Thermodynamic Characteristic Study Of A High Temperature Flow Rate Valve

A high temperature flow rate control valve is developed to control the fuel supply for ramjet engines at high temperature in this paper. As an active cooling method is required by the ramjet engines, the cold liquid fuel is circulated across the engine surface before going into the combustion chamber to decrease the surface temperature of the engine. Therefore the temperature of the fuel supply was raised up to be as high as 400~500°C. The real time flow rate regulation when the fuel was supplied to the engine is important for the combustion and working performance of the engine. The flow rate supplied to the engine needs to be regulated by a valve with high responding speed. When a common hydraulic valve works at the temperature as high as 400~500°C, it maybe encounters some problem. Firstly, the material will be melted because of the high temperature. Secondly, there will be a thermal deformation because of the small thermal expansion and yield stress coefficient of the material, so that the friction pair between the valve body and the spool can not work well. The friction pair is critical for the performance of the fuel supply control valve. If the thermal expansion coefficient is large, the clearance between the friction pair will become larger or smaller than usual. Therefore the valve will fail to work because of the larger leakage or friction force between the valve body and the spool.In this paper, the thermodynamic mathematic model and boundary conditions are introduced. The temperature field distribution and the thermal stress inside the materials of the valve are analyzed using the finite element analysis methods. The thermodynamic characteristics of the friction pair is studied under different working conditions, when the valve is made of different materials. The temperature field and thermal stress field between the friction pair are given when the high temperature fuel passes across the opening valve. The thermal expansion of the friction pair is evaluated at the same time. Thermodynamic experiments are carried out at different supply pressure of the valve. The comparison between simulation and experimental results shows that the thermodynamic mathematical model and analysis are reasonable.