CN114542483A

CN114542483A - Calibration device for flow coefficient of balance hole of centrifugal pump impeller

Info

Publication number: CN114542483A
Application number: CN202210208046.7A
Authority: CN
Inventors: 曾继来; 刘在伦; 张森; 顾生富; 吕佩涛
Original assignee: Lanzhou University of Technology
Current assignee: Lanzhou University of Technology
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2022-05-27

Abstract

A calibration device for flow coefficient of a balance hole of an impeller of a centrifugal pump is a pressure testing unit consisting of a 1# pressure measuring hole 9, a 1# pressure measuring cavity 8, a 1# pressure measuring conduit 16, a 1# screw joint 17, a 1# pressure hose 19, a 1# ball valve 21, a 2# pressure measuring hole 12, a 2# pressure measuring cavity 11, a 2# pressure measuring conduit 31, a 2# screw joint 18, a 2# pressure hose 20, a 2# ball valve 25, a pressure stabilizing tank 24, an exhaust valve 22 and a positive and negative pressure gauge 23, and realizes accurate measurement of inlet and outlet pressures of the balance hole 36 when the impeller 3 and the balance hole 36 rotate at high speed. The leakage rate test unit consisting of the drainage cavity 13, the water conduit 47, the backflow cavity 27, the electromagnetic flowmeter 29, the balance cavity 14 and the balance hole 36 is closed-loop, and can measure the leakage rate of the pump in operation under any working condition and cavitation state. The device has the advantages of simple structure and practical function, and can realize the measurement of the leakage amount of the balance hole 36 and the calibration of the flow coefficient of the balance hole 36 without repeatedly disassembling a testing device, so the operation is extremely convenient, and the time and the labor are saved.

Description

Calibration device for flow coefficient of balance hole of centrifugal pump impeller

Technical Field

The invention belongs to the technical field of pump detection, and particularly relates to a calibration device for a flow coefficient of a balance hole of an impeller of a centrifugal pump.

Background

In centrifugal pump design, a sealing ring is usually attached to an impeller, and a plurality of balancing holes are formed in the impeller to balance axial force. When the centrifugal pump works, a part of high-pressure liquid at the outlet of the impeller flows back to the inlet of the impeller through the rear pump cavity, the rear sealing ring gap, the balance cavity and the balance hole in sequence, and the leakage rate of the side cavity of the rear cover plate of the impeller is formed. According to a fluid mechanics continuity equation, the leakage quantity of the side cavity of the impeller back cover plate is equal to the leakage quantity of the balance hole. The method is characterized in that the leakage rate of the balance hole is accurately calculated according to the flow coefficient of the balance hole, and the method is a prerequisite condition for predicting the axial force, researching the influence mechanism of the high-speed jet of the balance hole on the cavitation performance of the pump, reducing the volume loss of the pump, saving energy and reducing emission. Therefore, the balance hole flow coefficient is calibrated by a test method, and the method has very important engineering application value. The flow coefficient of the balance hole is calibrated, and the leakage rate of the balance hole and the pressure of an inlet and an outlet of the balance hole are accurately measured. However, since the impeller rotates at high speed with the pump shaft, it is extremely difficult to directly measure the leakage amount of the balance hole and the inlet-outlet pressure thereof.

Through retrieval, documents on calibrating the balance hole flow coefficient include:

agricultural engineering reports test and analysis of liquid leakage rate of balance hole of centrifugal pump (volume 33 of 2017, period 7), and provides a method for indirectly measuring leakage rate of balance hole based on that the leakage rate of clearance of back sealing ring is equal to that of balance hole, and calibrates flow coefficient of balance hole with different lift coefficient. The method specifically comprises the following steps: and (3) arranging a liquid leakage hole on a blank cap of the balance cavity, firstly closing the liquid leakage hole, opening the balance hole, allowing liquid in the balance cavity to flow into an inlet of the impeller through the balance hole, and measuring the pressure of a gap inlet of the sealing ring and the balance cavity. Then block up the balancing hole, open liquid and let out the hole and cause balanced chamber liquid to the external world, let out the aperture of gate valve on the pipeline through adjusting liquid repeatedly and let out hole and pump outlet pipe, the pressure when making back seal ring clearance inlet pressure and balanced chamber and balancing hole open is equal, and the flow that the hole was let out to liquid this moment is the leakage quantity of balancing hole promptly. The method basically realizes indirect measurement of leakage amount of the balance hole, but has the disadvantages that: the liquid in the balance cavity is led to the outside, the pressure at the outlet of the liquid leakage hole is atmospheric pressure, and the inlet of the impeller is negative pressure in a cavitation state, so that the method cannot measure the leakage amount of the balance hole when the pump is cavitated.

The university of science and technology in Huazhong (Nature science edition) the calculation and experimental study of the leakage rate and pressure of the balance cavity of the centrifugal pump, the testing device of the leakage rate is improved, and the flow coefficient of the balance hole is calibrated according to the test result when the specific area is different. The balance cavity is communicated with the pump inlet pipeline through the water return pipeline, when the balance hole is blocked, liquid in the balance cavity flows back to the pump inlet, and closed-loop measurement of leakage amount is preliminarily achieved. Because the testing device is closed, the indirect measurement of the leakage amount of the balance hole in the cavitation state can be realized. The device has the following disadvantages: the liquid of the balance cavity is led to the inlet of the pump, the flow state of the inlet of the impeller is greatly changed under the two states of opening and blocking the balance hole, the external characteristic and the cavitation performance of the pump are directly changed, and therefore the error of the test result of the leakage rate in the cavitation state of the pump is large.

The test devices in both of the above documents have the following disadvantages: on one hand, when the leakage rate of the balance hole is measured, the balance hole is required to be opened to measure pressure, and then the balance hole is blocked to measure pressure, so that the test steps are complicated, a test device needs to be disassembled for many times, and time and labor are wasted; on the other hand, when the flow coefficient of the balance hole is calibrated, the pressure of the balance cavity and the pressure of the inlet of the pump are respectively adopted to replace the pressure of the inlet and the outlet of the balance hole. When the centrifugal pump operates, the pressure in the balance cavity is not uniformly distributed, and the pressure at the inlet of the pump is greatly different from the pressure at the outlet of the balance hole, so that the flow coefficient of the balance hole cannot be accurately calibrated.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a calibration device for the flow coefficient of a balance hole of a centrifugal pump impeller, which mainly comprises a stator component, a rotor component, a pressure testing unit and a leakage testing unit. The stator component consists of a pump body, a rear pump cover, a front sealing ring, a rear sealing ring, a penetrating cylinder, a No. 2 framework seal and a No. 3 framework seal; the rotor part consists of a pump shaft, an impeller, a balance hole disc, a balance hole, a No. 1 framework seal, a key and a round nut; the pressure testing unit consists of a 1# pressure tapping hole, a 1# pressure testing cavity, a 1# pressure testing conduit, a 1# screw joint, a 1# pressure hose, a 1# ball valve, a 2# pressure tapping hole, a 2# pressure testing cavity, a 2# pressure testing conduit, a 2# screw joint, a 2# pressure hose, a 2# ball valve, a pressure stabilizing tank, an exhaust valve and a positive and negative pressure gauge; the leakage testing unit consists of a drainage cavity, a water conduit, a reflux cavity, an electromagnetic flowmeter and a balance cavity.

In the stator component, the rear pump cover consists of a left large circular ring and a right cylinder, and is fixed on the right side of the pump body through A groups of bolts. The front sealing ring is arranged on the inner side of the pump body in an interference fit mode, the rear sealing ring is arranged at the left end of the cylinder on the right side of the rear pump cover in an interference fit mode, and the left end face of the rear sealing ring is flush with the left end face of the large ring of the rear pump cover. The penetrating cylinder is fixedly connected to the right side of the rear pump cover through the B group bolt and nut assembly, a certain gap is reserved between the left side end face of the penetrating cylinder and the right side wall face of the rear cover plate of the impeller, two stages of inner steps are axially processed from left to right on the inner side of the penetrating cylinder from the left side end face of the penetrating cylinder, and the inner step faces are perpendicular to the central axis. The 2# skeleton seal is installed on the inner wall of the transparent cylinder on the right side of the step surface in the first stage of the transparent cylinder through the seam allowance, and the left end face of the 2# skeleton seal is flush with the step surface in the first stage of the transparent cylinder. The 3# framework seal is installed on the inner wall of the transparent cylinder on the right side of the step surface in the second stage of the transparent cylinder through the seam allowance in a positioning mode, and the left end face of the 3# framework seal is flush with the step surface in the second stage of the transparent cylinder.

In the rotor component, the impeller is fixedly arranged on the pump shaft through a key. The impeller preformed hole is formed in the position, with the smaller radius, of the impeller rear cover plate, in order to reduce interference of the impeller preformed hole on the outlet liquid flow state of the balance hole, the diameter of the impeller preformed hole is as large as possible, and the impeller preformed hole is accurate enough to contain the balance hole and the left end face of the 1# pressure taking hole and prevent damage to the strength of an impeller hub. The balance hole disc is positioned and installed on the pump shaft and the key through the rabbets on the impeller hub. Two stages of outer steps are processed on the outer side of the balance hole disc from the right end face of the balance hole disc to the left in the axial direction, and the outer step faces are perpendicular to the central axis. The outer surface of the left side of the balance hole disc is matched with the sealing lip of the 2# framework seal, the outer surface of the right side of the balance hole disc is matched with the sealing lip of the 3# framework seal, and a gap is reserved between the first-stage step surface of the right side of the balance hole disc and the left end of the 3# framework seal. The impeller and the balance hole disc are axially fixed on the pump shaft through a round nut. The balance hole is horizontally arranged on the balance hole disc along the axial direction. The 1# framework seal is arranged on the inner side of the impeller seal ring, the left end face of the 1# framework seal is attached to the impeller rear cover plate, and the seal lip of the 1# framework seal is matched with the outer surface of the left side of the penetrating cylinder.

In the pressure test unit, the 1# pressure taking hole is a reverse L-shaped hole vertically arranged at the left part of the balance hole disc along the radial direction and the axial direction, and the outlet pressure of the balance hole can be transmitted into the 1# pressure measuring cavity. The number of 1# pressure taking holes is equal to that of the balance holes. The impeller rear cover plate, the balance hole disc, the No. 2 framework seal, the first-stage step surface of the penetrating cylinder, the inner wall of the penetrating cylinder and the No. 1 framework seal form a No. 1 pressure measuring cavity. The 1# pressure measurement pipe is opened on penetrating the section of thick bamboo, and the left end and the 1# pressure measurement chamber UNICOM of 1# pressure measurement pipe, the right-hand member of 1# pressure measurement pipe are through 1# to the silk joint and 1# pressure hose left end UNICOM. The right end of the No. 1 pressure hose is communicated with the surge tank through a No. 1 ball valve. The 2# pressure taking holes are short holes vertically arranged on the right part of the balance hole disc along the radial direction, the pressure of the inlet of each balance hole can be transmitted to the 2# pressure measuring cavity, and the number of the 2# pressure taking holes is equal to that of the balance holes. The outer surface of the balance hole disc, the second-stage outer step surface of the balance hole disc, the 3# framework seal, the second-stage step surface of the transparent cylinder, the inner wall of the transparent cylinder and the 2# framework seal enclose a 2# pressure measuring cavity. The 2# pressure measurement pipe is horizontally opened on the penetrating cylinder along the axial direction, the left end of the 2# pressure measurement pipe is communicated with the 2# pressure measurement cavity, and the right end of the 2# pressure measurement pipe is communicated with the left end of the 2# pressure hose through the 2# wire-aligning joint. The right end of the No. 2 pressure hose is communicated with the surge tank through a No. 2 ball valve. An exhaust valve is arranged at the upper end of the pressure stabilizing tank, and a positive pressure gauge and a negative pressure gauge are arranged on the right side of the pressure stabilizing tank.

In the leakage testing unit, a drainage cavity is enclosed by the outer surface of the through cylinder, the left side surface of the through cylinder flange, the inner wall surface of the cylinder on the right side of the rear pump cover, the right side end surface of the rear sealing ring, the impeller sealing ring and the No. 1 framework. The two water guide pipes are symmetrically and fixedly arranged on two sides of the cylinder on the right side of the rear pump cover along the radial direction, and the symmetrical central axes of the two water guide pipes are equal to the central line of the pump shaft in height. The flange on the left side of the water conduit is butted with the flanges on the two sides of the cylinder on the right side of the rear pump cover and fixedly connected together by an E group bolt and nut assembly. The flange on the right side of the water conduit is butted with the flanges on the two sides of the reflux cavity and fixedly connected together by F groups of bolt and nut assemblies. And a flange on the left side of the backflow cavity is butted with a flange on the right side of the electromagnetic flowmeter and fixedly connected together by a D group bolt and nut assembly. The left flange of the electromagnetic flowmeter is butted with the right flange of the transparent cylinder and fixedly connected together by a C group bolt and nut assembly. The inner wall surface of the penetrating cylinder, the 3# framework seal, the balance hole disc, the round nut and the right end surface of the pump shaft are enclosed to form a balance cavity, and the balance cavity is communicated with the impeller inlet through the balance hole.

Compared with the prior art, the invention has obvious beneficial effects.

1. After the leakage liquid flows out from the gap of the rear sealing ring, the leakage liquid flows back to the impeller inlet from the balance hole through the leakage testing unit, and the actual flow direction of the leakage liquid in the centrifugal pump is completely the same as that of the leakage liquid in the centrifugal pump. Therefore, the method and the device for measuring the leakage rate of the balance hole are based on the condition that the flow state of the inlet of the impeller is not influenced, the testing device does not influence the external characteristics and the cavitation performance of the pump, the reliability of the testing result is high, and the leakage rate of the pump in the operation under any flow working condition and cavitation state can be measured.

2. The pressure test unit can realize accurate measurement of the pressure at the inlet and the outlet of the balance hole when the impeller and the balance hole rotate at high speed, and provides technical support for accurately calibrating the flow coefficient of the balance hole.

3. The balance hole leakage measuring device is simple and practical in structure, can measure the leakage amount of the balance hole and calibrate the flow coefficient of the balance hole without repeatedly disassembling a testing device, is extremely convenient to operate, and is time-saving and labor-saving.

Drawings

FIG. 1 is a schematic diagram of the structure and function of the present invention.

Figure 2 is a top view of the test apparatus of figure 1.

In the figure: 1. the novel pressure measuring device comprises a front sealing ring 2, an impeller preformed hole 3, an impeller 4, an impeller rear cover plate 5, a rear pump cavity 6, a rear pump cover 7, an A group bolt 8.1 # pressure measuring cavity 9.1 # pressure measuring hole 10, a balance hole disk 11.2 # pressure measuring cavity 12.2 # pressure measuring hole 13, a drainage cavity 14, a balance cavity 15, a drainage cavity outlet 16.1 # pressure measuring pipe 17.1 # pressure measuring pipe 17.2 # screw joint 18.2 # screw joint 19.1 # pressure hose 20.2 # pressure hose 21.1 # ball valve 22, an exhaust valve 23, a positive and negative pressure gauge 24, a pressure stabilizing tank 25.2 # ball valve 26, a return cavity inlet 27, a D group bolt nut component 29, an electromagnetic flow meter 30, a C group bolt nut component 31.2 # pressure measuring pipe 32, a transmission cylinder 33, a B group bolt nut component 34, a round nut 35.3 # framework sealing 36, a balance hole 37, a key 38 and a rear sealing ring gap 39. Rear seal ring 40.2 # skeleton seal 41, impeller seal ring 42.1 # skeleton seal 43, pump body 44, pump shaft 45, E group bolt and nut assembly 46, F group bolt and nut assembly 47, water conduit.

Detailed Description

Hereinafter, embodiments of the present invention will be further described with reference to the drawings.

As shown in fig. 1 and fig. 2, a calibration apparatus for flow coefficient of a balance hole of an impeller of a centrifugal pump mainly includes a stator component, a rotor component, a pressure testing unit and a leakage testing unit, wherein: the stator component consists of a pump body 43, a rear pump cover 6, a front sealing ring 1, a rear sealing ring 39, a transparent cylinder 32, a No. 2 framework seal 40 and a No. 3 framework seal 35; the rotor part consists of a pump shaft 44, an impeller 3, a balance hole disc 10, a balance hole 36, a No. 1 framework seal 42, a key 37 and a round nut 34; the pressure testing unit consists of a 1# pressure measuring hole 9, a 1# pressure measuring cavity 8, a 1# pressure measuring conduit 16, a 1# screw joint 17, a 1# pressure hose 19, a 1# ball valve 21, a 2# pressure measuring hole 12, a 2# pressure measuring cavity 11, a 2# pressure measuring conduit 31, a 2# screw joint 18, a 2# pressure hose 20, a 2# ball valve 25, a pressure stabilizing tank 24, an exhaust valve 22 and a positive and negative pressure gauge 23; the leakage quantity testing unit consists of a drainage cavity 13, a water conduit 47, a backflow cavity 27, an electromagnetic flowmeter 29 and a balance cavity 14.

As shown in fig. 1 and 2, the rear pump cover 6 of the stator part is composed of a left large circular ring and a right cylinder, and the rear pump cover 6 is fixed on the right side of the pump body 43 through a group a of bolts 7. The front sealing ring 1 is arranged on the inner side of the pump body 43 in an interference fit manner, the rear sealing ring 39 is arranged on the left end of the right cylinder of the rear pump cover 6 in an interference fit manner, and the left end surface of the rear sealing ring 39 is flush with the left end surface of the large ring of the rear pump cover 6. The transmission cylinder 32 is fixedly connected to the right side of the rear pump cover 6 through a group B bolt-nut assembly 33, a certain gap is reserved between the left side end face of the transmission cylinder 32 and the right side wall face of the impeller rear cover plate 4, two stages of inner steps are axially processed from left to right on the inner side of the transmission cylinder 32 from the left side end face of the transmission cylinder 32, and the inner step faces are perpendicular to the central axis. The 2# skeleton seal 40 is positioned and installed on the inner wall of the penetrating tube 32 on the right side of the first-stage inner step surface of the penetrating tube 32 through the seam allowance, and the left end surface of the 2# skeleton seal 40 is flush with the first-stage inner step surface of the penetrating tube 32. The 3# skeleton seal 35 is installed on the inner wall of the penetrating tube 32 on the right side of the second-stage step surface of the penetrating tube 32 through the spigot in a positioning manner, and the left end surface of the 3# skeleton seal 35 is flush with the second-stage step surface of the penetrating tube 32.

As shown in fig. 1, the impeller 3 in the rotor component is fixedly mounted on the pump shaft 44 through the key 37, and when the impeller 3 is mounted, a sealant is applied to a contact surface between the impeller 3 and the shaft shoulder. The impeller preformed hole 2 is formed in the position, with the smaller radius, of the impeller rear cover plate 4, in order to reduce interference of the impeller preformed hole 2 on the flow state of liquid at the outlet of the balance hole 36, the diameter of the impeller preformed hole 2 needs to be as large as possible, and the impeller rear cover plate is accurate to the extent that the balance hole 36 and the left side end face of the 1# pressure taking hole 9 are included and the strength of a hub of the impeller 3 cannot be damaged. The balance hole disc 10 is positioned and installed on the pump shaft 44 and the key 37 through a seam allowance on the hub of the impeller 3, and when the balance hole disc 10 is installed, sealant is coated on the contact surface of the balance hole disc 10 and the impeller rear cover plate 4. Two stages of outer steps are machined on the outer side of the balance hole disc 10 from the right end face to the left end face of the right side of the balance hole disc 10 along the axial direction, and the outer step faces are perpendicular to the central axis. The outer surface of the left side of the balance hole disc 10 is matched with the sealing lip of the No. 2 framework seal 40, the outer surface of the right side of the balance hole disc 10 is matched with the sealing lip of the No. 3 framework seal 35, and a gap is reserved between the first-stage step surface on the right side of the balance hole disc 10 and the left end of the No. 3 framework seal 35. The impeller 3 and the balance hole disk 10 are axially fixed on the pump shaft 44 by a round nut 34. The balance hole 36 is horizontally opened on the balance hole disk 10 along the axial direction. The No. 1 framework seal 42 is arranged on the inner side of the impeller seal ring 41, the left end face of the No. 1 framework seal 42 is attached to the impeller rear cover plate 4, and the seal lip of the No. 1 framework seal 42 is matched with the left outer surface of the penetrating cylinder 32.

As shown in FIG. 1, the No. 1 pressure measuring hole 9 in the pressure test unit is a reverse L-shaped hole vertically arranged on the left part of the balance hole disc 10 along the radial direction and the axial direction, and can transmit the pressure at the outlet of the balance hole 36 to the No. 1 pressure measuring cavity 8. The number of 1# pressure taking holes 9 is equal to the number of balance holes 36. The impeller rear cover plate 4, the balance hole disc 10, the 2# skeleton seal 40, the first-stage step surface of the transparent cylinder 32, the inner wall of the transparent cylinder 32 and the 1# skeleton seal 42 enclose a 1# pressure measuring cavity 8. The 1# pressure measuring catheter 16 is arranged on the penetrating cylinder 32, the left end of the 1# pressure measuring catheter 16 is communicated with the 1# pressure measuring cavity 8, and the right end of the 1# pressure measuring catheter 16 is communicated with the left end of the 1# pressure hose 19 through the 1# wire-to-wire connector 17. The right end of the No. 1 pressure hose 19 is communicated with a pressure stabilizing tank 24 through a No. 1 ball valve 21. The 2# pressure taking holes 12 are short holes vertically arranged on the right part of the balance hole disc 10 along the radial direction, the pressure of the inlet of the balance hole 36 can be transmitted to the 2# pressure measuring cavity 11, and the number of the 2# pressure taking holes 12 is equal to that of the balance holes 36. The outer surface of the balance hole disc 10, the second-stage outer step surface of the balance hole disc 10, the 3# framework seal 35, the second-stage step surface of the transparent cylinder 32, the inner wall of the transparent cylinder 32 and the 2# framework seal 40 enclose a 2# pressure measuring cavity 11. The 2# pressure measuring catheter 31 is axially and horizontally arranged on the penetrating cylinder 32, the left end of the 2# pressure measuring catheter 31 is communicated with the 2# pressure measuring cavity 11, and the right end of the 2# pressure measuring catheter 31 is communicated with the left end of the 2# pressure hose 20 through the 2# wire-to-wire connector 18. The right end of the No. 2 pressure hose 20 is communicated with a pressure stabilizing tank 24 through a No. 2 ball valve 25. An exhaust valve 22 is arranged at the upper end of the pressure stabilizing tank 24, and a positive and negative pressure gauge 23 is arranged at the right side of the pressure stabilizing tank 24. The surge tank 24 can eliminate the adverse effect of pressure pulsations on the pressure test results.

As shown in fig. 1 and 2, the drainage chamber 13 is enclosed by the outer surface of the through tube 32, the left surface of the flange of the through tube 32, the inner wall surface of the right cylinder of the rear pump cover 6, the right end surface of the rear sealing ring 39, the impeller sealing ring 41 and the # 1 skeleton sealing 42 in the leakage amount test unit. The two water conduits 47 are symmetrically and fixedly arranged at two sides of the right cylinder of the rear pump cover 6 along the radial direction, and the symmetrical central axes of the two water conduits 47 have the same height with the central line of the pump shaft 44. The flange on the left side of the water conduit 47 is butted with the flanges on the two sides of the cylinder on the right side of the rear pump cover 6 and fixedly connected together by an E group bolt and nut assembly 45. The flanges on the right side of the water conduit 47 are butted against the flanges on both sides of the return chamber 27 and are fixedly connected together by the F-group bolt-and-nut assembly 46. The left flange of the return cavity 27 is butted with the right flange of the electromagnetic flowmeter 29 and fixedly connected together by a D group bolt-nut assembly 28. The left flange of the electromagnetic flowmeter 29 is butted with the right flange of the transparent cylinder 32 and fixedly connected together by a C group bolt-nut assembly 30. The inner wall surface of the penetrating cylinder 32, the # 3 framework seal 35, the balance hole disc 10, the round nut 34 and the right end surface of the pump shaft 44 enclose a balance cavity 14, and the balance hole 36 communicates the balance cavity 14 with the inlet of the impeller 3.

The operation of the present invention will be described in detail with reference to the accompanying drawings.

The measurement of the inlet and outlet pressures of the balance hole 36 is realized by the following steps:

as shown in fig. 1, the centrifugal pump is started, after the pump operates stably, the 2# ball valve 25 is opened, the liquid at the inlet of the balance hole 36 flows into the surge tank 24 through the 2# pressure measuring hole 12, the 2# pressure measuring cavity 11, the 2# pressure measuring conduit 31, the 2# screw joint 18, the 2# pressure hose 20 and the 2# ball valve 25 in sequence, and the air in the surge tank 24 is exhausted by slowly opening the exhaust valve 22. After the air is exhausted, the exhaust valve 22 is closed, at the moment, the liquid in the whole pressure measuring pipeline does not flow any more, the liquid pressure in the pressure measuring pipeline is transmitted by static pressure, and the reading of a positive pressure gauge 23 and a negative pressure gauge 23 is obtained

I.e. the pressure at the inlet of the equalizing port 36. Then, the 2# ball valve 25 is closed, the 1# ball valve 21 is opened, the liquid pressure at the outlet of the balance hole 36 is transmitted to the pressure stabilizing tank 24 through the 1# pressure taking hole 9, the 1# pressure measuring cavity 8, the 1# pressure measuring conduit 16, the 1# screw joint 17, the 1# pressure hose 19 and the 1# ball valve 21 in sequence, and the reading of the positive and negative pressure gauges 23 is obtained

I.e. the pressure at the outlet of the equalizing orifice 36.

The measurement of the leakage of the balance hole 36 is realized by:

as shown in figures 1 and 2, after the centrifugal pump is started, a part of high-pressure liquid at the outlet of the impeller 3 sequentially passes through the rear pump cavity 5 and the rear sealing ring gap 38 to enter the drainage cavity 13, then enters the water conduit 47 from the outlet 15 of the drainage cavity and passes through the water conduitThe water conduit 47 flows into the return cavity 27 from the return cavity inlet 26, and the liquid flow direction changes in the return cavity 27 and flows out from the left outlet of the return cavity 27. The liquid flowing out from the return cavity 27 flows into the inlet of the impeller 3 through the electromagnetic flowmeter 29, the balance cavity 14 and the balance hole 36 in sequence, and the leakage quantity of the balance hole 36 is formed. At this time, the indication value of the electromagnetic flowmeter 29 is the leakage amount of the balance hole 36

The size of (2). Since the leakage test unit is a closed loop, the leakage liquid in the rear pump cavity 5 flows out from the rear sealing ring gap 38 and finally flows back to the inlet of the impeller 3 from the balance hole 36 through the leakage test unit, which is exactly the same as the leakage flow direction in the real centrifugal pump. Therefore, the leakage testing unit tests the leakage on the basis of the condition that the flow state of the inlet of the impeller 3 is not influenced, the testing device does not influence the external characteristics and the cavitation performance of the pump, the reliability of the testing result is high, and the leakage under any working condition of the pump and the leakage of the pump in the cavitation state can be measured.

The calibration of the flow coefficient of the balance hole 36 is realized by:

the leakage of the balance hole 36 is given in the scientific newspaper (Nature science edition) of Huazhong university of science and technology (calculation and experimental research on leakage and pressure of balance cavity of centrifugal pump)

The calculation formula of (2) is specifically:

in the formula:

to balance the orifice flow coefficient;

the total area of the flow cross section of the balance hole is;

is the density of the liquid.

The measured pressure at the inlet of the balance hole 36

Balancing the pressure at the outlet of the orifice 36

Balance hole 36 leakage

Substituting the above formula, and measuring the total area of the flow cross section of the balance hole 36

And density of liquid

The flow rate coefficient of the balance hole 36 under the predetermined condition can be reversely deduced by substitution.

If the flow coefficient of the balance hole 36 under the conditions of different shapes, different tapers and different length-diameter ratios needs to be calibrated, only the balance hole disc 10 in different forms needs to be machined, and the operation is very convenient.

Claims

1. The utility model provides a calibration arrangement of centrifugal pump impeller balance hole flow coefficient, mainly includes stator part, rotor part, pressure test unit and lets out leakage test unit, its characterized in that: the stator component consists of a pump body (43), a rear pump cover (6), a front sealing ring (1), a rear sealing ring (39), a transparent cylinder (32), a 2# framework seal (40) and a 3# framework seal (35); the rotor component consists of a pump shaft (44), an impeller (3), a balance hole disc (10), balance holes (36), a No. 1 framework seal (42), keys (37) and round nuts (34); the pressure testing unit consists of a 1# pressure tapping hole (9), a 1# pressure testing cavity (8), a 1# pressure testing conduit (16), a 1# screw joint (17), a 1# pressure hose (19), a 1# ball valve (21), a 2# pressure tapping hole (12), a 2# pressure testing cavity (11), a 2# pressure testing conduit (31), a 2# screw joint (18), a 2# pressure hose (20), a 2# ball valve (25), a pressure stabilizing tank (24), an exhaust valve (22) and a positive and negative pressure gauge (23); the leakage quantity testing unit consists of a drainage cavity (13), a water conduit (47), a backflow cavity (27), an electromagnetic flowmeter (29) and a balance cavity (14).

2. The calibration device for the flow coefficient of the balance hole of the centrifugal pump impeller according to claim 1, wherein: in the stator component, a transmission cylinder (32) is fixedly connected to the right side of a rear pump cover (6) through a B group bolt and nut component (33), a certain gap is reserved between the left side end surface of the transmission cylinder (32) and the right side wall surface of an impeller rear cover plate (4), two stages of inner steps are machined from left to right in the axial direction on the inner side of the transmission cylinder (32) from the left end surface to the right end surface of the transmission cylinder (32), and the inner step surfaces are perpendicular to the central axis; the 2# framework seal (40) is positioned and installed on the inner wall of the penetrating tube (32) on the right side of the first-stage inner step surface of the penetrating tube (32) through a spigot, and the left end surface of the 2# framework seal (40) is flush with the first-stage inner step surface of the penetrating tube (32); the 3# framework seal (35) is positioned and installed on the inner wall of the penetrating tube (32) on the right side of the second-stage inner step surface of the penetrating tube (32) through the seam allowance, and the left end surface of the 3# framework seal (35) is flush with the second-stage inner step surface of the penetrating tube (32).

3. The calibration device for the flow coefficient of the balance hole of the centrifugal pump impeller according to claim 1, wherein: in the rotor component, an impeller (3) is fixedly arranged on a pump shaft (44) through a key (37), an impeller preformed hole (2) is formed in the position, with a smaller radius, of a rear cover plate (4) of the impeller, a balance hole disc (10) is positioned and arranged on the pump shaft (44) and the key (37) through a spigot on a hub of the impeller (3), two stages of outer steps are machined on the outer side of the balance hole disc (10) from the right side end face of the balance hole disc (10) to the left along the axial direction from right to left, and the outer step faces are perpendicular to a central axis; the outer surface of the left side of the balance hole disc (10) is matched with the sealing lip of the No. 2 framework seal (40), the outer surface of the right side of the balance hole disc (10) is matched with the sealing lip of the No. 3 framework seal (35), and a gap is reserved between the first-stage step surface of the right side of the balance hole disc (10) and the left end of the No. 3 framework seal (35); the impeller (3) and the balance hole disc (10) are axially fixed on the pump shaft (44) through a round nut (34); the balance hole (36) is horizontally arranged on the balance hole disc (10) along the axial direction; the 1# framework seal (42) is arranged on the inner side of the impeller seal ring (41), the left end face of the 1# framework seal (42) is attached to the impeller rear cover plate (4), and the seal lip of the 1# framework seal (42) is matched with the left outer surface of the penetrating cylinder (32).

4. The calibration device for the flow coefficient of the balance hole of the centrifugal pump impeller according to claim 1, wherein: in the pressure test unit, 1# pressure taking holes (9) are reversed L-shaped holes vertically formed in the left part of a balance hole disc (10) along the radial direction and the axial direction, the number of the 1# pressure taking holes (9) is equal to that of the balance holes (36), and a 1# pressure measuring cavity (8) is defined by an impeller rear cover plate (4), the balance hole disc (10), a 2# framework seal (40), a first-stage step surface of a penetrating cylinder (32), the inner wall of the penetrating cylinder (32) and the 1# framework seal (42); the 1# pressure measuring catheter (16) is arranged on the penetrating tube (32), the left end of the 1# pressure measuring catheter (16) is communicated with the 1# pressure measuring cavity (8), the right end of the 1# pressure measuring catheter (16) is communicated with the left end of the 1# pressure hose (19) through a 1# thread pair connector (17), the 2# pressure taking holes (12) are short holes which are vertically arranged on the right part of the balance hole disc (10) along the radial direction, the number of the 2# pressure taking holes (12) is equal to that of the balance holes (36), and the 2# pressure measuring cavity (11) is defined by the outer surface of the balance hole disc (10), the second-stage outer step surface of the balance hole disc (10), the 3# framework seal (35), the second-stage step surface of the penetrating tube (32), the inner wall of the penetrating tube (32) and the 2# framework seal (40); the 2# pressure measuring catheter (31) is horizontally arranged on the penetrating cylinder (32) along the axial direction, the left end of the 2# pressure measuring catheter (31) is communicated with the 2# pressure measuring cavity (11), and the right end of the 2# pressure measuring catheter (31) is communicated with the left end of the 2# pressure hose (20) through the 2# wire-matching joint (18).

5. The calibration device for the flow coefficient of the balance hole of the centrifugal pump impeller according to claim 1, wherein: in the leakage quantity testing unit, a drainage cavity (13) is defined by the outer surface of a penetrating cylinder (32), the left side surface of a flange disc of the penetrating cylinder (32), the inner wall surface of a cylinder on the right side of a rear pump cover (6), the right side end surface of a rear sealing ring (39), an impeller sealing ring (41) and a No. 1 framework seal (42); two water guide pipes (47) are symmetrically and fixedly arranged on two sides of a right cylinder of a rear pump cover (6) along the radial direction, the symmetrical central axes of the two water guide pipes (47) are equal to the central line of a pump shaft (44) in height, flanges on the left sides of the water guide pipes (47) are butted with flanges on two sides of the right cylinder of the rear pump cover (6) and fixedly connected together by an E group bolt-nut assembly (45), the flanges on the right sides of the water guide pipes (47) are butted with flanges on two sides of a backflow cavity (27) and fixedly connected together by an F group bolt-nut assembly (46), the flange on the left side of the backflow cavity (27) is butted with a flange on the right side of an electromagnetic flowmeter (29) and fixedly connected together by a D group bolt-nut assembly (28), the flange on the left side of the electromagnetic flowmeter (29) is butted with a flange on the right side of a transparent cylinder (32) and fixedly connected together by a C group bolt-nut assembly (30), the inner wall surface of the transparent cylinder (32), and a No. 3 skeleton seal (35), A balance cavity (14) is defined by the right end faces of the balance hole disc (10), the round nut (34) and the pump shaft (44); the balancing hole (36) communicates the balancing chamber (14) with the inlet of the impeller (3).