Analysis of Torque Waveforms in Two-Cylinder Engines for Ultralight Aircraft Propulsion Operating on 0W-8 and 0W-16 Oils at High Thermal Loads Using the Diamond-Like Carbon Composite Coating 03-15-01-0005

Piston internal combustion engines used in the propulsion of ultralight aircraft are characterized by special operating conditions, especially an increased engine oil temperature. Most of the engines intended for the drive of the propeller drivetrain are air cooled. Failure to introduce an additional cooling agent so as to absorb and remove heat from the running engine makes the average lubricating oil temperature rise to about 140°C in the pistohn ring part. With such a thermal load, changes in the moments of resistance to motion of the engine are difficult to determine in the conditions of engine tests due to difficulties in temperature stabilization. The performance of aircraft engines requires taking into account many variables that are difficult to determine, which may affect changes in the moment of resistance to movement of the engine, especially when using oils of low dynamic viscosity.

The experimental tests on the engine dynamometer undertaken in the article are to fill the scientific gap regarding the analysis of the waveforms of the moment of resistance to air movement of a two-cylinder internal combustion engine operating in a high-temperature range with the use of 0W-8 and 0W-16 oils. So far, no experimental studies have been carried out to measure the engine resistance torque for the operating conditions of aircraft internal combustion engines intended for the propulsion of ultralight aircraft with the use of low-viscosity oils. The following coating was applied on the sliding surfaces of the piston rings: DLC: a - C: Cr + a - C: H, 5-12% H. The scientific value of the work is the assessment of the possibility of reducing the moment of resistance to motion in nonstandard operating conditions of aircraft internal combustion engines. The benefits resulting from the use of oils with low dynamic viscosity at high engine operating temperatures are strictly dependent on the range of the applied rotational speeds of the shaft.