JP2024056152A - Flow Control Device and Centrifugal Pump - Google Patents

Abstract

[Problem] To expand the operating flow rate range of a centrifugal pump equipped with an inducer to the small flow rate region. [Solution] A flow rate control device (4) according to the present invention is a flow rate control device that controls the axial flow rate of handled liquid flowing in a suction pipe (35) of a centrifugal pump (1) equipped with an inducer (34). The flow rate control device has a throttling mechanism (40) arranged in the suction pipe on the upstream side of the handled liquid from the inducer. The throttling mechanism has at least one throttling member (41, 42) that protrudes from the inner surface side of the suction pipe into the suction pipe along the transverse direction of the suction pipe, thereby changing the axial flow rate of the handled liquid flowing into the inducer on the upstream side of the inducer. The amount of protrusion of the throttling member from the inner surface into the suction pipe is variably controlled based on flow rate information related to the flow rate of the handled liquid discharged from the centrifugal pump. [Selected Figure] Figure 2

Description

The present invention relates to a flow rate control device and a centrifugal pump.

In order to improve the suction performance of a centrifugal pump, a technique is known in which an inducer is disposed upstream of the impeller (upstream in the flow of the handled liquid in the suction pipe) (see, for example, Patent Document 1). The inducer is designed to be used in a narrow specific operating flow rate range. That is, for example, the inlet angle of the inducer vane is designed so that the handled liquid flows in at an attack angle of several degrees with respect to the inflow angle of the handled liquid at the maximum efficiency point (Q _bep ) of the discharge flow rate. Here, the inflow angle of the handled liquid is expressed as a function of the velocity of the handled liquid in the axial direction of the suction pipe (axial flow velocity) and the circumferential speed of the handled liquid, and increases or decreases according to an increase or decrease in the axial flow velocity.

U.S. Pat. No. 4,150,916

Generally, the flow rate (discharge flow rate) of a centrifugal pump is adjusted by controlling the rotation speed of the impeller (inducer) using an inverter and the opening of a valve (discharge valve) attached to the discharge pipe. Here, as described below, when only the flow rate is restricted by reducing the opening of the discharge valve, the inflow angle of the handled liquid into the inducer vanes becomes smaller. As a result, the difference between the inflow angle and the inlet angle of the inducer vanes becomes larger, and ultimately, the handled liquid peels off from the surface of the inducer vanes, deteriorating the suction performance of the centrifugal pump. Thus, in a small flow rate range smaller than a specific operating flow rate range, the suction performance of a centrifugal pump equipped with an inducer deteriorates.

The present invention aims to expand the operating flow range of a centrifugal pump equipped with an inducer to the low flow range.

In one embodiment of the present invention, the flow rate control device is a flow rate control device that controls the axial flow rate of the handled liquid flowing in the suction pipe of a centrifugal pump equipped with an inducer, and includes a throttling mechanism arranged upstream of the inducer in the flow of the handled liquid in the suction pipe, and the throttling mechanism includes at least one throttling member that protrudes from the inner surface of the suction pipe into the suction pipe along the transverse direction of the suction pipe to change the axial flow rate of the handled liquid flowing into the inducer upstream of the inducer, and the amount of protrusion of the throttling member from the inner surface into the suction pipe is variably controlled based on flow rate information related to the flow rate of the handled liquid discharged from the centrifugal pump.

The centrifugal pump in one embodiment of the present invention comprises a rotating shaft, an impeller attached to one end of the rotating shaft, a suction pipe for introducing the handled liquid to be sucked into the impeller, an inducer disposed within the suction pipe, and a flow rate control device as described in the above embodiment that is attached to the suction pipe and controls the axial flow rate of the handled liquid flowing within the suction pipe.

According to the present invention, the operating flow range of a centrifugal pump equipped with an inducer is expanded to the low flow range.

FIG. 1 is a schematic piping diagram of a pump system including a centrifugal pump according to the present invention. 1 is a schematic cross-sectional view showing an embodiment of a centrifugal pump according to the present invention. 1 is a schematic diagram showing an embodiment of a flow rate control device according to the present invention; 4 is a schematic cross-sectional view showing a state in which a throttle member included in the flow rate control device of FIG. 3 protrudes into a suction pipe included in the centrifugal pump of FIG. 2 . 3 is a schematic diagram illustrating an inflow angle of a pumped liquid in a region adjacent to the upstream side of an inducer included in the centrifugal pump of FIG. 2 . FIG. 5A and 5B are schematic diagrams showing the effect of the protrusion of the diaphragm member in FIG. 4 and the amount of protrusion. FIG. 13 is a schematic diagram showing an example of an aperture ratio with respect to a flow rate. FIG. 5 is a schematic cross-sectional view taken along line AA in FIG. 4 . FIG. 5 is a schematic perspective view of the suction pipe of FIG. 4 . 1A is a schematic diagram illustrating a conventional suction pipe, and FIG. 1B is a schematic diagram illustrating the suction pipe of the present invention. 5A and 5B are schematic cross-sectional views showing each modified example of the flow rate control device of FIG. 3, where (a) is a schematic cross-sectional view showing a first modified example, (b) is a schematic cross-sectional view showing a second modified example, (c) is a schematic cross-sectional view showing a third modified example, (d) is a schematic cross-sectional view showing a fourth modified example, (e) is a schematic cross-sectional view showing a fifth modified example, and (f) is a schematic cross-sectional view showing a sixth modified example. 12 is a schematic cross-sectional view illustrating the flow of handled fluid flowing into a through hole provided in the flow rate control device according to the second modified example of FIG. 11 . FIG. 13 is a schematic piping diagram of a seventh modified example of the flow rate control device of FIG. 3 .

Below, an embodiment of the flow rate control device and centrifugal pump according to the present invention will be described with reference to the drawings. In each drawing, the same members and elements are given the same reference numerals, and duplicated explanations will be omitted. In addition, the dimensional ratios of each element may be exaggerated for the convenience of explanation, and are not limited to the ratios shown in each drawing.

In the following description, the centrifugal pump according to the present invention is assumed to be provided in a pump system that transfers a handled liquid from a storage tank to an external facility or device. The flow rate control device according to the present invention is assumed to be provided in the centrifugal pump according to the present invention.

●Pump system●
Configuration of the Pump System FIG. 1 is a schematic piping diagram of a pump system including a centrifugal pump according to the present invention.
In the figure, the solid lines indicate the flow paths of the pumped fluid, and the dashed lines indicate the paths of signals.

The pump system S includes a storage tank T in which the handled liquid is stored, a suction pipe L11 connected between the storage tank T and the centrifugal pump 1, a suction valve V1 that opens and closes the suction pipe L11, a discharge pipe L12 connected between the centrifugal pump 1 and an external device O, a discharge valve V2 that opens and closes the discharge pipe L12, and the centrifugal pump 1. The centrifugal pump 1 is an example of a centrifugal pump according to the present invention.

The suction pipe L11 is a known pipe body, and together with the suction pipe 35 described below, constitutes the suction flow path L1 through which the handled liquid flows and is sucked into the pump chamber 33 described below. The discharge pipe L12 is a known pipe body, and together with the discharge pipe 36 described below, constitutes the discharge flow path L2 through which the handled liquid flows and is discharged from the pump chamber 33. The suction valve V1 and the discharge valve V2 are known valves (e.g., solenoid valves) and are configured so that their opening can be adjusted by remote control (the flow rate can be adjusted). The discharge valve V2 is an example of a flow rate adjustment device in the present invention.

The external device O is a device that uses and stores the handled liquid pumped by the centrifugal pump 1, such as an engine, a combustion furnace, or a fuel tank. In this embodiment, the external device O generates a control signal that controls the opening degree of the discharge valve V2, and transmits the generated control signal to the discharge valve V2 and the control device 60 described below. The control signal is an example of a flow rate control signal in the present invention.

●Centrifugal pump●
Next, an embodiment of a centrifugal pump according to the present invention will be described.

Configuration of Centrifugal Pump FIG. 2 is a schematic cross-sectional view showing an embodiment of a centrifugal pump according to the present invention.
For ease of explanation, part of the centrifugal pump 1 is omitted in the figure.

The centrifugal pump 1 comprises a motor section 2, a pump section 3, and a flow rate control device 4. The centrifugal pump 1 is an example of a centrifugal pump according to the present invention.

In the following description, the "forward direction" refers to the direction in which the pump section 3 is located relative to the motor section 2, and the "rearward direction" refers to the direction in which the motor section 2 is located relative to the pump section 3. The "upstream side" refers to the upstream side in the flow of the liquid (hereinafter referred to as the "handled liquid") being pumped to the centrifugal pump 1, and the "downstream side" refers to the downstream side in the flow of the handled liquid.

The motor unit 2 is driven at a predetermined drive voltage and drive frequency to rotate the impeller 32, which will be described later. The motor unit 2 includes a housing 21, a motor 22, and a rotating shaft 23.

The housing 21 houses the motor 22 and the rotating shaft 23. The motor 22 is a known motor consisting of a rotor (not shown) attached to the rotating shaft 23, and a stator (not shown) that rotates the rotor. The rotating shaft 23 rotates with the rotation of the motor 22, and transmits the rotational power to the impeller 32 described below. The rotating shaft 23 is cylindrical in shape. The front end 23a of the rotating shaft 23 protrudes into the pump chamber 33 described below.

The pump section 3 draws in and discharges the pumped liquid. The pump section 3 includes a housing 31, an impeller 32, a pump chamber 33, an inducer 34, a suction pipe 35, and a discharge pipe 36.

The housing 31 defines a pump chamber 33 that houses the impeller 32. The front end of the housing 31 extends forward so as to be coaxial with the rotating shaft 23, forming a suction pipe 35 that draws (introduces) the handled liquid into the pump chamber 33. In addition, a portion of the housing 31 that is located radially outward of the impeller 32 extends in the tangential direction (upward) of the impeller 32, forming a discharge pipe 36 that discharges the handled liquid from the pump chamber 33. In other words, the housing 31 constitutes the pump chamber 33, the suction pipe 35, and the discharge pipe 36.

The impeller 32 is attached to the front end 23a of the rotating shaft 23 and is housed in the pump chamber 33.

The inducer 34 is disposed upstream (forward) of the impeller 32 in the suction pipe 35, and pressurizes the handled liquid to assist the impeller 32 in suctioning the handled liquid. The inducer 34 is a known inducer that includes an inducer shaft 34a that extends upstream (forward) from the front end 23a of the rotating shaft 23, and inducer blades 34b that are attached to the outer circumferential surface of the inducer shaft 34a. The inducer 34 is attached to the front end 23a of the rotating shaft 23, and is disposed in the suction pipe 35.

The shape of the suction pipe 35 is, for example, cylindrical. The upstream (front) end of the suction pipe 35 is connected to the suction piping L11, which constitutes the suction flow path L1 together with the suction pipe 35. The suction pipe 35 has storage chambers 35a and 35b and slits 35c and 35d.

In the following description, the "circumferential direction" refers to the direction along the circumference of the suction pipe 35, the "radial direction" refers to the direction along the diameter (radius) of the suction pipe 35, and the "axial direction" refers to the axial direction (extension direction) of the suction pipe 35.

A part of the peripheral wall of the suction pipe 35 protrudes radially outward to form the accommodation chambers 35a, 35b that accommodate the throttling members 41, 42 described later. In this embodiment, the accommodation chamber 35a is disposed above the suction pipe 35, and the accommodation chamber 35b is disposed below the suction pipe 35. That is, in the radial direction, the accommodation chambers 35a, 35b are disposed so as to sandwich the suction pipe 35. In other words, in the circumferential direction, the accommodation chambers 35a, 35b are disposed evenly at 180° intervals. In the axial direction, the accommodation chambers 35a, 35b are disposed upstream (forward) of the inducer 34 (inducer vanes 34b).

Slits 35c and 35d are passages that connect suction pipe 35 with storage chambers 35a and 35b. Slits 35c and 35d are formed in the peripheral wall of suction pipe 35. In the circumferential direction, slit 35c is located at the same position as storage chamber 35a, and slit 35d is located at the same position as storage chamber 35b. In the radial direction, slit 35c is located on the inner side of storage chamber 35a, and slit 35d is located on the inner side of storage chamber 35b. Slit 35c opens to suction pipe 35 and storage chamber 35a, and slit 35d opens to suction pipe 35 and storage chamber 35b.

The shape of the discharge pipe 36 is, for example, a horn shape in which the inner diameter increases toward the downstream side (upper side) of the discharge pipe 36. The upper end (downstream end) of the discharge pipe 36 is connected to the discharge piping L12, which constitutes the discharge flow path L2 together with the discharge pipe 36.

Configuration of Flow Velocity Control Device FIG. 3 is a schematic configuration diagram showing an embodiment of the flow velocity control device 4. As shown in FIG.
For ease of explanation, the drawing also illustrates the suction pipe 35 .

The flow rate control device 4 controls the flow rate (hereinafter referred to as "axial flow rate") of the handled liquid flowing in the axial direction (hereinafter referred to as "axial flow") through the suction pipe 35. The flow rate control device 4 is an example of a flow rate control device according to the present invention. The flow rate control device 4 includes a throttling mechanism 40, a drive device 50, and a control device 60.

The aperture mechanism 40 has multiple aperture members 41, 42 (two in this embodiment).

The throttle members 41, 42 protrude from the inner surface side of the suction pipe 35 into the suction pipe 35 along the transverse direction (i.e., radial direction) of the suction pipe 35, thereby changing the axial flow velocity of the handled liquid flowing into the inducer 34 upstream of the inducer 34. When viewed in the axial direction, the throttle members 41, 42 have, for example, a rectangular plate shape. The throttle members 41, 42 are made of metal such as stainless steel. The throttle members 41, 42 are accommodated in the accommodation chambers 35a, 35b with both sides facing the axial direction (front-back direction). That is, the throttle members 41, 42 are arranged upstream of the inducer 34 and are evenly arranged at 180° intervals in the circumferential direction. In addition, the throttle members 41, 42 are configured not to abut against each other even when they protrude into the suction pipe 35 in the circumferential direction. In the axial view, the end 41a of the throttling member 41 on the suction pipe 35 side is a straight line parallel to the tangent of the circle formed by the inner surface of the suction pipe 35. Similarly, the end 42a of the throttling member 42 on the suction pipe 35 side is a straight line parallel to the tangent of the circle formed by the inner surface of the suction pipe 35. The end 41a of the throttling member 41 faces the end 42a of the throttling member 42. That is, the throttling members 41 and 42 are arranged on the same imaginary plane perpendicular to the axial direction in the suction pipe 35 (the same position of the suction pipe 35 in the axial direction). The length of the end 41a and 42a is, for example, approximately the same as the inner diameter of the suction pipe 35. Therefore, in the axial view, the throttling members 41 and 42 protrude into the suction pipe 35 so that the end 41a and 42a define the chord of the circle formed by the inner surface of the suction pipe 35. In the following description, the position in the suction pipe 35 where the throttling members 41, 42 are located in the axial direction is referred to as the "throttling position P."

The throttle members 41 and 42 are controlled to be able to move back and forth radially outward and inward by the driving force from the drive unit 50 based on the flow rate information described later. That is, the throttle members 41 and 42 can move back and forth along the transverse direction of the suction pipe 35. That is, a part (lower part) and an end 41a of the throttle member 41 can move (protrude) from the inner surface side of the suction pipe 35 into the suction pipe 35 through the slit 35c, and can move (contain) from the inside of the suction pipe 35 into the accommodation chamber 35a. Similarly, a part (upper part) and an end 42a of the throttle member 42 can move (protrude) from the inner surface side of the suction pipe 35 into the suction pipe 35 through the slit 35d, and can move (contain) from the inside of the suction pipe 35 into the accommodation chamber 35b. When the throttle members 41 and 42 are positioned at the outermost radial side, the throttle members 41 and 42 do not protrude into the suction pipe 35.

The drive unit 50 moves the throttling members 41, 42 in the transverse direction of the suction pipe 35. The drive unit 50 includes, for example, a known device (e.g., a motor, etc.) that generates a driving force to move the throttling members 41, 42, and a known mechanism (e.g., a crank mechanism, a gear mechanism, etc.) that transmits the driving force to the throttling members 41, 42.

The control device 60 controls the operation of the drive device 50 based on the flow rate information described below, to move the throttle members 41, 42. The control device 60 includes, for example, a processor such as a CPU (Central Processing Unit), a volatile memory such as a RAM (Random Access Memory) that functions as a working area for the CPU, and a non-volatile memory such as a ROM (Read Only Memory) that stores various information (programs, etc.).

"Flow rate information" is information related to the flow rate (discharge flow rate) of the handled fluid discharged from the centrifugal pump 1 and flowing through the discharge flow path L2. The flow rate information includes, for example, information indicating the flow rate of the handled fluid (discharge flow rate information) and information controlling the operation of a device (e.g., discharge valve V2) that controls the flow rate of the handled fluid flowing through the discharge flow path L2 (operation control information). As described above, in this embodiment, the flow rate information is a control signal that is generated by the external device O and transmitted to the control device 60 to control the opening degree of the discharge valve V2. In this embodiment, the ROM included in the control device 60 stores, for example, a table in which the opening degree (flow rate) of the discharge valve V2 and the protrusion amount (e.g., the area of the protruding portion) of the throttling members 41, 42 are associated with each other.

In the present invention, the ROM of the control device 60 may store a function for calculating the protrusion amount of the throttling members 41, 42 corresponding to the opening degree (flow rate) of the discharge valve V2 instead of a table.

In addition, in the present invention, the control device 60 may be equipped with a storage device (e.g., flash memory, etc.) that stores tables and functions.

Control of Axial Flow Velocity by Flow Velocity Control Device Fig. 4 is a schematic cross-sectional view showing a state in which the throttle members 41, 42 protrude into the suction pipe 35. In the following description, for convenience of explanation, Figs. 1 and 2 will also be referred to.

When the throttling members 41, 42 protrude into the suction pipe 35, at the throttling position P, the cross-sectional area (cross-sectional area perpendicular to the axial direction: the area of the region colored gray in FIG. 4 ) of the internal space S1 of the suction pipe 35 decreases according to the protrusion amount of the throttling members 41, 42. Here, the axial flow velocity "V _m " of the handled fluid flowing (passing) through the suction pipe 35 (throttling position P) is expressed as a function of the following equation (1).

_Vm = Q/A (1)

Here, "Q" is the flow rate (discharge flow rate) of the handled fluid flowing through the discharge flow passage L2, and "A" is the cross-sectional area of the internal space S1 of the suction pipe 35 (throttling position P). The cross-sectional area "A" decreases as the throttling members 41, 42 protrude into the suction pipe 35, and increases as the throttling members 41, 42 are accommodated in the accommodation chambers 35a, 35b.

As shown in formula (1), the axial flow velocity "V _m " of the handled fluid flowing through the suction pipe 35 (throttle position P) increases and decreases inversely proportional to the cross-sectional area "A". That is, the axial flow velocity increases as the throttling members 41, 42 protrude into the suction pipe 35, and decreases as the throttling members 41, 42 are accommodated in the accommodation chambers 35a, 35b. In this way, the flow velocity control device 4 controls the axial flow velocity of the handled fluid flowing through the suction pipe 35 (throttle position P) by controlling the protrusion amount of the throttling members 41, 42.

Furthermore, as shown in formula (1), the axial flow velocity "V _m " increases or decreases in proportion to the flow rate "Q" of the handled fluid flowing through the discharge flow path L2. Generally, the flow rate of a centrifugal pump is adjusted by controlling the rotation speed using an inverter and the opening degree of the discharge valve. In this embodiment, when the flow rate is adjusted by the opening degree of the discharge valve V2, the axial flow velocity increases or decreases according to the increase or decrease in the flow rate. That is, the flow rate decreases as the discharge valve V2 is closed and increases as the discharge valve V2 is opened.

When the centrifugal pump 1 is pumping the handled liquid, the flow path of the handled liquid from the suction flow path L1 (throttle position P) to the discharge flow path L2 (discharge valve V2) is filled with the handled liquid. The volume of this flow path is constant, and the volume of the handled liquid in this flow path is also considered to be constant. Therefore, when the flow rate (mass) of the handled liquid discharged decreases, in accordance with the law of conservation of mass, the flow rate (mass) of the handled liquid sucked in also decreases. As a result, the axial flow velocity also decreases.

FIG. 5 is a schematic diagram for explaining the inflow angle of the handled fluid in the region (inlet region) adjacent to the upstream side of the inducer 34. As shown in FIG.
The figure shows a schematic diagram of the internal space S1 of the suction pipe 35 and the inducer 34 deployed in the circumferential direction.

The "inflow angle" is the angle at which the handled liquid flows into the inducer vane 34b relative to the rotational direction (circumferential direction) of the inducer 34.

As shown in Fig. 5, since the inducer vane 34b is fixed to the inducer shaft 34a, the inlet angle "β1" of the inducer vane 34b is a fixed value for each position of the inducer vane 34b in the radial direction. Here, the "inlet angle "β1"" is the angle of the inducer vane 34b with respect to the rotation direction of the inducer 34. The inlet angle "β1" is designed to be approximately the same as the inflow angle of the handled liquid at the maximum efficiency point (Q _bep ) of the flow rate. Also, the inlet angle "β1" is designed to increase from the outer edge of the inducer vane 34b toward the center.

The inflow angle "β _w1 " of the pumped fluid is expressed as a function of the following equation (2).

β _w1 =tan ⁻¹ (V _m1 /u1) (2)

Here, "u1" is the circumferential velocity (flow velocity in the circumferential direction) of the handled liquid in the inlet region.

When the flow rate is adjusted by the opening degree of the discharge valve V2, the rotation speed of the impeller 32 (inducer 34) is constant, and therefore the peripheral speed "u1" is also constant. Therefore, as shown in the formula (2), the inflow angle "β _w1 " decreases as the axial flow velocity "V _m1 " decreases, and increases as the axial flow velocity "V _m1 " increases. Therefore, when the flow rate decreases by closing the discharge valve V2, the axial flow velocity "V _m1 " decreases from "V1" to "V2", and the inflow angle "β _w1 " decreases from "X1°" to "X2°". Then, the difference between the inflow angle "β _w2 " and the inlet angle "β1" becomes large. As a result, the optimal angle of the inflow angle "β _w1 " with respect to the inlet angle "β1" of the handled liquid is not maintained. At this time, separation of the handled liquid from the surface of the inducer vane 34b occurs, and the suction performance of the centrifugal pump 1 deteriorates. Therefore, the flow velocity control device 4 controls the axial flow velocity to be constant by increasing or decreasing the cross-sectional area of the suction pipe 35 (throttle position P) according to the opening degree (i.e., flow rate) of the discharge valve V2. That is, the control device 60 controls the protrusion amount of the throttle members 41, 42 so that it increases as the opening degree (flow rate) of the discharge valve V2 decreases and decreases as the opening degree (flow rate) of the discharge valve V2 increases. In other words, the flow velocity control device 4 controls the axial flow velocity so that the optimal angle of the inflow angle "β _w1 " relative to the inlet angle "β1" is maintained.

FIG. 6 is a schematic diagram showing the effect of the protrusion of the diaphragm members 41 and 42 and the amount of protrusion.
In the graph of the figure, the horizontal axis indicates the flow rate, and the vertical axis indicates NPSHr (Net Positive Suction Head required). The solid line indicates the change in NPSHr with respect to the flow rate when the throttle members 41, 42 are not protruding, and the dashed line indicates the same change when the throttle members 41, 42 are protruding. The figure also shows the protrusion amount of the throttle members 41, 42 from the suction pipe 35.

As shown in FIG. 6, when the throttle members 41 and 42 are not protruding, the NPSHr decreases as the flow rate decreases, but when the flow rate decreases below a certain value, it starts to increase. Below the flow rate at which the change in NPSHr bottoms out, the optimal angle of the inlet angle relative to the inlet angle is no longer maintained, and the above-mentioned separation occurs. Therefore, the flow rate control device 4 protrudes the throttle members 41 and 42 into the suction pipe 35 as the flow rate decreases, for example, starting from the flow rate at which the bottom occurs (first flow rate), so that the ratio of the flow rate to the cross-sectional area is kept constant. The protrusion amount of the throttle members 41 and 42 increases continuously as the flow rate decreases in a predetermined flow rate range up to the second flow rate (for example, a flow rate at which the NPSHr is approximately equal to the maximum efficiency point). As a result, in a flow rate range smaller than the first flow rate, the optimal angle of the inlet angle relative to the inlet angle is maintained, the above-mentioned separation is suppressed, and the increase in the NPSHr is suppressed.

FIG. 7 is a schematic diagram showing an example of the aperture ratio with respect to the flow rate.
In the figure, the horizontal axis indicates the flow rate, and the vertical axis indicates the aperture ratio.

The "opening ratio" is the ratio of the cross-sectional area when the aperture members 41, 42 are protruding to the cross-sectional area when the aperture members 41, 42 are not protruding at the aperture position P.

As mentioned above, the inlet angle is designed to be approximately the same as the inflow angle of the handled fluid at the most efficient point of the flow rate. The inducer vane 34b is also designed to be effective in a predetermined operating flow rate range centered on the most efficient point. Therefore, the optimal angle has a predetermined angle range according to the design range. Therefore, even if the flow rate becomes smaller than the most efficient point, the throttle members 41 and 42 are controlled not to protrude while the inlet angle is maintained at the optimal angle. In the example shown in FIG. 7, the throttle members 41 and 42 are controlled to start protruding at a flow rate of about 60% and to protrude to the maximum amount at a flow rate of about 20%. The protrusion amount of the throttle members 41 and 42 is controlled to increase as the flow rate decreases within the range of about 60% to about 20%.

FIG. 8 is a schematic cross-sectional view taken along line AA in FIG.
In the figure, the flow of the pumped fluid along the axial direction (axial flow) is indicated by arrows, and the figure also simplifies the illustration of the inducer 34. In the following description in which Fig. 8 is referred to, Fig. 4 will also be referred to as appropriate.

In this embodiment, the flow control device 4 is equipped with two throttle members 41, 42, which are arranged at 180° intervals in the circumferential direction and do not abut each other. Therefore, when the throttle members 41, 42 protrude into the suction pipe 35 in the axial direction, a region where the throttle members 41, 42 protrude (hereinafter referred to as the "protruding region") and a region where the throttle members 41, 42 do not protrude (hereinafter referred to as the "non-protruding region") are formed at the throttle position P. In the protruding region, the effective inner diameter of the suction pipe 35 is reduced by the throttle members 41, 42, and the axial flow is blocked. Therefore, downstream of the protruding region, the axial flow is made non-uniform and the axial flow velocity is reduced. That is, an axial flow with a non-uniform axial flow velocity is flowing into the tip (the radially outer end) of the inducer blade 34b located downstream of the protruding region. Therefore, downstream of the protruding region, the suction performance of the inducer 34 is reduced. On the other hand, in the non-projecting region, the flow of the handled liquid along the axial direction is not blocked. Therefore, a uniform axial flow flows onto the entire surface of the inducer vane 34b located downstream of the non-projecting region. Therefore, downstream of the non-projecting region, the suction performance of the inducer 34 does not decrease.

Figure 9 is a schematic perspective view of the suction pipe 35.

In the figure, the arrows indicate the flow of the handled liquid located on the inner surface side (radial outer side) of the suction pipe 35. When the flow rate is large, most of the handled liquid flows straight along the suction pipe 35 as a uniform axial flow that has only a component that flows along the axial direction (axial component). On the other hand, when the flow rate is small, the flow of the handled liquid is affected by the rotation of the inducer 34 just before the inducer 34. Here, the blade circumferential speed of the inducer blade 34b is zero at the center of rotation, but increases toward the radial outer side. As a result, a part of the handled liquid located on the inner surface side (radial outer side) of the suction pipe 35 becomes a swirling flow that flows in the axial direction while swirling in the circumferential direction. The swirling flow flows while swirling in the circumferential direction at a flow speed of about several tens of percent of the circumferential speed of the inducer blade 34b.

After passing through the non-projecting region, a portion of the swirling flow flows downstream of the projecting region and into the inducer vane 34b located downstream of the projecting region. At this time, the same portion flows into the tip of the inducer vane 34b located downstream of the projecting region at an axial flow velocity approximately equal to that of the axial flow that passed through the non-projecting region (solid arrow in Figure 9). Therefore, the deterioration of the suction performance of the inducer 34 downstream of the projecting region described above is slightly suppressed. Meanwhile, the other portion of the swirling flow that cannot pass through the non-projecting region is blocked by the throttle members 41, 42 (chain line arrow in Figure 9).

In this way, the flow rate control device 4 forms protruding and non-protruding regions to reduce the cross-sectional area and control the axial flow rate while suppressing a decrease in suction performance.

Relationship with backflow of handled liquid Figure 10 is a schematic diagram explaining backflow of handled liquid, where (a) is a schematic diagram showing a conventional suction pipe in which no measures against backflow are taken on the upstream side of the inducer, and (b) is a schematic diagram showing the suction pipe 35 of the present invention.

Generally, when a centrifugal pump equipped with an inducer is operated in the low flow rate range and at low NPSHr, backflow of the handled liquid may occur on the outer periphery of the inducer. When backflow occurs, the handled liquid, whose temperature has risen due to mixing loss in the impeller, is sent to the upstream side of the inducer. At this time, cavitation occurs at the tip of the inducer blade. The cavitation bubbles are sent to the upstream side of the inducer by the backflow and form a gas pool, and when the gas pool disappears, it causes pulsation on the upstream side of the inducer.

To prevent this backflow, a technique is known in which an annular member (so-called orifice) protruding from the inner circumferential surface of the suction pipe is arranged in the suction pipe upstream of the inducer, as described in Patent Document 1. This technique can suppress the increase in the backflow area (backflow area) upstream when the centrifugal pump is operated in a predetermined small flow rate range. However, since the size (protrusion amount) of the annular member is determined by the shape and flow rate of the suction pipe, the flow rate range that can be handled by one annular member is limited. Therefore, in this technique, when the flow rate becomes smaller than the applicable flow rate range, the effect of suppressing the increase in the backflow area decreases, and the suction performance deteriorates. On the other hand, when the flow rate becomes larger than the applicable flow rate range, the annular member obstructs the flow of the handled liquid, and the suction performance deteriorates. In other words, this technique can only handle a predetermined small flow rate range, and cannot handle a wide range of flow rates other than the predetermined flow rate range.

In this embodiment, the throttling members 41, 42 have the function of suppressing the increase of the backflow area, similar to the annular member described above. In addition, the amount of protrusion of the throttling members 41, 42 increases as the flow rate decreases, decreases as the flow rate increases, and becomes zero when the flow rate exceeds a predetermined flow rate. In this way, in the small flow rate range, the amount of protrusion of the throttling members 41, 42 changes depending on the flow rate, suppressing backflow, and in the large flow rate range, the flow of the handled fluid is not obstructed because the throttling members 41, 42 do not protrude.

In addition, the backflow is discontinuous (unsteady) in the circumferential direction, and the throttling members 41, 42 also do not protrude all around, and are discontinuous in the circumferential direction. Compared to an annular member that protrudes all around in the circumferential direction, the throttling members 41, 42, which also have discontinuities, are more effective at suppressing discontinuous backflow and suppressing the increase in the backflow area.

●Summary●
According to the embodiment described above, the flow rate control device 4 includes the throttle mechanism 40 disposed in the suction pipe 35 upstream of the inducer 34. The throttle mechanism 40 includes throttle members 41, 42 that protrude from the inner surface of the suction pipe 35 into the suction pipe 35 in the transverse direction to change the axial flow rate of the handled fluid flowing into the inducer 34 upstream of the inducer 34. The protrusion amount of the throttle members 41, 42 is variably controlled based on flow rate information related to the flow rate of the handled fluid discharged from the centrifugal pump 1. According to this configuration, the flow rate control device 4 can change the protrusion amount of the throttle members 41, 42 according to the flow rate to change the cross-sectional area at the throttle position P. Therefore, when the flow rate decreases, the flow rate control device 4 changes the cross-sectional area according to the flow rate, so that the axial flow rate at the throttle position P becomes constant. As a result, even if the flow rate decreases, the optimal angle of the inlet angle relative to the inlet angle is maintained, and the operating flow rate range of the centrifugal pump 1 including the inducer 34 is expanded to the small flow rate region side.

In addition, according to the embodiment described above, the protrusion amount of the throttling members 41, 42 is controlled so that it increases as the flow rate decreases. With this configuration, the cross-sectional area of the throttling position P decreases as the flow rate decreases, and the axial flow velocity at the throttling position P is maintained constant. As a result, even if the flow rate decreases, the optimal angle of the inlet angle relative to the inlet angle is maintained, and the operating flow rate range of the centrifugal pump 1 equipped with the inducer 34 is expanded toward the small flow rate region.

Furthermore, according to the embodiment described above, a discharge valve V2 that adjusts the flow rate of the handled liquid flowing through the discharge pipe 36 is attached to the discharge pipe 36 through which the handled liquid discharged from the centrifugal pump 1 flows. The flow rate information is control information that controls the operation of the discharge valve V2 transmitted from the external device O. According to this configuration, the flow rate control device 4 can control the axial flow rate in conjunction with the flow rate control for the discharge valve V2.

Furthermore, according to the embodiment described above, the throttling mechanism 40 includes two throttling members 41, 42 that are arranged at equal angular intervals (e.g., 180°) in the circumferential direction of the suction pipe 35. With this configuration, the flow rate control device 4 can easily form not only protruding regions but also non-protruding regions in the circumferential direction. Because the suction performance of the inducer 34 and impeller 32 does not decrease downstream of the non-protruding regions, the flow rate control device 4 can control the axial flow rate while suppressing the decrease in suction performance.

Furthermore, according to the embodiment described above, the throttling mechanism 40 includes two throttling members 41, 42 arranged to face each other. With this configuration, the flow rate control device 4 can form a wide non-protruding region while suppressing the amount of protrusion required to reduce the cross-sectional area.

Furthermore, according to the embodiment described above, when the throttling members 41, 42 protrude into the suction pipe 35, the adjacent throttling members 41, 42 do not come into contact with each other in the circumferential direction. With this configuration, a non-protruding region is reliably formed between the adjacent throttling members 41, 42 in the circumferential direction.

●Variations●
Next, modified examples of the flow rate control device 4 will be described below, focusing on the differences from the previously described embodiment (hereinafter referred to as the "first embodiment"). In the following description of the modified examples, for convenience of explanation, the same members as those in the first embodiment and members having common functions are given the same reference numerals as those in the first embodiment. In the following modified examples, reference will be made to Figures 1 to 9 as appropriate.

FIG. 11 is a schematic cross-sectional view showing each modified example of the flow rate control device 4, where (a) is a schematic cross-sectional view showing a first modified example, (b) is a schematic cross-sectional view showing a second modified example, (c) is a schematic cross-sectional view showing a third modified example, (d) is a schematic cross-sectional view showing a fourth modified example, (e) is a schematic cross-sectional view showing a fifth modified example, and (f) is a schematic cross-sectional view showing a sixth modified example.
This figure shows the state in which the throttle members 41 to 48 protrude to the maximum extent.

11(a), the first modified example differs from the first embodiment in that the flow rate control device 4 includes one throttling member 41. The protrusion amount of the throttling member 41 in the first modified example relative to the flow rate is greater than the protrusion amounts of the throttling members 41 and 42 in the first modified example relative to the flow rate. The flow rate range in which the axial flow rate can be controlled in the first modified example may be smaller than in the first embodiment, but the flow rate control device 4 according to the first modified example can appropriately control the axial flow within that flow rate range.

In the first modified example, the flow rate control device 4 may include one throttle member 42.

11B, the second modification is different from the first embodiment in that each of the throttle members 41, 42 has a plurality of (three in the second modification) circular through holes 41b, 41c, 41d, 42b, 42c, 42d. The through holes 41b to 41d are holes that penetrate the throttle member 41 in the axial direction and are arranged at equal intervals along the end 41a. The through holes 42b to 42d are holes that penetrate the throttle member 42 in the axial direction and are arranged at equal intervals along the end 42a. The through holes 41b to 42d are arranged in the throttle members 41, 42 so that all of the through holes 41b to 42d are exposed in the suction pipe 35 at least before the throttle members 41, 42 protrude to the maximum extent.

Figure 12 is a schematic cross-sectional view illustrating the flow of the handled fluid into the through-hole 41b.

When the through hole 41b is exposed in the suction pipe 35, a part of the axial flow flows into the through hole 41b. Also, a part of the swirling flow flowing on the inner peripheral surface side of the suction pipe 35 flows into the through hole 41b. Since the swirling flow flows in the axial direction while swirling, the swirling flow collides with the inner surface of the through hole 41b and changes direction to the axial direction. Then, the swirling flow that has changed direction flows downstream as an axial flow together with the axial flow that has flowed into the through hole 41b. Therefore, the swirling flow that has passed through the through hole 41b flows into the tip of the inducer vane 34b as an axial flow. As a result, the axial flow is made uniform downstream of the throttling position P, and the suction performance of the inducer 34 is improved compared to the first embodiment.

In addition, when the pumped fluid flows backward, the through-hole 41b also attenuates the swirling component of the pumped fluid that flows backward. Then, part of the backflow area is drawn into the axial flow that passes through the through-hole 41b. As a result, the increase in the backflow area upstream of the throttling members 41 and 42 is further suppressed.

In the second modified example, the other through holes 41c to 42d function in the same way as through hole 41b and provide the same effect.

In addition, in the second modified example, the shape, number, and size of the through holes 41b to 42d are set appropriately according to the corresponding flow rate.

Furthermore, in the second modified example, either one of the aperture members 41, 42 may not have the through holes 41b to 42d.

3rd Modification As shown in Fig. 11(c), in the third modification, the size of the throttle members 41, 42 is different from that of the first embodiment. Specifically, the length of the end portions 41a, 42a is set to be smaller than the inner diameter of the suction pipe 35, for example (about 2/3 of the length in the example shown in Fig. 11(c)). Therefore, from when the throttle members 41, 42 start to protrude until all of the end portions 41a, 42a are exposed in the suction pipe 35, the throttle members 41, 42 protrude into the suction pipe 35 in the axial direction so that the end portions 41a, 42a define a chord of a circle formed by the inner surface of the suction pipe 35. On the other hand, after all of the end portions 41a, 42a are exposed in the suction pipe 35, a quarter-circular gap S2 is formed between the throttle members 41, 42 and the suction pipe 35 in the axial direction. In this configuration, the flow velocity control device 4 functions in the same manner as in the first embodiment until all of the ends 41a, 42a are exposed in the suction pipe 35. On the other hand, after all of the ends 41a, 42a are exposed in the suction pipe 35, the axial flow also passes through the gap S2. The gap S2 also functions in the same manner as the through hole 41b in the second embodiment. That is, the swirling flow that has become an axial flow due to the gap S2 flows into the tip of the inducer vane 34b located downstream of the gap S2. As a result, the axial flow is made uniform downstream of the throttling position P, and the suction performance of the inducer 34 is slightly improved compared to the first embodiment.

● Fourth Modification As shown in FIG. 11(d), in the fourth modification, the protruding amount of the throttle members 41 and 42 is different from that of the first embodiment. Specifically, the protruding amount of the throttle member 41 is different from that of the throttle member 42 and is smaller than that of the throttle member 42. In this configuration, only the throttle member 41 starts to protrude first in response to a decrease in the flow rate. At this time, the flow rate control device 4 functions in the same manner as the flow rate control device 4 according to the first modification. Next, the throttle member 42 starts to protrude. At this time, the throttle member 41 protrudes more than in the first embodiment, and the throttle member 42 does not protrude more than in the first embodiment. Therefore, in the axial view, less axial flow flows into the tip portions (radially outer ends) of the inducer 34 and part of the impeller 32 located downstream of the throttle member 41 than in the first embodiment. On the other hand, more axial flow flows into the tip portions (radially outer ends) of the inducer 34 and part of the impeller 32 located downstream of the throttle member 42 than in the first embodiment. As a result, the decrease in the suction performance of the inducer 34 and the impeller 32 downstream of the protruding region is suppressed to approximately the same level as in the first embodiment.

In addition, in this configuration, the discontinuity in the circumferential direction of the throttle members 41, 42 is greater than in the first embodiment. Therefore, the effect of suppressing the increase in the backflow area is improved compared to the first embodiment.

5th Modification As shown in FIG. 11(e), the fifth modification is different from the first embodiment in that the flow rate control device 4 includes six throttle members 43-48. In the axial view, the throttle members 43-48 are plate-shaped with an isosceles trapezoid shape. In the circumferential direction, the throttle members 43-48 are evenly arranged at 60° intervals. The ends 43a-48a corresponding to the upper bases of the throttle members 43-48 are oriented radially inward and arranged to form a regular hexagon. In this configuration, the throttle members 43-48 protrude over substantially the entire circumference of the inner surface side of the suction pipe 35 in the circumferential direction. Therefore, when the throttle members 43-48 protrude, it is difficult for the axial flow to flow into the tip of the inducer vane 34b. Therefore, the throttle members 43-48 are configured not to abut against each other even when they protrude into the suction pipe 35 in the circumferential direction. In the fifth modified example, a slit-shaped gap S3 is formed between each of the adjacent throttle members 43 to 48 in the radial direction of the suction pipe 35 when viewed in the axial direction. When the axial flow passes through this gap S3, a part of the axial flow flows into the tip of the inducer vane 34b. The gap S3 functions in the same manner as the through hole 41b in the second embodiment. That is, when the flow rate decreases, a swirling flow that has become an axial flow due to the gap S3 flows into the tip of the inducer vane 34b located downstream of the gap S3. As a result, the axial flow is made uniform downstream of the throttle position P.

In addition, when backflow of the handled fluid occurs, the throttling members 43-48 can suppress the increase in the backflow area in the same way as conventional annular members, depending on the flow rate. At this time, the gap S3 also attenuates the swirling component of the handled fluid that is flowing back. Then, part of the backflow area is drawn into the axial flow that passes through the gap S3. As a result, the increase in the backflow area upstream of the throttling members 43-48 is further suppressed.

In the fifth modified example, the shape of the aperture members 43 to 48 is not limited to an isosceles trapezoid. Furthermore, the gap S3 does not have to be formed along the radial direction, and may be formed in a curved shape.

Furthermore, in the fifth variant, the size of each gap S3 may be the same or different.

Furthermore, in the fifth modified example, the shape of the gap S3 is not limited to a slit shape. That is, for example, the length (width) of the gap S3 in the circumferential direction may be set to be approximately the same as that of the aperture members 43 to 48.

Sixth Modification As shown in FIG. 11(f), the sixth modification is different from the fifth modification in that the diaphragm members 43-48 have notches 43b-48b. The center of each of the ends 43a-48a of the diaphragm members 43-48 is notched outward in the radial direction to form slit-shaped notches 43b-48b. That is, each of the diaphragm members 43-48 has notches 43b-48b. The notches 43b-48b function in the same way as the gap S3 in the fifth modification. In the circumferential direction, the diaphragm members 43-48 are configured to protrude so as to close the gap (not shown; the same applies below) formed between the adjacent diaphragm members 43-48, and ultimately come into contact with the adjacent diaphragm members 43-48. Therefore, the axial flow and the swirl flow pass through the gaps and the notches 43b to 48b until the throttle members 43 to 48 protrude to their maximum extent, and then pass through the notches 43b to 48b when the throttle members 43 to 48 protrude to their maximum extent. Therefore, the axial flow is more uniform downstream of the throttle position P than in the fifth modified example.

In addition, in the sixth modified example, the positions of the notches 43b to 48b are not limited to the centers of the ends 43a to 48a.

In addition, in the sixth modified example, the number of notches 43b to 48b provided on each of the aperture members 43 to 48 is not limited to "1".

Seventh Modification FIG. 13 is a schematic piping diagram of a seventh modification of the flow rate control device 4. As shown in FIG.

In the seventh modified example, the pump system S includes a flow meter FL attached to the discharge flow path L2. The flow meter FL measures the flow rate of the handled fluid flowing through the discharge flow path L2, generates discharge flow rate information indicating the measured flow rate, and transmits it to the control device 60. The flow velocity control device 4 changes the protrusion amount of the throttling members 41, 42 based on the discharge flow rate information transmitted from the flow meter FL (measured by the flow meter FL). The discharge flow rate information is an example of flow rate information in the present invention. Even with this configuration, the flow velocity control device 4 can control the axial flow velocity according to the flow rate, as in the first embodiment.

●Other embodiments●
In the present invention, as shown in each modified example, the configuration (number, shape, arrangement, etc.) of the diaphragm members 41, 42 is not limited to this embodiment.

In addition, in the present invention, the control information may be generated by an external device other than the external device O (e.g., a central control panel of the facility) and transmitted to the discharge valve V2 and the control device 60.

Furthermore, in the present invention, the configuration (number, shape, arrangement, etc.) of the storage chambers 35a, 35b and the slits 35c, 35d may be appropriately changed according to the configuration of the throttling members 41, 42. That is, for example, in the first modified example, the centrifugal pump 1 may have only one storage chamber 35a. Also, in the fifth modified example, the centrifugal pump 1 may have storage chambers (not shown) that house each of the throttling members 43 to 48, or may have one ring-shaped storage chamber (not shown).

Furthermore, in the present invention, the shape of the aperture members 41, 42 is not limited to a rectangle. That is, for example, the shape of the aperture members 41, 42 may be a semicircle or a triangle.

Furthermore, in the present invention, the arrangement of the throttling members 41, 42 does not have to be uniformly arranged at equal angular intervals in the circumferential direction. That is, for example, the angle between the throttling members 41, 42 in the circumferential direction may be 120° (240°).

Furthermore, in the present invention, the shape of the aperture member 41 may be different from the shape of the aperture member 42. That is, for example, when viewed in the axial direction, the length of the end 41a may be smaller than the length of the end 42a.

Furthermore, in the present invention, the shape of the ends 41a, 42a is not limited to a straight line. That is, for example, when viewed in the axial direction, the shape of the ends 41a, 42a may be an arc that follows the inner surface of the suction pipe 35.

Furthermore, in the present invention, the flow rate at which the throttling members 41, 42 start to protrude is not limited to the first flow rate. That is, for example, the throttling members 41, 42 may protrude from a flow rate between the maximum efficiency point and the first flow rate.

Furthermore, in the present invention, the flow rate at which the throttle members 41, 42 protrude by the maximum amount may be a flow rate greater than the second flow rate.

Furthermore, in the present invention, the relationship of the opening ratio to the flow rate is not limited to the relationship shown in Figure 7, as long as the inlet angle is kept at the optimal angle.

Furthermore, the configurations of the first embodiment and each of the modified examples may be combined with each other.

●Embodiments of the present invention●
Next, the embodiments of the present invention that can be understood from the above-described embodiments will be described below, using the terms and symbols described in the respective embodiments.

A first embodiment of the present invention is a flow rate control device (e.g., flow rate control device 4) that controls the axial flow rate of handled liquid flowing in a suction pipe (e.g., suction pipe 35) of a centrifugal pump (e.g., centrifugal pump 1) equipped with an inducer (e.g., inducer 34), and includes a throttling mechanism (e.g., throttling mechanism 40) arranged upstream of the flow of the handled liquid from the inducer in the suction pipe, and the throttling mechanism includes at least one throttling member (e.g., throttling members 41, 42) that protrudes from the inner surface of the suction pipe into the suction pipe along the transverse direction of the suction pipe, thereby changing the axial flow rate of the handled liquid flowing into the inducer, upstream of the inducer, and the protrusion amount of the throttling member from the inner surface into the suction pipe is variably controlled based on flow rate information related to the flow rate of the handled liquid discharged from the centrifugal pump.
According to this configuration, the optimum inlet angle relative to the inlet angle is maintained even if the flow rate decreases, and the operating flow rate range of the centrifugal pump equipped with an inducer is expanded toward the small flow rate region.

A second embodiment of the present invention is a flow velocity control device according to the first embodiment, wherein the protrusion amount is controlled to increase as the flow rate decreases.
With this configuration, the cross-sectional area at the throttle location decreases as the flow rate decreases, and the axial flow velocity at the throttle location remains constant.

A third embodiment of the present invention is a flow rate control device according to the first or second embodiment, wherein a flow measuring device (e.g., a flow meter FL) that measures the flow rate of the handled liquid flowing through the discharge flow path (e.g., discharge flow path L2) through which the handled liquid discharged from the centrifugal pump flows is attached, and the flow rate information is discharge flow rate information that indicates the flow rate measured by the flow measuring device.
According to this configuration, the flow velocity control device can control the axial flow velocity in conjunction with the flow rate control for the discharge valve.

A fourth embodiment of the present invention is a flow rate control device according to the first or second embodiment, in which a flow rate adjustment device (e.g., a discharge valve V2) is attached to a discharge flow path through which the handled liquid discharged from the centrifugal pump flows, and the flow rate information is flow rate control information that controls the operation of the flow rate adjustment device.
According to this configuration, the flow velocity control device can control the axial flow velocity while suppressing a decrease in suction performance.

A fifth embodiment of the present invention is a flow rate control device in any one of the first to fourth embodiments, wherein the throttling mechanism has a plurality of the throttling members arranged at equal angular intervals around the suction pipe.
According to this configuration, not only the protruding regions but also the non-protruding regions can be easily formed.

A sixth embodiment of the present invention is the flow rate control device according to the fifth embodiment, wherein the throttle mechanism includes two of the throttle members arranged to face each other.
According to this configuration, the flow velocity control device 4 can form a wide non-protruding region while suppressing the amount of protrusion required to reduce the cross-sectional area.

A seventh embodiment of the present invention is a flow rate control device in which, in the fifth embodiment, when each of the multiple throttling members protrudes into the suction pipe, adjacent throttling members in the circumferential direction do not come into contact with each other.
According to this configuration, a non-protruding region is reliably formed between adjacent throttle members in the circumferential direction.

An eighth embodiment of the present invention is a flow rate control device in which, in the seventh embodiment, a slit-shaped gap is formed between two adjacent throttling members (e.g., throttling members 43 to 48) in the circumferential direction.
According to this configuration, the axial flow is made uniform downstream of the throttling position.

A ninth embodiment of the present invention is a flow rate control device in any one of the first to eighth embodiments, wherein the throttling member is arranged in a portion protruding into the suction pipe and is provided with a through hole (e.g., through holes 41b to 42d) along the axial direction of the suction pipe, or a notch (e.g., notch 43b to 48b) cut into an end portion (e.g., end portion 43a to 48a) of the throttling member on the protruding direction side.
According to this configuration, the axial flow is made uniform downstream of the throttling position.

A tenth embodiment of the present invention is a centrifugal pump comprising a rotating shaft (e.g., rotating shaft 23), an impeller attached to one end (e.g., front end 23a) of the rotating shaft, a suction pipe for introducing handled liquid to be sucked into the impeller, an inducer disposed in the suction pipe, and a flow rate control device described in the first embodiment that is attached to the suction pipe and controls the axial flow rate of the handled liquid flowing through the suction pipe.
According to this configuration, the optimum inlet angle relative to the inlet angle is maintained even if the flow rate decreases, and the operating flow rate range of the centrifugal pump equipped with an inducer is expanded toward the small flow rate region.

1 Centrifugal pump 32 Impeller 34 Inducer 35 Suction pipe 4 Flow rate control device 40 Throttle mechanism 41 Throttle member 42 Throttle members 43 to 48 Throttle members 43a to 48a Ends 43b to 48b Notch L2 Discharge flow path FL Flow meter (flow measuring device)
V2 Discharge valve (flow rate control device)

In one embodiment of the present invention, a flow rate control device is a flow rate control device that controls the axial flow rate of handled liquid flowing through a suction pipe of a centrifugal pump equipped with an inducer, and includes a throttling mechanism arranged upstream of the inducer in the flow of the handled liquid in the suction pipe, and the throttling mechanism includes at least one throttling member that protrudes from the inner surface of the suction pipe into the suction pipe along the transverse direction of the suction pipe, thereby changing the axial flow rate of the handled liquid flowing into the inducer upstream of the inducer, and the amount of protrusion of the throttling member from the inner surface into the suction pipe is variably controlled based on flow rate information related to the flow rate of the handled liquid discharged from the centrifugal pump , and when the throttling member is located at the outermost position in the radial direction of the suction pipe, the throttling member does not protrude into the suction pipe, and when the throttling member protrudes into the suction pipe, only the throttling member of the throttling mechanism protrudes into the suction pipe .

A flow rate control device in one embodiment of the present invention is a flow rate control device that controls the axial flow rate of a handled liquid flowing in a suction pipe of a centrifugal pump equipped with an inducer, and includes a throttling mechanism that is arranged upstream of the inducer in the flow of the handled liquid in the suction pipe, and the throttling mechanism includes a plurality of throttling members arranged at equal angular intervals in the circumferential direction of the suction pipe, which protrude from the inner surface side of the suction pipe into the suction pipe along a transverse direction of the suction pipe, thereby changing the axial flow rate of the handled liquid flowing into the inducer upstream of the inducer. The amount of protrusion of the throttling member from the inner surface into the suction pipe is variably controlled based on flow rate information related to the flow rate of the handled fluid discharged from the centrifugal pump, and when the throttling member is located at the outermost side in the radial direction of the suction pipe, the throttling mechanism does not protrude from the inner surface into the suction pipe, and when the throttling member protrudes into the suction pipe, only the throttling member of the throttling mechanism protrudes from the inner surface into the suction pipe, and when each of the multiple throttling members protrudes into the suction pipe, adjacent throttling members in the circumferential direction do not come into contact with each other .

Claims (10)

A flow rate control device for controlling the axial flow rate of a handled liquid flowing through a suction pipe of a centrifugal pump equipped with an inducer,
a throttle mechanism disposed in the suction pipe upstream of the inducer in a flow of the handled fluid,
the throttling mechanism includes at least one throttling member that protrudes from an inner surface side of the suction pipe into the suction pipe along a transverse direction of the suction pipe to change the axial flow velocity of the handled fluid flowing into the inducer upstream of the inducer,
A protrusion amount from the inner surface of the throttle member into the suction pipe is variably controlled based on flow rate information related to a flow rate of the pumped fluid discharged from the centrifugal pump.
Flow rate control device. The protrusion amount is controlled to increase as the flow rate decreases.
The flow control device according to claim 1 . A flow rate measuring device is attached to a discharge flow path through which the handled liquid discharged from the centrifugal pump flows, the flow rate measuring device measuring the flow rate of the handled liquid flowing through the discharge flow path,
The flow rate information is discharge flow rate information indicating the flow rate measured by the flow rate measuring device.
The flow control device according to claim 1 . A flow rate adjusting device is attached to a discharge flow path through which the handled fluid discharged from the centrifugal pump flows, the flow rate adjusting device adjusting the flow rate of the handled fluid flowing in the discharge flow path,
The flow rate information is flow rate control information for controlling the operation of the flow rate regulator.
The flow control device according to claim 1 . The throttling mechanism includes a plurality of the throttling members arranged at equal angular intervals in the circumferential direction of the suction pipe.
The flow rate control device according to any one of claims 1 to 4. The throttling mechanism includes two throttling members arranged to face each other.
The flow control device according to claim 5 . When each of the plurality of throttle members protrudes into the suction pipe, the throttle members adjacent to each other in the circumferential direction do not come into contact with each other.
The flow control device according to claim 5 . A slit-shaped gap is formed between two adjacent throttle members in the circumferential direction.
The flow control device according to claim 7. The throttle member is disposed in a portion protruding into the suction pipe, and has a through hole along the axial direction of the suction pipe, or a notch cut into an end portion of the throttle member on the protruding direction side.
The flow control device according to claim 5 . A rotation axis;
an impeller attached to one end of the rotating shaft;
a suction pipe for introducing a handled liquid to be sucked into the impeller;
an inducer disposed within the suction pipe;
a flow rate control device according to claim 1, which is attached to the suction pipe and controls an axial flow rate of the handled fluid flowing through the suction pipe;
Is there,
Centrifugal pump.

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