An Investigation On Modeling Of Diesel Engine Spray Coupling The Flow In Injector

The computer simulation of the diesel fuel injection system has been the most important way for designing and optimizing the fuel injection system. For a long time, the simulation study of the common rail fuel injection system has focused on the response characteristics of solenoid and electrical control unit (ECU). However the transient flow in injector and the heavy turbulence and cavitation flow in nozzle hole have also been important aspects. Thus, more recently, emphasis has just shifted to the modeling of the detailed injection nozzle cavitating flow and its connection with the behavior of subsequent events such as the fuel atomization and spray characteristics. The nozzle flow, its upstream flows and its subsequent spray are a uniform system, so it's very necessary to carry out the detailed numerical simulation and study of spray coupled with numerically simulating nozzle flow. On the one hand, it can provide more realistic boundary conditions for the spray model, on the other hand, it's easier to analyze the effect of the whole fuel injection system on the fuel spray atomization and combustion process.This paper reviewed and summarized the recent progress of the fuel pray atomization at home and abroad. The developmental situation and trend of the numerical simulation of the fuel pray atomization have also been analyzed fully and systemic in this paper. A study on numerical simulation of spray coupled with numerically simulating nozzle flow has been performed. The main content is focused on a new method of numerical simulation of the fuel spray.A three-dimensional model of cavitation flow in nozzle was developed and the detail simulation on transient cavitating flow inside STD four-hole diesel injection nozzle is dealt with using CFD software STAR-CD. This paper uses moving mesh so the computed results can show the cavitation distribution inside injection nozzle with different needle valve lifts. The effect on the flow field inside injection nozzle and the outlet of cavitation has been analyzed. At the same time, the mass flow rate of role outlet has been gained to be the initial condition for the spray model that the spray model's boundary conditions will be more realistic. The gas-liquid phase turbulent model of fuel injection is developed for the spray to investigate the effect of injection pressure, gas temperature of cylinder and hole diameter on the development of spray. All above supplies theoretic fundament for optimum gas kinesis in cylinder and fuel mixing and combustion.On the basis of these, a visualization unit for spray in diesel has been developed. By means of high-speed video camera, the pictures of the spray in combustion chamber are taken under various injection pressures. These pictures worked are combined with the numerical simulation to verify the trueness of numerical simulation results of cavitating flow in the nozzle and spray.