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The X engine is a non-Wankel rotary engine that allies high power density and high efficiency by running a high-pressure Atkinson cycle at high speeds. The X engine overcomes the gas leakage issue of the Wankel engine by using two axially-loaded face seals that directly interface with three stationary radially-loaded apex seals per rotor. The direct-interfacing of the apex and face seals eliminates the need for corner seals of the typical Wankel engine, significantly reducing rotary engine blowby. This paper demonstrates the sealing performance that can be achieved by this new type of seal configuration for a rotary engine based on dynamics models and experiments. The dynamics models calculate the displacement and deformation of the face and apex seals for every crank angle using a time implicit solver. The gas leakage is then calculated from the position of the seals and pressure in the chambers and integrated over a rotor revolution.

This paper describes predictive models and validation experiments used to quantify the in-chamber heat transfer of LiquidPiston’s rotary 70cc SI “XMv3” engine. The XMv3 engine is air cooled, with separate cooling flow paths for the stationary parts and the rotor. The heat transfer rate to the stationary parts was measured by thermal energy balance of that circuit’s cooling air. However, because the rotor’s cooling air mixes internally with the engine’s exhaust gas, a similar procedure was not practical for the rotor circuit. Instead, a CONVERGE CFD model was developed, and used together with GT-POWER to derive boundary conditions to estimate a ratio between rotor and stationary parts heat transfer, thus allowing estimation of rotor and total heat losses. For both cases studied (5000 and 9000 rpm under full load), the rotor’s heat loss was found to be ∼60% that of the stationary parts, and overall heat losses were less than 35% of supplied fuel energy.