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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

1111-1 ItI' I illE RE PORT ORIGINALLY ISSUED

July 195 as Advance Confidential Report L5F30a

THE DFVELOPNM AND APPLICATION OF

HIGH—CRITICAL—SPEED NOSE INLETS

By Donald D. Baals, Norman F. Smith, and John B. Wright

Langley Memorial Aeronautical Laboratory Langley Field Va.

CAcopiYiLl

NACA WASHINGTON

FILE COPY To be returned to

the rues of the Naflonal Advisory Committee

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NACA WARTIME REPORTS are reprints of papers originally Issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were pre-viously held under a security status but are now unclassified. Some of these reports were not tech-nically edited. All have been reproduced without change In order to expedite general distribution.

L - 729

NA.CA ACR. No. L5FOa

NATIONAL ADVISORY CpMMr.TE FOR AERONAUTICS

ADVANCE CCI . D . L REPORT

THE DEVELOP1ENT AD APPLICATION OF

- . .... . .. HII -CRITICALSPED NOSE INLETS

By Donald D. Baals, Norman F4 Smith,. aid John B. Wright .

NMA"Y.

. analysis of the nbse-inleL shapes developed in previous investigations to represent the optirrniin from the st.andpo.nt of critical speed has shown thatmarked. simi-

' larity exists between the nondimensional profiles of inlets which have widely different proportions and critical speeds. With the •nondi:cnensiona.l similarity of such profiles established, the iare differences in the critical speeds of these nose inlets must be a function of their proportions.

An investigation was ande"ta±teri in the Langley e-foot high-speed tunnel to establish the effects of nose-Inlet proportions on critical ach number and to developa ational method for the des :Len of high-critical-peed

.nose Inlets to meet de r . d re quirements. The n.ondimen- slonal ordinates of the 13 nose inlet, which were developed in a previcus investigation to be optimum from

• the standpoint of criIca1 speed, were extended and modi-fied slightly to improve the fairing These ordinates, now designated the NACA 1-series, were then a pplied to a group hf nose Inlets involving a systematic variation of proportions. Wind-tunnel tests of these nose inlets were made through wide ranges of inlet-velocity ratIo and angle of attack at Mach..nurjibers of . 0.3 and Q•• . Tests of representative nose inlets were carried to high speed (a•n1axinum Mach niberofQ.7). Pressure distributions and. critical Mach . number .characterjtics are piesented. fbr each of the nos..in1etststed. The results of these tests show that the length rat o of 'Length to maximurtidiameter) of- the nos-inletis the primary.f act or governing the maximum crit.cai .pee•d..-The effect of inlet .-diameter ratio (ratio of inlet diameter to maximum diameter) on critical speed is, in general, secondary;

Pt

NACA ACR No. L5F30a

but this ratio has an important function in governing the extent of the .in1et-v1ocity-ratio range for maximum critical speed. The highest critical Mach number attained for any of the-nose Inlets tested was 0.89.

The data have been arranged in the form of design charts from which MACA 1-series nose--inlet proportions can be selected for given values of critical Mach number and air-flow quantity. Examples of nose-inlet selections are presented for a typical jet-propulsion installation (critical Mach number of 0.83) and for two conventional radial-engine installations (critical Mach number of 0.765

The selection, charts and NACA1-series ordinates are shown to he applicable to the design of cowlings with spinners and to the design of high-critical-speed fuse-laze scoops. The possibility of a pplication of the - MACA 1-series ordinates to the experimental development of wing inlets is also indicated.

IN70DUCT ;ro-

Markd Increases in airplane speeds have-creted a demand for design data on high-critical-speed air inlets suitable for use with jet- . propulsion units, gas-turbine propeller units, and conventional engine installations. Previous development programs on air inlets have produced the NACA C cowling having a critical Mach number of 0.63 (reference 1) and the B nose inlet having a critical Mach number of O. BL (reference 2). These inlets have widely different proportions; the first is short with a large-diameter air inlet; the second, is of considerably greater length with a small-diameter air itilet, Each nose inlet was developed to represent the optimum design from th standpoint of critical speed for the particular propor-tions involved, - -

- Little information has been available on air inlets having proportions in the range between these two specific shapes. The research program reported herein way under-taken at the Langley-8-foot hi ..h--speed tunnel to establish the effects of variations of nose-inlet proportions on the critical Madh number and to develop a rational method for the design of nose inlets intermediate to the NACA C cowling and Pi nose Inlets, both in poportions

NACA ACR No. L5F30a 3

and in design critical Mach numbers. Such data have direct application to the design of high-critical-speed nose inlets and to the development of scoop-type air inlets.

SYMBOLS

a speed of sound, feet per second

V velocity, feet per second

M iTach number (V/a)

v170 Inlet-velocity ratio

a model angle of attack, measurd from model center line, degrees

P density, slugs per CUbIC foot

ratio of specific heats (for air, l.tO)

p static pressure, pounds per square foot /p - po\

P pressure coefficient\ q0

cr critical pressure coefficient, corresponding to local Mach number of 1.0

m mass. flow, slugs per second (pAy)

A area, square feet

rn mass-flow coefficient pV -

- q darnic pressure, pounds per square foot (IPV 2)

AH total-pressure loss between free stream and measurement station, pounds per square foot

o total conical-diffuser angle, degrees

D maximum diameter of nose inlet

d inlet diameter

NACA ACR' No.. L5F30a -

d/D inlet-diameter ratio

x distance from entrance, measured, along nose-inlet center' line

X nose-inlet length, measured from inlet to maximum-diameter station

x/D length ratio

F maximum frontal area of n6se inlet, corresponding to D, square feet

y ordinate measured perpendicular to reference line

Y maximum ordinate, measured perpendicular to reference line at maximum-diameter station (See table I.)

r nose-inlet lip radius

K arbitrary factor (See p. 35 and fig. 7.)

Subscripts:

min minimum -

cr critical

o free stream

1 nose-inlet .entrance -

DESIGN ANALYSIS

Derivation of Basic -Nose Ordinates

The A, B, and C nose-inlets presented in reference ' 2 were derived experimentally In asystematic series of Wind-

tunnel tests toapproach the optimum from the standpoint of critical speed. A comparison from reference 2 of the nondimensional profiles for these nose inlets having different proportions (fig, 1) indicàts a similarity of profile for all three inlets. Marked similarity of pro-, file is noted for the B and C-nose inlets; the A nose

NACA ACR No. L5FOa

inlet, however, varies somewhat from the basic profile of the3 and C nose inlets. This variation is believed to be due to the limitations encountered in the tests of reference 2, which involved the fairin g of this nose. inlet of large diameter into the basic streamline body at a given point and with a given slope. These limita-tions were not serious for, the B and C nose inlets, which have small inlet diameters, and correspondingly greater lengths were available for fairing than for the A nose inlet. 'A flat pressure distribution similar to ihe dis-tributions obtained for the B and C nose inlets was not obtained for the Anose inlet,'f.or which a pressure peak occurred at all inlet—velocity ratios.

Although the difference between the nondimens icnal B and C nose-inlet ordinates is small, the ordinates of the B nose i nlet have been selected for general use because the original proportions were considered to correspond more nearly to current design arplications than those of the C nose inlet. The nondi.ensional B nose-inlet ordinates have been atpliod to the layout of various nose inlets that differ appreciably from the original nose-inlet proportions in length, inlet diameter, and maximum diameter. In. refersnce.3, in which the variation from the original B nose-inlet proportions was considerable, the pressure distribution over the resulting nose inlets exhibited the characteristic flat contour with low values of the pressure eak. It WaS thus indicated that the basic B nose-inlet profile and the method of nose design could be applied to the design of nose inlets having proportions gretly different from those of te original nose-inlet shape tested.

iffictilty' was experienced, however, in the application of the original B nose-inlet ordinates, The slope of the nose-inlet profile at the station at which the nose faired into the streamline body was a finite value that varied with the nose-inlet proportions assumed. It was evident that the nondimensional profile should be extended to a point at which the slope was zero (maximum-diameter station). In order to attain this extension, the B nose- inlet ordinates were considered to include the NACA ill streamline body (to which the original nose inlet was faired) as far back as the maximum-diameter station. The r'esulting ordinate' s were developed in 'a nondimensional form and are piotted in figure 2.

6 NACA?ACR No. L5F30a

The fairnessof the extended B nose-inlet ordinates could not he determined from the measured pressure distri-bution presented in reference 1 because the wing-support interference affected the pressure distribution over the rear part of the nose inlet. Plots of the slope and the rate of change of slopeof the extended B nose-inlet ordinates Indicated a slight amount of unfairness in the region where the original nose inlet joined the stream-

line body. On the assumption that the curves of slope nd rate of change of: slope should be fair (these two curves together specify the local radius of curvature), the two curves were faired and the resulting ordinates determined. The faired ordinats,hereinafter designated the NACA 1-series ordinates ., are given in table I and are plotted in 'figure 2 in comparison with the extended B nose-inlet ordinates. The two curves are practically identical over the critical forward section and have only minor differences - over the rear section. The resultant NACA 1-series ordinates are, f;herefore, essentially the original NACA B-nose-inlet ordinates with the addition of a faired extension back to the maximum--diameter. station.

• The NACA C cowling ordinates are presented in reference 1. These cowling ordinates, derived , from a system-atic series of wind-tunnel test, were developed to attain the maximum critical speed for conventional- cowling proportions. The cowling pressure distribution appr-oaches the flat shape' that is optimum from the standpoint of critical speed. A comparison of the ACAC cowling pro-file with the NACA 1-series ordinates on a.nondimenaional basis (fig. 3) shows reasonable- agreenerit. Figure 3 also shows the nondimensional 'profile of an NACA wing-inlet-shape that is discussed in the section entitled "Wing Inlets."

In figiñe 3 the NACA C cowling -( = 0.70, = 0.31)

and the original B nose Inlet- -(

038, = 1.85) are sketched to scale. The great difference in the proportions of these two nose inlets, which a pproach the optimum from the standpoint of critical speed, is-evident. The critical 1ach numbers of the NACA C cowling and B nose inlet are, from references 1 and 2, 0.63 and 0.8L, respec-tively. With the nondimensiorLal similarity of the profiles of these two nose inlets established (fig. '3), the large variation in critical speed im.ist be a function of the


nose-inlet proportions. It is indicated, therefore, that nose inlets having proportions intermediate to these two nose inlets and having critical-speed characteristics approaching the optimum can be derived from essentially the same nondimensional profile. With the NACA 1-series ordinates as a basic profile, a systematic series of wind-tunnel tests was uhdetaken to determine the effects of nose-inlet proportions on critical speed.

Nose-Inlet Designation

A designation system for nose inlets has been devised that' indorporates the foilowin basic proportions (see sketch in table I)

d inlet diameter

D maximum outside diameter of nose inlet

X length of nose inlet measured from inlet to maximum-diameter station

The number designation is written in the form 1-40-150. The first number in the designation represents the series; the number 1 has been assigned to the present series. The second group of numbers speôifies the 'inlet diameter in percent of maximum diameter d/D; the third group of numbers specifies the nose-inlet length in percent of maximum diameter x/D. The NACA 1-10-150 nose inlet,

therefore, has a 1-series basicprofile with = 01.I0 and = 1,50.

D

APPARATUS AND TESTS

Models

The nose inlets of the NACA i-series investigated are illustrated in table II. These nose inlets represent a systematic variation of inlet-diameter ratio d/D from 0.40 to 0.70 and of length ratio x/D from 0.30 to 2.00. All nose-inlet models were of 12-inch maximum diameter and were constructed of wood. With the exception

NACA ACHNo. L5F30a

of the nose'inlets of = 2.00,,for which the length

was 21 inches, the length. of :the. detachable nose inlets was maintained at 18 inches. This length corresponds to

a value of x/D of 1.5. To n6se inlets having < 1.5,

cylindrical sections (skirts) were added to maintain the over-all length at 18 1nches. Several of the nose inlets were provided with detachable skirts in order to investi-gate the effects of varying the fineness ratio of the test body . Scale drawings .of each of the nose inlets tested are presented In figure h., grouped according to inlet-diameter ratio. Photographs of certain of the nose inlets (with skirts), which illustrate variations in length ratio and inlet-diameter ratio, are presented in figure 5. The duct — li p radius for all nose Inlets tested was maintained at 0.025Y (table I), which is approximately the same value as In the develo pment tests of references 1 and 2. Several minor modifications to the lip radius and internal fairing were tested. (See fig. 6.) No attempt was made to simulate an aircraft internal-flow, system insofar as internal resistance and duct lines are con-cerned. The model ducts for the nose inlets were conical ba1c to the parting line of the removable nose section, where all ducts had a common diameter of 7.2 inches.

In addition to the nose inlets listed in table II, the NACA C cowling was tested. Three nose inlets

having 0.60 and 2 L = 1.50 and having profiles

representing, deviations from the NACA 1-series profile were also-tested to show the effects of such deviations. All three nose inlets, which are drawn to scale in figure 7, differ from the NACA 1-series profile in--that the thickness-of the forward part is greater than for the NACA 1-series profile.

Each nose inlet was provided with a row of surface static-pressure orifices, which extended along the top

center line from the inlet lip to a point inches to

the rear of the detachable nose. The pressure tubing passed from the model through the tunnel test section along the support strut and was connected to a photo-graphically recorded multiple-tube manometer in the test chamber.

NACA ACR No. L5F3 Oa 9

The nose inlets were mOunted on a cylindrical after-body that was supported at the tunnel center line by a single vertical streamline strut. This strut was attached to the body at a station 2 strut chords behind the removable nose Inlet in order to minimize interference effects. A drawing of the model installation is shown in fiure8. The internal-flow sjstem is also shown in fIgure 8. The duct section immediately behind the parting line of the nose inlet and body was contracted to the rake station; where a rake of total-pressure and static-pressure tubes was located for the determination of internal losses and air-flow quantity. The duct exit was located at the tail of the body and was provided with a plug-type control for 'varying the exit area. An electric- motor drive for the exit control was included in order'

• that the air-flow quantity could be varied through a range during each test. A flapped exit was used for several tests to obtain high values of inlet-velocity ratio. The angle of attack of the model was varied through fixed increments by means of an internal indexing device.

Equipment and Tests

The Langley 8-foot high-'speed. tunnel, In which this investigation was conducted, is a closed-throat, circular-section, single-return tunnel. The turbulence of the' air stream is lov but is somewhat higher than the turbulence of free air.

The complete range of NACA 1-series, nose inlets shovrn In table TI was tested at 0.30 and 0.40 through an angle-of-attack range from approximately 00 to 80 by 2 0 increments. Several of the nose Inlets were tested through the Mach number range up to approxi-mately M0 = 0.7. The inlet-velocity ratio was varied from about 0.2 to values higher than 1.0 for the nose Inlets having small values of d/D. For the nose inlets having large values of d/D, the maximum value of inlet-velocity ratio was limited by thecapacity of the internal-flow system.

10 NACA ACR No L5F30a

RESULTS AND DISCUSSION

Basic Nose-Inlet Characteristics

• Basic data.- The basic nose-inlet characteristics are presented as, plots of pressure distribution and critical Mach number for each of the nose inlets. These data are grouped according to inlet-diameter ratio. Figures 9 and 10 present the pressure distributions over

the nose inlets, having 0.IL0, the MACA l-1..0-200

and 1440-1-,0 nose inlets, through ranges of inlet-velocity ratio and model angle of attack. These two parameters goyern the pressure distribution for.a given nose inlet. At zero angle of attack the rressure distri-butions for the moderate-to-high values of inlet-velocity ratio are essentially flat with very low values of peak negative pressure coefficient. As the inlet-velocity ratio is progressively decreased, a pressure peak appears near the lip of the nose inlet because of the high local angle of attack of the lip. The magnitude of the pres-sure peak increases rapidly-as the Inlet-velocity ratio is further decreased. Progressively higher , values of the inlet-velocity ratio are required to eliminate. the pres-sure peak as the model angle of attack is increased. At higher values of inlet-velocity ratio a favorable pressure distribution can be obtained through greater ranges of angle of attack.

The critical-speed char acteris Lies for the NAOA 1410-200 and 1-40-150 nose inlets are presented in figmes .11 and 12. The critical Mach numbers were deter-mined from the measured pressure distributions by means of the von. .Karmn relation (reference )4). For a given angle of attack, little change occurs in the value of the critical Mach number for values of inlet-velocity ratio in the medium-to-high range. The sharp downward break in the critical Mach number curve occurs at a value of Inlet-veloQity ratio below which the critical Mach number is'deterinlne,d by a pressure peak near the lip. Further decrease in inlet-velocity ratio produces a rapid decrease in critical Mach number.

An important effect of an increase in angle of attack (figs. 11 and 12) is to shift the knee of the critical Mach number curve to progressively higher values


of inlet-velocity ratio. 7A compar .iso 'n of the critical-speed characteristics for. two . an-l-es of attack shows only small 'differences between the values of the critical speed above the knees of the, .two,eurves; below the knees of the curves ,, however, marked differences are noted.

Figures 13 to 38 present pressure distributions and critical Mach number characteristics for the nose inlets having inlet-diameter ratios of 0.50, 0.bO, and 0.70. In general, the. effects of changes in inlet-velocity ratio and angle of attack are .similar to those described for the NACA 1-40-200 and 1-I0-150 nose 'inlet.

The effects of inlet rroortibns.- The critical Mach number curves for the series of nose inlets tested have been grouped for constant angles of attack, according to inlet-diameter ratio and length ratio, to illustrate the effects of these parameter's on the critical Yach number characteristics. Figure 39 shows the effects of length ratio on critical Mach number., For a given inlet-diameter ratio, an increase in maximum critical Mach number is shown to occur with increases in length ratio. An increase in. length ratio, however, causes the knee. of the critical Mach number curve to occur at progressively higher values of inlct_velocit r ratio and thereby reduces the inlet-velocity-ratio range for maximum critical speed. A wider range for maximum critical speed is therefore obtained for the lower values, of length ratio but with an im portant sacrifice in the value of maximum critical Mach number. -

Figure ) ,O shows the- effect of inlet-diameter ratio on critical Mach number cheracteristics. A decrease in the value of inlet-diameter ratio for a given leigth ratio shifts the knee of critical Mach number curve to lower values of the inletvalocit r ratio and thereby increases the exten of the Inlet-ve.ocity-ratio range for aximurn ci' L' ice s-,caed. Thc cf ct of nle-z a icter ratio on maximum critical speed is small at largevalues of leneth ratio, For exti'ei-elv low values of length ratio, a significant decrease ifl maximum critical. Mach number occurs with decrease in the of inlet-diameter ratio. These data thus indicate that the length ratio is the more impor ;ant of the se t.o para;'uEter S J r governing the maximum crtcal speed; the n1e1;-o1ameter ratio is, in general, secondary. For a given length ratio, however, the inlet-diameter ratio fOveri'IS. the position of tiie knee of the critical Mach number curve,

12 NACA ACH No. L5F30a

In figure 39 envel.qpe curve, have been drawn tangent to theknoes of the critical Mach number curves. A summary plot of the envelope curves alone Is presented in figure Li for a = 00 , 2°, and 14°. for each of the d/D groups. Inasmuch as the knee of the critical Mach number curve corresponds to the point or conditions at which the nose-inlet pressure distribution is approxi-mately flat, the envelope curve has. important signifi-cance in that any point on the curve iepresents the optimum value of critical Macb, number that can he obtained for specified values of inlet-diameter ratio and inlet-velocity ratio. Comparison of the envelopes for the three angles of attack (fig. 141) shows that important decreases in critical Mach number occur in operation at angles of attack other than 00.

It is apparent from figure 79 that only one value of length ratio x/D will give the optimum critical speed at a particular value of inlet-diameter ratio and inlet-velocity ratio. This point on the envelope curve corresl)onds to the knee in the critical Mach number curve; therefore, this point represents the minimum.value of inlet-velocity ratio at which the particular nose Inlet will possess an essentially flat nressurè distribution and a critical Mach number approaching its maximum.

In flight the level high-speed condition will usually govern the inlet design, for not only will the flight Mach number be a maximum but also the inlet-velocity ratio will usually be a minimum. The design of a nose Inlet to satisfy given critical Mach number requirements must therefore be based on the minimum inlet-velocity ratio.

Selection Charts

Basis and composition.- The envelope curves for the NACA 1-series nose inlets tested (figs. 39 and 141) have been arranged in the form of selection charts in figure 142, from which nose-inlet proportions can be determined for a specified critical Mach number and corresponding minimum air-flOw quantity. The iii let - velocity ratio, which cannot be fixed for a given air quantity until the entrance diameter is known, has been replaced by the mass-flow

coefficient m , which is an independent design p FV0

NACA ACR No. L5F30a

1z

quantity. Figure 43 is a'p2ot of inlet-velocity ratio against mass-flow coefficient for various values of dID and M0 . The curves for Mach numbers less than 0.50 have

been omitted. The curves for incothpressihle flow (M 0 = 0) can he added to this figure as straight lines between the origin and the points, at which the curves converge

V1 at " = l.0. The Inlet-velocity ratios for the envelope

Vo curves from figure )v]. have been converted to mass-flow coefficients at the corresponding value of Mcr by means of figure L.

The solid lines in the lower half' of the selection chart (fig. 42) are the envelope curves from figure ti. The interjacent dashed curves re present the envelopes for intermediate values of diD and were Obtained from cross plots of the experimental data. The envelope curves have been extended beyond the limits of the data by only a small amount. Some additional extrapolation ma be judiciously performed on the selectioi chart, if necessary, through reference to figure 39. The dashed curves intersecting the main curves on the selection chart are lines of constant inlet-velocity ratio for

correspondin values of m , d/D, p0FV0

chart. The solid curves on the upper tion chart are plots of the value of an T'IACA i-series nose inlet havin th Mach number for a particular value of ratio and mass-flow coefficient.

and Mer on this

half of the selec-x/D required for

E maximum critical inlet-diameter

Use of charts. - The selection charts have two prin-coala'D)11cations: (1) selection of nose-inlet propor-tions, for use with the YACA 1-series ordinates, that will attain a specified design critical Mach number and satisfy specified air requirements; (2) determination of critical Machnumber and minimum-flow conditions for an MACA 1-series nose inlet of given broportions. , In general, these •bwo applications pertain to the high-speed and cruise conditions, respectively. The selection of proportions of a nose inlet will usually be governed by the high-speed condition. It will then be desirable to check the selected pro portions for other flight conditions, such 'as the cruise condition, for which the design angle of attack, mass-flow coefficient, and flight Mach number

NACAAOR No. L5F3Oa

Will be sbmewhat different. The high-angle-of-attack (low-speed) flight conditions are also of interest from considerations of external and internal separation. (These items are discussed in the section entitled "Detail Considerations..")

The design data specifying the selection parameters are the design speed and altitude, the corresponding air requirement, and the fontal area of the body to which the nose inlet is being a pplied. The use of the charts is Illustrated by means of an example. The following desin conditions and quantities will be assumed for a typical jet-propulsion installation:

Circular-fuselage cross-sectional area, F, sq ft . 20 0pera1.ing altitude, ft .............. 35,000 Density at altitude, p0, slug/cu ft . . . . 0.000736

/..1.gn-speed Cruise condition condition

Free-stream velocity, V ft/sec •(550ph) 11) Free-stream Mach number, M0 . . . 0.83 o.6 Angle of attack, a, deg ...... 0 . 2 Air required, lb/sec . . . . . . . 50 Mass•-flow coefficient, m/p 0FV0 . 0 . 13 0 013

The proportions for the nose inlet to meet the high-speed conditions are found by entering the selection chart for a = 00 (P i g. 42(a)) at the bottom with the

value of mass-flow coefficient(^O_

m = o.13b and.

FV)m i n

proceeding vertically upward to the value of Mcr = 0.83. At th'is'-point the value of inlet-diameter ratio d/D can be read, along with the value of inlet-velocity ratio V1/V0 Corresponding to the values of d/D,

, and M for this point. By continuing cr\

vertically to the top section of the chart, the required value of length ratio x/D can be read for the' value of d/D obtained previously. The proportions for the


nose inlet that will give a critical Mach number equal to the high-speed-flight Mach number are

= 0.5261Selection I

=1.16 5 The corresponding value of - j = 0. 5 may hç read

1 from the selection chart.

mn

The nose inletselectQc for the high-sreed condition (selection I) should now be checked to determine whether it willsatisfy the secified cruise requirements. This check can be made by entering the tor, half of the selec-

tion chart for a = 2 0 (fig.2(b)) with X = 1.16, pro-

ceeding across to the value = 0526, and then moving

vertically downward to the same value of d/D on the lower half of the chart.. At this point the value

of ( and the corresoonding value of M can ^pOFVO) cr

mm be read. By this procedure the following results for the cruise condition are obtained

Mcr = 0.815

( m =. 0-159

oF1V )m

(2:.) = o.14i4 \ mm

In figure 144(a) a scale drawing of this MACA 1-series nose in1t (selection I) is presented for illustration along with the critical Mach nuirber curves estimated from figure 39 for a. 00 and a =2 0 (the high-speed and cruise conditions, respectively). Also noted on this figure are points representi ng the two s pecified de sign requirements. The design high-speed requirement falls

16 NACA ACR No. L5F30a.

on the knee of the curve for a = 0 0 because the selec-tion charts are based on the knee. The fact that the desi gn cruise requirement falls below the estimated critical iach number curve for a 2 0 indicates that the critical speed for the nose Inlet selected exceeds the cruise requi'ement. The cruise requirement point, however, represents a value of ma-flow coefficient below the minimum value indicated by the knee of the curve. Operation of the selected nose inlet at the cruise condition will therefore produce at the lip of the inlet 'a pressure peak, which may be undesirable from the standpoint of drag.

It is evident that some marin ray be desirable between the design operating reqiirenents and the nose-inlet selection conditions. An .n.ipection of figure i!J4(a) indicates that a margin of m/p 0FV0 of the order of 0.02

may be desirable to eliminate the pressere peak in the cruise condition. The d.esie;n selection parameters for the high-speed condition then become

f.m '%\POFVQ

m in

= 0.150 - 0.02

= 0.110

M pr ar .1

From the selection chart for the high-speed condition (fig. L.2(a)), by the method outlined for selection I, the following results are obtained

= 0.50

-. - l.-0 D

/ V1 I ' - C t I - \ V —O/min

1'• Selection II

j

- NACA ACR No. L5F30a 17

- For the cruise condition for these values of x/D and d/D, from figure t2(h),

Mcr 0.819

rn= 0.138

to FV) \O mm

(ii) in

The estimated critical Mach munher curves and the points corresponding to the design requirements are shown with a scale drawing of this nose inlet in figure )4(b). For the cruise condition, the requIred value of the mass-flow coefficient is higher than the minimum value represented by the knee of the curve. Introdurtion of this margin

in - involves a decrease in the value of the inlet- p0FV0

diameter ratio and a corresr,ondinc increase in inlet-velocity ratio but only a small change in the value of the length ratio.

In the desi gn of sone instalJations a margin between the design high-speed Jaoh number and the critical Mach number of the nose inlet may be desirable in additiOn to the margin in mass-flow coefficient illustrated by selec-tion II. With a margin of 0.02 assumed for Mcr and with the same margin in mass-flow coefficient assumed a for selection IT, the dc-sign selection parameters become

/m \ I

0. 110 p0FV0)

'miii

Mier 0.83 + 0.02

= 0.85

From the selection chart for thehigh-speed condition (fig. LL2(a)), the following results are obtained.-

18 NACA ACR No. L5F3Oa

d

:L .45 Selection III

0.37 \'°/rnln

For the cruise condition (fig. .2(b)), for these values of x/D and •d/D,

cr 0.834-

=0.128 rI mm

\V OJj

The estimated critical Mach riuniber curves and the points corresponding to the design requirements are shown with a sc1e drawing of this nose inlet. in figure L!J4( c ). For both the cruise and the high-speed conditions a margin now exists between the design values and the required

\ operating values of Mor and . Introduction

0F J - \o. • 0

of these margins results in a nose inle,t havin a smaller inlet-diameter ratio and a greater length ratio than those of the nose inlet selected for the orir.:inal design. con-ditions (selection I). The decreased inlet-diameter ratio involves a corresponding increase in inlet-velocity ratio, which may he detrimental from the standpoint of internal losses. In order to determine the amount of design margin that maybe used, therefore, the character-istics of the internal-flow s ystem must he considered.

Several important qualifications should be noted concerning the a pplication of the selection charts. The selection charts for the NACA 1 ,-series nose inlets are based on the knee of the critical Mach number curve for a given nose inlet. The application of these charts to the design of a nose inlet for a given critical Mach.

NACA .ACR No. L5F3Oa 19

number will. therefore-result in a nose inlet having the ñiinimum value of x/D and the maximum value of d/D that can he used. - The proportions given by the selection charts represent limit ing.1ia1ues rather:th'an optimurri values; consequently, in. installations for ,which -values of length and. diameter ratios are n6t.restridted l the proportions cn oe varied from the limiting values in the .dire c .t ions indicated in the . éxamplê.p±'Oiio1sl presented.

• For anNACA i-series nose inlet having arbitrary proportions, the cit'ica1 Mach number characteristics at a 00 and -20 may he checked against-the operating. requirements by means of the selection , charts in a manner srnilar to that emp1oyed in.c-hecicing the cruise condition for selection I of the example. For conditions to which, the selection charts do not apply, reference can he made to . figures 39 and LC and to the figur e s presenting critical Mach number data for the nose inlets tested for estmaticn of the characteristics of the particular nose inlet involved.

- Certain combinations of , noee-inlet proportions within the range of the series tested cannot he checked for critical speed and operating conditions-by neans.of the. selection chart of figure 2; for 'example ., the NACA 1-50-050 nose inlet, which was tested in thepresent investigation, cannot be found by entering.the upper part of the selection chart with its, prorortions. Figure 16 shows that the characteristic flat pressure distribution is not obtained with this nose inlet at any value of inlet-velocity ratio. Examination of the curves for the

nose inlets of = 0.50 (fig. 39) shows that the critical-speed curve for this nose inlet, falls far below, the envelope curve even if the envelope and critical-

V1 speed curves, are extrapolated. to = 0. For an inlet-

0 diameter ratio Of 0.50,'theref6re, this nose inlet has a consideably shorter length than that required to obtain the' critical speed indicated by the envelope curve even vi

V0 at -' 0." This nose inlet therefore des not appear on

the selection charts because, as \the . chart shows, larger values . of length ratio should be Used for this value of, inlet-diameter ratio. •. .

NACA ACR No. L5F30a

Design Application

The NACA 1eries ordinates.- The selection charts presented are based on hose inlets designd from the NACA 1-series ordinates.., These ordinates have been shown in the setio!ièntit1ed "Design .Analyis tt to approach closely the optimum from the standpoint of critical speed for a wide range of nose-inlet proportiobs:. Any departure from the nondimensionl NACA 1-series ordinates (table I) may appreciably lower the value of the maximum critical Mach numbe and alter the shape of the critical Mach humber cuiwe. The results of tests of several nose inlets having profiles that differ from the NACA 1-series ordinates are presehted in the setin entitled "Effects of variations in basic profile.'

The small degree of.waviness.eviden- in some of the presue distributions for several of the nose inlets is believed to be due to very small deviations in profile. Because the models were constructed of wood and were of relatively small size (12 in. in diameter), exact dimen sional control of the profile was difficu-it. It is belieVed, however, that, inasmuch as these deviations 'are small, the effects on maximum critical Mach number and the shape of the critical Mach numbercurve will likewise be snal1. Nose inlets based on the MACA 1-series ordi-nates should therefore Closely a pproach the optimum from the standpoint of crtica1 .seed for the particular pro-portions selected.

It should he noted that the selection of an NACA 1-series nose inlet of proportion .s that exactly satisfy given conditions results in a pressure distri-bution approaching a flat shape. Although optimum from the, standpoint of critical speed, such a pressure 'distribution is not the most desirable from the stand-point of attaining laminar flow. The pressure distri-butions at-inlet-velocity ratios above the design value, however, tend to ap proach the type*yp of distribution char-acteristic of those permitting laminar flow. The intro-

duction of margin in the design value of , as

shown in the example, will therefore tend to provide a more favorable pressure distribution from the standpoint of attaining laminar flow.

20

MACA ACRNo. L5F30a 21

Cowlings.- In order to compare the critical-speed characteristics of the MACA lseries nose inlets with the MACA C cowling of reference 1, a model of the MACA C cowling was tested on the model shown in figure 8. The pressure distributions and critical Mach nwnber char-acteristics are presented in figures L5 and L6, respec- t

'ively. The value of critical speed obtained for this

cowling agrees closely with the value determined in the tests of reference 1. The proportions of this cowling

are = 0.70 and = 0.31; therefore, thi cowling is

closely comparable in proportions ' to the MACA 1-70-030 nose inlet. The critical-speed characteristics of this nose inlet and the NAG.AC cowling are compared in figure .47 The critical Mach number of the MACA C cowling is shown to be between 0.005 and 0.01 hic,her than that for the MACA 1-70-030 nose inlet. Ajproxi 3-ate1y one-half this difference can be shown (by cross plots of the expêri-mental data) to be due to the slightly 'reater length

ratio-of the NACA C cowling ( = 0.31); the remainder

must he ascribed to the slight difference between the -basic nondimerisional ordinates for the MACA C cowling and the MACA 1-series ordinates. (See fig. 3.) . The

- fact that the remaining difference is small indicates that the MACA C cowling ordinates and 1-series ordinates will yield nose inlets of approximat1y equal critical speed. An inspect-ion' of the pressure distributions, how-ever, indicates that for nose inlets of proportions similar to those of short cowlings, an increase in thickness near the lip, such as is provided by' the MACA C cowling ordinates, may be beneficial.

The critical?\Mach number curves for the MACA 1-70-050 and 1-60-05o nose inlets have been added to figure 47 to show the effects of small variations in proportions for short-cowling-type nose inlets and • iLlustrate the - chanc.esi p proortions that must he made.-In-order to obtain cowlings having critical Mach numbers above that of the MACA C cowling. These data show that the simül- taneous increase in the length ratio and decrease in-inlet-diameter ratio by apprbpriate increments Will yield cowlings of higher critical speed than the MACA C cowling for comparable -inlet-velocity-ratio and angle-of-attack ranges. Selection of nose-inlet proportions in this range may be made by means of the selection charts pre-viously presented (fig. 42).

WA

NACA ACR No. L5F30a

Effect of propeller spinners..- The effect of a pro-peller spinner on the crItical Mach number of a cowling and on the internal flow must be considered in the design of a cowling for a' tractor propeller installation. Several cowling shapes have been developed by the NACA for use with large spinners (references 5 and 6). The data from tests of these cowling -) s have been analyzed in relation to data in the present report.

Shown in figure 48 are the NACA DL cowling (cowl 2 of reference 5) and the NACA D5. cowling (the D 5 cowling of reference 6), which were developed for use with the spinners shown. For comparison of profiles', NACA 1-series -cowlings of. similar proportions have been-superimposed. The profiles of both the D 1 and D cowlings fail

somewhat under the NACA 1-series profile near the lip, but good agreement with the NACA . 1-series profiles Is ..evident. Inasmuch as the -profiles are generally comparable, the characteristics of bhé cowlings developed for use with spinners may be compared with the character-istics of the NACA 1-series open-nose cowlings to estab-lish qualitatively the effects of the propeller spinners.

Pressure distributions over . the NACA DL and D3 cowlings from data in references 5 and 6 are presented in figure 49. The pressure distributions for both cowlirigs 'do not possess the flat contour that Is chaxac- 't'eristic Of the pressure distributions for the NACA 1-series nose Inlets. Inasniuchas no high pressure peaks exist, hpwever,, • smali modifications to the cowling contours would probably suffice to obtain essentially flat pressure distributions.

The critical Mach numbers of the NACA D 1 and DS cowlings at a = 0 0 are shown in figure 50 for several values of Inlet-velocity ratio. Also shown in this figure are the estimated critical Mach number curves for the corresponding NACA lseries cowlings (without spinners) taken from figure' )2 for the proportions shown in figure 48. The maximum. critical Mach numbers of the NACA D5 and DL cowlins are in good agreement wit1- those of the corresponding NACA l-eries,open-nose cowlings.- The effect of a' spinner on the maximum critical speed of a cowling is evidently small.

NACA' ACR " No.. L5F3 Oa'

23

Figure 50(b) shows also values of critical Mach number from unpublished tests, of a full-scale NACA DS cowling Installation with spinner in place and. With spinner removed. These data show that the cowling Without spinner is-opera't'ing at an inlet-velocity ratio well below the knee of the 'critical Mach number curve and consequently possesses a high pressure peak at the lip and a corresponding low critical-speed. The principal effect of the spinher 'in the case of theNACA' DL and D5 c.Owlibgs is therefore to raise the in.e'-velocity ratio for the design air-flow qith.ntity; this increase permits the, cowling to operate in the range of inlet-velocity ratio for maximum critical speed...' .

The effect of a spinner on the inlet-velocity ratio at which the knee of. the critical Mach number curve occurs is not accurately predictable from existing data. The data tend to indicate, however; that'the knee 'will occur at a value of inlet-velocity ratio equal to or slightly less than the Value for the open-nose 'condition. The addition of a spinner to a cowling thus permits (but does not. necessarily require) an increase in d/D as a": consequence of the increased inlet-velocity ratio. This fact may be of advantage'in selecting a high-critical-speed cowling of minimum frontal area (discussed In section entitled "Sample cowling designs").

In the design of a cowling with a spinner, considera-tion must be given to the fact that a minimum value of inlet-velocity ratio 'exists, below which unstable flow at the cowling entrance occurs. Values of the minimum inlet-velocity ratio for stable entrance flow and high' cooling-pressure recovery have been determined from tests 'of specific installations. The data of references 6 and 7 indicate a value of minimum inlet-velocity ratio of the order of 0.4 for a cowling with spinner but no propeller; reference 6 and the results of unpublished flight tests indicate ,a value of the order' of 0.35 for a.cowling with spinner' and rotatIiig propeller. The use of' ui'tàble pro-peller cuffshas been found to improve entrance-flow stability at low values of inlet-velocity ratio and has been shown to permit satisfactory operation at' inlet-velocity ratios as 'low 'as 0.30. A general investigation, however, Is necessary',to provide definite values of minimum inlet-velocity ratio "for various "cowling-spinner configurations.

24 NACA ACR Now L030a

It will usually be desirable to design a cowling for the lowest value: 'of inlet-velocity ratio :oOnsisteñt with stabl,.e entrance flow because of the thèrêase in diffuser losses, that oecur with increase ii inlet-veipcity ratio. An-optimum value.of 5illet-velocity ratio or s pinner size therefore exists for a given cowlihg installation. This fact is illustrated in.referebes 7 and. 8, which preset the results of Investigations in which spinners of several sizes were tested in conjunction with NACA cowlings through limited rangesof air-low quantity. These references show that, from the standpoint of internal total-pressure recovery, an optimun spinner size exists for a given cowling. 'Ube of a spinner smaller or larger than the optimum was , Ehown to result in increased total-pressure losses.

In summary, the ioregoing , analysis indicates that no important changes in maximum critical speeds of cowlings selected from the deigii charts presented hOrein will occur when a propeller spinner-is added. In addi-tion, the availabledata tend to indicate that the knee of the critical Each number curve will occur at approxi-mately-the same value of inlet-velOcity ratio fora cowling with or withOut a spinner; further investigation is required, however, to etab1ish definitely the location of the knee of the curve. The inlet-diameter ratio d/D of a cowling may therefore be increased above the open-nose design value, if desired, in order to take advantage of the increase in inlet-velocity ratio produced by the' additiofl of the spinner. With a spinner, however, a. minimum value of inlet-velocity ratio exists for stable entrance conditions. The spinner, diameter should, there-fore be adjusted to keep thO operatiiigvalue of inlet-velocity ratio âlightlyabove.this minimum value. (The selection of a cowling-spinner combination is Illustrated in the sample cowling designs that follow.)

Sanp1e cowling designs.- The application of the NACA 1-series ordinates to high-critical-speed cowlings for two typical radial engines illustrated in the fol-lowing examples.. For these examples, the cowlings are designed to provide only cylinder cooling air. The fuse-lage diameter is assumed to be sufficiently large to assure internal clearance between engine and cowling. In order to obtain a specified value of 'clearance between engine and cowling, a trial-and-error procedure for determining the value of fuselage diameter is required.

NACA ACR No. L5F3 0a 25

The assumed design conditions and the proportions of the cowlings selected from figure 42 are presented in the following tablet

Maximum diameter of fuselage ox nacelle, D, ft . . 5.0 Operating altitude, ft . . . . . . . 35,000 Free-stream density at altitude, p0,

slug/cuft . . . . . . . . . 0.000736 Design maximum velocity, V 0 , ft/sec

(500 mph) . . . J. , . . . . . . ....... • 733 Desicn critical Mach number, Mcr,

corresponding to V0 above . . . . 0-76 Cowling angle of attack, dog . . . ........... 0

Two-row Four-row radial engine radial engine

Cylinder cooling mass 0

flow, m, slugs/sec . . . 0 .6)± 1.22

Mass-flow coefficient, m 0.06 0.115 t;lv t-,.o 0

From figure 42(a), for the above values of critical ach number and mass-flow

coêfficient

d/D . . . . . . . . . . . 0155 o61 X/-j) ........• • • • 3 75 0 • (v1/v0 \ .,....... 0.15 0.2L.

/min

The cowling profiles were computed from table I and are drawn to scale in figure 51 along with the corresponding engine installations. In the preceding section it was pointed out that the inlet-velocity ratio should not fall below approximately 0.3 when a spinner is used with a cu.ffedpropeller. With the asumption of .a cuffed pro-peller, the spinner sizes for th .e two cowlings have been selected to raise the inlet-velocity ratios to 0.3. The resulting spinner diameters are 23 inches and 16 inches for the cowlings shown in figures 51(a) and 51(b), respectively. .

26 1 NACA ACR No. L5F30a

These two examples show that cowlings-designed for critical Jach numbers above that of .the NACA C cowling are characterized by a smaller inlet-diameter ratio and a greater length ratio. The length-of the propeller shaft on these engines necessitates the location of the engine ahead of the

'maximum-diameter station of these

high-critical-speed cowlings. The maximum diameters of these cowlings are therefore greaterthan the minimum diameter that might otherwise .be used. The increases in frontal area above the minimum area (for the same internal clearance between engineand :cowling) for the cowlings in figures 51(a) and (b), are approximately 26 and 20 percent, respectively. Such an increase in frontal area may not be significantin the case of Installations for which the fuselage or nacelle iameter is governed by factors other than the engine diameter but will present an important increase in frontal area and drag in instal-lations for which the minimum fuselage or nacelle diameter is governed only by the engine diameter. This excess frontal area may be reduced by use of an extended pro-peller shaft or a hollow spinner such as that used in the NACA hi' -speed cowling (reference 9), which was derived from the B nose ordinates.

The cowling proportions given by the design charts (for use with the NACA 1-series ordinates) represent the minimum length ratio and the maximum inlet-diameter ratio for given requirements. The addition of the spinners, however, has increased the inlet-velocity ratios of the sample cowlings; thisincrease makes possible (but not mandatory) an increase in the inlet-diameter ratio. This change is of particular interest as an additional method of reducing the excess frontal area because, as the value of d/D is increased, the maximum diameter of the cowling can be decreased. Inasmuch as the inlet-velocity ratio for the cowling with spinner has teen raised above the value for the cowling without spinner,, a fictitious value of mass-flow coefficient higher than the design value can in effect he assumed and the cowling proportions can be determined from the selection charts on the basis of this value. The spinner frontal area must then be chosen to make the inlet-velocity ratio the desired value without actually increasing the mass-flow coefficient above the original design value.

• The proportions of an NACA 1-series cowling designed for operation with a spinner at an inlet-velocity ratio

NACA ACR No. L5F3Oa 9

of 0. vill now be selected for the four-row engine for which the requirements were previously presented. The selection may be made by entering the design chart (fic. L2(a)) at the left side with the value of 1cr = 0.76 and proceedin horizontally across the chart to the line

for = 0,30, At this point the. value of d/D can be If

read; then, by moving vertically u pward to the top section of the chart, the value ofx/D can he read at the value of d/D previously obtained. The results thus determined are

o.6t

=

(1

0

].)0.30

frn_\ = 0.159 kpFV)

• mm

The area occupied by the spinner must be sufficient to make the inlet-velocity ratio 3.0 at theôrizinal speci-fied value of mass-flow coefficient, 0.115. The spinner diameter is then 20 inches. The excess frontal area of this cowling over the minimum area that could be used (for the same engine clearance) is approximately 16 per-cent, sliitly loss than. the excess frontal area of the cowling sliowti in fi g c 1(h).

In some cases, further decreases in excess frontal area may he desired in others, asinñer larger than that given by the procedure outlined mp.y he required from ccnsideratiohs. of propeller hub size as, for e.xample, for cowlings designed for use with gas turhincs of' small diameter. In such caes the i?t-ve1ocit7 f?- ratio can be further increased in order to make possible further increase in inlet-diameter ratio and sDinner size. The increased.. inlet-velocity ratio will, however, tend to increase losses in the diffuser.

28 NACA ACR No. L5F30a

- It is to be emphasiZed that-the procedure presented for designing NACA 1-series cowlings for use with propeller spinners is based on the analysis of the results of limited investigations. Future general investigations of cowling-spinner combinations may therefore lead to some refinements of this procedure; in addition, some small modifications to the MACA 1-series ordinates may be'found necessary for use with spinners. In general, however ' , the procedure outlined Is believed to be satis-factory, particularly for thstallations including the use of a spinner of conservative. size.

Air scoops.- The a pplication of the MACA 1-series profile to air scoops has been denionst'rated in the tests of reference 10. In this investigation a large scoop was designed as a semicircular body of revolution and located near the 1onitudirial midposition on the lower surface of a fighter-type fuselage. Provision for removing the fuselage boundary layer wa's included. The critical Mach number curves for three radial planes of the scoop (taken from fig. 20(b) of reference 10) are shown in figure 52. The estimated critical Mach number curve for a nose inlet of . inlet-diameter ratio and length ratio equal to those of the scoop has been obtained by means of figures 39(a) and t.2(a) and added to figure 52 for comparison. Marked similarity between shapes of the estimated curve and the curves meesured for the bottom and .6o° planes of the scoop is noted. The knee& of the curves occur at aoproximately , the same value of inlet-. velocity ratio. The critical Mach number curves for the scoop are lower than the curves for the corresponding nose inlet throughout the inlet-velocity-ratio range because Of the effect of the flow field of the wing and fuselage on which the scoo p was located. It is thus indicated that The proportions for hid-i--.critica1-speed air scoops may be obtained from the selection chart (fig. ).2), with allowance for an estimated loss i in critical speed due to interference effects. Additional tests of such air scoops are needed to provide more detailed design information concerning the application of the YACA 1-series-profile to high-critical-speed air scoops.

Wina inlets.- An analysis presented in reference 11 shows that pressure distributions over two- and three-dimensional bodies of identical thickness distribution will generally have similar. shapes. Reference l shows,

NACkACR ' No.: 'L5F3Q5. 29

•',.foi exampi.' that in inômpresiblef1:o* wlth. môt ion paxa,llel,totie tha;jo a?c. s 'th.e'vcloci.yd'is:tI'ibut:1on about 'a',prolat.eplieroi.dJ.sp qual toa,.constant •t,ims,;

ie . velocity di ributi.qn .aout the'c err e.spondng•e 111p-tica".cy1inde.r.::Th'i,nsJantiS .. unctionof . only the thicmess: .ratto. Foil:shApe'$ other .thar' elli.p.'t:ical:.the.: coisponding velocity: rati:os for .:two- '-nd three-dineisona1odie.s do not: rmain a"cons.ta'nt;'hoWever:',

shapes deveiopêd::forh'ighcriticai speeds,', the ratio of'veloit.iês.:. may be ; con'idered to'approach a constant s a first. approximat1on' •'Inmubh as the: velocity dis.-

trihut5.ons for. similar' two-, and threediiriensional bodies are related, some similarity between profiles developed for optimum critical speed for 'two,dimensional wing inlets and three-dimensional nose in mi ght be

•- x .p .e o te.d. .. '. ,.

TIe profile of a symmetrical t zo-dimensional wing irlet (shape 9) is presented in refe rerce 12 High-speed test of this shae (refercnce 13) qow, or rreduni valuôs 'Of inIetvOlocityratio, 'apressur€x distribution app,roaching that of the three-dimensional NACA 1-series oeinits.' F.ime'3 presents the nondimensional pro-

file df shape 9 wingalnlet:fdr comparison with the NACA' i'seriés p ofile. Close agreement is noted. The' nondiiensional profiles for two- and three-dimensional ai inlets' developed to approach the optiniuin'from the standpoint 6f critical speed are thus shown to be essen-

. : jal1y similar. The NACA 1-series ordinates thus may have application to the experi m ental development of high-critical-speed two-dimensional wing ., Inlets.

It. is of interest to c'ompai'e the è1atibn between th.e .'mesured critical speed of , .thé shape 9 wing inlet and the critical speed estimated for a three-dimensional nose inlet from the pi--sent parer uth the factors for converting from three- to two-dImensioal flthis' derived from reference 11,, The :c,PP,a,1*P9n,. hows that the. measured critical speed 'of t.he.wng ppreciab1y 'lower than that waich. would 'be .pxedic.t:' 'y the ue cfd'a,,frqm'te' présezit paper and ,ref,?e,,,;: AltheUgh:.gene1' agrerient was :aS •to.:th shape , fQf . , the. corresponding pressure distributions for "similar two- and th'ree-dimensional po.ffles; nunieri I".'a'greement.'asto the manttude of the peak pr, sure should not, nec e s sari ly be expectod inasmuch as the results of reference 11 apply on '. .1" to '. E ei'1iic1 profile with no con-' s'idOrati6ii br dthit't'i' 1i at the -leadin g edge •

30 NACA'ACR Noi L5F30a

Gun hoods.- Low-drag hoods for Fun openings have been developed in reference,1)4 from the nose

4 ordinates presented in reference •2. The design of these gun-opening hoods or of gun.-bari'eI fairings.frorn which the gun barrel does not protrude can be determined by the nose-inlet selection charts (fig.. For.such a pplications the envelope curves of flgure')4.2 may have bo be extrapolated to low values of mas-,f1ow ratio. The proportions of the inlet section of the hood can be selected 'from this figure in the usual

of however, the design critical Mach

number 'should include consideration Of: the Induced-velocity field existing at the point of, application.

Detail Considerations

Comparison of critical speeds obtained expriment and by extrapolation,- The NAA 1-50-150 and 1-70-050 nose inlets, which are repesontative of a iqng nose inlet and a short-cowling-type nose inlet, respectively, were tested through the Mach number range.to 'approximately M 0 04 in order to compare the experimental variation in peak negative pressure coefficient with the theoretical varia-tion (the von Krrn 'n relation, reference )4.) assumed in the present paper for the determination of critical speeds. Figures 53( a ) and 54(a) show the variation of measured peak negative pressure coefficient with Mach number for the NACA 1-50-150-and 1-70-050 nose inlets at Oonstant values of inlet-velocity ratio. The lowest values of peak negative pressure coefficient follow approximately the theoretical increase with Mach number; however, the high values of peak negative pressure coefficient do not follow the theoretical variation. (See figs. 1)4. and 33 for the pressure distribution's over these nose-inlets.) This effect has been observed in previous inve'tigations in which sharp pressure peaks occurred over relatively sharp inlet lips (reference 13)..

The failure of the variation of peak negative pres-sure coefficient to follow the theoretical variation may be due in part. to the fact that, in compressible flows, the inlet-velocity ratio may not be the basic parameter,' which accurately defines the local flow angle at the inlet.

lip. Another per the: m.ss-'flow coefficient p0FV0'

reduces to A O/F,'the-ratio of the area of the stream tube for mass flow in at free-stream conditions' to the frontal are& F., This parameter therefore xpresse-s the

NACA ACR No. L5F30a . 31

amount that the stream tube must expand in approaching the inlet and thereby tends to govern the local angle of flow at the lip. Figures 53(b) and 54(b) present the variatThn ofpeak negative pressure coefficient with- , Mach number for constant values of the mass-flow coefficient. For low values of the. peak negative pressure coefficient, little difference exists between the theoretical and experimental variations with Mah number for constant values of v1/v0

or ofM

higher values of peak pressure, the ,p0FV0

experimental variation with Mach number for both parameters differs considerably from the theoretical variation; however, the variation for a constant value of the mass-flow coefficient more closely approaches the theoretical variation.

Comparisons of the critical Mach number characteris-tics obtained frbm high-speed data (figs. 53 and 54) and from extrapolation of data obtained at M 0 = o.L.o and 0.30 (figs. 18 and 37) are presented in figures 55 and 56. At high values of inlet-velocity ratio, the measured critical

• Mach numbers for both nose inlets are equal to or slightly greater than the critical Mach numbers estimated from the

• tests at M0 O.h0 and 0.30. For both hose inlets the knees of the experimental critical Mach number curves occur at lower values of Inlet-velocity ratio than those of the curves obtained by extra polation. Below the knees of the curves, therefore, the measured critical speeds are appreciably higher than • values obtained by extrapola-tion from M 0.40 and 0.30. The critical-speed-data presented for the series of nose inlets tested are there-fore indicated to be conservative by a small amount in the inlet-velocity-ratio range recommended for operation and by a larger amount for inlet-velocity ratios below the recommended range.

External separation.- The pressure distributions pre-sented for th& nose inlets tested have shown external-flow separation to occur over certain of the nose inlets at low inlet-velocity ratios and high angles of attack. The pres-sure distributions over the nose inlets tested having values of d/p Of 0J10 and 0.50 (figs. 9, 10, and 13 to 16) show no discernible separation through the test ranges. Certain of the nose inlets having values of d/D of 0.60 and 0.70.(figs. 21 to 25 and 31 to 314 ) however, show severe external separation or stall at the inlet lip; for example, the pressure distributions for the NACA 1-70-150 nose inlet (fig. 31) clearly indicate

32

NACA ACH No. L5F30a.

separated flow at low values . of inlet-velocity ratio. Figure 57 shows the critical Mach number characteristics for the NACA 1-70-150 nose inlet (taken from fig. 35), to which the curve of Mcr has been extended into the sepa -

rated range. The values of critical Mach number in this range of inlet-velocity ratio do not have their usual significance, because the flow has separated and the drag will have, reached excessive values even at low' speeds.

The inlet-velocity ratio belpw which separation occurs has been obtained from figures similar to figure 57 for the various nose. inlets tested and the results are plotted in figure 58. Also showr in figire 58 is a dashed curve indicating the value'of Vj7V 0 at the knee of the critical

)) for the various •values of X/D ived 'from the selection chart Inlet-velocity ratios equal to i.ven by thedashed curve in (I) the selection charts are

'Itical Mach number curve; e inlet will be selected on the Ions at which the inletve1ocity .ix've of design minimum inlet-the separation curves for all x/D. Figure 58 indicates,

Eparat1on will not occur, in nose inlets designed from the sent paper with the possible ving very low values of x/D ng1es of attack. By means of Lnlet-velocity ratio below which can be estimated for an

NACA 1-series nose inlet of proportions in the ranges shown.

The henomehon shown in figure 57 is of general interest with regard to investigations of specific air- inlet installations In rhich the critical s peed of an inlet may beetermined for only one value of inlet-velocity ratio. The measured (or estimated) critical seec1 may b* c'.eceptively high if the flow is semr::ted, and incorrect conclusions concerninr the ef.fiacy of the inlet may r'esult. Drag measurements and tuft surveys may be useful in verifying the results of an invest:i. tion of critical Mach number. In addition., comparison of critical Mach number values for several'inlet-veiocity ratios will gen-erally serve to define the flow conditions. The critical Mach number will normally increase or Deinain constant with increasing inlet-velocity ratio a decrease in critical Mach number with increasing V1/V 0 (fig.'57) generally indicates flow separation.

Mach number curves (a = 0 and d/D. A nose inlet de (fig. L2) will operate at or greater than the value figure 58 for two reasons: based on the knee of the c (2) for most cases,' the no basis of high-speed condit ratio is a minimum. The c velocity ratio falls above but the very low values of therefore; that external s general, for.NACA 1-series selection charts in the pr ece ption of nose inlets 'h or operating at very high figure 58 the approximate separation can be expected

MACA ACR No. L5F3Oa

Internal losses.- Internal total-pressure losses for the nose inlets tested were measured at the rake station (fig. 8) through the-ranges of inlet-velocity ratio and angle of attack. Inasmuch as the diameter at the end of .the nose-Inlet duct and the over-all length of the nose plus skirt was held constant for all tests, a corresponding value of diffuer angle 9 existed for each value of inlet-diameter ratio.. For nose inlets with' d/D values of o.Lo, 0.50, and 0.60 0 the values of diffuser angle were 7.60 , 3.8 0 , and 00, respectively.

A typical total-pressure-loss profile at the rake station is shown 'in figure 59. The total-pressure loss has been computed as a fraction of inlet dynamic pres-sure q1 . The total-pressure losses obtained for the MACA 1-140-150, 1-50-150, and 1-60-150 nose inlets from. Integration of figures similar to figure 59 are shown in fIgures 60(a), (b), and (c), respectively. A comparison of the magnitude of the pressure losses shows the effect of an increase In inlet-velocity ratio for constant diffuser angles,.

Figure 61 shows the variation of total-pressure loss with diffuser angle 8 for given values of inlet-velocity ratio and angle of attack. The adverse effect of large diffuser angles Is illustrated. Figure 62 shows the variation of total-pressure loss with angle of attack for two values of inlet-velocity ratio. This figure illustrates the increase of total-pressiire loss that occurs at high angles of attack for the large values of diffuser angle.

The integrated total-pressure losses for the MACA 1-50-150, 1-50-100, and 1-50-050 nose-inlets at two angles of attack are presented in figure 63. Inasmuch, as the value of X/D is a measure of the radius of curvature of the nose-inlet profile for a given value of d/D, comparison of the internal tot-al-pressure losses for these nose inlets indicates the effect of external curvature. The large external radius of curva-ture combined with the relatively small internal radius Is shown by the data for the MACA 1-50-050 nose Inlet to lead to internal separation at high values of inlet-velocity ratio and angle of attack.

Figure 61 shows the effects of Mach number on ' inte-grated total-pressure loss for the MACA 1-50-150 nose

34 NACA ACR No. L5F30a

inlet.' A slight decreaé in Internal losses generally occurs - with increase It-Mach humber within the range of teiti forth Is diffuser; ' It should be noted that the

iTiUm elftrance Mach nuftiber is 'about O.56

Nose .dnlet lpradi.- The internal lip radius for the NACA 1-series nose ir1e,ts tested was maintained at 0..025y, the value used in the deUeiopmei'it tet of references land 2. Froth considerations of external-pressur distributions, this nose radius appear to be satisfactory for the nose inlets having low values of d/D. For the NACA 1-70-030 nose inlet, however, the pressure distributions (fig. 34) show that a sharp local pressure peak occurs at the li p •at low values of inlet-velocity ratio. 'The NACA C cowling (fig. 5) also shows a.siiuilar effect. Because the lip radius was very small for these nose Inlets having large'values of a/D, an increase in lip radius was prunied to be desirable. The NACA C cowlIngwas theefdre tested with the lip radius increased to approximately twice the original value; the NACA 1-70-030 nose inlet was tested with ,a similar increase in lip radius and with an added internal fairing (fig. 6). 'The 'value of"a/D for these nose inlets was decreased from 0170 to 0.b9 by these modifications.

Figures 65 and 66 present pressure distributiois for the two nose inlets with increased lip radii. Com-parison of these figures with figures 3J and 45 shows, that the sharp 1oa1-pressure peak measured at the lip at low values of inlet-velocity ratio has been removed. The knees of the critical-speed curves (figs. 67 and 68) are consequently shifted to lower values of V,/V 0 , with the result that the critical speeds of these hose inlets are increased in this range. The internal losses measured for the original and modified lip radii were insignificant throughout the test ranges of inlet-velocity ratio and angle of attack. A lip radius somewhat in excess of 0.025y therefore seemsto be desirable for nose inlets of large values of d/D. Refernces 12 and 13 and other investigations indicate., hpwever, that inordinate. increases in lipradius can adversely affect the external-pressure distribution.

Effects of variations in basic rrofile.-Three,nose

inlets having... 1 = 0460 and = 1.50 And having pro-

files that differ from the NACA 1-series profile were

NACA ACR No. L5F30a

35

tested to show the effect of such differences (fig. 7). The first of these three profiles was derived directly from an elli pse. The second and third profiles were obtained by proportional* disto.-tion of the NACA 1-series profile according to the arbitrary equation

= Y _%r /2-t-l-L

where

y nondimensional ordinate of modified profile

y/Y nondimensional ordinate of basic profile (NACA 1-series)

K arbitrary factor

The two nose inlets tested are designated by the par-ticular value of the K-factor used i n their derivation,

pressure distributions over the three nose inlets at a 0 are presented in figure 6 along with the pressure distribution for the1ACA 1-&0-l0 nose inlet. The characteristic flat rressure distribution of the NACA 1-60-150 nose inlet at hih values of inlet-velocity ratio is not found for the modified nose inlets. Instead, a pressure peak overthe forward portion of the node occurs at all 'values of inlet-velocity ratio; the height of the peak is greatest for the nose inlet haviup; the greatest thickness near the lip.

Figure 70 shows the critical I.ach number character-istics for the modified nose inlets. An inlet-velo'c'ity-rat i o range for constant critical speed, which Is characteristic of the NACA 1-series nose inlet, does not exist for the modified nose inlets • The critical speed decreases with decrease in inlet-velocity ratio through the entire range. The critical Mach number curves are compared (at a = 0 0 ) . with those for the NACA 1-60-150, 1-60-100, and 1-60-075 nose inlets in figure 71. The comparison shows that the rat (e of decrease of critical Mach number for the modified noses is lower than the rate of decrease which occurs below the knee of the curves for the NACA 1-series nose inlets. The critical speeds for the modified nose inlets, however, are lower than those

36

NACA ACR No. L5F30a

of the NACA I-series nose inlets Of comparable maximum critical s peed, except at very-low values of inlet-., velocity ratio beyond the range wherein the comparable NACA 1-series nose inlets are designed to operate.

These tests show that deviations from the NACA 1-seriesprofile that cause appreciable departuTe from the characteristic flat pressure dIstribution can cause important reductions in critical speeds. The NACA 1-seriesordinates, which have been shown to approach closely the optimum from the standpoint of ciftical speed, should be accu±ately applied in order to realize the optimum characteristics.

Effect of variations in fi-neness ratio.- In order to investigate the effect of 'iaryin; the fineness ratio of the test body, the NACA 1-60-100 and 1-60-050 nose inlets were tested with and without cylindrical skirts. (The test body, however, as shown in fig. J, still retained a cylindrical length of 2 diameters.) The fineness ratio of the body. was decreased by 9 and 18 iercent for the NACA 1-60-100 and 1-60-050 nose inlets, respectively. The effect o.f these changes on critical-sped character-istics was found to be neg1i'4ble. Comparison of the

: critical speed of the NACA C cowling as measured on the test body of the present report and on. a nacelle in reference 1 substantiates this finding. The over-all fineness ratios of the test bod y and nacelle were 5.5 and 2J, respectively . The critical speeds measured for the 1TACA C cowling agree closely with the critical speeds measured In the tests of reference 1. The critical speed of the nose inlet therefore aoDears to he essentially independent of the over-all fineness ratio of the body. It should he noted, however, that this conclusion is based on tests of nose inlets which employed an appreciable length of cylindrical afterbody; other types of afterbody may appreciably affect the critical-speed characteristics..

SUMMARY OF RESULS

An analysis of the noseIni.et shapes developed in Previous investigations to represent the optimum from the standpoint of crItIcal s peed has shown that similarity exists between the nondimensioIal profiles of inlets which have widely different proportions and critical

1'1ACA ACR Nô t5F3 0a

37

speeds. With the nondimensional similarity of such prb- files established, the large differences in critical speeds of these nose inlets must he a functiOn of theix proportions.

The nondimensional ordinates of the 3 nose inlet, which.were developed in a previous investigation to be optimum from the standpOint of critical speed, were extended a'nd modified slightly to improve the fairing. These ordinates, now designated the NACA 1-series, were then applied to a group of nose inlets involving a sys-tematic variation of proportions. Wind-tunnel tests of these nose inlets were made through wide ranges of init-velocity, ratio and angle of attack at Mach numbers of 0.3 and 0.1. Tests of representative nose inlets 'ere carried to high speed (a maximum Mach iumher of 0.7). Pressure distrii5utiOns and critical Mach number characteristics are presented for each of the nose inlets tested. The results of these tests show that the length ratio (ratio of length to maimum diameter.) of the nose inlet, is the prima,,ry factor governing the znaximixn critical speed. The effect of inlet-diameter ratio (ratio of inlet diameter to maximum diameter) on critical speed is, in general, secondary; but this ratio has an important function in governing the extent of the inletvelocity-ratio range for maximum critical speed. The highest critical Mach number attained for any of the nose inlets tested was 0.89.

The data have beer ax'r:anged in the form of design charts from which NACA l'-series nose-inlet prdportions can be selected for given values of critical Mach number and air-flow quantity. Exam ples of nose-inlet selec-tions are presented for a typical iet 7 propulsion installation (critical Math number - of 0.t3) and for two conventional radial-engine installations . (critical Mach number of 0.76).

The selection charts and NACA 1-series ordinates have been shown to he applicable to the design of cowlings with spinners and to the design of high-critical-speed fuselage scoops. The possibility of application of the NACA 1-series ordinates to the experimental development of wing inlets is also indicated.

Langley Memorial Aeronautical Laboratory National Advisory Committee for Aeronautics

Langley Field, Va.

NACA ACF No. L5F30a

RE FERE N CE

1. Robinson, Russell (i., and Becker, John V.: High-Speed Tests of Conventional Radial-Engine Cowlings. MACA Rep. No. 745,. 1942.

2. Becker, John V.: Wind-Tunnel Tests of Air Inlet and Outlet Openings on a Streamline 3ody. NACA ACR, Nov. 1940.

. Becker, John v., and Baals, Donald D.: Wind-Tunnel Tests of a Submerged-Engine Fuselage Design. NACA ACR, Oct. 1940.,

4. von Krmn, Th. Comrnpressibility iffects in Aero-dynamics. Jour. Aero. Sci., vol. 8, no. 9, July 1941, pp. 37-356.

5. Silverstein, Abe, and ciryansky, uren R.: Develop-ment of Cowling for Long-Nose Air-Cooled Engine in the NACA u1l-cale Wind Tunnel. MACA ARR, Oct.

1941.

6. Valentine, E. Floyd, Preliminary Investigation Directed toward Improvement of the MACA Cowling. MACA AT.R, April 19h.2.

7. Molloy, Richard C., and l3rewster, James H., ITT: New Research on the Cowling and Cooling of Radial Engines. MACA ARR, May l9J2.

8 Preston, G. Merritt, and Weisinan, Yale, Investigation of an Individual-Duct Engine Cowl. MACA AHR, Oct. 1914.

9. McHugh, James G.: Progress Report on Cowlings for Air-Cooled Engines Investigated in the MACA 19-Foot Pressure Wind Tunnel, NACA AftR., July 1941-

10. Smith, Norman F., and Baals, Donald D.: W thd-Tunnel Investigation of a High-CritiCal-Spe ed Fuselage Scoop Including the Effec lk---s ofoundary Layer. MACA ACR No. L5BOIa, 1945.

11. Wright, Ray H. Estimation of Pressures on Cockpit Canopies, (un Turrets, Blisters, and Similar Pro- tuberances. NACA ACR No. L)4E1O , 19)4)4.

NACA ACR No. L5F3Oa 39

12. von Doenhoff Albert E, and btoñ, Elmer A.: Pre-liminary Invest1gatiOr in the NACA Low-Turbulence Tunnel of Low-Drag-Aixfo1 SectIons Suitable for Admitting Air at the Leading Edge. NACAAcR, July 1942.

13. Smith, Norman F.: High-Speed Investigation or'. Lo*-'ag Wing Inlets. NACA ALP No. L4I18, 1944.

]J.... Fedzluk, Henry A.: High-Speed Wind-Tunnel Tests of Gun Openings In the Nose of the Fuselage of a i/)4-Scale Model. NACA AM, July 19)42.

I. T

MACA ACR No. L5F30a

40

TA2LK I

NACA 1-SERIES ORDINATES

[ordinates In percent]

= ____ - For r = 0.025!: Y 0 d D

2.05


liz x/A y/Y x/x y/Y I/I y/y

0 0 13.0 41.94 34.0 69.08 60.0 89.11 .2 4.80 14.0 43.66 33.0 90.08 62.0 90.20 .4 6.63 15.0 45.30 36.0 71.05 64.0 91.23 .6 8.12 16.0 46.88 37.0 72.00 66.0 92.20 .8 9.33 17.0 48.40 38.0 72.94 68.0 93.11

1.0 10.38 18.0 49.88 39.0 73.85 70.0 93.95 1.5 12.72 19.0 51.31 40.0 74.75 72.0 94.75 2.0 14.72 20.0 52.70 41.0 75.63 94.0 95.48 2.5 16.57 21.0 54.05 42.0 76.48 76.0 96.16 3.0 18.31 22.0 55.37 43.0 79.32 78.0 96.79 3.5 19.94 2340 56.66 44.0 78.15 80.0 97.35 4.0 21.48 24.0 59.92 43.0 98.95 82.0 97.87 4.5 22.96 25.0 59.15 46.0 79.74 84.0 98.33 5.0 24.36 26.0 60.35 47.0 80.50 86.0 98.74 6.0 27.01 27.0 61.52 48.0 81.25 88.0 99.09 7.0 29.47 28.0 62.67 49.0 81.99 90.0 99.40 8.0 31.81 29.0 63.79 50.0 82.69 92.0 99.65 9.0 34.03 30.0 64.89 52.0 84.10 94.0 99.85

10.0 36.13 31.0 65.97 54.0 85.45 96.0 99.93 11.0 38.15 32.0 67.03 56.0 86.93 98.0 99.98 12.0 1 40.09 33.0 68.07 58.0 87.95 100.0 100.00

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NACA 1-70-030 nose /,ile1

NATIONAL ADVISORY

COMMITTEE FOR AERONAUTICS

Extrna/ surface

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7.8 NATIONAL ADVISORY


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NACA ACR No. L5F30a

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V12V001 / 0 .L.. COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

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Fig. 16

NACA ACR No. L5F30a

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-6 P.

Wo

.2

COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

//V0\

2 .54 .66

—N .96

lit!

x/X /9 12

Figure 16.- Pressure distributions over the NACA 1-50-050 nose inlet. M o = 0.40.

-/4

-I2

-/.

P-.6

-4

-2

0

2

.20

CY==78° .2 4 .,.8 /0 /2 /4

• -/4

-AU

P.

-4

-2

I

.20

• - -12

-w

-P-6

• 0•

2 .4 k 8 /0 /2 IV-

XP

0.2/

10 .3 SZ

NACA ACR No.:L5F3Oä

Fig. 16 Cone.

1(2/9

-L2

V, /yo

'Ot8°

-IA

- .

2

V/ /v, Lo .2/

ir4 3•90

0 2 . 10 12 /4

XO^ NATIONAL ADVISORY X/X COMMITTEE FOR AERONAUTICS

Figure 16.- Concluded.

Fig. 17

NACA ACR No. L5F30a

!Iij

rJ

.8 Mcr

.7

.5

• _

-

NATIONAL ADVISORY


.8

//ure / ?-Cri/ith/ Mach iiun be r. 'r yhe NACA /-50-20O ,ice 2

NACAACRNO. L5F306

Fig. 18

N I

.8

.7

.5

1 L -

/ e

/

A 001.

7COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

.6 .8Zo VIA

7wre /8. - Cri/ic,/ iVach l7umbers Lop //e 4/,4C4 1-50-150 nose

Al

58 _ ____

NATIONAL. ADVISORY


1.0

Re

.8

.7

Fig. 19 NACAACR No. L5F30a

o .4.6 .8 /0 V, A

are /9.-CrJ/ico'/ Mach rnrn7ber5

'2'T Me /V4C4 /-so-/oa ,'ose.in/e/

(deg)

7.8-s

•______

NATIONAL ADVISORY

COMMITTEE FOR AERONAUTICS I I I

,O

.8

.7

.6

.5

NACA ACR No. L5F30a

Fig.. 20

O .2 4 .6 .8

fwre 2 Criha/ /t'fach. number's • for lh' A CA n o 5 e 14 /e

0

0

0 z

1)

Q) Cl)

0 r. 0 0

c1I

0

0

z

a) 0

(I)

0

Erl

ul

CQ

a)

Fig. 21D NACA ACR No. L5730a

8

H: ±1 VOEJ

I I

Q

_L _J 0)

-

Ioo :

- •t- r-_ =

-. N N

No No.

Ow EMEuui'iiiMEMEMMINII MEMEMENIN Emommolim MEMEMMIllm EMEMENIIIIN

r

NACA ACR No. L5F30a

Fig. 21conc.

'0) fY)

I

--- - - nil

I I

I I I I

I"

L.1

c:I 0

co

0

a)

C)

0

CQ

L)

–4

a) I-i

0)

vODG ----

-

-'

oç-

—

I I 1Ii1__.I I

Fig. 22

NACA ACR No. L5F30a

F Ii

•II

N• /

N .:8 N)

0

U

0 E

4.,

cZ3G)

a)

0

0 IL)

0

N. L)

a)

1.1

a)

I rra)

to EO

s-I

r

CQ

a) 5-I

a

NACA ACR No. L5F30a Fig. 22 Conc.

a) C') - - N 0

I/o - JL I!

----

--

----c

a)

C)

0 C)

a)

c9 ¶ c:

Q---

0

•;q rr)

IIIIi t4t: 0

I I

I I

I.

Iz

N

I • I•_I I

MEMEMMEMIM MMEMEMMI MEMEMEME MOMMEMIll .....1/I. mmmmmmllm MMMMMM11,111 mmm mmm

I ANmm

Fig. 23

NACA ACR No. L5F30a

-/4

VD

-6

P H /V 7-<O./4--

O .21- \ \

I

COMMITTEE NATIONAL ADVISOPY

FOR AERONAUTICS

.6 .5

x/X10 /2

Figure 23.- Pressure distributions over the NACA 1-60-100 nose inlet. M 0 = 0.40.

_JA _IA

vl/vo

0 .32/vo

0 J9

O :43 £ .56

3.90

-1.2

-1.0

P6

0

7

-/2

-/0

0

2

v/ v. —7---Jo0.I4---- --- ./5 ,Z 29

1

c .7/

06 5:8

E_ - - - -- c_ 77_.(1 0.14-.23

\ ;:::=(> .48 -A .62

.70

-/2

-/0

-.4

0

2

.iz

p_6

0

2

NACA ACR No. L5F30a

Fig. 23 Conc.

o .2 4. /0

NATIONAL ADVISORY

2 .4 •o8 1.0 12 14

COMMITTEE FOR AERONAUTICS.

0 .2 .4 -1.0 /2 14 0 .2 4

6//0 12 1.4

Fi-gure 23.- Concluded.

.6 18 x/X

-.6 D /

-4

-/4

-/0

-2

2-

0

V,/V0 0.14 .21 COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

t>.7/ I ___ I I

1.0 /2

Fig. 24

NACA ACR No. L5F'30a

Figure 24.- . Pressure distributions over the NACA 1-60-075 nose inlet. mo = 0.40.

0) cla

V//VO

O=3.8°

I

7o .2/ /,-D .34 /

- 1.4 icr

-12

-Ia

-:5

P

0

2

!.1

-12

-/.0

-.8

-J

P-.4

0

2


0 .2 .4 £ .8 JO 121.4 0 2 .4 4 .8 40/2 14

x/x NATIONAL ADVISORY x/X

-h4

-12

-40

P

-2

0

—"1..

-12

)-:4

-2

0

2

I/V

cl .35

.7/

.68—_---_-----

.L

.6 .8 IO 12 14

- -

V//VO

/o.35-

7Jo.45

Iv.68------

-- - -- --- --- ------0 .2. .4 •6/).5 /0 /2 /4

Figure 24.-Concluded.

Fig. 25

NACA ACR No. L5F3Oa

a)

-/4-

-/2

-6

P-

—2

2

-,/' - <1

.13

.21

r[D4 SS

___ •

COMMITTEE

NATIONAL ADVISORY FOR AERONAUTICS

^:a

020

0 2 4 £ .5 /0 /2 /4 x/X

Figure25.- Pressure distributions over the NACA 1-60-050 nose inlet. M 0 = 0.40.

-

-/2

-I-U

P-.6 -.4

0

2

-- V//vl

U.6 7 70

1 5o

o .2 .4 .6 .8 10 12 14

x /X

-12

P

0

O 2 4 .6 .8 Al 12 14

x/X

NACA ACR No. L5F30a

Fig. 25 Cone.

C']

_IA--

-12

-/2

-ID

-ID

-.5

-.4

-:4

-2

0

0

7

2 o .z . .6 .8 1.0 121.4 0 .2 4 .(o .8 /0 12 14

x/X NATIONAL ADVISORY



NATIONAL ADVISORY


(c/eq) _ _____

/II

/ •11'

1' -7.0 /

10

ca

.8

.7

Im

• _

Fig. 26

NACA ACR No. L5F30a

F7qureZ6 -'CJ/caI Mach /'rnbQrs'

br Me 111,4C4 1-60-000 /lo5e

NACA ACR No. L5F30a

Fig. 27

ri#J

.8 ikcr

Eel

(a'eqY ____-

NATIONAL ADVISORY


o .2 4.6 .8

are 0 T-Crill-ic/ Mach nmber5

-lor Me iVA C4 1-60-150 ,,oe th/e 7L

Fig. 28

NACA ACR No. L5F30a

/0

•g

.8 ,t

.7

.6

.5

X,A

I /


0/V. .6 .8 /0

/7uTe Z8 - CthL,^a/ Math ,2uftthers /oi 1,4 e NA CA 1-60-100 rn2e , /e ,L

NACA ACR No. L5F30a

Fig. 29

t,.

L0

.8

7.

ml.8 10

VIAO

22- Criith/ ach nurnber5 r The /V4CA 1-60-075 nose i/et.

Fig. 30

NACA ACR No. L5F30a.

IC

.8 /Wcr

.7

.6

.5

—7.8 -

- _----_ /—

_-- --:_---ç ----:--

1 I ,/

NATIONAL ADVISORY


o .2 4 .6 .8 V/ A

/7wre 30-Cr11-1cc,1 /1//cich /2umber5

t Me A/A CA /-60--050 ise i/eiL.

NACA ACR No. L5F30.a Fig. 31

4 -*1,-, !^-I.

I .

Q,

U

-F _J 4-

N

8

— f-

vODj O<

0 z

4.)

a)

() U)

)

0

0 U)

z

co

In Id

U)

to a)

0..

a) I-.

Qo

II

-

If

VOD ___ ___

N

N N

N

0

a)

ao

-o


q.


-'.4

P:4

2

.2a .2

/2

Figure 32.- Pressure distributions over the NACA 1-70-100 nose inlet. m o = 0.40.

Separated

V,/V0

44COMMITTEE

NATIONAL ADVISORY FOR AERONAUTICS

V, ^0 0 0.22 0 35

,L

I

OA .4544

7

-

v,/ V

-/4-

-Az

-1.0

-:4

-2

0

2

-/4

1L9

F-:6

-4

0

p

V//vo tIiiiiF—T I

V, /vo o

C,-12

-/0

P-:6

0

9

Fig. 32 Conc. NACA ACR'No. L5F30a

UX/X

12 xi-


-/2

-/0

-'S

0

.2 4- .6 .8 10 12 /4- - 0 .2 .4

x/X

2


/0 12 14


I

-/2

-/0

P-4

U

.2

0 .24— %^^o

COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

S7 .63

0 .2 .4. .6

x/X

Figure 33.- Pressure distributions over the NACA 1-70-050 nose inlet. m o = 0.30.


-/4

-12

-10

P-A-

0

2 .1.

0 .2

-/

-:8

-:6

P

-2

0

2

-20

P-4

-2

0

.2 .4- .6.8 k 12 14 0 .2 .4 .6 .8 /0 1 /4

OX NATIONAL ADVISORYx/X


1-12

-IL

10

P

0

-.2 A

.6- /X .5 1 12 14

- ;;::c1t9./5__ 0.24

/ 0.36

Q'

\\ .24 7D .36 0.47

-°:

I V vo l

0 48

=5.7°

wv

AJ,—D .36 047--------------

o 2 .4. .6 & 10 12 /14


COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

I V0 vo

-"4

P-.4

NACA ACR No. L5F30a

Fig. 34

a) C3 t..

0 .2 4 .6 .6 x/X

Figure 34.- Pressure distributions over the NACA 1-70-030 nose inlet. M . = 0.40.

'v/v0 i9./3

o .2/. o .33

43 .52-

V sj-

I Icy,0

-12

-1.0

-4

0

qv,/V

-14--IA I-,-

-12

-/0

8

P6. -4

0

.2

1I0 2/ o .33

II

I'r

-12

-IL,

0

.2


4. .68 to z z 0

NATIONAL ADVISORY


-IA

-/2

-10

P

0

9

2 .6.8 10 12 tc

x/X

Y//VO

Ic ;

S\-2/3 /

.43

17-=ETO=78C

0 .2 .4 .6 / 5 /0 12 14- 0 .2 8 1.0 /2 1.4

^ I L


NACA ACR No. L5F30a

Fig. 35

N

1.0

Me

.5-

(a'q)

111 .1/7 _ NATIONAL ADVISORY;


44

.7

oV//VO

/Cy,pe 35.Cr//ca/ A/oh mi'bers

r Me NA (4 1-70- /50 /205 e th 4? 7

Fig. 6

NACA ACR No. L5F30a

.8

.7

0

.5

NATIONAL ADVISORY


1.8

3.6. /-

C .2V//VO

.6 .8

36. - Cti//cQ/ Mac nber5

br 7L/?e NACI4 /-70-/00 i,ose 112 le 4

NACA ACR No. L5F30a

Fig. 37

a) CJ t..

.9

.8

Cr1W

.7

(oeq)-

1.8

________

-

-__

/ NATIONAL ADVISORY


0 .4

8 v

37. -Cr,½th//WQ'c/2 rn//7iber5 he NACA /-70 -050 415e 1171e1.

WRA

-1.6

78 NATIONAL ADVISORY


Awl

.7

.5

Fig. 38

NACA ACR No. L5F30a

o

35. Crica/ Mo/c/i ihr /7C 5e //2k

S

NACA ACR No. L5F30a

Fig. 39a

/12

------X'7- 9 ___4____zo

•

.8

4r - 7 - - - -- --

.6 --

0 .2 4 .6 .8 /0

(YID =o.50

.9

.8

.7

.6

0 .2 .4- .6 .8 1.0 12 .2 .4.6 .8 /0

d/D=aoo NATIONAL ADVISORY (a) o= O°(nomi,'.?c,/)


FT2c/ure 39. - C riWca/ Mach number c hcirac ter!5 f/c of /VA CA 1-5 eries nose b/et5 te5/col, qrotiped accoro'/q to//z2

1.0

Envelope - 20

Tl

.5 --0 .2 .4.6 .8 /0

VIA c//D=040

.9

.8

.7

.6

Fig. 39b

NACA ACR No. L5F30a

.1.0 I I JJ/ope- -

.9 - iii-i

.8

.7

:

d/z7=c240

XID .:

8 M61

.7 --/7-/----

.6 I7iiZIIIII .5 _LLL

O .2 4.6 .8 /0

c///2= 2 6O

NATIONAL ADVISORY (b) COMMITTEE FOR AERONAUTICS

F7qre 39.- Coril/rn,'ecl.

.9 -- 0.0

.8 :=LO

Allcr . IIEEEE± .6 -- - L_

o .2 .4.6 .8 /0

d/D=O.50

/.0

.9

.8

.7

.6

0 .2 .4 .6 .8 /0VIA

d,V/2O.7O

= 2°(nomina/).

XID 50

/.0

• .30

1.50

NACA ACR No. L5F'30a Fig. 39c

I. U

/0

.9 .9

.8 .8 'A/Icr

.7 .7

.6 .6

O .2 .4 .6 .8 1.0 0 .2 4 .6 .8 /0

d/Z7 = O.40 /L=o.5o

VIA VIA

AlIct

1.0

.9 .9

.8 .8

.7 .7

.6 .6

.5-0 .2 .4 .6 .8 /0 0 .2 .4 .6 .8 /0

c//L7= 0.(50 0. 70 NATIONAL ADVISORY

(c) y- 0070m1hal) COMMITTEE FOR AERONAUTICS

fure 3 9. Coric/tided.

N I

/0 -

.9

.8

cr7 i°MZiii

.50

.S/

X/L7=2.o

/.0

.9

.8

.7

.6

.9 d/ 0.40 - = = = =

.8 -

- .00 -.70

46 '/0

X129= 1-5

1.0

.9

.8

N/cr .7

.6

.5 0 .2 .4 .6 .8 /0 0 .2 .4 .6

X/Di.o NATIONAL ADVISORY 0. 5 COMMITTEE FOR AERONAUTICS

ure O.- CrH/a/ iVach number crc/er//Jcs of NA CA 1-5erie5 no3e in/et-5 fe 5lLec/1 qroupecl

o accordinq to X/D. =0 .

Fig. 40 NACA ACR No. L5F30a


I_U

•

- - - - - 2 --

Allcr .7 -

.6

-

o .2 .4 .6 .8 /0

d/L7=0.4o

1.0

.9

.8 lvcr

.7

.6

1

0 .2 .4 .6 .8 /0 VIA

0.50

1.0

Au

.9 .9

.8 .8

'4r

.7 .7.

.6 .6

.5 0 .2 .4 .6 .8 /0 0 .2 4 .6 . /0

d10 :::'0 60 NATIONAL ADVISORY 0. 70 COMMITTEE FOR AERONAUTICS

,ure Ii.- Envelope curves forNA CA 1-5er/e5 nose i/eta alL lLhree al? q/e5 of attack (Ft-arn . 39

Fig. 42a

NACA ACR No. L5F30a

2.0

XID 10

0

• __________ uuauuiamau

No

M MEMBER - • UUN !

us.. UI •ViLLi •UU•U•W!

uuuumi •u•uuuui

• _________I

o .04 .08 .12 .16 .20 24 28 .32 .36 (/77


Fiure 42.-5e/ec/'on chcirf5 for /\/ACA 1-5erie5 no5e

NACA ACR No. L5F30a

Fig. 42b

XID

0

zo

.8

Mcr

.7

0 .0 .08 .12 .16 .20 .24 .28 .32 .36

(/0 F)miñ NATIONAL ADVISORY


(b)

Fl-pre 4 - Coric/iic/ecl.

Le

rej

.5

.3

.2

VO

Fig. 43

NACA ACR No. L5F30a

o D4 L28 ./2 .16 .20 .24 .28 .32 .30 .40 .44 .4

Fure 43.- Vorb tiôn of ,-f/ow coeff/c/e, t with /17/el-

ve/oc//q rci/io for a Q/Ve/') /VaC/) 171/m,ÔCr. (



o 12 .16 .20 24 28 32 36 40 44 .43

PC /\' NATIONAL ADVISORY COMMITTEE FOR AERONAUIICb

F/qare 43.- Concluded.

Fig. 44a-c

NACA ACR No. L5F30a

-I

U

o

>

jO 4'-Z La

0 I.)

N :^ o

o lb

-L

IZ Olc

q•) )

UI 1- -L

c.

"3 v

-

N

4- - LI)

c

u

ci Qi

vu

S.... -i---

¼

. vu vuQ

1

c: '<

- ," Q)

-

c,

c c: V) c..j Q)

1$-

Q-) I-0

I--

c ..

0° c

-/4

-/2

-1.0

P-4

U

.2x/X

.20

I 1_

COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

I ((.?%0J3

.52- .55 i J

1 -O.10

NACA ACR No. L5F30a

Fig. 45

a)

Figure 45.- Pressure distributions over the NACA C cowling. M 0 = 0.40.

V//Vo 4Q./3

0 21

V//V,-/.-5..

-/2

P-.4

-2

0

9

-1.-st

-/2

-/0

P-.6 -4

-2

0

9

Fig. 45 Conc. NACA ACR No. LSF3Oa

-/4

-/2

- a

-•6

P

0

9

(. - -/4

-/2

-/1.2

-:8

:6

P

0

2

I

V//VO -

V 0

I

11111 0 2 4- .6.8 / /2 14

x/X0.2 .4 .6 .8 10 12 14

' o . 4 .6.8 /0 12 /4

x/X0 .2 .4 .6 .8 /0 12 14

x/)c



Zo

IN

.8 /W

.7

I No

.5-

3.8

79

- - --

I // / N -' / NATIONAL ADVISORY


NACA ACR No. L5.F30a

Fig. 46

C')

.o .a

/,re 46.- Cthv/ Mach numbers-/0' i2'r %e NA CA . C Co w/inq.

Fig. 47

NACA ACR No;L5F30a

ol

.8 cr

.7

rel

.5

NA CA

1-60-050_

/-70 -030 - I

_[/70-050 -

__r

__=

__7Cco/i

= /A

NATIONAL ADVISORY


0 2 .4 .6V//vo .8

are ?- Com1oar, on of cr,i'kq/ /Vfcich namberchqrc'c/er/5/75 0/ NACA Ccow/461 and 1-ser/5 nose /I7kfs. 6kO.

(Cc

N

SAior/

L'on9 S

NACA ACR No. L5F30a

Fig. 48

(7) C) t.;.

A/ACA 1-66-06--

/VACA 1-73-043 cowlinq-1 /

Fiqore 48 NACA cow//nqs developed lot- use wi/A lcrqe sp/7/7er5..

NA CA I-series cowl,nqs of similar pr op or!ions superimposed for NATIONAL ADVISORY

comparison of profiles. COMMITTEE FOR AERONAUTICS

wl

-4

P

I-)

fç' IA V,/V" -Q•47 'I \\

Fig. 49a,b

NACA ACR No. L5F30a

Cow/thq 1b1-o///e

--

(a) NA CA DL c Ow/iig.

Cow/ui9 ,oro(,k

NATIONAL ADVISORY


(h) N14 C14 D cow//17q.

F,qur'e 49.- Pressure dsfribi//ons over /V/ICA D and

D5 2ow//q . (Da/a from references 5 atci 6.) 0 0 '

NACA ACR No. L5F30a

Fig. 50a,b

Eiaec/ curve or NACA N 1-66-064 nose .117/et - -0— -

Reference 5 o Wi'h pirner

C)

.8

.7

/k& .6

.8

.7

41cr .6

.5

.4

.2 .4 .6 .8 /0

(a) NA CA '7L cOkVl//19.

F I E51-,r1a/ecJ curve Ir N,4C.'4

173-043 nose

\ —1----0----

Reference 6 C/npub hshed es/5

o 5hOt7' 5p/flh)er o 5/,ort spinner

°Lonq sprnner No 5p,nner

o .2 .4 .6 .8 1.0

V, /VO NATIONAL ADVISORY


(b) NA CA D co/vl/2q.

Fiqure 50. - Cr,/,ca/ Mach numbers /r NACA 11Lc'nc/ 175

cow//.q. Es/irnaec/ curves br Il/ACA I- 5eries

COkV///lq.5' 5/-?OiWfl iti yure 18 ,/27c1.'c/ed 1c0

com,bcltison . =0°.

- V

-<N

NATIONAL ADVISOR

COMMITTEE FOR AERONAU

Fig. 51a,b. NACA ACR No. L5F30a

(a) Two - row radki/ enq/ñe.

Four - row radid/ e/7q11--7e.

FAcjure 5/. -[Kemp/es of NA CA I- series co w/ihqs de5/717ed

to pro vide on/y cy/iño'r coo/ihq or for Iwo /çipica/ raa2i/

enyes. Intern a/ cow/i/'q shape omitted. Desiqn

c ri/ica/ Mach number, 0.76.

NACA ACR No. L5F30a

Fig. 52

1 10

.9

.8 4r.

.7

.6

.5

NATIONAL ADVISORY


E5//n7c//edCurv6'1--or - 1- 62. 5-/lOnc.se/i/et

NACA

5coop plane 7inci'ure--

• 0 2 .4-/.6

fice 52. -Compa'1-150n 0'1-cc,7/,th/

5peed5 lop 5COO (from i. 200) of rel,'ence io)

and cori-e5pond/riq nose

ho/h cle5iqned from /VAA 1-5er1e5 0rc/rnate5. ctO

Fig. 53a,b

NACA ACR No. L5F30a

Experimenci/ ------Theoretith/ (from referencei-)

.-1

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P -.4

IIMMMMMMMW _0 —

(a) Con5/6,1 L vci/ues of k/. -:8

P-.4

_ U _EMMEMEMMUME_U.." - =E 'ii

.3. .4 .5 .6 .7 .8 NATIONAL ADVISORY o COMMITTEE,FOR AERONAUTICS

(b) Cons tan/ Lid/yes of ,n,/(p FI).

are 53 - Vara//on of peak 17eqcn4ve pressute coe f fic/eri 1 w/th /Llach number for /Lhe A/A CA 1-50 -150 nose inlet. =0.20

NACA ACR No. L5F30a

Fig. 54a,b

1

ON

'1)

I

MEMEMEMON MENOMONEE

MEMEMSENEI MOMEMEMME

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Figs. 55,56

NACA ACR No. L5F30a

- f --;---

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NATIONAL ADVISORY CONNITTEF FOQ AERONAUTICS

CD N I

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NACA ACR No. L5F30a

Fig. 57

• 0 .2 .4- .6 .8

/iqii e - Cri/ic/ Meich rnunber5

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N ao to

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Qi

CO c)

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Fig. 58a,b

NACA ACR No. L5F30a

-

J c-..

'p c)

I 1^

NACA ACR No. L5F30a.

Figs. 59,60a

T^t 19

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ME Ilm. III'.... OEMII1I

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NACA ACR No. L5F30a

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NACA ACR No. L5F30a

Figs. 61,62a,b,63

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Fig. 64

NACA ACR No. L5F30a

a) C\3

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COMMITTEE

• NATIONAL ADVISORY

FOR AERONAUTICS

0.13

0 3D

I 1

NACA ACR No. L5F30a

Fig. 65

a) -c%J

L';.

- Figure 65.- Pressure distributions over the NACA 1-70-030 nose inlet with increased

- lip radius. M o = 0.40.


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ccIarrTU FOl AEJONAUTICS

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NACA ACR No. L5F30a

Fig. 66

ML

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COMMITTEE

NATIONAL ADVISORY

FOR AERONAUTICS

.21 ,[I. V\-o

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Figure 66.- Pressure-distributions over the NACA C cowling with increased lip radius. mo = 0.40.

Fig. 66 Cone. NACA ACR No. L5F30a

v/vo

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NACA ACR. No. L5F30a

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• Figs. 67,68

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NACA ACR No. L5F30a

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-9

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.7

.6

NACA ACR No. L5F30a Figs. 70a-c,71

'a

0 .2 4 .5 .8 1.0 0 2 .4 .6 .8 /0JIV JIV

(a) El/i)of/cat (6) K ci 5:

fgw-e 70 . -0-/fithi Math ,umbers of the mod/f/ed nose inlets fes/ed.

a

S

.9

Mcr

.6

1.0 --- --

.9 -- P - -c- -

iti - - - - - -- - - — -

.7 ---- 3.8._

--- ----58 7-9

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wvo

Figure 70. -Concluded.

MEEMEEMMMM •uuuuuuuuu uur

MAIRIOMFERM MUS •iV4Ul• •iirauiuuuu •iiuuuuuui •wiuuuuuuu0 .2 .4 .6 .8 /0

VI/ vo

F7iure

7/.- Comparison of the criticQ/

Mach numbers of M4 modified and

/VAC/? I-series nose inlets. o,—o°

1111-1 iti' i ille re port/67531/metadc279653/m2/1/high_re… · file copy to be returned to...

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