Investigation of the effect of piston geometrical parameters on RCCI engine performance based on second law of thermodynamic

The reactivity controlled compression ignition engines have high thermal efficiency and low exhaust emission of nitrogen oxides and soot because of low temperature combustion. In this type of engines, low reactivity fuel is injected to air through intake port and high reactivity fuel is injected into the combustion chamber during compression stroke. The aim of current study is to investigate the effect of engine geometrical parameters on different terms of exergy in reactivity controlled compression ignition engines. In this study natural gas and diesel fuel are used as low and high reactivity fuels and effects of top land height and depth of piston bowl on different exergy terms are investigated. Engine is simulated utilizing a CFD model and the numerical data are compared to experimental data and the validity of model is evaluated. Thermomechanical exergy, chemical exergy, work, irreversibility and exergy loss due to heat transfer are calculated at each time step. The results show that the depth of piston bowel has more significant effect on heat transfer exergy in comparison to the top land height. Also, comparison to depth of piston bowel, the top land height affects chemical exergy terms significantly. Comparison to the top land height, depth of piston bowl affects total irreversibility more significantly.