Investigation of the effects of swirler blade angle and micro-mixing hole diameter on performance and NOx emissions in hydrogen-fueled recirculation combustor

Abstract

Abstract This study presents a three-dimensional numerical simulation investigation into two distinct swirl configurations (axial and radial) of hydrogen fuel recirculation combustor under a lean equivalence ratio of 0.3, focusing on the effects of swirler blade angle and micro-mixing hole diameter on combustion performance and pollutant emissions. The results demonstrate that: swirler blade angle significantly influences combustion efficiency, total pressure recovery coefficient, and NOx formation. For axial swirlers, the combustion efficiency peaks at 99.92 % when the blade angle is 30°, while the total pressure recovery coefficient decreases from 98.61 % to 97.26 %. The Emission Index (EI) exhibits an approximately linear increase with increasing blade angles. For radial swirlers, combustion efficiency rises from 99.56 % to 99.90 % as the blade angle increases from 30° to 60°, while the total pressure recovery coefficient drops from 98.68 % to 97.55 %. Temperature distribution factors (OTDF/RTDF) decrease continuously, and EI shows nonlinear growth. Micro-mixing hole diameter has a minimal impact on the total pressure recovery coefficient and temperature distribution metrics but significantly affects combustion efficiency. For axial swirlers, combustion efficiency reaches its maximum at 0.8 mm hole diameter, with negligible changes in total pressure recovery (<1 %) and temperature distribution coefficients. The EI index exhibits nonlinear growth. For radial swirlers, combustion efficiency peaks at 99.90 % when the micro-mixing hole diameter is 0.8 mm, with near-constant total pressure recovery and insignificant variations in OTDF/RTDF. The EI index shows nearly linear growth under these conditions.