В статье рассмотрена методика проведения теоретического исследования гидродинамической смазки юбки составного поршня, и влияние на нее конструктивных параметров деталей поршневой и кривошипно-шатунной групп.
The article describes the features developed by the authors of the profiling method of the piston skirt, provides the main parameters that affect the lubrication conditions of the piston skirt and the magnitude of mechanical losses. In computational studies, the basic formulas are given for determining the thickness of the oil layer in a piston skirt - cylinder sleeve conjunction to assess the nature of friction. To determine the deformations, the finite element method is used on the spatial model of the piston. To verify the finite element model, a stand for experimental studies was developed. The article describes the developed stand, the methodology and results of experimental studies of the stress-strain state of the two-piece piston skirt obtained at this stand and a comparative analysis of the results of the calculated and experimental studies of the stress-strain state of the two-piece piston skirt of a diesel engine. The research results showed that the developed stand can be used to verify mathematical models for calculating the stress-strain state of the piston skirt in the pilot production of internal combustion engine pistons to accelerate and reduce the cost of the piston design development process, as well as the results of experimental studies obtained at the stand, can be used as initial data for the developed mathematical model of the dynamics of the movement of the piston and the profiling of the piston skirt.
The performance of a diesel engine has been studied using well-known types of ceramic thermal insulating HIC or thermal barrier TBC coatings. This problem is relevant for a diesel engine with low thermal losses of the combustion chamber, in which the intense radiant component (in the near-IR range) reaches ∼ 50 % of the total heat flow. In this paper, the authors continued to study these coatings, but as translucent (SHICs or STBCs) with bulk absorption of penetrating radiant energy. The spectrophotometric modeling of the optical parameters of these coatings made it possible to estimate the characteristics of the temperature field being formed with a reduced near-surface temperature gradient (compared to opaque coatings), causing a significant decrease in heat loss through the heat-insulated piston. A translucent STBC coating based on partially stabilized zirconia (PSZ ceramics ZrO2 + 8 % Y2O3) was chosen, determining the formation of the optimum temperature profile in the piston head. For bench testing was used experimental single-cylinder tractor diesel. With a rotation frequency of n > 2800 1/min, the heat loss did not exceed 0,2 MW/m2 through the bottom of the piston with the heat-shielding layer. The tests performed showed a lower specific fuel consumption of ∼ 2-3 % in comparison with the combustion chamber of a diesel engine with an uncoated ceramic piston. At the same time, torque and effective power increased by ∼ 2-5 %.
An overview of the advantages of an engine with the ignition of a lean homogeneous mixture from compression (HCCI), among which, above all, economic and environmental indicators are presented. There were considered the disadvantages of this engine, hampering the release of batch production, and the main is the difficulty in providing in the combustion chamber the conditions for self-ignition of the working homogeneous mixture near TDC in the entire range of engine operating conditions. The ways of solving the problems of controlling the ignition of the working mixture in the combustion chamber, reducing the noise level and fighting the occurrence of shock loads with increasing load, starting the cold engine and improving the engine with the HCCI process are presented. The main ones can be a combination of distributed and direct injection using variable valve timing and exhaust gas recirculation, the joint use of controlled turbocharging and exhaust gas recirculation, a change in the heating of the working mixture at the inlet to the engine, external and internal exhaust gas recirculation (EGR) phases of gas distribution, regulation of the chemical composition of fuel and changes in the intensity of heat transfer and the dynamics of temperature growth in the cylinder, primarily due to changes in the piston crown temperature. The results of computational studies of the influence of various parameters on the process of ignition of a homogeneous mixture on compression are presented. It is established that the greatest effect on the process of homogenization of the air-fuel mixture is caused by an increase in the surface temperature of the bottom of the piston. Reducing the diameter of the fuel droplets from 0.1 mm to 0.03 mm results causes an increase in the relative mass of evaporated fuel by a factor of 2. Increasing the temperature of the fuel at the inlet also effectively increases the relative mass of the evaporated fuel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.