Numerical Study of the Effect of Injection Strategy and Compression Ratio on Gasoline/Diesel Fueled RCCI Engine 2018-32-0017
RCCI engine is proven to have better combustion control and producing very low NOx and soot emissions. However, RCCI engines operations is limit by HRR and PPRR as well as weak combustion efficiency which results in high release of HC and CO. Engine management factors like injection strategy and compression ratio can affect the reactivity of fuels in cylinders as well as the gas temperature increase rate which are the important factors to control the RCCI combustion. Injection strategies such as single and double injections has been studied before but the effects are still unpredictable and the effects of compression ratio towards combustion characteristic and emissions need to be further analyzed. This study using a 3D computational fluid dynamic (CFD) combustion model to study the effect of combustion characteristic and emissions of single, double injections strategy and compression ratio. The model is validated by comparing the simulation result with a previous research. The results show that double injections strategy can produce more extensive combustion propagation than single injection strategies. This is because the second injection of diesel fuel which is more reactive creates steeper reactivity gradient and equivalence ratio gradient throughout the combustion chamber. This results in lower NOx, soot, HC and CO compare to single injection strategy. Single injection strategy combustion depends on the reactivity gradient and equivalence ratio gradient of injected diesel fuel which need to be at the right level. The effect of compression ratio on the best parameter of double injection strategy were also investigated. The results show that higher compression ratio can further reduce soot, HC and CO to very low level but increase the NOx.
Muhammad Asyraf Mohd Azmi, Mohd Radzi Abu Mansor, Wan Mohd Faizal Wan Mahmood, Taib Iskandar Mohamad
Universiti Kebangsaan Malaysia, Yanbu Industrial College, Saudi Arabia
SAE/JSAE Small Engine Technology Conference