Fluid dynamics analysis of butterfly valve opening process

As an indispensable part of the fluid control system, the performance of butterfly valves has a vital impact on the operating efficiency of the entire system. During the opening process of the butterfly valve, the power loss of the fluid is a key parameter, which reflects the energy loss when the fluid passes through the butterfly valve. This article will conduct a detailed analysis of the changes in fluid flow rate, kinetic energy and pressure loss in the early and late stages of butterfly valve opening.

1. The initial stage of butterfly valve opening

In the initial stage of opening of the butterfly valve, the gap between the butterfly plate and the valve seat is small, which limits the flow space of the fluid. Due to the narrowness of the gap, the fluid is forced to accelerate as it passes through to maintain a constant flow rate. This increase in flow velocity causes the kinetic energy of the fluid to also increase because kinetic energy is proportional to the square of the velocity.

At this time, although the kinetic energy of the fluid increases, the pressure loss is relatively small. This is because at this stage, the fluid is mainly affected by the local resistance between the butterfly plate and the valve seat. This local resistance mainly comes from the friction between the fluid and the surface of the butterfly plate and valve seat, as well as the vortex and turbulence of the fluid when passing through the gap. Since the gaps are small, these local resistances have not yet had a significant impact on the entire piping system, so the pressure loss is relatively low.

2. Late opening stage of butterfly valve

As the butterfly valve is further opened, the gap between the butterfly plate and the valve seat gradually increases, and the fluid circulation space also increases. This causes the fluid to flow gradually slower as it passes through the butterfly valve, as the larger space allows the fluid to pass at a lower speed while maintaining a constant flow rate. As the flow rate decreases, the kinetic energy of the fluid also decreases accordingly.

At the same time, however, pressure losses began to increase significantly. This is because as the gap increases, the frictional resistance between the fluid and the pipe wall as well as the turbulence and vortex phenomena inside the fluid become more obvious. These resistances not only come from the local area between the butterfly plate and the valve seat, but also gradually extend to the entire pipeline system. Therefore, although the reduced flow rate reduces the kinetic energy loss of the fluid, the increase in the overall resistance of the piping system results in greater pressure losses.

3. Conclusion

Through the analysis of the fluid flow rate, kinetic energy and pressure loss during the opening process of the butterfly valve, it can be seen that there is a significant difference in the power loss of the fluid in the early and late stages of the butterfly valve opening. In the early stage, although the increase in flow rate leads to an increase in kinetic energy, the pressure loss is relatively small; while in the later stage, although the decrease in flow rate reduces the kinetic energy loss, the increase in the overall resistance of the pipeline system results in a greater pressure loss. Therefore, in practical applications, it is necessary to select the appropriate butterfly valve type and opening method according to specific conditions to optimize system performance.