Моделювання в САПР нестаціонарних термічних навантажень та ресурсної міцності поршнів швидкохідних дизелів

Abstract

Thesis for the science degree of the Candidate of technical sciences by specialіty 05.05.03 – engines and power plants. – National Technical University "Kharkov polytechnic institute", Kharkov, 2018. The thesis is devoted to modeling in CAD of non-stationary thermal stresses and resource durability of pistons of high-speed diesel engines. The dissertation is devoted to the modeling of non-stationary thermal loads and resource strength of high-speed diesels in CAD. It has been found that for modeling the thermal state of the piston in the transient processes diesel, it is necessary to use non-stationary models of operation. In this case, when the boundary conditions are imposed, it is necessary to have data on control functions that including the time of the transition process. The allowable simplifications of the border conditions problem in the characteristic zones of the piston in the calculations of the thermal and thermo-stressed state of the piston on the stationary and in the transient processes of the diesel load are determined. Their use allows to shorten the design time without violating the concept of guaranteed maintenance of the resource of the edge of the combustion chamber in the initial stages of CAD application. An experimental study was conducted to determine the thermal of a piston for a 4CHN12/14 diesel engine in transient diesel processes. According to the study, control functions are defined for each transient process. A complex of mathematical models for the determination of the thermal and thermo-stressed state of the piston in the transient processes of the diesel is proposed. With simplified border conditions, the reliability of the results proposed to set the indicator of the relative estimated increase in the resource. According to the results of the research, the effect of the shift in time of the step change of the BC of the 3rd kind of a piston in the transient process of the diesel engine on the resource strength of the edge of the combustion chamber is established. This measure allows to increase the efficiency of CAD on stationary and non-stationary loads and when performing the evaluation of the resource strength of the pistons. New designs of pistons with oil-cooling cavities are proposed.