Cavitation lift prediction method of inducer centrifugal pump and centrifugal pump test system

Abstract

The invention discloses a cavitation lift prediction method of an inducer centrifugal pump and a centrifugal pump test system, and relates to the technical field of pump performance prediction.The cavitation lift prediction method comprises the steps that structural parameters of the inducer centrifugal pump are collected; according to the running flow Q and the rotating speed n of the inducer centrifugal pump, the specific rotating speed ns of the inducer centrifugal pump is determined; and the first critical cavitation point NPSHRI, the second critical cavitation point NPSHRII and the lift drop relative value # imgabs0 # of the inducer centrifugal pump are determined, and then a cavitation lift prediction curve is generated on the basis of the first critical cavitation point NPSHRI, the second critical cavitation point NPSHRII and the lift drop relative value # imgabs0 #. According to the method, the cavitation lift of the inducer centrifugal pump after cavitation can be predicted by measuring the structural parameters of the inducer centrifugal pump, the required parameters are few, and the accuracy is high.

Description

Technical Field

[0001] The invention 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 testing system. Background Art

[0002] Centrifugal pumps are widely used in agricultural irrigation, water conservancy and hydropower, petrochemical industry, aerospace, metallurgy and light industry. With the continuous development of petrochemical industry and aerospace technology, especially when transporting easily vaporized media and low-temperature media, the flow-through parts are more susceptible to cavitation damage. In order to avoid premature cavitation in high-speed centrifugal pumps, installing an inducer in front of the impeller is one of the most important methods to improve the anti-cavitation performance of high-speed centrifugal pumps. The performance of the inducer itself will interfere with the impeller to a certain 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. For example, the rotational cavitation of the inducer will cause the flow state at the impeller inlet to be more chaotic, reduce the reliability of the centrifugal pump operation, and then have a greater impact on the cavitation performance curve of the centrifugal pump, making it impossible for the original device performance curve 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 technical personnel in this field urgently need to solve. Summary of the invention

[0004] In view of this, the present invention provides a method for predicting the cavitation head of an inducer centrifugal pump and a centrifugal pump testing system, which solve the problems existing in the background technology.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

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

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

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

[0009] Based on the device NPSH a The change of the inducer centrifugal pump is used to determine the first critical cavitation point NPSHR Ⅰ ;

[0010] Based on critical NPSH cri , determine the second critical cavitation point NPSHR of the inducer centrifugal pumpⅡ ;

[0011] Calculate the relative value of the head drop of the inducer centrifugal pump

[0012] According to the relative value of the head drop of the inducer centrifugal pump First critical cavitation point NPSHR Ⅰ 、The second critical cavitation point NPSHR Ⅱ And specific speed n s , generate the 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 ; Diameter D of the inlet rim of the inducer it1 , outlet rim diameter D it2 , imported wheel hub diameter d ih1 , outlet hub diameter d ih2 , hub axial length l it , relative liquid level angle β of the average effective diameter of the inlet i1 , the relative liquid level angle of the average effective outlet diameter is the hub diameter β i2 , inducer blade flow path length L i , chord length of rim section l i .

[0014] Optional, inducer centrifugal pump first critical cavitation point NPSHR Ⅰ As the device NPSH a The point where the cavitation head prediction curve changes due to the gradual decrease of , the expression is:

[0015]

[0016] in:

[0017] Average speed of inducer inlet shaft

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

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

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

[0021] Average effective diameter of inducer inlet

[0022] Density of leaf coral at the inducer rim

[0023] Circumferential speed u at the average diameter of the inducer inlet iAV1 =πD iAV1 n / 60;

[0024] Average inlet diameter of inducer D iAV1 =(D it1 +d ih1 ) / 2;

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

[0026] Optional, inducer centrifugal pump second critical cavitation point NPSHR Ⅱ NPSHR is the critical NPSH cri At the corresponding operating point, the cavitation head drops sharply, and the expression is:

[0027]

[0028] in:

[0029] Average speed of inducer inlet shaft

[0030] Inducer equivalent diameter speed coefficient

[0031] Relative thickness of the inlet section of the inducer blade

[0032] Average inlet diameter of inducer D iAV1 =(D it1 +d ih1 ) / 2;

[0033] Relative length of inducer blade flow passage

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

[0035] Circumferential speed u at the average diameter of the inducer inlet iAV1 =πD iAV1 n / 60;

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

[0037] Optional, relative value of head drop of inducer centrifugal pump The expression is:

[0038]

[0039] in:

[0040] Centrifugal impeller density c =Z c (D c2 -D cc1 ) / (D c2 +D cc1 );

[0041] Density of leaf sedge at the average diameter of the inducer

[0042] Comprehensive parameters The range is 0.2 to 0.75;

[0043] Flow angle β' at the average effective diameter of the inducer inlet ip1 =arctan(v im1 / u ip1 );

[0044] Average speed of inducer inlet shaft

[0045] Circumferential speed u at the average effective diameter of the inducer inlet ip1 =πD ip1 n / 60;

[0046] Average effective diameter of inducer inlet

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

[0048] Optionally, device NPSH a The expression is:

[0049]

[0050] Where: P in Indicates the centrifugal pump inlet pressure, Pa; P V It represents the saturated vapor pressure of the medium at the operating temperature, Pa; g represents the acceleration of gravity, and ρ represents the density of the operating medium.

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

[0052]

[0053] Where: Indicates cavitation head.

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

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

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

[0057] The outlet end of the centrifugal pump is connected to an outlet pipeline equipped with an outlet regulating valve, 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 of the cavitation tank through a return water pipeline equipped with an outlet stop valve;

[0058] 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 water inlet pipeline through an air inlet pipeline equipped with a gas outlet regulating valve, a gas pressure stabilizing valve and a gas mass flow meter.

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

[0060] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a cavitation head prediction method for an inducer centrifugal pump and a centrifugal pump testing system, which can predict the cavitation head of an inducer centrifugal pump with cavitation by measuring the structural parameters of the inducer centrifugal pump. Few parameters are required, and it is only necessary to measure the seal clearance of the worn centrifugal pump. When the specific speed of the centrifugal pump is in the range of 120 to 350, the prediction fitting accuracy of the head curve of the centrifugal pump reaches more than 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0062] Figure 1 A flow chart of a method for predicting the cavitation head of an inducer centrifugal pump provided by the present invention;

[0063] Figure 2 A sectional view of the axial surface of the inducer provided by the present invention;

[0064] Figure 3 The expansion diagram of the inducer provided by the present invention at the diameter D;

[0065] Figure 4 A schematic diagram of the centrifugal wheel axis provided by the present invention;

[0066] Figure 5 A schematic diagram of the structure of a centrifugal pump testing system provided by the present invention;

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

[0068] Figure markings: 1-cavitation tank, 2-outlet stop valve, 3-exhaust water tank, 4-import regulating valve, 5-import electromagnetic flowmeter, 6-outlet regulating valve, 7-air compressor, 8-gas pressure stabilizing tank, 9-gas outlet regulating valve, 10-gas pressure stabilizing valve, 11-gas mass flowmeter, 12-centrifugal pump. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] Since the performance of the inducer itself will interfere with the impeller to some extent, when cavitation occurs in the inducer, especially unstable cavitation flow, it will have a certain impact on the internal flow characteristics and overall performance of the centrifugal pump, making it impossible to use the original device performance curve to predict the performance of the existing centrifugal pump.

[0071] To this end, the embodiment of the present invention discloses a method for predicting the cavitation head of an inducer centrifugal pump, such as Figure 1 As shown, the following steps are included:

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

[0073] According to the operating flow Q and speed n of the inducer centrifugal pump, determine the specific speed n of the inducer centrifugal pump s ;

[0074] Based on the device NPSH a The change of the inducer centrifugal pump is used to determine the first critical cavitation point NPSHR Ⅰ ;

[0075] Based on critical NPSH cri , determine the second critical cavitation point NPSHR of the inducer centrifugal pump Ⅱ ;

[0076] Calculate the relative value of the head drop of the inducer centrifugal pump

[0077] According to the relative value of the head drop of the inducer centrifugal pump First critical cavitation point NPSHR Ⅰ 、The second critical cavitation point NPSHR Ⅱ And specific speed n s , generate the cavitation head prediction curve.

[0078] Further, refer to Figure 2-Figure 4 The structural parameters of the inducer centrifugal pump include: the impeller outlet diameter D of the centrifugal wheel c2 , blade inlet diameter D cc1 ; Diameter D of the inlet rim of the inducer it1 , outlet rim diameter D it2 , imported wheel hub diameter d ih1, outlet hub diameter d ih2 , hub axial length l it , relative liquid level angle β of the average effective diameter of the inlet i1 , the relative liquid level angle of the average effective outlet diameter is the hub diameter β i2 , inducer blade flow path length L i , chord length of rim section l i .

[0079] Furthermore, the first critical cavitation point NPSHR of the inducer centrifugal pump Ⅰ As the device NPSH a The point where the cavitation head prediction curve changes due to the gradual decrease of , the expression is:

[0080]

[0081] in:

[0082] Average speed of inducer inlet shaft

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

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

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

[0086] Average effective diameter of inducer inlet

[0087] Density of leaf coral at the inducer rim

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

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

[0090] Where: Q represents the operating flow rate of the inducer centrifugal pump, m 3 / h; n is the operating speed of the inducer centrifugal pump, rpm; g is the acceleration of gravity, β ip1 Indicates the relative liquid level angle at the effective inlet diameter, βip2 Indicates the relative liquid level angle at the effective outlet diameter, Z i represents the number of inducer blades, β it1 Indicates the relative liquid level angle at the inlet rim, β it2 Indicates the relative liquid level angle at the outlet rim, D it Indicates the inducer rim diameter.

[0091] Furthermore, the second critical cavitation point NPSHR of the inducer centrifugal pump Ⅱ NPSHR is the critical NPSH cri At the corresponding operating point, the performance of the pump is seriously deteriorated, and the cavitation head drops sharply. The expression is:

[0092]

[0093] in:

[0094] Average speed of inducer inlet shaft

[0095] Inducer equivalent diameter speed coefficient

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

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

[0098] Relative length of inducer blade flow passage

[0099] Inducer inlet wedge degree WD i =S iAV1 / D iAV1 , the value range is 0~3.5;

[0100] Circumferential speed u at the average diameter of the inducer inlet iAV1 =πD iAV1 n / 60;

[0101] Where: Q represents the operating flow rate of the inducer centrifugal pump, m 3 / h; n is the operating speed of the inducer centrifugal pump, rpm; g is the acceleration of gravity, D iAV2 Indicates the average outlet diameter of the inducer, S iAV1 It represents the average tip length of the inducer inlet. Indicates the inlet edge thickness of the inducer, L iAV Represents the average blade flow path length of the inducer.

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

[0103]

[0104] in:

[0105] Centrifugal impeller density c =Z c (D c2 -D cc1 ) / (D c2 +D cc1 );

[0106] Density of leaf sedge at the average diameter of the inducer

[0107] Comprehensive parameters The range is 0.2 to 0.75;

[0108] Flow angle β' at the average effective diameter of the inducer inlet ip1 =arctan(v im1 / u ip1 );

[0109] Average speed of inducer inlet shaft

[0110] Circumferential speed u at the average effective diameter of the inducer inlet ip1 =πD ip1 n / 60;

[0111] Average effective diameter of inducer inlet

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

[0113] Furthermore, the NPSH of the device a The expression is:

[0114]

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

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

[0117]

[0118] Where: Indicates cavitation head.

[0119] like Figure 5 As shown, this embodiment provides a centrifugal pump testing system, including: a liquid phase circulation system, an air supply system and a pump section;

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

[0122] The outlet end of the centrifugal pump 12 is connected to an outlet pipeline equipped with an outlet regulating valve 6, and the outlet pipeline extends into the inlet of the exhaust water tank 3. The bottom outlet of the exhaust water tank 3 is connected to the middle of the cavitation tank 1 through a return water pipeline equipped with an 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 water inlet pipeline through an air inlet pipeline equipped with a gas outlet regulating valve 9, a gas pressure stabilizing valve 10 and a gas mass flow meter 11. The cavitation tank 1 is a sealed cylindrical water tank.

[0124] The centrifugal pump test part uses two centrifugal pumps with different specific speeds for research, and the inducer cavitation test part uses a centrifugal pump with a specific speed of n s = 25 with a front inducer centrifugal pump, the casing is made of plexiglass, and its design parameters are Q d =8m 3 / h、n=2900r / min、H d =38m. The data acquisition instrument used in the test is mainly used to collect the external characteristic parameters of the centrifugal pump, such as the pump inlet and outlet pressure, speed, etc., and collects the pump data through the electrical measurement method and torque method, while measuring the pressure and flow.

[0125] To predict the cavitation head using this method, it is necessary to determine the first critical cavitation point NPSHR Ⅰ 、The second critical cavitation point NPSHR Ⅱ And the relative value of head drop

[0126] in,

[0127]

[0128] First critical cavitation point

[0129]

[0130] The second critical cavitation point

[0131]

[0132] Relative value of head drop

[0133]

[0134] When NPSHR a ≥6.04m, head

[0135]

[0136] When NPSHR a <6.04m, head

[0137]

[0138] n s =25 when the cavitation performance curve of the inducer centrifugal pump is predicted as follows Figure 6 As shown in the figure, it can be clearly seen that the cavitation head prediction curve is generally consistent with the test results. However, there is still a certain deviation between the first critical cavitation point and the second critical cavitation point, but the deviation is relatively small. The same device cavitation head NPSHR a Down, lift The deviation is basically within 0.5%.

[0139] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments 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 parts can be referred to the method part.

[0140] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the cavitation head of an inducer centrifugal pump, characterized in that: The following steps are involved: Collect the structural parameters of the inducer centrifugal pump; According to the operating flow Q and speed n of the inducer centrifugal pump, determine the specific speed n of the inducer centrifugal pump s ; Based on the device NPSH a The change of the inducer centrifugal pump is used to determine the first critical cavitation point NPSHR Ⅰ ; Based on critical NPSH cri , determine the second critical cavitation point NPSHR of the inducer centrifugal pump Ⅱ ; Calculate the relative value of the head drop of the inducer centrifugal pump According to the relative value of the head drop of the inducer centrifugal pump First critical cavitation point NPSHR Ⅰ 、The second critical cavitation point NPSHR Ⅱ And specific speed n s , generate the cavitation head prediction curve.

2. The method for predicting cavitation head of an inducer centrifugal pump according to claim 1, characterized in that: The structural parameters of the inducer centrifugal pump include: the impeller outlet diameter D of the centrifugal wheel c2 , blade inlet diameter D cc1 ; Diameter D of the inlet rim of the inducer it1 , outlet rim diameter D it2 , imported wheel hub diameter d ih1 , outlet hub diameter d ih2 , hub axial length l it , relative liquid level angle β of the average effective diameter of the inlet i1 , the relative liquid level angle of the average effective outlet diameter is the hub diameter β i2 , inducer blade flow path length L i , chord length of rim section l i .

3. The method for predicting cavitation head of an inducer centrifugal pump according to claim 2, characterized in that: The first critical cavitation point NPSHR of the inducer centrifugal pump Ⅰ As the device NPSH a The point where the cavitation head prediction curve changes due to the gradual decrease of , the expression is: in: Average speed of inducer inlet shaft Comprehensive parameters The range is 0.2 to 0.75; Flow angle β' at the average effective diameter of the inducer inlet ip1 =arctan(v im1 / u ip1 ); Circumferential speed u at the average effective diameter of the inducer inlet ip1 =πD ip1 n / 60; Average effective diameter of inducer inlet Density of leaf coral at the inducer rim Circumferential speed u at the average diameter of the inducer inlet iAV1 =πD iAV1 n / 60; Average inlet diameter of inducer D iAV1 =(D it1 +d ih1 ) / 2; Where: Q represents the operating flow rate of the inducer centrifugal pump, m 3 / h; n is the operating speed of the inducer centrifugal pump, rpm; g is the acceleration of gravity, β ip1 Indicates the relative liquid level angle at the effective inlet diameter, β ip2 Indicates the relative liquid level angle at the effective outlet diameter, Z i represents the number of inducer blades, β it1 Indicates the relative liquid level angle at the inlet rim, β it2 Indicates the relative liquid level angle at the outlet rim, D it Indicates the inducer rim diameter.

4. The method for predicting cavitation head of an inducer centrifugal pump according to claim 2, characterized in that: The second critical cavitation point NPSHR of the inducer centrifugal pump Ⅱ NPSHR is the critical NPSH cri At the corresponding operating point, the cavitation head drops sharply, and the expression is: in: Average speed of inducer inlet shaft Inducer equivalent diameter speed coefficient Relative thickness of the inlet section of the inducer blade Average inlet diameter of inducer D iAV1 =(D it1 +d ih1 ) / 2; Relative length of inducer blade flow passage Inducer inlet wedge degree WD i =S iAV1 / D iAV1 ; Circumferential speed u at the average diameter of the inducer inlet iAV1 =πD iAV1 n / 60; Where: Q represents the operating flow rate of the inducer centrifugal pump, m 3 / h; n is the operating speed of the inducer centrifugal pump, rpm; g is the acceleration of gravity, D iAV2 Indicates the average outlet diameter of the inducer, S iAV1 It represents the average tip length of the inducer inlet. Indicates the inlet edge thickness of the inducer, L iAV Represents the average blade flow path length of the inducer.

5. The method for predicting cavitation head of an inducer centrifugal pump according to claim 2, characterized in that: Relative value of head drop of inducer centrifugal pump The expression is: in: Centrifugal impeller density c =Z c (D c2 -D cc1 ) / (D c2 +D cc1 ); Density of leaf sedge at the average diameter of the inducer Comprehensive parameters The range is 0.2 to 0.75; Flow angle β' at the average effective diameter of the inducer inlet ip1 =arctan(v im1 / u ip1 ); Average speed of inducer inlet shaft Circumferential speed u at the average effective diameter of the inducer inlet ip1 =πD ip1 n / 60; Average effective diameter of inducer inlet Where: Q represents the operating flow rate of the inducer centrifugal pump, m 3 / h; n represents the operating speed of the inducer centrifugal pump, rpm; Z c Indicates the number of centrifugal wheel blades, β Σ represents the blade bending angle, Z i Indicates the number of inducer blades, L iAV represents the average blade flow path length of the inducer, β iAV1 represents the average blade placement angle at the inlet of the inducer, β iAV2 Denotes the average blade placement angle at the inducer outlet, D iAV Indicates the average diameter of the inducer.

6. The method for predicting cavitation head of an inducer centrifugal pump according to claim 1, characterized in that: Device NPSH a The expression is: Where: P in Indicates the centrifugal pump inlet pressure, Pa; P V It represents the saturated vapor pressure of the medium at the operating temperature, Pa; g represents the acceleration of gravity, and ρ represents the density of the operating medium.

7. The method for predicting cavitation head of an inducer centrifugal pump according to claim 1, characterized in that: The expression of cavitation head prediction curve is: Where: Indicates cavitation head.

8. A centrifugal pump testing system, characterized in that: A method for predicting cavitation head of an inducer centrifugal pump as claimed in any one of claims 1 to 7, comprising: a liquid phase circulation system, an air supply system and a pump section; The liquid phase circulation system includes: cavitation tank, outlet stop valve, exhaust water tank, water inlet pipeline, inlet electromagnetic flowmeter, inlet regulating valve, outlet regulating valve; the gas supply system includes: air compressor, gas pressure regulating tank, air inlet pipeline, gas mass flowmeter, gas pressure regulating valve, gas outlet regulating valve and gas mixing structure; the pump section includes: centrifugal pump and motor; The bottom outlet of the cavitation tank is connected to the inlet end of the centrifugal pump through a water inlet pipeline equipped with an inlet regulating valve and an inlet electromagnetic flowmeter; The outlet end of the centrifugal pump is connected to an outlet pipeline equipped with an outlet regulating valve, 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 of the cavitation tank through a return water pipeline equipped with an 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 water inlet pipeline through an air inlet pipeline equipped with a gas outlet regulating valve, a gas pressure stabilizing valve and a gas mass flow meter.

9. A centrifugal pump testing system according to claim 8, characterized in that: The cavitation tank is a sealed cylindrical water tank.

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