Coupling Combustion Simulation and Primary Evaluation of an Asymmetric Motion Diesel Pilot Hydrogen Engine

The thermal efficiency and combustion of conventional hydrogen engines cannot be optimized and improved by its symmetric reciprocating. This article introduces an asymmetric motion hydrogen engine (AHE) and investigates its combustion characteristics using diesel pilot ignition. A dynamic model is firstly proposed to describe the asymmetric motion of the AHE, and then it is coupled into a multidimensional model for combustion simulation. The effect of asymmetric motion on the AHE combustion is also analyzed by comparing with a corresponding conventional symmetric hydrogen engine (SHE). The results show that the AHE moves slower in compression and faster in expansion than the SHE, which brings about higher hydrogen-air mixing level for combustion. The asymmetric motion delays diesel injection to ignite the AHE and its combustion appears later than the SHE, which leads to lower pressure and temperature for reducing NO formation. However, the AHE faster expansion has a more severe post-combustion effect to reduce isovolumetric heat release level and decrease the energy efficiency.