JP3179672B2 - Pump device with self-control function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump device having a self-control function for always controlling a discharge pressure of a pump to be substantially constant with respect to fluctuations in a pump load.

[0002]

2. Description of the Related Art FIG. 8 is a diagram showing the head (H) and flow rate (Q) characteristics of a conventional general centrifugal pump. As shown in the figure, when the load (pipe resistance) on the discharge side changes, the operating point of the pump changes from point A to point B, for example, and the discharge pressure (H) and flow rate (Q) of the pump change. I do. A change in the discharge pressure may cause an increase or decrease in the water pressure on the demand side, for example, which may be inconvenient.

In order to keep the discharge pressure of the pump constant with respect to load fluctuation in a conventional centrifugal pump,
Various methods have been employed. As an example, a method of providing a rotation speed control device for controlling the rotation speed of the pump and controlling the pump rotation speed in accordance with the fluctuation of the pump load, or a method of providing a pressure control valve at the pump discharge port to change the pump load For example, there is a method of controlling the pressure control valve.

[0004]

However, the above-mentioned conventional methods all require the addition of special equipment such as a rotational speed control device, a pressure control valve, and a drive device thereof having a complicated structure, and the entire pump device is required. There is a problem that it is complicated and expensive and requires complicated installation and adjustment work.

[0005] The present invention has been made in view of the above-mentioned problems, and controls the discharge pressure to be constant with respect to load fluctuation.
An object of the present invention is to provide a pump device including a self-control mechanism in the pump itself.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a vortex chamber disposed at a suction port of a centrifugal pump, and a backflow pipe communicating from a discharge port of the centrifugal pump to an outer peripheral portion of the vortex chamber. A flow path, and the outlet of the backflow pipe and the inlet of the transport fluid are caused to collide with the transport fluid flowing backward from the discharge port of the pump into the outer periphery of the vortex chamber, thereby narrowing the transport fluid. In addition, a function of self-controlling the discharge pressure of the pump substantially constantly with respect to fluctuations in the pump load so as to obtain steep diode characteristics is provided.

The backflow pipe is arranged such that a backflow fluid flows in a tangential direction of an outer peripheral portion of the vortex chamber, and the transport fluid flows in a substantially radial direction of the vortex chamber and collides with the backflow fluid. The angle formed between the flow direction of the backflow fluid and the flow direction of the transport fluid is larger than 90 °.

[0008]

According to the present invention, as described above, the vortex chamber is provided at the suction port of the centrifugal pump, and the backflow pipe communicating from the discharge port to the outer periphery of the vortex chamber. It is configured to collide with the transport fluid flowing into the outer peripheral portion of the chamber. Therefore, in the vortex chamber, a steep diode characteristic is obtained in the relationship between the pressure and the flow rate. That is, when the pressure of the backflow fluid becomes higher than a certain value, the inflow amount of the transport fluid is reduced, and when the pressure of the backflow fluid falls below a certain value, the inflow amount of the transport fluid increases. By feeding back such characteristics of the vortex chamber, the discharge pressure of the pump can be self-controlled to be substantially constant with respect to fluctuations in the pump load.

In particular, the collision between the flow of the backflow fluid flowing tangentially at the outer peripheral portion of the vortex chamber and the flow of the transport fluid flowing substantially radially is larger than 90 °, and the collision is made in a slightly opposite direction. Accordingly, the diode characteristics can be made steeper, and as a result, the pressure fluctuation on the discharge side of the pump can be reduced.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 1 is a view showing the structure of a centrifugal pump device according to the present invention. Reference numeral 1 denotes a pump casing, reference numeral 2 denotes an impeller housed in the pump casing 1, and reference numeral 3 denotes a pump main shaft. The impeller 2 is fixed to one end of a pump main shaft 3. The pump main shaft 3 is rotatably supported by bearings 4 and 5. In the centrifugal pump device having the above structure, the pump main shaft 3 is indirectly or directly connected to a main shaft of a drive motor (not shown) via a speed reduction mechanism or the like. When the drive motor is rotated, the impeller 2 rotates via the pump main shaft 3.

By the rotation of the impeller 2, a transport fluid such as water is sucked from the transport fluid inlet 10, flows into the vortex chamber 7, passes through the pump suction port 6, and is pressurized by the impeller 2. Is discharged from the pump discharge port 11. Note that reference numeral 1
3 is a sealing mechanism. The backflow pipe 12 is connected between the pump discharge port 11 and an outer peripheral portion of the vortex chamber 7 which is an inflow port of the transport fluid.

FIG. 2 shows a cross section of the vortex chamber 7 along the line AA in FIG. As shown in the figure, the outlet 12a of the backflow pipe 12 is provided so that the backflow fluid from the outlet 12a is ejected in the tangential direction of the outer peripheral portion of the vortex chamber 7. The inlet 10 of the transport fluid flowing into the vortex chamber 7 is
Are provided substantially in the radial direction. Inlet 10
From the outlet 12a of the backflow line 12
It is arranged so as to collide with the backflow fluid ejected from the nozzle. Then, the backflow fluid applies a swirl force to the transport fluid, and generates a swirl flow indicated by an arrow in the figure. Reference numeral 9 in the drawing denotes a stay, which supports the vortex chamber 7 and imparts a radial component to the swirling flow and guides the swirling flow to the suction port 6.

FIG. 3 shows a configuration of a control circuit of the pump device. _Let the pressure of the transport fluid at the inflow port 10 of the vortex chamber 7 be P _S , and the flow rate be Q _S. The pressure of the backflow fluid in the vortex chamber outer periphery P _C, the flow rate Q _C. The pressure of the transport fluid at the pump suction port 6 is P ₀ , and the flow rate is Q ₀ . The pressure of the transport fluid at the pump discharge port 11 pressurized by the pump impeller 2 is set to P ₁ . Flow rate Q ₁ at this pressure P ₁ is supplied to the load side via line resistor R _1. Further, the flow rate Q _f as a backflow conduit 12, the pressure P _C to the outer peripheral side of the vortex chamber 7 by the pipeline resistance R _11, is fed back as reflux fluid flow Q _C.

FIG. 4 shows a model of the shape of the vortex chamber 7. Here, the diameter of the backflow pipe 12 is assumed to be b _c , and the diameter of the inflow port of the transport fluid is assumed to be b _s . The radius of the outer circumference of the vortex chamber is r ₁ and the diameter of the suction port is r ₀ . The arrows in the figure indicate the turning direction of the fluid. Although the flow direction of the inflow port 10 of the transport fluid is substantially the radial direction of the vortex chamber 7, the flow direction is shifted from the radial direction by the supply port angle β. The supply port angle β of the vortex chamber 7 is set to a negative value, that is, the angle formed between the inflow direction of the backflow fluid and the inflow direction of the transport fluid is larger than 90 °, and the two are slightly opposed to each other. By making them collide,
The diode characteristics of the vortex chamber can be made steeper.

Based on the control circuit shown in FIG. 3 and the model shown in FIG. 4, the basic expressions of the control characteristics are as shown in equations (1) to (7).

[0017]

(Equation 1)

The pumping characteristics of the pump can be calculated using these equations. In addition, the characteristics of the vortex chamber modeled in FIG. 4 are expressed by Bichara's equation (Analysis and Modeling of
theVortex Amplifier, Trans. ASME Journal of Basic
Engineering, Vol.91 (1969), can be calculated by modifying the equation (8) the tangential speed V [theta] _i of Pp.755-763).

FIG. 5 shows an example of a calculation result of the pressure / flow rate characteristics of the vortex chamber. In the relationship between the pressure P and the flow rate Q, the pump discharge pressure P ₁ is high, ie, the pressure P _{C of the} backflow fluid.
The state having a large difference between the suction side pressure P ₀ throttled flow rate Q ₀ is substantially constant value, it is seen that the diode characteristics that the flow rate Q ₀ is sharply increased to obtain a low state pressure P _1.

In the figure, the dotted line indicates the case where the supply fluid angle β of the transport fluid in the vortex chamber is −25 °, the solid line indicates the case where it is 0 °, and the dashed line indicates the case where it is + 25 °. As is apparent from the calculation result, by setting the supply port angle β to be a negative value, that is, the angle formed between the flow direction of the backflow fluid and the flow direction of the transport fluid is larger than 90 °. By setting, steep diode characteristics can be obtained.

FIG. 6 shows calculated values of the pump head (H) and flow rate (Q) characteristics when the feedback control of the pump is performed using the vortex chamber having the characteristics shown in FIG. FIG.
It is an experimental value obtained by confirming the calculation result shown in FIG. 6 by an experiment.

In the figure, the dashed line indicates the case where the feedback control by the vortex chamber is not performed.
The solid line indicates the case where the supply port angle β is 0 °. The bottom line in the figure indicates the supply port angle β is +2.
5 °.

As is apparent from these figures, when the pressure on the discharge side of the pump is fed back to the suction side by using a vortex chamber having a sharp diode characteristic, the pump pressure is higher than that without feedback control. Discharge pressure P ₁
It can be seen that it fairly flat controlled regardless of variations of the flow rate Q ₁ a. This effect is particularly remarkable when the supply port angle β is negative and the diode characteristics are sharp.

In the above embodiment, an example is described in which the vortex chamber is provided with one inlet for the transport fluid and one outlet for the backflow pipe. However, two or more outlets may be provided. . Further, a control valve or the like may be provided in the middle of the backflow pipe to adjust the pressure of the control fluid flowing through the backflow pipe. As a result, it is possible to control the pump discharge pressure with respect to the fluctuation of the pump load so as to be more effectively constant, to reduce the loss in the vortex element, and the like.

[0025]

As described above, according to the present invention, the vortex chamber is provided at the suction port of the centrifugal pump, and the reverse flow path communicating from the discharge port of the centrifugal pump to the vortex chamber is provided. The pump discharge pressure can be controlled to be substantially constant with respect to load fluctuation on the pump discharge side by relatively simple means of arranging the fluid ejected from the outlet so as to collide with the transport fluid flowing into the vortex chamber. . In other words, the self-control function of the pump itself provides an excellent effect that the discharge pressure can be kept substantially constant at low cost without using a frequency conversion device or the like.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing the structure of a centrifugal pump device according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

FIG. 3 is an explanatory diagram showing a control circuit of the centrifugal pump device according to one embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a model of a vortex chamber of the centrifugal pump device according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing calculation results of pressure / flow rate characteristics of a vortex chamber.

FIG. 6 is an explanatory diagram showing calculation results of pressure / flow rate characteristics of a centrifugal pump.

FIG. 7 is an explanatory diagram showing experimental results of pressure / flow rate characteristics of a centrifugal pump.

FIG. 8 is an explanatory diagram showing pressure / flow rate characteristics of a conventional centrifugal pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump casing 2 Impeller 3 Pump main shaft 4, 5 Bearing 6 Pump suction port 7 Vortex chamber 10 Vortex suction port 11 Pump discharge port 12 Backflow pipe 13 Sealing mechanism

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-72706 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04D 15/00 F04D 1/00 F04D 29 / 00

Claims (2)

(57) [Claims] A vortex chamber disposed at a suction port of a centrifugal pump;
A reverse flow passage communicating from the discharge port of the centrifugal pump to the outer peripheral portion of the vortex chamber is provided, and the transport fluid flowing backward from the discharge port of the pump is connected to the outlet of the reverse flow channel and the inlet of the transport fluid. By squeezing the transport fluid by colliding with the transport fluid flowing into the outer periphery of the vortex chamber, to obtain a steep diode characteristic,
A pump device having a self-control function, characterized in that the pump device has a function of always self-controlling the discharge pressure of a pump substantially constantly in response to a change in pump load. 2. The backflow conduit is arranged such that a backflow fluid flows in a tangential direction of an outer peripheral portion of the vortex chamber, and the transport fluid flows in a substantially radial direction of the vortex chamber and collides with the backflow fluid. 2. The pump device having a self-control function according to claim 1, wherein an angle formed between the flow direction of the backflow fluid and the flow direction of the transport fluid is larger than 90 [deg.].