Effects of fuel structure on emissions and stability in the well-stirred reactor

The design and development of low-emissions aero and industrial gas turbine combustors is challenging because it entails satisfying emissions regulations without conflicting with performance improvements. Efforts to reduce emissions have typically ignored the variability in emissions that can result from change in fuel type. Consequently, it is desirable to investigate fuel effects on emissions and performance characteristics of the combustor under realistic operating conditions. The well stirred reactor (WSR) is a laboratory combustor with two uses: (a) it provides a laboratory idealization of a highly mixed gas turbine combustor; (b) it emulates the perfectly stirred reactor condition for use in measuring kinetics parameters and data to compare to kinetics models of gas turbine fuels.; The WSR was used to study lean blow-out limits and emissions from a variety of fuels. In particular, effects of residence time and flame temperature on lean blow-out limits, NO{dollar}sb{lcub}rm x{rcub}{dollar}, CO, and unburned hydrocarbon (UHC) emissions were measured from normal and cyclic alkanes, aromatics and hydrocarbon mixes. It was found that CO and UHC emissions increase with increasing carbon number of the fuel, with methane being an exception. NO{dollar}sb{lcub}rm x{rcub}{dollar} emissions increase with increasing carbon to hydrogen ratio of the fuel. Results showed that hydrocarbon structure plays a significant role in determining lean blow-out limits, combustion efficiency, and pollutant emissions. From this study, the global activation energies of methane and ethane were measured during lean combustion. Also, empirical formulae to predict NO{dollar}sb{lcub}rm x{rcub}{dollar} formation and minimal production of CO as a function of fuel characteristics are given.; Emissions data from the WSR were compared to simulations by detailed kinetic modeling of the combustion of methane, ethane, n-heptane, toluene, ethylbenzene, Jet A and cracked fuel simulant. Computations are generally in excellent qualitative agreement with experimental observation for all fuels without relying on ad hoc adjustments to kinetic rate parameters.; In addition, the WSR was used to measure products of the decomposition of halon, the sooting limits from several fuels and aerosol production during lean and rich combustion. These experiments show the versatility of the WSR in studies of chemical systems other than the gas turbine combustor.