Investigation into the influence of combustion system based upon tumble flow on engine performance of opposed-piston two-stroke engine

The Opposed Piston Two-Stroke (OP2S) engine, with its potential for high thermal efficiency and low emissions, offers a promising pathway for the sustainable development of future energy systems. However, due to the unique combustion system of the OP2S engine and the increasing cylinder bore size aimed at achieving high power and torque, relying solely on swirl flows is insufficient to achieve ideal fuel utilization. To address this issue, this paper quantitatively analyzes the impact of different combustion chamber shapes and their key parameters on in-cylinder flow fields and Indicated Mean Effective Pressure (IMEP) through simulation calculations. Additionally, the spray and combustion processes under five nozzle configurations combined with tumble flow fields are investigated. The results indicate that controlling the combustion chamber shape can effectively regulate and enhance the tumble flow. The optimized tumble flow, combined with swirl flows, promotes rapid spray dispersion and breakup, thereby improving fuel utilization efficiency. Moreover, co-directional motion between the spray and tumble flow achieves a higher heat release rate throughout the combustion phase, leading to increased IMEP. Finally, the optimally case demonstrates a 7.34% increase in total heat release and a 9.72% improvement in IMEP compared to the baseline.