Correction Of Intake Evaluation Parameters Computation And Optimization Design Research Of Double Tangent Intake Ports

As one of the key components of engine intake system, performance of intake ports can have direct impacts on power?economy and emission of engine. In recent years, computational fluid dynamics has been widely adopted in development and research of intake port of engine, and became an important counterpart of steady flow test for intake port performance evaluation. However, research with regard to poor accuracy of intake port simulation, a common engineering problem, has been quite little and no public research results were published. At the same time, traditional research about intake port mainly focused on performance evaluation, while not much attention was paid on the double tangent intake ports, especially effects of new eccentric chamfer structure adopted in this paper on intake performance.Based on forward development of a China V diesel engine, this paper conducted deep research about traditional intake evaluation parameters computation method and optimization design of double tangent intake ports. Firstly, main factors leading to poor simulation accuracy of traditional intake port simulation method was analyzed, and a modified computation method based on porosity model was came up with, and it shows that the new method can effectively improve simulation accuracy of intake port, especially that of swirl ratio. Aiming at the problem that the popular mean value definitions of intake evaluation parameters were complicated and not consolidated, a new definition based on proportion of valve lift section over the whole intake stroke was proposed. The new definition is not only simple, but also can be closely correlated to AVL average value definition, which was validated by 3 sets of steady flow test results.In the meantime, preliminary design of double tangent intake ports was finished and its performance was evaluated using steady flow test; To increase swirl ratio, this paper proposed a new intake port design method based on eccentric chamfer. To see influence of eccentric chamfer on intake properties, 25 intake ports schemes with different eccentric chamfer angles were designed and tested, and it shows that eccentric chamfer produces no effect on flow coefficient; when valve lift is smaller than 6mm, eccentric chamfer can significantly increase swirl ratio, but this influence disappears when valve lift exceeds 6mm; As steady flow test was operated on individual valve lift, and it is impossible to reflect continuity of real engine intake, so this paper adopted transient simulation of intake stroke to see effects of eccentric chamfer on intake properties depending on crank angle, and an accumulation effect was found, which made up the drawbacks of steady flow test and steady simulation. To see whether large torque at low speeds and emission targets were achieved, the first prototype engine was manufactured and tested with engine bench, and it shows that torque at 1000 rpm is 202N?m, larger than target value of 200N?m, and emission also meets its corresponding design target.