Effect of multi-hole passive jet ignition on thermodynamic and combustion characteristics of hydrogen-doping elliptical rotary engine in high-altitude environment

The conventional internal combustion engine using spark plug ignition (SI) faces the risk of performance degradation in high-altitude environments. To address this problem, this paper proposes a novel elliptical rotary engine (ERE) using hydrogen direct injection and passive jet ignition (PJI). Firstly, the 3D numerical model of PJI-ERE is developed to study the effect mechanism of PJI arrangement on mixture distribution and internal flow field. Furthermore, the jet flame shape and combustion characteristics of PJI-ERE are investigated. Finally, the impacts of PJI arrangement on the thermodynamic and emission performance of PJI-ERE at different altitudes are analyzed comparatively. The results show that at ground condition, the single-hole jet (Jet1) offers the highest jet flame kinetic energy and thus the highest thermal efficiency of 0.348. The circumferential three-hole jet (Jet3-C) produces a faster flame propagation speed via forward swirl, and reaches the best thermodynamic performance and the worst emission performance at high-altitude condition. The thermal efficiency of Jet3-C is 18.33 % and 20.48 % higher than that of Jet1 and SI at 6000 m altitude, respectively. The five-hole jet (Jet5) delays the expansion of local high-temperature zone by dispersed jet, and thus provides a better trade-off between thermodynamic and emission performance at high-altitude condition.