Reduction of nitrogen oxides emission for lean prevaporized-premixed combustors

The purpose of this research is to examine the formation and to determine the means of prevention of NO_x emission in lean prevaporized-premixed (LPP) combustion for application to gas turbine engines. The focus of this study is twofold: (1) examination of the effects of prevaporizer-premixer design and operation on NO_x formation and (2) examination of the effects of fuel type on NO_x formation.; Three generations of prevaporizing-premixing injector technology are used, beginning with very simple single stage prevaporizing-premixing injectors and continuing through to a staged prevaporizer-premixer (this is termed the SPP) of advanced design for which a patent has been applied. Parametric analysis conducted includes the effects of inlet temperature, injection pattern, degree of premixing and, of particular interest, fuel type.; The developmental history of the prevaporizing-premixing injectors used is discussed. A detailed review of the experimental results obtained for the SPP injector is presented. The research focuses on the full characterization of the SPP and the jet-stirred reactor (JSR) fed by the SPP. Effects including stage inlet temperature split, stage airflow split, stage residence time split and fuel variation are investigated to characterize the SPP and the NO _x formation in the JSR. A laser absorption technique is employed to quantify the degree of premixing at the SPP outlet. Additionally, a separate multi-sampling port jet-stirred reactor is tested to provide detailed information on the temperature distribution within the JSR. Several chemical kinetic mechanisms are tested in conjunction with simple chemical reactor models (CRMs) of the JSR to enhance the understanding of the various NO_x formation mechanisms. A large hydrocarbon oxidation mechanism with pollutant formation chemistry is studied to enhance the understanding of the liquid fuel oxidation and NO_x formation processes.; The results show that complete vaporization of both pure and multi-component, commercial fuels is obtained with the SPP and that the premixing is nearly perfect. With the JSR fed by the SPP, the formation of NO_x from commercial liquid fuels, such as No. 2 diesel fuel, is within a factor two of the NO_x emission from natural gas. That is, the NO_x emission from liquid fuel firing is not significantly increased as is typically found with other injectors used in LPP combustion systems.