JPH04269393A - Volute type mixed flow pump - Google Patents

Abstract

PURPOSE:To prevent the lowering of pump performance caused by air suction from a higher water level than the intake air unrequired water level and also prevent the clogging of an intake pipe and an intake hole due to foreign material. CONSTITUTION:A branch pipe 21 is horizontally connected to the intermediate part of a suction pipe 5 and raised vertically. An air suction pipe 25 with its tip opened into a higher position than the water intake highest level, and an air suction hole 7 disposed in the air suction required water level position, right in front of the inlet of an impeller 2 are connected to a branch pipe 23 extended from the branch pipe 21 in the same vertical direction through a master valve 22.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed-flow pump, such as a rainwater drainage pump or a sewage drainage pump, which is required to operate at full water level and at full speed.

0002

BACKGROUND OF THE INVENTION A volute mixed flow pump is normally used for rainwater drainage pumps, sewage drainage pumps, etc., and the vortex mixed flow pump is required to operate at full water level and at full speed. FIG. 2 is a sectional view showing a centrifugal mixed flow pump that has been commonly used in the past. This swirl mixed flow pump has an impeller 2 housed in a casing 1, the lower part of which serves as an impeller suction section 3. The impeller suction section 3 is connected to a suction pipe 5 whose tip protrudes into the water intake tank 4 via a connecting pipe 6 or the like.

[0003] Further, the impeller suction portion 3 is provided with several intake holes 7 for intake in the circumferential direction immediately before the inlet of the impeller 2, and each intake hole 7 is formed by a ring arranged in a ring shape. It is connected to pipe 8. The ring pipe 8 is connected to an intake pipe 9, and the intake pipe 9 extends in the vertical direction, and its tip is opened at a position higher than the highest intake water level HWL of the swirl mixed flow pump. Therefore, such a volute mixed flow pump is called an atmospherically open type vortex mixed flow pump. The impeller 2 is connected to a rotating shaft 10 that is rotationally driven by a drive source (not shown), and pressurizes fluid such as sewage flowing into the suction pipe 5 into the volute chamber 11 by rotating the impeller 2. It is sent out and discharged.

0004

[Problems to be Solved by the Invention] As mentioned above, conventional atmospherically open type spiral mixed flow pumps have problems with intake air due to the relationship between the water level in the water intake tank 4 and the loss in the suction pipe 5 up to the impeller suction section 3. Because it sucks in air from a higher water level than it doesn't need,
There was a problem in that this resulted in an unnecessary reduction in pump performance.

[0005] To solve this problem, instead of the intake pipe 9 extending vertically and having its tip opened at a position higher than the highest water intake water level HWL, a diagram in which the same parts as in FIG. 2 are given the same reference numerals. 3, by extending the intake pipe 9a horizontally from the ring pipe 8, the water level LW of the water intake tank 4 that requires intake air is adjusted.
This problem can be solved by using a so-called tank-directly connected vortex mixed flow pump connected to the L position. In other words, Fig. 4 shows the changes in efficiency and flow rate of the atmospherically open type vortex mixed flow pump and the tank-directly connected type vortex mixed flow pump. It can be seen that the tank-directly connected type vortex mixed flow pump directly connected to the water level LWL of the water intake tank 4 exhibits better characteristics than the atmospherically open type vortex mixed flow pump shown by the broken line. In addition, in FIG. 4, the horizontal axis is the ratio of the height Hs from the center of the suction pipe 5 to the water level to the diameter D of the suction pipe 5.

By the way, various foreign substances flow into the water intake tank 4. Therefore, in a tank-directly connected type swirl mixed flow pump, when the water level is high, water also flows into the intake pipe 9a, and foreign matter gets mixed in, causing the intake pipe 9a to
There was a problem that the air intake hole 7 was blocked or the air intake hole 7 was clogged. The present invention has been made to solve these problems, and it prevents deterioration of pump performance due to air being sucked in from a water level higher than the water level that does not require air intake, and also prevents deterioration of pump performance due to air intake from a water level that is higher than a water level that does not require air intake. The purpose is to prevent clogging.

[0007]

[Means for Solving the Problems] The present invention includes an impeller that pressurizes fluid flowing into a suction pipe and sends it out to a swirl chamber, and an intake hole connected to the suction pipe and provided immediately before the inlet of the impeller. In a swirl mixed flow pump having an impeller suction section, a first branch pipe connected horizontally in the middle of the suction pipe and raised vertically;
One side is branched horizontally so as to communicate with the intake hole of the impeller suction part, and the other side is an intake pipe extending vertically with its tip opening at a position higher than the highest intake water level. It is provided with a connected second branch pipe and a main valve provided between the second branch pipe and the first branch pipe.

[0008]

[Function] According to the above means, the intake hole of the impeller suction part is indirectly communicated with the position corresponding to the water level that requires air intake, so the tank-directly connected vortex mixed flow pump It is possible to operate the system by taking advantage of its advantages, and at the same time, it is possible to eliminate the inflow of foreign matter.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the centrifugal mixed flow pump according to the present invention will be described in detail below with reference to FIG. Note that in FIG. 1, parts that are the same as those in FIGS. 2 and 3 are designated by the same reference numerals, so a description of those parts will be omitted.

In the mixed swirl pump of the present invention, a first branch pipe 21 is connected horizontally to the middle of the suction pipe 5 protruding into the water intake tank 4. The first branch pipe 21 is vertically raised and connected to the main valve 22. The main valve 22 is connected to a second branch pipe 23. The branch point of the second branch pipe 23 is the water level LW that requires air intake.
A small-diameter branch pipe 24 extends horizontally from this branch point to connect to a ring pipe 8 that communicates with the intake hole 7 of the impeller suction section 3. Further, the second branch pipe 23 is connected to an intake pipe 25 extending in the vertical direction. Note that the tip of this intake pipe 25 opens at a position higher than the highest intake water level HWL.

By the way, in the swirl mixed flow pump of the present invention shown in FIG. 1, the pressure P1 at the first branch point, the pressure P2 at the second branch point, and the pressure P3 at the impeller suction section 3 are expressed as 2 and the number 3.

[Math. 1] P1/γ=H-ζ1・V12/2g

[Math. 2] P2/γ=(H-H2)-(ζ1・V12/2g+ζ2
・V22/2g)

[Math. 3] P3/γ=(H-H2)-(ζ1・V12/2g+ζ3
・V32/2g) In Equations 1, 2, and 3, γ is the specific weight of the liquid, H is the height from the center of the suction pipe 5 to the highest intake water level HWL, and H2 is the height from the center of the suction pipe 5 to the intake water level. The height to the required water level LWL, ζ1, is the suction pipe 5
loss coefficient from the inlet to the first branch point, ζ2 is the loss coefficient from the first branch point to the second branch point, ζ3 is the loss coefficient from the first branch point to the impeller suction part 3, V1 is the velocity of the main stream at the first branch point in the suction pipe 5, V2 is the velocity of the second
V3 is the velocity of the fluid in the branch pipe 23, and V3 is the velocity of the main flow in the impeller suction section 3.

Now, when the water level is high, the main flow flowing through the impeller suction section 3 flows at the pressure difference (P1-P3) between the pressure P1 at the first branch point and the pressure P3 at the impeller suction section 3. The speed is V3. Water also flows toward the branch pipe 24 due to the pressure difference (P2-P3) between the pressure P2 at the second branch point and the pressure P3 at the impeller suction section 3. In this case, compared to the mainstream loss coefficient ζ3, the branch pipe 24 with a small diameter
In this case, the loss coefficient including the intake hole 7 is large, so the amount of water flowing through the branch pipe 24 is small.

[0013] Let us now consider the case where foreign matter is flowing. The first branch pipe 21 branches horizontally, and water flows due to the pressure difference (P1-P2) between the pressure P1 at the first branch point and the pressure P2 at the second branch point, and the flow rate is It's as small as V2. Therefore, it is difficult for foreign matter to flow into the first branch pipe 21, and even if it does, the flow velocity V2
Sludge and the like will settle in areas where the water is small and rises vertically. Further, in the case that the valve is clogged with foreign matter, maintenance can be easily performed by closing the main valve 22.

[0014] On the other hand, regarding intake air, the situation is as follows. In other words, intake occurs when the pressure P2 at the second branch point becomes negative pressure, and the conditions are as follows from Equation 2:

[Math. 4] (H-H2)<(ζ1・V12/2g+ζ2・V22/
2g). When air is inhaled, the second term on the right side of Equation 4 becomes zero, so the relationship between the water level at which air is to be inhaled and the flow rate Q is:

[
It can be determined as H2=H-ζ1/2g(Q/A1)2. Note that in Equation 5, A1 is the cross-sectional area of the suction pipe 5.

[0015]

Effects of the Invention As described in detail above, according to the present invention, the suction pipe 5 is communicated with the water at the highest water level HWL.
Since the intake hole 7 of the impeller suction section 3 is communicated with the intake pipe 25 whose tip opens at a higher position than the above, it is possible to operate a swirl mixed flow pump that takes advantage of the advantages of a tank-directly connected swirl mixed flow pump. becomes. Therefore, unlike an atmosphere-opening type swirl mixed flow pump, there is no possibility of deterioration in pump performance due to air being sucked in from a water level higher than a water level that does not require air intake, and foreign matter is less likely to get mixed into the intake hole 7, etc. A highly effective vortex mixed flow pump is provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of a swirl mixed flow pump according to the present invention.

FIG. 2 is a sectional view showing a conventional atmospherically open type centrifugal mixed flow pump.

FIG. 3 is a sectional view showing a conventional tank-directly connected type centrifugal mixed flow pump.

FIG. 4 is a characteristic diagram comparing the characteristics of conventional swirl mixed flow pumps.

[Explanation of symbols]

2 Impeller 3 Impeller suction part 5 Suction pipe 7 Intake hole 11 Swirl chamber 21 First branch pipe 22 Genben 23 Second branch pipe 24 Branch pipe 25 Intake pipe

Claims (1)

[Claims] Claim 1: An impeller that pressurizes fluid flowing into a suction pipe and sends it out to a vortex chamber; and an impeller suction section that is connected to the suction pipe and has an intake hole for intake air immediately before the inlet of the impeller. In the swirl mixed flow pump, a first branch pipe is connected horizontally in the middle of the suction pipe and is raised vertically; A second branch pipe is connected to an intake pipe that branches horizontally so as to communicate with the intake hole of the section, and the other branch pipe extends vertically and has a tip opening at a position higher than the highest intake water level; A swirl mixed flow pump comprising a branch pipe and a main valve provided between the first branch pipe.