Online determination method and device for specific enthalpy and dryness of working fluid of nuclear power saturated steam turbine

Abstract

The present invention provides a method and device for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine, including: S1, obtaining relevant parameters and operation data of the saturated steam turbine; S2, determining the dry-base internal efficiency and dehumidification efficiency of each stage group in the turbine; S3, determining the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group; S4, calculating the internal efficiency of the stage group under the current working condition, the effective enthalpy drop of the working fluid at the inlet and outlet, and the specific enthalpy and dryness of the working fluid at the outlet of the stage group; S5, determining the internal efficiency of the stage group under the current working condition; S6, repeating S4 to S5 until the difference between the specific enthalpies of the working fluid at the outlet of the stage group obtained from two adjacent calculations is less than a preset threshold, and then terminating the calculation to obtain the specific enthalpy of the working fluid before dehumidification; S7, obtaining the Bowman factor of the turbine by optimization according to the effective enthalpy drop of the stage group in S4; S8, solving the model of the inter-stage dehumidification device of the turbine to obtain the real-time values of the specific enthalpy and dryness of the working fluid of the turbine. The present invention solves the problem that the specific enthalpy and dryness of the working fluid of the turbine cannot be measured in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant modeling and operation optimization control. Specifically, it relates to a method and device for online determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine. Background Art

[0002] A saturated steam turbine, also known as a wet steam turbine, refers to a steam turbine in which the main steam is in a saturated or nearly saturated state. Since the natural circulation type steam generator used in a pressurized water reactor nuclear power unit can only generate saturated steam and there is no superheater in the nuclear power unit, for a nuclear power saturated steam turbine, except for the first few stages of the low-pressure cylinder working in the superheat region, all stages of the high-pressure cylinder and the remaining stages of the low-pressure cylinder work in the saturated region. Under off-design conditions, the specific enthalpy and dryness of the working fluid will change greatly. For example, as the unit power decreases, the main steam regulating valve gradually closes, the pressure behind the valve (i.e., the pressure of the first-stage stationary blade of the steam turbine) decreases, the pressure ratio of the working fluid at the inlet and outlet of the stage group decreases, resulting in a decrease in the effective enthalpy drop of the stage group, and the specific enthalpy and dryness of the working fluid at the outlet of the stage group increase accordingly.

[0003] Obtaining the dryness information of the working fluid is of great significance for the safety and economy of nuclear power plant operation. First, the dryness of the working fluid is an important process variable for the thermal calculation and simulation of the unit, and the calculation of the extraction mass flow rate and the unit efficiency depends on the dryness information of the working fluid; second, too low dryness of the working fluid will cause erosion of the steam turbine blades, reducing the safety of the nuclear power unit; third, too low dryness of the working fluid will exacerbate the wet steam loss of the steam turbine, reducing the internal efficiency of the steam turbine and affecting the economy of the unit.

[0004] In order to improve the internal efficiency of the steam turbine and reduce the wet steam loss of the saturated steam stage, the nuclear power unit uses a moisture separator reheater as an external dehumidification device to remove the liquid droplets in the exhaust steam of the high-pressure cylinder and heat the working fluid to the superheat state at the same time. In addition, various internal dehumidification devices are also used in nuclear power saturated steam turbines, such as drain rings, dehumidification stages, hollow stationary blades, etc. However, there is no real-time flow measurement point for the inter-stage drain, which brings difficulties to the thermal calculation of the steam turbine.

[0005] The existing measurement methods for the dryness of the working fluid are limited. The isotope tracer method is expensive and cannot be used for a long time due to the influence of the half-life; the optical method is restricted by the liquid droplet diameter and has low measurement accuracy; the thermodynamic method cannot be continuously measured online. For thermal power units, a soft measurement method can be used: since in a thermal power steam turbine, except for the last stage of the low-pressure cylinder being in a saturated state, the extraction steam at each stage is in a superheated state, the extraction specific enthalpy can be directly calculated according to the temperature and pressure of the working fluid at the extraction port, and then an equation for the output power of the unit and the total enthalpy drop of the working fluid is established to determine the specific enthalpy and dryness of the exhaust steam of the low-pressure cylinder. However, for nuclear power units, most of the extraction steam is in a saturated state, and the specific enthalpy of the extraction steam cannot be uniquely determined by temperature and pressure, so this method is not applicable.

[0006] After a search of the prior art, it is found that the Chinese invention patent "An Online Monitoring System and Method for the Exhaust Enthalpy Value of a Steam Turbine Low-Pressure Cylinder" with the application number CN201811214827.7 and the application date of October 18, 2018 proposes an online monitoring system and method for the specific enthalpy of the exhaust steam of a steam turbine low-pressure cylinder, establishes the enthalpy balance equations of the shaft seal steam heater, the low-pressure feedwater heater, and the condenser, and can be used to calculate the specific enthalpy of the exhaust steam of the low-pressure cylinder. However, this method is only applicable to steam turbines in which only the exhaust steam of the last stage of the low-pressure cylinder is saturated steam, and is not applicable to nuclear power saturated steam turbines in which the extraction steam at each stage is in a saturated state. Similarly, Chinese invention patents CN202110710390.1, CN201410329223.2, CN201711124397.5, CN201010128903.X, CN201810343813.9, CN200810200503., etc. can all be used for the calculation or identification of the specific enthalpy of the exhaust steam of the low-pressure cylinder of a thermal power unit, but cannot be used to determine the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine. In addition, the Chinese invention patent "Soft Measurement Method for the Exhaust Enthalpy of a Steam Turbine in a Saturated Steam Power Generation Unit" with the application number CN202110311488.X and the application date of March 24, 2021 proposes a soft measurement method for the exhaust enthalpy of a steam turbine in a saturated steam power generation unit based on enthalpy balance, which can be used to determine the specific enthalpy of the exhaust steam of saturated steam. This method establishes the enthalpy balance equation at the inlet and outlet of the steam turbine, and determines the specific enthalpy of the working fluid at the outlet of the steam turbine by using the specific enthalpy of the working fluid at the inlet of the steam turbine and the output power of the steam turbine. However, this method does not consider the multi-stage extraction steam of a large steam turbine and is only applicable to steam turbines without extraction steam, and cannot be used to determine the specific enthalpy and dryness of the working fluid of a nuclear power plant saturated steam turbine.

[0007] In summary, the existing public literatures and patents do not involve the online determination problem of the specific enthalpy and dryness of the working fluid of a saturated steam turbine under variable operating conditions, and this gap needs to be filled. Summary of the Invention

[0008] In view of the deficiencies of the prior art, the present invention provides a method and device for online determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine.

[0009] In the first aspect of the present invention, a method for online determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine is provided, specifically including:

[0010] S1: Obtain the structural parameters of the steam turbine equipment, the design values of the process variables of each stage of the steam turbine, and the operating data of the steam turbine device at a given moment; the steam turbine operating data includes: the inlet and outlet working fluid pressures of each stage group of the steam turbine, the mass flow rate and dryness of the working fluid at the inlet of the stage group.

[0011] S2: Determine the dry-base internal efficiency of each stage group in the steam turbine and the dehumidification efficiency of the internal dehumidification device of the steam turbine according to the structural parameters obtained in S1 and the design values of each process variable.

[0012] S3: Calculate the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group based on the pressures of the working fluid at the inlet and outlet of the stage group in the steam turbine operation data in S1.

[0013] S4: Calculate the effective enthalpy drop of the working fluid at the inlet and outlet of the stage group based on the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group obtained in S3, and further determine the specific enthalpy and dryness of the working fluid at the outlet of the stage group.

[0014] S5: Determine the internal efficiency of the stage group under the current working condition according to the dryness of the working fluid at the inlet of the stage group in the steam turbine operation data in S1 and the dryness of the working fluid at the outlet of the stage group obtained in S4.

[0015] S6: Substitute the internal efficiency of the stage group in S5 back into S4, and repeat S4 - S5 several times. When the difference between the calculation results of the effective enthalpy drop of the stage group in two adjacent times is less than the threshold, terminate the calculation.

[0016] S7: Calculate the output power of the steam turbine according to the specific enthalpy of the working fluid at the outlet of the stage group determined in S4 that meets the conditions of S6. Optimize the obtained output power of the steam turbine to obtain the Bowman factor of the steam turbine. The obtained Bowman factor will be used in S2 and S5 of the next operation.

[0017] S8: Solve the model of the inter-stage dehumidification device of the steam turbine according to the specific enthalpy of the working fluid at the outlet of the stage group determined in S4 that meets the conditions of S6, and obtain the real-time values of the specific enthalpy and dryness of the working fluid of the steam turbine.

[0018] In the second aspect of the present invention, a readable medium is provided, on which instructions are stored. When the instructions are executed on an electronic device, the electronic device is enabled to execute the online determination method for the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine.

[0019] In the third aspect of the present invention, an electronic device is provided, including a memory, a processor, and a computer program stored on the memory and capable of running on the processor. When the processor executes the program, it is used to execute the online determination method for the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine.

[0020] Compared with the prior art, the embodiments of the present invention have at least one of the following beneficial effects:

[0021] The present invention provides an online determination method for the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine, which can be used for the step-by-step determination of the specific enthalpy of the working fluid of each stage of the nuclear power saturated steam turbine, and can solve the problem of online determination of the specific enthalpy and dryness of the working fluid of the saturated steam turbine under variable working conditions.

[0022] The present invention provides a method for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam steam turbine, which corrects the calculation result of the dryness of the working fluid under variable operating conditions, performs iterative calculations on the internal efficiency of the steam turbine unit and the dryness at the outlet of the stage group, and obtains the specific enthalpy and dryness of the working fluid applicable to variable operating conditions, solving the problem that the dryness of each stage of extraction steam cannot be continuously measured on-line, and having application potential in the real-time evaluation of the operating economy index of a nuclear power saturated steam steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments read in conjunction with the accompanying drawings.

[0024] Figure 1 is a schematic structural diagram of a nuclear power saturated steam steam turbine in an embodiment of the present invention;

[0025] Figure 2 is a flowchart of a method for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam steam turbine in an embodiment of the present invention;

[0026] Figure 3 is a diagram of the output power change of a nuclear power unit in an embodiment of the present invention;

[0027] Figure 4 is the calculation result of the specific enthalpy of the working fluid of each stage of the steam turbine in an embodiment of the present invention;

[0028] Figure 5 is the calculation result of the dryness of the working fluid of each stage of the steam turbine in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0030] Figure 1 is a schematic structural diagram of a nuclear power saturated steam steam turbine in an embodiment of the present invention. The steam turbine includes a high-pressure cylinder and a low-pressure cylinder. The high-pressure cylinder has extraction steam at the 7th, 6th, and 5th stages, and the low-pressure cylinder includes extraction steam at the 4th, 3rd, 2nd, and 1st stages. The specific enthalpy and dryness of the above-mentioned extraction steam at each stage cannot be measured on-line.

[0031] Figure 2 is a flowchart of a method for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam steam turbine in an embodiment of the present invention. Referring to Figure 2 as shown, in the embodiment of the present invention, the method for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam steam turbine can be carried out according to the following steps:

[0032] S1: Obtain the structural parameters of the steam turbine equipment, the design values of each process variable of the steam turbine, and the operating data of the steam turbine device at a given moment.

[0033] The structural parameters of the steam turbine equipment specifically include the number of stages and the extraction port positions of the steam turbine, which can be obtained by referring to the steam turbine regulations.

[0034] The design values of each process variable of the steam turbine specifically include the design values of the temperature, pressure, specific enthalpy, dryness, and mass flow rate of the working fluid at the inlet and outlet of each stage group of the steam turbine. The above design values can be obtained according to the steam turbine regulations.

[0035] The operating data of the steam turbine device at a given moment can be obtained through the on-site DCS, specifically including: the pressures of the working fluid at the inlet and outlet of each stage group of the steam turbine, the mass flow rate and dryness of the working fluid at the inlet of the stage group.

[0036] S2: Calculate the dry-base internal efficiency of each stage group in the steam turbine and the dehumidification efficiency of the internal dehumidification device of the steam turbine according to the structural parameters and the design values of each process variable obtained in S1.

[0037] S3: Calculate the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group based on the pressures of the working fluid at the inlet and outlet of the stage group in the steam turbine operating data in the above step S1.

[0038] S4: Calculate the effective enthalpy drop of the working fluid at the inlet and outlet of the stage group based on the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group obtained in the above step S3, and then calculate the specific enthalpy and dryness of the working fluid at the outlet of the stage group.

[0039] S5: Determine the internal efficiency of the stage group under the current working condition according to the dryness of the working fluid at the inlet of the stage group in the steam turbine operating data in S1 and the dryness of the working fluid at the outlet of the stage group obtained in S4.

[0040] S6: Substitute the internal efficiency of the stage group in S5 back into the formula in S4, and repeat S4 - S5 several times. When the difference between the calculation results of the effective enthalpy drop of the stage group in two adjacent times is less than the threshold, terminate the calculation.

[0041] S7: Calculate the output power of the steam turbine according to the specific enthalpy of the working fluid at the outlet of the stage group in S4 that meets the conditions in S6, and obtain the Bowman factor of the steam turbine by optimizing the output power of the steam turbine.

[0042] In this step, the obtained Bowman factor will be used in steps S2 and S5 of the next operation; the determination of the Bowman factor requires the results of other steps. Since this parameter is slowly varying, the results of this time are used for the next calculation.

[0043] S8: Solve the model of the inter-stage dehumidification device of the steam turbine according to the specific enthalpy of the working fluid at the outlet of the stage group in S4 to obtain the real-time values of the specific enthalpy and dryness of the working fluid of the saturated steam turbine.

[0044] This embodiment is a method for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine applicable to all working conditions, which solves the problem of on-line determination of the specific enthalpy and dryness of the working fluid of a saturated steam turbine under variable working conditions.

[0045] As a preferred embodiment, in S2, the dry-base internal efficiency of the stage group is calculated by the following formula:

[0046]

[0047] In the formula, η dry is the dry-base internal efficiency of the stage group, dimensionless; η ref is the internal efficiency of the stage group under the design condition, dimensionless; α is the Bowman factor of the stage group, dimensionless; x in ref and x out ref are the drynesses of the inlet and outlet working fluids of the stage group under the design condition, respectively, dimensionless.

[0048] Among them, the internal efficiency η ref of the stage group under the design condition is calculated by the following formula:

[0049]

[0050]

[0051] In the formula, h in ref and h out ref are the specific enthalpies of the inlet and outlet working fluids of the stage group under the design condition, kJ / kg; h out,s ref is the specific enthalpy of the outlet working fluid during isentropic expansion of the stage group under the design condition, kJ / kg; s in ref is the specific entropy of the inlet working fluid of the stage group under the design condition, kJ / kg / K; p out ref is the pressure of the outlet working fluid of the stage group under the design condition, MPa; s L (p out ref ) and s L (p out ref ) are the specific entropies of saturated water and saturated dry steam corresponding to the pressure p out ref , kJ / kg / K; h L (p out ref ) and h L (p out ref ) are the specific enthalpies of the pressure pout ref Specific enthalpy of corresponding saturated water and saturated dry steam, kJ / kg.

[0052] In this preferred embodiment, the dry-base internal efficiency of the calculation stage group is obtained through the above method, which has the advantages of convenient implementation and accurate calculation results compared with the existing methods. At the same time, it provides better preconditions for finally determining the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine online.

[0053] As a preferred embodiment, the dehumidification efficiency of the internal dehumidification device of the steam turbine is calculated by the following formula:

[0054]

[0055] In the formula, η sp is the dehumidification efficiency of the internal dehumidification device of the steam turbine, dimensionless; D dw ref is the mass flow rate of the inter-stage drain of the steam turbine under the design condition, kg / s; D in ref is the mass flow rate of the working fluid at the inlet of the stage group under the design condition, kg / s;

[0056] As a preferred embodiment, in S3, calculating the isentropic enthalpy drop of the stage group includes the following steps:

[0057] (a) Calculate the dryness x in and specific entropy s in of the working fluid at the inlet of the stage group:

[0058]

[0059] s in = x in s V (p in )+(1 - x in )s L (p in )

[0060] In the formula, x in is the dryness of the working fluid at the inlet of the stage group, dimensionless; h in is the specific enthalpy of the working fluid at the inlet of the stage group, kJ / kg; p in is the pressure of the working fluid at the inlet of the stage group, MPa; s in is the specific entropy of the working fluid at the inlet of the stage group, kJ / kg / K; h L (p in ) and h V (p in ) are the specific enthalpies of the saturated water and saturated dry steam corresponding to the pressure of the working fluid at the inlet of the stage group, kJ / kg; s L (p in ) and sV (p in ) are the specific entropies of saturated water and saturated dry steam corresponding to the inlet working fluid pressure of the stage group, kJ / kg / K.

[0061] (b) According to the specific entropy s in of the inlet working fluid of the stage group calculated in (a), calculate the dryness x out,s and specific enthalpy h out,s of the outlet working fluid of the stage group during isentropic expansion:

[0062]

[0063] h out,s = x out,s h V (p out ) + (1 - x out,s )h L (p out )

[0064] In the formula, x out,s is the dryness of the outlet working fluid of the stage group during isentropic expansion, dimensionless; h out,s is the specific enthalpy of the outlet working fluid of the stage group during isentropic expansion, kJ / kg; p out is the outlet working fluid pressure of the stage group, MPa; s L (p out ) and s V (p out ) are the specific entropies of saturated water and saturated dry steam corresponding to the outlet working fluid pressure of the stage group, kJ / kg / K; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the outlet working fluid pressure of the stage group, kJ / kg.

[0065] (c) According to the specific enthalpy h in of the inlet working fluid of the stage group and the specific enthalpy h out,s of the outlet working fluid of the stage group during isentropic expansion calculated in (b), calculate the isentropic enthalpy drop Δh s of the inlet and outlet working fluids of the stage group:

[0066] Δh s = h in - h out,s

[0067] In the formula, Δh s is the isentropic enthalpy drop of the inlet and outlet working fluids of the stage group, kJ / kg.

[0068] In this preferred embodiment, during the expansion process of saturated steam in the stage group, the influence of steam humidity on the efficiency within the stage group is considered, and the accuracy of the calculation results is higher.

[0069] As a preferred embodiment, in S4, the effective enthalpy drop of the stage group is calculated using the following formula:

[0070] Δh = ηΔh s

[0071] In the formula, η is the efficiency within the stage group under off-design conditions, dimensionless; Δh and Δh s are the effective enthalpy drop and isentropic enthalpy drop of the stage group respectively, in kJ / kg.

[0072] As a preferred embodiment, the specific enthalpy h out and dryness x out of the working fluid at the outlet of the stage group are calculated using the following formula:

[0073] h out = h in -Δh

[0074]

[0075] In the formula, h out is the specific enthalpy of the working fluid at the outlet of the stage group, in kJ / kg; x out is the dryness of the working fluid at the outlet of the stage group, dimensionless; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the outlet of the stage group respectively, in kJ / kg.

[0076] In this preferred embodiment, the specific enthalpy and humidity of the working fluid are calculated based on the internal efficiency and isentropic enthalpy drop of the stage group, solving the problem that the specific enthalpy and humidity of the steam in a saturated steam turbine cannot be measured.

[0077] As a preferred embodiment, in S5, based on the known dryness x in of the working fluid at the inlet of the stage group and the dryness x out of the working fluid at the outlet of the stage group obtained in S4, the internal efficiency of the stage group under the current operating conditions is calculated:

[0078]

[0079] In the formula, η is the internal efficiency of the stage group under off-design conditions, dimensionless; η dry is the dry-base internal efficiency of the stage group, dimensionless; x in and x out are the drynesses of the working fluid at the inlet and outlet of the stage group respectively, dimensionless.

[0080] In this preferred embodiment, the influence of the steam quality in the stage group on the internal efficiency is considered, and the calculation result is more accurate than that of the existing method.

[0081] As a preferred embodiment, in S6, the condition for terminating the calculation is:

[0082] ||Δh(i) - Δh(i - 1)||2 < ε es

[0083] In the formula, Δh(i) represents the effective enthalpy drop of the stage group obtained from the i-th iterative calculation, kJ / kg; ε es is a preset threshold according to the accuracy requirement, which is set to 0.1 kJ / kg in this embodiment. Of course, in other embodiments, it can also be selected according to the actual situation, and is not limited to this threshold value.

[0084] As a preferred embodiment, in S7, the output power of the steam turbine is calculated using the following formula:

[0085] P tur = ∑D in (h in - h out )

[0086] In the formula, P tur is the output power of the steam turbine, KW; D in is the mass flow rate of the working fluid at the inlet of the stage group, kg / s; h in and h out are the specific enthalpies of the working fluid at the inlet and outlet of the stage group, kJ / kg respectively.

[0087] As a preferred embodiment, the following formula is used to optimize the Bowman factor of the steam turbine:

[0088]

[0089] In the formula, α is the Bowman factor, dimensionless; α(t - 1) represents the Bowman factor at the previous moment; and are the weighting coefficients, dimensionless; P gen is the electric power generated by the generator; η e is the generator efficiency, dimensionless.

[0090] In this preferred embodiment, the Bowman factor of the saturated steam turbine is determined by the above formula, solving the problem that the Bowman factor cannot be determined. At the same time, it provides conditions for on-line continuous measurement of the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine.

[0091] As a preferred embodiment, in S8, the specific enthalpy h es and dryness x es of the working fluid after steam-water separation are calculated using the following formulas respectively:

[0092]

[0093]

[0094] Wherein, h es is the specific enthalpy of the working fluid after steam-water separation, kJ / kg; x es is the dryness of the working fluid after steam-water separation, dimensionless; D in is the mass flow rate of the working fluid at the inlet of the stage group, kg / s; h out is the specific enthalpy of the working fluid at the outlet of the stage group, kJ / kg; η sp is the dehumidification efficiency of the internal dehumidification device of the steam turbine, dimensionless; x out is the dryness of the working fluid at the outlet of the stage group, dimensionless; p out is the pressure of the working fluid at the outlet of the stage group, MPa; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the outlet of the stage group, kJ / kg respectively.

[0095] In this preferred embodiment, through the steam-water separation process in the stage group by the above formula, the problem of difficult quantitative calculation in the steam-water separation process in the steam turbine is solved. At the same time, the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine are obtained, and the problem of inability to measure the specific enthalpy and dryness of the working fluid of the steam turbine in real time is solved.

[0096] In the above embodiment of the method for on-line determination of the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine of the present invention, the DCS measured data of the nuclear power unit are first obtained. Among them, the output power of the unit is shown in Figure 3 .

[0097] Figure 4 is the calculation result of the specific enthalpy of the extraction steam of each stage of the steam turbine in an embodiment of the present invention; among them, the specific enthalpy of each stage of extraction steam cannot be determined according to the existing temperature and pressure measurement points. The method for on-line determination of the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine provided by the embodiment of the present invention solves this problem.

[0098] Figure 5 is the calculation result of the dryness of the extraction steam of each stage of the steam turbine in an embodiment of the present invention. The present invention solves the problem of inability to continuously measure the dryness of the extraction steam of each stage on line.

[0099] In another embodiment of the present invention, a readable medium is further provided, and instructions are stored on the readable medium. When the instructions are executed on an electronic device, the electronic device executes the method for on-line determination of the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine in any one of the above embodiments.

[0100] In another embodiment of the present invention, an electronic device is further provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it is used to execute the on-line determination method of the specific enthalpy and dryness of the working medium of the nuclear power saturated steam steam turbine in any one of the above embodiments.

[0101] Next Figure 1 Taking the first stage group in the front flow path of the high-pressure cylinder of the steam turbine below as an example, the specific enthalpy and dryness of the working medium at the outlet of this stage group (i.e., the 7th stage extraction steam) are determined online at a certain moment:

[0102] S1. Obtain the design values of each process variable of the steam turbine according to the steam turbine regulations, including: the design values of the working medium temperatures at the inlet and outlet of the stage group are 547.8K and 504.9K respectively; the design values of the working medium pressures at the inlet and outlet of the stage group are 5.918MPa and 2.883MPa respectively; the design values of the specific enthalpies of the working medium at the inlet and outlet of the stage group are 2772.4kJ / kg and 2652.3kJ / kg respectively; the design values of the drynesses of the working medium at the inlet and outlet of the stage group are 99.53% and 91.64% respectively; the design values of the mass flows of the working medium at the inlet and outlet of the stage group are 767.7kg / s and 638.2kg / s respectively; the design value of the mass flow of the inter-stage drain is 0.4080kg / s;

[0103] Obtain the operation data of the steam turbine device at a given moment through the on-site DCS, including: the working medium pressures at the inlet and outlet of the stage group are 6.005MPa and 2.838MPa respectively; the mass flow of the working medium at the inlet of the stage group is 777.4kg / s; the dryness of the working medium at the inlet of the stage group is 99.48%;

[0104] S2. The dry-base internal efficiency of the stage group is calculated using the following formula:

[0105]

[0106] In the formula, α is the Baumann factor of the stage group, which is 1.324; x in ref and x out ref are the drynesses of the working medium at the inlet and outlet of the stage group under the design conditions, which are 99.53% and 91.59% respectively.

[0107] The dry-base internal efficiency η dry of this stage group is 94.84%

[0108] Among them, the internal efficiency η ref of the stage group under the design conditions has a value of 89.26% and is calculated using the following formula:

[0109]

[0110]

[0111] In the formula, h in ref and h out ref are the specific enthalpies of the working fluid at the inlet and outlet of the stage group under the design condition, which are 2772 kJ / kg and 2651 kJ / kg respectively; h out,s ref is the specific enthalpy of the working fluid at the outlet during isentropic expansion of the stage group under the design condition, and the calculated result is 2637 kJ / kg; s in ref is the specific entropy of the working fluid at the inlet of the stage group under the design condition, which is 5.883 kJ / kg / K; p out ref is the pressure of the working fluid at the outlet of the stage group under the design condition, which is 2.883 MPa; s L (p out ref ) and s L (p out ref ) are the specific entropies of saturated water and saturated dry steam corresponding to the pressure p out ref , which are 3.019 kJ / kg / K and 5.897 kJ / kg / K respectively; h L (p out ref ) and h L (p out ref ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure p out ref , which are 1209 kJ / kg and 2785 kJ / kg respectively.

[0112] The dehumidification efficiency of the internal dehumidification device of the steam turbine is calculated by the following formula:

[0113]

[0114] In the formula, D dw ref is the mass flow rate of the inter-stage drain of the steam turbine under the design condition, 0.4080 kg / s; D in ref is the mass flow rate of the working fluid at the inlet of the stage group under the design condition, 767.7 kg / s;

[0115] The dehumidification efficiency η sp of the internal dehumidification device is 0.63%;

[0116] S3. To calculate the isentropic enthalpy drop of the stage group, the following steps are included:

[0117] (a) Calculate the dryness fraction \(x\) of the working fluid at the inlet of the stage group in and the specific entropy \(s\) in :

[0118]

[0119] \(s\) in = \(x\) in \(s\) V (\(p\) in )+(1 - \(x\) in )\(s\) L (\(p\) in )

[0120] In the formula, \(h\) in is the specific enthalpy of the working fluid at the inlet of the stage group, 2776 kJ / kg; \(p\) in is the pressure of the working fluid at the inlet of the stage group, 6.005 MPa; \(h\) L (\(p\) in ) and \(h\) V (\(p\) in ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the inlet of the stage group, 1214 kJ / kg and 2784 kJ / kg respectively; \(s\) L (\(p\) in ) and \(s\) V (\(p\) in ) are the specific entropies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the inlet of the stage group, 3.028 kJ / kg / K and 5.890 kJ / kg / K respectively.

[0121] The dryness fraction \(x\) of the working fluid at the inlet of the stage group is obtained as 99.48%; the specific entropy \(s\) of the inlet working fluid in is 5.8748 kJ / kg / K; in

[0122] (b) According to the specific entropy \(s\) of the working fluid at the inlet of the stage group calculated in (a) in , calculate the dryness fraction \(x\) and specific enthalpy \(h\) of the working fluid at the outlet of the stage group during isentropic expansion out,s : out,s

[0123]

[0124] \(h\) out,s = \(x\) out,s \(h\) V (\(p\) out )+(1 - \(x\) out,s )\(h\) L (\(p\) out )

[0125] In the formula, \(p\) out is the pressure of the working fluid at the outlet of the stage group, 2.838 MPa; \(s\) L(p out ) and s V (p out ) are the specific entropies of saturated water and saturated dry steam corresponding to the working fluid pressure at the outlet of the stage group, which are 2.617 kJ / kg / K and 6.208 kJ / kg / K respectively; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the working fluid pressure at the outlet of the stage group, 993.9 kJ / kg and 2803 kJ / kg respectively.

[0126] The dryness x of the working fluid at the outlet of the stage group during isentropic expansion is obtained as out,s 90.73%; the specific enthalpy h out,s is 2635 kJ / kg;

[0127] (c) According to the specific enthalpy h in of the working fluid at the inlet of the stage group and the specific enthalpy h out,s of the working fluid at the outlet of the stage group during isentropic expansion calculated in (b), calculate the isentropic enthalpy drop Δh s of the working fluid at the inlet and outlet of the stage group:

[0128] Δh s = h in - h out,s

[0129] In the formula, h in is the specific enthalpy of the working fluid at the inlet of the stage group, which is 2776 kJ / kg;

[0130] The isentropic enthalpy drop Δh s of the working fluid at the inlet and outlet of the stage group is obtained as 140.9 kJ / kg;

[0131] S4. The effective enthalpy drop of the stage group is calculated using the following formula:

[0132] Δh = ηΔh s

[0133] In the formula, η is the efficiency within the stage group under off-design conditions. During the first calculation, the dry-base internal efficiency η dry in S2 can be used for substitution, that is, 94.84%. During the subsequent iteration process in S6, the calculation result in S5 is used;

[0134] The effective enthalpy drop Δh of the stage group is obtained as 133.6 kJ / kg;

[0135] The specific enthalpy h out and dryness x out of the working fluid at the outlet of the stage group are calculated using the following formula:

[0136] h out = hin -Δh

[0137]

[0138] Obtain the specific enthalpy h of the working fluid at the outlet of the stage group out is 2643 kJ / kg; the dryness x of the working fluid at the outlet of the stage group out is 91.14%;

[0139] S5. According to the known dryness x of the working fluid at the inlet of the stage group in and the dryness x of the working fluid at the outlet of the stage group obtained from S4 out , calculate the internal efficiency of the stage group under the current working condition:

[0140]

[0141] Obtain the internal efficiency η of the stage group under off-design conditions as 88.95%;

[0142] S6. The condition for terminating the calculation is:

[0143] ||Δh(i) - Δh(i - 1)||2 < ε es

[0144] where Δh(i) represents the effective enthalpy drop of the stage group obtained from the i-th iterative calculation, kJ / kg; ε es is a threshold preset according to the accuracy requirement, which is set to 0.1 kJ / kg in this embodiment. Of course, in other embodiments, it can also be selected according to the actual situation, and is not limited to this threshold value.

[0145] After multiple iterations, obtain the effective enthalpy drop Δh of the stage group that satisfies the termination condition as 125.5 kJ / kg; the specific enthalpy h of the working fluid at the outlet of the stage group out is 2650 kJ / kg, and the corresponding dryness x of the working fluid at the outlet of the stage group out is 91.57;

[0146] S7. The output power of the steam turbine is calculated using the following formula:

[0147] P tur = ∑D in (h in - h out )

[0148] Obtain the output power P of the steam turbine tur is 1.156×10 6 KW;

[0149] Optimize the Baumann factor of the steam turbine using the following formula:

[0150]

[0151] In the formula, α(t - 1) represents the Bowman factor at the previous moment, that is, 1.324 used in S2 and S4 before; and are weighting coefficients, taking 10 and 1 respectively; P gen is the electric power generated by the generator, which is 1.060×10 6 KW; η e is the generator efficiency, with a value of 91.66%.

[0152] The new Bowman factor α is obtained as 1.321.

[0153] S8, the specific enthalpy h es and dryness x es of the working fluid after steam - water separation are calculated respectively using the following formulas:

[0154]

[0155]

[0156] In the formula, D in is the mass flow rate of the working fluid at the inlet of the stage group, which is 777.4 kg / s;

[0157] The specific enthalpy h es of the working fluid after steam - water separation is obtained as 2651 kJ / kg; the dryness x es of the working fluid after steam - water separation is 91.63%; the real - time values of the specific enthalpy and dryness of the steam turbine working fluid are h es and x es .

[0158] The method of the above - mentioned embodiments of the present invention can be used to determine the specific enthalpy and dryness of the working fluid of a saturated steam turbine in a nuclear power plant, and can determine the specific enthalpy and dryness of the saturated steam turbine working fluid in real - time. The results obtained in the embodiments of the present invention can be directly used for the real - time online monitoring of the nuclear power saturated steam turbine. Specifically, after obtaining the real - time values of the specific enthalpy and dryness of the above - mentioned steam turbine working fluid, they can be compared with the set monitoring threshold values. If the threshold values are exceeded, an alarm will be issued, which plays an important auxiliary role in the operation monitoring of the nuclear power saturated steam turbine.

[0159] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above - mentioned specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An online determination method for the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine, characterized in that, Including: S1: Obtain the structural parameters of the steam turbine equipment, the design values of various process variables of the steam turbine, and the operating data of the steam turbine device at a given moment; The operating data of the steam turbine includes: the inlet and outlet working fluid pressures of each stage group of the steam turbine, the mass flow rate and dryness of the working fluid at the inlet of the stage group; S2: Determine the dry-base internal efficiency of each stage group inside the steam turbine and the dehumidification efficiency of the internal dehumidification device of the steam turbine according to the structural parameters and the design values of various process variables obtained in S1; S3: Calculate the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group based on the pressures of the working fluid at the inlet and outlet of the stage group in the operating data of the steam turbine in S1; S4: Calculate the effective enthalpy drop of the working fluid at the inlet and outlet of the stage group based on the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group obtained in S3, and further determine the specific enthalpy and dryness of the working fluid at the outlet of the stage group; S5: Determine the internal efficiency of the stage group under the current working condition according to the dryness of the working fluid at the inlet of the stage group in the operating data of the steam turbine in S1 and the dryness of the working fluid at the outlet of the stage group obtained in S4; S6: Substitute the internal efficiency of the stage group in S5 back into S4, repeat S4 - S5 several times, and terminate the calculation when the difference between the calculation results of the effective enthalpy drop of the stage group in two adjacent times is less than the threshold; S7: Calculate the output power of the steam turbine according to the specific enthalpy of the working fluid at the outlet of the stage group determined in S4 that meets the condition of S6, and optimize the Bowman factor of the steam turbine by using the obtained output power of the steam turbine. The obtained Bowman factor will be used in S2 and S5 of the next operation; S8: Solve the model of the inter-stage dehumidification device of the steam turbine according to the specific enthalpy of the working fluid at the outlet of the stage group determined in S4 that meets the condition of S6, and obtain the real-time values of the specific enthalpy and dryness of the working fluid of the steam turbine; In S2, the dry-base internal efficiency of each stage group inside the steam turbine is calculated by using the following formula: In the formula, η dry is the dry-base internal efficiency of the stage group, dimensionless; η ref is the internal efficiency of the stage group under the design condition, dimensionless; α is the Bowman factor of the stage group, dimensionless; x in ref and x out ref are the drynesses of the working medium at the inlet and outlet of the stage group under the design condition, respectively, dimensionless; The internal efficiency η of the stage group under the design condition ref is calculated using the following formula: where h in ref and h out ref are the specific enthalpies of the working fluid at the inlet and outlet of the stage group under the design conditions, kJ / kg; h out,s ref is the specific enthalpy of the working fluid at the outlet during isentropic expansion of the stage group under the design conditions, kJ / kg; s in ref is the specific entropy of the working fluid at the inlet of the stage group under the design conditions, kJ / kg / K; p out ref is the pressure of the working fluid at the outlet of the stage group under the design conditions, MPa; s L (p out ref ) and s L (p out ref ) are the specific entropies of saturated water and saturated dry steam corresponding to the pressure p out ref , kJ / kg / K; h L (p out ref ) and h L (p out ref ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure p out ref , kJ / kg; The dehumidification efficiency of the internal dehumidification device of the steam turbine is calculated by using the following formula: In the formula, η sp is the dehumidification efficiency of the internal dehumidification device of the steam turbine, dimensionless; D dw ref is the mass flow rate of the inter-stage drain of the steam turbine under the design condition, kg / s; D in ref is the mass flow rate of the working medium at the inlet of the stage group under the design condition, kg / s; x out ref is the dryness of the working medium at the outlet of the stage group under the design condition, dimensionless; In S3, the calculation of the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group includes: (a) Calculate the dryness fraction x of the working fluid at the inlet of the stage group in and the specific entropy s in : s in = x in s V (p in ) + (1 - x in )s L (p in ) where x in is the dryness of the working fluid at the inlet of the stage group, dimensionless; h in is the specific enthalpy of the working fluid at the inlet of the stage group, kJ / kg; p in is the pressure of the working fluid at the inlet of the stage group, MPa; s in is the specific entropy of the working fluid at the inlet of the stage group, kJ / kg / K; h L (p in ) and h V (p in ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the inlet of the stage group, kJ / kg; s L (p in ) and s V (p in ) are the specific entropies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the inlet of the stage group, kJ / kg / K; (b) Calculate the dryness fraction x in and specific enthalpy h out,s of the working fluid at the outlet of the stage group during isentropic expansion according to the specific entropy s out,s of the working fluid at the inlet of the stage group obtained in (a): h out,s = x out,s h V (p out ) + (1 - x out,s )h L (p out ) where x out,s is the dryness of the working fluid at the outlet of the stage group during isentropic expansion, dimensionless; h out,s is the specific enthalpy of the working fluid at the outlet of the stage group during isentropic expansion, kJ / kg; p out is the pressure of the working fluid at the outlet of the stage group, MPa; s L (p out ) and s V (p out ) are the specific entropies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the outlet of the stage group, kJ / kg / K; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the outlet of the stage group, kJ / kg; (c) According to the specific enthalpy h of the working fluid at the inlet of the stage group in and the specific enthalpy h of the working fluid at the outlet of the stage group during isentropic expansion obtained in (b) out,s , calculate the isentropic enthalpy drop Δh of the working fluid at the inlet and outlet of the stage group s : Δh s = h in - h out,s where Δh s is the isentropic enthalpy drop of the working fluid at the inlet and outlet of the stage group, kJ / kg; In S4, the calculation of the effective enthalpy drop of the working fluid at the inlet and outlet of the stage group is carried out by using the following formula: Δh = ηΔh s In the formula, η is the efficiency within the stage group under off-design conditions, dimensionless; Δh and Δh s are respectively the effective enthalpy drop and the isentropic enthalpy drop of the stage group, kJ / kg; The calculation of the specific enthalpy and dryness of the working fluid at the outlet of the stage group is carried out by using the following formula: h out = h in - Δh where h out is the specific enthalpy of the working fluid at the outlet of the stage group, kJ / kg; x out is the dryness fraction of the working fluid at the outlet of the stage group, dimensionless; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the outlet of the stage group, respectively, kJ / kg; In S5, according to the known dryness x of the working fluid at the inlet of the stage group in and the dryness x of the working fluid at the outlet of the stage group obtained in S4 out , calculate the efficiency within the stage group under the current operating condition: In the formula, η is the efficiency within the stage group under off-design conditions, dimensionless; η dry is the dry-base internal efficiency of the stage group, dimensionless; x in and x out are the drynesses of the working fluid at the inlet and outlet of the stage group, respectively, dimensionless.

2. The method for on-line determination of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine according to claim 1, characterized in that, In S6, the condition for terminating the calculation is: ||Δh(i)-Δh(i - 1)||2 < ε es where Δh(i) represents the effective enthalpy drop of the stage group obtained from the i-th iterative calculation, kJ / kg; ε es is a preset threshold value, kg / s.

3. The online determination method of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine according to claim 1, characterized in that In S7, the output power of the steam turbine is calculated by using the following formula: P tur = ∑D in (h in - h out ) Wherein, P tur is the output power of the steam turbine, in kW; D in is the mass flow rate of the working fluid at the inlet of the stage group, in kg / s; h in and h out are the specific enthalpies of the working fluid at the inlet and outlet of the stage group respectively, in kJ / kg; The Bowman factor of the steam turbine is optimized by using the following formula: where α is the Bowman factor, dimensionless; α(t - 1) represents the Bowman factor at the previous moment; and are weighting coefficients, dimensionless; P gen is the electric power generated by the generator; η e is the generator efficiency, dimensionless.

4. The online determination method of the specific enthalpy and dryness of the working fluid of a nuclear power saturated steam turbine according to claim 1, characterized in that In S8, for the model of the steam turbine inter-stage dehumidification device, the specific enthalpy h of the working fluid after steam-water separation es and the dryness x es are respectively calculated by the following formulas: where h es is the specific enthalpy of the working fluid after steam-water separation, kJ / kg; x es is the dryness fraction of the working fluid after steam-water separation, dimensionless; D in is the mass flow rate of the working fluid at the inlet of the stage group, kg / s; h out is the specific enthalpy of the working fluid at the outlet of the stage group, kJ / kg; η sp is the dehumidification efficiency of the internal dehumidification device of the steam turbine, dimensionless; x out is the dryness fraction of the working fluid at the outlet of the stage group, dimensionless; p out is the pressure of the working fluid at the outlet of the stage group, MPa; h L (p out ) and h V (p out ) are the specific enthalpies of saturated water and saturated dry steam corresponding to the pressure of the working fluid at the outlet of the stage group, kJ / kg; The real-time values of the specific enthalpy and dryness of the working fluid of the steam turbine are h es and x es .

5. A readable medium, characterized in that, Instructions are stored on the readable medium, and when the instructions are executed on the electronic device, the electronic device executes the method for on-line determination of the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine according to any one of claims 1 to 4.

6. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and capable of running on the processor, characterized in that, When the processor executes the program, it is used to execute the method for on-line determination of the specific enthalpy and dryness of the working fluid of the nuclear power saturated steam turbine according to any one of claims 1 to 4.

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