Reduced Kinetics Mechanisms for Ram Accelerator Combustion
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Two skeletal kinetics mechanisms for reactive CH4/O2and H2/O2ram accelerator flowfields are presented. Both models were derived from a 190-reaction, 38-species kinetics mechanism (RAMEC or RAM accelerator MEChanism) that successfully reproduces the high-pressure (>50 atm), low-dilution (<70%), fuel-rich chemistry of ram accelerator mixtures. The reduction procedure for the CH4/O2mechanism utilized a detailed-reduction technique with ignition delay time and heat release as the selection criteria. The methane-based mechanism (REDRAM or REDuced RAM accelerator mechanism) contains 34 reactions and 22 species and predicts ignition times to better than 5% and postcombustion temperatures to within 10 K of the full mechanism for a representative range of ram accelerator mixtures and conditions. This CH4/O2mechanism is an improvement over existing reduced methane-oxidation mechanisms that are based on lower-pressure, higher-temperature chemistry. An 18-step, 9-species mechanism is presented for hydrogen-based ram accelerator combustion that is based on the H2/O2submechanism of the RAMEC/Gas Research Institute GRI-Mech 1.2 methane-oxidation mechanism. The H2/O2kinetics model includes HO2and H2O2chemistry near the second and third explosion limits, necessary for ignition at ram accelerator pressures but lacking in certain finite rate chemistry models currently in use.
author list (cited authors)
Petersen, E. L., & Hanson, R. K.