Numerical Simulation And Optimization On Helical Intake Port For RD190 Diesel Engine

The intake and exhaust system is one of the three major factors that affect the quality of combustion for diesel. The movement of organizational airflow in the system makes a direct influence on the quality of combustion. Therefore, it is of great significance to analyze the airflow movement of intake system and the influence of structural parameters for intake port on airflow characteristics.The helical intake port of RD190 diesel engine was used as research subject. Use reverse engineering technology to build the three-dimensional model of the helical intake port and the tangential exhaust port. The Fluent software was employed in simulating the flow status of intake or exhaust port-valve-cylinder in different valve lift. The macro information of the flow coefficient and swirl ratio under each valve lift was calculated. The traces and the distributing pictures of the velocity in the helical intake port were obtained.By combining the method of three-dimensional CFD numerical simulation and one-dimensional dynamical simulation, the accuracy of three-dimensional CFD numerical simulation was verified. The flow coefficient and swirl ratio calculated by the Fluent simulation were used as input parameters for one-dimensional dynamical model, which established by GT-Power for RD190 diesel engine. Then the external characteristic parameter values were obtained by the simulation. The comparison between the numerical simulation and experiments is verified that the simulated results are accurate.The influence of some structural parameters, such as the shape of the intake valve stem, the valve seat height, minimum cross-section ratio and the spiral wrap angle etc, on airflow characteristics of the helical intake port were analyzed in the way of three-dimensional CFD numerical simulation. According to the analysis results, the inlet port of RD190 engine has been optimized and improved.By analyzing above research results, it can find that changing the minimum cross-section ratio or the spiral wrap angle, the flow coefficient is varied not more than 2.14%. While if change the shape of the intake valve stem or the valve seat height, the variation in the flow coefficient will reach a maximum of 6.88%. However, the effect of the change in the four structural parameters on the swirl ratio is large, which increases the swirl ratio reaching a maximum of 27.24%. The shape of the intake valve stem and the valve seat height has been optimized on the basis of minimal changes in the structure of the original cylinder. The average flow coefficient and swirl ratio has increased 1.49% and 47.32% respectively in the improved inlet port. Meanwhile, the simulation results on the power performance of the improved diesel show that the effective power increased by 1.27% at rated speed of 2400r/min.Therefore, integrating three-dimensional CFD numerical simulation and one-dimensional dynamical simulation is an effective method to optimize the port of diesel engine. The method can also be applied to the design and development on other types of internal combustion engine intake and exhaust systems.