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A model for oil consumption due to in-cylinder evaporation of oil in reciprocating engines, has been developed. The model is based on conservation of mass and energy on the surface of the oil film left on the cylinder by a piston ring pack, at the oil/gas interface, and also conservation of energy within the oil film and cylinder/coolant interface. The model is sensitive to in-cylinder conditions and is part of an integrated model of ring pack performance, which provides the geometry of the oil film left by the ring pack on the cylinder. Preliminary simulation results indicate that a relatively small but not insignificant fraction (2-5%) of the total oil consumption may be due to evaporation losses for a heavy duty diesel at the rated condition. The evaporation rate was shown to be sensitive to oil grade and upper cylinder temperature. Much of these losses occur during the non-firing half of the cycle.

Detailed heat transfer measurements were made in the combustion chamber of a Cummins single cylinder NH-engine in two configurations: cooled metal and ceramic-coated. The first configuration served as the baseline for a study of the effects of insulation and wall temperature on heat transfer. The second configuration had several in-cylinder components coated with 1.25 mm (0.050″) layer of zirconia plasma spray -- in particular, piston top, head firedeck and valves. The engine was operated over a matrix of operating points at four engine speeds and several load levels at each speed. The heat flux was measured by thin film thermocouple probes. The data showed that increasing the wall temperature by insulation reduced the heat flux. This reduction was seen both in the peak heat flux value as well as in the time-averaged heat flux. These trends were seen at all of the engine operating conditions.

An experimental study was conducted of the heat radiation in a single-cylinder direct injection 142 diesel engine. The engine was operated at speeds ranging from 1000 to 2100 RPM and a variety of loads. The radiation was measured using a specially designed fiber-optics probe operating on the two-color principle. The probe was located in the head at two different locations: in one location it faced the piston bowl and in the other it faced the piston crown. The data obtained from the probe was processed to deduce the apparent radiation temperature and soot volume concentration as a function of crank angle. The resultant profiles of radiation temperature and of the soot volume concentrations were compared with the predictions of a zonal heat radiation model imbedded in a detailed two-zone thermodynamic cycle code. The agreement between the model and the measurements was found to be good, both in trends and in magnitudes.