The influence of the valve timing of the intake process on the parameters and indicators of the working cycle in a diesel engine mechanically driven supercharging compressor

The article presents the features of evaluating the consideration of the gas distribution phases of the intake process as parameters of the gas exchange system when determining the effect of the cylinder filling coefficient with a fresh charge on the operating cycle indicators in a diesel engine with a mechanically driven boost compressor. When forming methodological approaches to assessing the effect of valve timing on the indicator indicators of the working cycle by influencing the cylinder filling coefficient with a fresh charge, such features as the modernization of the valve timing mechanism in an existing diesel engine and its development for a newly designed diesel engine are taken into account. As components of the total losses in determining the filling coefficient of the cylinder with a fresh charge, gas dynamic losses are noted, losses from heating the air charge by the cylinder walls, from the expansion of residual gases and from throwing a fresh charge into the intake manifold, and the increment of the filling coefficient due to the additional charge of the cylinder is determined. Numerical modeling of the diesel operating cycle with a change in valve timing was performed in two versions: with an assessment of the effect of the filling coefficient on the operating cycle without taking into account the relationship of the filling coefficient with the coefficient of excess air, the duration of the combustion process and the coefficient of combustion efficiency in conditions of increased fuel consumption and taking into account these relationships while maintaining the same fuel consumption by diesel. The evaluation used methods of computational and experimental study of the working cycle based on algorithms and programs for the thermodynamic synthesis of theoretical indicator diagrams of gas pressure in the cylinder, which resulted in a change in the pressure and temperature of the gas in the cylinder as a function of the angle of rotation of the crankshaft, as well as such indicators of the working cycle as the average indicator pressure, specific indicator fuel consumption, the maximum pressure and temperature of the gas in the cylinder, etc. As a result of the analysis of theoretical pressure indicator diagrams and operating cycle indicator indicators, the insufficiently studied effect of valve timing on the possibility of increasing diesel engine power while maintaining and changing the excess air coefficient has been determined. At the same time, the greatest effect of optimizing the valve timing according to the criterion of the maximum value of the average indicator pressure is noted while maintaining the coefficient of excess air. In this case, it is possible to ensure that the specific indicator fuel consumption and the maximum gas temperature remain unchanged with a slight increase in the maximum gas pressure in the cylinder with an increase in the average indicator pressure of the diesel engine. The effect of optimizing valve timing on the possibility of increasing diesel engine power when changing the excess air coefficient is characterized by a slight increase in the average indicator and maximum pressures, an insignificant decrease in the specific indicator fuel consumption and a slight decrease in the maximum temperature gas in the diesel cylinder.