Numerical Simulation Of The Flow Field Inside A Turbulent Chamber In A Turbulent Combustion System

With the improvement of vehicle economy and emission limit,higher and higher requirements have been put forward for the design of engine combustion system.Turbulent constant volume combustion chamber is a test device to simulate engine combustion,which can effectively simulate engine combustion process and carry out comprehensive research and analysis.There are three methods for constructing turbulent flow: orifice method,inlet method and fan method.In this paper,the composition and functional principle of the fan-method turbulent combustion test system are introduced.Four kinds of axial flow fans with different blade shapes were designed and their functions were analyzed by numerical simulation.It is concluded that the fan performance is related to the shape of the fan blade,and the fan should be stiffened to avoid smaller fan blades to avoid tip turbulence.An axial fan rotates the air from the fan inlet through the fan and out of the fan outlet.The velocity generated by the axial flow fan is faster near the rotation axis of the fan,and the velocity of the axial flow field is basically the same.By setting up the monitoring point,it is found that the speed increase is proportional to the time,and the higher the fan speed is,the higher the speed of the monitoring point will be.The optimal axial flow fan was applied to the turbulence chamber with positive tetrahedron distribution,and the grid independence and experimental verification were carried out to verify the reliability of the physical model.Numerical simulation of turbulence chamber was carried out to study the turbulent environment created by axial flow fan at different speeds under high and low pressure conditions.The variation of velocity field and turbulence intensity in a turbulent chamber is analyzed.It is concluded that the velocity in the surrounding area is large in the turbulent projectile,and the maximum velocity is 1.8m/s.The main burning area has a small speed,ranging from 0 to 0.5m/s.In addition,the velocity in the central part of the main combustion area,namely the chamber,is almost constant,while the velocity increases gradually near the fan.The velocity and turbulence intensity of the flow field in the main combustion area of the combustor increase with the same initial pressure.With the same initial pressure,the greater the fan speed,the greater the speed of the main combustion area of the combustion chamber,but the turbulence intensity does not change significantly.In terms of the study on the stability area of turbulent region,the radius of the turbulence stability area in the low-pressure environment is almost greater than 1/3 of the capacity chamber diameter.When the initial pressure is close to 0.4MPa,the diameter rate of the stability area will be less than 1/3.In a high-pressure environment,the radius of the turbulence stability area decreases with the increase of fan strength and initial pressure,but the influence of fan strength on the radius of the turbulence stability area is less obvious than that of initial pressure.When the initial pressure is higher than a certain value,the radius of the turbulence stability area will be less than one third of the capacity indoor diameter,which is not conducive to the experimental study.So when you do high pressure turbulent combustion you have to control the initial pressure of the environment and the fan speed.