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Comparison of dual and single spark ignition in operation of a large piston aircraft engine

The paper presents the results of the experimental research on the combustion process inside the cylinder of a large piston radial aircraft engine with dual or single spark plug ignition. The tests were carried out on the ASz-62IR-16X radial engine equipped with a double, electronically controlled ignition system with two spark plugs in each cylinder. The constant engine speed tests allowed for comparing the combustion processes with ignition carried out by both spark plugs, the rear plug only, and the front plug only. The analyses were based on the recorded pressure signal from one of the engine cylinders. It has been shown that the type of ignition significantly affects the combustion process and its non-repeatability. The obtained results indicate the leading role of the rear spark plug in initiating the combustion process. When the ignition is carried out with the rear spark plug, the induction period is identical to that for dual ignition, but the combustion process is much less intensive. Ignition carried out with the front spark plug only has a longer induction period but a similar intensity of combustion as with dual ignition. Deactivating one of the plugs also improves the non-repeatability of the combustion process.