Enhancing the Efficiency of Rotary Thermal Propulsion Systems

Xuankun Shen and Aaron W. Costall ()
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Xuankun Shen: Department of Mechanical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK
Aaron W. Costall: Advanced Vehicle Engineering Centre, Cranfield University, Cranfield, Bedford MK43 0AL, UK

Energies, 2024, vol. 17, issue 9, 1-26

Abstract: Transport electrification is essential for reducing CO 2 emissions, and technologies such as hybrid and range-extended electric vehicles will play a crucial transitional role. Such vehicles employ an internal combustion engine for on-board chemical energy conversion. The Wankel rotary engine should be an excellent candidate for this purpose, offering a high power-to-weight ratio, simplicity, compactness, perfect balance, and low cost. Until recently, however, it has not been in production in the automotive market, due, in part, to relatively low combustion efficiency and high fuel consumption and unburnt hydrocarbon emissions, which can be traced to constraints on flame speed, an elongated combustion chamber, and relatively low compression ratios. This work used large eddy simulations to study the in-chamber flow in a peripherally ported 225cc Wankel rotary engine, providing insight into these limitations. Flow structures created during the intake phase play a key role in turbulence production but the presence of the pinch point inherent to Wankel engine combustion chambers inhibits flame propagation. Two efficiency-enhancement technologies are introduced as disruptive solutions: (i) pre-chamber jet ignition and (ii) a two-stage rotary engine. These concepts overcome the traditional efficiency limitations and show that the Wankel rotary engine design can be further enhanced for its role as a range extender in electrified vehicles.

Keywords: Wankel rotary engines; range extender; electric vehicles; combustion chamber; thermal efficiency; CFD; LES; turbulence; pre-chamber jet ignition; two-stage rotary engine (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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