Effects of diesel ignition on gas motion and heat transfer in asymmetric reciprocating hydrogen engines

In this paper, the unique gas flow and heat transfer characteristics of an asymmetric reciprocating hydrogen engine are investigated relative to a conventional engine. By means of compression ignition, coupling kinetic and thermodynamic models, and combining software iterative simulation, the effects of diesel ignition and other effects on the gas flow and heat transfer characteristics in the engine cylinder are revealed and discussed in comparison with the experimental results. The comparison results show that the enhancement of turbulent kinetic energy during hydrogen injection increases the gas flow motion velocity, which leads to a more homogeneous fuel mixing and accelerated combustion. Moreover, the asymmetric reciprocating hydrogen engine has a shorter combustion duration and faster expansion, which reduces the time available for heat transfer and therefore transfers less heat to the outside world than the conventional reciprocating hydrogen engine. In terms of combustion heat release, the asymmetric reciprocating hydrogen engine has a higher heat release rate, but the peak pressure and temperature are about 20% and 9% smaller, respectively, than those of the conventional reciprocating hydrogen engine.