Physical and Numerical Modeling of Thermomechanical Processes in Gas-Air Systems of Piston Engines Under Gasdynamic-Nonstationarity Conditions

摘要

It is well known that as of today, internal combustion engines are the most widespread energy sources among heat engines. Therefore, one relevant problem in the development of world energy is to improve operating processes, and also to modernize systems and elements of piston internal combustion engines with the aim of improving their technical and economic indices. In the present paper, the authors have given new information on nonstationary gasdynamics and local heat transfer of pulsating flows in gas-air flow ducts of internal combustion engines, and also have proposed methods for improving the processes in intake and exhaust systems. Experimental investigations were conducted on full-scale models of a single-cylinder internal combustion engine with supercharging and without it. Physical features of pulsations of gas flows in the engines ' gas-air flow ducts have been described. Calculated and experimental dependences of the change in the instantaneous velocity and the pressure of the gas flow in the gas-air flow ducts with time have been presented. Particular emphasis was placed on an analysis of the intensity of heat transfer in gas-air flow ducts of different configurations. It has been shown that lateral profiling of intake and exhaust pipelines exerts a positive influence on the technical and economic indices of piston engines without supercharging. A method to reduce pulsations of the pressure and velocity of gas flows (on the average, by a factor of 2) in the intake pipeline of a supercharged internal combustion engine has been proposed, which leads to an improvement of the reliability of the entire engine.