Effects of Ignition Control on Combustion Process Non-Repeatability in an Aircraft Radial Piston Engine

The ignition method significantly affects the combustion process in piston aircraft engines. This paper presents the results of bench tests of two variants of the radial piston aircraft engine: equipped with a standard magneto system and an electronic dual ignition system. The engine was tested in steady states for operating points defined by rotational speed and load. Their values corresponded to a load ranging from 50% of nominal power to take-off power. The ignition advance angle was constant for the engine equipped with ignition magnetos, while for the second engine variant it was determined by the developed algorithm introduced to the electronic ignition system control unit. The analysis of the combustion process was based on pressure measurements in one cylinder. The article focuses on the non-repeatability of engine operation described as a coefficient of variation for parameters such as indicated mean effective pressure, peak pressure, peak pressure angle, maximum rate of pressure rise, maximum rate of pressure rise angle and mass fraction burned. The obtained results indicate that the replacement of a magneto system with an electronic system results in a greater stability (repeatability) of the combustion process and maintaining assumed power.