JPH0849692A - Double suction centrifugal pump - Google Patents

Abstract

PURPOSE:To prevent lowering of pump efficiency and to reduce a fluid force by operating a moving tongue, mounted in such a manner that a tongue part is partially divided in a spiral casing, by a pressure regulating device. CONSTITUTION:An impeller 3 rotationally driven by a rotary shaft 2 to boost fluid is contained in a casing 1. A tongue 4 having two end supported and a tip being movable is incorporated in a casing 1a on the delivery side, and a water injection valve 5 to control the need of water injection is arranged on the side plate side of a tongue part. In a pump, when a fluid force is low, by detecting a total head during operation, the water injection valve 5 is closed and a pressure on the upper surface side of the tongue is increased and a gap between the tongue 4 and a vane outlet is decreased to prevent lowering of pump efficiency. During the starting and the stop of a pump and during operation when a quantity of water is low, through control of opening of the water injection valve 5 when a differential pressure exceeds a set value, high pressure water on the vane outlet side is injected. By decreasing a pressure on the upper surface side of the tongue and moving the tongue to the outer diameter side, a gap between the tongue and the vane outlet is increased and a fluid force, such as pressure pulsation and noise, is suppressed to a low value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double suction volute pump, and more particularly to a double suction volute pump which has reduced pressure pulsation, noise and fluid force of radial thrust in a small amount of water region.

[0002]

2. Description of the Related Art A conventional spiral pump has, for example, a structure as shown in "Mechanical Engineering Handbook, B5, Chapter 162, Turbo pump, page 162 of Chapter 76" edited by the Japan Society of Mechanical Engineers. Was.

The conventional fluid force reduction technique is generally 180 as shown in the document “FIG. 157 on page 75”.
There is a double volute with two spiral chambers at every ° to reduce radial thrust. Further, means for reducing the fluid force such as pressure pulsation and noise are, as described in Japanese Utility Model Laid-Open No. 54-78901, a means for shifting the pitch of blades provided on both sides of a double suction impeller, or a spiral winding. A large gap is used between the tongue portion of the casing (the beginning of the spiral winding) and the outlet of the impeller.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the −78901 publication, the main plate in the center of the impeller must be extended to the same diameter as the vane outlet in order to shift the pitch. Compared to the standard type as shown in FIG. The inside gets bigger.

Further, since both the left and right flow paths are partitioned by the main plate, the flow path becomes non-uniform due to manufacturing errors and the like, and the pressure in the left and right flow paths becomes unbalanced, which makes the axial flow unstable.

Further, in the impeller whose main plate in FIG. 162 is smaller than the blade outlet, the left and right blade pitches cannot be shifted as in Japanese Utility Model Laid-Open No. 54-78901. Although the gap with the vehicle outlet is made large, in this case, in order to make the gap large, it is necessary to cut the outer diameter of the impeller or make the casing size larger than usual design. Therefore, the efficiency of the pump is lower than that of a pump that is normally designed (the gap between the tongue portion and the impeller outlet is small). This leads to an increase in equipment costs such as a drive output and an increase in running costs in a large capacity pump.

There is a problem that

An object of the present invention is to reduce the fluid force by paying attention to the pressure characteristics in a small amount of water in the spiral casing and the impeller.

[0009]

In order to achieve the above-mentioned object, the present invention separates the tip of the tongue part in a normally designed spiral casing and impeller (the gap between the tongue part and the impeller outlet is small). A pipe that recycles the high pressure water on the side plate side at the tongue and the impeller outlet and the tongue inlet part in the small water amount area where the one end of the downstream side is supported by a piece, such as a piece, and the tip is movable, to the suction side casing ( (Or the water extraction passage in the casing), and the increase in the fluid force due to the flow rate or the differential pressure (usually, the increase in the fluid force increases the fluctuation of the pressure pulsation), and the above-mentioned high-pressure water is extracted as necessary. , A bleed valve that movably controls the pressure distribution in the tongue part (giving a pressure difference to the upper and lower surfaces of the tongue) is incorporated.

[0010]

[Function] As shown in Fig. 3 (a), the flow in the impeller of the centrifugal pump having a centrifugal impeller has almost no deviation near the design flow rate (near the maximum efficiency point), and the flow is Flows evenly along. When the flow rate becomes a small amount of water, the flow becomes biased toward the side plate side because the ratio of centrifugal force acting on the fluid becomes large as shown in Fig. 3 (b), and the pressure distribution at the impeller outlet is at the center part on the side plate side. Get higher.

Next, looking at the pressure at the tip of the tongue,
As shown in FIG. 2, the upper surface side of the tongue is higher than the lower surface side, and a force that directs the tongue toward the inner diameter side acts.

In consideration of the above characteristics, in the present invention, a part of the high pressure on the side plate side in the small water volume region is extracted and recirculated to the suction side casing, so that the pressure on the lower surface side becomes higher than the upper surface side of the tongue. As a result, the tongue whose one end on the downstream side is supported moves toward the outer diameter side due to the pressure difference between the upper and lower surfaces of the tongue. Thereby, the gap between the tongue portion and the blade outlet can be increased, so that the fluid force can be reduced (FIG. 4 (b)). In addition, the extraction of high-pressure water from the tongue is detected by the discharge flow rate or total head (differential pressure), and the extraction valve is opened / closed (automatic control). Since the tongue is closed, the pressure on the upper surface side of the tongue becomes high and the tongue moves to the inner diameter side, so that there is no decrease in efficiency (Fig. 4 (a)).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 (a) and 1 (b).

FIG. 1 (a) shows an embodiment in which a double suction suction pump is provided with a water extraction valve for controlling the pressure of the tongue portion. FIG.
In FIG. 1A, an impeller 3 that is rotationally driven by a rotating shaft 2 to pressurize a fluid is housed in a casing 1. On the tongue side plate side of the discharge side casing 1a, a water extraction pipe 8 and a water extraction valve 5 for detecting the total head (differential pressure between the discharge pressure and the suction pressure) to control the necessity of water extraction and a pipe for returning the water extraction to the suction side casing. It is composed of

FIG. 1 (b) is a longitudinal sectional view of FIG. 1 (a), in which the tip of the tongue portion is partially divided, and a tongue 4 is incorporated into the discharge side casing at the downstream side by a pin so that the tip is movable. There is.

In the double-suction centrifugal pump constructed by the above components, when the pump is operated near the design flow rate where the fluid force is small, the total head is detected, and the water extraction valve 5 is closed.
As indicated by the solid line, the pressure on the upper surface of the tongue can be increased to reduce the gap between the tongue and the blade outlet to prevent the efficiency of the pump from decreasing. Next, at the time of starting / stopping the pump and at the time of partial operation with a small amount of water, the water withdrawal valve is pulled out when the water pressure exceeds a given differential pressure (for example, the flow rate at which the fluid force such as the pressure corresponding to the 50% design flow rate begins to increase). 5 is an automatic opening control, high-pressure water on the side plate side of the blade outlet as shown by the broken line in FIG. 1 (b) is extracted, the pressure on the upper side of the tongue is lowered from the lower side, and the tongue and blade are moved to the outer diameter side. By increasing the gap between the outlets, fluid forces such as pressure pulsation, noise, and radial thrust can be kept low.

Further, the existing plant can be improved by a slight modification of the pump itself.

[0018]

According to the present invention, in the conventional type, when the fluid force such as pressure pulsation, noise, radial thrust, etc. in the small water region becomes large due to the enlargement of the pump, the structure of the impeller and the spiral casing are changed. Since the fluid force can be reduced without increasing the size, etc., not only can the element parts such as bearings be downsized, but also the effects on peripheral equipment such as pipes and buildings and the surrounding environment can be reduced, improving plant reliability. Can be expected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of a double volute casing.

FIG. 3 is a cross-sectional view of an impeller outlet to a tongue portion.

FIG. 4 is a characteristic diagram of efficiency and pressure pulsation due to a gap between a tongue and a blade outlet.

[Explanation of symbols]

1 ... Swirl casing, 1a ... Discharge side casing, 1b
... Suction side casing, 2 ... Shaft, 3 ... Impeller, 4 ... Movable tongue, 5 ... Water extraction valve, 6 ... Controller, 7 ... Recirculation piping, 8 ...
Water extraction piping, 8a ... Water extraction port.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimasa Chiba 2-28-4 Jinritsu Higashi, Tsuchiura City, Ibaraki Prefecture Hitachi Techno Engineering Co., Ltd. Tsuchiura Works (72) Inventor Genichiro Nakamura 603, Kintate Town, Tsuchiura City, Ibaraki Prefecture Nitate Seisakusho Tsuchiura Factory

Claims (1)

[Claims] 1. A swirl pump comprising a double suction centrifugal impeller and a swirl casing, wherein a tongue is provided in the swirl casing, the tongue part being partially movable, and a pressure adjusting device for moving the tongue. A double-suction spiral wound pump characterized by being provided with.