Multi-field coupling effect of injection on dynamics and thermodynamics of a linear combustion engine generator with slow compression and fast expansion

Abstract

An asymmetric reciprocating engine (ARE) with slow compression and fast expansion is designed in this paper, which can improve combustion performance and energy conversion efficiency by optimizing piston motion. However, due to the particularity of piston motion, how to consider the multi-field coupling effect of injection position (IP) on dynamics and thermodynamics becomes a key issue. Therefore, this paper proposes a multi-dimensional coupled model including motion, gas exchange and combustion, and uses an iterative algorithm to solve the model. The results show that ARE has better gas exchange performance and higher acceleration near TDC than conventional engines because of its slow compression and fast expansion processes, which lead to its obvious advantages in gas organization and combustion heat release. Furthermore, increasing IP has a positive excitation effect on the operating frequency and the combustion performance of ARE because the changed motion results in a longer ignition delay and a better fuel atomization environment. However, increasing IP continuously will lead to weak turbulent motion, which will greatly reduce the combustion reaction rate. The results suggest that increasing the IP is beneficial to improve the thermal efficiency of ARE and reduce soot generation, but too large an IP is not supported.