Mulvihill, Clayton Reed (2019-08). H2O LASER ABSORPTION AND OH* CHEMILUMINESCENCE MEASUREMENTS OF H2-NO2 OXIDATION IN A SHOCK TUBE. Doctoral Dissertation. Thesis uri icon

abstract

  • The mitigation of NOx pollutants continues to be a matter of environmental and economic interest in the gas-turbine industry, and an improved understanding of fundamental NOx chemical kinetics has led to reductions in NOx emissions. However, the exhaust gas recirculation (EGR) method necessitates an accurate understanding of NOx/fuel interactions, and few experimental data with NOx as the sole oxidizer exist. New measurements of this kind would provide unique target data for the continuing design and optimization of NOx chemical kinetics mechanisms. To this end, new combustion data in the H2-NOv2 system were acquired. Experiments were performed behind reflected shock waves near 1 atm and at temperatures between 917 and 2003 K. Fuel-lean, near-stoichiometric, and fuel-rich mixtures of H2-NOv2 diluted in approximately 99 percent Ar were studied. A laser absorption diagnostic near 1.39 um measured H2O time histories, while an emission diagnostic near 307 nm measured exited-state OH (OH asterisk) time histories. Kinetic modeling of the H2O data revealed the species HONO and NO3 are important in the H2vO reaction pathways. Newer mechanisms predicted the experimental H2O profiles quite well at fuel-lean and high-temperature conditions, but discrepancies persisted at fuel-rich and low-temperature conditions despite variation of the most-sensitive reactions. The kinetic models were unable to predict the experimental OH asterisk profile shapes with any sort of accuracy, suggesting the need for a new OH asterisk-forming reaction. By fitting the OH* profile shapes and considering exothermicity, the reaction NH + NOv2 ? N2vO + OH asterisk was identified, and a tentative rate constant of kv13 = 5.0x10^^16?exp(- 40,000/RT) was proposed (units of [cal], [mol], [cm^3 ], [s]).

publication date

  • August 2019