A computational fluid dynamics investigation of an alternative two stroke engine design

Abstract

This study presents a computational fluid dynamics analysis of a new two-stroke engine design aimed at addressing the traditional shortcomings of crankcase-scavenged designs. The proposed concept incorporates a supercharged, uniflow, two-stroke configuration with a dedicated crankcase lubrication system, effectively decoupling the oiling mechanism from the intake charge. This offers significant scope for reducing unburned hydrocarbon emissions. The design incorporates an overhead rotary intake valve and piston-controlled exhaust ports in the cylinder. The port timing has been tuned to minimize short-circuiting losses, resulting in a scavenging efficiency of 62% without loss of fresh charge to the exhaust. A new combustion chamber geometry has also been developed to enhance the tumble flow intensity near the spark plug region. This enhanced flame propagation and improved stability. Additionally, the implementation of a pre-chamber ignition system has been investigated, including multiple active fueling configurations, and is evaluated based on combustion duration. The simulation results indicate a 33% reduction in combustion duration, demonstrating the potential of the proposed design in improving the overall combustion performance.