Mechanisms Of Breakup And Atomization Of Liquid Jets And Process Simulation In Cylinder Of Internal Combustion Engine

In fact, the process of fuel breakup and atomization is a kind of instability phenomenon of the liquid jet. In order to increasing the oil surface area and promoting efficient combustion, the instability process of the jet is always used to make the fuel atomization in engineering. So studying on the mechanisms of breakup and atomization of a jet is not only important on theory but it owns the engineering background. This thesis conducts a theoretic and numerical investigation on the mechanisms of the breakup and atomization of viscous liquid jets, and the results that obtained from this studying are applied in the process simulation in cylinder of the internal combustion engine. The following terms have been finished.1. The detailed review of the previous works on the stability analysis of liquid jets and it's breakup and atomization are given, in addition, the fuel atomization models in cylinder of the ICE are introduced in this dissertation.2. The model of viscous liquid round jets is extended, namely, it includes the action of the gas viscosity in the breakup and atomization process, and in such way that makes the model of the jet more consummate. Based on the linear analysis method, the dispersion relation is obtained which delineates the evolution of a general 3-dimensional disturbance on the free surface of a viscous liquid jet. The manually deduced dispersion relation has been verified by means of the computer algebra software MATHEMATICA.3. For above obtained dispersion relation, comprehensive numerical analysis has been carried out, and so as a certain number of operating mode. By numerical simulation, a critical Weber number(We_2c=1) is first found in this dissertation, which can be as a criterion to distinguish the breakup and atomization of viscous liquid jets. When Weber number We₂<1, the process of viscous liquid jets is in the case of breakup, while We₂>1, it shows the behavior of atomization. By combining theoretical analysis and numerical results, formulas are obtained to compute the intact breakup length and the mean radius of the jet.4. The model of viscous liquid annular jets is also promoted, namely, 3-D model of an annular liquid jet surrounded by swirling airstreams has been established. Themanually deduced dispersion relation that delineates the evolution of a general 3-dimensional disturbance on the free surface of a viscous liquid jet has also been verified by means of the computer algebra software MATHEMATICA.5. For the dispersion relation of the viscous liquid annular jet, comprehensive numerical analysis has been earned out, and actions of many parameters on the low-speed and high-speed jet have been compared in this thesis.6. The results, which are obtained from the studying on the mechanism of viscous liquid round jets, are applied in the simulating for a high-speed 4- cylinder diesel engine, and the properties of this diesel engine are experimented in the dissertation.