Numerical investigation of the effects of typical cylinder shapes with turbulent jet ignition on the combustion performance of methanol-fueled rotary engine

Abstract

Due to the insufficient combustion and high carbon emissions of rotary engine (RE), a strategy employing methanol and turbulent jet ignition(TJI) was adopted, while the primary purpose of TJI mode is to achieve the impingement between rotary piston surface and jet flame in order to enable multi-point ignition. Optimizing this interaction could enhance the ignition efficiency and overall combustion characteristics of methanol fuel within the cylinder. Thus, this paper adopts three typical cylinder shapes to alter impingement height and employs varying TJI ignition strategies to affect in-cylinder flame propagation, investigating the effect of these factors on combustion process and combustion performance via numerical simulation. The numerical outcomes indicate that the cylinder shape, jet orifice angle and ignition timing collectively affect the impingement height between rotary piston surface and jet orifice at 10°CA (BTDC). The intensity of jet flame impinging on the rotary piston surface intensifies as the impingement height decreases, which further promotes the turbulent kinetic energy(TKE) and accelerates in-cylinder flame propagation. Furthermore, the advance of ignition timing improves combustion intensity and flame propagation within the cylinder. Additionally, with the decreasing of jet orifice angle, the flammable blend mass within the pre-combustion chamber is relatively elevated under any fixed cylinder shape, thus facilitating to generate a more intense jet flame Based on the comprehensive analysis of all cases, double pocket(DP) type cylinder shape exhibits optimal combustion performance with −30° jet orifice angle and 35°CA (BTDC) ignition timing, with the peak value in-cylinder pressure(PVIP) of 1.9 MPa.