Fuel flexible distributed combustion for efficient and clean gas turbine engines

Abstract

The need for fuel flexible ultra-low emission gas turbine combustors is imminent to secure future power needs. Distributed combustion technology is demonstrated to provide significant performance improvement of gas turbine combustors including uniform thermal field in the entire combustion chamber (improved pattern factor) at very high combustion intensity, ultra-low emission of NOx and CO, low noise, enhanced stability, higher efficiency and alleviation of combustion instability. Distributed reaction conditions were achieved using swirl for desirable controlled mixing between the injected air, fuel and hot reactive gases from within the combustor prior to mixture ignition. In this paper, distributed combustion is further investigated using a variety of fuels. Gaseous (methane, diluted methane, hydrogen enriched methane and propane) and liquid fuels, including both traditional (kerosene) and alternate fuels (ethanol) that cover a wide range of calorific values are investigated with emphasis on pollutants emission and combustor performance with each fuel. For liquid fuels, no atomization or spray device was used. Performance evaluation with the different fuels was established to outline the flexibility of the combustor using a wide range of fuels of different composition, phase and calorific value with specific focus on ultra-low pollutants emission. Results obtained on pollutants emission and OH* chemiluminescence for the specific fuels at various equivalence ratios are presented. Near distributed combustion conditions with less than 8PPM of NO emission were demonstrated under novel premixed conditions for the various fuels tested at heat (energy) release intensity (HRI) of 27MW/m3-atm. and a rather high equivalence ratio of 0.6. Higher equivalence ratios lacked favorable distributed combustion conditions. For the same conditions, CO emission varied for each fuel; less than 10ppm were demonstrated for methane based fuels, while heavier liquid fuels provided less than 40ppm CO emissions. Lower emissions of NO (<4.5PPM) were also demonstrated at lower equivalence ratios. This demonstration outlines the combustor ability for fuel flexibility without any modifications to the combustor injectors, while maintaining high performance. Further reduction of NOx can be possible by establishing true distributed combustion condition, in particular at higher equivalence ratios.