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The H + O2 + M yields HO2 + M reaction was investigated at temperatures between 1050-1250 K and pressures from 7 to 152 bar behind reflected shock waves in gas mixtures of H2, 02, NO, and bath gases of Ar, N2, and H2O. Narrow linewidth laser absorption of NO2 at 472.7 nm was used to measure quasi-steady NO2 concentration plateaus in experiments designed to be sensitive only to the H + 02 + M yields HO2 + M and the relatively well-known H + NO2 yields NO + OH and H + 02 yields OH + 0 reaction rates. The pressure dependence of the reaction was studied by measuring the fall-off of the reaction for M = Ar over a 10-152 bar pressure range. A simple modified Hindered-Gorin model of the transition state is used in an RRKM analysis of the results to facilitate comparisons of this work with measurements from other researchers at lower pressures. The RRKM calculations can also be described, using the simple functional form suggested by Troe, with the following: k(sub infinity)/cu cm molecule(exp -1)s(exp -1) = 4.7x10(exp -11)(T/300)(exp .02); k(sub 0)(Ar)/cm(exp 6) molecule(exp -2)s(exp -1) = 2.0x10(exp -32)(T/300)(exp -1.2); k(sub 0)(N2)/cm(exp 6) molecule(exp -2)s(exp -1) = 4.4 x 10(exp -32)(T/300)(exp -1.3); k(sub 0)(H2O)/cm(exp 6) molecule(exp -2)s(exp-1) = 3.4 x 10(exp -31)(T/300)(exp -1.0); F(sub c) = 0.7 for Ar and N2 and 0.8 for H20. Measured values of the reaction rate for M = Ar in the highest pressure experiments fall below both simple RRKM analysis and the more sophisticated treatment of Troe using an ab initio potential energy surface. Collision efficiencies of N2 and H20 relative to Ar at 1200K are 3.3 and 20 respectively., Prepared in collaboration with High Temperature Gasdynamics Laboratory, Department of Mechanical Engineering, Stanford University, CA.

The effectiveness of selective non-catalytic (SNCR) gas-phase reaction processes for NO(x) removal from combustion products at elevated pressures was investigated in a combined experimental and modeling research program. Calculations using existing chemical models for SNCR indicate that the temperature window for NO(x) removal by SNCR widens as pressure increases, resulting in NO(x) removal at higher temperatures than at ambient pressure. The calculations also show a significant reduction in the reaction time scale with increasing pressure. These observations suggest the possibility of utilizing SNCR for reducing NO(x) emissions from marine gas turbines and Diesel engines by direct injection of a reductant species into the combustion chamber, possibly as a fuel additive. Initial experiments were carried out at atmospheric pressure to allow comparison with previous measurements in order to verify the experimental approach. Following these validation tests, experiments were conducted at elevated pressures. Results from these tests, confirm the model predictions that the SNCR window for NO(x) removal widens as the pressure increases. In addition, a project was initiated, to develop compact, robust, solid-state microsensors for pollutant species for use in control systems for reduction of pollutant emissions. The sensor concept is based on integrated circuit fabrication technology that allows the integration of a metal-oxide sensor with associated electronic circuitry on a single chip. Initial efforts focused on development of a sensor for NO(x).

This project is directed toward obtaining a more fundamental understanding of mixing and chemical reaction in supersonic flows. The research effort comprises three inter-related elements: (1) an experimental study of mixing and combustion in a supersonic plane mixing layer; (2) development of laser-based diagnostics for high-speed flows; and, (3) simulations of compressible reacting flows. (MM)