Study on the sealing system of an opposed rotary piston engine

Abstract

The opposed rotary piston (ORP) engine represents as a promising power source for unmanned aerial vehicles (UAVs), due to its structural simplicity and exceptional power density. But the rotary piston motion gives rise to significant gas leakage challenges, which critically deteriorate engine performance. This study conducts a systematic analysis of the existing sealing configuration and establishes computational fluid dynamics (CFD) models to quantify cylinder gas leakage. The results demonstrate that strategic placement of piston rings between rotating shaft contact surfaces effectively reduces leakage flows. Reducing the engine load from 100% to 60% decreased leakage through the rotating shaft contact surfaces from 5.755 × 10⁻⁵ to 1.841 × 10⁻⁵ kg. Concurrently, decreasing fit clearance decreased from 0.1 to 0.06 mm reduced the circulating leakage between shafts from 5.755 × 10⁻⁵ to 2.942 × 10⁻⁵ kg, corresponding to a 48.8% reduction. Additionally, combustion gas blowby between adjacent chambers exhibits load-dependent characteristics, decreasing from 6.74 × 10⁻⁶ to 1.17 × 10⁻⁷ kg when the engine load decreases from 100% to 60%. Analysis of the sealing strip-groove interface confirms that leakage rates and gas velocities exhibit inverse proportionality to clearance dimensions.