Numerical Simulation And Analysis Of Three-dimensional Turbulence In Air Filter

Air filter is an important component of the inner combustion engine, and its performance directly affects the reliability and service life of the engine. Due to the constraints of the internal complex structure and operation environment, it is very difficult to fully know the true internal flow characteristics, and it will not only have to spend a lot of time but also can't get its comprehensive flow information if the air filter is developed with the experience and experimental methods. Therefore, the numerical simulation method is put forward to study its flow characteristics in this thesis, which is a basic theory to improve its performance and to prolong its service life.Firstly, the classification for the performance comparison and the air filter are introduced, the characteristics of the air filter in this study is overviewed, the performance and the flow factors to effect wet and dry composite air filter are analyzed.Secondly, the continuity equation, the momentum equation, and the standard k-εtwo equation model are used to build the air filter flow theoretical model, the flow air is supposed as three-dimensional turbulence fluid, and the heat transference between the wall of filter and air is not considered, the FVM is adopted for convection diffusion equation, and SIMPLE algorithm is used for calculation. The basic principles of the numerical simulation software STAR-CD and the CFD simulation steps are introduced briefly.Finally, the Pro-star of STAR-CD is used to construct the computing grid of fine filter directly. The porosity, the convergence criteria and the boundary condition parameters are set, the flow field is simulated, and the results are analyzed.The results show that the uniform flow of air filter is affected significantly by the location of the entrance; the best uniformity location of the flow is the 160mm distance between the location and the export. The circular entrance is better than the rectangle entrance in the same position, because it can decrease the pressure loss of the filter, which will improve the flow performance. With the diameter of the export increasing, the pressure loss becomes smaller, but the connection size between filter and the engine should be taken into account, which can not be increased too much. With the porosity decreasing, the velocity distribution becomes uniform, but the pressure drops dramatically. Therefore, the various factors to affect its performance must be considered. When the distance between the location and the export is 160 mm, the entrance circle, and the export diameter is 140 mm, the porosity is about 0.65, the structure and the operating parameters of air filter is the best.This thesis provides a theoretical basis in the reduction of blindness, the structural optimization of the air filter, high efficiency, low cost, superior quality design and the improvement of its overall performance.