Calibration Method and System for Measuring Flow by Differential Pressure Method of Turbine Volute

Abstract

The present invention relates to a calibration method and system for measuring flow by differential pressure in a turbine volute, which comprises the following steps; Step 1, arranging a measurement assembly; First, based on the volute of the turbine, there is a straight-section flow channel upstream of the volute. In the straight-section flow channel, a plurality of sound channels are arranged in parallel according to the channel height, and ultrasonic transducers are arranged.

Description

Technical Field

[0001] The present invention relates to a calibration method and system for measuring flow by differential pressure in a turbine volute, and relates to the technical field of measuring the water flow rate through a turbine volute. Background Art

[0002] The efficiency test of a water turbine is an important link in the operation and management of a hydropower station, which is of great significance for ensuring the safe, stable and efficient operation of the water turbine. Its main purpose is to evaluate the performance and efficiency of the water turbine to determine whether it meets the design requirements and actual operation needs. The measurement of water flow rate is indispensable in the process of water turbine efficiency test. The more accurate the flow rate measurement is, the more accurate the calculation of water turbine efficiency will be.

[0003] Currently, the main methods for measuring the water turbine flow rate are: the differential pressure flow measurement method in the volute (Winter-Kennedy method): Although its installation and implementation are relatively simple, it can obtain high measurement accuracy after calibration according to the absolute flow rate, has a long working life, and simple on-line maintenance. Disadvantages: It is necessary to calibrate according to the flow rate calibration coefficient. Since the absolute flow rate calibration is obtained under ideal conditions before leaving the factory, the coefficient cannot truly and accurately represent the actual coefficient, resulting in the inability to avoid measurement errors. Those skilled in the art do not have the idea of correcting the coefficient based on the actual working state. When wear, deformation and inclusion occur, the previous coefficient is still used for calculation, resulting in errors in flow rate calculation and inability to achieve real-time adjustment. Although the ultrasonic flow measurement method has high measurement accuracy and can be measured in real time on-line, its installation is relatively complex, the equipment life is relatively short, and it is difficult to repair the underwater equipment after damage. Summary of the Invention

[0004] Generally speaking, the technical problem to be solved by the present invention is to provide a calibration method and system for measuring flow by differential pressure in a turbine volute, aiming to provide an integrated method using two flow measurement methods, and automatically and real-time calibrate the differential pressure flow measurement according to the accuracy of the ultrasonic flow measurement method, improve the flow measurement accuracy, extend the operation life of the flow measurement device, and at the same time, realize the early warning of differential pressure method faults. Even if the underwater equipment of the ultrasonic flow measurement device is damaged, the differential pressure flow measurement device calibrated by coefficient correction can still ensure the flow measurement accuracy. When an error occurs in the differential pressure method of the volute, it can be corrected in time through the ultrasonic method.

[0005] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0006] In order to achieve accurate calibration, a calibration method for measuring flow by differential pressure in a turbine volute includes the following steps; Step 1, arrange the measurement components; First, based on the volute of the water turbine, there is a straight section flow channel upstream of the volute. In the straight section flow channel, a plurality of sound channels are arranged in parallel according to the sound channel height, and ultrasonic transducers are arranged.

[0007] Then, based on the volute differential pressure flow measurement method, the flow rate Q is obtained

[0008] , formula (1);

[0009] Among them, , is the pressure sensor installed on the inner and outer circular tube walls of the volute, used to measure the differential pressure between the high and low pressure sides of the pressure measuring tubes. k and n are the Winter-Kennedy coefficients;

[0010] Secondly, based on the ultrasonic flow measurement method, the flow rate Q is obtained;

[0011] , formula (2);

[0012] In the formula, is the radius of the flow channel cross-section, is the number of sound channels, is the integral weight coefficient, is the sound channel flow velocity;

[0013] Thirdly, obtain the flow rates obtained by the i-group ultrasonic flow measurement method, and at the same time obtain the volute differential pressure , and calibrate the k and n coefficients in formula (1);

[0014] Step 2, first, take the logarithm of both sides of formula (1) to get:

[0015] , formula (3);

[0016] Let , , and transform formula (3) into a linear function , formula (4);

[0017] After that, for the flow rates obtained by the multi-group ultrasonic flow measurement method, take the natural logarithm ; and for the multi-group pressure difference values corresponding to the flow rate , take the natural logarithm , formula (5); where is the measurement sequence number of the measured value;

[0018] In formula (4), among them, 、 are undetermined constants, and obtain the point ;

[0019] After that, assume a straight line through the point ; set the straight line , deviation , formula (6), formula (6) expresses The corresponding value on the straight line With actual value The smaller the deviation, the smaller the point The closer it is to the assumed straight line, the to measure the total deviation;

[0020] Then, the constructor:

[0021] , formula (7);

[0022] When formula (7) takes the minimum value, the obtained and That is the solution sought;

[0023] Then, according to the extreme value principle:

[0024] ,Right now , Formula (8);

[0025] Solving the equations together we get:

[0026] Formula (9);

[0027] Obtain Formula (10);

[0028] The obtained values ​​of k and n are the exact values ​​of the Winter-Kennedy coefficients in formula (1);

[0029] Among them, at point Assuming that in the straight line step, based on the linear regression process, with the help of coefficients

[0030] Formula (11);

[0031] The correlation coefficient is calculated based on the product difference method. The closer to 1 the better.

[0032] In order to realize long-term automatic self-monitoring, a method for measuring flow of a turbine volute is provided, wherein an ultrasonic transducer and a pressure sensor are installed on the turbine, and the ultrasonic transducer and the pressure sensor are electrically connected to a host computer;

[0033] The measurement method includes the following steps:

[0034] Step A, starting the pressure sensor to measure flow based on the volute pressure difference, and starting the ultrasonic transducer to measure flow based on the ultrasonic flow measurement method;

[0035] Step B, executing the above calibration method to correct the coefficient of the volute pressure difference flow measurement;

[0036] Step C: Perform real-time flow measurement using the volute differential pressure flow measurement method with the corrected coefficient.

[0037] Step D: Regularly turn on the ultrasonic transducer to detect and compare whether the flow rate measured by the volute differential pressure flow measurement method is correct, so as to determine whether there are equipment failures or wear.

[0038] Step E: After replacing the faulty or worn equipment, repeat Steps B and C.

[0039] As a further improvement of the above technical solution:

[0040] Since the replacement or repair of the water turbine involves a large amount of work, in order to further verify whether there are faults and avoid false alarms, when there are several water turbines in particular, when it is determined that there are equipment failures or wear, start one of the following strategies;

[0041] Strategy 1: Introduce an expected standard amount of water flow into the water turbine, start the ultrasonic flow measurement method to calibrate whether there are equipment failures or wear of the ultrasonic transducer and / or start the volute differential pressure flow measurement method for secondary verification;

[0042] Strategy 2: Start the ultrasonic transducers of adjacent water turbines for comparison and calibration.

[0043] The occurrence of probe failures is generally caused by water flow impact, especially when the debris mixed in the water flow impacts at high speed, resulting in probe damage. Therefore, in order to further ensure the accuracy and long-term performance of calibration from a hardware perspective, the ultrasonic transducer is equipped with a protective hood.

[0044] When the ultrasonic transducer is started, open the protective hood of the ultrasonic transducer;

[0045] When the ultrasonic transducer is turned off, close the protective hood of the ultrasonic transducer.

[0046] The protective hood includes a push rod base provided on the guide housing and a sliding sleeve connected to the push rod base through a polished rod sleeve and sleeved on the guide housing;

[0047] A number of swing bent arms are hinged at the end of the guide housing; there is a petal guard plate on one side arm of the swing bent arm;

[0048] An articulated sliding seat slides in the radial channel on the other side arm of the swing bent arm;

[0049] There is a petal gap between adjacent petal guard plates;

[0050] The sliding sleeve is hinged to the articulated sliding seat through a traction rod;

[0051] When the hood needs to be actuated for protection, the push rod base drives the sliding sleeve to move through the polished rod sleeve, causing the traction rod to pull the articulated sliding seat, making the swing bent arm swing, thereby driving the petal guard plate to open and close.

[0052] To match the above method, a flow measurement system for a water turbine volute includes ultrasonic transducers and pressure sensors installed on the water turbine. The ultrasonic transducers and pressure sensors are electrically connected to a host computer, which is used to match the above calibration method.

[0053] As a basic installation requirement, the ultrasonic transducer includes a transducer probe. The transducer probe is installed and inserted into the inner cavity of the straight section flow channel. The protective hood is installed on the guiding housing and used to cover the transducer probe to avoid the influence of pipe wall vibration.

[0054] As a further improvement of the above technical solution: for better protection, an elastic net is connected between the petal guard plates.

[0055] To better overcome the respective disadvantages of the volute differential pressure method for flow measurement and the ultrasonic method for flow measurement, this invention patent adopts a combined integrated flow measurement scheme of the two. It uses the ultrasonic flow measurement method to calibrate the coefficient in the formula of the volute differential pressure method for flow measurement, solves the problem of calibrating the volute flow measurement coefficient, and improves the accuracy of the volute differential pressure method for flow measurement equipment. Through the ingenious combination of the two, real-time online measurement of the volute differential pressure method for flow measurement is achieved, and regular calibration is carried out through the ultrasonic method for flow measurement. When measurement errors occur, a detection method without disassembly and without stopping the machine is further provided. Furthermore, to ensure the normal operation of the water turbine and the reliability of regular calibration, a protective hood is added, thus ensuring the verification of the coefficient of the volute differential pressure method for flow measurement to the greatest extent and ensuring the non-stop monitoring of water turbine failures.

[0056] The design of the present invention is reasonable, with low cost, strong and durable, safe and reliable, simple to operate, time-saving and labor-saving, cost-saving, compact in structure and convenient to use. Description of the Drawings

[0057] Figure 1 It is a schematic structural diagram of the existing volute differential pressure flow measurement method of the present invention.

[0058] Figure 2 It is a schematic structural diagram of the ultrasonic flow measurement method of the present invention.

[0059] Figure 3 It is a simple schematic diagram of the present invention.

[0060] Figure 4 It is a schematic diagram of the improvement of the transducer of the present invention.

[0061] Figure 5 It is a schematic diagram of the internal structure of the transducer head of the present invention.

[0062] Wherein: 1. Water gate; 2. Ultrasonic transducer; 3. Pressure sensor; 4. Volute; 5. Straight-section flow channel; 6. Transducer probe; 7. Guide housing; 8. Push rod base; 9. Slide sleeve; 10. Traction rod; 11. Hinged slide seat; 12. Swing bent arm; 13. Petal guard plate; 14. Petal gap. Detailed implementation manners

[0063] See Figure 1 , the existing differential pressure flow measurement method for volute (Winter-Kennedy method): It uses the pressure difference between the high-pressure side and the low-pressure side between the pressure measuring tubes installed on the inner and outer circular tube walls of the volute to measure. When the water turbine is running, there is a certain mathematical relationship between the pressure difference flow of its volute, and the empirical formula of the flow rate,

[0064] , formula (1);

[0065] Among them, k and n are Winter-Kennedy coefficients. n is about 0.5. The values of n and k are generally determined according to the model experiment of the water turbine in the laboratory or the computational fluid simulation (CFD) method. The accurate values of the coefficients determine the accuracy of the flow rate. Since the values of n and k are different from the true values of the on-site conditions and are simulation values under non-actual working conditions, the corresponding flow rate values are only a reference value under the on-site actual working conditions. The model experiment is used to trim and reverse-calculate the coefficients, which has an error with the site. When the volute is repaired, worn, or there are inclusions, it cannot be corrected. The specific implementation method is to measure the pressure difference between the pressure measuring tubes installed on the inner and outer circular tube walls of the volute, and obtain the flow rate according to the corresponding relationship between the pressure difference and the flow rate.

[0066] The ultrasonic flow measurement method is to arrange several sound channels in parallel at different sound channel heights in the straight-section flow channel upstream of the volute, such as Figure 2 shown. The axial flow velocity of each sound channel represents the average flow velocity within a certain area above and below it. The axial velocities of multiple sound channels are used to better estimate the cross-sectional average flow velocity of the flow channel, and then the flow rate is obtained by integrating through the velocity-area method. The probe is worn, damaged, and has time drift. Among them, Figure 1 is the illustration of the existing equipment, Figure 2 is the layout drawing. These two drawings are only for reference, and their presence or absence does not affect the protection scope of the present invention.

[0067] , formula (2);

[0068] In the formula, is the radius of the flow channel cross-section, is the number of sound channels, is the integration weight coefficient, is the sound channel flow velocity.

[0069] Obtain the flow rates obtained by multiple ultrasonic flow measurement methods and simultaneously obtain the differential pressure of the volute to accurately calibrate the k and n coefficients in .

[0070] Among them, taking the logarithm of both sides of the formula is:

[0071] , formula (3);

[0072] Let , , and can be transformed into a linear function , formula (4);

[0073] For the multiple flow rates obtained by the ultrasonic flow measurement method , take their natural logarithms ; for the multiple differential pressure values corresponding to the flow rate , take their natural logarithms , formula (5);

[0074] Among them is the measurement order number of the measured value

[0075] Regarding the function , among which and are undetermined constants. Generally speaking these points are not necessarily exactly on the same straight line. Assume there is a straight line , and the deviation , formula (6); which expresses the value on the corresponding straight line and the actual value The smaller the deviation, the closer the point is to the assumed straight line

[0076] Use to measure the total deviation and construct the function:

[0077] , formula (7);

[0078] When this function takes the minimum value, the obtained and are the solutions

[0079] According to the extreme value principle, we can get:

[0080] , that is , formula (8);

[0081] The equations are combined to get:

[0082] Formula (9);

[0083] Further seek Formula (10);

[0084] The obtained k and n values ​​are the formula The exact value of the Winter-Kennedy coefficient in .

[0085] In the linear regression process, it is impossible for the fitted straight line to pass through all the regression data points. In order to judge the quality of the correlation, we can use the correlation coefficient Formula (11);

[0086] It is a common form of calculating the correlation coefficient based on the product difference method. The closer it is to 1, the better. In the present invention, the coefficient of determination is used To determine the availability of the Winter-Kennedy coefficient, we need .

[0087] The above coefficient correction method ensures the accuracy of flow measurement under field conditions using the volute pressure difference method.

[0088] Application implementation case:

[0089] like Figures 1-3 The formula for calculating flow rate using the volute pressure difference method is: , taking the logarithm of both sides of the formula is: ,make , , you can Transformed into a linear function , the flow measurement scheme is enabled to obtain the flow rate obtained by multiple sets of ultrasonic flow measurement methods , and take the natural logarithm ; Record the volute pressure difference method and flow rate Corresponding multiple sets of pressure difference values , taking its natural logarithm ,in is the measurement order number of the measured value. To ensure sufficient accuracy, the value should be greater than 1000.

[0090] About Functions ,in and is a constant to be determined. Generally speaking, These points are not necessarily completely on the same straight line. Assume there is a straight line , deviation , which represents the value on the corresponding straight line and the actual value The smaller the deviation, the closer the point is to the assumed straight line.

[0091] Use to measure the total deviation and construct the function: , when this function takes the minimum value, the obtained and are the solutions.

[0092] According to the extreme value principle, we can get:

[0093] ,

[0094] That is , ;

[0095] By solving the equations simultaneously, we get:

[0096] ;

[0097] Further, we obtain ;

[0098] , which is the corrected Winter-Kennedy coefficient.

[0099] To illustrate , the calculation process of , take 5 for example using the data in Table 1. To simplify the problem,

[0100] Table 1: Data for correcting the Winter-Kennedy coefficient

[0101]

[0102] According to the above formula, the correction coefficient is:

[0103] , .

[0104] As an extended protection, as a protection for the flow measurement method based on the calibration method, as Figures 1-5 shown, for the flow measurement method of the turbine volute in this embodiment, an ultrasonic transducer 2 and a pressure sensor 3 are installed on the turbine, and the ultrasonic transducer 2 and the pressure sensor 3 are electrically connected to conventional components such as a host computer.

[0105] AsFigures 1-5 , in order to achieve better monitoring of the water turbine, the measurement method includes the following steps;

[0106] Step A: Start the pressure sensor 3 to measure the flow based on the differential pressure in the volute, and start the ultrasonic transducer 2 to measure the flow based on the ultrasonic flow measurement method, so as to collect two sets of data.

[0107] Step B: Execute the above calibration method to correct the coefficient of the flow measurement based on the differential pressure in the volute; since the differential pressure method in the volute is convenient and practical, turn off the ultrasonic and do not use it as the main measurement, but use it as a backup, and it can be corrected through the ultrasonic probe.

[0108] Step C: Use the flow measurement method based on the differential pressure in the volute after correction to perform real-time flow measurement; achieve continuous testing and save costs;

[0109] However, during the use process, the equipment will inevitably be worn and damaged. Therefore, execute Step D: Regularly turn on the ultrasonic transducer 2 to detect and compare whether the flow rate measured by the differential pressure method in the volute is correct, so as to determine whether there is equipment failure or wear; thus, it is possible to achieve non-disassembly and non-stop detection, greatly reducing costs.

[0110] Step E: After replacing the faulty or worn equipment, repeat Steps B and C.

[0111] However, theoretically speaking, it is impossible to ensure that the turned-on ultrasonic is definitely free of faults or errors, because the ultrasonic probe is generally either intact or faulty, resulting in large measurement errors. Moreover, the pipeline can have angular or positional changes. The applicant can achieve approximate detection through the side-by-side water turbines. Of course, the pipeline can be equipped with a level gauge for detection and correction of the inclination angle, thereby reducing the difficulty of ultrasonic maintenance. When there are several water turbines and it is determined that there is equipment failure or wear, start one of the following strategies for verification;

[0112] Strategy 1: Pass an expected standard amount of water flow into the water turbine, start the ultrasonic flow measurement method to calibrate whether there is equipment failure or wear in the ultrasonic transducer 2 and / or start the differential pressure measurement method in the volute for secondary verification; this is a theoretical protection and is difficult to implement in practice because it is difficult to actually control the expected standard water volume. However, if it can be achieved, the verification accuracy can be improved.

[0113] Strategy 2: Start the ultrasonic transducer 2 of the adjacent water turbine for comparison and verification. This is relatively convenient for actual operation. However, there are errors and it is suitable for large rivers and large flows.

[0114] In order to further ensure the convenience and accuracy of calibration, as a hardware improvement, the ultrasonic transducer 2 is equipped with a protective hood; the inventor found that one of the problems leading to a high failure rate of ultrasonic flow measurement is that due to the high-speed flowing particulate matter in the flow channel, it will collide with the probe, resulting in probe damage. As a specific protection strategy:

[0115] When the ultrasonic transducer 2 is activated, the protective hood of the ultrasonic transducer 2 is opened;

[0116] When the ultrasonic transducer 2 is deactivated, the protective hood of the ultrasonic transducer 2 is closed.

[0117] However, another problem arises. Due to the presence of the protective hood, the measurement near the probe is inaccurate. Therefore, the present invention designs a petal structure. When it is opened, the opening angle is large and dispersed, without blocking the upstream and downstream of the water flow, thus solving the above problem, which is a clever design not proposed in the prior art.

[0118] Specifically, it cleverly utilizes the combination of an umbrella-opening structure and a petal structure to form a bent-arm force-consuming lever, achieving a large swing with a small-angle input. The protective hood includes a push rod base 8 provided on the guiding housing 7 and a sliding sleeve 9 connected to the push rod base 8 through a polished rod sleeve and sleeved on the guiding housing 7;

[0119] A plurality of swing bent arms 12 are hinged at the end of the guiding housing 7; a petal guard plate 13 is provided on one side arm of the swing bent arm 12; by utilizing the hinged setting on the guiding housing 7 at a different height from the probe, the water flow can be avoided as much as possible.

[0120] An articulated sliding seat 11 slides in a radial channel on the other side arm of the swing bent arm 12;

[0121] There is a petal gap 14 between adjacent petal guard plates 13;

[0122] The sliding sleeve 9 is hinged to the articulated sliding seat 11 through a traction rod 10;

[0123] When the protective hood needs to act, the push rod base 8 drives the sliding sleeve 9 to move through the polished rod sleeve, causing the traction rod 10 to pull the articulated sliding seat 11, making the swing bent arm 12 swing, and thus driving the petal guard plate 13 to open and close.

[0124] The water turbine volute flow measurement system of this embodiment includes an ultrasonic transducer 2 and a pressure sensor 3 installed on the water turbine. The ultrasonic transducer 2 and the pressure sensor 3 are electrically connected to a host computer;

[0125] For supporting the above calibration method;

[0126] As a theoretical improvement, an elastic net is connected between the petal guard plates 13 to further reduce the entry of debris.

[0127] The present invention is fully described for a clearer disclosure, and the prior art will not be listed one by one.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; as those skilled in the art, it is obvious to combine multiple technical solutions of the present invention. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. The technical content not described in detail in the present invention is all well-known technology.

Claims

1. A calibration method for flow measurement by differential pressure method of a turbine volute, characterized in that: The method comprises the following steps: Step 1: Arrange the measurement components; first, based on the volute (4) of the turbine, there is a straight section flow channel (5) upstream of the volute (4), and in the straight section flow channel (5), a plurality of sound channels are arranged in parallel according to the sound channel height, and an ultrasonic transducer (2) is arranged; Then, based on the volute pressure difference flow measurement method, the flow rate Q is obtained , formula (1); Among them, , a pressure sensor (3) installed on the inner and outer circular pipe walls of the volute (4) is used to measure the differential pressure between the high and low pressure sides of the pressure measuring pipes, and k and n are Winter-Kennedy coefficients; Secondly, based on the ultrasonic flow measurement method, the flow rate Q is obtained; , formula (2); In the formula, is the radius of the flow channel cross-section, is the number of sound channels, is the integration weight coefficient, is the flow velocity of the sound channel; Next, obtain the flow rates obtained by the ultrasonic flow measurement method for i groups , and simultaneously obtain the volute differential pressure , and calibrate the k and n coefficients in formula (1); Step 2: First, take the logarithm of both sides of formula (1): , formula (3); Let , , transform formula (3) into a linear function , formula (4); Afterwards, for the flow rates obtained by multiple groups of ultrasonic flow measurement methods , take the natural logarithm ; for the multiple groups of differential pressure values corresponding to the flow rates , take the natural logarithm , formula (5); where is the measurement order number of the measured value; In formula (4), where , are undetermined constants, and the acquisition point is obtained; Subsequently, through the point Assume a straight line; set a straight line , deviation , formula (6), formula (6) expresses The value corresponding to the straight line And the actual value The deviation between them, the smaller this deviation indicates that the point Is closer to the assumed straight line, using To measure the total deviation; Then, the constructor: , formula (7); When formula (7) takes the minimum value, the obtained and are the solutions to be found; Then, according to the extreme value principle: , namely , Formula (8); Solving the equations together we get: Formula (9); Obtained Formula (10); The obtained values ​​of k and n are the exact values ​​of the Winter-Kennedy coefficients in formula (1).

2. The calibration method for flow measurement by differential pressure method of the spiral case of a hydraulic turbine according to claim 1, characterized in that: At the point In the assumed straight-line step, based on the linear regression process, with the aid of the coefficient Formula (11); It is to calculate the correlation coefficient based on the product-moment method, The closer it is to 1, the better.

3. A method for measuring the flow rate of a turbine volute, characterized in that: An ultrasonic transducer (2) and a pressure sensor (3) are installed on the turbine, and the ultrasonic transducer (2) and the pressure sensor (3) are electrically connected to a host computer; The measurement method includes the following steps: Step A, starting the pressure sensor (3) to measure flow based on the volute pressure difference, and starting the ultrasonic transducer (2) to measure flow based on the ultrasonic flow measurement method; Step B, executing the calibration method described in claim 1 to correct the coefficient of the volute pressure difference flow measurement; Step C, using a volute pressure difference flow measurement method after correction coefficient to perform real-time flow measurement; Step D, regularly turning on the ultrasonic transducer (2) to detect whether the flow rate measured by the volute pressure difference flow measurement method is correct, so as to determine whether there is any equipment failure or wear; Step E, after the faulty or worn equipment is replaced, repeat steps B and C.

4. The method for measuring the flow rate of a turbine volute according to claim 3, characterized in that: When there are several turbines, when equipment failure or wear is identified, one of the following strategies is initiated; Strategy 1: introducing an expected standard amount of water flow into the turbine, starting the ultrasonic flow measurement method to calibrate the ultrasonic transducer (2) to check whether there is equipment failure or wear and / or starting the volute pressure difference flow measurement method for secondary calibration; Strategy 2: Start the ultrasonic transducer (2) of the adjacent turbine for comparison and verification.

5. The flow measurement method for the spiral case of a water turbine according to claim 3, characterized in that: The ultrasonic transducer (2) is provided with a protective head cover; When the ultrasonic transducer (2) is started, the protective head cover of the ultrasonic transducer (2) is opened; When the ultrasonic transducer (2) is turned off, the protective head cover of the ultrasonic transducer (2) is closed.

6. The method for measuring the flow in the spiral case of a water turbine according to claim 3, characterized in that: The protective head cover comprises a push rod base (8) arranged on the guide housing (7) and a sliding sleeve (9) connected to the push rod base (8) via a smooth rod sleeve and sleeved on the guide housing (7); A plurality of swing arms (12) are hingedly connected to the end of the guide housing (7); a petal guard plate (13) is provided on one side arm of the swing arm (12); A hinged sliding seat (11) slides in a radial groove on the other side arm of the swing arm (12); There is a petal gap (14) between adjacent petal guard plates (13); The sliding sleeve (9) is hingedly connected to a hinged sliding seat (11) via a traction rod (10); When the head cover needs to be protected, the push rod base (8) drives the sliding sleeve (9) to move through the light rod sleeve, so that the traction rod (10) drives the hinged sliding seat (11), so that the swing arm (12) swings, thereby driving the petal guard plate (13) to open and close.

7. A flow measurement system for a turbine volute, characterized in that: The invention comprises an ultrasonic transducer (2) and a pressure sensor (3) installed on the turbine, wherein the ultrasonic transducer (2) and the pressure sensor (3) are electrically connected to a host computer; Used to support the calibration method described in claim 1; The ultrasonic transducer (2) includes a transducer probe (6); the transducer probe (6) is installed and extends into the inner cavity of the straight-section flow channel (5); the protective hood is installed on the guiding housing (7) and is used to cover the transducer probe (6). The protective hood includes a push rod base (8) arranged on the guiding housing (7) and a sliding sleeve (9) connected to the push rod base (8) through a polished rod sleeve and sleeved on the guiding housing (7). A plurality of swing bent arms (12) are hinged at the end of the guiding housing (7); a petal-shaped guard plate (13) is provided on one side arm of the swing bent arm (12). A hinged sliding seat (11) slides in the radial channel on the other side arm of the swing bent arm (12). A petal gap (14) is provided between adjacent petal-shaped guard plates (13). The sliding sleeve (9) is hinged with the hinged sliding seat (11) through a traction rod (10).

8. The water turbine volute flow measurement system according to claim 7, characterized in that: An elastic net is connected between the petal-shaped guard plates (13).

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