Comparative analysis of combustion, thermodynamic and environmental performance of hydrogen-doping X-type rotary engines using single-ignitor and dual-ignitors under high-altitude condition

In this paper, a novel hydrogen-doping X-type rotary engine (XRE) using dual-ignitors is proposed to improve its high-altitude performance. Firstly, the effects of hydrogen doping fraction and operation altitude on the combustion, thermodynamic and environmental performance of XRE are revealed by establishing CFD model. Furthermore, the novel dual-ignition strategy using different ignition intervals is raised based on the eddy distribution characteristics. Finally, the comprehensive performance of the dual-ignition strategies is analyzed by comparing with the traditional single-ignition strategy under high-altitude conditions. The results show that the thermal efficiency increases firstly and then drops with the increasing hydrogen doping fraction. When hydrogen doping fraction increase by 6 %, the NO_x emission increases by 2.9 times at 0 km altitude, while it increases by 4.2 times at 6 km altitude. Auxiliary ignitor arranged at back side can generate backward flame and promote combustion. At 0 km altitude, the thermal efficiency of dual-ignition reaches the maximum of 0.330, which is 3.12 % higher than that of single-ignition. However, the synchronous dual-ignition is the best strategy at high-altitude, in which the thermal efficiency is improved by 2.59 % and CO₂ emission is reduced by 3.99 % compared with the asynchronous ignition using an interval of 10 °EA.