Modeling of the processes of evaporation and mixture formation in the cylinder of a tractor diesel engine when working on an ethanol-fuel emulsion

Abstract

The article is devoted to the problems of modeling the processes of evaporation and mixture formation in the cylinder of a tractor diesel 4Ch 11.0 / 12.5 with a combustion chamber of the TsNIID (Central Research Diesel Institute) type when working on ethanol-fuel emulsion. In a diesel engine 4Ch 11.0 / 12.5 with a combustion chamber of the TsNIIDI type, when working on an ethanol-fuel emulsion, a volume-film mixture takes place with the predominance of evaporation of the fuel prior to the start of the combustion process. The evaporation of fuel depends not only on the dynamics of the motion of the medium and the temperature conditions, but also on the characteristics of injection and spraying. The speed and turbulence of the mixture are important characteristics. Therefore, the above parameters determine the intensity of evaporation and mixture formation. During the evaporation of droplets of ethanol-fuel emulsion and diffusion into the surrounding vapor-air medium, a combustible mixture forms. It does not ignite the fuel itself, but its vapor mixes with air. The constructed model takes into account the peculiarities of evaporation and mixture formation during the spraying of fuel and allows us to accurately calculate their speed. In regions where the concentration of droplets is low, calculations are made for one drop, and in zones with a high concentration, the interaction between the drops during evaporation and combustion is taken into account. In order to better understand the nature of the interaction of droplets with each other and with the surrounding turbulent gas flow, the entire combustion process is divided into stages: the formation of aerosol particles, the movement of droplets, their evaporation, mixing with the oxidant, ignition and combustion. The following basic assumptions are also accepted: there is a spherical symmetry of drops; The thermal conductivity coefficient, the specific heat are constant and do not depend on temperature; there is an identity of heat and mass transfer processes; the quasistationary nature of the process takes place.