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

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 ((Formula presented.)) and spark plug channel diameter ((Formula presented.)), on the ignition environment, various combinations of (Formula presented.) and (Formula presented.) 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 (Formula presented.) and (Formula presented.) combinations, indicating that the engine performance was deeply limited by the ignition chamber. (Formula presented.) and (Formula presented.) also had profound influences on short-term (affected by (Formula presented.)) and long-term (affected by (Formula presented.)) flow losses, fresh intake at spark region, combustion speed, and working stability. Stable working condition was achieved when (Formula presented.) cc and (Formula presented.) mm, while powerful situations were (Formula presented.) cc and (Formula presented.) mm, or (Formula presented.) cc and (Formula presented.) mm.