| A new shock tube facility, designed to achieve reflected-shock pressures as high as 1000 atm, was installed in the High Temperature Gasdynamics Laboratory in the summer of 1994. The higher pressures within the shock tube result in increased viscous effects, heat transfer, and turbulence, leading to uncertainty in the test temperature and making optical measurements difficult to perform. Using a combination of CO-emission and pressure measurements, the nonideal temperature and density behind reflected shock waves in argon were characterized at elevated pressures. A theoretical model, based on existing shock tube boundary layer theory, an improved friction model, and the method of characteristics, was developed that agrees well with the experimental data. The nonidealities can be accounted for using the theoretical model and/or measurements of the pressure via an isentropic assumption.; For the application of laser absorption and infrared emission diagnostics, the elevated pressures within the High Pressure Shock Tube lead to stress-induced anisotropy of the windows, large index of refraction perturbations due to increased turbulence, and background radiation from the enhanced heat transfer. Various techniques for minimizing the resulting uncertainties in the measured light intensity are proposed. Ignition delay time experiments were conducted with CH{dollar}sb4{dollar}/O{dollar}sb2{dollar}/Diluent mixtures at pressures from 20 to 260 atm, low dilution levels (fuel plus oxidizer {dollar}ge{dollar}30%), intermediate temperatures (1040-1500 K), and F/O equivalence ratios as high as 6. The ignition delay times were found to be independent of the concentration and type of diluent (Ar, N{dollar}sb2{dollar}, He) and exhibited an unexpected acceleration at the highest pressures and lowest temperatures. A 38-species, 190-reaction kinetics model was developed from the GRI-Mech 1.2 detailed mechanism using additional reactions and species important in methane oxidation at intermediate temperatures. The resulting calculations agree well with the measured ignition delay times and reproduce the trends seen in the data at higher pressures and lower temperatures. In general, reactions involving HO{dollar}sb2{dollar}, CH{dollar}sb3{dollar}O{dollar}sb2{dollar}, and H{dollar}sb2{dollar}O{dollar}sb2{dollar} have increased importance at the conditions of this work relative to previous studies at lower pressures and higher temperatures. |
