DEVELOPMENT OF TURBOEXPANDER BASED DEVELOPMENT OF TURBOEXPANDER BASED NITROGEN LIQUEFIER

ByBy

P f R jit K S hProf. Ranjit Kumar Sahoo

Prof. Sunil Kumar SarangiDIRECTOR, NIT ROURKELA

Department of Mechanical EngineeringNIT R k l NIT Rourkela

CONTENTS

1 Liq efaction S stems1. Liquefaction Systems

2. Process Design

3 Major Components of Liquefier

4. Design of Heat Exchanger

5 Design of Turboexpander

3. Major Components of Liquefier

5. Design of Turboexpander

6. Design of JT Valve

7. Design of Phase Separator

8. Assembly of the Liquefier

9. References

7. Design of Phase Separator

9

i f i S1. Liquefaction Systems

Linde Cycle

In 1895, Carl Von Linde made this air liquefaction system

CompressorT=const

12

21 3Heat Exchanger

JouleThomson a

ture

, T

4g1

Thomson Valve

Tem

pera

3

fPhaseseparator Liquid

3

4 gf

Fig. 1 Fig. 2Entropy,s

Claude System

In 1902, Georges Claude made an air liquefaction system with anexpansion engineexpansion engine.

H E h

T=const1

2

3Compressor

Heat Exchangers

421 3 5

ture

, T

3

9

JTValve

g

1 78

6

9

3

Tem

pera

t

5

47

Expander

g

fe LiquidPhase6 gf

e

8

Fig. 3 Fig. 4

qPhaseseparator

Entropy,s

Kapitza System

In 1939 Claude cycle is modified by eliminating the third or lowIn 1939, Claude cycle is modified by eliminating the third or lowtemperature heat exchanger.

CompressorHeat Exchangers

421 3

JTValve

5

78

69

3

Expander

fe LiquidPh fe LiquidPhase

separator

Fig. 5

Heylandt Systemy y

In 1949, Davies modified the Claude cycle by eliminating the first heatexchanger

CompressorHeat Exchangers

exchanger.

Compressor

421 3

789JTValve

5

78

6

9

3

Expander

fe LiquidPhaseseparatorseparator

Fig. 6

P D i2. Process Design

CASE -1 (Claude Cycle)

CASE -2 (Modified Claude Cycle Eliminating Last Heat Exchanger)Last Heat Exchanger)

CASE -3 (Modified Claude Cycle Eliminating First Heat Exchanger)First Heat Exchanger)

CASE -1 Pressure 10 20 30 50 80 100 130 150

0 93 0 89 0 86 0 83 0 73 0 7 0 67 0 66 0.93 0.89 0.86 0.83 0.73 0.7 0.67 0.66Pinch1 3 3 3 3 3 3 3 3Pinch2 2 2 2 2 2 2 2 2Pinch3 1 1 1 1 1 1 1 1t 50% 50% 50% 50% 50% 50% 50% 50%m 1 1 1 1 1 1 1 1mf 0.05534 0.07933 0.09567 0.1155 0.142 0.1521 0.1644 0.171

CASE -2Pressure 10 20 30 50 80 100 130 150Pressure 10 20 30 50 80 100 130 150 0.93 0.89 0.85 0.82 0.71 0.68 0.65 0.62Pinch1 3 3 3 3 3 3 3 3Pinch2 1 1 1 1 1 1 1 1t 50% 50% 50% 50% 50% 50% 50% 50%

1 1 1 1 1 1 1 1m 1 1 1 1 1 1 1 1mf 0.05581 0.0797 0.09579 0.1161 0.1412 0.1517 0.1636 0.17

CASE -3Pressure 10 20 30 50 80 100 130 150 0.14 0.14 0.15 0.2 0.3 0.35 0.38 0.4Pinch1 3 3 3 3 3 3 3 3Pinch2 1 1 1 1 1 1 1 1t 50% 50% 50% 50% 50% 50% 50% 50%m 1 1 1 1 1 1 1 1m 1 1 1 1 1 1 1 1mf 0.003936 0.01319 0.0237 0.04673 0.07726 0.09425 0.1147 0.126

Fig. 7 Variation of Yield with compression pressure

Claude cycle (Case-1) (At 10 bar)

300 K 127.12 K103.93 Kx=0.2372

103.93 Kx=0.3230

105.34 K297 K

78.44 K90.45 K 102.93 K186 kW 14 kW 1.4kW

Kapitza cycle (Case-2) (At 10 bar)

300 K127.09 K 103.93 K

x=0.2355300 K

297 K 88 97

0 355

105.35 K 88.97

Animated Process Flow Diagram

Compressor

HX-

2b

HX-

2a

HX-

1 JTValve

Turboexpander

Phase separator

Fig. 8

8 bar310 K

1.1 bar300 K 7 95 bar

7.9 bar100 2 K

7.9 bar100 2 K

HX-

2b

HX-

2a

HX-

1

4g

9

C

Mixer-2

JTValve

310 K300 K 7.95 bar 100.2 K

Make Up

12

8

3

p 7

4

100.2 K

1.15 bar1.15 bar1.1 bar 1.2 bar

1.3 bar

1.2 bar78.8 K

1.2 bar78.8 K

Mixer-1UpFluid

5

5g

TurboexpanderLiquid

1.2 bar78.8 K

6

5f

Phase separator

Fig. 9 Process Diagram of Nitrogen Liquefier

Fig. 10 T-S Diagram of Nitrogen Liquefier

Parameters and Variables

Parameters

Eff ti f h t h 1 1Effectiveness of heat exchanger 1,1

Pinch point for heat exchanger 2, p

Efficiency of turbo expander,Efficiency of turbo expander,

Mass flow ratio diverted through Turbo expander,

Initial Values

Yield, y

Enthalpy of cold fluid at outlet of HX1,h9

Unknown Variables:

hp,h3, h4, h5, h6, h6s, h7, h8, h9, x5, y p 3 4 5 6 6s 7 8 9 5 y

i. Pinch point specification of Heat exchanger-2

Splitting the HX2 into two parts, First heat exchanger being the one where the hot

nitrogen gas is cooled up to the saturation temperature of 100.13 K & the second part

being the condensing part. The minimum temperature difference occurs at the point

where the condensation begins and is called as pinch point.

For the specified pinch value p, for HX2, we have

TT 4g3

pTT g4p =

We can get enthalpy hp, at that pinch

Pinch, p

pera

ture

g

4g

7

8

p

temperature and pressure

DistanceTe

m

7

Fig. 11

ii. HX1 and HX2a

Assume'219 hh = ( )18219 1h'hh +=Q

From HX1 and HX2a Energy balance

1y)](1h)(1h)(1h)y)(1(1[h

h p4g29+

=1. y)])(1[(h8

=

)]hh)(y1()1(h[ p8g4 +2. )1(

)])(y()([h p8g43

=

3. 81219 h)1('hh +=

Fig. 12

iii. Turbo-expander

From the figure,From Allprops, find s3, at h3 and p3.3 6s is the isentropic expansion3-6s is the isentropic expansion3-6 is the actual expansions6 > s6sg, the hot gas is not wet at the end of expansion

3s6 ss =The enthalpy at the end of expansion is found out as

h6 b t f 6 d 6 tur

e, T

h6s can be get from p6s and s6s.

Tem

pera

t

( ))hh(

hh

s63

63

=

)hh(hh s6336 =

Entropy,s

Fig. 13

iv. Mixer-2

]h)y1(h[h g567

+=

Applying energy balance equation for the mixer, enthalpy at outlet of mixer is

6 1.3 bar 1.2 bar 7)y1(

h7 1.3 bar

1.2 bar78.8 K 5g

Enthalpy at outlet of hot fluid is found out by energy balance between hot and cold fluids as

v .Heat Exchanger 2 Fig. 14

hot and cold fluids as

)1()]hh)(y1()1(h[h 7834

=

)1(

Fig. 15

vi. JT valve

45 hh =

Throttling is an isenthalpic expansion process. Equating the enthalpies before and after throttling

7.9 bar100.13 K4

45 hh =

)hh()hh(x f555

=

1.2 bar78.8 K

5

)hh( f5g5

vii. Yield

Th li id i ld bt i d k f i th h th th ttli l

Fig. 16

The liquid yield obtained per kg of gas passing through the throttling valve Is (1-x5), Here (1-) kg of gas passing through the throttling valve is

)x1)(1(y 5=

Fig. 17 Snapshot of the process design Program

3:Inlet to turboexpander and HX-2

3-6: Expansion in turbine

3-4: High pr. Stream in HX-2

1

92 4-5: Expansion in JT valve

7(5g+6) -8: Low pr. Stream in HX-2

P: Pinch point temp. (100.13-99.13)

4g

3

4 8

T-S Diagram5g

5 76

P

T S DiagramFig. 18

Parametric Study

Yield increases with increase inmass fraction through theturboexpander.

After a maximum mass fractionthrough the turboexpander, yieldstarts decreasing.g

The maximum mass fractiondecreases with increase in thepressure of compression

Fig. 19 Effect of Variation of mass fraction through

Turboexpander

pressure of compression.

Turboexpander

Parametric Study

Yield increases with increase inthe effectiveness of the HX-1.

A i i ff ti i A minimum effectiveness ispresent after which the yieldbecomes zero.

Requirement of higheffectiveness increases withincrease in compression

Fig. 20 Effect of Variation of

pressure

Fig. 20 Effect of Variation of effectiveness 1 of HX-1

Parametric Study

Yield decreases with increasein the pinch point of the HX-2.

The rate of decrease in yield isless with pinch point of HX-2p p

yield increases with increase incompression pressure

Fig. 21 Effect of Variation of pinch point of second heat exchangerpoint of second heat exchanger

Parametric Study

Yield increases with increase inthe efficiency of theturboexpander.

yield increases with increase inycompression pressure.

Fig. 22 Effect of Variation of turbo expander efficiency turbo expander efficiency

M j C t f Li fi 3. Major Components of Liquefier

Major Components Of The Liquefier

i. Compressor

ii. Cold Boxii. Cold Box

iii. Heat Exchangers

iv. Turboexpanderiv. Turboexpander

v. JT Valve

vi Liquid nitrogen Separator along with vi. Liquid nitrogen Separator along with transfer line

i. Compressor

Screw oil flooded,compressor : 340

3/h 11 bnm3/hr, 11 bar(Kaeser make)

This compressor isThis compressor isavailable in ourlaboratory with oil filter,pressure controller andppipe layout.

ii Cold Boxii. Cold Box

It is a double walled 750di 1800mm dia x 1800 mm

height cylinder.

4. Design Plate Fin Heat Exchanger

Basic Components of a Plate Fin Heat Exchanger

Parts of plate fin heat exchanger

Cross Flow and Counter Flow

Types of flow in a Heat exchanger

FIN TYPES

Fig. 25 Different types of fin

Advantages of Offset Strip Fins Plate Fin Heat Exchanger

Large heat transfer area per unit volume

Flow area goodness factor: Ratio of the Colburn factor tofriction factor for the given surface is higher for the OSF asfriction factor for the given surface is higher for the OSF ascompared to other fins.

High effectiveness: very close temperature approachesHigh effectiveness: very close temperature approachesbetween streams.

Significant reductions in size, weight.

Thermal input data for HX-1

Thermal data of process stream Nitrogen

Hot FluidInlet temperature 310 K

Outlet temperature 120 45 K

Cold Fluid

Inlet temperature 100.74 K

Outlet temperature 305 8 KOutlet temperature 120.45 K

Mass flow rate 82.22 g/sec

Pressure at inlet 8 bar

Allowable pressure drop 0 05 bar

Outlet temperature 305.8 K

Mass flow rate 78.68 g/sec

Pressure at inlet 1.15 bar

Allowable pressure drop 0.05 barAllowable pressure drop 0.05 bar Allowable pressure drop 0.05 bar

All properties like density , enthalpy, specific heat, viscosity, prandtlnumber are determined at mean temperature and pressure.number are determined at mean temperature and pressure.

Effectiveness , UA , heat load are also calculated from the above inletand exit conditions.

INPUT :

1 Fin frequency f1. Fin frequency, f

2. Fin thickness, t

3. Fin length, lf

4. Fin height, hg

5. Plate thickness, p

Basic dimensions of fin used in the heat exchangerBasic dimensions of fin used in the heat exchanger

HX-1 Fin Specification Hot and Cold Side

Fin frequency 714 fins/mFin metal thickness 0.2 mmFin length 1.5 mmFin height 6.3 mmSeparating plate thickness 0 8 mmSeparating plate thickness 0.8 mm

l

CALCULATION :

Fi P t

1. Fin spacing,

2. Plate spacing, b=h+t

ffts )( = 1

Fin Parameters

S- fin spacingH- fin heightT- fin thicknessl- strip length

2. Plate spacing, b h t

3. Free flow area per fin,

4 F t l fi

htsaff )( =

))(( thtGeometry of a typical offset strip fin surface

l strip length4. Frontal area per fin,

5. Heat transfer area,

))(( thtsafr ++=

slhthlas 222 ++=

6. Fin area,

7. Equivalent diameter,

hthlaf 22 +=

slhthlhltsDe ++

=

=

)(area transferheattotal

lengthareaflow free total 24

8. Ratio of fin area with total surface area,

9. Frontal area ratio,s

f

aa

=

ff

aa

=fra

10.Dimensionless parameters for the finhsh

=

sl

=

t

Assume width of heat exchanger, W and No. of layers in hot and cold side, nh and nc.

st

=

11.Total area between plates,

12.Total free flow area,

WnbAfr =

fff AA = 12.Total free flow area, frff AA =

13.Core mass velocity,ffAmG =

GD14.Reynolds number,

15.Critical Reynolds number

eGD=Re

217043312170581568 ... )()()(.*Re = jj19601006023648 ... )()()(.*Re = f

Maiti Correlations for offset serrated fins

For Re>Re*,005018402880420180 )()()((R ) j

0230185022102860320 .... )()()((Re). = f

F R R *

005018402880420180 .... )()()((Re).= j

06302702750510360 .... )()()((Re). = j

104018101960700

For Re

Manglik and Bergles Correlations for OSF fins

0678.01499.01541.05403.0Re6522.0 = j

[ ] 1.0055.1546.0504.0340.15 Re10269.51 + 2659.03053.01856.07422.0Re6243.9 =f

[ ] 1.0236.0767.3920.0429.48 Re10669.71

+

f

Where

hs

=

lt

=l

st

=

shlD 2( ) tsslhthlDe +++= 2

Joshi and Webb Correlations for OSF fins

For Re

17.Convective heat transfer coefficient, 6670.(Pr))( cjGh =

18.Fin parameter,

19.Fin effectiveness,

)*()*(tKhM

f

c2=

tanh( )f

Ml =19.Fin effectiveness,

20.Surface effectiveness,

21 O ll h t t f ffi i t

( )f Ml =

)()( fo

fo A

A = 11

h )/A(ApA1121.Overall heat transfer coefficient,

22.The ratio of total heat transfer surface area

coc

ohoc

WW

o

hoho h)/A(A

AKpA

hU++=

11

* tNf1to the separating surface area (wall area) ,

23.Heat transfer area may now be calculated as )/(

*/of

wo AAtNfAA

=1

1

UoUoAoAo =

24.The required length of the heat exchanger is calculated from the equivalent diameter definition, as

AffAoDeL

**

4=

2

25.The pressure dropbDe

fLGp2

2=

Effect of longitudinal heat conduction

1. Frontal area of fin, HWAfrt *=

2. Free flow area for hot fluid Affh

3. Free flow area for cold fluid, Affc

4. Wall conduction area,

5 Conductivity of fin K

frcfrhfrtw AAAA =

5. Conductivity of fin, Kw

6. N.T.U required

==

11

11 .ln

)(.. R

R

CC

UTN

7. Assuming a Factor of safety = F.S

8. N.T.U (considering longitudinal heat conduction), SFUTNUTN lc .)..()..( =

9. UA considering longitudinal conduction min*)..()( CUTNUA lclc =

10.Area considering longitudinal conduction,UUAA lc)(=

AD 11.Length of the heat exchanger (considering longitudinal heat conduction)

12.Wall conduction parameter,ff

oe

AADL

=4

minLCAwKw=

13.Dimensionless parameters,

14.-

CrUTNy *..*=

))(()(yCr

Cr+

=

111

15.-

))(( yCr +11

+

++=

yyyy

)()()/(( /

11

11 21

16.-

17

)()(

+

=11

UTNCr r1 ..*)(17. -

18. Ineffectiveness

CrNTUr r

+=

11)(

CrrCr

=)exp(

)()(1

11

19.Effectiveness

)( 1

)]([ = 11

Dimensions of the HX-1

D k M lik J hi & Deepak Manglik Joshi & Webb

Core length 2002 1888 2277

Core width 180 180 180

Core Height 165 165 165Core Height 165 165 165

Number of layers in hot side 10 10 10

Number of layers in cold side 9 9 9

2D Drawing views & Photograph of HX-1

Thermal input data for HX-2

Cold fluidHot fluid Cold fluid

Inlet temperature 91.38 K

Outlet temperature 100.81K

Mass flow rate 78 68 g/sec

Inlet temperature 120.45 KOutlet temperature 100.2 K,

x= 0.064M fl / Mass flow rate 78.68 g/sec

Pressure at inlet 1.2 bar

Allowable pressure drop 0.05 bar

Mass flow rate 4.9 g/sec

Pressure at inlet 7.95 barAllowable pressure drop 0.05 bar

HX-2 fin specificationFin Density 714 & 500 Fins/mPlate spacing 6.5 mmPlate spacing 6.5 mmFin length 10 mm

Separating platethickness

0.8 mmthicknessFin metal thickness 0.2 mm

2D Drawing views & Photograph of HX-2

5. Design Turboexpander

1. A turboexpander, is a centrifugal or axial flow turbine through

which a high pressure gas is expanded to produce work that is

often used to drive a brake compressor.

2 T d i h b d fi d f2. To design the turboexpander a fixed state of process stream

parameters or design point is required. So the design point is

fixed as per the process design done previouslyfixed as per the process design, done previously.

Working Fluid Nitrogen

The design points are as follows

Turbine inlet temperature, Tin 124 K

Turbine inlet pressure, Pin 7.97 bar

Discharge pressure, Pex 1.2 bar

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Mass flow rate, m 76.46 g/s

Major Parts Of Turboexpander

Turbine Wheel

Brake Compressor

Shaft

Aerostatic Thrust BearingAerostatic Thrust Bearing

Tilting Pad Bearing

Nozzle

Diffuser

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Brake compressorBrake compressor

Shaft

Turbine Wheel

Shaft with brake compressor and Turbine wheel

Turboexpander Assembly

Brake compressor

Turbine wheel

DiffuserBrake nozzleshaft

Nozzle

Tilting Pad Bearing

Aerostatic thrust Bearingg

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Turboexpander Assembly Animation

Design Of Turbine Wheel

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ns ds diagram show the maximum obtainable efficiency and theoptimum design geometry as function of diameter and speed of thep g g y pturbine.

d s

ns

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ns ds diagram for radial inflow turbiness

Specific speed and specific diameter of the turbine wheel are calculated by 3Qby

4/33

3

)( sins h

Q

=

4/132 )( hDd sin

(1)

(2)3

32 )(Q

d sins =

WhereexQkQ *13 =

(2)

(3)exQQ 13

)()( 023 exsinsin hhkh = (4)

To achieve the maximum possible efficiency, within the subsoniczone, the value of specific speed and specific diameter selectedfrom the n d diagram of Baljefrom the ns ds diagram of Balje.

ns= 0.5471and ds = 3.4728

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Ratio of eye tip diameter to turbine inlet diameter,tipD (5)2

0.6tipDD

= =

Ratio of eye hub to eye tip diameter ,

(5)

0.425hubtip

DD

= =

Power produced

(6)

0( ) 2.8523in exP m h h= =

Power produced,

(7)kW

Number of blades=10

Thickness of blades= 0.6 mm

Blade height at inlet,.

2 ( )t rmb

D Z t C= (8)

2 2 2( )t r t r mD Z t C ( )

Dimensions of the Turbine wheel

O t di t f th t bi 29 6Outer diameter of the turbine : 29.6 mm

Speed of the turbine : 1,38,778 rpm

Eye tip diameter : 17.8 mm

Eye hub diameter : 8.9 mm

Number of blades : 10

Thickness of blades : 0.6 mm

Height of blade at turbine inlet : 0.7 mm

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Velocity Triangle

Inlet to Turbine (m/s) Exit to Turbine (m/s)

C2 187.38 C3 110.31

W2 94 48 W3 152 97W2 94.48 W3 152.97

U2 215.11 U3 96.8

2 60.38o 3 45.92o

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2 26o 3 95o

Determination Of Blade Profile

The blade profile determined by Haselgrubbers method assumingThe blade profile determined by Haselgrubber s method assuming

pressure balanced flow path.

This technique gives three dimensional contours of the blades andThis technique gives three dimensional contours of the blades and

simultaneously determine the velocity, pressure and temperature

fil i th t bi h lprofile in the turbine wheel.

Design of Brake compressor

Input parameters:

Process gas : Air/Nitrogen

Power to be dissipated : 2.85 kWPower to be dissipated : 2.85 kW

Angular speed : 14534.67 rad/s (1, 38,777 rpm)

Inlet total pressure : 4.1 barp

Inlet total temperature : 300 K

Expected efficiency : 60%

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Specific speed and Specific diameter are given by

,

4/31

ss h

Q

=

p p p g y

(9)

1

4/12

QhDd ss

= (10)

951= 92=d

to achieve the subsonic operation within the constraints of available power and rotational speed,

and (11)95.1=s 9.2=sdand28524/)( 22

211

22 === DQUmP sfbsf W

(11)

(12)

i t f t 1 02 power input factor 1.02 = =Slip factor 0.9sf = =

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Dimensions of Brake Compressor

Di t t i l t 15Diameter at inlet : 15 mm

Diameter at outlet : 33.7 mm

Blade height at inlet : 3 mm

Number of blades : 12

Thickness of blades : 0.75 mm

Power to be dissipated : 2.85 KWPower to be dissipated : 2.85 KW

Angular speed : 14534 rad/sec

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Dimensions of Nozzle

Wt = Throat widthtDt = Throat diameter

Dn = Nozzle diameter

D2 = Turbine inlet diameter

Cn = Chord length

Width at throat 84.1== trtmw mm (13)Width at throat, 84.1

tttnt CbZw

Throat angle, 01 06.29tan =

= mtt C

C

( 3)

(14)g ,

t

t C

Blade pitch length, 79.3== ntn ZDp mm (15)

Inner diameter of nozzle ring,829222 =+= CosDwwDD mm (16)8.292 =+= tttttin CosDwwDD

Chord length of the nozzle is given by

2 S

mm (16)

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4.4sin

2cot1

22

=

++

=

sz

nuSuCh

mm (17)

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Design of Diffuser

1 Kinetic energy at the rotor outlet should be recovered using a1. Kinetic energy at the rotor outlet should be recovered using a

diffuser.

2. The best suited diffusing angle which minimizes the loss ing g

pressure recovery is 5o-6o

20.0148 0 00087exQ

A (18)20.00087 m17

exex

ex

QA

C= = =

The exit diameter is found out to be 33.3 mm

(18)

Assuming radial clearance 0.1 mm

The inlet diameter is 29.8mm

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The length of the diffuser is 87.4 mm

Design Of Shaft

We have chosen the diameter of the shaft and checked for maximum

stress and critical speed .

Di t f th h ft 16Diameter of the shaft = 16 mm

The length of the shaft and dimension of the collar depends upon the

dimensions of the bearings.

Length of the shaft = 108 1 mmLength of the shaft 108.1 mm

Diameter of the collar = 44 mm

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P i h l d t th ti f th ll

Check for maximum stress:

Peripheral speed at the tip of the collar(14534.67 0.036)

2 116.272surf

V d = = =1

(19)m/s

Stress at the root of the collar, MPaVsurf 23022531 2

Gas Lubricated Bearings

Advantages of gas bearings1. Clean operation

2. Lower viscosity provides low friction,resulting in lower heat

generation.

3. Gases are chemically stable over a much wider range of

t t

Disadvantages of gas bearingstemperatures

1. Lower load carrying capacity.

2. Suffer from problem of instability.

3 Demand high mechanical precision

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3. Demand high mechanical precision.

Gas Lubricated Bearings

Two types of bearings used for the turboexpandert

A. Thrust Bearingsi Aerostatic Thrust Bearing

rotor

i. Aerostatic Thrust Bearing

ii. Aerodynamic thrust bearing

iii. Thrust Foil Bearing

i. Rubber stabilized Aerostatic Journal Bearing

B. Journal Bearingsust o ea g

ii. Pivot less Tilting Pad Journal Bearing

iii. Aerodynamic Journal bearing

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iv. Journal Air Foil Bearing

Aerostatic Thrust Bearings

A double or combined thrustbearing consists of a pair of thrustplates, with the shaft collar inbetween, forming the bearingsurfaces.

Neutral Load on

Upper Thrust Plate

Thrust Collar

Lower Thrust PlateShaft

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W

Aerodynamic Thrust Bearings

It has shallow angled groovescut in one of the bearingcut in one of the bearingsurfaces.

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Thrust Foil Bearings

T F il

Bump FoilBump foil Gas bearings consist of three parts: Top Foilparts:

a. top foil b. bump foil structure c. the bearing housing

Advantages:1 Self-acting

Bearing Housing

1. Self-acting.

2. Rotor dynamically stable.

3. Accommodate thermal growth.

4. Accommodate Misalignment.

5. High ability to damp.

66. Better wear resistant.

Rubber Stabilized Aerostatic Journal Bearings

Rubber Stabilised Aerostatic Journal Bearings consists of a plain aerostaticbearing mounted on a pair of rubber O-rings. The O-rings convert the rigidaerostatic bearing to a flexible one, so that enough damping is provided topass over the limiting speed of half speed whirl.

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pass over the limiting speed of half speed whirl.

Pivot less Tilting Pad Journal Bearings

It consists of three pads floatingaround the journal, within the padaround the journal, within the padhousing, surrounded by gas filmson all sides.

Pad made of high density metal impregnated graphitePad made of high density metal impregnated graphite

Aerodynamic Journal Bearings

In a herringbone grooved journalHerringbone grooved bearingbearing, the grooves are cut in the

form of two opposing helices

Journal Air Foil Bearings

Top Foil As the shaft rotates a Top Foil

Bump Foil

aerodynamic pressure isgenerated between therotating shaft and the p

Gas Filmsmooth top foil due towedging.

A d i Bearing Block Aerodynamic pressuredetermines the loadcarrying capacity of shaftand it deforms the top foiland it deforms the top foiland bump foil to preventcontact between rotor andbearing, which results zerobearing, which results zerowear of the bearings.

Modification in Turboexpander

Present Model Modified Model

Supporting structures

The major supporting structure of the turboexpander areThe major supporting structure of the turboexpander are

A. Cold end casing

B. Bearing housingg g

C. Warm end housing

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Supporting structures

A C ld d i1. The cold end housing is the lower

t t hi h i bl t h ld th

A. Cold end casing

most part which is capable to hold the

Teflon insulation rings so that the heat

could not enter into itcould not enter into it.

2. It contains nozzle diffuser centrally.

3 It takes the process gas inside and3. It takes the process gas inside and

cooled gas comes out centrally from

the diffuser.

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Supporting structures

B. Bearing block

The bearing housing is the central

component providing support to the

t j l b i d th ttwo journal bearings and the two

thrust bearings.

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Supporting structures

C Warm end housing1. The warm end housing has a nozzle to

the brake compressor which is fitted

C. Warm end housing

p

above brake compressor by shrink fit

operation.

2. There is an inlet and exit tube through

which air is sucked in and compressed

air goes outair goes out.

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Fabricated of Turboexpander Parts

Turbine wheel Brake compressor

Shaft

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Shaft

Tilting pad journal bearing Aerostatic thrust bearing Nozzle Diffuser

N lLock Nut (Compressor Side) Lock Nut (Turbine Side)

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Nozzle coverLock Nut (Compressor Side) Lock Nut (Turbine Side)

Spacer Exhaust gas plate

B i bl k C

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Compressor end Bearing block Cold end housing

Photograph of Turboexpander test setup

H.P. Pressure Vessel

Bearing supply gas

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Turbine inlet gas Turbine exit gas

v. JT ValveJ a e

A Swagelok make fine needle valve is converted to act as a expansionJT valve.

It is connected with a long pipe so that it will be easier to operate theIt is connected with a long pipe, so that it will be easier to operate thevalve from the top of the cold box flange, while it will be quite belowinside the cold box.

vi. Phase Separator

A 25 liter capacity phase separator has been designed andfabricated.

3D model of Liquefier3D model of Liquefier

Liq. Nitrogen exit

Exit to the CompressorInlet to the HX1

Turboexpander

Inlet to the HX1

HX2

HX1

Cold Box

Phase separator

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