Study On Steady Flow Testing Of Intake Port And Simulation Of Air Flow In Diesel Engine

In the engine design process, two dimensionless parameters: the discharge coefficient and the swirl number, have great influence on the performance of fuel economy and exhaust emission of the diesel engine. Computational Fluid Dynamics(CFD) simulation, which can reducing cost of design and cutting the development cycle of engines,is an important method to study performance of the port in IC engine. Traditionally,steady-state flow rigs are extensively used in the design of intake ports for diesel engines, which was performed to evaluate the fluid dynamics of intake port. But experimental method can only offer global parameters; it is not able to get the detailed information about the in-cylinder flow structure. The design heavily relies on the designer's intuition and experience. However, as the complexity of the engine structure and more stringent emission regulations and fuel economy requirements having to meet, it makes the port development task more difficult. It requires designers to understand and control the detail of the flow. CFD based on numerical simulation have recently made it possible to study the development of such engine flows in great detail, which can provide the information about the fields of pressure and velocity and how the structure parameters influence the flow pattern characteristics for the design and improvement of intake system. By this time a combined use of both the available approaches, the experimental and the numerical one,is considered to be essential for a further intake systems improvement along a deeper insight in the related fluid dynamics. Only a close interaction between these two approaches can help in overcoming the respective limits. In this paper, study was carried out on the intake port of the diesel engine. A series of steady state testing have been performed for different valve lifts. The port data form laser measuring instrument was handled with reverse engineering software Geomagic, an intake port model was gained. Then the geometry model including the port, valve and cylinder for the simulation was built with three-dimension modeling software CATIA. The computation was carried out by the CFD code FIRE on steady state test bench and real operating condition test rig. Steady state tests were performed to evaluate the global fluid-dynamic of intake system, in terms of flow coefficients and swirl ratio. The pressure drop and the theoretical basis of non-constant pressure flow testing were discussed in detail. A new generating method, combination of mesh generation, is proposed for steady state simulation. It split the whole geometric model into different parts, and mesh them using automatic mesh generating, then combine them...