Effects of structural parameters of active pre-chamber on the combustion process of methanol/gasoline TJI rotary engine

• Investigated APC-RE's APC structural parameters impact on cylinder flow and combustion. • The APC's throat diameter has a greater impact on engine performance than throat length direction. • Orifice diameter affects APC pressure and regulates jet flame velocity . The application of Turbulent Jet Ignition (TJI) combustion mode in spark ignition engine can improve combustion efficiency and output power. This paper innovatively proposes the application of active pre-chamber (APC) in rotary engine (RE) to realize this mode. And blending a certain percentage of methanol in gasoline to achieve carbon reduction. A three-dimensional computational model of the APC-RE was developed, and the effects of three APC structural parameters including throat section diameter, throat section length and orifice diameter on the component flow and combustion characteristics were investigated. The results showed that the APC-RE exhibited higher sensitivity to the diameter of the throat section than the length variation under the fixed active fuel injection strategy. The low length or small diameter of the throat section causes insufficient energy in the APC jet, and too high values cause unstable combustion. The optimal APC volume is achieved at a throat length of 8 mm and a diameter of 6 mm, with the highest Indicated mean effective pressure (IMEP) and Indicated thermal efficiency (ITE). Next, The APC volume was fixed and the effect of jet orifice size on RE performance was discussed and the optimal size was determined 1.25 mm, which can further optimize the jet velocity and can continue to increase IMEP and ITE by 1.24 % and 1.46 % respectively.