Calculation method for maximum runaway rotating speed of bulb tubular turbine

Abstract

The invention relates to the field of bulb through-flow turbines in hydropower stations, discloses a method for calculating the maximum runaway speed of a bulb through-flow turbine, and solves the problems that in the prior art, a scheme for calculating the maximum runaway speed of the bulb through-flow turbine under the working condition that guide vanes and runner blades are not in joint cooperation is inaccurate in calculation; the difference between the actual value and the actual value is large, and the requirement for hydropower engineering construction of a new device with a bulb tubular water turbine generator set cannot be met. According to the method, data of a large number of bulb tubular hydroelectric generating sets which run well at home and abroad for recent 30 years are collected and arranged, and then a nonlinear regression method is adopted to fit a complex relation among the data, so that a calculation formula of the maximum runaway rotating speed under the non-joint working condition is obtained. In practical application, the maximum runaway rotating speed under the non-joint working condition can be quickly and accurately calculated by substituting the rated specific rotating speed value, the maximum water head value and the nominal diameter value of the rotating wheel of the bulb tubular turbine with the maximum runaway rotating speed to be calculated into the maximum runaway rotating speed calculation formula.

Description

Technical Field

[0001] This invention relates to the field of bulb turbines in hydropower stations, and specifically to a method for calculating the maximum runaway speed of a bulb turbine. Background Technology

[0002] A water turbine is a machine in a hydropower station that converts the mechanical energy of water flow into the mechanical energy of a runner, enabling the runner and main shaft to overcome various resistances and drive the turbine generator to operate continuously. It is known as the "heart" of a hydropower station. The rational selection of its parameters is crucial to the initial investment of hydropower projects and the safe and reliable operation of hydropower stations after commissioning. It is one of the core contents that need to be studied in the construction of hydropower projects.

[0003] The maximum runaway speed of a hydroelectric turbine refers to the highest steady-state speed that the turbine can reach within a specified operating head range when it is in an uncontrolled state and the shaft end load torque is zero. It is an important technical parameter of the turbine. The maximum runaway speed of a bulb turbine occurs under both coordinated and non-coordinated operating conditions of the guide vanes and runner blades. The maximum runaway speed is the highest under the non-coordinated operating condition of the guide vanes and runner blades, and its impact on the safety of the unit is the most significant.

[0004] Current national standards have specific requirements for the runaway performance of water turbines and their associated generators: 1. Clause 4.2.1.7 of the "Basic Technical Conditions for Hydropower Turbines" (GB / T 15468-2020) stipulates: The permissible continuous operating time of the turbine at its maximum runaway speed should not be less than the permissible runaway time of the matching turbine generator, and the rotating parts of the turbine should not be subjected to harmful deformation or collision and damage.

[0005] 2. Section 9.2 of "Basic Technical Requirements for Hydropower Generators" (GB / T 7894-2023) stipulates: The hydro-generator should be able to withstand the maximum design speed without any harmful deformation or damage. The maximum design speed duration is 5 minutes. The maximum design speed of the hydro-generator corresponds to the highest runaway speed of the turbine. The structural rigidity of the hydro-generator is usually designed based on its maximum design speed; exceeding the maximum design speed for too long will lead to damage to components such as the rotor and main shaft.

[0006] Therefore, accurately calculating the maximum runaway speed of a water turbine is extremely important for the structural rigidity design of water turbines and hydro-generators, as well as for ensuring their long-term safe and reliable operation.

[0007] In the existing technology, there are two main methods for calculating the maximum runaway speed of a bulb turbine under non-coordinated operation of the guide vanes and runner blades: Firstly, if the head, power, and other parameters of the bulb turbine in a new hydropower project are the same as or close to those of an already designed and manufactured turbine, then the maximum runaway speed of the bulb turbine can be estimated using the existing model runner parameters and runaway characteristic curves. However, because this method is based on existing model data, it is generally difficult to conduct comprehensive and in-depth experimental research on the runner characteristics due to the limitations of the technology available at the time. This is especially true for large and medium-sized hydropower projects or those with special requirements, which typically necessitate the development and fabrication of new models using new technologies such as CFD and model testing, based on the specific conditions and operational requirements of the project.

[0008] Secondly, when suitable model data is unavailable, the maximum runaway speed of the bulb turbine is estimated using the statistical range of the maximum runaway speed in the "Hydropower Station Electromechanical Design Manual" (Hydraulic Machinery) published by the Water Resources and Electric Power Press in 1983 (i.e., the maximum runaway speed of the bulb turbine under non-coordinated operation of the guide vanes and runner blades is 2.4 to 2.6 times the rated speed). This estimation method only provides a range of values, and it is unclear how to select the appropriate value in actual engineering. Furthermore, since the turbine parameter data used in this estimation method are from before the 1990s, it does not take into account the data of numerous bulb turbines developed in the large-scale hydropower development over the past 30 years, and thus has certain limitations due to its historical context.

[0009] With the improvement of design and R&D capabilities, as well as the continuous development and application of new technologies, materials, processes, and structures, the hydraulic losses and bearing mechanical friction losses that affect the maximum runaway speed of bulb turbines are showing a downward trend. In recent years, the actual value of the maximum runaway speed of bulb turbines under non-coordinated operation of guide vanes and runner blades differs significantly from the maximum runaway speed value estimated using existing methods, which cannot meet the construction needs of new hydropower projects with bulb turbine generator sets. Summary of the Invention

[0010] The technical problem to be solved by this invention is to provide a method for calculating the maximum runaway speed of a bulb turbine, which solves the problem that the calculation scheme of the maximum runaway speed of a bulb turbine under non-coordinated operation of the guide vanes and runner blades in the prior art is inaccurate, has a large deviation from the actual value, and cannot meet the construction needs of hydropower projects with bulb turbine generator sets.

[0011] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: The method for calculating the maximum runaway speed of a bulb turbine includes the following steps: S1. Collect and organize data on bulb turbine generator sets that have been put into operation at home and abroad, and establish a basic database of bulb turbine parameter samples. The parameter samples in the database include: maximum head, rated head, rated power, rated speed, rated specific speed, nominal runner diameter, and maximum runaway speed under non-coupling conditions. The formula for calculating the rated specific speed is as follows: ; in, The rated specific speed of the turbine, in units of ; This refers to the rated speed of the water turbine, expressed in r / min. This refers to the rated power of the water turbine, measured in kW. The rated head of the water turbine is expressed in meters (m). S2. Based on the data in the bulb turbine parameter sample database, a nonlinear regression method is used to fit the relationship between the maximum runaway speed and the rated specific speed, maximum head, and nominal runner diameter under non-coordinated operating conditions, thus obtaining the calculation formula for the maximum runaway speed of the bulb turbine under non-coordinated operating conditions of the guide vanes and runner blades: ; in, This represents the maximum runaway speed of the turbine, expressed in r / min. The rated specific speed of the turbine, in units of ; This represents the maximum head of the water turbine, measured in meters (m). This is the nominal diameter of the turbine runner, in meters (m). S3. For the bulb turbine with the highest runaway speed to be calculated, the rated specific speed of the turbine is calculated by substituting the rated speed, rated power and rated head of the bulb turbine into the formula for calculating the rated specific speed of the turbine. S4. For the bulb turbine whose maximum runaway speed is to be calculated, the maximum runaway speed calculation formula is used. The rated specific speed, maximum head and nominal runner diameter of the bulb turbine are substituted into the formula to calculate the maximum runaway speed of the bulb turbine under the condition that the guide vanes and runner blades are not coordinated.

[0012] Furthermore, in step S2, the method of fitting the relationship between the maximum runaway speed and the rated specific speed, maximum head, and nominal diameter of the runner under non-coordinated operating conditions using a nonlinear regression method includes: Using rated specific speed, maximum head, and nominal runner diameter as independent variables, and the maximum runaway speed under non-coordinated operating conditions as the dependent variable, a nonlinear regression method was used to fit the data on maximum runaway speed, rated specific speed, maximum head, and nominal runner diameter under non-coordinated operating conditions from the basic database of bulb turbine parameter samples.

[0013] The beneficial effects of this invention are: (1) This scheme has established a comprehensive, complete and effective basic database of bulb turbine parameters by collecting and organizing data on well-run bulb turbine generator sets from home and abroad over the past 30 years. This provides solid data support for the derivation of the formula for calculating the maximum runaway speed. The data covers information on new turbines accumulated in the large-scale hydropower development in recent years and can reflect the impact of new technologies, new materials, new processes and new structures on turbine performance.

[0014] (2) Based on the above database, the formula for calculating the maximum runaway speed of the bulb turbine under non-coordinated operation of the guide vane and runner blades is obtained by fitting the nonlinear regression method. This formula comprehensively considers the correlation between key parameters such as rated specific speed, maximum head, and nominal runner diameter and the maximum runaway speed, and overcomes the limitations caused by relying on old model data or general value range in the existing technology.

[0015] (3) The maximum runaway speed obtained by the calculation method of this scheme has a small deviation from the actual value, and the calculation accuracy can meet the engineering requirements. It can quickly and accurately calculate the maximum runaway speed of the bulb turbine under non-coupling conditions.

[0016] (4) This method does not rely on specific existing model runner parameters and is applicable regardless of whether there are identical or similar turbine models. It improves the quality and efficiency of the demonstration work of bulb turbine and reduces costs. It can better meet the construction needs of new hydropower projects equipped with bulb turbine generator sets and provides strong technical support for the structural rigidity design and long-term safe and reliable operation of related equipment in hydropower projects. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the method for calculating the maximum runaway speed of the bulb-type turbine in this invention. Detailed Implementation

[0018] This invention aims to provide a method for calculating the maximum runaway speed of a bulb turbine, addressing the problem that existing calculation methods for the maximum runaway speed of bulb turbines under non-coordinated operation of the guide vanes and runner blades are inaccurate, deviating significantly from actual values, and failing to meet the needs of new hydropower projects with bulb turbine generator sets. The core idea is to collect and organize data from a large number of well-operated bulb turbine generator sets from both domestic and international sources over the past 30 years, including maximum head, rated head, rated power, rated speed, rated specific speed, nominal runner diameter, and maximum runaway speed under non-coordinated operation. Then, a nonlinear regression method is used to fit the complex relationships between these data, thereby obtaining a formula for calculating the maximum runaway speed of the bulb turbine under non-coordinated operation of the guide vanes and runner blades. In practical applications, by substituting the rated specific speed, maximum head, and nominal runner diameter of the bulb turbine into the formula for calculating the maximum runaway speed of the bulb turbine, the maximum runaway speed of the bulb turbine under non-coordinated operation of the guide vanes and runner blades can be calculated quickly and accurately.

[0019] In specific implementation, the calculation method flow for the maximum runaway speed of the bulb turbine provided by this invention is as follows: Figure 1 It includes the following steps: S1. Collect and organize parameter data of bulb turbines and establish a parameter sample database: This step involves collecting and organizing data from a large number of well-functioning bulb turbine generator sets from both domestic and international sources over the past 30 years, establishing a comprehensive, complete, and effective database of bulb turbine parameter samples. The turbine parameter data collected here mainly includes the name / country of the hydropower station, maximum head, rated head, rated power, rated speed, rated specific speed, nominal runner diameter, and maximum runaway speed under non-coupling conditions, etc.

[0020] S2. Based on the sample parameters, the formula for calculating the maximum runaway speed of the bulb turbine is obtained using a nonlinear regression method: In this step, based on the data in the bulb turbine parameter sample database, a nonlinear regression method is used to obtain the calculation formula for the maximum runaway speed of the bulb turbine under non-cooperative operating conditions of the guide vanes and runner blades. That is, by using the nonlinear regression method, the complex relationship between the maximum runaway speed of the turbine under non-cooperative operating conditions and the rated specific speed, maximum head and nominal runner diameter of the turbine in the bulb turbine parameter sample database is fitted, thereby obtaining the calculation formula for the maximum runaway speed of the bulb turbine under non-cooperative operating conditions of the guide vanes and runner blades.

[0021] S3. Calculate the rated specific speed of the bulb turbine using the formula for calculating the rated specific speed of a water turbine: In this step, for the bulb turbine whose maximum runaway speed is to be calculated, the formula for calculating the rated specific speed of the turbine is used. The rated speed, rated power and rated head of the bulb turbine are substituted into the formula to calculate the rated specific speed of the bulb turbine.

[0022] S4. The maximum runaway speed of the bulb turbine to be calculated is obtained using the formula for calculating the maximum runaway speed of a bulb turbine: In this step, for the bulb turbine whose maximum runaway speed is to be calculated, the formula for calculating the maximum runaway speed of the bulb turbine obtained in step S2 is used. By substituting the rated specific speed, maximum head, and nominal runner diameter of the bulb turbine whose maximum runaway speed is to be calculated, the maximum runaway speed of the bulb turbine under non-coordinated operation of the guide vanes and runner blades can be quickly and accurately calculated.

[0023] This embodiment takes the calculation of the maximum runaway speed of a bulb turbine as an example, and the implementation process is as follows: (1) First, by collecting and organizing a large amount of well-run bulb turbine generator data from domestic and foreign sources over the past 30 years, a comprehensive, complete and effective basic database of bulb turbine parameter samples was established. Some of the parameter samples in the database are shown in Table 1.

[0024] Table 1. Sample Parameters from the Basic Database of Bulb-type Axial-flow Turbine Parameters (2) Next, based on the parameter samples in the basic database of bulb turbine parameters, the relationship between the highest runaway speed and the rated specific speed, maximum head and nominal diameter of the runner under non-coordinated operation conditions of the bulb turbine is fitted by nonlinear regression method, and the formula for calculating the highest runaway speed of the bulb turbine under non-coordinated operation conditions of the guide vanes and runner blades is obtained: ; (3) Then, for the bulb turbine with the highest runaway speed to be calculated, substitute its rated speed, rated power and rated head into the formula for calculating the rated specific speed to calculate the rated specific speed of the bulb turbine.

[0025] (4) Finally, for the bulb turbine whose maximum runaway speed is to be calculated, substitute its rated specific speed, maximum head and runner nominal diameter into the formula for calculating the maximum runaway speed, and the maximum runaway speed of the bulb turbine under the condition of non-coordinated operation of the guide vane and runner blades can be calculated.

[0026] To verify the accuracy of the formula for calculating the maximum runaway speed of the bulb turbine proposed in this embodiment, the rated specific speed, maximum head, and nominal runner diameter values ​​from Table 1 above will be substituted into the formula for calculating the maximum runaway speed of the bulb turbine proposed in this embodiment. The maximum runaway speed of the bulb turbine will then be calculated, and the error rate between the calculated maximum runaway speed and the actual value will be calculated.

[0027] Using the calculation formula proposed in this embodiment, the calculation results of the maximum runaway speed of the bulb turbine under the non-coordinated operation of the guide vane and runner blades are shown in Table 2.

[0028] Table 2. Calculation results of the maximum runaway speed of the bulb turbine using the calculation formula of this embodiment. Based on the calculation results in Table 2 above, it can be seen that: The calculation formula in this embodiment has a small error rate, only -3.37% to 3.24%, and the calculation accuracy meets the requirements of engineering calculation. This means that the calculation formula in this embodiment can be used to calculate the maximum runaway speed of a bulb turbine under non-coordinated operation of the guide vane and runner blades, and can better meet the construction needs of hydropower projects with new bulb turbine generator sets.

[0029] Although embodiments of the present invention have been described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, and all such changes and alterations shall not depart from the protection scope of the present invention.

Claims

1. A method for calculating the maximum runaway speed of a bulb turbine, characterized in that, Includes the following steps: S1. Collect and organize data on bulb turbine generator sets that have been put into operation at home and abroad, and establish a basic database of bulb turbine parameter samples. The parameter samples in the database include: maximum head, rated head, rated power, rated speed, rated specific speed, nominal runner diameter, and maximum runaway speed under non-coupling conditions. The formula for calculating the rated specific speed is as follows: ； in, The rated specific speed of the turbine, in units of ; This refers to the rated speed of the water turbine, expressed in r / min. This refers to the rated power of the water turbine, measured in kW. The rated head of the water turbine is expressed in meters (m). S2. Based on the data in the bulb turbine parameter sample database, a nonlinear regression method is used to fit the relationship between the maximum runaway speed and the rated specific speed, maximum head, and nominal runner diameter under non-coordinated operating conditions, thus obtaining the calculation formula for the maximum runaway speed of the bulb turbine under non-coordinated operating conditions of the guide vanes and runner blades: ； in, This represents the maximum runaway speed of the turbine, expressed in r / min. The rated specific speed of the turbine, in units of ; This represents the maximum head of the water turbine, measured in meters (m). This is the nominal diameter of the turbine runner, in meters (m). S3. For the bulb turbine with the highest runaway speed to be calculated, the rated specific speed of the turbine is calculated by substituting the rated speed, rated power and rated head of the bulb turbine into the formula for calculating the rated specific speed of the turbine. S4. For the bulb turbine whose maximum runaway speed is to be calculated, the maximum runaway speed calculation formula is used. The rated specific speed, maximum head and nominal runner diameter of the bulb turbine are substituted into the formula to calculate the maximum runaway speed of the bulb turbine under the condition that the guide vanes and runner blades are not coordinated.

2. The method for calculating the maximum runaway speed of a bulb turbine as described in claim 1, characterized in that, In step S2, the step of fitting the relationship between the maximum runaway speed and the rated specific speed, maximum head, and nominal diameter of the runner under non-coordinated operating conditions using a nonlinear regression method includes: Using rated specific speed, maximum head, and nominal runner diameter as independent variables, and the maximum runaway speed under non-coordinated operating conditions as the dependent variable, a nonlinear regression method was used to fit the data on maximum runaway speed, rated specific speed, maximum head, and nominal runner diameter under non-coordinated operating conditions from the basic database of bulb turbine parameter samples.

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