Effect of ignition pattern on combustion characteristics in a hydrogen Wankel rotary engine: A numerical study

Hydrogen is considered the optimal solution for achieving high efficiency and low emissions in Wankel rotary engines (WREs). This paper aims to reveal the effect of ignition patterns on the combustion process of a hydrogen-fueled WRE. The results show that the combustion rate of the trailing spark plug (TSP), due to its structural similarity with the passive precombustion chamber, surpasses that of the leading spark plug (LSP). The unidirectional flow field promotes the forward development of the flame of TSP but inhibits the backward development of the flame of LSP. Moreover, the recess in combustion chamber facilitates flame propagation of TSP. Asynchronous ignition mode exhibits a higher indicated thermal efficiency (ITE) than synchronous ignition mode, facilitating effective control of the combustion phase. When the ignition timing of LSP is delayed, and TSP is earlier, the flame of TSP exceeds LSP, resulting in unchanged ITE. When the ignition timing of TSP is delayed, and LSP is earlier, the peak of free radicals and burned volume rate are the highest, resulting in a faster combustion rate. It is recommended that the LSP ignition timing is set earlier for practical operations.