Study On The Breakup Breakup Mechanism And Atomization Characteristics Of Fuel Jet In High Pressure Heating Environment

The energy exhaustion and environmental pollution have become two major problems which were troubling the world development.With the urbanization process and the improvement of living conditions,the consumption of motor vehicles is increasing.A large amount of fuel is consumed every day,and the exhaust gas emitted in the process of driving will produce haze which has a serious impact on the environment and even endangers people's health.Therefore,reducing engine emissions has become a major concern.As one of the automotive engines,the direct injection diesel engine is one of the power machines which has higher thermal efficiency so far,and the fuel jet splitting atomization process plays a crucial role in improving the performance of diesel engine.Although many studies have been carried out on the atomization mechanism of liquid,due to the complexity of the diesel combustion chamber environmental conditions,the cognition of diesel atomization splitting process under high temperature and pressure environment is still not comprehensive.Thus,it is very necessary to carry out the research on fuel atomization under the condition of more extreme high contrast pressure and temperature,which will comprehensively deepen people's understanding of diesel atomization mechanism and provide theoretical basis for the research and development of advanced diesel engines and other thermal power devices.Firstly,the atomization mechanism of fuel jet splitting in hot atmosphere is studied by theoretical analysis.Taking cylindrical jet as the research object,the temperature distribution on gas-liquid interface was solved under the condition of jet viscosity,and then the spatial distribution of surface tension along the jet axis was obtained.The spatial distribution model of surface tension and the circular jet transport model were combined to obtain the dispersion equation under the high pressure thermal environment.By solving the dispersion equation with Müller method,the distribution of fluid properties such as temperature and surface tension at the interface and the relationship between the growth rate of jet surface wave and wave number are obtained.The effects of Re number,ambient contrast temperature,gas density,jet diameter and angular modulus on the growth rate and dominant wave number of surface waves were analyzed by using the linear stability theory,and then the influence law of the surface tension change on the crushing behavior of fuel jet after entering the thermal atmosphere was obtained.The high temperature/pressure constant volume bomb and high speed photography were used to study the spray development process in hot atmosphere.Taking parameters such as reduced pressure,reduced temperature,injection pressure and nozzle diameter as research variables,multiple groups of spray images were obtained.Based on the analysis of the reduced pressure,hot atmosphere environment factors such as temperature,injection pressure and nozzle hole diameter change throughout throughout the spray distance and speed through features such as,the influence of hot atmosphere environment is studied in the injection parameters and environmental parameters on spray spreading area,the influence of the spreading properties such as the spray cone angle,with the aid of the experimental results we compare the classic atomization model and a fix was obtained under the condition of high pressure hot atmosphere environment experience model of fuel atomization.The schlieren method was used to measure the variation of the fluid density of the spray and its surroundings.Several working points of high ambient pressure and temperature were selected to study the change rule of high pressure and temperature on the structure distribution characteristics of spray gas-liquid phase.With the help of parameters such as liquid phase relaxation time and fractal characteristics,the structure distribution characteristics of gas and liquid phase were quantified.By comparing the liquid phase relaxation time with the jet crushing time,a relatively complete influence mechanism of the contrast pressure/temperature on the atomization process was obtained by combining theoretical analysis and experimental research.