Research on energy distributions of the lateral swirl combustion system in DI diesel engines

The lateral swirl combustion system (LSCS) can improve the air-use, fuel and emission performance of direct injection (DI) diesel engines. In this study, the differences in energy distributions between the LSCS and the double swirl combustion system (DSCS) were analyzed under different working conditions using a single-cylinder test system. A simulation calculation was used to compare the velocity, mixture equivalence ratio and in-cylinder temperature distributions of the working medium in the two combustion chambers, elucidating the different energy distributions of the two chambers. Additionally, a new idea is proposed herein for the design of LHR engines. The experimental results show that, compared with the DSCS under different operating speeds (1300–2100 r/min) and different loads (21–43 kW), the indicated thermal efficiency of the LSCS was approximately 2% higher, the percentage of the exhaust energy and heat transfer to the total energy was approximately 2% lower, the cylinder head temperature was 2–20.5 K lower, the ratio of the cylinder head heat transfer to the total heat transfer was 2–8% smaller and the heat transferred to the cooling water in the water jacket of the cylinder head was 0.2–1 kW lower. The in-cylinder velocity distribution, mixture equivalence ratio and temperature distribution of both the LSCS and the DSCS were compared through simulation. The results show that the fuel in the LSCS developed along the wall of the combustion chamber circumferentially due to the convex edge, and the high temperature zone distributed along the circumference of the combustion chamber. In the DSCS, most of the fuel moved to the cylinder head due to the circular ridge, and the high temperature zone existed near the cylinder head. The LSCS had a lower cylinder head temperature, a higher exhaust gas temperature, and less heat transferred to the cooling water through the cylinder head. Therefore, the unique shape of the LSCS chamber guided the movement of the fuel and reduced the concentration of the fuel/air mixture near the cylinder head, which reduced the heat transferred to the cooling system through the cylinder head and improved the thermal efficiency. In addition to these findings, this study also provides a foundation for the design of a low heat rejection engine.