Unmanned, autonomous aerial vehicle applications are an indispensable part of
modern aviation. The propulsion of such aerial vehicles is often realized by
Wankel rotary engine. They are particularly suitable for this application due to
their high power-to-weight ratio and smooth operation. As a result of their
properties and geometric characteristics, Wankel rotary engines are usually
operated with highly volatile fuels like aviation gasoline (AvGas). In
comparison, the existing aviation refueling infrastructure is oriented toward
the most common aviation fuel, kerosene. This and other reasons, such as
significantly lower prices and easier fire protection regulations, lead to the
desire to be able to operate these propulsion units with kerosene. Opposed to
reciprocating engines, the low compression ratio of rotary engines prevents the
implementation of compression ignition (CI) combustion processes. In previous
studies, the effects of an air-assisted injection system on operation with
different fuels were examined on the basis of a spark-ignited combustion
process. Operation with kerosene in particular requires appropriate mixture
preparation in order to be able to ensure a stable combustion process over a
wide operating range. The purpose of this paper is to investigate improvements
for further optimization of the combustion process with regard to efficiency,
stability, and power output based on the findings of the previous
investigations. One of the most promising steps is a combustion process with the
ignition of four spark plugs (2+2). Based on simulative investigations using
computational fluid dynamics (CFD), a potential analysis regarding the optimal
positioning of the additional spark plugs and the effects on the combustion
process is carried out. It could be shown that a correspondingly “early”
positioning of the trailing spark plugs should be aimed at. Based on the
simulated results, the preferred spark plug configuration is implemented on the
real engine. Subsequently, the influence of the use of four spark plugs on the
combustion process is examined on the basis of experimental investigations. In
particular, the effects on the possible operating range in kerosene operation
are investigated in more detail.