Investigation of high-tumble chamber of ammonia-hydrogen fueled elliptical rotary engine based on turbulence and combustion characteristics

The ammonia-hydrogen dual-fuel elliptical rotary engine (AH-ERE) is a promising novel power system within the low-carbon context. To enhance the combustion and emission performances of AH-ERE, this paper investigates the optimized high-tumble chamber arrangement from both aspects of cylinder configuration (front configuration FC, middle configuration MC, and rear configuration RC) and hydrogen injection angle (HIA = 0°, 45°, and 60°). On this basis, the characteristics of the flow field and mixture distribution under different operating conditions are compared from the perspective of in-cylinder swirl and tumble flow emphatically. Finally, the improvement of combustion, power and emission performance by cylinder configuration and HIA is analyzed. The results indicate that under MC-A60 condition, the hydrogen jet tends to accumulate inside the external chamber due to the effect of wall blocking and high tumble ratio. This phenomenon significantly promotes the flame propagation, resulting in the highest indicated power of 11.30 kW and NO_x emission of 41.07 ppm. As the HIA decreases to 45°, the dispersed combustion caused by long hydrogen penetration distance and high TKE leads to a 55.10 % reduction in NO_x, at a slight expense of power performance. In comparison, the RC cylinder has more uniform hydrogen distribution and significant clockwise tumble. The RC-A30 condition can reduce NO_x emission to 20.09 % of MC-A60 condition while maintaining the indicated power of 10.87 kW, performing better in terms of emission performance.