Analyzing the impact of hydrogen direct injection parameters on flow field and combustion characteristics in Wankel rotary engines

This study aims to explore the influence of hydrogen injection parameters on the flow field and combustion characteristics in Wankel rotary engines. The numerical results showed that the area of high-speed hydrogen jet flow in the combustion chamber decreased when the hydrogen injection timing (HIT) was delayed to 390 degrees of eccentric angle. This weakened the mixing process in the combustion chamber but resulted in a lower residual gas in the ignition chamber at the end of injection. However, a lean mixture area was formed at the rear end of the combustion chamber. When the HIT was changed, the velocity and turbulent kinetic energy (TKE) fields at the ignition timing were almost the same. The distribution of the equivalence ratio significantly impacted the initial flame kernel, whereas TKE had minimal influence. When the hydrogen nozzle diameter (HND) was increased to 4 mm and the injection pressure (HIP) was raised to 10 MPa, the size of the high-velocity zone and the mass of leakage gas were increased. When the concentration of hydrogen near the leading spark plug was high, it could cause the rapid consumption of the unburned mixture in the front part of the combustion chamber. The high-temperature and high-pressure mixture generated by the instantaneous heat release accelerated the flame propagation to the back part of the combustion chamber, thus leading to the occurrence of knock.