MAIN FACTORS THAT INFLUENCE THE THERMAL STRESS STATE OF PISTON ENGINE PARTS

The development of a holistic, effective, and scalable structure of economic management, as well as the introduction of a program to improve the technical level and efficiency of machinery, are two of the most important concepts for the deep reconstruction of the Republic of Uzbekistan's economic process. Vehicles with diesel engines are gradually being introduced to our country's car fleet. Modern diesel engines are being developed by boosting them: increasing the average effective pressure and speed. Therefore, high reliability and service life, fuel efficiency and environmental performance are the main criteria for their quality. Forcing diesels leads to an increase in thermal and mechanical stresses on the main parts of the cylinder-piston group (CPG) (piston, liner, cylinder head), a significant increase in their temperature, as well as the temperature of piston rings and valves. Overheating of components causes the creation of temperature fields with pronounced irregularities in temperature distribution and, as a consequence, the development of thermal strains, which causes the material's mechanical properties to deteriorate, the formation of fractures, and, eventually, the part's destruction. The task of shielding parts from the undue effects of high thermal loads from the working body, or, in other words, the task of designing a diesel engine with reduced heat recovery from the working body, becomes important in this regard. However, creating a highly efficient engine with reduced heat dissipation from the working body is associated with solving a number of other issues, primarily with meeting today's environmental requirements. First and foremost, this relates to the reduction of nitrogen oxides in the combustion products, while at the same time reducing specific fuel consumption. Prospects for the development of the diesel engine industry can be seen in a consistent increase in the specific performance by boosting the mean effective pressure with a simultaneous reduction in combustion heat losses, thermal insulation of the combustion chamber and use of the exhaust gas energy. All these measures are taken in order to bring the actual thermodynamic cycle closer to the theoretical adiabatic cycle. Existing assessments of the effectiveness of combustion chamber thermal insulation of diesel engines on the level of thermodynamic adiabatic cycle were based on qualitative rather than quantitative indicators, due to which the achieved effects were interpreted ambiguously by various researchers. The introduction of uniformity in methodology, metrics, and quantitative parameters for estimating the efficiency of using heat from fuel combustion in a diesel working cycle helps not only to identify the reached stage, but also to forecast future progress of the engine-building branch, demonstrating the problem's urgency.