A chemical kinetic and numerical study of nitrogen oxides and pollutant formation in low-emission combustion

The NO{dollar}rmsb{lcub}x{rcub}{dollar} formation process in lean premixed gas-fired combustion turbines is examined as a function of the primary combustion variables (flame temperature, inlet mixture temperature, pressure, and residence time). The effects of these variables are examined using chemical reactor and laminar one-dimensional computational models.; The flame temperature is determined to be the primary variable affecting the NO{dollar}rmsb{lcub}x{rcub}{dollar} formation process. The apparent activation energies of NO{dollar}rmsb{lcub}x{rcub}{dollar} formation for the 1700 to 1900K range are found to vary from 48.8 to 90.5kcal/gmol, depending on the chemical kinetic mechanism used, the reactor residence time, and the pressure.; For a fixed flame zone residence time and a fixed flame temperature, an increase in the inlet mixture temperature is found to produce an increase in NO{dollar}rmsb{lcub}x{rcub}{dollar} emissions. Increases in flame zone residence time are likewise found to result in increased NO{dollar}rmsb{lcub}x{rcub}{dollar} emissions.; The sensitivity of NO{dollar}rmsb{lcub}x{rcub}{dollar} formation to pressure is found to be strongly influenced by the flame temperature. At a flame temperature of 1700K, there is a neutral or slightly negative NO{dollar}rmsb{lcub}x{rcub}{dollar} pressure sensitivity. However, at a flame temperature of 1900K, the NO{dollar}rmsb{lcub}x{rcub}{dollar} pressure sensitivity is strongly dependent on flame zone residence time and on the chemical kinetic mechanism used.; In order to permit numerical models to predict NO{dollar}rmsb{lcub}x{rcub}{dollar} emissions for practical combustors, a chemical mechanism reduction procedure, and pre- and post-processors for use with CFD codes are developed.; Reduced chemical mechanisms are developed and presented for lean, (0.4 {dollar}leqphileq{dollar} 0.8), high pressure combustion, and for atmospheric pressure combustion over the fuel-air equivalence ratio ranges of 0.4 {dollar}leqphileq{dollar} 0.8, and 1.2 {dollar}leqphileq{dollar} 1.6.; The pre-processor global mechanism "fine-tuning" procedure is developed and applied to cases of lean premixed combustion at atmospheric and representative gas turbine operating pressures.; The post-processor allows for NO{dollar}rmsb{lcub}x{rcub}{dollar} emission prediction from global mechanisms by linking local NO{dollar}rmsb{lcub}x{rcub}{dollar} formation rates to CO concentrations, a method developed under this research.