Method for extending pump-turbine characteristic curves

Abstract

The present application relates to the technical field of water pump water turbine, in particular to a water pump water turbine characteristic curve extension method, which mainly solves the technical problem that the prior art cannot carry out multi-condition digital simulation due to the lack of water pump working condition characteristic curve data. The method comprises the following steps: obtaining the comprehensive characteristic curve of the water turbine working condition, obtaining the numerical value of the water turbine unit flow and efficiency under different unit speeds through image digital processing, and generating the water turbine unit flow characteristic curve; based on the equivalent point conversion method, estimating the water pump unit flow of the water pump working condition under the same unit speed and efficiency, and generating the water pump unit flow characteristic curve; respectively based on the unit flow characteristic curves and efficiency calculation of the water turbine and the water pump, corresponding unit torque is generated, and the water turbine and water pump unit torque characteristic curves are generated. The present application realizes the extension from single condition data to multi-condition data, and provides complete input parameters for the multi-condition digital simulation of the water pump water turbine.

Description

Technical Field

[0001] This invention relates to the field of water pump and turbine technology, and in particular to a method for extending the characteristic curve of a water pump and turbine. Background Technology

[0002] Pumped storage power stations, as large-scale energy storage facilities, undertake key functions such as peak shaving and valley filling, frequency regulation, and phase regulation in the context of renewable energy grid integration. The pump-turbine, as its core equipment, needs to frequently switch between two operating modes: turbine mode and pump mode. Digital simulation of the pump-turbine in the early stages of product design is an effective means to optimize product design and verify control strategies, and the characteristic curve is the core input parameter for digital simulation.

[0003] The comprehensive characteristic curves provided by manufacturers typically only contain data for turbine operation, which can meet the digital simulation requirements for turbine operation, but lack characteristic data for pump operation, thus failing to meet the digital simulation requirements for pump operation. This limits the use of digital simulation methods for product optimization design and control strategy verification under multiple operating conditions.

[0004] Therefore, there is an urgent need for a method to obtain pump operating condition characteristic curve data in order to solve the aforementioned technical problems. Summary of the Invention

[0005] To overcome the technical deficiency of existing technologies that cannot perform multi-condition digital simulation due to the lack of pump operating condition characteristic curve data, this invention proposes a method for extending the characteristic curve of a pump-turbine.

[0006] The method for extending the characteristic curve of a water pump turbine provided by the present invention includes the following steps:

[0007] S1. Obtain the comprehensive characteristic curve of the turbine operating conditions within the target opening range, and obtain the values ​​of turbine unit flow rate and efficiency at different unit speeds through image digitization processing; and generate the turbine unit flow rate characteristic curve based on the correspondence between the unit speed and turbine unit flow rate at different openings.

[0008] S2. Based on the equivalent point transformation method, estimate the unit flow rate of the water pump under the same unit speed and efficiency; and based on the correspondence between the unit speed and the unit flow rate of the water pump, generate the unit flow rate characteristic curve of the water pump.

[0009] S3. Based on the turbine's unit flow characteristic curve and efficiency, calculate the turbine's unit torque, and based on the correspondence between the unit speed and the turbine's unit torque, generate the turbine's unit torque characteristic curve; based on the pump's unit flow characteristic curve and efficiency, calculate the pump's unit torque, and based on the correspondence between the unit speed and the pump's unit torque, generate the pump's unit torque characteristic curve.

[0010] Furthermore, the unit flow rate of the water pump is estimated using the following formula:

[0011] ;

[0012] in, This indicates the unit flow rate of the water pump. This indicates the unit flow rate of the water turbine.

[0013] Furthermore, in step S3, the unit torque of the turbine and the unit torque of the pump are calculated using the following formula:

[0014] ;

[0015] in, This represents the unit torque of a water turbine or the unit torque of a water pump. Indicates the specific gravity of water. This indicates the unit flow rate of the water turbine or the unit flow rate of the water pump. Indicates efficiency. Indicates unit rotational speed.

[0016] Furthermore, in step S1, the target opening range must satisfy the following: the turbine unit flow characteristic curve obtained based on the comprehensive characteristic curve of the target opening range exhibits a linear change, and the linear deviation does not exceed a preset threshold.

[0017] The method for extending the characteristic curve of a water pump turbine provided by this invention has the following advantages compared with the prior art:

[0018] 1) This method only uses the comprehensive characteristic curve of the turbine under the operating conditions provided by the manufacturer. Through digital processing and equivalent point conversion, it can obtain the pump unit flow rate and pump unit torque data. It realizes the expansion from single operating condition data to multi-operating condition data, provides input parameters for multi-operating condition digital simulation of pump turbine, and solves the problem that manufacturers usually only provide turbine operating condition data, which makes it impossible to perform multi-operating condition digital simulation.

[0019] 2) Based on similarity theory and the principle of energy conservation, this method establishes a physical mechanism relationship between turbine and pump operating conditions using the equivalent point transformation method. It estimates the unit flow rate of the pump through a linear proportional relationship, avoiding reliance on a large number of experimental tests or complex numerical calculations. The method is simple and has high computational efficiency, which can meet the digital simulation needs of preliminary scheme design in engineering applications. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the method for expanding the characteristic curve of a water pump and turbine in an embodiment of the present invention;

[0023] Figure 2 This diagram shows the unit flow rate characteristic curve of the water turbine in an embodiment of the present invention.

[0024] Figure 3 This diagram shows the unit torque characteristic curve of the water turbine in an embodiment of the present invention.

[0025] Figure 4 This diagram shows the unit flow rate characteristic curve of the water pump in an embodiment of the present invention.

[0026] Figure 5 This diagram shows the characteristic curve of the unit torque of the water pump in an embodiment of the present invention. Detailed Implementation

[0027] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0029] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] Reference Figure 1 This embodiment provides a method for extending the characteristic curve of a water pump turbine, including steps S1 to S3.

[0031] S1. Obtain the comprehensive characteristic curves of the turbine under multiple opening conditions, and obtain the values ​​of unit flow rate and efficiency of the turbine at different unit speeds through image digitization processing; and generate the turbine unit flow rate characteristic curve based on the correspondence between unit speed and turbine unit flow rate at different opening degrees.

[0032] It is easy to understand that the comprehensive characteristic curve is usually provided directly by the manufacturer. Its vertical axis is the unit speed and the horizontal axis is the unit flow rate. There are multiple flow rate curves corresponding to different opening degrees in the quadrant. In addition to the flow rate curve, there is also an efficiency curve, and each efficiency curve shows the efficiency value. The image can be digitized using image processing software.

[0033] Specifically, coordinate points corresponding to each guide vane opening are extracted from the comprehensive characteristic curve to obtain data tables of unit flow rate and efficiency at different guide vane openings and unit speeds. Based on these data tables, for different guide vane openings, unit flow rate characteristic curves of the turbine are generated with unit speed as the abscissa and turbine unit flow rate as the ordinate, such as... Figure 2 As shown.

[0034] Specifically, the aforementioned target opening range must meet the following requirements: the turbine unit flow characteristic curve obtained from the comprehensive characteristic curve based on the target opening range must exhibit a linear change, and the linear deviation must not exceed a preset threshold.

[0035] It should be noted that different models of water pumps and turbines have different characteristics, so the preset threshold should be determined according to the actual situation, generally corresponding to small to medium opening conditions. This is because at small to medium openings, the unit flow characteristic curve of the water pump and turbine changes gently and can be approximated as a straight line; however, in the larger opening range, the unit flow characteristic curve of the water pump and turbine changes more significantly and cannot be approximated as a straight line; this method is based on linear proportional calculation and is suitable for curves that can be approximated as linear.

[0036] S2. Based on the equivalent point transformation method, estimate the unit flow rate of the water pump under the same unit speed and efficiency; and generate the unit flow rate characteristic curve of the water pump based on the correspondence between unit speed and unit flow rate.

[0037] It's easy to understand that a water pump and a water turbine are two opposite operating modes of the same machine. Based on similarity theory and the principle of energy conservation, at the same unit speed, there is an approximate relationship between the operating parameters of the highest efficiency point or other equivalent points of the water pump and water turbine operating conditions. The equivalent point conversion method can be used to estimate the characteristics of the water pump operating condition. According to the principle of the equivalent point conversion method, for any operating point on the comprehensive characteristic curve of the water turbine operating condition, at the same unit speed and the same efficiency, the energy exchange relationship between the work done by the water flow on the blades and the work done by the blades on the water flow is reversible. Based on the above equivalent point conversion relationship, for each guide vane opening and operating point at different unit speeds, the unit flow rate at the corresponding point of the water pump operating condition is obtained. Based on the water pump unit flow rate calculated at each guide vane opening, a water pump unit flow rate characteristic curve is generated with unit speed as the abscissa and water pump unit flow rate as the ordinate, as shown below. Figure 4 As shown.

[0038] Specifically, the unit flow rate of the water pump is estimated using the following formula:

[0039] ;

[0040] in, This indicates the unit flow rate of the water pump. This indicates the unit flow rate of the water turbine.

[0041] The above formula takes into full account that in actual scenarios, the flow rate absorbed by the pump is slightly greater than the flow rate emitted by the turbine, making the estimation results more consistent with the actual situation.

[0042] S3. Based on the unit flow characteristic curve and efficiency of the water turbine, calculate the unit torque of the water turbine, and generate the unit torque characteristic curve of the water turbine based on the correspondence between unit speed and unit torque of the water turbine; based on the unit flow characteristic curve and efficiency of the water pump, calculate the unit torque of the water pump, and generate the unit torque characteristic curve of the water pump based on the correspondence between unit speed and unit torque of the water pump.

[0043] Specifically, the unit torque of the turbine and the unit torque of the pump are calculated using the following formula:

[0044] ;

[0045] in, This represents the unit torque of a water turbine or the unit torque of a water pump. Indicates the specific gravity of water. This indicates the unit flow rate of the water turbine or the unit flow rate of the water pump. Indicates efficiency. Indicates unit rotational speed.

[0046] The derivation of this formula will be explained in detail below.

[0047] 1) This formula is derived from 7 formulas, as follows.

[0048] Formula 1: Power-Torque Formula

[0049] ;

[0050] in, Indicates torque, This represents the unit's power; this represents the unit's angular velocity.

[0051] Formula 2: Angular velocity - rotational speed formula

[0052] ;

[0053] in, Indicates angular velocity, Indicates rotational speed;

[0054] Formula 3: Power output formula of water turbine

[0055] ;

[0056] in, Indicates unit power, nominal diameter of the impeller, and head;

[0057] Formula 4: Rotational Speed ​​Formula

[0058] ;

[0059] in, Indicates rotational speed. Indicates unit rotational speed;

[0060] Formula 5: Power-Flow Formula

[0061] ;

[0062] in, Indicates the specific gravity of water. Indicates flow rate. Indicates efficiency;

[0063] Formula 6: Unit Flow Rate Formula

[0064] ;

[0065] in, Indicates unit flow rate;

[0066] Formula 7: Formula for unit torque

[0067] ;

[0068] in, This represents the unit torque.

[0069] 2) The derivation process is as follows.

[0070] Combining formulas 1 to 4, we can obtain:

[0071] ;

[0072] Combining formulas 3, 5, and 6, we can obtain:

[0073] ;

[0074] Combining the first two equations with Formula 7, we can obtain:

[0075] .

[0076] For the turbine operating condition, substitute the turbine's unit flow rate and efficiency corresponding to each point on the turbine's unit flow rate characteristic curve into the above relationship to calculate the turbine's unit torque; then, using unit speed as the abscissa and turbine unit torque as the ordinate, generate the turbine's unit torque characteristic curve, as shown below. Figure 3 As shown.

[0077] For the pump operating condition, substitute the pump's unit flow rate and efficiency corresponding to each point on the pump's unit flow rate characteristic curve into the above relationship to calculate the pump's unit torque; then, generate the pump's unit torque characteristic curve by plotting unit speed as the abscissa and pump unit torque as the ordinate, as shown below. Figure 5 As shown.

[0078] During digital simulation, the aforementioned turbine unit flow characteristic curve, turbine unit torque characteristic curve, pump unit flow characteristic curve, and pump unit torque characteristic curve can be used as inputs.

[0079] The above are merely specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for extending the characteristic curve of a water pump turbine, characterized in that, Includes the following steps: S1. Obtain the comprehensive characteristic curve of the turbine operating conditions within the target opening range, and obtain the values ​​of turbine unit flow rate and efficiency at different unit speeds through image digitization processing; and generate turbine unit flow rate characteristic curve based on the correspondence between unit speed and turbine unit flow rate at different openings. S2. Based on the equivalent point transformation method, estimate the unit flow rate of the water pump under the same unit speed and efficiency; and based on the correspondence between the unit speed and the unit flow rate of the water pump, generate the unit flow rate characteristic curve of the water pump. S3. Based on the turbine's unit flow characteristic curve and efficiency, calculate the turbine's unit torque, and based on the correspondence between the unit speed and the turbine's unit torque, generate the turbine's unit torque characteristic curve; Based on the pump's unit flow rate characteristic curve and efficiency, the pump's unit torque is calculated, and based on the correspondence between the unit rotational speed and the pump's unit torque, a pump unit torque characteristic curve is generated.

2. The method for expanding the characteristic curve of a water pump-turbine according to claim 1, characterized in that, In step S2, the unit flow rate of the water pump is estimated using the following formula: ； in, This indicates the unit flow rate of the water pump. This indicates the unit flow rate of the water turbine.

3. The method for expanding the characteristic curve of a water pump-turbine according to claim 1, characterized in that, In step S3, the unit torque of the turbine and the unit torque of the pump are calculated using the following formula: ； in, This represents the unit torque of a water turbine or the unit torque of a water pump. Indicates the specific gravity of water. This indicates the unit flow rate of the water turbine or the unit flow rate of the water pump. Indicates efficiency. Indicates unit rotational speed.

4. The method for extending the characteristic curve of a water pump turbine according to any one of claims 1 to 3, characterized in that, In step S1, the target opening range must satisfy the following: the turbine unit flow characteristic curve obtained based on the comprehensive characteristic curve of the target opening range changes linearly, and the linear deviation does not exceed a preset threshold.

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