A single-channel flow measurement device and method for a mixed-flow pump with a built-in pitot tube

Abstract

The present invention discloses a flow measurement device and method for a single-channel mixed flow pump with a built-in Pitot tube. A Pitot tube assembly is arranged in the single-channel of the mixed flow pump. The Pitot tube assembly includes a circumferential Pitot tube flowmeter and a radial Pitot tube flowmeter. A plurality of pressure measuring holes are respectively arranged in the upstream direction and the downstream direction of each circumferential Pitot tube flowmeter or the radial Pitot tube flowmeter. Each pressure measuring hole in the upstream direction is connected to one side of a pressure equalizing chamber through a connecting pipe, and each pressure measuring hole in the downstream direction is connected to the other side of the pressure equalizing chamber through a connecting pipe. A pressure difference parameter is obtained from a stress sheet in the pressure equalizing chamber. By experimentally calibrating the Pitot tube assembly in the single-channel of the mixed flow pump, a relationship between the pressure difference parameter measured by the Pitot tube assembly in each channel and the flow parameter is obtained. Then, the flow passing through the channel is corrected to obtain the flow value in each channel of the final impeller.

Description

Technical Field

[0001] The invention belongs to the field of internal flow testing of fluid machinery (pumps), and in particular relates to a single-channel flow measurement device and method for a mixed-flow pump with a built-in Pitot tube. Background Art

[0002] Mixed flow pumps have been widely used in the fields of South-to-North Water Diversion, nuclear power generation, municipal water supply and drainage systems, etc. due to their large flow and moderate head. However, due to the changes in the terminal water supply demand, mixed flow pumps often need to operate under non-design conditions, resulting in a variety of turbulent structures in the internal flow field of the mixed flow pump, which increases the instability of the mixed flow pump operation. Especially when the mixed flow pump operates under partial flow conditions, stall vortices will appear in its impeller or guide vane, causing the mixed flow pump to experience rotational stall. The stall vortices in the flow channel not only block the impeller flow channel, but also propagate along the circumference of the impeller under the action of the impeller rotation, causing the flow volume of the fluid in each flow channel to fluctuate periodically over a period of time. This periodic flow fluctuation not only greatly reduces the work efficiency of the impeller, but also induces hydraulic vibration of the impeller in the radial direction, which seriously threatens the operation of the mixed flow pump unit. At present, many scholars have paid attention to the instability of the mixed flow pump caused by the flow change in the impeller flow channel, especially the self-excited vibration of the rotor caused by the uneven circumferential distribution of the flow in each impeller flow channel. Li et al. (Numerical investigation of energy loss mechanism of mixed-flow pump under stall condition [J]. Renewable Energy, 2020, (167): 740-760) studied the fluid flow rate in different flow channels of mixed flow pumps and found that the fluid flow rate in different flow channels of the impeller was different under stall conditions. Li Enda (Study on the flow instability mechanism of mixed-flow water jet propulsion pump [D]. Jiangsu: Jiangsu University, 2020.) also studied the flow values ​​in each flow channel of the impeller of a water jet propulsion mixed flow pump under partial load conditions and found that there were differences in the flow rates in different impeller flow channels. However, the above studies all used numerical calculations to predict the fluid flow rate in a single flow channel of the impeller of a mixed flow pump, and there have been no reports on the use of experimental methods to measure the fluid flow rate in a single flow channel of the impeller of a mixed flow pump. Therefore, in order to make up for the shortcomings of numerical calculations in predicting the fluid flow rate in a single flow channel of the impeller and verify the accuracy of numerical calculations, it is necessary to design a measurement method or means that can measure the flow rate in a single flow channel of the impeller.

[0003] After searching, there are currently no relevant patent applications and literature involving a single-channel flow measurement method for a mixed-flow pump. Summary of the invention

[0004] In view of the shortcomings in the prior art, the present invention provides a single-channel flow measurement device and a measurement method for a mixed flow pump with a built-in Pitot tube. By arranging multiple groups of Pitot tube flowmeters in different flow channels of the mixed flow pump impeller, the real-time flow rates between different flow channels are measured, the internal flow testing technology of the mixed flow pump under non-design conditions is improved, and a theoretical reference is provided for the smooth operation of the mixed flow pump under off-design conditions.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A single-channel flow measurement device for a mixed-flow pump with a built-in Pitot tube, comprising a plurality of sets of Pitot tube components, an outlet flow measurement unit and a flow data acquisition and correction system;

[0007] A set of Pitot tube assemblies is arranged in each impeller flow channel; each set of Pitot tube assemblies includes a circumferential Pitot tube flowmeter and a radial Pitot tube flowmeter; one end of the circumferential Pitot tube flowmeter is arranged on the suction surface of the blade and extends smoothly along the circumferential direction in the impeller flow channel; one end of the radial Pitot tube flowmeter is arranged on the impeller hub and extends smoothly along the radial direction in the impeller flow channel;

[0008] Each circumferential Pitot tube flowmeter or radial Pitot tube flowmeter corresponds to a pressure equalizing chamber, and the pressure equalizing chamber is divided into two parts by a strain gauge; a plurality of pressure measuring holes are respectively arranged in the upstream direction and the downstream direction of each circumferential Pitot tube flowmeter or radial Pitot tube flowmeter, each pressure measuring hole in the upstream direction is connected to one side of the pressure equalizing chamber through a connecting pipe, and each pressure measuring hole in the downstream direction is connected to the other side of the pressure equalizing chamber through a connecting pipe, and the two parts of the pressure equalizing chamber are used to average the static pressure of the water flow in the upstream direction and the dynamic pressure in the downstream direction of the same circumferential Pitot tube flowmeter or radial Pitot tube flowmeter;

[0009] The outlet flow measurement unit is used to collect the flow at the pump outlet;

[0010] The flow data acquisition and correction system includes a signal transmitting end component and a signal receiving end component. The signal transmitting end component is placed in the wheel hub body and is used to collect the pressure difference data of the strain gauge and transmit the pressure difference data to the signal receiving end component. The signal receiving end component includes a signal receiving component and a computer. The signal receiving component receives the data transmitted by the signal transmitting end component and inputs it into the computer. The computer receives the flow data collected by the outlet flow measurement unit, and realizes the single-channel flow measurement of the mixed flow pump by processing and correcting the pressure difference data and flow data.

[0011] Furthermore, the root of the circumferential Pitot tube flowmeter is arranged in the middle area of ​​the suction surface of the blade; the top of the circumferential Pitot tube flowmeter is fixed to the surface of the pressure surface of the lower blade or does not contact the pressure surface of the lower blade.

[0012] Further, the top of the radial Pitot tube flowmeter does not contact the end wall of the impeller chamber.

[0013] Furthermore, the diameters of the circumferential Pitot tube flowmeter and the radial Pitot tube flowmeter are both smaller than 1 / 10 of the flow channel width, and the diameters of the circumferential Pitot tube flowmeter and the radial Pitot tube flowmeter are both larger than 1 / 30 of the flow channel width.

[0014] Furthermore, on the same circumferential Pitot tube flowmeter or the radial Pitot tube flowmeter, the pressure measuring holes in the upstream direction and the pressure measuring holes in the downstream direction are distributed in pairs, the axis of the pressure measuring holes in the upstream direction is consistent with the mainstream direction at that position, and the axis of the pressure measuring holes in the downstream direction is parallel to the axis of the pressure measuring holes in the upstream direction.

[0015] Furthermore, the pressure equalizing chamber is arranged inside the hub body, and a three-pronged through hole is opened on the hub body above the pressure equalizing chamber, respectively connecting the two parts of the pressure equalizing chamber separated by the strain gauge, and the connecting pipe of the upstream direction pressure measuring hole and the connecting pipe of the rear direction pressure measuring hole on the same circumferential Pitot tube flowmeter or the radial Pitot tube flowmeter are respectively connected to the two parts of the pressure equalizing chamber through the three-pronged through hole.

[0016] Furthermore, the connecting pipe between the pressure measuring hole and the pressure equalizing chamber is a thin hose.

[0017] Furthermore, a cavity is provided inside the hub body for accommodating the pressure equalizing chamber and the signal transmitting end assembly; the pressure equalizing chamber is arranged along the circumferential direction, and a filling block is provided between the pressure equalizing chamber and the signal transmitting end assembly.

[0018] A method for measuring flow rate of a single flow channel of a mixed flow pump comprises the following steps:

[0019] Step 1: Experimentally calibrate the Pitot tube assembly in a single flow channel of the mixed flow pump, and after the calibration is completed, obtain the relationship between the pressure difference parameter and the flow parameter measured by the Pitot tube assembly in each flow channel;

[0020] Step 2: Mark each flow channel of the impeller in turn in the counterclockwise direction; start the mixed flow pump to rotate the impeller, select the flow condition to be measured according to the needs, monitor and record the real-time flow value Q at the outlet t At the same time, record the pressure difference parameters in each flow channel measured by the Pitot tube assembly that change with time t, and use the relationship between the pressure difference parameter and the flow parameter obtained in step 1 to obtain the real-time flow rate in each flow channel of the impeller that changes with time t, recorded as q i ;

[0021] Correct the flow rate in each flow channel of the impeller at the same time to obtain the final flow value q in each flow channel of the impeller i ′, the correction formula is as follows:

[0022]

[0023] Wherein, subscript i represents the i-th impeller flow channel; j ranges from 1 to Z; and Z is the number of flow channels.

[0024] Further, the experimental calibration process is as follows:

[0025] S1, keep the impeller fixed and not rotating, and press the fluid into the mixed flow pump by connecting other power sources at the mixed flow pump inlet and let it flow out from the mixed flow pump outlet; monitor and record the outlet flow value, and control the output power of other power sources to ensure that the flow value is stable at M times the design flow condition (Q d ) n ;

[0026] S2, record the pressure difference parameters of the circumferential Pitot tube flowmeter in a single flow channel of the impeller (ΔP c ) n , and simultaneously record the pressure difference parameters of the radial Pitot tube flowmeter in each flow channel of the mixed flow pump impeller, which are (ΔP r ) n ;

[0027] S3, average the pressure difference parameters measured by the circumferential Pitot tube flowmeter and the radial Pitot tube flowmeter in each flow channel of the impeller, and record it as (ΔP) n =(ΔP c +ΔP r ) / 2;

[0028] S4, the total flow rate of the mixed flow pump is divided by the number of flow channels Z, thereby obtaining a data set of pressure difference parameters and flow parameters in a single flow channel of the impeller, recorded as (ΔP1, (Q d )1 / Z), (ΔP2, (Q d )2 / Z),…,(ΔP n , (Q d ) n / Z);

[0029] S5, ΔP is represented by x, Q is represented by y d / Z, then the data set of the pressure difference parameter and flow parameter in the single flow channel of the impeller is expressed as (x1, y1), (x2, y2), ..., (x n ,y n );

[0030] S6, using the least squares method to calculate the output sensitivity k and the initial zero output value b of the Pitot tube assembly linear equation y=kx+b, and then obtain the relationship between the pressure difference parameter and the flow parameter of the Pitot tube assembly, k and b are expressed as follows:

[0031]

[0032] Where n is the number of trials.

[0033] Beneficial effects of the present invention:

[0034] The present invention discloses a single-channel flow measurement device and method for a mixed flow pump with a built-in Pitot tube. By arranging a Pitot tube assembly inside each impeller channel of the mixed flow pump to measure the flow rate of the fluid passing through a single channel, the test method of the mixed flow pump under partial flow conditions is improved, and a reliable experimental means is provided for deepening the research on rotational stall of the mixed flow pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a general schematic diagram of a single-channel flow measurement device and method for a mixed-flow pump with a built-in Pitot tube according to the present invention.

[0036] Figure 2 This is an enlarged view of the impeller area structure of a mixed flow pump single-channel flow measurement device and method with a built-in Pitot tube as described in the present invention.

[0037] Figure 3 This is a structural schematic diagram of an impeller and a Pitot tube assembly of a single-channel flow measurement device and method for a mixed-flow pump with a built-in Pitot tube as described in the present invention.

[0038] Figure 4 This is a schematic diagram of the relative positions of the impeller blades and the Pitot tube assembly of the mixed flow pump single-channel flow measurement device and method with a built-in Pitot tube described in the present invention.

[0039] Figure 5 This is a schematic diagram of the impeller hub structure of a single-channel flow measurement device and method for a mixed-flow pump with a built-in Pitot tube as described in the present invention.

[0040] Figure 6 A schematic cross-sectional view of an impeller hub shaft of a mixed flow pump single-channel flow measurement device and method with a built-in Pitot tube as described in the present invention.

[0041] Figure 7 This is a schematic diagram of the Blade-to-Blade cross-section of an impeller of a single-channel flow measurement device and method for a mixed-flow pump with a built-in Pitot tube as described in the present invention.

[0042] Figure 8 This is an enlarged view of the structure in the Blade-to-Blade cross section of the impeller of the single-channel flow measurement device and method for a mixed-flow pump with a built-in Pitot tube described in the present invention.

[0043] Fig. 9 This is a schematic diagram of the filling block structure of a mixed flow pump single-channel flow measurement device and method with a built-in Pitot tube as described in the present invention.

[0044] In the figure, 1. hub body, 2. impeller blades, 3. equalizing pressure chamber, 4. filling block, 5. signal transmitting end assembly, 6. guide cone, 7. first through hole, 8. second through hole, 9. strain gauge, 10. sealing ring, 11. threaded matching structure, 12. thin hose, 13. fifth through hole, 14. fourth through hole, 15. circumferential pitot tube flowmeter, 16. radial pitot tube flowmeter, 17. pressure measuring hole, 18. blade inlet, 19. blade top, 20. outlet pipeline, 21. outlet flowmeter, 22. computer, 23. signal receiving assembly, 24. first equalizing pressure chamber, 25. second equalizing pressure chamber, 26. third through hole. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] like Figure 1 and Figure 2 As shown, a single-channel flow measurement device for a mixed flow pump with a built-in Pitot tube includes an impeller, multiple sets of Pitot tube assemblies, an outlet pipeline 20, an outlet flow meter 21, and a flow data acquisition and correction system. A set of Pitot tube assemblies is installed in the middle area of ​​each flow channel of the impeller, the outlet pipeline 20 is installed at the outlet of the mixed flow pump, and the outlet flow meter 21 is located downstream of the outlet pipeline 20. Each set of Pitot tube assemblies includes a circumferential Pitot tube flowmeter 15 and a radial Pitot tube flowmeter 16.

[0047] like Figure 3 and Figure 4 As shown, in a certain flow channel, the root of the circumferential Pitot tube flowmeter 15 is arranged in the middle area of ​​the suction surface of the blade and extends smoothly along the circumferential direction in the impeller flow channel, and the top of the circumferential Pitot tube flowmeter 15 can be fixedly connected to the surface of the pressure surface of the lower blade or be separated from the pressure surface of the lower blade by a certain distance.

[0048] Preferably, the distance between the root of the circumferential Pitot tube flowmeter 15 and the blade inlet end 18 is L1, and L1=(40%-60%)*L1', L1' is the length from the blade inlet edge to the outlet edge (the root position of the circumferential Pitot tube flowmeter 15); the distance between the root of the circumferential Pitot tube flowmeter 15 and the blade top 19 is L2, and L2=(40%-60%)*L2', L2' is the radial height of the blade.

[0049] Preferably, when the circumferential Pitot tube flowmeter 15 extends in the circumferential direction, the position regularity of each axial cross section thereof is the same as that of its root.

[0050] Preferably, the distance between the top of the circumferential Pitot tube flowmeter 15 and the pressure surface of the lower blade is less than 5 mm.

[0051] like Figure 3 , Figure 7 and Figure 8 As shown, the root of the radial Pitot tube flowmeter 16 is arranged on the impeller hub in the middle of the impeller flow channel, and extends smoothly along the radial direction in the impeller flow channel. The top of the radial Pitot tube flowmeter 16 is a distance away from the end wall of the impeller chamber.

[0052] Preferably, the distance between the root of the radial Pitot tube flowmeter 16 and the axial section where the blade inlet end 18 is located (the axial section is selected at the contact point between the blade inlet end 18 and the hub) is L3, and L3=(40%-60%)*L3', L3' is the flow channel length; the distance between the root of the radial Pitot tube flowmeter 16 and the adjacent two-stage blades is the same.

[0053] Preferably, when the radial Pitot tube flowmeter 16 extends in the radial direction, the position regularity of each axial cross section thereof is the same as that of its root.

[0054] Preferably, the distance between the top of the radial Pitot tube flowmeter 16 and the end wall of the impeller chamber is less than 5 mm.

[0055] The measuring direction of the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 changes according to the width and height of the flow channel. When the flow channel is long, the flowmeter can be arranged along the curvature of the flow channel in the flow channel; if the flow channel is short, the flowmeter can be arranged in a straight line or in a long strip without curvature in the flow channel. The diameter of the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 are both less than 1 / 10 of the flow channel width, but in order to ensure the strength of the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 when the fluid passes through, the diameter of the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 are both greater than 1 / 30 of the flow channel width. At the same time, the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 need to be staggered by a certain distance in the flow channel space. The staggered distance between the two is at least 2% of the impeller flow channel length in the mainstream direction, but the staggered distance must also be greater than 2 times the diameter of the circumferential Pitot tube flowmeter 15 or the radial Pitot tube flowmeter 16.

[0056] like Figure 7 and Figure 8As shown, a plurality of pressure measuring holes 17 are arranged on the cylindrical surface of the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16, and are evenly distributed at equal intervals from the root to the top of the circumferential Pitot tube flowmeter 15 (or the radial Pitot tube flowmeter 16). More specifically, the pressure measuring holes 17 are respectively arranged in the upstream direction and the downstream direction of the circumferential Pitot tube flowmeter 15 (or the radial Pitot tube flowmeter 16); the pressure measuring holes 17 in the upstream direction and the pressure measuring holes 17 in the downstream direction are arranged in pairs, and the axis of the pressure measuring hole 17 in the upstream direction is consistent with the mainstream direction at this position, and at the same time, the axis of the corresponding pressure measuring hole 17 in the downstream direction is parallel to the axis of the pressure measuring hole 17 in the upstream direction. A partition is arranged axially inside the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 to separate the upstream direction from the downstream direction.

[0057] like Figure 5 and Figure 6 As shown, each circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 are equipped with an equalizing pressure chamber, which is arranged inside the hub body 1. The equalizing pressure chamber is divided into a first equalizing pressure chamber 24 and a second equalizing pressure chamber 25 by strain gauges 9 arranged radially; the hub body 1 is provided with a bifurcated through hole corresponding to the first equalizing pressure chamber 24 and the second equalizing pressure chamber 25, one of which extends to the outside of the hub body 1, and the other two through holes are connected to the first equalizing pressure chamber 24 and the second equalizing pressure chamber 25 respectively. For the convenience of description, the bifurcated through hole corresponding to the circumferential Pitot tube flowmeter 15 is referred to as the first through hole 7, and the three-forked through hole corresponding to the radial Pitot tube flowmeter 16 is referred to as the second through hole 8. More specifically, the upper end of the first through hole 7 extends all the way to the impeller blade 2, corresponding to the root of the circumferential Pitot tube flowmeter 15; the second through hole 8 corresponds to the root of the radial Pitot tube flowmeter 16. A plurality of thin hoses 12 are arranged inside the same circumferential Pitot tube flowmeter 15 or radial Pitot tube flowmeter (16), one end of each thin hose 12 is connected to a pressure measuring hole 17, and the other end is connected to an equalizing pressure chamber. More specifically, in each Pitot tube flowmeter, the pressure measuring hole 17 in the upstream direction is connected to the first equalizing pressure chamber 24 through the thin hose 12, and the pressure measuring hole 17 in the downstream direction is connected to the second equalizing pressure chamber 25 through the thin hose 12. The thin hose 12 inside the circumferential Pitot tube flowmeter 15 passes through the blade 2 and the first through hole 7 in sequence, and then is connected to the first equalizing pressure chamber 24 and the second equalizing pressure chamber 25 respectively. The thin hose 12 inside the radial Pitot tube flowmeter 16 passes through the second through hole 8, and then is connected to the first equalizing pressure chamber 24 and the second equalizing pressure chamber 25 respectively. In the present application, the first equalizing pressure chamber 24 is used to average the static pressure of the water flow in the upstream direction, and the second equalizing pressure chamber 25 is used to average the dynamic pressure in the downstream direction. Since the strain gauge 9 is provided between the first equalizing pressure chamber 24 and the second equalizing pressure chamber 25 , the difference between the total pressure and the static pressure of the fluid in the impeller flow channel can be measured.

[0058] like Figure 1 , Figure 6 and Fig. 9 As shown, the flow data acquisition and correction system includes a signal transmitting end component 5 and a signal receiving end component. The signal transmitting end component includes the strain gauge 9, a data acquisition storage and transmission device and a power supply system. The data acquisition storage and transmission device is mainly used to receive the pressure difference data transmitted by the strain gauge 9, and then transmit the flow data to the signal receiving end component through a wireless signal transmitting device; the power supply system supplies power to each power unit through a power line. The signal transmitting end component 5 needs to be fixed at the center position in the impeller hub cavity, and its shape is an oblate cylinder. The impeller hub includes a hub body 1 and a guide cone 6, wherein a cavity is opened inside the hub body 1 for placing the first equalizing chamber 24, the second equalizing chamber 25 and the signal transmitting end component 5. The guide cone 6 is used to seal the internal cavity of the hub body 1, and the guide cone 6 and the hub body 1 are connected by a threaded matching structure 11, and a sealing ring 10 is provided between the guide cone 6 and the hub body 1. A filling block 4 is provided between the signal transmitting end assembly 5 and the first equalizing pressure chamber 24 and the second equalizing pressure chamber 25. Fig. 9 A third through hole 26 is provided in the center of the filling block 4 for installing the signal line and the power line. The impeller on which the signal transmitting end assembly 5 is installed needs to be dynamically balanced before the mixed flow pump is operated.

[0059] The signal receiving end component includes a signal receiving component 23 and a computer 22, which are used to receive the flow data of the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 in each flow channel of the impeller and transmit them to the computer 22. The signal receiving end component also collects the outlet flowmeter 21 set at the outlet of the mixed flow pump, and transmits the flow data of the outlet of the mixed flow pump to the computer 22 for correcting the flow data in a single flow channel of the impeller. A fourth through hole 14 is opened in the middle of the guide cone 6, and a fifth through hole 13 is opened on the end wall of the runner chamber for the passage of wireless signals. The fourth through hole 14 and the fifth through hole 13 are both filled with wireless signal friendly materials to prevent fluid passage and fluid leakage.

[0060] With respect to the above-mentioned mixed flow pump single-channel flow measurement device with a built-in Pitot tube, the present invention also proposes a mixed flow pump single-channel flow measurement method, which is specifically implemented by the following steps:

[0061] Step 1: Since the original data transmitted by the Pitot tube assembly is differential pressure data, it is necessary to convert the differential pressure data into flow data and calibrate the measurement range of the Pitot tube assembly in each flow channel of the impeller. Since the impeller of the mixed flow pump has a circumferentially symmetrical structure, it is only necessary to calibrate the Pitot tube assembly of one of the flow channels. The calibration method is as follows:

[0062] First, the impeller is kept fixed and does not rotate. The fluid is pressed into the mixed flow pump by connecting other power sources to the mixed flow pump inlet and flows out from the mixed flow pump outlet. The fluid flows through the outlet pipeline 20 and the outlet flow meter 21 in sequence. The computer 22 is used to monitor and record the flow value of the outlet flow meter 21, and the output power of other power sources is controlled to ensure that the flow value is stable at M times the design flow condition (Q d ) n (where M = 0.1 × n, n = 1 to 16). Next, the pressure difference parameters of the circumferential Pitot tube flowmeter 15 in each flow channel of the impeller are recorded as (ΔP c ) n , and simultaneously record the pressure difference parameters of the radial Pitot tube flowmeter 16 in each flow channel of the mixed flow pump impeller, which are (ΔP r ) n The pressure difference data measured by the circumferential Pitot tube flowmeter 15 and the radial Pitot tube flowmeter 16 in each flow channel of the impeller are averaged and recorded as (ΔP) n =(ΔP c +ΔP r ) / 2. Divide the total flow rate of the mixed flow pump by the number of channels Z, and you can get the data set of pressure difference data and flow parameters in a single channel of the impeller (ΔP1, (Q d )1 / Z), (ΔP2, (Q d )2 / Z),…,(ΔP n , (Q d ) n / Z). ΔP is represented by x and Q is represented by y d / Z, then this series of data can be expressed as (x1, y1), (x2, y2), ..., (x n ,y n ). The output sensitivity k and the initial zero point output value b of the Pitot tube assembly linear equation y=kx+b are calculated using the least squares method. The main formula is shown in (Equation 1)

[0063]

[0064] In the formula, ∑x i =x1+x2+···+x n ;

[0065] ∑y i =y1+y2+···+y n ;

[0066] ∑x i y i =x1y1+x2y2+···+x n y n ;

[0067]

[0068] n is the number of trials.

[0069] ΔP and Q d By substituting / Z back into equation 1, the relationship between the pressure difference parameter and the flow parameter in a single flow channel can be obtained.

[0070] Step 2: After obtaining the relationship between the pressure difference parameter and the flow parameter measured by the Pitot tube assembly in each flow channel, the flow rate through each impeller flow channel of the mixed flow pump can be formally measured. First, mark the flow channels of the impeller in the counterclockwise direction as the 1st flow channel, the 2nd flow channel, ..., the Zth flow channel (where Z is the number of flow channels). Start the mixed flow pump to rotate the impeller, select the flow condition to be measured as needed, and use the computer 22 to monitor and record the real-time flow value Q of the outlet flow meter changing with time t. t At the same time, record the pressure difference parameters in each flow channel measured by the Pitot tube assembly that change with time t, and use the relationship between the pressure difference parameter and the flow parameter obtained in step 1 to obtain the real-time flow rate in each flow channel of the impeller that changes with time t, which are recorded as q1, q2, ..., q Z (where Z is the number of flow channels).

[0071] The computer 22 is used to correct the flow rate in each flow channel of the impeller at the same time to obtain the final flow rate value q in each flow channel of the impeller. i ′. The correction formula is shown in Formula 2

[0072]

[0073] In the formula, the subscript i represents the i-th impeller flow channel; j takes a value from 1 to Z; Z is the number of flow channels, and in this embodiment, Z is 4.

[0074] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A single-channel flow measurement device for a mixed-flow pump with a built-in Pitot tube. It is characterized in that Includes multiple sets of Pitot tube components, outlet flow measurement units and flow data acquisition and correction systems; A set of Pitot tube assemblies is arranged in each impeller flow channel; each set of Pitot tube assemblies comprises a circumferential Pitot tube flowmeter (15) and a radial Pitot tube flowmeter (16); one end of the circumferential Pitot tube flowmeter (15) is arranged on the suction surface of the blade and smoothly extends along the circumferential direction in the impeller flow channel; one end of the radial Pitot tube flowmeter (16) is arranged on the impeller hub and smoothly extends along the radial direction in the impeller flow channel; Each circumferential Pitot tube flowmeter (15) or radial Pitot tube flowmeter (16) corresponds to a pressure equalizing chamber, and the pressure equalizing chamber is divided into two parts by a strain gauge (9); a plurality of pressure measuring holes (17) are respectively arranged in the upstream direction and the downstream direction of each circumferential Pitot tube flowmeter (15) or radial Pitot tube flowmeter (16); each pressure measuring hole in the upstream direction is connected to one side of the pressure equalizing chamber through a connecting pipe, and each pressure measuring hole in the downstream direction is connected to the other side of the pressure equalizing chamber through a connecting pipe; the two parts of the pressure equalizing chamber are used to average the static pressure of the water flow in the upstream direction and the dynamic pressure in the downstream direction of the same circumferential Pitot tube flowmeter (15) or radial Pitot tube flowmeter (16); The outlet flow measurement unit is used to collect the flow at the pump outlet; The flow data acquisition and correction system comprises a signal transmitting end component (5) and a signal receiving end component. The signal transmitting end component (5) is placed in the wheel hub body (1) and is used to collect pressure difference data of the strain gauge (9) and transmit the pressure difference data to the signal receiving end component. The signal receiving end component comprises a signal receiving component (23) and a computer (22). The signal receiving component (23) receives the data transmitted by the signal transmitting end component (5) and inputs the data into the computer (22). The computer (22) receives the flow data collected by the outlet flow measurement unit. By processing and correcting the pressure difference data and the flow data, the single-channel flow measurement of the mixed flow pump is realized.

2. A mixed flow pump single-channel flow measurement device with a built-in Pitot tube according to claim 1, It is characterized in that The root of the circumferential Pitot tube flowmeter is arranged in the middle area of ​​the suction surface of the blade; the top of the circumferential Pitot tube flowmeter is fixed to the surface of the pressure surface of the lower blade or does not contact the pressure surface of the lower blade.

3. A mixed flow pump single-channel flow measurement device with a built-in Pitot tube according to claim 1, It is characterized in that The top of the radial Pitot tube flowmeter does not contact the end wall of the runner chamber.

4. A mixed flow pump single-channel flow measurement device with a built-in Pitot tube according to claim 1, 2 or 3, It is characterized in that The diameters of the circumferential Pitot tube flowmeter (15) and the radial Pitot tube flowmeter (16) are both smaller than 1 / 10 of the width of the flow channel, and the diameters of the circumferential Pitot tube flowmeter (15) and the radial Pitot tube flowmeter (16) are both larger than 1 / 30 of the width of the flow channel.

5. The single-channel flow measurement device for a mixed-flow pump with a built-in Pitot tube according to claim 1, It is characterized in that On the same circumferential Pitot tube flowmeter (15) or the radial Pitot tube flowmeter (16), the pressure measuring holes (17) in the upstream direction and the pressure measuring holes (17) in the downstream direction are arranged in pairs, the axis of the pressure measuring holes (17) in the upstream direction is consistent with the mainstream direction at that position, and the axis of the pressure measuring holes (17) in the downstream direction is parallel to the axis of the pressure measuring holes (17) in the upstream direction.

6. A mixed flow pump single-channel flow measurement device with a built-in Pitot tube according to claim 5, It is characterized in that The pressure equalizing chamber is arranged inside the hub body (1), and a three-pronged through hole is opened on the hub body (1) at the upper part of the pressure equalizing chamber, respectively connecting the two parts of the pressure equalizing chamber separated by the strain gauge (9), and the connecting pipe of the upstream pressure measuring hole (17) and the connecting pipe of the downstream pressure measuring hole (17) on the same circumferential Pitot tube flowmeter (15) or the radial Pitot tube flowmeter (16) are respectively connected to the two parts of the pressure equalizing chamber through the three-pronged through hole.

7. A mixed flow pump single-channel flow measurement device with a built-in Pitot tube according to claim 6, It is characterized in that The connecting pipe between the pressure measuring hole (17) and the pressure equalizing chamber is a thin hose (12).

8. The single-channel flow measurement device for a mixed-flow pump with a built-in Pitot tube according to claim 1, It is characterized in that The hub body (1) has a cavity inside for accommodating the pressure equalizing chamber and the signal transmitting end assembly (5); the pressure equalizing chamber is arranged along the circumferential direction, and a filling block (4) is provided between the pressure equalizing chamber and the signal transmitting end assembly.

9. A method for measuring flow rate of a single flow channel of a mixed flow pump. It is characterized in that Based on the mixed flow pump single-channel flow measurement device with a built-in Pitot tube as described in claim 1, the measurement method comprises the following steps: Step 1: Experimentally calibrate the Pitot tube assembly in a single flow channel of the mixed flow pump, and after the calibration is completed, obtain the relationship between the pressure difference parameter and the flow parameter measured by the Pitot tube assembly in each flow channel; Step 2: Mark each flow channel of the impeller in turn in the counterclockwise direction; start the mixed flow pump to rotate the impeller, select the flow condition to be measured according to the needs, monitor and record the real-time flow value Q at the outlet t At the same time, record the pressure difference parameters in each flow channel measured by the Pitot tube assembly that change with time t, and use the relationship between the pressure difference parameter and the flow parameter obtained in step 1 to obtain the real-time flow rate in each flow channel of the impeller that changes with time t, recorded as q i ; Correct the flow rate in each flow channel of the impeller at the same time to obtain the final flow value q in each flow channel of the impeller i ′, the correction formula is as follows: Wherein, subscript i represents the i-th impeller flow channel; j ranges from 1 to Z; and Z is the number of flow channels.

10. A mixed flow pump single-channel flow measurement method according to claim 9, It is characterized in that The experimental calibration process is as follows: S1, keep the impeller fixed and not rotating, and press the fluid into the mixed flow pump by connecting other power sources at the mixed flow pump inlet and let it flow out from the mixed flow pump outlet; monitor and record the outlet flow value, and control the output power of other power sources to ensure that the flow value is stable at M times the design flow condition (Q d ) n ; S2, record the pressure difference parameters of the circumferential Pitot tube flowmeter (15) in a single flow channel of the impeller (ΔP c ) n , and simultaneously record the pressure difference parameters of the radial Pitot tube flowmeter (16) in each flow channel of the mixed flow pump impeller, which are (ΔP r ) n ; S3, the pressure difference parameters measured by the circumferential Pitot tube flowmeter (15) and the radial Pitot tube flowmeter (16) in each flow channel of the impeller are averaged and recorded as ΔP n =((ΔP c ) n +(ΔP r ) n ) / 2; S4, the total flow rate of the mixed flow pump is divided by the number of flow channels Z, thereby obtaining a data set of pressure difference parameters and flow parameters in a single flow channel of the impeller, recorded as (ΔP 1 , (Q d ) 1 / Z), (ΔP 2 , (Q d ) 2 / Z),…,(ΔP n , (Q d ) n / Z); S5, ΔP is represented by x, Q is represented by y d / Z, then the data set of the pressure difference parameter and flow parameter in the single flow channel of the impeller is expressed as (x 1 ,y 1 ), (x 2 ,y 2 ),…,(x n ,y n ); S6, using the least squares method to calculate the output sensitivity k and the initial zero point output value b of the Pitot tube assembly linear equation y=kx+b; expressed as follows: Where n is the number of trials.

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