Potential improvement in combustion and pollutant emissions of a hydrogen-enriched rotary engine by using novel recess configuration.

The rotary engine constitutes promising propulsion for unmanned aerial vehicles, and creating turbulence within the rotor chamber is an effective means to strengthen the combustion of this engine concept since it is characterized by a unidirectional flow from the trailing side to the leading side of the rotor chamber. Based on CFD modeling, this work proposed a novel turbulence-induced blade (TIB) configuration and carried out a feasibility assessment focused on this innovation for improving engine performance under different operation/design parameter conditions (spark timing, hydrogen enrichment, and compression ratio). The results of this work confirmed the benefit of this proposed configuration as a useful tool to enhance combustion characteristics and control emissions formation. When the TIB was arranged at the leading part of the rotor chamber, better turbulent flow could be formed in the desired location and actually enhanced the combustion. Compared with the no-blade rotor chamber, the indicated thermal efficiency of the leading-blade, middle-blade, and trailing-blade rotor chambers increased by 7.3%, 5.1%, and 0.8%, respectively. Further assessment of TIB benefits demonstrated that the introduction of the TIB could postpone the optimal spark timing, and effectively increase the pressure within the rotor chamber, and the later the spark timing is, the more significant the increment in the peak pressure. Compared with hydrogen-enriched rotary engines, the TIB is more sensitive to the combustion improvement of pure gasoline rotary engines, and the difference between the no-blade and leading-blade rotor chambers reduced notably in terms of emissions formation as hydrogen enrichment increased. It is recommended that a higher compression ratio could be realized by decreasing the chamber volume, thus producing better engine performance. The turbulence intensity in the leading-blade rotor chamber is higher than that in the non-blade rotor chamber, and the discrepancy shows an increasing trend with the increase of the compression ratio. The effect of the TIB on efficiency improvement and emissions reduction is negligible at a relatively higher compression ratio (9.6).