Modeling and parametric study of the performance-emissions trade-off of a hydrogen Wankel rotary engine

The use of hydrogen energy is considered an essential research direction for carbon neutrality. Hydrogen Wankel rotary engines (WREs) are of increasing interest to researchers due to their excellent power and emissions characteristics. For WREs, the intake and exhaust phases significantly influence performance and emissions. This study focuses on the implementation of a one-dimensional (1-D) model of a hydrogen WRE, and studies the effects of intake port closing (IPC) timing and exhaust port opening (EPO) timing on the performance and emissions. The 1-D model is implemented in the AVL BOOST modeling environment and verified with experimental data at different excess air ratios (λ). The effects of leakage and crevice are also considered in the modeling process. The simulation results demonstrated that the indicated mean effective pressure (IMEP) decreased by approximately 14% due to leakage and crevice compared with the ideal model. The volumetric efficiency (VE) reduction caused by the crevice was less than the leakage effect. Meanwhile, VE improved with the increasing λ. As the IPC advanced, the gas reflux was reduced, which increased the in-cylinder mass and IMEP. However, the relative NOx emissions increased due to the higher temperature. The variation caused by EPO timing in performance and emissions was reversed. The VE first increased and then decreased with the delayed EPO timing. This paper provides a viable solution with more practical guidance for optimizing the performance and emissions of hydrogen WRE.