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Air Force Chemical Equilibrium Specific Impulse (Isp) Code

Air Force Chemical Equilibrium Specific Impulse (Isp) Code. Overview. The Air Force ISP code is a DOS-based thermochemistry code designed for rocket combustion/performance evaluation Performs similar functions as ‘Rocket’ mode of CEA Why use this code over CEA?

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Air Force Chemical Equilibrium Specific Impulse (Isp) Code

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  1. Air Force Chemical Equilibrium Specific Impulse (Isp) Code 1

  2. Overview • The Air Force ISP code is a DOS-based thermochemistry code designed for rocket combustion/performance evaluation • Performs similar functions as ‘Rocket’ mode of CEA • Why use this code over CEA? • Has optimization feature which allows code to be run over a large range of O/F’s, Pc’s, Ae/At’s, etc. with minimal input effort by user • Produces tabular summary of data which can easily copied into Excel, Matlab, etc. • Drawbacks to ISP Code? • Does not calculate thermal transport properties • Does not have additional functional capabilities that CEA has such as shocks, detonations, etc. • Software is available for download on AAE 539 course website 2/14

  3. Overview • There are two exectuable files that must be run to perform calculation: • INP.exe – Run this first – sets up inputs, desired outputs, and asks for input file name • ISP.exe – Run this second – asks for input file name, desired output file name, and executes code • *.DAT files contain propellant libraries, equilibrium reaction data, etc. • HLP.doc – Details the Optimizer functionality • Program has a fairly extensive library of propellants however not everything is there – you may have to enter some on your own 3/14

  4. Example • Continue with our example from class: • Oxidizer: O2(l) • Fuel: CH4(l) • Pc = 1000 psi • O/F = 0.1-20.0 (Run a range of mixture ratios) • Ac/At = 3.0 • Ae/At = 10.0, 25.0, 50.0 4/14

  5. Input Example (1/8) Run INP.exe Enter CH4(l) as Fuel Follow same steps for O2(g) as Oxidizer Now ready to enter proportions 5/14

  6. Input Example (2/8) Can enter fixed proportions here We want to run a range of mixture ratios from 0.1 to 20.0 by using the optimizer Mass Units We are running a ratio of oxidizer mass to fuel mass – must indicate this here We will fix the fuel mass at 1 and vary ox mass 6/14

  7. Input Example (3/8) Set the fuel mass fixed at 1 Set up a second relationship as the ratio of CH4 mass to O2 mass 7/14

  8. Input Example (4/8) Set initial mass ratio at 0.1 Set range of mass ratios from 0.1 to 20.0 with a step size of 0.1 Summary of relationships Press ‘Enter’ 8/14

  9. Input Example (5/8) Input Pc Input Ae/At Press ‘Enter’ 9/14

  10. Input Example (6/8) Setting optimization parameter at ‘constant’ permits code to run through all mass ratios Frozen Flow Press ‘Enter’ 10/14

  11. Input Example (7/8) Output Options Create Output Summary Press ‘Enter’ Press ‘Enter’ Select Parameters for Summary 11/14

  12. Input Example (8/8) Name & Save Input File View Inputs Exit Program Created file ch4o2.in 12/14

  13. Output Example (1/2) Run ISP.exe Portion of Output for O/F = 4.0 Creates file ch4o2.out 13/14

  14. Output Example (2/2) Portion of Output Summary for O/F = 5.1 to 7.7 Tabulated Quantities: 1) Mass of CH4 2) Mass of LOX 3) Vacuum Isp at Ae/At = 50 4) Chamber Temperature 5) C* using Chamber Properties 6) Thrust Coefficient at Ae/At = 50 14/14

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