DETERMINATION OF LOCAL HEAT TRANSFER COEFFICIENTS AT THE PISTON OF A HIGH SPEED DIESEL ENGINE BY EVALUATION OF MEASURED TEMPERATURE DISTRIBUTION

For different operating conditions of a high speed Diesel engine the steady state temperature fields in the piston were measured and evaluated by use of the relaxation method and the electrolytic tank analogue. Thus the local heat transfer coefficients at the contour of the piston could be determined. To obtain in spite of the weakness of the method, that 20 measured temperatures are not sufficient to define exactly the temperature field, reliable results, different test series were carried out with extremely altered cooling conditions at the piston. More than 60 temperature fields were evaluated thus determining the heat transfer coefficients at the piston crown, the bottom side, the cooling channel and at the piston rings.