A method for calculating the variable working condition of equivalent steam distribution stage group of a steam turbine

Abstract

The application provides a method for calculating the variable working condition of equivalent steam distribution stage group of a steam turbine unit, which regards the main steam valve of the steam turbine to the first-stage steam extraction port as an equivalent steam distribution stage group, regards the main steam parameter as the stage front parameter of the equivalent steam distribution stage group, and regards the first-stage steam extraction parameter as the stage rear parameter of the equivalent steam distribution stage group; the "total valve position instruction-equivalent steam distribution stage group flow correction coefficient" curve and the "total valve position instruction-equivalent steam distribution stage group efficiency" curve are established according to the test results of the turbine valve flow characteristics or the simulation calculation results of the overall variable working condition of the steam turbine distribution end; the variable working condition calculation of the steam turbine distribution end characteristics containing the total valve position instruction information is realized by setting the total valve position instruction and according to the "total valve position instruction-equivalent steam distribution stage group flow correction coefficient" curve and the "total valve position instruction-equivalent steam distribution stage group efficiency" curve; and the method is suitable for nozzle steam distribution unit, pure throttle steam distribution unit and throttle steam distribution unit with overload steam supplement.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of steam turbine equivalent steam distribution level group variable condition calculation method, belong to steam turbine operation technical field. BACKGROUND

[0002] For nozzle steam distribution steam turbine, its regulating stage is divided into several independent nozzle arc segments; Generally, each regulating valve controls the steam admission of a nozzle arc segment. When the load changes, several regulating valves are opened or closed in turn to change the flow area of the regulating stage to control the total steam admission of the steam turbine. Assuming that the steam turbine is arranged with CV1, CV2, CV3 and CV4, a total of 4 regulating valves. In actual operation, to improve the safety of the unit operation, the nozzle steam distribution mode is often designed as "throttle-nozzle mixed steam distribution mode", that is, CV1 and CV2 are opened synchronously at low load, and CV3 and CV4 are sequentially opened with the increase of load (CV1 / 2→CV3→CV4).

[0003] In order to improve the flow performance of steam and increase the efficiency of the stage, the moving blades and the static blades of the regulating stage are designed to have a small amount of reaction, and the value of the reaction changes with the working condition, so the pressure after the nozzle is not equal to the pressure after the moving blade. The variable condition calculation of the regulating stage is one of the most common problems in the thermal calculation of the nozzle steam distribution steam turbine. In the variable condition calculation of the regulating stage, two parts of the steam flow must be discussed respectively: one is the steam flow through the fully open regulating valve; the other is the steam flow through the partially open regulating valve. Due to the complexity of the thermal calculation of the regulating stage under variable condition, the general characteristic curve of the regulating stage provided by the manufacturer is usually used to obtain the relevant data by looking up the graph, and then the corresponding calculation is carried out.

[0004] For the regulating valve of the steam turbine, it belongs to the quick-opening type regulating valve, and its flow characteristic (numerically represented as the function relationship between stroke and steam flow) has typical nonlinear characteristics; for the steam regulating valve with determined sleeve structure and installation stroke, the regulating valve stroke, as a necessary state parameter of all steam turbine regulating valves on site, has dual attributes of geometric meaning and thermodynamic meaning; the size of the regulating valve stroke directly affects the variable load thermal economy characteristic, variable pressure thermal economy characteristic and flow characteristic of the steam turbine.

[0005] In operation, the total valve position command is a necessary coordinated control and state parameter of the steam turbine generator unit, which has no strict thermodynamic meaning, but has important practical application value in measuring and characterizing the steam turbine variable load thermal economic characteristics, constant power variable pressure operation thermal economic characteristics, and governing valve flow characteristics. The patent ZL202011116140.7, a steam turbine steam distribution end simulation calculation method, provides a comprehensive variable condition simulation calculation method for the steam turbine steam distribution end. However, due to the complexity of the governing valve characteristics and the regulating stage characteristics, the variable condition calculation of the nozzle steam distribution steam turbine is not only time-consuming and laborious, but also extremely tedious. Moreover, there is inevitably a certain deviation between the simulation calculation results and the actual operation characteristics of the steam turbine steam distribution end. Undoubtedly, the calculation effect will be better if the characteristic curves required for the variable condition calculation of the steam distribution end are extracted through field tests.

[0006] Therefore, the present application provides a steam turbine equivalent steam distribution stage group variable condition calculation method according to the principle of the steam turbine, realizes the simplified calculation of the variable condition characteristics of the steam turbine unit steam distribution end containing the total valve position command information, and is suitable for various types of steam turbine units such as nozzle steam distribution (sequential valve and single valve valve control mode), pure throttling steam distribution, and throttling steam distribution with overload steam supplement. SUMMARY

[0007] The purpose of the present application is to provide a steam turbine equivalent steam distribution stage group variable condition calculation method to simplify the variable condition calculation of the steam turbine steam distribution end characteristics.

[0008] The technical scheme realized by the present application is as follows: a steam turbine equivalent steam distribution stage group variable condition calculation method, which regards the main steam valve of the steam turbine to the first stage extraction port as an equivalent steam distribution stage group, regards the main steam parameters as the stage front parameters of the equivalent steam distribution stage group, and regards the first stage extraction parameters as the stage rear parameters of the equivalent steam distribution stage group; according to the test results of the steam turbine governing valve flow characteristics or the simulation calculation results of the comprehensive variable condition of the steam turbine steam distribution end, a "total valve position command-equivalent steam distribution stage group flow correction coefficient" curve and a "total valve position command-equivalent steam distribution stage group efficiency" curve are established; in the application, by setting the total valve position command, the variable condition calculation of the steam turbine steam distribution end characteristics containing the total valve position command information is realized according to the "total valve position command-equivalent steam distribution stage group flow correction coefficient" curve and the "total valve position command-equivalent steam distribution stage group efficiency" curve.

[0009] A steam turbine equivalent steam distribution stage group variable condition calculation method, comprising the following steps:

[0010] Step 1: regarding the main steam valve of the steam turbine to the first stage extraction port as an equivalent steam distribution stage group, regarding the main steam parameters as the stage front parameters of the equivalent steam distribution stage group, and regarding the first stage extraction parameters as the stage rear parameters of the equivalent steam distribution stage group;

[0011] According to the test results of the turbine governing valve flow characteristics or the simulation calculation results of the overall variable working condition of the turbine steam distribution end, the total valve position command φ = 100% is taken as the reference working condition, and the related parameters are substituted into formula (1) to calculate the flow factor under the working condition.

[0012]

[0013] In the formula, M0 is the flow factor under the reference working condition; p 10 , p 20 are the equivalent steam distribution stage group front and back pressures under the reference working condition; v 10 is the equivalent steam distribution stage group front specific volume under the reference working condition.

[0014] When the total valve position command 50% < φ < 100%, the related parameters under different total valve position command working conditions are substituted into formula (2) at certain intervals to calculate the flow factor under the working condition.

[0015]

[0016] In the formula, M1 is the flow factor under the different total valve position command working condition; p 11 , p 21 are the equivalent steam distribution stage group front and back pressures under the different total valve position command working condition; v 11 is the equivalent steam distribution stage group front specific volume under the different total valve position command working condition.

[0017] The flow factor M0 under the reference working condition is taken as the unit reference value, the flow factor M1 under the different total valve position command working condition is divided by the flow factor M0 to obtain the equivalent steam distribution stage group flow correction coefficient μ = M1 / M0 under the different total valve position command φ; that is, the "total valve position command φ-equivalent steam distribution stage group flow correction coefficient μ" curve can be obtained.

[0018] Step 2: According to the test results of the turbine governing valve flow characteristics or the simulation calculation results of the overall variable working condition of the turbine steam distribution end, the main steam parameters are taken as the front stage parameters of the equivalent steam distribution stage group, and the first stage extraction steam parameters are taken as the back stage parameters of the equivalent steam distribution stage group, and the efficiency η of the equivalent steam distribution stage group under the different total valve position command φ is calculated, that is, the "total valve position command φ-equivalent steam distribution stage group efficiency η" curve can be obtained.

[0019] Step 3: In application, the main steam valve of the turbine up to the first extraction port is considered as an equivalent steam distribution stage group. The main steam parameters are used as the pre-stage parameters of this equivalent steam distribution stage group, and the first extraction parameters are used as the post-stage parameters of this equivalent steam distribution stage group. For the equivalent steam distribution stage group flow rate and the equivalent steam distribution stage group pre-pressure, one of them is usually known, and the other is a quantity to be determined. At this time, by setting the total valve position command φ, the corresponding equivalent steam distribution stage group flow rate correction coefficient μ can be calculated by interpolation according to the curve of "total valve position command φ - equivalent steam distribution stage group flow rate correction coefficient μ"; then, the mutual solution between the equivalent steam distribution stage group flow rate or the equivalent steam distribution stage group pre-pressure can be realized by using equation (3).

[0020]

[0021] In the formula: G0 is the equivalent steam distribution stage flow rate under the reference operating condition; G1 is the equivalent steam distribution stage flow rate under the total valve position command φ operating condition; μ is the correction coefficient for the equivalent steam distribution stage flow rate under the total valve position command φ operating condition. p′ 11 p′ 21 v′ represents the equivalent pre-stage and post-stage pressures of the steam distribution stage under the total valve position command φ condition. 11 The equivalent pre-stage specific volume of the steam distribution stage group under the operating condition of the total valve position command φ.

[0022] Step 4: In application, the enthalpy after the equivalent steam distribution stage is usually the quantity to be determined. At this time, the corresponding efficiency η of the equivalent steam distribution stage can be calculated by interpolation based on the curve of "total valve position command φ - equivalent steam distribution stage efficiency η" by setting the total valve position command φ; then, the enthalpy after the equivalent steam distribution stage can be solved by using the efficiency calculation formula (4).

[0023] h 21 =h 11 -η*(h 11 -h s21 Equation (4)

[0024] Where: h 21 The equivalent steam distribution stage enthalpy after the main valve position command φ under the operating condition; h 11 The equivalent enthalpy before the main steam distribution stage under the main valve position command φ condition; h s21 η is the isentropic enthalpy of the equivalent steam distribution stage under the total valve position command φ condition; η is the efficiency of the equivalent steam distribution stage under the total valve position command φ condition.

[0025] The beneficial effects of this invention are that it can relatively simply and efficiently realize various calculation and application functions such as the variable load thermal economic characteristics, variable pressure thermal economic characteristics, and flow characteristics of steam turbines containing total valve position command information; this invention not only has abundant experimental data, but also most realistically reflects the actual situation; it is applicable to nozzle steam distribution units (sequential valve and single valve control methods), pure throttling steam distribution units, and throttling steam distribution units with overload supplementary steam. Attached Figure Description

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0027] Figure 1 The figure is a schematic diagram of a steam turbine steam distribution end of an embodiment of the present application.

[0028] Figure 2 The figure is a schematic diagram of an equivalent steam distribution stage group of an embodiment of the present application.

[0029] Figure 3 The figure is a scatter plot of "total valve position instruction φ-equivalent steam distribution stage group flow correction coefficient μ" of an embodiment of the present application.

[0030] Figure 4 The figure is a scatter plot of "total valve position instruction φ-equivalent steam distribution stage group efficiency η" of an embodiment of the present application.

[0031] Figure 5 The figure is a comparison diagram of simplified simulation calculation of an equivalent steam distribution stage group and comprehensive variable condition simulation calculation of a steam turbine steam distribution end of an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the protection scope of the present application.

[0033] The specific embodiments of the present application are shown in the figures. The following will combine the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Figures 1-4

[0034] The unit in the embodiment is a certain ultra-supercritical 700MW grade steam turbine, and the unit is arranged with 4 groups of nozzle chambers and the same number of nozzles in each chamber. The embodiment only introduces the application under the sequential valve control mode (valve sequence is CV1 / 2-CV3-CV4), and is also applicable to the single-valve control mode of the nozzle steam distribution unit, the pure throttle steam distribution unit and the throttle steam distribution unit with overload steam supplement.

[0035] The equivalent steam distribution stage group variable condition calculation method of the steam turbine in the embodiment of the present application comprises the following steps:

[0036] ​Step 1: Based on the test results of the rated parameter turbine control valve flow characteristics or the simulation calculation results of the turbine distribution end under comprehensive variable operating conditions, the main steam parameters are used as the pre-stage parameters of the equivalent distribution stage group, and the first-stage extraction steam parameters are used as the post-stage parameters of the equivalent distribution stage group. In this embodiment of the invention, based on the test results of the rated parameter turbine control valve flow characteristics, the relevant characteristic curves of the equivalent stage group are extracted (see...). Figure 3 and Figure 4 Furthermore, comprehensive variable operating condition simulation calculations of the steam turbine distribution end are used to verify the accuracy of the invention (see...). Figure 5 ).

[0037] Using the total valve position command φ = 100% as the baseline operating condition, and substituting its relevant parameters into equation (1), the flow factor under this operating condition is calculated.

[0038]

[0039] Where: M0 is the flow factor under the baseline operating condition; p 10 p 20 The equivalent steam distribution stage group's pre-stage and post-stage pressures under baseline operating conditions; v 10 The equivalent steam distribution stage pre-stage specific volume under the baseline operating conditions.

[0040] When the total valve position command is 50% < φ < 100%, the relevant parameters under different total valve position command conditions are substituted into equation (2) at certain intervals to calculate the flow factor under that condition.

[0041]

[0042] Where: M1 is the flow factor under different total valve position command conditions; p 11 p 21 The equivalent pre-stage and post-stage pressures of the steam distribution stage under different main valve position command conditions; v 11 The equivalent pre-stage specific volume of the steam distribution stage group under different total valve position command conditions.

[0043] Using the flow factor M0 under the baseline operating condition as the per-unit reference value, divide the flow factor M1 under different total valve position command conditions by it to obtain the equivalent steam distribution group flow correction coefficient μ = M1 / M0 under different total valve position commands φ; a scatter plot of "total valve position command φ - equivalent steam distribution group flow correction coefficient μ" can then be obtained, as shown below. Figure 3 As shown. By Figure 3 It can be seen that, under the same total valve position command, the equivalent steam distribution stage flow correction coefficient obtained from the turbine constant pressure control valve flow characteristic test is consistent with the equivalent steam distribution stage flow correction coefficient obtained from the 600MW constant power variable pressure operation test of the turbine, confirming the rationality of the present invention. Using a clustering algorithm, the characteristic curve of "total valve position command φ – equivalent steam distribution stage flow correction coefficient μ" can be further obtained.

[0044] Step 2: According to the test results of the turbine governing valve flow characteristics or the simulation calculation results of the overall variable working condition of the turbine steam distribution end, the main steam parameters are taken as the parameters before the stage of the equivalent steam distribution stage group, and the first-stage extraction steam parameters are taken as the parameters after the stage of the equivalent steam distribution stage group. The efficiency η of the equivalent steam distribution stage group under different total valve position instructions φ is calculated, and a "total valve position instruction φ-equivalent steam distribution stage group efficiency η" scatter plot is obtained, as shown in Fig. 2. Figure 4 Figure 4 It can be seen from Fig. 2 that the equivalent steam distribution stage group efficiencies obtained from the turbine constant-power variable-pressure operation tests under different working conditions such as 600 MW, 560 MW, 460 MW and 340 MW tend to be consistent under the same total valve position instruction, which proves the rationality of the present application. With the help of clustering algorithm, the "total valve position instruction φ-equivalent steam distribution stage group efficiency η" characteristic curve can be further obtained.

[0045] Step 3: In application, one of the equivalent steam distribution stage group flow and the equivalent steam distribution stage group front pressure is usually known, and the other is to be solved. At this time, the total valve position instruction φ can be set, and the corresponding equivalent steam distribution stage group flow correction coefficient μ can be calculated according to the "total valve position instruction φ-equivalent steam distribution stage group flow correction coefficient μ" curve. Then, the mutual solving between the equivalent steam distribution stage group flow and the equivalent steam distribution stage group front pressure is realized by using formula (3).

[0046]

[0047] In the formula, G0 is the equivalent steam distribution stage group flow under the reference working condition; G1 is the equivalent steam distribution stage group flow under the total valve position instruction φ working condition; μ is the equivalent steam distribution stage group flow correction coefficient under the total valve position instruction φ working condition. 11 , p′ 21 are the equivalent steam distribution stage group front and back pressures under the total valve position instruction φ working condition; v′ 11 is the equivalent steam distribution stage group front specific volume under the total valve position instruction φ working condition.

[0048] Step 4: In application, the equivalent steam distribution stage group back enthalpy is usually to be solved. At this time, the total valve position instruction φ can be set, and the corresponding equivalent steam distribution stage group efficiency η can be calculated according to the "total valve position instruction φ-equivalent steam distribution stage group efficiency η" curve. Then, the equivalent steam distribution stage group back enthalpy is solved by using the efficiency calculation formula (4).

[0049] h 21 = h 11 - η * (h 11 - h s21 )——Formula (4)

[0050] In the formula, h 21 is the equivalent steam distribution stage group back enthalpy under the total valve position instruction φ working condition; h​11 The equivalent enthalpy before the main steam distribution stage under the operating condition of the main valve position command φ; h s21 η is the isentropic enthalpy of the equivalent steam distribution stage under the total valve position command φ condition; η is the efficiency of the equivalent steam distribution stage under the total valve position command φ condition.

[0051] Based on turbine principles, under the same total valve position command, since the throat area of ​​the regulating valve and the corresponding nozzle area of ​​the regulating stage remain constant, it can be assumed that when the pre-stage parameters of the equivalent steam distribution stage change, the flow rate passing through it meets the application conditions of the Flueger formula; simultaneously, the stage efficiency of the equivalent steam distribution stage also remains essentially constant. When the total valve position command changes, since the throat area of ​​the regulating valve or the corresponding nozzle area of ​​the regulating stage changes, the flow rate through the equivalent steam distribution stage obviously does not meet the application conditions of the Flueger formula; however, the Flueger formula can be corrected using the "total valve position command - equivalent steam distribution stage flow rate correction coefficient". The efficiency of the equivalent steam distribution stage can be determined through the "total valve position command - equivalent steam distribution stage efficiency" curve. Thus, the solution for the equivalent steam distribution stage flow rate and stage efficiency under varying operating conditions can be achieved.

[0052] Figure 5 The results of simplified simulation calculations of the equivalent steam distribution stage group and comprehensive variable operating condition simulation calculations of the turbine steam distribution end are presented. The figure shows the trend of unit heat consumption under different main steam pressures corresponding to different total valve position commands, while maintaining a generator power of 450MW. Figure 5 It can be seen that, under the 450MW operating condition, the unit has the lowest heat consumption and the best economic performance at the two valve points. Moreover, the simplified simulation calculation of the equivalent steam distribution stage group is close to the simulation calculation results of the comprehensive variable operating condition of the steam turbine distribution end. Thus, the accuracy of the present invention is verified.

[0053] The above provides a detailed description of the method for calculating the equivalent steam distribution stage group of a steam turbine under varying operating conditions. Specific examples in this embodiment illustrate the principle and implementation of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A method for variable condition calculation of equivalent steam distribution stage group of a steam turbine, characterized in that, The method regards the main steam valve and the first-stage extraction port as an equivalent steam distribution stage group, takes the main steam parameter as the stage front parameter of the equivalent steam distribution stage group, and takes the first-stage extraction parameter as the stage rear parameter of the equivalent steam distribution stage group; According to the test results of the turbine control valve flow characteristics or the simulation calculation results of the overall turbine steam distribution end, the "total valve position instruction-equivalent steam distribution stage group flow correction coefficient" curve and the "total valve position instruction-equivalent steam distribution stage group efficiency" curve are established; in the application, by setting the total valve position instruction, the variable condition calculation of the turbine steam distribution end characteristics containing the total valve position instruction information is carried out according to the "total valve position instruction-equivalent steam distribution stage group flow correction coefficient" curve and the "total valve position instruction-equivalent steam distribution stage group efficiency" curve; Specifically, the following steps are included: Step 1: The main steam valve and the first-stage extraction port are regarded as an equivalent steam distribution stage group, the main steam parameter is taken as the stage front parameter of the equivalent steam distribution stage group, and the first-stage extraction parameter is taken as the stage rear parameter of the equivalent steam distribution stage group; According to the test results of the turbine control valve flow characteristics or the simulation calculation results of the overall turbine steam distribution end, the total valve position instruction φ = 100% is taken as the reference condition, and the related parameters are substituted into formula (1) to calculate the flow factor under the condition; - formula (1) In the formula: is the flow factor under the reference operating condition; , is the equivalent steam distribution stage group pre-stage and post-stage pressure under the reference operating condition; is the equivalent steam distribution stage group pre-stage specific volume under the reference operating condition; When the total valve position instruction 50% < φ < 100%, the related parameters under different total valve position instructions are substituted into formula (2) at a certain interval to calculate the flow factor under the condition; - formula (2) In the formula: is the flow factor under different total valve position command working conditions; , is the equivalent steam distribution stage group pre-stage and post-stage pressure under different total valve position command working conditions; is the equivalent steam distribution stage group pre-stage specific volume under different total valve position command working conditions; Flow factor under the reference working condition Flow factor under different total valve position instructions φ Divide by the same, get equivalent steam distribution stage group flow correction coefficient under different total valve position instructions φ That is, get the "total valve position instruction φ-equivalent steam distribution stage group flow correction coefficient μ" curve; Step 2: According to the test results of the turbine valve flow characteristics or the overall variable condition simulation calculation results of the turbine steam distribution end, the main steam parameters are taken as the parameters before the equivalent steam distribution stage group, and the parameters of the first extraction steam are taken as the parameters after the equivalent steam distribution stage group. The efficiency of the equivalent steam distribution stage group under different total valve position commands φ is calculated , that is, the "total valve position command φ-equivalent steam distribution stage group efficiency " curve is obtained; Step 3: In the application, the main steam valve and the first-stage extraction port are also regarded as an equivalent steam distribution stage group, the main steam parameter is taken as the stage front parameter of the equivalent steam distribution stage group, and the first-stage extraction parameter is taken as the stage rear parameter of the equivalent steam distribution stage group; for the equivalent steam distribution stage group flow and the equivalent steam distribution stage group front pressure, one of them is known and the other is to be solved; at this time, by setting the total valve position instruction φ, the corresponding equivalent steam distribution stage group flow correction coefficient μ is calculated by interpolation according to the "total valve position instruction φ-equivalent steam distribution stage group flow correction coefficient μ" curve; then, formula (3) is used to realize the mutual solving between the equivalent steam distribution stage group flow and the equivalent steam distribution stage group front pressure; - formula (3) In the formula: is the equivalent steam distribution stage group flow under the reference working condition; is the equivalent steam distribution stage group flow under the total valve position instruction φ working condition; is the equivalent steam distribution stage group flow correction coefficient under the total valve position instruction φ working condition, , is the equivalent steam distribution stage group pre-stage and post-stage pressure under the total valve position instruction φ working condition; is the equivalent steam distribution stage group pre-stage specific volume under the total valve position instruction φ working condition; Step 4: In the application, the equivalent steam distribution stage group rear enthalpy is to be solved; at this time, by setting the total valve position instruction φ, the corresponding equivalent steam distribution stage group efficiency η is calculated by interpolation according to the "total valve position instruction φ-equivalent steam distribution stage group efficiency η" curve; then, the equivalent steam distribution stage group rear enthalpy is solved by using the efficiency calculation formula (4). - formula (4) In the formula: is the equivalent enthalpy after the stage in the equivalent stage group at the total valve position command φoperation; is the equivalent enthalpy before the stage in the equivalent stage group at the total valve position command φoperation; is the equivalent isentropic enthalpy in the equivalent stage group at the total valve position command φoperation; is the equivalent stage group efficiency in the equivalent stage group at the total valve position command φoperation.

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