Parametric analysis on throttling elements of conical throttling valve for hydrogen decompression in hydrogen fuel cell vehicles

Abstract

As the most common component of the pressure management system in hydrogen fuel cell vehicle (HFCV), the structure of conical throttling valve affects the hydrogen decompression performance significantly, which plays an important role in the safe and stable application of hydrogen. In this paper, parametric analysis on throttling elements of conical throttling valve for hydrogen decompression is presented. The hydrogen decompression and flow model is built based on the real gas model. The velocity, pressure, temperature and turbulent kinetic energy are monitored for reflecting the hydrogen flow characteristics. The influence of the cone angle and the pressure difference between inlet and outlet on the hydrogen decompression performance is studied. The results are shown that cone angle and pressure difference significantly affect flow patterns and flow characteristics in the flow region near the cone surface of valve core. There is stronger turbulent flow along the cone surface under the smaller cone angle and higher pressure difference. When the cone angle is below 45°, the flow pattern flowing out along the cone surface transforms from free jet to parallel flow along the cylindrical surface. The multiple high-velocity regions are generated behind the narrow throttling gap under large pressure difference. With the decrease of pressure difference, the position of maximum velocity gradually moves closer to the flow region of narrow throttling gap. The optimizing structure with a convex cylinder has a positive effect on improving the flow patterns and hydrogen decompression performance. The stability of decompression can be achieved within a short distance by the optimization structure of the convex cylinder. This study can provide a reference for the design of conical throttling valves for hydrogen decompression in hydrogen fuel cell vehicles.