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DESIGN OF A ROCKET INJECTOR FOR A LIQUID BI-PROPELLANT SYSTEM

DESIGN OF A ROCKET INJECTOR FOR A LIQUID BI-PROPELLANT SYSTEM. Presented by: Andrew Schwarz Woon-Ho Cho Simtha Sankaran AE 267 Instructor: Dr Periklis E. Papadopoulos December 7, 2004. Objective.

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DESIGN OF A ROCKET INJECTOR FOR A LIQUID BI-PROPELLANT SYSTEM

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  1. DESIGN OF A ROCKET INJECTOR FOR A LIQUID BI-PROPELLANT SYSTEM Presented by: Andrew Schwarz Woon-Ho Cho Simtha Sankaran AE 267 Instructor: Dr Periklis E. Papadopoulos December 7, 2004

  2. Objective Obtain the optimum propellant mixture ratio based on different injector parameters. The resultant mixture should impinge in an axial direction along the combustion chamber axis.

  3. Assumptions • Hypergolic ignition (no need for igniter) • Incompressible fluid • Resultant momentum at the point of impingement between the fuel and oxidizer flow is axially directed • Optimum mixture ratio based on optimum Isp • Adiabatic combustion and isentropic expansion of an ideal gas • Optimum expansion at nozzle exit (1 atm) • Combustion chamber pressure of 1000 psia (6895 kN/m2)

  4. Parameters • Input variables • Propellant combination (densities of fuel and ox) • Pressure Drop (across injector plate) • Discharge Coefficient (depends on quality of orifice) • Injector hole pattern (spacing and number of holes) • Diameter of oxidizer orifice • Diameter of fuel orifice • Output Values • Volume flow rate • Mixture ratio • Injection velocity • Combustion chamber cross-sectional area • Angle of impingement

  5. Cd - Coefficient of discharge A –Total injector area Dp- Pressure Drop across injector r –Density of propellant Equations Injection velocity Volume flow rate Mass flow rate Suffix o and f denotes oxidizer and fuel

  6. Injector Hole Pattern

  7. Equations (cont.) • Area • Ao(total) = No Ao • Af(total) = Nf Af D – Spacing between each concentric circle d - Spacing between each hole C – Circumference n - nth circle N – Total number of holes A – Area of hole • Hole pattern • Cn = π(nD) • Nn = Cn/d • N = ΣNn • Nf=N/2 No=N/2 Suffix o and f denotes oxidizer and fuel

  8. Equations (cont.) Axial flow (tan d = 0)

  9. Propellant combinations Fuels • Ammonia (NH3 )  • Analine (C6H5NH2)  • Ethanol (C2H5OH)  • Hydrazine (N2H4)  • Liquid Hydrogen (H2)  • Monomethyl-hydrazine (CH3)2NNH2 (MMH) Oxidizers • Nitrogen Tetroxide ( N2O4) • Hydrogen Peroxide (H2O2)  • Nitric Acid (H2NO3 ) • Liquid Oxygen (O2)

  10. Propellant Reactions N2O4 + N2H4 N2O4 + MMH H2O2 + N2H4 H2O2 + MMH H2O2 + NH3 H2O2 + C2H5OH H2O2 + H2 O2 + C6H5NH2 H2NO3 + N2H4 H2NO3 + MMH

  11. Baseline • Theoretical values for optimum mixture ratio • Dp is 15% - 25% of Pc • Pc is 1000 psia • Cylindrical injector and hole pattern • Like-unlike stream pattern • Experimental values of Cd

  12. Stream Pattern

  13. Discharge Coefficient

  14. Procedure • Program layout to find number of injector orifices Circumference of nth circle # of orifices on nth circle Total number of orifices # of concentric circles Spacing between circles Spacing between holes Number of oxidizer and fuel orifices

  15. Program outline to find optimum mixture ratio • Pressure Drop • Density • Coefficient of • discharge • Area • Total propellant flow • Volume flow rate • Injection velocity Mixture ratio Condition for axial flow

  16. Sample Data for Hole Pattern Calculation

  17. Results • The size of the fuel and oxidizer orifices directly affect the mixture ratio. • Changing the hole pattern only adds more mass flow to the combustion chamber. Mixture ratio stays the same. • The quality of the orifices (Cd) affects both the propellant flow characteristics and mixing properties.

  18. Conclusion

  19. Remarks Further applications can be applied: • Study heat transfer in combustion chamber wall near injector surface • Real gas chemical equilibrium combustion • Study combustion stability (pressure propagation and vibration) • Flow characteristics of the injector’s internal piping (more pressure losses) • Transient effects (starting and stopping conditions)

  20. References Rocket Propulsion Elements, George P. Sutton, Oscar Biblarz. 7th Edition. Wiley-Interscience, 2001 Mechanics and Thermodynamics of Propulsion, Philip Hill and Carl Peterson. 2nd Edition. Addison-Wesley, 1992 Aerothermodynamics of Gas Turbine and Rocket Propulsion, Gordon C. Oates. 3rd Edition. AIAA Series, 1997 Modern Compressible Flow, John D. Anderson. 3rd edition. Mc Graw Hill, 2003 Building GUIs with MATLAB, Version 5. The Mathworks Inc., June 1997 Encyclopaedia Britannica, 2004. Encyclopaedia Britannica Premium Service, Dec. 7, 2004

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