Thermal tension of cylinder covers of transport diesel engines converted to marine diesels

Abstract

The article describes the characteristics of thermal loading of the cylinder covers of transport diesel engines during their conversion to marine diesels. The engines of the CHN14/14 type produced by the Yaroslavl Motor Plant are proposed as promising for use in marine power plants. A special feature of the engine design is the individual four-valve cylinder heads, which have a complex geometric shape. The conversion of automobile engines, the cylinder heads of which were made of aluminum alloys, to marine ones is accompanied by an increase in the degree of their acceleration. The cylinder heads in operation experience significant thermal and mechanical loads, which causes the need for increased requirements for the materials of the cylinder heads. The rational choice of the cylinder head material is one of the most important tasks to be solved when upgrading and boosting engines. Experience in the operation of marine diesel engines shows that in order to ensure the required reliability under prolonged exposure to elevated temperatures due to forcing, it is necessary to choose cast iron as a structural material. A three-dimensional model of the cylinder head is developed. When performing the calculations, the boundary conditions are justified, taking into account the local nature of the distribution of thermal and mechanical effects on the diesel cylinder head. As a result of numerical modeling, the stress-strain states of cylinder heads made of high-strength cast iron, ductile iron and cast iron with vermicular graphite are determined and analyzed. There has been proved the preference for using cast irons with vermicular graphite, which have satisfactory casting and physical and mechanical properties. The advantages of using cast iron with vermicular graphite include a decrease in the temperature of the cylinder head in the area of the inter-valve bridge. The possibility of increasing the engine power from 330 to 560 kW when replacing aluminum alloys with cast iron with vermicular graphite for the manufacture of cylinder heads is proved.