Enhancing combustion in an ethanol rotary engine via turbulent jet ignition: parametric study and mechanism analysis

Abstract

Enhancing the combustion of ethanol rotary engine (ERE) is crucial for carbon neutrality. This study systematically compares the effects of conventional spark plug ignition mode (CSPIM) and turbulent jet ignition mode (TJIM) on the performance of an ERE. This investigation employs a combined methodology of experimental validation and numerical simulation, systematically analyzes the combustion characteristics of both ignition modes across multiple equivalence ratio conditions. Furthermore, this research elucidates the effect of jet nozzle diameter (JND) on the combustion behavior of the TJIM. The results reveal that TJIM’s effectiveness is governed by the coupling between the energy of the jet flame and the concentration of the mixture in the pre-combustion chamber. It demonstrates superior flame propagation and combustion at equivalence ratios of 1.0 and 1.2 by generating highly turbulent jet flames, but underperforms CSPIM under an equivalence ratio of 0.8 due to reduced jet flame intensity. Furthermore, the optimal JND shifts with the global equivalence ratio — 3.5 mm for lean and 2.0 mm for stoichiometric combustion. The JND governs a trade-off between the mass of fuel in the pre-combustion chamber and the jet flame velocity. While TJIM significantly reduces CO emissions via more complete combustion, it increases NO formation due to higher temperatures.