A method for predicting the cavitation head of an inducer centrifugal pump and a centrifugal pump test system

Abstract

The application discloses a cavitation head prediction method of an inducer centrifugal pump and a centrifugal pump test system, and relates to the technical field of pump performance prediction. s ; the first critical cavitation point NPSHR Ⅰ , the second critical cavitation point NPSHR Ⅱ , the relative head drop value, and a cavitation head prediction curve is generated on the basis. The cavitation head of the inducer centrifugal pump after cavitation can be predicted by measuring the structural parameters of the inducer centrifugal pump, and the required parameters are few and the accuracy is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pump performance prediction, and more particularly to a method for predicting the cavitation head of an inducer centrifugal pump and a centrifugal pump test system. BACKGROUND

[0002] Centrifugal pumps are widely used in the fields of agricultural irrigation, water conservancy and hydropower, petrochemical industry, aerospace, metallurgy and light industry, etc. With the continuous development of petrochemical industry and aerospace technology, especially in the transportation of easily vaporized medium and low temperature medium, the flow parts are more susceptible to cavitation damage. In order to avoid cavitation in high-speed centrifugal pumps, one of the most important methods to improve the anti-cavitation performance of high-speed centrifugal pumps is to install an inducer in front of the impeller. The performance of the inducer itself will interfere with the impeller to some extent, and when cavitation occurs in the inducer, especially when unstable cavitation flow occurs, it will have a certain impact on the internal flow characteristics and overall performance of the centrifugal pump. For example, the occurrence of rotational cavitation in the inducer will make the flow state at the inlet of the impeller more turbulent, reducing the reliability of the centrifugal pump operation, and thus having a greater impact on the cavitation performance curve of the centrifugal pump, making the original device performance curve unable to predict the performance of the existing centrifugal pump.

[0003] Therefore, in view of the deficiencies in the prior art, how to provide a method for predicting the cavitation head of an inducer centrifugal pump to predict the cavitation head of the inducer centrifugal pump after cavitation occurs is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0004] Therefore, the present application provides a method for predicting the cavitation head of an inducer centrifugal pump and a centrifugal pump test system, which solves the problems in the background art.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] A method for predicting the cavitation head of an inducer centrifugal pump, comprising the following steps:

[0007] Collecting the structural parameters of the inducer centrifugal pump;

[0008] According to the operating flow rate Q and the rotational speed n of the inducer centrifugal pump, the specific speed n of the inducer centrifugal pump is determined s ;

[0009] Based on the change of the device net positive suction head NPSHR a , the first critical cavitation point NPSHR Ⅰ of the inducer centrifugal pump is determined;

[0010] Based on the critical cavitation head NPSHR cri , the second critical cavitation point NPSHRⅡ ;

[0011] The relative head drop of the induced draft centrifugal pump was calculated.

[0012] Based on the relative value of the head reduction of the inducer centrifugal pump Critical cavitation point NPSHR Ⅰ The second critical cavitation point NPSHR Ⅱ and specific speed n s Generate a cavitation head prediction curve.

[0013] Optionally, the structural parameters of the inducer centrifugal pump include: the impeller outlet diameter D of the centrifugal wheel. c2 Blade inlet diameter D cc1 The diameter D of the inlet rim of the inducer. it1 Export rim diameter D it2 Imported wheel hub diameter d ih1 Export hub diameter d ih2 axial length of the hub l it The relative liquid level angle β of the average effective diameter of the inlet i1 The relative liquid level angle of the outlet average effective diameter and the hub diameter β i2 Inducer wheel blade flow channel length L i chord length of the rim section l i .

[0014] Optionally, the first critical cavitation point (NPSHR) of the inducer centrifugal pump. Ⅰ To increase the net positive suction head (NPSHR) of the unit a The point on the cavitation head prediction curve that appears to change as the cavitation head gradually decreases is expressed as:

[0015]

[0016] in:

[0017] Average speed of the inlet shaft surface of the inducer

[0018] Comprehensive parameters The range is 0.2 to 0.75;

[0019] Fluid flow angle β' at the average effective diameter of the inducer inlet ip1 =arctan(v im1 / u ip1 );

[0020] Circumferential velocity u at the average effective diameter of the inducer inlet ip1 =πD ip1 n / 60;

[0021] Average effective diameter at the inducer inlet

[0022] Blade solidity at the inducer shroud

[0023] Peripheral velocity u at the inducer inlet average diameter iAV1 = πD iAV1 / 60;

[0024] Inducer inlet average diameter D iAV1 = (D it1 + d ih1 ) / 2;

[0025] In the formula: Q represents the operating flow of the inducer centrifugal pump, m 3 / h; n represents the operating speed of the inducer centrifugal pump, rpm; g represents the acceleration of gravity, β ip1 represents the relative liquid level angle at the effective diameter of the inlet, β ip2 represents the relative liquid level angle at the effective diameter of the outlet, Z i represents the number of inducer blades, β it1 represents the relative liquid level angle at the shroud of the inlet, β it2 represents the relative liquid level angle at the shroud of the outlet, D it represents the inducer shroud diameter.

[0026] The second critical cavitation point NPSHR of the inducer centrifugal pump Ⅱ is the critical net positive suction head NPSHR cri The corresponding working point, the cavitation head appears a sharp drop, the expression is:

[0027]

[0028] Among them:

[0029] Average axial velocity at the inducer inlet

[0030] Equivalent diameter velocity coefficient of the inducer

[0031] Relative thickness of the inducer blade inlet section

[0032] Inducer inlet average diameter D iAV1 = (D it1 + d ih1 ) / 2;

[0033] Relative length of the inducer blade passage

[0034] Inducer inlet section wedge WD i = SiAV1 / D iAV1 ;

[0035] Inducer inlet average diameter at circumferential velocity u iAV1 = πD iAV1 n / 60;

[0036] wherein: Q represents the operating flow rate of the inducer centrifugal pump, m 3 / h; n represents the operating rotational speed of the inducer centrifugal pump, rpm; g represents the acceleration of gravity, D iAV2 represents the inducer outlet average diameter, S iAV1 represents the inducer inlet average tip length, represents the inducer inlet edge thickness, L iAV represents the inducer average blade passage length.

[0037] The relative value of the inducer centrifugal pump head drop is expressed as:

[0038]

[0039] wherein:

[0040] Centrifugal wheel blade solidity s c = Z c (D c2 -D cc1 ) / (D c2 +D cc1 );

[0041] Inducer average diameter at circumferential velocity u

[0042] Comprehensive parameter ranges from 0.2 to 0.75;

[0043] Inducer inlet average effective diameter at liquid flow angle β' ip1 = arctan(v im1 / u ip1 );

[0044] Inducer inlet average axial face velocity

[0045] Inducer inlet average effective diameter at circumferential velocity u ip1 = πD ip1 n / 60;

[0046] Inducer inlet average effective value diameter

[0047] wherein: Q represents the operating flow rate of the inducer centrifugal pump, m 3h; n represents the operating speed of the inducer centrifugal pump, rpm; Z c represents the number of blades of the centrifugal wheel, β ∑ represents the blade bending angle, Z i represents the number of blades of the inducer, L iAV represents the average blade passage length of the inducer, β iAV1 represents the average blade setting angle at the inducer inlet, β iAV2 represents the average blade setting angle at the inducer outlet, D iAV represents the average diameter of the inducer.

[0048] Optionally, the device NPSHR a is expressed as:

[0049]

[0050] In the formula: P in represents the inlet pressure of the centrifugal pump, Pa; P V represents the saturated vapor pressure of the medium at the working temperature, Pa; g represents the acceleration of gravity, and p represents the density of the operating medium.

[0051] Optionally, the expression of the cavitation head prediction curve is:

[0052]

[0053] In the formula: represents the cavitation head.

[0054] A centrifugal pump test system applied to the cavitation head prediction method of the inducer centrifugal pump described in any one of the above, comprising: a liquid phase circulation system, a gas supply system and a pump section;

[0055] The liquid phase circulation system comprises a cavitation tank, an outlet stop valve, an exhaust water tank, an inlet water pipeline, an inlet electromagnetic flowmeter, an inlet regulating valve, and an outlet regulating valve; the gas supply system comprises an air compressor, a gas pressure stabilizing tank, an inlet gas pipeline, a gas mass flowmeter, a gas pressure stabilizing valve, a gas outlet regulating valve and a gas mixing structure; and the pump section comprises a centrifugal pump and a motor.

[0056] The bottom outlet of the cavitation tank is connected to the inlet end of the centrifugal pump through the inlet water pipeline provided with the inlet regulating valve and the inlet electromagnetic flowmeter;

[0057] The outlet end of the centrifugal pump is connected to the outlet pipeline provided with the outlet regulating valve, and the outlet pipeline extends into the inlet of the exhaust water tank, and the bottom outlet of the exhaust water tank is connected to the middle part of the cavitation tank through the backwater pipeline provided with the outlet stop valve;

[0058] The air compressor is connected with the inlet end of the gas pressure stabilizing tank, and the outlet end of the gas pressure stabilizing tank is connected to the water inlet pipeline through a gas outlet adjusting valve, a gas pressure stabilizing valve and a gas mass flow meter.

[0059] Optionally, the cavitation tank is a sealed cylindrical water tank.

[0060] According to the technical scheme, compared with the prior art, the cavitation head prediction method of the inducer centrifugal pump and the centrifugal pump test system can predict the cavitation head of the inducer centrifugal pump that occurs cavitation by measuring the structural parameters of the inducer centrifugal pump, the required parameters are few, and only the sealing gap of the centrifugal pump that occurs wear needs to be measured, when the specific speed of the centrifugal pump is in the range of 120-350, the prediction fitting accuracy of the head curve of the centrifugal pump reaches more than 95%. BRIEF DESCRIPTION OF DRAWINGS

[0061] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0062] Figure 1 The flow chart of the cavitation head prediction method of the inducer centrifugal pump provided by the present application;

[0063] Figure 2 The axial section view of the inducer provided by the present application;

[0064] Figure 3 The development view at the diameter D of the inducer provided by the present application;

[0065] Figure 4 The axial section view of the centrifugal wheel provided by the present application;

[0066] Figure 5 The structural schematic view of the centrifugal pump test system provided by the present application;

[0067] Figure 6 The cavitation performance and prediction curve diagram of the inducer centrifugal pump provided by the present application;

[0068] The drawings show that: 1 is a cavitation tank, 2 is an outlet stop valve, 3 is an exhaust water tank, 4 is an inlet regulating valve, 5 is an inlet electromagnetic flowmeter, 6 is an outlet regulating valve, 7 is an air compressor, 8 is a gas pressure stabilizing tank, 9 is a gas outlet regulating valve, 10 is a gas pressure stabilizing valve, 11 is a gas mass flow meter, and 12 is a centrifugal pump. DETAILED DESCRIPTION

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] Because the performance of the inducer itself can interfere with the impeller to some extent, when cavitation occurs in the inducer, especially when unstable cavitation flow occurs, it will have a certain impact on the internal flow characteristics and overall performance of the centrifugal pump, making the original device performance curve no longer able to predict the performance of the existing centrifugal pump.

[0071] Therefore, this invention discloses a method for predicting the cavitation head of an induced draft centrifugal pump, such as... Figure 1 As shown, it includes the following steps:

[0072] Collect the structural parameters of the inducer centrifugal pump;

[0073] Determine the specific speed n of the induced wheel centrifugal pump based on its operating flow rate Q and rotational speed n. s ;

[0074] Based on the device's net positive suction head (NPSHR) a The changes determined the first critical cavitation point (NPSHR) of the induced wheel centrifugal pump. Ⅰ ;

[0075] Based on critical net positive suction head (NPSHR) cri Determine the second critical cavitation point (NPSHR) of the induced wheel centrifugal pump. Ⅱ ;

[0076] The relative head drop of the induced draft centrifugal pump was calculated.

[0077] Based on the relative value of the head reduction of the inducer centrifugal pump Critical cavitation point NPSHR Ⅰ The second critical cavitation point NPSHR Ⅱ and specific speed n s Generate a cavitation head prediction curve.

[0078] Furthermore, referring to Figures 2-4 The structural parameters of the induced draft centrifugal pump include: the impeller outlet diameter D of the centrifugal wheel. c2 Blade inlet diameter D cc1 The diameter D of the inlet rim of the inducer. it1 Export rim diameter D it2 Imported wheel hub diameter d ih1Export hub diameter d ih2 axial length of the hub l it The relative liquid level angle β of the average effective diameter of the inlet i1 The relative liquid level angle of the outlet average effective diameter and the hub diameter β i2 Inducer wheel blade flow channel length L i chord length of the rim section l i .

[0079] Furthermore, the first critical cavitation point (NPSHR) of the induced draft centrifugal pump... Ⅰ To increase the net positive suction head (NPSHR) of the unit a The point on the cavitation head prediction curve that appears to change as the cavitation head gradually decreases is expressed as:

[0080]

[0081] in:

[0082] Average speed of the inlet shaft surface of the inducer

[0083] Comprehensive parameters The range is 0.2 to 0.75;

[0084] Fluid flow angle β' at the average effective diameter of the inducer inlet ip1 =arctan(v im1 / u ip1 );

[0085] Circumferential velocity u at the average effective diameter of the inducer inlet ip1 =πD ip1 n / 60;

[0086] Induction wheel inlet average effective diameter

[0087] Density of filaments at the rim of the inducer wheel

[0088] Circumferential velocity u at the average diameter of the inducer inlet iAV1 =πD iAV1 n / 60;

[0089] Average diameter D of the inducer inlet iAV1 =(D it1 +d ih1 ) / 2;

[0090] In the formula: Q represents the operating flow rate of the induced draft centrifugal pump, m 3 / h; n represents the operating speed of the inducer centrifugal pump, rpm; g represents the acceleration due to gravity, β ip1 β represents the relative liquid level angle at the effective diameter of the inlet.ip2 represents the relative liquid level angle at the outlet effective diameter, Z i represents the blade number of the inducer, β it1 represents the relative liquid level angle at the inducer inlet, β it2 represents the relative liquid level angle at the inducer outlet, D it represents the inducer rim diameter.

[0091] Further, the second critical cavitation point NPSHR of the inducer centrifugal pump Ⅱ is the critical net positive suction head NPSHR cri corresponds to the working condition point, at which the performance of the pump is seriously deteriorated, and the cavitation head appears a sharp drop, and the expression is:

[0092]

[0093] wherein:

[0094] the inducer inlet axial surface average velocity

[0095] the inducer equivalent diameter velocity coefficient

[0096] the relative thickness of the inducer blade inlet section

[0097] the inducer inlet average diameter D iAV1 = (D it1 +d ih1 ) / 2;

[0098] the inducer blade passage relative length

[0099] the inducer inlet section wedge degree WD i =S iAV1 / D iAV1 , and the value range is 0-3.5;

[0100] the inducer inlet average diameter circumferential velocity u iAV1 =πD iAV1 n / 60;

[0101] In the formula, Q represents the running flow of the inducer centrifugal pump, m 3 / h; n represents the running speed of the inducer centrifugal pump, rpm; g represents the gravity acceleration, D iAV2 represents the inducer outlet average diameter, S iAV1 represents the inducer inlet average trimming length, represents the inducer inlet edge thickness, L iAV represents the inducer average blade passage length.

[0102] Further, the expression of the relative value of the head drop of the inducer centrifugal pump is:

[0103]

[0104] wherein:

[0105] The inducer centrifugal pump c = Z c (D c2 -D cc1 ) / (D c2 +D cc1 );

[0106] The inducer centrifugal pump

[0107] The comprehensive parameter ranges from 0.2 to 0.75;

[0108] The inducer centrifugal pump ip1 = arctan(v im1 / u ip1 );

[0109] The inducer centrifugal pump

[0110] The inducer centrifugal pump ip1 = πD ip1 n / 60;

[0111] The inducer centrifugal pump

[0112] wherein: Q represents the running flow of the inducer centrifugal pump, m 3 / h; n represents the running speed of the inducer centrifugal pump, rpm; Z c represents the number of blades of the centrifugal wheel, β ∑ represents the blade bending angle, Z i represents the number of blades of the inducer, L iAV represents the average blade channel length of the inducer, β iAV1 represents the average blade setting angle of the inducer at the inlet, β iAV2 represents the average blade setting angle of the inducer at the outlet, D iAV represents the average diameter of the inducer.

[0113] Further, the expression of the net positive suction head of the device NPSHR a is:

[0114]

[0115] wherein: Pin represents the inlet pressure of the centrifugal pump, Pa; P V represents the saturated vapor pressure of the medium at the working temperature, Pa; g represents the acceleration of gravity, and p represents the density of the operating medium.

[0116] Further, the expression of the cavitation head prediction curve is:

[0117]

[0118] In the formula, H represents the cavitation head.

[0119] As shown in Figure 5 , the embodiment provides a centrifugal pump test system, which comprises a liquid phase circulation system, a gas supply system and a pump section.

[0120] The liquid phase circulation system comprises a cavitation tank 1, an outlet stop valve 2, an exhaust water tank 3, an inlet water pipeline, an inlet electromagnetic flowmeter 5, an inlet regulating valve 4, an outlet regulating valve 6; the gas supply system comprises an air compressor 7, a gas pressure stabilizing tank 8, an inlet gas pipeline, a gas mass flowmeter 11, a gas pressure stabilizing valve 10, a gas outlet regulating valve 9 and a gas mixing structure; and the pump section comprises a centrifugal pump 12 and a motor.

[0121] The bottom outlet of the cavitation tank 1 is connected to the inlet end of the centrifugal pump 12 through the inlet water pipeline provided with the inlet regulating valve 4 and the inlet electromagnetic flowmeter 5.

[0122] The outlet end of the centrifugal pump 12 is connected to the outlet pipeline provided with the outlet regulating valve 6, the outlet pipeline extends into the inlet of the exhaust water tank 3, and the bottom outlet of the exhaust water tank 3 is connected to the middle part of the cavitation tank 1 through the backwater pipeline provided with the outlet stop valve 2.

[0123] The air compressor 7 is connected to the inlet end of the gas pressure stabilizing tank 8, and the outlet end of the gas pressure stabilizing tank 8 is connected to the inlet water pipeline through the inlet gas pipeline provided with the gas outlet regulating valve 9, the gas pressure stabilizing valve 10 and the gas mass flowmeter 11. The cavitation tank 1 is a sealed cylindrical water tank.

[0124] The centrifugal pump test part adopts two centrifugal pumps with different specific speeds for research, and the inducer cavitation test part adopts a centrifugal pump with a front inducer with a specific speed of n s = 25, the shell is made of organic glass, and the design parameters are Q d = 8 m 3 / h, n = 2900 r / min and H d = 38 m. The data acquisition instrument used in the test is mainly used for collecting the external characteristic parameters of the centrifugal pump, such as pump inlet and outlet pressure, rotating speed and the like, and the pump data is collected through two ways of electric measurement and torque method, and the pressure and flow are measured at the same time.

[0125] The method is used to predict the cavitation head, and the first critical cavitation point NPSHR Ⅰ , the second critical cavitation point NPSHR Ⅱ , and the relative head drop value

[0126] Among them,

[0127]

[0128] The first critical cavitation point

[0129]

[0130] The second critical cavitation point

[0131]

[0132] The relative head drop value

[0133]

[0134] When NPSHR a ≥6.04m, the head

[0135]

[0136] When NPSHR a <6.04m, the head

[0137]

[0138] n s =25, the prediction results of the cavitation performance curve of the inducer centrifugal pump are shown in Figure 6 It can be seen that the cavitation head prediction curve is basically consistent with the test results as a whole, but there is still a certain deviation between the first critical cavitation point and the second critical cavitation point, but the deviation is relatively small. For the same device, the deviation of the head a is basically within 0.5% under the cavitation allowance NPSHR .

[0139] In the specification, each embodiment is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between each embodiment can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the method part.

[0140] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of predicting the net positive suction head for inducer wheel centrifugal pumps, characterized by, The method comprises the following steps: Collecting the structural parameters of the inducer centrifugal pump; Determination of operating flow rate of an inducer centrifugal pump Q and rotational speed n , determination of specific speed of an inducer centrifugal pump ; Determining the first critical cavitation point of an inducer centrifugal pump based on changes in the device net positive suction head ;​ Based on a critical cavitation margin , determining a second critical cavitation point of an inducer centrifugal pump ; The relative value of the head drop of the induced wheel centrifugal pump is calculated ; According to the relative value of the head drop of an inducer centrifugal pump The first critical cavitation point The second critical cavitation point And specific speed A cavitation head prediction curve is generated The structural parameters of the inducer centrifugal pump include: inducer outlet diameter of the centrifugal wheel , blade inlet diameter ; inducer inlet rim diameter , outlet rim diameter , inlet hub diameter , outlet hub diameter , hub axial length , relative liquid level angle of the inlet average effective diameter , relative liquid level angle of the outlet average effective diameter hub diameter , inducer blade channel length , rim section chord length ; The first critical cavitation point of the inducer centrifugal pump To increase the net positive suction head (NPSH) of the unit The point on the cavitation head prediction curve that appears to change as the cavitation head gradually decreases is expressed as: Wherein: Induced wheel inlet axial face average velocity ; Comprehensive parameters in the range of 0.2 to 0.75; Induced wheel inlet average effective diameter at flow angle ; Induced wheel inlet average effective diameter circumferential velocity ; Induced wheel inlet average effective value diameter ; Induced wheel rim porosity ; Induced wheel inlet average diameter circumferential velocity ; Induced wheel inlet average diameter ; wherein: Q Qind represents the operating flow rate of the inducer centrifugal pump, ; n Nind represents the operating rotational speed of the inducer centrifugal pump, rpm; g g represents the acceleration of gravity, a represents the relative liquid level angle at the inlet effective diameter, b represents the relative liquid level angle at the outlet effective diameter, Nind represents the number of inducer blades, a represents the relative liquid level angle at the inlet rim, b represents the relative liquid level angle at the outlet rim, Dind represents the inducer rim diameter; Inducing the second critical cavitation point of centrifugal pump The critical cavitation margin The corresponding operating point, the cavitation head appears a sharp drop, the expression is: Wherein: Induced wheel inlet axial face average velocity ; Induced wheel diameter speed coefficient ; Relative thickness of inducer vane inlet section ; Induced wheel inlet average diameter ; Induced wheel blade flow passage relative length ; Inducing wheel inlet section wedge ; Induced wheel inlet average diameter circumferential velocity ; wherein: Q Q represents the operating flow rate of the inducer centrifugal pump, ; n N represents the operating rotational speed of the inducer centrifugal pump, rpm; g g represents the acceleration of gravity, D represents the average diameter of the inducer outlet, L represents the average length of the inducer inlet tip, t represents the inducer inlet edge thickness, L represents the average blade passage length of the inducer. Relative value of head drop of an inducer wheel centrifugal pump The expression for the relative value of head drop of an inducer wheel centrifugal pump is: Wherein: Centrifuge wheel blade density ; Induced wheel average diameter at leaf density ; Comprehensive parameters in the range of 0.2 to 0.75; Induced wheel inlet average effective diameter at flow angle ; Induced wheel inlet axial face average velocity ; Induced wheel inlet average effective diameter circumferential velocity ; Induced wheel inlet average effective value diameter ; wherein: Q Qind represents the operating flow rate of the inducer centrifugal pump, ; n Nind represents the operating rotational speed of the inducer centrifugal pump, rpm; N represents the number of centrifugal wheel blades, B represents the blade bend angle, Nind represents the number of inducer blades, Lind represents the average blade passage length of the inducer, Aind represents the average blade setting angle at the inducer inlet, Aind represents the average blade setting angle at the inducer outlet, Dind represents the average diameter of the inducer.

2. A method of predicting the NPSR of an inducer centrifugal pump according to claim 1, characterized in that, Device net positive suction head The expression for the net positive suction head is: wherein: denotes the pressure at the inlet of the centrifugal pump, Pa; denotes the saturation vapor pressure of the medium at the operating temperature, Pa; g denotes the acceleration due to gravity, denotes the density of the operating medium.

3. A method of predicting the NPS of a centrifugal pump with inducer according to claim 1, characterized in that, The expression of the cavitation head prediction curve is: In the formula: represents the net positive suction head.

4. A centrifugal pump testing system characterized by, The cavitation head prediction method is applied to the inducer centrifugal pump according to any one of claims 1-3, comprising a liquid phase circulation system, a gas supply system and a pump section. The liquid phase circulation system comprises a cavitation tank, an outlet stop valve, an exhaust water tank, an inlet water pipeline, an inlet electromagnetic flowmeter, an inlet regulating valve, and an outlet regulating valve; the gas supply system comprises an air compressor, a gas pressure stabilizing tank, an inlet gas pipeline, a gas mass flowmeter, a gas pressure stabilizing valve, a gas outlet regulating valve and a gas mixing structure; and the pump section comprises a centrifugal pump and a motor. The bottom outlet of the cavitation tank is connected to the inlet end of the centrifugal pump through the inlet water pipeline provided with the inlet regulating valve and the inlet electromagnetic flowmeter. The outlet end of the centrifugal pump is connected to the outlet pipeline provided with the outlet regulating valve, and the outlet pipeline extends into the inlet of the exhaust water tank; the bottom outlet of the exhaust water tank is connected to the middle part of the cavitation tank through the backwater pipeline provided with the outlet stop valve. The air compressor is connected to the inlet end of the gas pressure stabilizing tank, and the outlet end of the gas pressure stabilizing tank is connected to the inlet water pipeline through the inlet gas pipeline provided with the gas outlet regulating valve, the gas pressure stabilizing valve and the gas mass flowmeter.

5. A centrifugal pump testing system according to claim 4, wherein, The cavitation tank is a sealed cylindrical water tank.

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