["A RAPID COMPRESSION MACHINE DESIGN, CHARACTERIZATION, AND AUTOIGNITION INVESTIGATIONS"]

["A rapid compression machine (RCM) has been designed for the purpose of chemical kinetics studies at elevated pressures and temperatures. The present RCM is designed as a versatile tool and includes the features of a well-defined core region, fast compression, ability to vary stroke and clearance, optical accessibility, and capability for specie measurement. The machine is pneumatically driven and hydraulically actuated and stopped. Characterization experiments establish the suitability of the machine for chemical kinetic studies and show that highly repeatable experimental conditions up to 50 bar and greater than 1000 K can be obtained. A numerical model accounting for compression and heat loss is also developed to simulate the RCM experiments. Experimental and computational investigations of aerodynamics inside the machine by using planar laser induced fluorescence of acetone and Star-CD CFD package substantiate the importance of piston head design for achieving a homogeneous core region inside a rapid compression machine. Results show that the flat piston head design leads to significant mixing of cold vortex with hot core region, eventually leading to the failure of adiabatic core assumption. Whereas, creviced piston head configuration is demonstrated to result in drastic reduction of the effect of vortex, and adiabatic core assumption is found to be valid for long time after compression. Using this facility, autoignition investigations are conducted for iso-octane, H2, and H2/CO system. Iso-octane autoignition is investigated at pressures up to 22 bar, and temperature from 680 K to 880 K. Whereas H2, and H2/CO systems are investigated at pressures from 15 to 50 bar, and temperatures from 950 K to 1100 K. Comparisons of experimental results with numerical predictions of detailed mechanisms show that existing mechanisms fail to predict the behavior of these systems. Particularly, for isooctane ignition significant differences in simulated and experimental results are noted for experimental conditions in the NTC regime. For H2/CO system, the existing mechanisms fail to describe the inhibition effect of CO addition on H2. Kinetic analysis is shown to further identify the controlling reaction steps, which require modification of rate constant. Further investigation of these systems over a wide range of physical conditions is warranted."]