The effect of H2 enrichment on in-cylinder flow behavior, engine performances and exhaust emissions: Case of LPG-hydrogen engine

In this paper, numerical and experimental studies were performed to explain the effect of hydrogen enrichment on LPG fuelled engine; and consequently its effect on in-cylinder flow characteristics, engine performances and exhaust emissions. Also, the influence of the intake system geometry on in-cylinder mixture flow behavior was studied. The in-cylinder flow velocity, turbulence characteristics and hydrogen mass fraction were evaluated in the intake stroke in order to analyze the intake flow behavior. For this purpose, a 3D Computational Fluid Dynamics (CFD) code is adopted. The variation of brake torque (BT), brake specific fuel consumption (BSFC), NOx and CO emissions for various engine speeds were investigated for gasoline, LPG and LPG-hydrogen fuelled engines, using an experimental study. Engine performances were investigated on various fractions of LPG-hydrogen blends (0%, 10% and 20% of H2). The results has shown that the BT produced by LPG-hydrogen blend is increased by 12% and 20% compared to gasoline and pure LPG operations respectively when the hydrogen fraction equal to 20%, particularly for high engine speeds. CO emissions tend to be eliminated with the addition of hydrogen. NOx emissions for LPG-hydrogen operation was decreased by 3.25% and 1.89% compared to gasoline and LPG fuels, respectively. Simulation and experiments results demonstrate the benefits of the hydrogen enrichment on the in-cylinder flow characteristics and engine performances.