10/29/2009nasa grant urc ncc nnx08ba44a supersonic combustion theresita buhler sara esparza cesar...
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10/29/2009 NASA Grant URC NCC NNX08BA44A
Supersonic Combustion
Theresita Buhler
Sara Esparza
Cesar Olmedo
10/29/2009 NASA Grant URC NCC NNX08BA44A
Supersonic Outline
• 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
• 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
10/29/2009 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
Combustion
• Fuel
• Air
• Heat
• High pressure flow, at high compression
• Quickly changing conditions
• Temperature difficulties– Frictional heating
– High forced convection
• Highly turbulent
• Shock
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
Jet Engines
• Inlet design– Feed air into chamber
• Compressor blades– Increase pressure of flow
• Combustion chamber– Introduce fuel– House combustion
• Turbine blades– Capture expansion of exhaust
gases
10/29/2009 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
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
ScramjetBoeing
10/29/2009 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
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
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
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
Design of Diffuser
• Initial design of diffuser• Use manifold design to
introduce fuel• Diffuser was designed in to
two separate pieces
Goal Seek18° 28.29°
19.67°
10/29/2009 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
Design of Diffuser
10/29/2009 NASA Grant URC NCC NNX08BA44A
2D Shockwaves
10/29/2009 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 AnalysisCosmo Flowork Analysis
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
Velocity Profile Mach Speed Profile
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
Pressure ContoursInlet Mach = 4.5
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
Temperature ContoursInlet Mach = 4.5
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork Analysis
10/29/2009 NASA Grant URC NCC NNX08BA44A
Ramp Fuel InjectionsRamp Fuel Injections
Ramped Outward
Ramped Inward
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
10/29/2009 NASA Grant URC NCC NNX08BA44A
Cosmos Flowork AnalysisCosmos Flowork Analysis
10/29/2009 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– Hydrogen
• 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
CombustionParallel Mixing
Fuel- Air Mixing at mach speedsGas 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
Mixing Layer
δmU1
U2
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionParallel 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
δmU1
U2
Ya
Ya
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionParallel 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
δmU1
U2
Ya
Ya
y
CDjA AFA
.
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionParallel Mixing
• Fick’s law for diffusion
dttxerf
yerfY
U
xD
CC
CY
y
CDjA
x
mA
c
FAm
FA
AA
AFA
0
2 exp2
41
2
1
8
.
Air ofFraction Mole Y
knesslayer thic Mixing
air ofion Concentrat
gradiention concentrat lateral theis
directiony in theflux diffusivemolar net theis
A
m
A
A
A
C
y
C
j
10/29/2009 NASA Grant URC NCC NNX08BA44A
Combustion Parallel Mixing
δmU1
U2
Ya
Ya
xofroot square with theinversely decreases
rate mixing maximum e that thdemostrate results The
0,772.14
41
2
1
equation ion concentratmolar theatingDifferenti
0
mmmyy
A
mA
Y
yerfY
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
δmU1
U2
Ya
Ya
B1+B2X=Lm
B1
-B2
y
x
X=0
10/29/2009 NASA Grant URC NCC NNX08BA44A
Combustion Parallel Mixing
FA
Cm
m
m
c
FAm
D
bUL
Lx
b
U
xD
16
for Solving
2
8
2
Mixing layer thickness equation
δmU1
U2
Ya
Ya
B1+B2X=Lm
B1
-B2
y
x
X=0
Estimate injector height, B1+B2=B
to reduce mixing length, Lm
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
Fuel
FuelAir
AirB δm
δm
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 )
1
12)(
2
)(
21
2
1
21
21
r
ruUUU
U
Ur
UUU
UU
c
c
r
r
u
x
u
x
yerf
r
r
u
u
c
c
1
1288
4
1
11
μ: dynamic viscosityν: 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
Micro-mixingFuel vortexFuel wave
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent Shear Mixing
• Mean velocity profile combines– Prandtl’s number
– Turbulent kinematic viscosity
– Time average characteristics of turbulent shear
3
431
11
yy
r
r
U
U
c
Micro-mixingFuel vortexFuel wave
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent Shear Mixing
Shear layer width – Two methods
m
m
lB
xr
rB
1
16 2
Local shear layer width for turbulent shear mixing
xr
rCm
1
1
Recent researchCδ is a experimental constant
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent 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
2
1
2
12
1
21
22
11
2222
2111
2
1
2
1
2
1
UU
UU
U
Us
PP
UUU
UUU
uPuP
s
c
c
c
c
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent Shear Mixing
• Convective velocity for the vortex structures
• With compressible flow using isentropic stagnation density equation changes to
2
22
1
11
1222
212
11
2/12
2/11
2
1
1
2
11
2
11
1
a
UUM
a
UUM
MM
s
UsUU
cC
cC
CC
c
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent Shear Mixing
• Density correct expression for shear layer growth including compressibility effects
213
1
2/1
2/1
2/1
2/11
8.2.)(
1129.1
1
11
12
1
1
1)(49.
cMc
cm
eMf
rrrsrs
rs
rs
rCMf
x
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent Shear Mixing
Only applies to box cowl
10/29/2009 NASA Grant URC NCC NNX08BA44A
CombustionTurbulent Shear Mixing
Based on what we know the angle of our hydrogen injection should be
To produce a hydrogen rich mixture
• Fuel
air
Lm, A
Lm, F
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
10/29/2009 NASA Grant URC NCC NNX08BA44A
Diffusion Combustion
• Symmetric flame
• Stoichiometric ratio– Varies across flame
• Flame center– Highest temperature, fuel
• Air lost around edges
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
10/29/2009 NASA Grant URC NCC NNX08BA44A
Supersonic Wind TunnelSupersonic 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
ApparatusApparatus
10/29/2009 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
HydrogenHydrogen
Scramjet X-43
Expensive fuel
Much less emissions than hydrocarbons
Dangerous
Invisible flame
Detailed analysis
Calculations & numerical
Safety procedures
Experimental
Safety analysis
O2HO2H 222
10/29/2009 NASA Grant URC NCC NNX08BA44A
Hydrogen Safety EquipmentHydrogen 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
Materials
Hastelloy
Nickel Steel
Reinforced carbon-carbon
BMI
Stainless steel 430
10/29/2009 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
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
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
Textbook ReferencesTextbook 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
Journal ReferencesJournal 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” 4 th 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
AcknowledgementsAcknowledgements
• Dr. H. BoussalisDr. H. Boussalis
• Dr. D. GuillaumeDr. D. Guillaume
• Dr. C. LiuDr. C. Liu
• Dr. T. PhamDr. T. Pham
• Dr. C. WuDr. C. Wu
• SPACE Center StudentsSPACE Center Students• Combustion TeamCombustion Team• Wind Tunnel TeamWind Tunnel Team
– Nhan DoanNhan Doan– Long LyLong Ly
• Sheila BlaiseSheila Blaise• Don RobertoDon Roberto• Cris ReidCris Reid• Dr. D. BlekhmanDr. D. Blekhman
– Cesar HuertaCesar Huerta– Celeste MontenegroCeleste Montenegro
• Dr. C. KhachikianDr. C. Khachikian– Keith BacosaKeith Bacosa
• D. MaurizioD. Maurizio