Simulation of combustion process in the forced transport diesel engine with the prescribed law of mixture formation

Abstract

There was developed a new single-zone model of the fuel combustion process, based on the equations of chemical kinetics, which takes into account in more detail the features of the internal chamber processes of internal combustion engines. The combustion process is considered as a set of successive oxidation reactions to carbon dioxide and water of groups of active fuel molecules proceeding according to the Arrhenius law. The number of active molecules of fuel entering into the reaction depends on the total number of fuel molecules, the current mixture temperature and the conditional activation energy, varying depending on the fraction of burned fuel. The conditional duration of oxidation of this group of active molecules is assumed to depend not only on the total number of fuel molecules, but also on the volume of the combustion chamber, the number of oxygen molecules, the number of molecules of inert components and turbulence inside the combustion chamber. The heat released during the oxidation of each group of active fuel molecules is determined through the lower heat of combustion of the fuel and is expended to increase the temperature and pressure of the mixture in the combustion zone. At each step of the calculation, the number of molecules of all substances is corrected as a result of fuel burn-out. A special feature of the model is the introduction of a new parameter that takes into account the time factor at the molecular level, the conventional duration of the oxidation reaction of the active molecules of the fuel. A new mathematical model is used as the basis for the algorithm for the developed program for calculating the operating cycle of an accelerated diesel engine with a prescribed law of mixture formation. Calculations of the influence of the temperature of the fresh charge after the charge air cooler on the duty cycle of the forced diesel in the range from 360 to 430 K are performed. According to the results of the calculation, it is established that the best indicator characteristics of the working cycle are reached at a temperature of 360 K. Indicator diagrams of pressure in the cylinder and the laws of heat generation, obtained by calculation correspond with known experimental data.