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MAE 5450 - Propulsion Systems

Project 3, CEA Exercise• This Programing Assignment is due on Beginning of Final Exam Period-- 11:30 AM MDT, Wednesday May 3.

• We are going to build a chemistry table for an AP-composite rocketPropellant, and investigate the effects due to increasing metallization of the grain.

• Look at important effects on flame temperature, molecular weights, andC* (infinitely expanded nozzle)

1


Download and Build CEA Code

2

• Down Load the CEAGUI from the NASA Glenn Research center Web site- Recommend you use the windows GIU as it seems to be bug free …- Linix code has a bunch of compile errors that need to be fixed- Special Setup Procedure for MAC User ..

http://www.neng.usu.edu/classes/mae/6530/propulsion_systems/section7/ceagui_FAQ_g77MacPC.pdf

• See … http://www.grc.nasa.gov/WWW/CEAWeb/ceaRequestForm.htm1)Update your comuter’s Java Runtime Environment, Reboot Computer

• Java SE Runtime Environment 8 Downloads

Works for most of you


• FCEA2.exe … built code for PC processor • Download all three(3) .zip files and save into the installation directory

• Extract (unzip) the CEAgui JAR file (CEAgui-jar.zip) • Extract (unzip)the CEA+ Fortran Package (CEA+Fortran.zip) for CEA files • Extract (unzip) the CEAexec Package (CEAexec-win.zip)

Download and Build CEA Code (2)

3

• You must have the 6! Unzipped files installed in the installation directory

à 1) CEAgui.jar, 2) thermo.lib, 3) trans.lib, 4) b1b2b3.exe, 5) syntax.exe, and 6) FCEA2.exe in the installation directory.)


Download and Build CEA Code (3)

4

• Directory Structure

Command Line (DOS) Interface

JAVA GUI Interface


Project Background

5

Need atLeast 15% minimumtotal HTPB binder by mass for “cake” to stick together

0.150≤MHTPB

MAl + MAP+ MHTPB( )Adiabatic Flame Temperature of AP/HTPB/Al Composite Propellant as function of Mass


Project Background (2)

• Investigate Mixture effects

Plot T0,g ,C* for both Chamber & Throat vs O/F for increasing aluminization levels

6

• Using equilibrium properties at Throat, plot data for various mixture ratios and determine optimal operating mixture ratio (based on C*) .. Assume T0 is constant through out motoe• Based on flow properties from nozzle throat … Update AMW L-700 model for “Best case” Formulation Properties

Assume that St. Roberts burn /erosive burn/Bates Grain parameters are same as previously used

O/F


Project Overview• Set up input file to run as “Rocket” Problem with a combustion pressure

of 3000 kPa (30 bars)

• Look AP Composite propellant with Mixture ratio of AP/HTPB/AL

• Run code in “equilibrium”, with “infinite” combustor contraction ratio

• Use results for molecular weight(Mw), ratio of specific heats (g), and combustion temperature to calculate and C*

1) Based on Chamber, g, Mw.2) Based on Throat (*), g, Mw.

…. Assume that T0chamber = T0*

7

etc.

etc.


Project Overview (2)

8

• Apply what we learn to AMW-L700 Motor Analysis

.. Look at both Cylindrical Port with both erosive burn and Bates grain .. Compare original and “improved” propellant” formulation (be sure to re-evaluate the propellant density based on formulation) Using new g, Rg, Mw, T0 ….......

Compare time history plots of chamber pressure thrustregression rate

Calculate and compare … total impulse .. effective Isp’s

… assume that Saint Robert’s burn parameters (a, n} and the erosionparameters (k, Mcrit) remain unchanged for new propellant


Project Overview (3)

9

• Based on Equilibrium flow “Frozen” at nozzle throat …

Compare to project 2 solution including erosive burn model for cylindrical grainand /Bates grain model

• Using equilibrium combustor properties from CEA


Equilibrium Properties at Chamber and Throat (example)

10

CHAMBER THROAT

P0/Pstatic 1.0000 1.7428P, BAR 31.000 17.787T, K 2925.58 2744.19RHO, KG/CU M 3.65500 2.2555 0H, KJ/KG 0.00000 -454.46U, KJ/KG -848.15 -1243.08G, KJ/KG -26683. 9 -25484.0S, KJ/(KG)(K) 9.1209 9.1209

MW, (1/n) 28.680 28.932(dLV/dLP)t -1.01044 -1.00776(dLV/dLT)p 1.2400 1.1912Cp, KJ/(KG)(K) 3.1727 2.9098GAMMAs 1.1495 1.1526SON VEL,M/SEC 987.4 953.4MACH NUMBER 0.000 1.000

Assume P0, T0 constant throughout motorCalculate C* based on local g (throat), Mw (throat) , T0 (chamber)


Chamber Pressure Ballistic Equation

11

Show that when “shifting equilibrium” from chamber to throat and then properties frozen at throat is used … the chamber pressure equation for solid motor must be modified as …

*, Mw* -> properties at throat

Rg -> based on molecular weight at chamber conditions, MwP0, T0 Chamber stagnation Pressure, temperature

Use modified chamber pressure ballistic equation in your follow-on analysis

*

Rg = Ru/Mw


Characteristic Velocity, C*• The characteristic velocity is a figure of thermo-chemical merit for a particular propellant and may be considered to beIndicative of the combustion efficiency.

• Lower Molecular Weight Propellants Produce Higher C*

• For this calculation based value on g, Mw

at the nozzle throat …

*

**

*

*

*


Mass Fraction Relationships

13

Relate O F to %( )NH4ClO4

→

O / F ≡MNH4ClO4

MHTPB+ MAL

%( )NH4ClO4

≡100%×MNH4ClO4

MNH4ClO4+ MHTPB+ MAL

⎛

⎝

⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟

⎧

⎨

⎪⎪⎪⎪⎪⎪⎪⎪⎪

⎩

⎪⎪⎪⎪⎪⎪⎪⎪⎪

⎫

⎬

⎪⎪⎪⎪⎪⎪⎪⎪⎪

⎭

⎪⎪⎪⎪⎪⎪⎪⎪⎪

→ %( )NH4ClO4

=100%×MNH4ClO4


⎛

⎝

⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟=100%× 1

1+MHTPB+ MAL

MNH4ClO4

⎛

⎝

⎜⎜⎜⎜⎜⎜⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟⎟⎟⎟⎟⎟⎟⎟

=100%× 1

1+ 1O / F

⎛

⎝

⎜⎜⎜⎜⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟⎟⎟⎟⎟

=100%× O / FO / F+1⎛

⎝⎜⎜⎜

⎞

⎠⎟⎟⎟⎟

Inverse→O / F =

%( )NH4ClO4

100%

1−%( )

NH4ClO4

100%


Mass Fraction Relationships (2)

14

…i.e. Mass Constraint Rsolid on terms of O/F and fal

Rsolid ≡MNH4ClO4

+ MAL


fAl ≡MAL

MHTPB+ MAL

MNH4ClO4= O / F( )⋅ MHTPB+ MAL( )

→ Rsolid =

MAL

MNH4ClO4

+1

MAL+ MHTPB

MNH4ClO4

+1

MAL

O / F( )⋅ MHTPB+ MAL( )+1

MAL+ MHTPB

O / F( )⋅ MHTPB+ MAL( )+1=

MAL


1O / F( )

+1

Rsolid =

MAL


1O / F( )

+1⋅O / F( )O / F( )

=

MAL

MHTPB+ MAL( )+ O / F( )

O / F( )+1=fAl + O / F( )O / F( )+1

Inverse→ O / F( )= Rsolid − fAl1−Rsolid



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…Summary

%( )NH4ClO4

=100%×MNH4ClO4


⎛

⎝

⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟

O / F( )=MNH4ClO4

MHTPB+ MAL( )

Rsolid ≡MNH4ClO4

+ MAL


fAl ≡MAL

MHTPB+ MAL

→

Mass Constraint

Rsolid =O / F( )+ fAlO / F( )+1

O / F( )= Rsolid − fAl1−Rsolid



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…i.e. Mass Constraint on terms of O/F and fal

O / FMax =

MAl + MAP

MHTPB+ MAl + MAP

⎛

⎝⎜⎜⎜⎜

⎞

⎠⎟⎟⎟⎟− fAl

1−MAl + MAP

MHTPB+ MAl + MAP

⎛

⎝⎜⎜⎜⎜

⎞

⎠⎟⎟⎟⎟

=0.85( )− fAl1− 0.85( )

fAl =MAl

MHTPB+ MAl

MAl

MHTPB

=fAl

1− fAl

Required .... MAl + MAP

MHTPB+ MAl + MAP

≤0.85



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…e.g. look at à fAl = 0.2 @ O/F = 5

Too High of Al Fraction! .. Must Lower O/F or f Al

MAL

MHTPB

=fAlf Al−1

=0.20.8= 0.25 → Required → Rsolid =

MNH4ClO4


⎛

⎝

⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟<0.85


=5( )+0.25( )+1

=5.26= 0.86667>85% ..... NO GOOD!

… look at à fAl = 0.15 @ O/F = 4.5

MAL

MHTPB

=fAlf Al−1

=0.150.85= 0.1765 → Required → Rsolid =

MNH4ClO4


⎛

⎝

⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟⎟<0.85


=4.5( )+0.15

4.5( )+1= 0.8455<85% ..... Just BARELY!


AP Composite Propellant Key Physical Properties

• AP chemical formula, NH4 Cl O4

18

Fine white powder usedas propellant oxidizer

Ammonium perchlorate crystals decompose before melting

When AP is mixed with a fuel (like a Al powder) or polymeric binder (like HTPB) it can generate considerable het release and allows self-sustained combustion once lit

ρNH4ClO4= 1.950 g

cm3

MwNH4ClO4= 117.49kg/kg−mol


AP Composite Propellant -- Key Physical Properties

• Powdered Elemental Al, micron-scale

19

Al Powder acts both as a fuel and combustion catalyst

(molecular weight) kg / kg −molΔH f0

= 0KJ /mol


Key Physical Properties, cont’d (2)

• HTPB -- (ARCO R-45TM, polymerization ~ 50)• Full Chemical Formula

• Butadiene C4H6, with n-50 degree of polymerization with hydroxyl termination (hydroxyl makes polymerized rubber more hydrophobic)

20

(C4H6)50 OH2 à Molecular Weight ~ 2766 kg/kg-mol

- OH

OH -


Key Physical Properties (3)

21

ρHTPB = 0.930 gcm3

C4H6( )⋅ OH( )0.40.04

• “Reduced” Chemical Formula w Broken Polymer Bonds

Molecular Weight ~ 54.68 kg/kg-mol

O2 H2 TARs

C4H6 (butadiene gas)

• Main “fuel” for combustion reaction

• Enthalpy of Formation Accounts for Energy Required to Break Polymer Chains

ΔH f0~ 23.99KJ /g−mol = 23.99×10

3KJ /kg−mol



22

• Insert HTPB PropertiesHere (Not in CEA tables)

• CEA calculates mass properties based on entered chemical formula

• HTPB Properties not listed in CEA tables



• Other Important Physical Properties

23

Need to calculate your propellant density for“best mixture”

ρHTPB = 0.930 gcm3

ρNH4ClO4= 1.950 g

cm3

ρAl Powder = 2700 kgm3



• Other Important Physical Properties

24

ρHTPB = 0.930 gcm3

ρNH4ClO4= 1.950 g

cm3

ρAl Powder = 2700 kgm3

ρ propellant =1

%NH4ClO4

100%

⎛

⎝

⎜⎜⎜⎜⎜

⎞

⎠

⎟⎟⎟⎟⎟

ρ propellant+

%Al

100%⎛

⎝⎜⎜⎜⎜

⎞

⎠⎟⎟⎟⎟

ρNH4ClO4+

%HTPB

100%⎛

⎝⎜⎜⎜⎜

⎞

⎠⎟⎟⎟⎟

ρHTPB


CEA Input File ….. Example < file >.inp

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problem o/f=1,1.5,2,2.5,3,3.5,4,4.5,5,5.5,6,6.5,7.,7.5,8,9, rocket equilibrium frozen nfz=1 tcest,k=3000 p,bar=30,

react oxid=NH4CLO4(I) wt=100 t,k=298 fuel=AL(cr) wt=25 t,k=298 fuel=HTPB wt=75 t,k=298 h,kj/mol=23.99 C 4 H 6 O 0.04 H 0.04

output plot p t rho m cp gam end

Setup file by default written to < file > input whenCode is saved using > “save as”

project 3, cea exercisemae-nas.eng.usu.edu/.../project3_assignment_2018.pdfproject 3, cea exercise...

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