JPH0417884Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a valve body of a butterfly valve used as a control valve for controlling the flow rate of fluid such as water or gas flowing through a pipe.

A butterfly valve as a control valve has a large flow rate that can flow with the same differential pressure even if the diameter is the same as that of other types of control valves, that is, the valve capacity is large, but it has the disadvantage that it is susceptible to flow contraction and cavitation. Also, when the valve is opened and fluid begins to flow, the flow velocity toward the nozzle part of the valve body increases, and the static pressure generated on the downstream surface of the valve body causes a force that tries to close the valve body, and U towards the orifice part of
The disadvantage is that the valve tends to close due to the combined dynamic torque of the force that tends to close the valve due to the change in momentum caused by the turned flow.

Cavitation occurs because, as shown in FIG. 6, a contraction section A is formed on the downstream side of the valve body. A flow contraction zone is a phenomenon observed in valves where the pressure _P2 on the downstream side of the valve body is lower than the pressure _P1 on the upstream side, and the fluid temporarily becomes high flow velocity,
This is due to static pressure changing to dynamic pressure and becoming contracted flow. Then, when the pressure pvc in the contraction section A drops significantly and becomes lower than the vapor pressure pv of the fluid, bubbles are generated and cavitation occurs. In the case of a butterfly valve, since the flow in the nozzle section is particularly high-speed, cavitation is likely to occur on the downstream side of the nozzle section.

In the past, several proposals have been made to reduce the dynamic torque in butterfly valves used as control valves, but there have been few valves that can also improve cavitation resistance. An example of a valve proposed to reduce dynamic torque and improve cavitation resistance is shown in FIGS. 4 and 5. This valve has a valve body 1 bent toward the upstream side in an inverted dogleg shape to reduce dynamic torque, and a plurality of slits 3 are formed along the periphery on the upstream surface on the nozzle side and the downstream surface on the orifice side. Cavitation is reduced by protruding the edge 2 and suppressing the flow. However, since there is only one row of edges 2 on the periphery to prevent the fluid from increasing in speed, a sufficient effect cannot be expected, and cavitation cannot be prevented. In addition, since the valve body is bent in the opposite direction for backflow, there is a drawback that it does not have the effect of reducing dynamic torque.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional butterfly valve as a control valve, and can reduce dynamic torque and improve cavitation resistance at the same time. Furthermore, the technical challenge is to achieve these effects regardless of the direction of flow.

The technical means taken to solve this technical problem is a butterfly valve in which a disc-shaped valve body 11 is rotatably supported by a valve shaft 12 in a cylindrical main body 10. A plurality of rod-shaped protrusions 17 that are independent of each other and extend perpendicularly to the upstream surface of the valve body are arranged at appropriate intervals over almost the entire area of the upstream surface 14 from at least the valve shaft 12 to the nozzle part 13,
It is characterized in that the protrusion 17 is a resistor that obstructs the flow of fluid from the valve stem 12 toward the nozzle portion 13.

Such technical means work as follows. As shown in FIG. 1, the fluid from upstream is divided into a flow I toward the nozzle portion and a flow toward the orifice portion at a position approximately 1/2 to 1/3 of the radius of the upstream surface of the orifice side of the valve body. The flow I flowing along the valve body toward the nozzle portion collides with the protrusion, and the flow direction is reversed to the upstream direction, causing a change in momentum. Such a change in momentum becomes a force pushing the valve body in the opening direction, cancels out the dynamic torque, and reduces the dynamic torque. The force applied to the protrusion in the valve opening direction is the cumulative effect of these forces, and a sufficiently large force can be obtained.
If the force in the valve opening direction is too large than the dynamic torque, it can be easily adjusted by cutting off the protrusion as appropriate. Further, the protrusion is located at a position where it obstructs the flow I toward the nozzle portion, and the flow colliding with the protrusion loses kinetic energy and its flow velocity decreases. For this reason,
Contraction is less likely to occur on the downstream side of the nozzle, and cavitation can also be suppressed. The flow that collides with the protrusion splits to the left and right as shown in Figure 2, but the flow that collides with the protrusion and splits and the flow that splits after colliding with the adjacent protrusion collide, so the kinetic energy is lost here. There is consumption, and the flow rate is further reduced, which is effective in reducing contracted flow.

Next, we will discuss the effects of this idea. As a result of being able to reduce the dynamic torque as described above, the actuator that drives the valve body can be made smaller, saving drive energy and stably controlling the opening and closing of the valve body. I can do it. Furthermore, by improving cavitation resistance, vibration and noise can be reduced and the life of the valve can be extended. Furthermore, since the valve body itself does not have a directional bend, it has bidirectional properties.
There is no risk of incorrect installation direction, and
The desired effect can also be expected against backflow.

A preferred embodiment of this invention will be described below with reference to FIGS. 1 and 2. In the figure 1
0 is a cylindrical main body, 11 is a valve shaft 12 inside the main body 10
On the upstream surface 14 from the valve shaft 12 to the nozzle portion 13 and the downstream surface 16 from the orifice portion 15 of the valve body 11, which is a disk-shaped valve body rotatably supported by the
A large number of protrusions 17 are erected. The protrusion 17 is the valve body 1
They are arranged at appropriate intervals over almost the entire upstream surface from the valve shaft 12 of No. 1 to the nozzle portion 13 or the downstream surface from the orifice portion 15.
It is designed so that it functions sufficiently as a resistor adjacent to the front and back toward the nozzle portion 13 or orifice portion 15. The protrusions 17 do not necessarily need to be installed in the entire area from the valve stem to the periphery, but they are provided in sufficient number in an area sufficient to cause a change in the direction of movement of the flow and to reduce the flow velocity to a level at which contracted flow does not occur. shall be placed. In this specification, substantially the entire area should be understood to have this meaning. The cross-sectional shape of the protrusions 17 is not limited to the circular shape shown in the figure, but may have a rectangular cross-section such as a triangular or square cross-section, and the lower part of each protrusion 17 is connected by a connecting base portion having a certain height. Also good. Further, in the illustrated embodiment, the valve body 11
Although it is formed in a symmetrical region on both sides, it is of course possible to form it only on one side. Even if it is formed on one side, the valve body 11 only needs to be reversed, so there is virtually no directionality in mounting the valve body of this invention. Further, as shown in FIG. 3, fewer protrusions 17 may be arranged on the semicircular surface on the orifice side than on the nozzle side in order to reduce the dynamic torque and the flow velocity on the orifice side. Of course.

[Brief explanation of the drawing]

Fig. 1 is a side view of the butterfly valve according to this invention, showing the main body in cross section, Fig. 2 is a front view, Fig. 3 is a front view showing another modification, and Fig. 4 is a side view of the conventional butterfly valve. 5 is a front view of the same, and FIG. 6 is a graph showing the occurrence of diameter reduction in a conventional butterfly valve. 10... Main body, 11... Valve body, 12... Valve shaft,
13... Nozzle part, 14... Upstream surface, 15... Orifice part, 16... Downstream surface, 17... Protrusion.

Claims (1)

[Scope of utility model registration request] In a butterfly valve in which a disc-shaped valve body 11 is rotatably supported by a valve shaft 12 in a cylindrical main body 10, almost the entire upstream surface 14 of the valve body 11 from at least the valve shaft 12 to the nozzle portion 13 A plurality of rod-shaped projections 17 are arranged at appropriate intervals and are independent of each other and extend perpendicularly to the upstream surface of the valve body.
A valve body for a butterfly valve, characterized in that 7 is a resistor that obstructs the flow of fluid from the valve shaft 12 toward the nozzle portion 13.