Numerical analysis of flow field in link rod butterfly valve for high-temperature steam

Abstract

The link rod butterfly valve, which uses a four-bar linkage mechanism to drive the valve plate, is a promising candidate for treating high-temperature steam and industrial exhaust because of its reliable sealing property. In this paper, the 3D flow field in the link rod butterfly valve for high-temperature steam was simulated using computational fluid dynamics. The flow coefficient of the valve, the velocity field, the temperature distribution and the enthalpy change in the steam under different valve openings were studied. The results showed that the flow coefficient of the link rod butterfly valve increased with an accelerated slope as the rotation angle of the valve stem was enlarged over 60°. The velocity and the vorticity of the steam were dramatically increased near the valve. The steam branches were accelerated up to 15 times the inlet flow velocity when they passed through the gaps between the valve plate and the valve body, and the vorticity was as large as 76/s. The temperature of the steam passing through the valve was decreased by 50–108 K for different openings. The temperature difference in the steam on the valve plate was as high as 400 K, which makes a challenge for the material of the valve plate. Larger enthalpy drop of the steam was resulted in when the valve was working at the throttling state than fully opened. Local peaks for the enthalpy drop were observed as the valve stem was rotated by 30° and 60°, and the local valley was at about 50°. The present study may serve as a useful reference for the design of link rod butterfly valves.