INFLUENCE OF CONSTRUCTIVE FACTORS ON THE HEAT CONDITION OF THE CYLINDERS

Abstract

The optimization of the thermal state of the cylinder sleeve in the study involves equalizing the temperature of its working surface in the area of operation of the compression rings to a certain level at which the optimum viscosity of the engine oil is achieved and the mechanical losses in the conjugation of the piston-sleeve are reduced. The use of aluminum alloys with a higher thermal conductivity than the materials of most serial sleeves - pig iron MH is considered as the main means of temperature equalization. The wear resistance of the working surface of the sleeve is ensured by the corundum coating. The results of the nonmotor experiment for the determination of the heat-insulating effect of the coating, the results of calculations of the thermal state for variants of aluminum alloy casings with corundum coating are given. Calculations are performed using a mathematical model based on the finite element method. It is shown that the use of an aluminum alloy AL19 with high thermal conductivity in the working temperature range allows for a significant reduction of the temperature in this most thermally stressed zone (from 278 to 214 ° C) due to more intense heat removal from the upper belt of the sleeve. The decrease of temperatures by 30-50 ° C is also observed in the adjacent zones of the working surface. At the same time, the insulating effect of the corundum layer is insignificant and evaluated within 2-5 ° C. Therefore, such a layer with a thickness of 0,2-0,3 mm is considered only as a means of protecting the working surface from wear. In addition, the results of the study show that the friction zone of the compression rings still remains supercooled (158-102°C), especially near the lower seating belt. Solving the problem can be applied to the outer surface of the sleeves of enamel or other coatings that have a significantly lower thermal conductivity.