Enhancing the Efficiency of Rotary Thermal Propulsion Systems

Xuankun Shen, Aaron W. Costall

Research output: Contribution to journalArticlepeer-review


Transport electrification is essential for reducing CO2 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.

Original languageEnglish
Article number2112
Issue number9
Early online date28 Apr 2024
Publication statusPublished - 31 May 2024

Data Availability Statement

The data presented in this study are available on request from the corresponding author due to reasons of commercial sensitivity.


  • CFD
  • combustion chamber
  • electric vehicles
  • LES
  • pre-chamber jet ignition
  • range extender
  • thermal efficiency
  • turbulence
  • two-stage rotary engine
  • Wankel rotary engines

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Energy (miscellaneous)
  • Control and Optimization
  • Electrical and Electronic Engineering

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