STATISTICAL MODELING OF THE TURBULENT STRUCTURES FORMATION IN THE LIGHT OF THE DROP DISPERSION

Abstract

Methods of mathematical and numerical modeling of reacting open media in the presence of combustion are widely used in various fields of thermal physics, technical physics, and heat power engineering. Owing to the optimization of computing resources, the required degree of accuracy and quality of the results obtained, and easy manipulations to adapt the program to the task at hand, it became possible to model complex dissipative structures without large computational costs. In this regard, methods of computer modeling of the evolution of open systems have become widespread through the optimization of the stages of simulation of a virtual prototype. Such random processes as collision of many drops, turbulent dissipative structures, changes in the cavitation flow inside the injector, etc. promote the process of disintegration of liquid filaments into droplets that interact with a resting gas medium. Then the question arises whether the probability of droplet size distribution matters when the temperature gradient exceeds a certain critical value and an ordered macroscopic motion, which is called convective, arises in the liquid. Because of the complexity of this phenomenon, it is difficult to identify clearly dominant spray mechanisms according to the characteristic droplet size. In such flows, nonequilibrium phase transitions appear, which are expressed in the formation of new dissipative structures. In dissipative structures, an inflow of energy is possible, which compensates for losses due to dissipation and ensures the existence of more ordered states. Due to the flow of a liquid moving in the combustion chamber, consisting of a large number of drops, collective as synergistic interactions are possible, which are necessary for restructuring the system. Thus, modeling the processes of breakup, dispersion, and evaporation of liquid fuel droplets under various initial conditions is an urgent problem in the evolution of open systems. In this regard, in this work, dissipative structures are described by the nonlinear Fokker-Planck equation, which expresses the temporal and spatial evolution of particles along the radii in approximation to the size of the parent droplet. Also in the work is the discrete model of A.N. Kolmogorov was transformed into the evolutionary equation of the distribution function. The asymptotic solution of this equation is used to simulate the breakup and dispersion of particles, along with the Lagrange model, which is used to describe the dynamics of the spray. The paper presents the data of computer experiments to determine the optimal conditions (injection rate) for the combustion of isooctane, based on a statistical model of particle evolution. As a result of the performed computer experiments, the distribution of temperature, combustion products and fuel vapors along the height of the combustion chamber was obtained. Based on these numerical data, the optimal parameters of the atomization and dispersion processes of isooctane were determined