Simulation Research Of Intake Port Flow In Highly Intensified Diesel Engine

The highly intensified diesel engine has the characteristics of high speed,high cycle fuel injection volume and high boost air intake.Compared with traditional diesel engines,it requires a greater amount of air intake,while the intake and combustion processes need to be completed in a shorter time,thus making the intake system more demanding.The geometry of the intake port directly affects the intake charge and swirl strength of the engine,thus affecting the oil and gas mixing and combustion efficiency,which in turn affects the engine’s dynamics,economy and emission performance.Therefore,it is necessary to understand the flow characteristics of the gas under high pressure and provide the necessary theoretical basis for the design of the low-flow resistance intake port of the highly intensified diesel engine.First of all,the double tangential diesel engine is tested through the steady-flow intake port test bench,the flow rate of different valve life under different intake pressures is measured,and then the flow coefficient is calculated.However,the traditional test method needs a lot of human and material resources,can not adapt to the development of modern high-performance engines.Therefore,the use of three-dimensional numerical simulation method is a more efficient research method.This paper uses AVL-FIRE software to mesh the geometric model,set the boundary conditions,apply the turbulence model of k-?-f,use the SIMPLE algorithm of pressure correction,and simulate the calculation and analysis of the circulation characteristics of the three different combinations of double tangential intake port,helical and tangential intake port and double helical intake port.The test and simulation values of the double tangential intake port are verified by AVL evaluation method,and the results match well to ensure the accuracy and feasibility of the calculation model.Then,the flow coefficient,velocity field,pressure field and turbulent energy field of the three combined intake port in the air pressure and pressure difference of 300 k Pa and 30 k Pa are analyzed,which provides reference for the improvement of the intake port performance.Finally,consider the compressibleness of the gas and derive a new flow calculation formula.By comparing the flow coefficients calculated by two different formulas,the necessity of compressibleness is further proved.Then,the concept of relative pressure difference is put forward,and the flow state comparison of the air in the air system at the same relative pressure difference is studied under different intake pressure and pressure difference.