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The Role of Density Gradient in Liquid Rocket Engine Combustion Instability Amardip Ghosh

The Role of Density Gradient in Liquid Rocket Engine Combustion Instability Amardip Ghosh Aerospace Engineering Department University of Maryland College Park, MD 20742 Advisor - Kenneth Yu Sponsors- NASA CUIP (Claudia Meyer) NASA/DOD. Liquid Rocket Engine (LRE). Combustion Chamber

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The Role of Density Gradient in Liquid Rocket Engine Combustion Instability Amardip Ghosh

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  1. The Role of Density Gradient in Liquid Rocket Engine Combustion Instability Amardip Ghosh Aerospace Engineering Department University of Maryland College Park, MD 20742 Advisor - Kenneth Yu Sponsors- NASA CUIP (Claudia Meyer) NASA/DOD

  2. Liquid Rocket Engine (LRE) Combustion Chamber With Shear Coax Shower Head Shear Coaxial Injector SSME – LOX / LH2 Arianne 5 – LOX / Kerosene Soyuz – LOX / Kerosene Ghosh, 2008 PhD

  3. Combustion Instability Onset of Instability Stable Combustion Combustion Instability • Large amplitude pressure oscillations (Reardon, 1961) • Increased heat transfer rates to the combustor walls (Male, 1954) • Increased mechanical loading on the thrust chamber assembly • Off Designoperation of entire engine • CatastrophicFailures Ghosh, 2008 PhD

  4. Scope of present work • Correlations Exist • Injector Geometry • Outer Jet Momentum • Outer Jet Temperature • Recess • Hydrocarbon Fuel • Lacking • Physics Based Mechanisms • Predictive Capability • Recognized as a key element controlling LRE stability margins • Rich Physics • Reacting Interface • Hydrodynamic Instabilities • Kelvin Helmholtz • Rayleigh Taylor • Richtmyer Meshkov • Chamber Acoustics • Baroclinic Interactions Ghosh, 2008 PhD

  5. Recent Work Ghosh, 2008 PhD

  6. Technical objectives • To better understand the physical mechanisms that play key role during the onset of combustion instability in liquid rocket engines (LRE). • What leads pressure perturbations (p’) to couple with heat release oscillations (q’) • Hydrodynamic Modes • Jet and Wake Modes • Chamber Acoustics • Heat Release • Coupling between two or more of the above • To model the relative importance of various flow-field parameters affecting flame acoustic interaction in LREs • Fuel-Oxidizer Density Ratio • Fuel-Oxidizer Velocity Ratio • Fuel-Oxidizer Momentum Ratio • Fuel composition • To build experimental database for CFD code validation Ghosh, 2008 PhD

  7. Experimental Apparatus and Techniques • Two-Dimensional Slice of Shear-Coax Injector Configuration • Turbulent Diffusion Flames • Central O2 Jet • Outer H2 Jet • Inert Wall Jet at Boundary • Transverse Acoustic Forcing • Flow Visualization • Phase-Locked OH* Chemiluminescence • Phase-Locked Schlieren/Shadowgraphy • High Speed Cinematographic Imaging • Measurement Devices • Static Pressure Sensors (Setra) • Dynamic Pressure Sensors (Kistler) • ICCD Camera (DicamPro) • Photomultiplier Tube • Hotwire • High Speed Camera Ghosh, 2008 PhD

  8. Experimental Apparatus and Techniques • Instrumentation • Signal Generator • Amplifier • Oscilloscope • LabView based VIs • Firing Sequence (Reacting Flow Cases) • H2-O2-H2 tests • O2/N2-H2-O2/N2 test • H2/Ar-O2/He-H2/Ar tests • H2/Ar/He-O2-H2/Ar/He tests • H2/CH4-O2-H2/CH4 tests Ghosh, 2008 PhD

  9. Preliminary Flame-Acoustic Interaction Tests Ghosh, 2008 PhD

  10. Acoustic Characterization using Broadband Forcing • Acoustically excited response using band-limited (< 5000Hz) white noise • Dynamic pressure • Spectral analysis using FFT (400 spectra averaged). • Non-reacting and reacting environments. Ghosh, 2008 PhD

  11. Acoustic Characterization using Broadband Forcing Ghosh, 2008 PhD

  12. Non-reacting Flow Experimental Results • Quarter-wave mode of the oxidizer post (longitudinal) • Insensitive to the density ratio • Insensitive to the sensor locations • Three-quarter-wave mode of the chamber (longitudinal) • Sensitive to the density ratio • Relatively insensitive to the sensor location • Quarter-wave mode of the chamber (transverse) • Sensitive to the density ratio • Insensitive to the sensor location f2 f1 f3 f0 f2 f1 f3 f0 Ghosh, 2008 PhD

  13. Modeling Resonance in Variable Density Flowfields • Complete Reaction Model • Consider variation in speed of sound through heterogeneous media consisting of fuel, oxidizer, and equilibrium products • Jet-Core Mixing-Length Model • Assign two different length scales in the streamwise direction -- incompletely-mixed near-field region defined by jet-core length (Ln~6D) and fully-mixed far-field region consisting of the equilibrium products • Near-field mixture fraction determined by velocity ratio • Transverse Entrainment Model • Oxidizer entrainment depends on cross-flow momentum ratio (i.e., ratio between transverse pressure force and total injection momentum) • Average mixture fraction depends on the momentum ratio Far-Field: Near-Field: Ghosh, 2008 PhD

  14. f3 T/4 f2 L/4 f1 O/4 Comparison of Isothermal Case Data • Resonance at f1 • Longitudinal first-quarter wave mode of the oxidizer post • Well predicted • Resonance at f2 • Longitudinal three-quarter wave mode of the chamber • Adequately predicted by various models • Resonance at f3 • Transverse first-quarter wave mode of the chamber • Under-predicted by complete reaction model (implies the fuel content is actually higher than the equilibrium approximation) Ghosh, 2008 PhD

  15. Acoustic Excitation of Density Stratified Non-Reacting Flows Ghosh, 2008 PhD

  16. Acoustic Excitation of Density Stratified Non-Reacting Flows - Schlieren Results for Helium Jet He (18m/s) He (18m/s) Air 6m/s Baseline ReAir (Center Jet)~ 7000 234 Hz Phase = 0o 90o 180o 270o Ghosh, 2008 PhD

  17. Acoustic Excitation of Density Stratified Non-Reacting Flows - Schlieren Results for Helium Jet He (18m/s) He (18m/s) Air 6m/s 400 Hz ReAir (Center Jet)~ 7000 625 Hz Phase = 0o 90o 180o 270o Ghosh, 2008 PhD

  18. Acoustic Excitation of Density Stratified Non-Reacting Flows - Schlieren Results for Helium Jet He (18m/s) He (18m/s) Air 6m/s 771 Hz ReAir (Center Jet)~ 7000 1094 Hz Phase = 0o 90o 180o 270o Ghosh, 2008 PhD

  19. Hydrodynamic Modes - Hot Wire Experiments • Wake Mode Instability • Jet Preferred Mode Wake Mode Frequencies F1 = 1134 Hz F2 = 756 Hz F3 = 378 Hz Jet Preferred Mode Frequencies Ghosh, 2008 PhD

  20. Hydrodynamic Modes - Hot Wire Experiments Probe Air 6m/s He 18m/s He 18m/s • Low Quality Resonant Response • f1 = 429.7 Hz, f2 = 869.4 Hz,f3=1289.3 Hz • Forced Response Closely Follows Natural Response. ReAir (Center Jet)~ 7000 Ghosh, 2008 PhD

  21. Hydrodynamic Modes– Excitation of Wake Mode He (18m/s) He (18m/s) Air 6m/s 429.7 Hz (Wake Mode Excitation) ReAir (Center Jet)~ 7000 Phase = 0o 90o 180o 270o Ghosh, 2008 PhD

  22. Reacting Flow Experiments Characteristic Flame-Acoustic Interactions H2 H2 O2 Ghosh, 2008 PhD

  23. Reacting Flow Experiments Characteristic Flame-Acoustic Interactions 300 Hz 1150 Hz Phase = 0o 90o 180o 270o Ghosh, 2008 PhD

  24. Asymmetric Excitation for the H2-O2-H2 flame Baroclinic Vorticity as a potential mechanism Ghosh, 2008 PhD

  25. Effect of Density Gradient Reversal Ghosh, 2008 PhD

  26. Effect of Density Ratio Variations • Fix velocity ratio constant at 3 and at stoichiometric H2-O2 ratio • Vary density ratio by mixing inert gas Ghosh, 2008 PhD

  27. Effect of Density Ratio Variations Instantaneous OH* Chemiluminescence(Acoustic Forcing Characteristics Held Constant at 1150Hz;12.5W) Ghosh, 2008 PhD

  28. Chapter 5 - Effect of Density Ratio Variations Ensemble Averaged OH* Chemiluminescence(Acoustic Forcing Characteristics Held Constant at 1150Hz;12.5W) Ghosh, 2008 PhD

  29. Measurements of Flame Wrinkling Amplitude • Quantifying the special extent of flame wrinkling from time-averaged OH*-chemiluminescence data Ghosh, 2008 PhD

  30. Effect of Density Gradient on Flame-Acoustic Interaction • Time-Averaged Measurement of Flame Wrinkling Thickness • Fixed OH Ratio, Velocity Ratio, Acoustic Forcing Amplitude • Variable Density by Ar or He Dilution Ghosh, 2008 PhD

  31. Effect of Heat Release Variations • Use noble gas to dilute fuel and oxidizer streams while keeping the velocities constant • Gradual change in heat release with dilution • O2/He and H2/Ar combination • Exponential change in density ratio • Ideal for isolating the density effect • O2/Ar and H2/He combination • Little change in density ratio • Ideal for studying the effect on chemistry Ghosh, 2008 PhD

  32. Effect of Heat Release VariationsUnder Constant Forcing, Constant Heat Release, Different Density Ratios • Acoustically Forced • Heat Release: 15 kW • 6% Dilution by Mole • Density Ratio: 7.0 (left) and 15.2 (right) • Unforced • Heat Release: 15 kW • 6% Dilution by Mole • Density Ratio: 7.0 or 15.2 Ghosh, 2008 PhD

  33. Effect of Jet Momentum Variations • Use noble gas to dilute fuel and oxidizer streams while keeping the velocities constant • Exponential change in Density Ratio with dilution • O2/He and H2/Ar combination • Exponential change in density ratio • Linear increase in outer jet momentum • Linear Increase in total jet momentum Ghosh, 2008 PhD

  34. Effect of Jet Momentum VariationsAcoustic Excitation – 1150 Hz, 15.8 Watts • Case 1 • Outer Jet Momentum :0.0055 kg.m/s2 • Inner Jet Momentum : 0.0047 kg.m/s2 • Density Ratio: 8 • Case 2 • Outer Jet Momentum :0.0055 kg.m/s2 • Inner Jet Momentum : 0.0036 kg.m/s2 • Density Ratio: 2 Ghosh, 2008 PhD

  35. Rayleigh Taylor Growth Rate • Richtmyer-Meshkov Instability • Rayleigh-Taylor Instability g Rayleigh-Taylor Instability Youngs (1984) Richtmyer-Meshkov Instability Sunhara et al. (1996) Ghosh, 2008 PhD

  36. Rayleigh Taylor Growth Rate • Classical Rayleigh-Taylor mode instability analysis yields wavelength-dependent growth rate • Intermittent fluid acceleration by pressure waves is used instead of gravitational acceleration Ghosh, 2008 PhD

  37. Parametric Studies. Dimensional Analysis for the Shear-Coax Injector Problem δ(x)=|ro- ri |, where I(x,r) satisfies Imax(x)-I(x,ro)=Imax(x)-I(x,ri)=0.9[Imax(x)-Ibackground(x)] Ghosh, 2008 PhD

  38. Parametric Studies. Effect of Density Ratio • Time-Averaged Measurement of Flame Wrinkling Thickness • Fixed OH Ratio, Velocity Ratio, Acoustic Forcing Amplitude • Variable Density by Ar or He Dilution Ghosh, 2008 PhD

  39. Parametric Studies. Effect of Velocity Ratio. Ghosh, 2008 PhD

  40. Parametric Studies. Effect of Velocity Ratio • OH* Chemiluminescence Imaging • Uf/Uo : 3.02, 3.36, 3.64, 4.01,4.51, 5.03, 5.27 • Density Ratio: 8 Ghosh, 2008 PhD

  41. Parametric Studies. Effect of Velocity Ratio • Time-Averaged Measurement of Flame Wrinkling Thickness • Fixed OH Ratio, Density Ratio, Acoustic Forcing Amplitude • Variable Velocity Ratio by He Addition to outer Jet Ghosh, 2008 PhD

  42. Parametric Studies. Effect of Momentum Change Ghosh, 2008 PhD

  43. Parametric Studies. Effect of Momentum Change • Case A • Case B Increase in Outer Jet Momentum Velocities fixed (Velocity Ratio ~ 3) Decrease in Oxidizer Fuel Density Ratio (6 - 2) Increase in Outer Jet Momentum Densities Fixed (Density Ratio ~ 8) Increase in Fuel Oxidizer Velocity Ratio (3 - 5.3) Ghosh, 2008 PhD

  44. Parametric Studies. Effect of Momentum Change • Case A • Fixed Densities • Outer Jet Velocity is Increased • Case B • Fixed Velocities • Density Ratio is Decreased Ghosh, 2008 PhD

  45. Parametric Studies. Effect of Chemical Composition. Ghosh, 2008 PhD

  46. Parametric Studies. Effect of Chemical Composition Lifted flame using only methane as fuel (a) OH* average (b) CH* average (c) OH* instantaneous (d) CH* instantaneous 50% methane and 50% hydrogen flame subjected to acoustic excitation. (a) OH* average (b) CH* average (c) OH* instantaneous (d) CH* instantaneous Ghosh, 2008 PhD

  47. Parametric Studies. Effect of Chemical Composition. • Time-Averaged Measurement of Flame Wrinkling Thickness • Fixed Density Ratio ~ 6 • Fixed Velocity Ratio ~ 3 • Fuel Composition is varied. Ghosh, 2008 PhD

  48. Chapter 5- Parametric Studies .Dependence of Flame-Acoustic Interactionon Density Ratio, Velocity Ratio, HC Mole Fraction Fuel mixture ratio (methane mole fraction) Density ratio Velocity ratio y = 0.022 exp(5.1 x) y = -3.5 x + 3.6 y = -0.87 x + 2.3 Ghosh, 2008 PhD

  49. Pressure Oscillation OH* Oscillation Simultaneous Measurement of Pressure and Heat Release Oscillations Density Ratio = 14.5 Density Ratio = 3 Ghosh, 2008 PhD

  50. OH* Chemiluminescence Oscillations • Photomultiplier Measurements • Forcing Frequency = 1150 Hz f = 1150 Hz Ghosh, 2008 PhD

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