DEVELOPMENT OF POROUS INJECTION TECHNOLOGY TO REDUCE EMISSIONS FOR DRY LOW NOx COMBUSTORS: MICROMIXER SWIRL INJECTORS

摘要

The Combustion and Fire Research Laboratory (CFRL) at the University of Cincinnati (UC) is working on the development of advanced next generation injectors for DLN combustors. Several inputs were received from the project partners during the development phase. In the present paper, developmental work on two novel injectors with Porous Injection Technology (PIT) is presented. The technology has the potential to reduce NO_x emissions to single digit PPM level with a stable combustion across wide range of load conditions. One of the key factors that are essential for lowering NOx levels is the efficient mixing of fuel-air in both spatial and temporal domains. The porous injection technology has the potential to reduce the spatial and temporal gradients to a minimum. In the present paper, two measurement techniques were used to evaluate the fuel-air mixing under atmospheric conditions. The CO_2 mixing technique was used to quantify the spatial variations in the fuel mass fraction. Planar Laser Induced Fluorescence (PLIF) was used to obtain both spatial and temporal fuel mass fractions. The CO_2 mixing measurements were used to validate the PLIF data for quantification. The RMS fluctuations in spatial and temporal domains were quantified from PLIF data. The combustion experiments were carried out at atmospheric pressure with a preheated temperature of air of 500-650 K and equivalence ratio of 0.5-0.8. The pressure drop across the injector was 4%. Natural gas with 90% methane and 9% ethane was used as fuel. The results show a stable flame for both injectors without combustion instabilities. Both injectors show low NO_x levels. For conventional swirl stabilized design with PIT, the NO_x levels were of the order of 1.5 ppm at the firing temperature of 1866 K whereas for the novel micromixer design, the NOx levels were of the order of 4 ppm @ ~1866 K.