Evaluation of blunt body setting for improving the combustion performance of a jet ignition hydrogen/natural gas rotary engine

Hydrogen/natural gas mixture (HNGM) is considered a highly promising alternative fuel for rotary engines (REs) due to its ability to significantly reduce carbon emissions. However, the unique operating mode and cylinder structure of REs present challenges for improving combustion efficiency. Hence, considering that the flame and flow field characteristics inside various types of combustion devices can be improved by using blunt bodies, this study evaluates the impact of V-shaped bluff body (VSBB) settings on the combustion performance of a jet ignition rotary engine (JIRE) fueled with HNGM. The results revealed that in contrast to the case with no VSBB, the settings of a VSBB with any included angle and any setting position all could improve the burning rate in the cylinder. However, regarding any VSBB with a fixed included angle, as the VSBB setting position moves from the rear to the front of the rotor piston, the acceleration degree of VSBB on the combustion speed in the cylinder continues to increase. In addition, for any fixed VSBB setting position, the peak value of in-cylinder pressure (PVIP) first increases and then decreases as the included angle of the VSBB increases. Overall, compared to the case without a bluff body, the VSBB performs best when positioned at the front of the rotary piston with a 180 degrees angle. Its inclusion increases the peak in-cylinder pressure (PVIP) by 8.5% and maximizes the indicated work by 6.4%, but also results in a 15% increase in NOx emissions. This study provides detailed insights into optimizing flame propagation and combustion efficiency in JIREs using HNGM, offering new strategies for improving performance and reducing emissions in rotary engines.