Numerical Simulation Study On Intake Port Of Gasoline Engine

Intake and exhaust port are the key parts for the mobile engine,and the flow characteristic of intake port has sensitively influence on engine,including economy performance,dynamical performance and the level of injurant emission. The intake flow characteristics are sensitively influenced by the changing in shape and size of the key position of a intake port,the effective way to improve the engine power is to enhance the flow coefficient and to reduce the inlet flow resistance,so it is important to optimize intake port structures for the improvement of engine performance. Lately,more and more requirememts for engine make the quality of the port to be improved.Traditionally , steady-state flow rigs are extensively used in the amelioration of intake ports for engines, which was performed to evaluate the amelioration effect of intake port. But experimental method can only offer global parameters , these results can only token the macroscopical performance of the flow,it can't provide more information for theimprovement of the port,it is not easy to get the detailed information about the intake flow structure. The amelioration design heavily relies on the designer's experience and intuition. Therefore,the amelioration cycle has been enlarged,and it's very difficult to make a ideal design plan. CFD technology can be used to solve this problem by simulating the intake flow in the intake port which is modeled in CAD software. It can provide three-dimensional flow structure details in the intake port model. It turns out to be quicker to find out the bad flow areas more accurately. So it takes less time and money to obtain a good amelioration plan. It's evidenced that the combine of using steady-state flow test and CFD simulation is an effective way to amend intake ports.In the medium and late term of 1980s,tumble was found in the cylinder,its application particular in multi-valve engine has been the subject of extensive attention. Because it could substantially increase dynamicalperformance and economy performance of the gasoline engine,reduce injurant emission at the same time. The researchers found that the flow coefficient of multi-valve engine in the intake process have been greatly heightened,and the tumble in cylinder was the important reason of improving the performance of the engine,all these indicated that the tumble is more effective to the performance of the engine compared with the swirl.In this paper,the steady-state flow rigs tests for an original intake port has been carried out to get the flow coefficients at different valve lifts. The tests were under a steady pressure drop. And flow coefficients of these tests are measured to evaluate the flow capacity.Using CAD software Pro/E,the intake port model was set up and amended.Numerical simulation was carried out on steady-state flow test of original engine. The flow coefficient and three dimensional flow features such as pressure fields,velocity fields and turbulent kinetic energy values were obtained as simulation results. It was qualified that the simulation results were coincide with test results. Figure 1 is contrast of test and computational flow coefficients.Figure 1 Contrast of test and computational flow coefficients.Three-dimensional numerical simulation can provide a more accurate and visual internal flow of the intake port,through the analysis,the factors of influencing the flow forms and the specific influencing rule are found. Use the numerical simulation results of the intake port steady-state flow to discover the influencing factors of the intake flow of the engine,conclusion is given as below: while the valve lift gradually become bigger,the average inlet velocitygradually become bigger;the velocity of the location of the inlet valve throat gradually become smaller;the average inlet absolute pressure gradually become smaller;the average absolute pressure of the location of the inlet valve throat is not too much change;the average inlet viscosity resistance gradually become bigger;the average viscosity resistance of the location of the inlet valve throat gradually become smaller;the radius of the tumble gradually become smaller,the tumble in cylinder become homogeneous,and in favor of forming homogeneous mixture.The angle of the valve seat of the original engine is 15 degree,change it to 30 degree and 60 degree respectively,and compare with the one another's changes of the flow,conclusion is given as below: the changes of the valve seat's angle have not too much influence on the intake flow coefficient,especially under the circumstance of the big valve lift;while the angle of the valve seat gradually become bigger ,the maximal inlet velocity gradually become smaller;the maxima inlet absolute pressure gradually become bigger;the maximal inlet viscosity resistance gradually become smaller;there is not too much influence on the tumble in the cylinder.Through the wedgy combustion chamber simplify respectively on the qualitative study of the inlet flow combustor flow and the formation of the tumble,conclusion is given as below: while the angle of the chamber gradually become bigger,the velocity of the location of the inlet valve throat gradually become smaller;the angle between the flow through the upper location of the inlet valve throat and the cylinder axis gradually become bigger,the Tumble in the cylinder become more homogeneous. And in the actual engine design process, the compact structure should also take into account.Intake port,cylinder,piston and exhaust port modal can be built on the base of this paper,how they influence the flow field of intake port and cylinder,and provide effective guidance to the overall improving of the performance of the engine.These applications are very important.