Analysis of Liquid Fuel Effect on Swirl-Assisted Jet-Stabilized Combustor Performance

Abstract Growing interest in reducing pollutant emissions from gas turbines is driving efforts to develop combustor system solutions with low NOx, CO and UHC emissions while maintaining a wide range of performance and fuel flexibility. The paper describes an investigation of the spray produced by flash boiling mechanism (superheated injection) and mechanical liquid bulk breakup (pressure-swirl atomization) in a lean premixed swirl-assisted jet-stabilized combustion system. Fuel vaporization prior to combustor inlet is greatly enhanced by the combustor design and elevated liquid fuel temperature. A comprehensive analysis of combustion behavior for a range of fuels in both liquid and superheated regimes has been performed. The fuel atomization is based on the mechanical and thermal breakup of the liquid fuel in a temperature range of 150–300°C. Variable thermophysical properties of four different liquid fuels from various origins are investigated under atmospheric conditions. OH* chemiluminescence and Mie scattering have been used as optical and laser diagnostic methods. These measurement techniques were used to analyze the combustion behavior and spray breakup mechanism. A mixing condensation particle counter (MCPC) was used to determine the particulate emissions of the various liquid fuels and spray generation techniques. Measurement of exhaust gas emission levels of NOx, CO and UHC are conducted simultaneously for each operating point. The underlying factor effects are presented and discussed. The results indicate that while NOx and CO emissions are not majorly affected by the fuel atomization technique, the thermophysical properties of the fuel, such as the saturation temperature, play an important role in the fuel atomization process and to a minor degree on the emitted NOx and CO emissions. Furthermore, it is shown that, except for differences in spray penetration length and evaporation quality, the combustion performance was similar in terms of flame operating range for all tested liquid fuels. The effect of different fuel atomization techniques on particulate emissions was minimal. However, due to their origins, the different fuels had large variations in the particulate matter measurements.