Three-dimensional Transient Simulation For Intake Port Flow Characteristics Of Marine Diesel Engine

The airflow inside the cylinder plays an increasingly important role in the high efficiency and low pollution diesel engine,which is greatly affected by the intake port.As one of the key parts of diesel engine,intake port has a great effect on the amount of air entering the cylinder and the ability to form vortex,which affects the formation of the mixture gas in the cylinder and the combustion process,thereby affect the power performance,economy and emissions performance of the diesel engine indirectly.For this purpose,three-dimensional transient simulation of inlet flow characteristics of intake port is carried out based on Wartsila 4L20 marine four-stroke turbocharged diesel engineFirstly,the intake port model of diesel engine is obtained by liquid silicon.The point cloud data obtained by 3D scanning are imported into CATIA software to reconstruct the reverse surface,and the 3D solid model of the intake port is achieved.On this basis,the intake valve,valve seat and cylinder are added to obtain a complete geometric model of the calculation area.In order to obtain the desired transient simulation of inlet boundary and initial conditions,build the one-dimensional simulation model using AVL BOOST software,based on the initial mesh of 3D geometric model.Then,the three-dimensional transient numerical simulation of the intake process of the diesel engine intake port is carried out,and the variation law of the air flow with the crank angle and the evolution process of the flow field are studied.Take the swirl ratio,tumble ratio,mean turbulence kinetic energy,mean dissipation rate,mass flow and mass as indexes to show the variation trend of the flow field integrally.After comparing the relevant literature,the simulation results of this paper accord with the objective law of engine transient simulation,and have certain universality.Finally,the influence of the above structural parameters on the flow characteristics of the intake port of the diesel engine is studied with the macro parameters as the evaluation index.The simulation results show that:The swirl ratio and tumble ratio decrease with the increase of the height of the spiral chamber.The mean turbulence kinetic energy and mean dissipation rate increase with the increase of the height of the spiral chamber.The influence of the height change of the spiral chamber on the mass flow and mass is negligible in the range of error allowed.With the increase of the cone angle of the valve,the swirl ratio changes little,the tumble ratio(TRx)decreases first and then increases,and the tumble ratio(TRy)decreases.The mean turbulence kinetic energy and mean dissipation rate increase first and then decrease with the increase of the cone angle of the valve.The mass flow and mass decrease with the increase of the cone angle of the valve.Combined with the change curve of the evaluation parameters,and referring to the importance of the evaluation parameters in the analysis,the results are as follows:when the height of the spiral chamber is 10mm and the cone angle of the valve is 20°,the initial structure parameters of the intake port are more reasonable.