Effect of side leakage on the flow field and combustion process of a rotary engine

The rotary engine offers the advantages of high-power density and compact structure, yet its performance is severely constrained by gas leakage, and the influence of side leakage on the in-housing working process remains insufficiently understood. To clarify the effect of side leakage on in-housing flow field and combustion, a three-dimensional CFD model incorporating side leakage was developed for a premixed gasoline rotary engine. Simulations were conducted with three representative equivalent leakage areas (ELA). The results showed that side leakage significantly restructured the in-housing flow field. Under the large leakage area condition, the intake airflow was markedly deflected, the high-velocity zone shifted toward the leading side of the combustion chamber, and a low-velocity zone formed around the intake port. During the expansion stroke after ignition, the local flow-field disturbance near the spark plug intensified, whereas the mean turbulent kinetic energy decreased overall. During the combustion process, the flame front became distorted and propagated asymmetrically, and the peak heat release rate decreased. Moreover, under the large leakage area condition, the peak heat release phase was retarded, whereas the subsequent heat release was enhanced. Meanwhile, both the indicated work and the indicated thermal efficiency deteriorated noticeably under leakage conditions. Finally, a comparison between side leakage and apex leakage revealed that, under the same ELA, the apex leakage mass flow was significantly larger than the side leakage. The study concluded that, although the magnitude of side leakage was lower than that of apex leakage, its detrimental impact on flow field organization, turbulence generation, and flame propagation was pronounced, making it a key factor contributing to the degradation of engine power and fuel economy.