Effects of spark ignition chamber arrangement on combustion characteristics in a hydrogen rotary engine

In dual-spark-plug rotary engines, the trailing spark plug reduces unburned charge resulting from the combustion-chamber geometry. To investigate the effect of ignition-chamber layout on combustion characteristics, this study employs computational-fluid-dynamics to analyze a dual-spark-plug hydrogen rotary engine at lean combustion, focusing on variations in leading spark plug's position and height, and trailing spark plug's position and the ignition channel inclination. The results revealed that displacing the leading ignition chamber forward promoted the leakage of fresh charge, whereas rearward displacement induced leakage of high-temperature and pressure residual gas, thereby lowering the local equivalence ratio. However, the reaction-kinetic analyses indicated that elevated temperature and pressure within the ignition chamber increased laminar flame velocity. When the height of leading ignition chamber was increased, inter-chamber leakage increased marginally, the peak equivalence ratio inside the chamber decreased, and the combustion phase was accordingly delayed. Forward displacement of the trailing ignition chamber decreased the mass of leaked fresh charge, but the flame kernels initiated by the dual spark plugs rapidly merged, which reduced the effective flame-propagation speed. Increasing the inclination channel angle had little effect on leakage but resulted in higher in-cylinder pressures.