1. Studies of High-Pressure Acoustic Combustion Instabilities in Hydrocarbon-Oxygen Liquid-Propellant Rocket Engines Based on Reduced Chemical-Kinetic Mechanisms A. L. Sánchez, F.A. Williams, Mechanical and Aerospace Engineering, UCSD C.K. Law, Mechanical and Aerospace Engineering, Princeton University
Project Goal: Advance fundamental knowledge pertaining to the interplay of the acoustic field with the reactive flow in hydrocarbon-fueled liquid-propellant rocket engines, enabling the development of advanced modeling tools for predicting the instability behavior in realistic scenarios.
Technical Approach: Combination of experimental measurements of methane-oxygen systems with numerical and modeling efforts
Improvement of high-pressure oxidation kinetics and development of reduced chemistry descriptions
Investigation of acoustic pressure response in elementary laminar flamelets
Development of extended experimental data base
Advanced flamelet models

2. Discoveries and Impact:
Studies of High-Pressure Acoustic Combustion Instabilities in Hydrocarbon-Oxygen Liquid-Propellant Rocket Engines Based on Reduced Chemical-Kinetic Mechanisms A. L. Sánchez, F.A. Williams, Mechanical and Aerospace Engineering, UCSD C.K. Law, Mechanical and Aerospace Engineering, Princeton University
Variation with acoustic frequency of the Rayleigh index as computed with one-step kinetics for different Damkohler numbers
Discoveries and Impact:
Preliminary evaluation of acoustic pressure response of strained flamelets with one-step model chemistry suggests that finite-rate effects are dominant near extinction, and that direct unsteady modifications to the outer chemical-equilibrium transport regions produce only moderate effects.
Systematic identification of the inaccuracies associated with the use of ideal gas assumptions (EoS, thermodynamics, transport) and chemical kinetics in supercritical fluids. Use of newly evaluated rate coefficients of selected key reactions leads to significant modifications of the burning rates of methane flames.
Laminar flame speeds of methane flames with different supercritical physical & chemical models

3. Studies of High-Pressure Acoustic Combustion Instabilities in Hydrocarbon-Oxygen Liquid-Propellant Rocket Engines Based on Reduced Chemical-Kinetic Mechanisms A. L. Sánchez, F.A. Williams, Mechanical and Aerospace Engineering, UCSD C.K. Law, Mechanical and Aerospace Engineering, Princeton University
Potential Transition to Air Force/DOD Needs:
New directions for modeling studies in predicting the occurrence of combustion instabilities in liquid-propellant rockets.
Emphasis that subgrid-scale modeling for LES of liquid-propellant rocket instability needs to consider proper chemical kinetics, systematically reduced from correct detailed chemistry, to achieve reliable predictions severity to be expected.
Development of inputs required for improving the basis of high-fidelity computation of combustion instabilities in turbulent reacting flows involved in CH4/LOX rocket motors.
For supercritical, rocket-relevant, non-ideal conditions, need to use appropriate EoS, thermodynamics, transport properties, and rate parameters of selected reactions.
Re-evaluated reaction rates serve as initial building blocks for the development of comprehensive supercritical reaction mechanisms.
Ultimately achieving more well-founded propulsion designs for liquid-propellant rocket motors.