Combined influence of ignition chamber volume and spark plug channel diameter on the performance of small-scale natural gas Wankel rotary engine

Abstract

To improve the poor in-cylinder combustion condition of the small spark ignition Wankel rotary engine (SI-WRE) and improve its efficiency, this paper conducted a comprehensive optimization of its ignition environment. Since there are no known effects of ignition chamber characteristics, including ignition chamber volume () and spark plug channel diameter (), on the ignition environment, various combinations of and were established, simulated, and compared, using Computational Fluid Dynamics (CFD) methods with validated models. As there are small and complex structures in the small SI-WRE, along with the huge simulation load in the case study, special treatments were adopted in mesh division to maintain the fast and accurate simulation. The results showed a wide thermal efficiency range of 8.51–32.13% under various and combinations, indicating that the engine performance was deeply limited by the ignition chamber. and also had profound influences on short-term (affected by ) and long-term (affected by ) flow losses, fresh intake at spark region, combustion speed, and working stability. Stable working condition was achieved when cc and mm, while powerful situations were cc and mm, or cc and mm.