Numerical Simulation On Evaporation And Combustion Of Sprays And Some Priori Analysis

The evaporation and combustion of sprays has wide applications in industrial area, suchas internal combustion engines, gas turbine engines, liquid-fuelled rocket engines, as well asin liquid-fuelled industrial burners. At the same time, the evaporation and combustion ofsprays is a complex physical-chemical phenomenon, which involves the problems than can befound in turbulent flow, muti-phase flow and combustion process, and the problems caused bythe interaction between these basic processes. Therefore, the study on the evaporation andcombustion of sprays can make great difference in practical applications as well as infundamental research.The current models of evaporation and combustion of sprays faces many problemsbecause of its complexity. Making deeper research on the micro-processes in sprayevaporation and combustion phenomenon to improve and extend the son models of the modelof evaporation and combustion of sprays, is an effective approach to improve its predictingperformance. The work of verifying the validity of son models, improving their accuracy,extending their application, establishing new models for new parameters can be called prioristudy of modeling evaporation and combustion of sprays. In this article, the priori study onturbulent model in strong vortex flow, the son model of heat and mass transfer betweenphases, the mutual interaction between droplets in dilute burning sprays is made.Firstly, a test stand, which is suitable for laser measurement, is built to investigate theflow field behind the oil burner, using PIV system. The measuring results are compared withthe results of numerical simulation to evaluate the predicting performance of turbulent models.Some quantitative dates and global understanding of the flow field behind the burner isobtained through the experiment. The RNG k-turbulent model has the best predictingperformance compared with measuring results.Secondly, a mathematical model for a single droplet in convective surroundings withhigh temperature is established based on the basic conservation equations. The phenomenonof the internal circulation within the droplet, the layer flow in the gas phase is taken intoaccount in the model and numerical method is adopted to solve the problem based on theMatlab software using self-making program. The influence of gas phase temperature, surrounding pressure, and initial radius on the evaporation and combustion of droplet isstudied and the son model of heat and mass transfer between phases in common CFD packageis analyzed and evaluated. The simulation results reproduce the transient process of the flameof droplet. The regulation of the influence of gas phase temperature, surrounding pressure,and initial radius on the evaporation and combustion of droplet is also obtained. The resultsshow the shortage of the son model of heat and mass transfer between phases in commonCFD package.Thirdly, double-droplets models which are arranged to be perpendicular with gas flowdirection or to be parallel with gas flow direction in convective surroundings are built andsolved using CFD package Fluent, to investigate the mutual interaction between adjoiningdroplets. The result shows that: the transient process of the flame of double-droplets is similarwith that of single droplet; the interaction between adjoining droplets is always strong nomatter how the droplets are arranged and the interaction of parallel configuration is strongerthan that of perpendicular configuration; the interaction between adjoining droplets can betaken into consideration if droplet group model is introduced into the spray model.