Calculation method and system for differential pressure flow coefficient of bulb tubular turbine

Abstract

The invention provides a bulb tubular turbine differential pressure flow coefficient calculation method and system. Belongs to the technical field of water turbine operation characteristic calculation and analysis. According to the method, correlation coefficient calculation is carried out on water pressure measured values of a plurality of units under the same test condition along with a power curve, a measuring point data curve with a high correlation coefficient is preferably selected to participate in calculation of a flow coefficient, and a calculation expression of a water turbine head and differential pressure flow based on field actual measurement data is deduced; and in combination with a water turbine operation comprehensive characteristic diagram given by a water turbine manufacturer, a calculation step for fitting the differential pressure flow coefficient based on the field measured data of the hydropower station is given. According to the method, the uncertainty influence of power actual measurement data caused by rotation of the bulb tubular turbine paddle is avoided, and the problems that a large bulb tubular turbine unit is large in water diversion pipeline size, large in flow measurement difficulty and difficult in field flow coefficient drawing are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water turbine operation characteristic calculation and analysis, and particularly relates to a bulb tubular turbine differential pressure flow coefficient calculation method and system. BACKGROUND

[0002] Water turbine flow is mainly used for calculating water turbine operation efficiency, and is a key parameter for water turbine operation characteristic analysis. A differential pressure flow meter is configured at a water power station to measure flow, and the measurement points of the differential pressure flow meter are configured differently for different forms of water turbines. However, the differential pressure flow meter needs to be calibrated with a differential pressure flow coefficient. Large-scale water power plants have larger and larger unit sizes, and it is difficult to accurately measure the flow of a super-large pipe diameter water diversion system. On the other hand, due to the influence of various factors, it is difficult to determine the accuracy of the water pressure data measured by the water pressure measuring instrument on site, and the differential pressure flow coefficient fitted based on the on-site measured data is uncertain. Due to these factors, the differential pressure flow measurement system configured for the water power station unit is mostly in a limited state.

[0003] In theory, the differential pressure flow coefficient is mainly determined by the geometric structure parameters of the measurement point section, and is irrelevant to the operation condition. In practice, due to the use of the section average flow velocity in the derivation process of the differential pressure flow calculation formula, the distribution of the section flow velocity along the pipe diameter direction will change greatly under different water flow, and the use of the section average flow process for equivalent calculation will cause errors, especially in the case of large section area or pipe diameter, the error is more obvious. Field measurement shows that the flow coefficient changes slightly with the load condition or flow. In ultrasonic flow measurement, this non-uniform distribution characteristic of the section flow velocity is still the main cause of the measurement error. Although the differential pressure flow measurement has certain errors, its application cost is relatively low, and the differential pressure flow meter is basically configured in the water power unit flow measurement. In the field of a water power station, for a large pipe diameter water diversion flow channel, how to calibrate the water turbine differential pressure flow coefficient by using a relatively simple method has not been a good method. The bulb tubular turbine has low water head and large flow, and the size of the water diversion flow channel is large, so it is difficult and expensive to calibrate the differential pressure flow coefficient on site by using a higher level of precision instrument. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0005] To this end, the first object of the present application is to propose a bulb tubular turbine differential pressure flow coefficient calculation method. Two assumptions are proposed from the actual operation conditions of the bulb tubular unit on site of the water power station, and a bulb tubular turbine differential pressure flow coefficient fitting method based on on-site measured data is given on the premise of the two assumption conditions. The theory is clear, the technical scheme and calculation are simple, and the problem of on-site calibration of the differential pressure flow coefficient of a large bulb tubular unit is solved.

[0006] The second object of the present application is to provide a system for calculating the differential pressure flow coefficient of a bulb turbine.

[0007] To achieve the above object, the first aspect of the present application provides a method for calculating the differential pressure flow coefficient of a bulb turbine, comprising: S1, obtaining a water head calculation expression of the turbine based on measured data according to the water pressure measurement point arrangement information of the bulb turbine unit and the measured water pressure data related to the water head calculation; S2, obtaining a differential pressure flow calculation expression of the turbine based on measured data according to the water pressure measurement point arrangement information of the bulb turbine unit and the measured water pressure data related to the flow calculation; S3, calculating the correlation coefficient of the water head and the flow differential pressure measurement point curve of the turbine of the multiple units based on the water head calculation expression of the turbine, the differential pressure flow calculation expression of the turbine and the measured water pressure data of the multiple units of the hydropower station; S4, calculating the differential pressure flow coefficient based on the differential pressure flow calculation expression of the turbine, the measured data of the hydropower station and the correlation coefficient.

[0008] In one embodiment of the present application, the measurement point diagram of the bulb turbine is obtained, and the water head of the turbine is defined as the energy difference between the inlet and outlet sections of the turbine, i.e. the energy difference between the pressure measurement section 1 of the inlet of the flow passage and the pressure measurement section 9 of the outlet of the draft tube; the flow differential pressure measurement points of the bulb turbine unit are sections 2 and 5.

[0009] In one embodiment of the present application, the S1 comprises: S1-1, the measurement points of sections 1 and 9 have the same elevation, and the water head of the turbine is: (1) In the formula, H t is the water head of the turbine, H 1、 H 9 are the water pressures of sections 1 and 9 respectively, V 1、 V 9 are the flow rates of sections 1 and 9 respectively, α 1 is the correction coefficient of section 1, g is the acceleration of gravity; S1-2, rewriting the water head formula (1) of the turbine as: (2) In the formula, is the section coefficient, A 1、 A 9 are the areas of sections 1 and 9 respectively, and Q is the flow of the turbine, α9 is the correction coefficient of section 9; S1-3, according to the orifice outflow principle, the water turbine flow is expressed as: (3) In the formula, K u is the flow coefficient, Y is the guide vane opening, H t is the water head of the water turbine; S1-4, at the rated water head and rated flow, it satisfies , Q r , Y r , H tr respectively, the flow, guide vane opening and water head of the water turbine at the rated operating condition, with the rated operating condition parameters as the base value, the relative value form is: (4) Among them, q = Q / Q r is the flow relative value, h t = H t / H tr is the water head relative value of the water turbine, y = Y / Y r is the guide vane opening relative value; S1-5, formula (4) is substituted into formula (2): (5) S1-6, in the actual operation of the hydropower station, the guide vane opening of the speed regulator adopts the relative value form; if the guide vane opening base value is Y B , then: (6) Among them, y r is the guide vane opening relative value at the rated operating condition; S1-7, the water pressure difference of measuring points 1 and 9 is recorded as H 1_9 = H 1- H 9; formula (6) is substituted into formula (5) and arranged as: (7) Among them, , Htr is the rated water head under rated working condition.

[0010] In an embodiment of the present application, according to the geometry of the unit flow passage structure, the rated water head K f is calculated according to the design parameters of the water turbine H r and the rated flow Q r The calculation coefficient K .

[0011] In an embodiment of the present application, the S2 includes: S2-1, the Bernoulli equation between the flow differential pressure measuring points of section 2 and section 5 is established, the elevations of the two section measuring points are the same, and there are: (8) wherein, H 2、 H 5 are the water pressures of section 2 and section 5 respectively, V 2、 V 5 are the flow velocities of section 2 and section 5 respectively, α 2、 α 5 are the correction coefficients of section 2 and section 5 respectively, V is the average flow velocity between section 2 and section 5, λ is the equivalent hydraulic loss coefficient between section 2 and section 5; S2-2, the above formula (8) is rewritten as: (9) wherein, H = H 2- H 5 is the pressure difference between section 2 and section 5, A 2、 A 5、 A s are the equivalent section areas of section 2, section 5 and section 2 to section 5 respectively, Q is the flow through the section; S3-3, the water pressure difference of measuring points 2 and 5 is recorded as H 2_5 = H 2- H 5; formula (9) is rewritten as: (10) wherein, is the bulb through-flow.

[0012] In one embodiment of the present application, the correlation coefficient of the water head and the differential pressure of the water turbine of the multiple units of the hydropower station is calculated, the data curve with high correlation coefficient is selected for pre-processing, and the water head of the water turbine for calculating the differential pressure flow coefficient is obtained H 1_9 and the differential pressure H 2_5 .

[0013] In one embodiment of the present application, S3 comprises: S3-1, the multiple units installed in the hydropower station have the same flow passage structure and hydraulic characteristics, and the water head measuring point and the differential pressure measuring point are the same; S3-2, under the same test conditions, the data curves of the water pressure changing with the load of each unit are obtained by testing; S3-3, the correlation coefficient is calculated: (11) wherein r is the correlation coefficient of variables X and Y, , and the standard deviation of variables X and Y, , is the mean value of variables X and Y; S3-4, the correlation coefficient of the measured data H 1_9 of the multiple units under the same test conditions is calculated by formula (11); 2-3 groups of data with high correlation coefficient are selected and the mean value is taken as the calculation data, and the correlation coefficient of H 2_5 of the multiple units is calculated in the same way, and the data curve for calculation is selected.

[0014] In one embodiment of the present application, S4 comprises: S4-1, according to the selected measured water pressure H 1_9 and the relative opening of the guide vane y , the water head of the water turbine is calculated according to formula (7) H t ; S4-2, under the preset condition of the water head, the flow of the water turbine is related to the opening of the guide vane, and the change of the blade opening does not affect the efficiency of the water turbine converting mechanical energy; According to the water head of the water turbine H t and the guide vane opening, the flow of the water turbine is read from the comprehensive characteristic diagram of the water turbine Q i ; S4-3, according to the selected measured data H 2_5 and Q, the differential pressure flow coefficient K Q is calculated according to formula (10); S4-4, repeat the above calculation process S4-1, S4-2, S4-3, calculate the differential pressure flow coefficient under full load condition K Q ; With the guide vane relative opening y As the horizontal coordinate, draw K Q - y Curve, and fitting, reduce data reading error, obtain accurate flow coefficient K Q .

[0015] To achieve the above purpose, the second aspect of the present application provides a bulb tubular turbine differential pressure flow coefficient calculation system, comprising: a water turbine head calculation module, for obtaining a water turbine head calculation expression based on measured data according to the water pressure measuring point arrangement information of the bulb tubular unit and the measured water pressure data related to the head calculation; A water turbine differential pressure flow calculation module is used to obtain a water turbine differential pressure flow calculation expression based on measured data according to the water pressure measuring point arrangement information of the bulb tubular unit and the measured water pressure data related to the flow calculation; A curve correlation coefficient calculation module is used to calculate the correlation coefficient of the water turbine head and the flow differential pressure measuring point curve of the multiple units based on the water turbine head calculation expression and the water turbine differential pressure flow calculation expression and the measured water pressure data of the multiple units of the hydropower station; A differential pressure flow coefficient module is used to calculate the differential pressure flow coefficient based on the water turbine differential pressure flow calculation expression, the measured data of the hydropower station and the correlation coefficient.

[0016] The method and system of the embodiment of the present application avoid the uncertainty influence of the power measurement data caused by the rotatable paddle of the bulb tubular turbine, and solve the problems of large size of the diversion pipe of the large bulb tubular unit, difficulty in flow measurement, and difficulty in on-site preparation of flow coefficient.

[0017] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which: Figure 1 A flowchart of a bulb tubular turbine differential pressure flow coefficient calculation method provided by an embodiment of the present application is shown; Figure 2 A bulb tubular turbine measuring point arrangement diagram provided by an embodiment of the present application is shown; Figure 3 Measuring points provided for the embodiments of the present application H 1_9 Correlation coefficient thermodynamic diagram Figure 4 Measuring points provided for the embodiments of the present application H 2_5 Correlation coefficient thermodynamic diagram Figure 5 Water head of a bulb tubular turbine provided for the embodiments of the present application H t With guide vane opening y Change curve diagram Figure 6 Flow Q of a bulb tubular turbine provided for the embodiments of the present application changes with guide vane opening y Change curve diagram Figure 7 Flow coefficient provided for the embodiments of the present application K Q With guide vane opening y Change curve diagram Figure 8 Structure diagram of a bulb tubular turbine differential pressure flow coefficient calculation system according to the embodiments of the present application. DETAILED DESCRIPTION

[0019] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] In order to enable persons skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative labor should belong to the protection scope of the present application.

[0021] A bulb tubular turbine differential pressure flow coefficient calculation method and system according to the embodiments of the present application will be described below with reference to the accompanying drawings.

[0022] The present application calculates the correlation of water pressure measurement curve, selects the data with the smallest measurement error from the same measuring point data of multiple machines for curve fitting calculation, combines the water turbine operation comprehensive characteristic diagram provided by the manufacturer, and obtains the corresponding flow according to the water turbine water head and guide vane opening, and then fits to obtain the bulb tubular turbine differential pressure flow coefficient.

[0023] Figure 1 is a flow chart of a bulb tubular turbine differential pressure flow coefficient calculation method according to the embodiments of the present application, likeFigure 1 As shown in the figure, including: S1, according to the water pressure measuring point arrangement information of the bulb tubular unit and the measured water pressure data related to the water head calculation, the water turbine water head calculation expression based on the measured data is obtained.

[0024] It can be understood that the measuring point diagram of the bulb tubular turbine is as shown in the figure Figure 2 As shown in the figure, the water turbine water head is defined as the energy difference between the inlet and outlet sections of the water turbine, that is, the energy difference between section 1 and section 9.

[0025] In an embodiment of the present application, according to the water pressure measuring point arrangement of the bulb tubular unit, the water turbine water head calculation expression based on the measured data is derived as:

[0026] Wherein, , ; According to the geometric size of the flow channel structure of the unit, the water head K f , according to the design parameters of the water turbine, the rated water head H r and the rated flow Q r The calculation coefficient K .

[0027] It can be understood that, Figure 2 In the figure: 1 is the flow passage inlet pressure measuring section, 2 is the water turbine flow inlet pressure measuring section, 3 is not installed, 4 is the front pressure measuring section of the movable guide vane, 5 is the water turbine flow outlet pressure measuring section, 6 is the rear pressure measuring section of the movable guide vane, 7 is the tail water pipe inlet pressure measuring section, 8 is the tail water pipe pressure fluctuation measuring section, and 9 is the tail water pipe outlet pressure measuring section.

[0028] It can be understood that the "section" described in the context refers to Figure 2 the meaning of the related reference in the figure, for example, section 1 is the flow passage inlet pressure measuring section; Section 2 is the water turbine flow inlet pressure measuring section; and so on.

[0029] It can be understood that the "measuring point" described below also refers to Figure 2 the meaning of the related reference in the figure, for example, measuring points 1 and 9 are the flow passage inlet pressure measuring section and the tail water pipe outlet pressure measuring section, respectively, and so on.

[0030] The specific steps of the embodiment of the present application are as follows: The elevations of section 1 and section 9 are the same, and the water turbine water head is: (1) Wherein,H t is the water head of the water turbine (m), H 1、 H 9is the water pressure of section 1, section 9 (m), V 1、 V 9is the flow velocity of section 1, section 9 (m / s), α 1is the correction coefficient of section 1, g is the acceleration of gravity (m / s). 2

[0031] Equation (1) is rewritten as: (2) wherein, is the section coefficient, A 1、 A 9is the area of section 1, section 9 (m 2 ), Q is the flow rate of the water turbine, α 9is the correction coefficient of section 9.

[0032] According to the principle of orifice outflow, the flow rate of the water turbine is expressed as: (3) wherein, K u is the flow coefficient, Y is the guide vane opening degree, H t is the water head of the water turbine.

[0033] At the rated water head and the rated flow rate, the following is satisfied: , Q r 、 Y r 、 H tr are respectively the flow rate, the guide vane opening degree and the water head of the water turbine under the rated working condition. With the rated working condition parameters as the base value, the relative value form is: (4) wherein, q = Q / Q r is the flow relative value, h t = H t / H tr is the water head relative value of the water turbine, y = Y / Y r is the guide vane opening degree relative value. ​

[0034] Substitute equation (2) with equation (4): (5) In the actual operation of hydropower stations, the guide vane opening of the governor is in the form of a relative value. The guide vane opening base value is not necessarily Y r If the guide vane opening base value is Y B , then: (6) wherein y r is the guide vane opening relative value at the rated operating condition.

[0035] The water pressure difference of measuring points 1 and 9 is denoted as H 1_9 = H 1- H 9. Substitute equation (6) into equation (5) and rearrange to have: (7) wherein , H tr is the rated water head (m) at the rated operating condition.

[0036] Further, in step S1, the section correction coefficient α 1= α 9=1 is taken, and K f is calculated according to the geometric size of the flow passage of the power station, and then the coefficient K is calculated. From the form of the coefficient K , K is a constant irrelevant to the operating condition.

[0037] Further, the approximation in the derivation process of step S1 is mainly that the water turbine flow coefficient K u is approximately constant, and when the flow relative value is taken, the coefficient is eliminated. In fact, the coefficient K u is also variable. The subsequent example calculation shows that even at the rated load, the speed head term is less than 1%Hr, and at the rated load, the value of this term is smaller. This approximation will not cause large calculation errors.

[0038] S2, according to the water pressure measuring point arrangement information of the bulb tubular unit and the measured water pressure data related to flow calculation, a water turbine differential pressure flow calculation expression based on measured data is obtained.

[0039] It can be understood that according to the water pressure measuring point arrangement of the bulb turbine unit, the water turbine differential pressure flow calculation expression based on the measured data is derived, and the flow differential pressure measuring points of the bulb turbine unit in step S2 are section 2 and section 5, as shown in Figure 2

[0040] Further, the water turbine differential pressure flow calculation expression based on the measured data in step S2 is derived, and the specific steps are as follows: The Bernoulli equation between the flow differential pressure measuring points of section 2 and section 5 is established, and the elevations of the two section measuring points are the same, and it has: (8) Wherein, H 2、 H 5 are the water pressures (m) of section 2 and section 5 respectively, V 2、 V 5 are the flow velocities (m / s) of section 2 and section 5 respectively, α 2、 α 5 are the correction coefficients of section 2 and section 5 respectively, V is the average flow velocity (m / s) between section 2 and section 5, λ is the equivalent hydraulic loss coefficient between section 2 and section 5.

[0041] The above formula (8) is rewritten as: (9) Wherein, H = H 2- H 5 is the pressure difference (m) between section 2 and section 5, A 2、 A 5、 A s are the equivalent cross-sectional areas (m 2 ) of section 2, section 5 and section 2 to section 5 respectively, Q is the flow (m 3 / s) through the section.

[0042] The water pressure difference of measuring points 2 and 5 is recorded as H 2_5 = H 2- H 5. Formula (9) is rewritten as: (10) Wherein, is the differential pressure flow coefficient of the bulb turbine unit.

[0043] ​S3, calculating the correlation coefficient of the water head and the flow differential pressure measuring point curve of the multiple units of the hydropower station based on the water head calculation expression of the water turbine, the flow differential pressure calculation expression of the water turbine, and the measured water pressure data of the multiple units of the hydropower station.

[0044] Specifically, the correlation coefficient of the water head and the flow differential pressure measuring point curve of the multiple units of the hydropower station is calculated, and the calculation formula is as follows: (11) wherein r is the correlation coefficient of variables X and Y, , is the standard deviation of variables X and Y, respectively, , is the mean value of variables X and Y.

[0045] Further, step S3 uses the correlation coefficient to reflect the reason for the differential pressure. Assumption 1: the multiple units installed in the hydropower station have the same flow passage structure and hydraulic characteristics, the water head measuring point and the differential pressure measuring point are the same, and the probability of the multiple units of the hydropower station simultaneously having the same fault is very small.

[0046] Under the same test conditions, the multiple units of the hydropower station test the data curves of the random group load changes of each water pressure. If the trend is consistent, the correlation coefficient is high; otherwise, if the water pressure measuring point data trend is different, the correlation coefficient is low, and it is possible that the water pressure measuring point data has a fault (blockage, pulsation, etc.) to induce measurement error.

[0047] Further, step S3 selects the data curve with a high correlation coefficient for preprocessing to obtain the water head of the water turbine H 1_9 and the differential pressure H 2_5 for calculating the flow coefficient of the differential pressure. The specific steps are as follows: The correlation coefficient of the measured data of the multiple units under the same test conditions is calculated by formula (11). H 1_9 The correlation coefficient of the measured data of the multiple units under the same test conditions is calculated by formula (11). H 2_5 The correlation coefficient of the measured data of the multiple units under the same test conditions is calculated by formula (11).

[0048] The H 1_9 and H 2_5 of the same unit are selected as much as possible to reduce the error caused by slight differences in test conditions.

[0049] S4, calculating the flow coefficient of the differential pressure based on the flow differential pressure calculation expression of the water turbine, the measured data of the hydropower station, and the correlation coefficient.

[0050] Specifically, the differential pressure flow coefficient is calculated according to the measured data of the hydropower station combined with the operating comprehensive characteristic curve of the bulb tubular turbine unit, and the specific steps are as follows: (1) According to the selected measured water pressure H 1_9 and the guide vane relative opening y , the water head of the water turbine is calculated according to formula (7) H t .

[0051] (2) Hypothesis 2: Under the condition of a certain water head, the water turbine flow is related to the guide vane opening, and the paddle opening only changes the efficiency of the water turbine converting mechanical energy, and has no effect on the water turbine flow.

[0052] According to this hypothesis, the water turbine flow H t is read from the water turbine operating comprehensive characteristic diagram according to the water head of the water turbine Q i .

[0053] (3) According to the selected measured data H 2_5 and Q , the differential pressure flow coefficient K Q is calculated according to formula (10)

[0054] (4) Repeat the calculation process (1), (2), (3) to calculate the differential pressure flow coefficient K Q under full load conditions.

[0055] Further, step S4 takes the guide vane relative opening y as the horizontal coordinate to draw K Q - y curve, and performs fitting to reduce data reading error and obtain accurate flow coefficient K Q .

[0056] In an embodiment of the present application, the bulb tubular turbine differential pressure flow coefficient calculation method of the present application is described in detail.

[0057] Suppose that a hydropower station is installed with 8 bulb tubular turbine units. The full load condition measured data of the hydropower station includes water head measuring points H 1, H 2, H 5, H 9 and guide vane relative value y .

[0058] Step 1: According to the water pressure measuring point arrangement of the bulb turbine unit, the water head calculation expression based on the measured data is derived as: According to the flow channel structure data of the hydropower station, it is calculated that: The area of section 1 is: A 1 = 140.5488 (m 2 ); The area of section 9 is: A 9 = 94.5 (m 2 ); The local gravitational acceleration is: g = 9.783 (m 2 / s); The section correction coefficient is taken as α 1 = α 9 = 1;

[0059] The design flow rate is Q r = 252.45 (m 3 / s), H r = 21.7 (m), y r = 0.75 (pu). The calculation coefficient K is: ; According to formula (7), the water head of the water turbine is:

[0060] In the rated load working condition, the relative opening degree of the guide vane is y r = 0.75 (75%), and the water head correction term is 0.0164 y 2 = 0.0092, that is, 0.92%Hr, which is less than 1% of the rated water head. In the working condition below the rated load, the correction coefficient is smaller. Therefore, the derivation process assumes that the flow coefficient of the water turbine K u is approximately constant, and this approximate treatment will not cause large calculation errors.

[0061] Step 2: According to the water pressure measuring point arrangement of the bulb turbine unit, the water head calculation expression based on the measured data is derived as:

[0062] Step 3: Calculate the correlation coefficient of the water head and flow differential pressure measuring point curve of the water turbine of the multiple units of the hydropower station, select the data curve with high correlation coefficient for preprocessing, and obtain the water head of the water turbine for calculating the differential pressure flow coefficient H1_9 and differential pressure H 2_5 .

[0063] The measured 0-100% power points of the hydropower station are given, and the actual power of the 8 units is given with slight differences. The power is taken as the horizontal coordinate, and the water pressure is taken as the vertical coordinate. To ensure the consistency of the measurement points, the power and water pressure curves of each unit are fitted, and the water pressure is interpolated according to the power P, and the horizontal coordinates of the 8 unit measurement points are unified to the same measurement point scale. P-H 1_9 , P-H 2_5

[0064] The correlation coefficients of the water pressures of the 8 units are calculated, and the correlation coefficient thermograph is used to represent them, as shown in FIG. 8. H 1_9 Figure 3

[0065] The correlation coefficients of the water pressures of the 8 units are calculated, and the correlation coefficient thermograph is used to represent them, as shown in FIG. 8. H 2_5 Figure 4

[0066] Figure 3 In the above, the correlation coefficients of units 5, 7 and 8 are above 0.95. H 1_9 Figure 4 In the above, the correlation coefficients of units 4, 5, 7 and 8 are above 0.999. The water pressure of unit 5 is selected H 2_5 H 1_9 and H 2_5 for subsequent calculation.

[0067] Step 4: Calculate the differential pressure flow coefficient according to the measured data of the hydropower station combined with the comprehensive characteristic curve of the bulb tubular unit operation.

[0068] (1) According to the selected measured water pressure H 1_9 and the relative opening of the guide vane y , the water head of the water turbine is calculated according to formula (7) H t .

[0069] The change of the water head of the water turbine with the opening of the guide vane is shown in the attached Figure 5 .

[0070] The attached Figure 5 gives whether to consider the correction coefficient K , the measured water head H 1_9 and H ​​​​​​​t A comparison of the differences. As can be seen from the figure, the hydropower station governor adopts... H 1_9 As the turbine head, there is a certain margin of error. The head error before and after correction when the rated output is reached is 0.87%Hr.

[0071] (2) Based on the turbine head H t The turbine flow rate is read from the turbine's comprehensive operating characteristic diagram, along with the guide vane opening. Q The turbine flow rate varies with the guide vane opening as shown in the attached figure. Figure 6 As shown.

[0072] (3) Based on the measured data of the selected Unit 5 H 2_5 and Q Calculate the differential pressure flow coefficient according to formula (10). K Q .

[0073] (4) Repeat the above calculation process (1), (2), and (3) to calculate the differential pressure flow coefficient under full load conditions. K Q Based on the relative opening of the guide vanes y Plot the x-axis. K Q - y The curve is fitted to reduce data reading errors.

[0074] K Q - y The curve and the fitted curve are attached. Figure 7 As shown.

[0075] from Figure 7 Looking at the vertical axis, the flow coefficient K Q The opening variation at full load is approximately 11.5%. A linear fit was used, and the deviation between the fitted data and the calculated data is within the range of -1.55% to +1.73%.

[0076] In summary, bulb turbines have adjustable blades. With the same guide vane opening, different blade angles result in varying turbine conversion efficiency, meaning there's no single-valued correlation between guide vane opening and turbine output power. This invention avoids this problem by using precisely measurable water pressure data combined with the manufacturer's comprehensive operating characteristic curves for calculation, making it convenient to apply. By fitting the flow coefficient under full opening conditions, a calculation method for a single-valued functional relationship between the flow coefficient and guide vane opening is established, solving the problem of large calculation errors under different flow rates caused by non-uniform velocity distribution in large-size flow channel cross-sections.

[0077] To achieve the above embodiments, such as Figure 8 As shown, this embodiment also provides a differential pressure flow coefficient calculation system 10 for bulb turbines, including: The turbine head calculation module 100 is used to obtain the turbine head calculation expression based on the measured data according to the water pressure measurement point layout information of the bulb turbine and the measured water pressure data related to the head calculation. The turbine differential pressure flow calculation module 200 is used to obtain the turbine differential pressure flow calculation expression based on the measured data, according to the water pressure measuring point layout information of the bulb turbine and the measured water pressure data related to flow calculation. The curve correlation coefficient calculation module 300 is used to calculate the correlation coefficient of the turbine head and flow differential pressure measurement point curves of multiple units based on the turbine head calculation expression, the turbine differential pressure flow calculation expression, and the measured water pressure data of multiple units in the hydropower station. The differential pressure flow coefficient module 400 is used to calculate the differential pressure flow coefficient based on the turbine differential pressure flow calculation expression, the measured data of the hydropower station, and the correlation coefficient.

[0078] The differential pressure flow coefficient calculation system for bulb turbines in this invention calculates the correlation coefficient between water pressure measurements and power curves under the same test conditions for multiple units. It prioritizes data curves from measurement points with high correlation coefficients for flow coefficient calculation, solving the problem of difficulty in interpreting on-site water pressure measurement data for potential errors. The system derives calculation expressions for turbine head and differential pressure flow based on on-site measured data. Combining this with the turbine manufacturer's comprehensive operating characteristic diagram, it provides calculation steps for fitting the differential pressure flow coefficient based on on-site measured data from hydropower stations. This invention avoids the uncertainty in measured power data caused by the rotatable blades of bulb turbines and solves the problems of large-scale bulb turbine units, large water intake pipe dimensions, difficulty in flow measurement, and difficulty in determining flow coefficients on-site.

[0079] In the description of this specification, the references to "one embodiment," "some embodiments," "example," "specific example," or "some examples" refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0080] Furthermore, the terms "first", "second", "third", "fourth", "fifth" and "sixth" are used herein for descriptive purposes only and are not to be construed as indicating or implying relative importance or a significant difference from other embodiments. Thus, a feature defined with "first", "second", "third", "fourth", "fifth" or "sixth" can implicitly or explicitly include at least one of the features. In the description of the present application, the meaning of "a plurality" is at least two, for example two, three, unless otherwise explicitly specified.

Claims

1. A method of calculating the differential pressure flow coefficient of a bulb turbine, characterized by, The method comprises the following steps: S1, obtaining a water head calculation expression of a water turbine based on measured data according to water pressure measuring point arrangement information of a bulb turbine unit and measured water pressure data related to water head calculation; S2, obtaining a differential pressure flow calculation expression of a water turbine based on measured data according to water pressure measuring point arrangement information of a bulb turbine unit and measured water pressure data related to flow calculation; S3, calculating a correlation coefficient of a water turbine water head and a flow differential pressure measuring point curve of a plurality of units of a hydropower station based on the water head calculation expression of the water turbine, the differential pressure flow calculation expression of the water turbine and measured water pressure data of the plurality of units of the hydropower station; S4, calculating a differential pressure flow coefficient based on the differential pressure flow calculation expression of the water turbine, measured data of the hydropower station and the correlation coefficient.

2. The method of claim 1, wherein, The measuring point diagram of the bulb turbine is obtained, the water head of the water turbine is defined as the energy difference between the inlet and outlet sections of the water turbine, that is, the energy difference between the pressure measuring section 1 at the water inlet and the pressure measuring section 9 at the tail water outlet, and the flow differential pressure measuring points of the bulb turbine unit are the sections 2 and 5.

3. The method of claim 2, wherein, The S1 comprises the following steps: S1-1, the elevations of the sections 1 and 9 are the same, and the water head of the water turbine is: (1) wherein H t is the water head of the turbine, H 1、 H 9 is the water pressure of the section 1, respectively section 9, V 1、 V 9 is the flow velocity of the section 1, respectively section 9, α 1 is the correction factor of the section 1, g is the acceleration of gravity; S1-2, the water head formula (1) of the water turbine is rewritten as: (2) wherein is the cross-sectional coefficient, A 1、 A 9 is the area of the cross-section 1, 9, Q is the flow rate of the water turbine, α 9 is the correction coefficient of the cross-section 9; S1-3, according to the orifice outflow principle, the flow of the water turbine is represented as: (3) wherein K u is the flow coefficient, Y is the guide vane opening, H t is the water head of the turbine; S1-4, at rated head and rated flow, meet , Q r , Y r , H tr are respectively the flow, guide vane opening and water turbine head under rated conditions, with rated condition parameters as base values, in relative value form: (4) wherein q = Q / Q r is a flow relative value, h t = H t / H tr is a water turbine head relative value, y = Y / Y r is a guide vane opening relative value; S1-5, formula (4) is substituted into formula (2): (5) S1-6, in the actual operation of the hydropower station, the guide vane opening of the governor is in the form of relative value; if the guide vane opening base value is Y B then (6) wherein y r is the relative value of the guide vane opening at the rated operating condition; S1-7, the water pressure difference of measuring points 1 and 9 is recorded as H 1_9 = H 1- H 9; formula (6) is substituted into formula (5) and arranged as follows: (7) wherein , H tr is the rated water head under rated operating conditions.

4. The method of claim 3, wherein, According to the geometric dimensions of the flow passage structure of the unit, calculate K f , according to the design parameters of the water turbine rated water head H r and rated flow Q r Calculate the coefficient K .

5. The method of claim 4, wherein, The S2 comprises the following steps: S2-1, the Bernoulli equation between the flow differential pressure measuring points of the sections 2 and 5 is established, the elevations of the two sections are the same, and the following formula (8) is obtained: (8) wherein, H 2、 H 5 are the water pressures at the sections 2, 5 respectively, V 2、 V 5 are the flow rates at the sections 2, 5 respectively, α 2、 α 5 are the correction factors at the sections 2, 5 respectively, V is the average flow rate between the sections 2 and 5, S2-2, the above formula (8) is rewritten as: is the equivalent hydraulic loss coefficient between the sections 2 and 5. The S3 comprises the following steps: (9) wherein H = H 2- H 5 is the pressure difference between section 2 and section 5, A 2、 A 5、 A s respectively the equivalent cross-sectional area of section 2, section 5, section 2 to section 5, Q is the flow rate through the section; S3-3, the water pressure difference between points 2 and 5 is recorded as H 2_5 = H 2- H 5; formula (9) is rewritten as: (10) wherein is a bulb run-through.

6. The method of claim 5, wherein, The correlation coefficient of the water head and flow differential pressure measuring point curve of the multiple units of the hydropower station is calculated, the data curve with high correlation coefficient is selected for preprocessing, and the water head of the water turbine for calculating the differential pressure flow coefficient is obtained H 1_9 and differential pressure H 2_5 .

7. The method of claim 1, wherein, S3-1, the plurality of units installed in the hydropower station have the same flow passage structure and hydraulic characteristics, and the water head measuring points and the differential pressure measuring points have the same positions; S3-2, under the same test conditions, data curves of the water pressure changing with the load of each unit are obtained by testing; S3-3, the correlation coefficient is calculated: The S4 comprises the following steps: (11) where r is the correlation coefficient of the variables X, Y, , are the standard deviations of the variables X, Y, respectively, , are the means of the variables X, Y, respectively. S3-4, the same test conditions under the measured data H of multiple units is calculated by formula (11) 1_9 Correlation coefficient; Select 2-3 groups of data with high correlation coefficient to take the average as the calculation data, and calculate the correlation coefficient of multiple units H 2_5 in the same way, select the data curve for calculation.

8. The method of claim 7, wherein, S4-2, under the preset water head condition, the flow of the water turbine is related to the guide vane opening degree, the paddle opening degree changes the efficiency of the water turbine converting mechanical energy, and has no influence on the flow of the water turbine; S4-1, the measured water pressure according to the selection H 1_9 and the relative opening of the guide vane y , the water head of the water turbine is calculated according to formula (7) H t ; The method comprises the following steps: The water head of the turbine is determined H t The turbine flow is read from the turbine operating characteristic diagram with the guide vane opening Q i ; S4-3, the measured data H is selected according to 2_5 and Q, the differential pressure flow coefficient K is calculated according to formula (10) Q ; S4-4, repeat the above calculation process S4-1, S4-2, S4-3, calculate the differential pressure flow coefficient under full load condition K Q ; relative opening of the guide vanes y Plot the x-axis. K Q - y The curve is obtained and fitted to reduce data reading errors and obtain an accurate flow coefficient. K Q .

9. A system for calculating the differential pressure flow coefficient of a bulb turbine, the system comprising: The water head calculation module is configured to obtain a water head calculation expression of a water turbine based on measured data according to water pressure measuring point arrangement information of a bulb turbine unit and measured water pressure data related to water head calculation; The differential pressure flow calculation module is configured to obtain a differential pressure flow calculation expression of a water turbine based on measured data according to water pressure measuring point arrangement information of a bulb turbine unit and measured water pressure data related to flow calculation; The curve correlation coefficient calculation module is configured to calculate a correlation coefficient of a water turbine water head and a flow differential pressure measuring point curve of a plurality of units of a hydropower station based on the water head calculation expression of the water turbine, the differential pressure flow calculation expression of the water turbine and measured water pressure data of the plurality of units of the hydropower station; The differential pressure flow coefficient module is configured to calculate a differential pressure flow coefficient based on the differential pressure flow calculation expression of the water turbine, measured data of the hydropower station and the correlation coefficient. ​

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