Supersonic Combustion Theresita Buhler Sara Esparza Cesar Olmedo 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Supersonic Outline Engine: Cowl design Combustion schemes & fuels Exhaust: Expansion Prototype design Materials Design Specifications Installation in the wind tunnel Location Fuel lines and ignition wires Hydrogen safety History Cost Acknowledgements Questions Purpose & Goals Introduction to combustion Engine parameters Jet Engine Ramjet Scramjet Jet Engine vs. Scramjet Model Reference stations Analytical approach Compressible flow Shockwaves Inlet: Diffuser design COSMOSWorks design ADD PICTURE OF OVER-EXPOSED DIFFUSER 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Hypersonic Vehicle High speed travel Commercial flight Reaction engines Circumnavigation in four hours NASA Goals Global reach vehicle Reduced emissions Challenges Shockwaves High heat Combustion instability Flight direction control NASA X-43 Vehicle NASA X-51 Testing 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Combustion Fuel Air Heat High pressure flow, at high compression Quickly changing conditions Temperature difficulties Frictional heating High forced convection Highly turbulent Shock ADD PICTURE FOR COMBUSTION 10/29/2009 NASA Grant URC NCC NNX08BA44A

Engine Parameters Fit engine to aerospace system Jet Engines – Low orbit, max Mach 3 Ramjets – High altitude, supersonic flight, subsonic combustion Scramjets – High altitude, hypersonic flight, supersonic combustion 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Jet Engines Combustion chamber Introduce fuel House combustion Turbine blades Capture expansion of exhaust gases Inlet design Feed air into chamber Compressor blades Increase pressure of flow Cesar Olmedo 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Ramjet Vehicle travels at supersonic speed Simplest air-breathing engine No moving parts Compression of intake achieved by supersonic flow – inlet speed reduction Shockwave system Relatively low velocity Combustions at subsonic speeds Very high reduction in speed High drag High fuel consumption Temperature at 3000 K (4940°F) Diffuser Exit plane contracts Exhaust at supersonic speed Travel: M = 3 Combustion: M= 0.3 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Scramjet Hypersonic flight No moving parts Combustion at Supersonic speed Flow ignites supersonically Fuel injection into supersonic air stream Steer clear of shock waves Is Aerodynamically challenged 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Scramjet Boeing 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Then and Now 10/29/2009 NASA Grant URC NCC NNX08BA44A

What is Supersonic Combustion Combustion maintained at supersonic speed How is it achieved? Design Shockwave Fuel Injector Detonation Combustion 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Shock Waves Oblique shocks Mach number decreases Pressure, temperature, and density increase Attached to vehicle Normal shocks Mach number decreases Pressure, temperature, and density increase Creates subsonic region in front of nose Detached 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Shock Waves Oblique shock Mach number decreases Pressure, temperature, and density increase Expansion wave Mach number increases Pressure, temperature, and density decrease 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Diffuser Development Wind tunnel specifications Inlet speed Mach 4.5 Cross-sectional area 6 x 6 in Length of test section 10 in 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Design of Diffuser Initial design of diffuser Use manifold design to introduce fuel Diffuser was designed in to two separate pieces Goal Seek 18° 28.29° 19.67° 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Design of Diffuser Top part of the diffuser Has machined holes for fuel and ignition wires. Also four holes for securing the base of the diffuser 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Design of Diffuser 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A 2D Shockwaves 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Inefficient Designs Bow Shock – Cowl Interference Oblique Shock – Cowl Spillage 10/29/2009 NASA Grant URC NCC NNX08BA44A

Cosmo Flowork Analysis Mesh used by Cosmo to perform calculation on the diffuser. 10/29/2009 NASA Grant URC NCC NNX08BA44A 20

Cosmos Flowork Analysis Do we need a scale ? To determine the magnitude on this pictures? Velocity Profile Mach Speed Profile 10/29/2009 NASA Grant URC NCC NNX08BA44A 21

Cosmos Flowork Analysis Pressure Profile of original Design Pressure Contours Inlet Mach = 4.5 10/29/2009 NASA Grant URC NCC NNX08BA44A 22

Cosmos Flowork Analysis Temperature profile of original design Temperature Contours Inlet Mach = 4.5 10/29/2009 NASA Grant URC NCC NNX08BA44A 23

Cosmos Flowork Analysis 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Ramp Fuel Injections Ramped Outward Ramped Inward 10/29/2009 NASA Grant URC NCC NNX08BA44A

Cosmos Flowork Analysis Mach sped 10/29/2009 NASA Grant URC NCC NNX08BA44A

Cosmos Flowork Analysis Pressure 10/29/2009 NASA Grant URC NCC NNX08BA44A

Cosmos Flowork Analysis Density 10/29/2009 NASA Grant URC NCC NNX08BA44A

Cosmos Flowork Analysis Velocity 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Combustion Combustion Stoichiometry Ideal fuel/ air ratio Recommended fuel for scramjets Hydrogen Methane Ethane Hexane Octane Only Oxidizer is Air Maximum combustion temperature Hydrocarbon atoms are mixed with air so Hydrogen atoms form water Oxygen atoms form carbon dioxide Most common fuel for scramjets In scramjets, combustion is often incomplete due to the very short combustion period. Equivalence ratio Should range from .2 -2.0 for combustion to occur with a useful time scale Lean mixture ratio below 1 Rich mixture ratio above 1 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Fuel- Air Mixing at mach speeds Gas phase chemical reaction occurs by the exchange of atoms between molecules as a results of molecular collisions. The fuel and air must be mixed at near-stoichiometric proportions before combustion can occur Parallel Mixing of Fuel- Air U1 Mixing Layer δm U2 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Zero shear mixing Both air and fuel velocities are equal Shear stress doesn’t exist between streams Coflow occurs Lateral transport Occurs by molecular diffusion At fuel – air interface No momentum or vorticity transfer Axial development of cross –stream profiles of air mole fraction YA in Zero shear (U1=U2) Fuel Mole fraction Profile is YF=1-YA Mirror Image Ya Ya U1 δm U2 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Molecular diffusion Fick’s Law Air molecular transport rate into fuel Proportional to the interfacial area times the local concentration gradient. Proportionality constant DFA, = molecular diffusivity Where DFA*ρ is approximately equal to molecular viscosity μ for most gases Ya Ya U1 δm U2 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Fick’s law for diffusion 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Ya Ya U1 δm U2 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Steepest concentration gradient at x = 0 Mixing layer reaches the wall at x=Lm the air mole fraction still varies from 1.0 at y=B1 and 0 at y= -B2 More mixing is needed 2Lm is recommended by experiment enables complete micro-mixing δm U1 U2 Ya B1+B2 X=Lm B1 -B2 y x X=0 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Mixing layer thickness equation Estimate injector height, B1+B2=B to reduce mixing length, Lm δm U1 U2 Ya B1+B2 X=Lm B1 -B2 y x X=0 You can reduce Uc, decrease B , increase Dfa or combination of all three to shorten Lm But since Uc and Dfa are effected by design and physical properties the only solid change is B by manifolding 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Parallel Mixing Manifolding idea Multiple inlets Reduce mixing length Tradeoff: Inefficient design Adds bulk and volume Air B δm NEED TO ADD LM ON THIS ONE, CP! Fuel Air δm Fuel 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Laminar Shear Mixing Molecular diffusion alone cannot meet the requirements of rapid lateral mixing in supersonic flow Solution shear layer between both layers U1>U2 , Uc=0.5(U1+U2 ) Velocity ratio r =(U1/U2 ) Velocity Difference Δ U= (U1-U2 ) μ: dynamic viscosity ν: kinematic viscosity 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent shear mixing As we further increase the velocity difference delta U Shear stress causes the periodic formation of large vortices The vortex sheet between the two streams rolls up and engulfs fluid from both streams and stretches the mixant interface. Stretching of the mixant interface increases the interfacial area and steepens the concentration gradients Shear mixing increases molecular diffusion 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent shear mixing EXPLAIN Fuel wave Fuel vortex Micro-mixing 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent Shear Mixing Mean velocity profile combines Prandtl’s number Turbulent kinematic viscosity Time average characteristics of turbulent shear Micro-mixing Fuel wave Fuel vortex 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent Shear Mixing Shear layer width – Two methods Local shear layer width for turbulent shear mixing Recent research Cδ is a experimental constant 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent Shear Mixing Density effects on shear layer growth – compressible flow Based on constant but different densities A density ratio, s, is derived s can be calculated once stagnation pressure and stream velocities are known 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent Shear Mixing Convective velocity for the vortex structures With compressible flow using isentropic stagnation density equation changes to 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent Shear Mixing Density correct expression for shear layer growth including compressibility effects 10/29/2009 NASA Grant URC NCC NNX08BA44A

Combustion Turbulent Shear Mixing EXPLAIN, CP 10/29/2009 NASA Grant URC NCC NNX08BA44A Only applies to box cowl

Combustion Turbulent Shear Mixing Based on what we know the angle of our hydrogen injection should be To produce a hydrogen rich mixture Lm, F Fuel air Lm, A 10/29/2009 NASA Grant URC NCC NNX08BA44A

Diffusion Combustion Mixing Controlled Combustion High mixture temperature High reaction rates Limiting feature: mixing Reaction Rate Controlled Low mixture temperature Adequate mixing Limiting feature: reaction rates Rate of heat release Picture and explanation 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Diffusion Combustion Symmetric flame Stoichiometric ratio Varies across flame Flame center Highest temperature, fuel Air lost around edges READ SECTION TO EXPLAIN FLAME BETTER 10/29/2009 NASA Grant URC NCC NNX08BA44A

Conductive Combustion Diffusion and premixed combined Stoichiometric ratio Determined by pre-mixture Flame center Highest temperature, fuel Air lost around edges explanation 10/29/2009 NASA Grant URC NCC NNX08BA44A

Supersonic Wind Tunnel Commission of pressure tank Team Assistant dean Don Maurizio Technician Sheila Blaise Professor Chivey Wu Wind tunnel team : Long Ly, Nhan Doan 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Apparatus 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Fuel Supply Follows test rig of wind tunnel Stainless steel lines Leak proof Tank pressure 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Hydrogen Scramjet X-43 Expensive fuel Much less emissions than hydrocarbons Dangerous Invisible flame Detailed analysis Calculations & numerical Safety procedures Experimental Safety analysis 10/29/2009 NASA Grant URC NCC NNX08BA44A

Hydrogen Safety Equipment Tank Carbon fiber, non-burst tank Liquid check valve Gas flashback arrestor Infrared camera FLIR Thermacam $3,500.0 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Materials Hastelloy Nickel Steel Reinforced carbon-carbon BMI Stainless steel 430 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Costs Group Item Price Fuel Hydrogen + Regulator Catalyst - Silane $275. $125. Materials Steel $400. Manufacturing In-house Wind Tunnel Retrofit Gauges, Channels, $350. View Windows 2 Sapphire 1” x 0.375” $700. Total $1,850. 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Future Work Analytical study Compressible flow Gas dynamics Diabatic flow Chemical kinetics in supersonic flow Numerical analyses FLUENT Supersonic wind tunnel Manufacturing Compressible flow class with Dr. Wu Document calculations 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Dramatic Quotes Sustaining supersonic combustion is “like trying to light a match in a hurricane” “There is currently no conclusive evidence that these requirements can be met: nevertheless, the present study starts with the basic assumption that stable supersonic combustion in an engine is possible” -Richard J. Weber 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Textbook References Anderson, J. “Compressible Flow.” Anderson, J. “Hypersonic & High Temperature Gas Dynamics” Curran, E. T. & S. N. B. Murthy, “Scramjet Propulsion” AIAA Educational Serties, Fogler, H.S. “Elements of Chemical Reaction Engineering” Prentice Hall International Studies. 3rd ed. 1999. Heiser, W.H. & D. T. Pratt “Hypersonic Airbreathing Propulsion” AIAA Educational Searies. Olfe, D. B. & V. Zakkay “Supersonic Flow, Chemical Processes, & Radiative Transfer” Perry, R. H. & D. W. Green “Perry’s Chemical Engineers’ Handbook” McGraw-Hill Turns, S.R. “An Introduction to Combustion” White, E.B. “Fluid Mechanics”. 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Journal References Allen, W., P. I. King, M. R. Gruber, C. D. Carter, K. Y Hsu, “Fuel-Air Injection Effects on Combustion in Cavity-Based Flameholders in a Supersonic Flow”. 41st AIAA Joint Propulsal. 2005-4105. Billig, F. S. “Combustion Processes in Supersonic Flow”. Journal of Propulsion, Vol. 4, No. 3, May-June 1988 Da Riva, Ignacio, Amable Linan, & Enrique Fraga “Some Results in Supersonic Combustion” 4th Congress, Paris, France, 64-579, Aug 1964 Esparza, S. “Supersonic Combustion” CSULA Symposium, May 2008. Grishin, A. M. & E. E. Zelenskii, “Diffusional-Thermal Instability of the Normal Combustion of a Three-Component Gas Mixture,” Plenum Publishing Corporation. 1988. Ilbas, M., “The Effect of Thermal Radiation and Radiation Models on Hydrogen-Hydrocarbon Combustion Modeling” International Journal of Hydrogen Energy. Vol 30, Pgs. 1113-1126. 2005. Qin, J, W. Bao, W. Zhou, & D. Yu. “Performance Cycle Analysis of an Open Cooling Cycle for a Scramjet” IMechE, Vol. 223, Part G, 2009. Mathur, T., M. Gruber, K. Jackson, J. Donbar, W. Donaldson, T. Jackson, F. Billig. “Supersonic Combustion Experiements with a Cavity-Based Fuel Injection”. AFRL-PR-WP-TP-2006-271. Nov 2001 McGuire, J. R., R. R. Boyce, & N. R. Mudford. Journal of Propulsion & Power, Vol. 24, No. 6, Nov-Dec 2008 Mirmirani, M., C. Wu, A. Clark, S, Choi, & B. Fidam, “Airbreathing Hypersonic Flight Vehicle Modeling and Control, Review, Challenges, and a CFD-Based Example” Neely, A. J., I. Stotz, S. O’Byrne, R. R. Boyce, N. R. Mudford, “Flow Studies on a Hydrogen-Fueled Cavity Flame- Holder Scramjet. AIAA 2005-3358, 2005. Tetlow, M. R. & C. J. Doolan. “Comparison of Hydrogen and Hydrocarbon-Fueld Scramjet Engines for Orbital Insertion” Journal of Spacecraft and Rockets, Vol 44., No. 2., Mar-Apr 2007. 10/29/2009 NASA Grant URC NCC NNX08BA44A

NASA Grant URC NCC NNX08BA44A Acknowledgements Dr. H. Boussalis Dr. D. Guillaume Dr. C. Liu Dr. T. Pham Dr. C. Wu SPACE Center Students Combustion Team Wind Tunnel Team Nhan Doan Long Ly Sheila Blaise Don Roberto Cris Reid Dr. D. Blekhman Cesar Huerta Celeste Montenegro Dr. C. Khachikian Keith Bacosa D. Maurizio 10/29/2009 NASA Grant URC NCC NNX08BA44A