JPH08226397A - Device for reducing shaft power of mixed flow pump or axial flow pump - Google Patents

Abstract

PURPOSE: To reduce cut-off shaft power only near a cut-off and to enable the pump to exhibit its own performance as the flow rate increases by opening or closing throttling blades based on detected values of pressure at an impeller outlet inside a casing. CONSTITUTION: Eight throttling blades 4 are provided around a suction pipe 3, are joined with a lever 5 attached to a shaft passing through the suction pipe, and are moved simultaneously by a guide ring 6 surrounding the suction pipe 3. When the pump is actuated while in a cut-off state, water is pressurized by an impeller 1, and when the throttling blades 4 are fully closed a reverse flow region is restrained as the result of throttling and cut-off shaft power is lowered. Then with an increase in pump displacement, pressure within a casing 2 is also lowered. A pressure sensor 8 detects this pressure drop and signals it to a control board 9, and at or below a certain pressure a motor 7 is energized so that the throttling blades 4 are fully opened. Therefore, the flow is smoothed, and pump efficiency and suction performance near a specified point can be prevented from decreasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft power reduction device applied to reduce the shaft power of a mixed flow pump or an axial flow pump.

[0002]

2. Description of the Related Art A conventional mixed flow pump will be described as an example of a device for reducing dead shaft power and partial load shaft power (hereinafter collectively referred to as dead shaft power). FIG. 4 is a vertical sectional view of a conventional mixed flow pump. The main part of the pump is composed of a rotary shaft 11, an impeller 1, a casing 2, and a suction pipe 3. High specific speed pumps such as mixed flow pumps and axial flow pumps require a motor with a higher output because the deadline shaft power is considerably higher than the specified shaft power.
This is because normal start / stop is performed by deadline operation. Since a high output motor is expensive, a pump with a low shutoff shaft power is desired.

A suction ring 4A shown in FIG. 4 is often used as an example of this measure. This is a kind of throttle provided immediately before the impeller inlet, and is intended to suppress the backflow region that occurs at the impeller inlet and reduce the dead shaft power. The upper half of the figure shows the case where the suction ring 4A is not provided, the lower half shows the case where the suction ring 4A is provided, and the broken line arrow shows the flow of water without the suction ring,
The solid arrows show the flow of water with the suction ring.

In the shut-off operation, the backflow region without a throttle grows greatly, and a high shaft power is required to rotate the impeller, but the backflow region can be reduced by providing the throttle, so that the shutoff shaft can be reduced. Power is also held down low.

[0005]

The above-mentioned conventional shut-off shaft power reducing means has an adverse effect when it is operated near the specification point. That is, when the flow rate increases, due to the throttling, the running water does not smoothly flow into the impeller, leading to a decrease in pump efficiency and a decrease in suction performance, and the original pump performance cannot be exhibited.

In order to solve the problems of the prior art, the present invention reduces the backflow region of the impeller inlet only near the deadline to reduce the deadline shaft power, and returns to the normal suction state when the flow rate increases. It is an object of the present invention to provide a shaft power reduction device for the purpose.

[0007]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and in an axial power reduction device for a mixed flow pump or an axial flow pump provided with a casing, an impeller, and a suction pipe, an impeller inlet. A plurality of rotary shafts that penetrate the suction pipe in the radial direction in the immediately preceding portion, diaphragm blades attached to the inner ends of the rotary shafts, drive means for rotating the rotary shafts,
Pressure detecting means provided in the casing for detecting the impeller outlet pressure in the casing; and control means for controlling the rotating shaft driving means on the basis of the detected pressure value to open and close the diaphragm blades. The present invention relates to a shaft power reduction device for a mixed flow pump or an axial flow pump.

[0008]

[Function] The diaphragm blade is "open" when it is parallel to the pump axis, and "closed" when it is perpendicular to the pump axis.
Is. When the diaphragm blade is closed, the flow path of the suction pipe becomes narrower,
Acts as a diaphragm.

When the pump is operated near the deadline, the inside of the casing has a high pressure. At this time, the high pressure causes the control device to operate and the diaphragm blades to be fully closed, so that the suction pipe can be throttled. As a result, the reverse flow at the impeller inlet is controlled and the shaft power is suppressed low.

When the discharge valve is opened and the operating state is close to the specification point, the pressure in the casing becomes low, so that the control device works and the diaphragm blades are fully opened. Therefore, there is no restriction at the inlet of the impeller, and the pump efficiency and suction performance can exhibit the original performance.

[0011]

1 is a perspective view of a mixed flow pump according to an embodiment of the present invention. In the figure, 11 is the rotation axis of the pump, 1
Is an impeller, 2 is a casing, 3 is a suction pipe, 12 is a rotary shaft penetrating the suction pipe immediately before the impeller inlet, 4 is a diaphragm blade attached to the inner end of the rotary shaft, and 5 is the aforesaid rotary shaft. A lever attached to the outer end of the moving shaft, 6 is a guide ring connected to the lever, 7 is a motor connected to the guide ring, 8 is provided in the casing 2 and detects the pressure at the impeller outlet of the casing. The pressure sensor 9 is connected to the pressure sensor 8 and is a control panel for controlling the drive of the motor 7 according to the pressure detected by the sensor. The upper half of the figure shows the position of the diaphragm blades 4 in a state where water is constantly flowing (forward flow) and the flow of water (arrow) at that time, and the lower half of the figure shows the diaphragm blades 4 at the deadline. The position and the flow of water (arrow) at that time are shown.

FIG. 2 is a transverse sectional view at the position of the diaphragm blade 4 in the above embodiment. Eight diaphragm blades 4 are provided around the suction tube 3. The eight diaphragm blades move in unison by a single guide ring 6 that is connected to the lever 5 attached to the shaft of each blade that penetrates the suction tube and that surrounds the suction tube 3. 10 is a stopper that sets the limit of the movement.

When the pump is started in the closed state, the pressure of water is increased by the impeller 1, but since it does not flow, a large reverse flow region is formed at the inlet of the impeller 1. However, the diaphragm blade 4 is in a fully closed state (the lower half portion in FIG. 1) at the time of activation, the throttling effect is exhibited, the reverse flow region is suppressed, and the shutoff shaft power is suppressed low.

When the pump discharge amount increases, the pump head lowers and the pressure in the casing 2 also decreases. This is detected by the pressure sensor 8 and transmitted to the control panel 9, and when the pressure falls below a certain pressure, the motor 7 is energized and the guide ring 6
The diaphragm blade 4 connected to the lever 5 is fully opened (upper half of FIG. 1). Note that the guide ring 6 is provided with a stopper 10 shown in FIG. 2, which serves as a mechanism for sending a fully closed / fully opened signal to the control panel 9.

When the diaphragm blades 4 are fully opened, the flow at the inlet of the impeller 1 becomes smooth, and the original performance is exhibited without lowering the pump efficiency and suction performance near the specification point. When the pump is stopped, the diaphragm blade 4 is fully closed by the reverse movement of the opening mechanism, and the dead shaft power is reduced. With the above operation, it is possible to start and stop the pump with a pump motor that is slightly larger than the point specification motive power of the pump.

FIG. 3 shows the shaft power reduction range. First, the solid line indicates the shaft power and the alternate long and short dash line indicates the lift. Without the present invention, the dead shaft power is at point A, but when the effect of the diaphragm blades occurs, it is at point B. When the flow rate increases and the discharge pressure drops to point C, the diaphragm blades are fully opened and normal pump operation is started. Therefore, the shaft power reduction portion according to the present invention is a hatched portion.

The effect of the present embodiment is that, in a high specific speed mixed flow and axial flow pump, during the shutoff operation or partial load operation, the inlet backflow is suppressed by the throttle blade provided immediately before the impeller inlet, and the shaft near the shutoff is controlled. To reduce power. If the flow rate increases, the diaphragm blades can be fully opened to eliminate the throttle at the inlet, and the original performance of the pump can be exhibited. As a result, the motor capacity can be reduced and the cost can be significantly reduced.

[0018]

In the axial power reduction device for a mixed flow pump or axial flow pump of the present invention, a plurality of rotary shafts penetrating the suction pipe in the radial direction immediately before the impeller inlet, and inside each rotary shaft. A diaphragm blade attached to the end, a driving means for rotating the rotating shaft, a pressure detecting means provided in the casing for detecting the impeller outlet pressure in the casing, and the rotating shaft drive based on the detected pressure value. Since the control means for controlling the means for opening and closing the diaphragm blades is provided, it is possible to reduce the shutoff shaft power only in the vicinity of the shutoff time and to exhibit the original performance of the pump when the flow rate increases.

[Brief description of drawings]

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

FIG. 2 is a transverse cross-sectional view of the mixed flow pump at positions of diaphragm blades.

FIG. 3 is a relationship diagram showing a shaft power reduction effect.

FIG. 4 is a vertical cross-sectional view of a conventional mixed flow pump.

[Explanation of symbols]

 1 Impeller 2 Casing 3 Suction Pipe 4 Aperture Blade 4A Suction Ring 5 Lever 6 Guide Ring 7 Motor 8 Pressure Sensor 9 Control Panel 10 Stopper 11 Pump Rotating Shaft 12 Rotating Shaft of Impeller

Claims (1)

[Claims] 1. A shaft power reducing device for a mixed flow pump or an axial flow pump, comprising: a casing, an impeller, and a suction pipe, wherein a plurality of rotary shafts radially pass through the suction pipe immediately before the impeller inlet. A diaphragm blade attached to the inner end of each of the rotary shafts, a drive means for rotating the rotary shafts, a pressure detection means for detecting the impeller outlet pressure in the casing, and a pressure detection value thereof. An axial power reduction device for a mixed flow pump or an axial flow pump, comprising: a control means for controlling the rotating shaft drive means based on the above to open and close a diaphragm blade.