Study Of Gas-solid Two-phase Flow In Air Filter For Diesel Engine Based On STAR-CD

Air filter is an important component of the diesel engine intake system. Abnormal abrasion,power down and economic performance degradation of the diesel engine are mainly due to large amount of dust in the intake air and the quality of intake air depends on the air filter to a large extent. The internal structure of air filter is complex,so there exists a complex gas-solid two-phase flow,which consists of gas and dust. In order to improve the filtration efficiency of air filter,it is necessary to understand the situation of the gas-solid two-phase flow. Because the experiment to obtain the detailed data of gas flow and trajectories of dust particles inside the air filter spends a lot of time and it can not get internal comprehensive data,the numerical simulation method is put forward to study the internal gas-solid two-phase flow of air filter.On the basis of the researched work,where the single-phase flow in a new type of wet and dry compound air filter for diesel engile was single-phase studied,this thesis carries on further study,and the entrance part and coarse filtration part of the air filter is studied as.In the numerical simulation of gas-solid two-phase flow of the air filter in the entrance part,the numerical simulation of gas flow is carried out firstly,followed by the numerical simulation of gas-solid two-phase flow. In numerical simulation of gas,the boundary conditions of gas flow is determined,and the SIMPLE method is used to calculate the three-dimensional turbulent flow field of gas. In the numerical simulation of gas-solid two-phase flow,the model of dust particles is established,dividing dust particles into 10 groups according to size,and Lagrange method is used to particles trajectories for each group.In the numerical simulation of gas-solid two-phase flow of the air filter in the coarse filtration part,the Pro-star/amm module of STAR-CD is used to establish the computing grid of the coarse filtration part directly. The first,the numerical simulation of gas flow is carried out to obtain three-dimensional turbulent flow field of gas. The second,the numerical simulation of gas-solid two-phase flow is carried out to obtain the trajectories image of dust particles,and then the efficiency of coarse filtration section is calculated for different dust particles in size.In this thesis,the notion of critical grain diameter is put forward. With the help of STAR-CD software,data of any point in the air filter can be obtained,and numerical simulation is rapid,efficient and economical,which experimental methods do not have. Therefore,giving full play to the advantages of STAR-CD software for green design of the air filter of diesel engine is of great significance.