Method of calculating the heat and stress-deformed state of the cylinder head of a transport diesel with liquid cooling

Abstract

In an internal combustion engine (ICE), stresses arise from the action of a variable gas force and from a variable temperature due to the combustion of fuel in the combustion chamber in the cylinder head and piston, while the thermal stresses are much higher than the stresses from the power load. Therefore, at the design stage of a new engine design, they are calculating the durability of heat-stressed parts, since they limit the reliability of a piston engine. The paper discusses the method of selecting source data when calculating the thermal and stress-strain state of the cylinder head of a diesel engine using the finite element method and using the Solid Works software package. The stages of creating and preparing a solid model of a cylinder head to create a finite element model are described using the example of the 8ChN12 / 13 diesel engine (KAMAZ 740.75-440). The main loads acting on the cylinder head during the assembly period are considered: efforts from pressing in valve seats and bushings, as well as from tightening the bolts for fastening the head to the crankcase. The shape of the elements for the finite element model of the cylinder head was chosen from the condition of reducing the estimated time. This condition was suited to the shape of a finite element in the form of a tetrahedron with four nodal points. These elements made it possible to reduce the computational grid in cross sections, for example, stress concentration. It is shown that high-frequency temperature fluctuations that occur as a result of the flow of the working process of a piston engine do not affect the thermal strength of the cylinder head, and high-frequency temperature fluctuations due to changes in the engine operating conditions affect. The changes in the basic characteristics of the aluminum alloy from which the cylinder head is made with temperature and cyclic thermomechanical loading of low frequency are given. It is shown that with increasing temperature, the endurance limit of the material decreases at low frequency loads.