Evaluation of Spark-Ignited Kerosene Operation in a Wankel Rotary Engine

Wankel rotary engines (REs) are often used for unmanned aerial vehicle (UAV) applications due to their excellent power-to-weight ratio and their smooth operation. Existing RE propulsion units are mainly designed to run on high-volatility fuels like aviation gasoline or regular gasoline. However, specific applications require a jet fuel or even multi-fuel capability. Due to their geometry, the low compression ratio (CR) of REs prevents the implementation of compression ignition (CI) combustion processes. While publications of modified spark-ignition engines that are able to run on low-volatile fuels are already few in number, publications of heavy-fuel spark-ignited (SI) REs can hardly be found at all.

The purpose of this paper is as follows: The operation of a SI RE operated on kerosene is discussed. Accordingly, a thermodynamic analysis is carried out at warmed-up operation with kerosene. It is shown that sufficient performance and power output can be achieved on kerosene for full-load behavior. Furthermore, cold-start tests are carried out to investigate the limits of kerosene operation. Therefore, a low-temperature test bench is developed that allows the investigation of engine starts down to −30°C. The challenges of mixture formation for heavy fuels in port fuel injection systems for REs at cold-start conditions are investigated and discussed. It is demonstrated that cold starting a SI RE down to −25°C is possible with correct measures.