Heat transfer process in a piston ring of an internal combustion engine is considered. Heat fluxes from the piston and a cylinder liner as wel as frictiongenerated heat are taken into account. because of the ring deformation heat is not uniformly distributyed along the ring circumference and friction-generated heat is added to the ring primarily through the contact sections betweent he ring and a cylinder liner. An equation for the average temperature for the ring cross section is derived and solved by presenting the solution as Fourier series. The obtained results show the distribution of instantaneous and local as well as an average for a cycle temperatures in a ring cross section as functions of engine parameters and a number and size of sections of contact between the ring and a cylinder liner. It is shown that the considered problem is a boundary layer type problem. Estimation of the thickness of a boundary layer formed on the boundaries of the sections with different temperatures as well as investigation of the influence of significant parameters ont he boundary layer is performed. It is shown, that due to partial contact between the ring and a cylinder liner the level of temperatures is high enough to be responsible for the microwelding phenomenon between the piston groove and the piston ring surface that is observed in a number of studies. It is also shown that when the contact surface between the piston ring and a cylinder liner reduces under 45-50percent, the increase in temperature is relatively slow and can be described by a linear function. The temperature increases much faster as farther reduction of the contact surface between the piston ring and a cylinder liner takes place. An example of calculations for the particular internal combustion engine is presented.
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