Reduced kinetics mechanisms for ram accelerator combustion

Two skeletal kinetics mechanisms for reactive CH4/O-2 and H-2/O-2 ram accel erator flowfields are presented. Both models were derived from a 190-reacti on, 38-species kinetics mechanism (RAMEC or RAM accelerator MEChanism) that successfully reproduces the high pressure (>50 atm), low dilution (110%), fuel-rich chemistry of ram accelerator mixtures. The reduction procedure fo r the CH4/O-2 mechanism utilized a detailed reduction technique with igniti on delay time and heat release as the selection criteria. The methane-based mechanism (REDRAM or REDuced RAM accelerator mechanism) contains 34 reacti ons and 22 species and predicts ignition times to better than 5% and postco mbustion temperatures to within 10 K of the full mechanism for a representa tive range of ram accelerator mixtures and conditions. This CH4/O-2 mechani sm is an improvement over existing reduced methane-oxidation mechanisms tha t are based on lower-pressure, higher-temperature chemistry, An 18-step, 9- species mechanism is presented for hydrogen based ram accelerator combustio n that is based on the H-2/O-2 submechanism of the RAMEC/Gas Research Insti tute GRI-Mech 1.2 methane oxidation mechanism, The H-2/O-2 kinetics model i ncludes HO2 and H2O2 chemistry 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.