Thermal Performance Analysis And Numerical Simulation Of Hollow Sodium-filled Valve

Valve is the core component of engine valve train,which is also an important component to ensure that the engine has good economic performance,power performance,reliability and durability.However,due to the continuous improvement of engine strength,the popularization and application of sodium-valve technology,the heat load of exhaust valves is increasing.The original cooling method through the contact of valve cone and valve seat ring has gradually reached the heat dissipation bottleneck.Therefore,there is an urgent need to develop a new cooling technology of exhaust valves.Under such circumstance,there appears hollow sodium filled valves.The present study choose Santana AFE engine as the object of analysis,three engine operating points(speeds of 800 r/min,3100 r/min and 5200 r/min)were selected to compare the heat load and temperature distribution of solid rod exhaust valve and hollow sodium-filled exhaust valve.Firstly,the reverse mapping of the exhaust valve was carried out to obtain the exact size data of the exhaust valve,meanwhile,three-dimensional model of the exhaust valve was established with the collected data through Solidworks software.Then,using the AVL Timing Excite Drive,the valve mechanism was redesigned to get the velocity and acceleration of the exhaust valve with the data of the valve mechanism of AFE engine.Based on the comparison of the oscillating velocity of exhaust valve,the axial velocity of steam passage of high temperature heat pipe and the relevant literature,the feasibility analysis in carried out on the equivalent treatment of heat transfer mechanism between hollow sodium filled valve and high temperature heat pipe,and the pressure-angle dynamometer diagrams of the engine at the above three operating points are simulated and calculated by GT-Suit software.Next,ANSYS Workbench was used to simulate the temperature field of the exhaust valve assembly.Finally,the temperature distribution cloud and longitudinal section and the temperature curve of the exhaust valve outer surface along the axial length of the exhaust valve were obtained.The results indicate that the cooling capacity of the hollow sodium-filled valve increases with the heat load of the exhaust valve.Compared with that of the solid rod exhaust valve,the hottest temperature of the hollow sodium-filled exhaust valve can be reduced by 151.31? under the high load condition of 5200 r/min.