Determination of the medium-speed diesel engine thermal state taking into account the coolant boiling

Abstract

The most important direction of the medium-speed diesel engines development is to increase their power values. The forcing diesel engines by increasing the mean effective pressure leads to an increase in the thermal factor of the engine parts. High temperatures of the cylinder cover fire deck and the cylinder liner working surface cause thermal fatigue cracks in these parts as well as piston scuffing. Thus, the development of both new methods of intensifying heat transfer in cooling gallery and new methods for determining the engine parts thermal state is needed to decrease the thermal factor of the cylinder covers and liners. In this case, the controlled coolant boiling can be used as an effective method for local cooling. This paper presents the developed method for determining the temperature field of diesel engine taking into account the coolant boiling as well as the results of calculating the thermal state of the D500 medium speed diesel engine. Based on the results obtained, the thermal factor of the main engine parts was estimated. It is noted that the boiling is fully developed in some regions of the cooling system while the transition to the film boiling is not carried out since the heat fluxes do not reach critical values and there are no stagnant flow zones. The recommendations for normalization of the thermal state of the cylinder cover for forced working processes are formulated.