A numerical methodology for three-dimensional fluid dynamics and chemical kinetics simulation of the combustion and gas-exchange processes in the Wankel engine was developed and validated. Two approaches of performance enhancement were studied—the addition of a slot in the rear side of the rotor recess, and installation of a third plug in the trailing side of the working chamber, in addition to the two available plugs mounted in the leading side of the baseline engine. The obtained results showed that the suggested three-plug arrangement significantly improves the engine performance. Furthermore, positioning the trailing plug further from the passage between the trailing and leading sides is of preference for higher mean in-chamber pressures. Nevertheless, for maximum performance, the distance should be brought to an optimum as during the intake stroke there is a loss of inducted charge due to backflow from the trailing plug hole. For the three-plug arrangement the presence of a slot is necessary for the prevention of early flame quenching in the trailing side, while keeping the added volume to a minimum. Moreover, positioning the slot and the trailing plug off-center, results in higher flow intensity towards the leading plugs, and accordingly, to a higher combustion efficiency. For dual-plug ignition system (two plugs in the leading side) it is preferable to maintain minimum clearance in the trailing side.

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<div class="section abstract"><div class="htmlview paragraph">In recent years, rotary combustion engines have experienced renewed interest as alternative power sources in various applications, due to their multi-fuel capability, simplicity, and advantageous power-to-weight, and power-to-volume ratios. Further improvements to the engine's performance require a thorough examination of its inherent shortcomings. Most prominent are its incomplete, slow combustion and lower thermal efficiency, both of which are caused by the combustion chamber's high surface-to-volume ratio and unfavorable flattened shape. Considering the difficulties involved in performing experimental measurements on rotary combustion engines, numerical simulations have proven to be valuable tools for research and development. This study presents a validated three-dimensional RANS model that simulates the flow, reaction kinetics, and heat transfer in rotary combustion engines. The model incorporates a conjugate heat transfer approach, which couples the heat transfer between the solid rotor, the convective airflow within its core, and the gas in the combustion chamber. Different heat transfer models and meshing approaches were evaluated as part of the development of the model for high load/high revving speed applications. Lastly, an advanced thermal barrier coating was proposed for use in rotary combustion engines. The developed model was modified to include a temperature discontinuity at the solid-gas interfaces of the rotor, which is related to the thermal resistivity of the coating. It was predicted that the application of the coating would reduce heat losses by 10 %, lower the mean temperature of the rotor by 4.6 %, and improve the fuel conversion efficiency by 1.3 %. The results suggest that an advanced thermal barrier coating can reduce thermal loads and enhance the performance of rotary combustion engines.</div></div>