A method and device for real-time determination of extraction flow rate of nuclear power saturated steam turbine

Abstract

The present invention provides a method and device for determining the extraction flow rate of a nuclear power saturated steam turbine in real time, including: S1, obtaining the equipment structural parameters of a feedwater heater and the operating data of the feedwater heater at a given time; S2, calculating the extraction specific enthalpy at the given time; S3, calculating the heat flow of the extraction condensation section and the drain cooling section; S4, solving the tube-side feedwater model; S5, solving the shell-side steam condensation section model; S6, solving the shell-side drain cooling section model; S7, repeating S3-S6 several times, terminating the calculation when the difference between two adjacent results is less than a threshold, and obtaining the real-time calculated value of the turbine extraction mass flow rate. The present invention can be used to calculate the extraction mass flow rate of a nuclear power saturated steam turbine in real time, and the calculation result has the advantages of small calculation error, strong anti-interference and high real-time performance compared with the existing method.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant operation optimization control, and in particular to a method and device for real-time determination of extraction flow of a nuclear power saturated steam turbine based on a feedwater heater mechanism model. Background Art

[0002] Modern steam turbine units mostly use heat recovery steam extraction to preheat feed water, thereby reducing the cold end loss of the steam turbine and improving the thermal cycle efficiency of the power plant. The heat recovery steam extraction system extracts high-energy steam from the steam turbine and sends it to the steam condensation section of the shell side of the feed water heater. The extraction steam condenses into drain after heat exchange with the tube side feed water in the steam condensation section. The drain flows into the drain cooling section and continues to exchange heat with the feed water. In summary, according to the spatial position and aggregation state of the working fluid, the feed water heater can be divided into three parts: tube side feed water, shell side steam condensation section and shell side drain cooling section.

[0003] The steam extraction mass flow rate of the steam turbine is one of the important process variables of the steam turbine. Based on the steam extraction mass flow rate, the steam mass flow rate flowing through each stage of the steam turbine can be calculated, which can be further used for the thermal balance calculation of the steam turbine system. However, there is no mass flow measurement point for steam extraction of the steam turbine. The existing technology mainly uses the method of establishing the enthalpy balance equation of the feedwater heater to calculate the steam extraction mass flow rate.

[0004] After searching the prior art, it was found that the Chinese invention patent "Method for measuring the heating extraction steam flow rate of the unit based on enthalpy calculation" with application number CN202010551035.X and application date June 17, 2020, is aimed at a 300MW subcritical cogeneration thermal power unit. It proposes a heating extraction steam flow calculation method based on enthalpy balance, which can be used for the calculation of heating extraction steam flow.

[0005] However, the enthalpy balance method only considers the inlet and outlet working fluids, ignoring the mass and energy accumulation inside the equipment. Therefore, the enthalpy balance method is easily affected by the noise in process variables such as feed water mass flow rate and feed water specific enthalpy, and the calculation results fluctuate greatly and have poor anti-interference ability. Secondly, the enthalpy balance method constructs the steady-state equation of the inlet and outlet working fluids of the feed water heater, ignoring the dynamic characteristics inside the feed water heater. In particular, the stages of nuclear power saturated steam turbines are mostly in a working environment of wet saturated steam, the humidity of wet steam cannot be measured online, and the specific enthalpy of the working fluid cannot be directly calculated through temperature and pressure. Therefore, the enthalpy balance method of the existing patent is not applicable to nuclear power saturated steam turbines.

[0006] In summary, the existing publicly reported literature and patents do not involve a real-time determination method for the extraction mass flow rate of a saturated steam turbine of a nuclear power unit, and this gap needs to be filled. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a method and device for real-time determination of extraction flow of a nuclear power saturated steam turbine based on a feedwater heater mechanism model.

[0008] In a first aspect of the present invention, a method for real-time determination of extraction flow rate of a nuclear power saturated steam turbine is provided. The method is based on a feedwater heater mechanism model, wherein the feedwater heater mechanism model includes a tube-side feedwater model, a shell-side steam condensation section model, and a shell-side drain cooling section model; the method includes:

[0009] S1: Acquire the equipment structural parameters of the feedwater heater and the operation data of the feedwater heater at a given time;

[0010] S2: Determine the extraction steam specific enthalpy at the given time according to the equipment structural parameters and operation data obtained in S1;

[0011] S3: Based on the extraction specific enthalpy obtained in S2 above, the real-time heat flow and heat transfer coefficient of the steam condensation section and the drain cooling section are calculated respectively;

[0012] S4: Based on the heat transfer coefficient obtained in S3 above, solve the tube feedwater model in the feedwater heater mechanism model to obtain the temperature, specific enthalpy and flow rate distribution of the feedwater;

[0013] S5: Based on the extraction steam specific enthalpy obtained in S2 and the real-time heat flow obtained in S3, the shell-side steam condensation section model in the feedwater heater mechanism model is solved to obtain the extraction steam mass flow rate and the condensate mass flow rate;

[0014] S6: Based on the temperature, specific enthalpy and flow rate distribution of the feed water obtained in S3 and the mass flow rate of the condensate obtained in S5, the shell-side drain cooling section model in the feed water heater mechanism model is solved to obtain the temperature, specific enthalpy and flow rate distribution of the drain;

[0015] S7: Substitute the results of S4-S6 back into S3, iterate S3-S6 several times, and terminate the calculation when the difference between the extraction steam mass flow rates obtained in S5 in two adjacent calculations is less than the threshold value, and use the extraction steam mass flow rate in S5 as the real-time calculated value of the turbine extraction steam mass flow rate.

[0016] A second aspect of the present invention provides a readable medium having instructions stored thereon, which, when executed on an electronic device, causes the electronic device to execute the method for real-time determination of the extraction flow rate of a nuclear power saturated steam turbine.

[0017] According to a third aspect of the present invention, there is provided an electronic device comprising a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor is used to execute the method for real-time determination of extraction flow of a nuclear power saturated steam turbine when executing the program.

[0018] Compared with the prior art, the embodiments of the present invention have at least one of the following beneficial effects:

[0019] The present invention provides a method for real-time determination of the extraction flow rate of a nuclear power saturated steam turbine based on a feedwater heater mechanism model. The method can be calculated based on the DCS measuring point data of the nuclear power plant's turbine system and the heat extraction system. The final result has the advantages of small calculation error, strong anti-interference and high real-time performance compared with the existing method.

[0020] In the above method of the present invention, the measuring point data required for the real-time calculation of the extraction flow of the nuclear power saturated steam turbine are all provided by the DCS real-time database. No additional measuring points or other expensive hardware are required on site. Only the corresponding software modules need to be added to the existing control system, which is low-cost.

[0021] The present invention provides a method for real-time determination of the extraction flow of a nuclear power saturated steam turbine based on a feedwater heater mechanism model, which can be used for real-time monitoring of the extraction mass flow of a saturated steam turbine of a nuclear power unit, and is one of the supporting technologies for full-process simulation and digital twinning of nuclear power units. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objectives and advantages of the present invention will become more apparent from a reading of the detailed description of non-limiting embodiments made with reference to the following accompanying drawings.

[0023] Figure 1 is a structural diagram of a heat recovery steam extraction system in one embodiment of the present invention;

[0024] Figure 2 is a schematic structural diagram of a feedwater heater in one embodiment of the present invention;

[0025] Figure 3 It is a flow chart of a method for real-time determination of extraction flow rate of a nuclear power saturated steam turbine based on a feedwater heater mechanism model in one embodiment of the present invention;

[0026] Figure 4 is a graph showing a change in output power of a nuclear power unit in one embodiment of the present invention;

[0027] Figure 5 It is a comparison between the calculated value of the extraction steam flow rate of the 7th stage high pressure feedwater heater in one embodiment of the present invention and the calculated results of several existing methods;

[0028] Figure 6 It is a comparison between the calculated value of the extraction steam flow rate of the 6th stage high pressure feedwater heater in one embodiment of the present invention and the calculated results of several existing methods;

[0029] Figure 7 The figure is a comparison between the calculation result of the extraction steam flow rate of the 1st to 4th stage low-pressure feedwater heater and the value of the enthalpy balance calculation result in one embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0031] Figure 1 This is a structural diagram of a heat recovery steam extraction system in an embodiment of the present invention. This embodiment belongs to a 1000MW nuclear power unit, and its heat recovery steam extraction system adopts 7-stage reheating, of which 1-4 stages are low-pressure feedwater heaters, and 6-7 stages are high-pressure feedwater heaters.

[0032] Figure 2 The feedwater heater is a schematic diagram of the structure of an embodiment of the present invention. According to the spatial position and aggregation state of the working fluid, the feedwater heater can be divided into three parts: tube-side feedwater, shell-side steam condensation section and drain cooling section. This part is an existing structure and will not be described in detail.

[0033] In an embodiment of the present invention, corresponding to the above-mentioned working fluid division, a mechanism model of the feedwater heater is constructed, the heat exchange capacity of the feedwater heater is calculated in real time, and the real-time steam extraction mass flow rate and the steam drainage mass flow rate are calculated according to the volume of the shell-side steam extraction space and the steam extraction pressure.

[0034] Specifically, the method for real-time determination of the extraction flow rate of a nuclear power saturated steam turbine in an embodiment of the present invention is based on a feedwater heater mechanism model, which includes a tube-side feedwater model, a shell-side steam condensation section model and a shell-side drain cooling section model; wherein: the tube-side feedwater model is used to describe the flow state of feedwater along the heat exchange tube and the heat exchange between it and the shell-side steam and drain; the shell-side steam condensation section model is used to describe the condensation process of shell-side steam, and the influence of steam condensation on the shell-side pressure and the extraction mass flow rate; the shell-side drain cooling section model describes the flow and heat release process of the drain.

[0035] like Figure 3 As shown, based on the above-mentioned feedwater heater mechanism model, the real-time determination method of the extraction flow rate of the nuclear power saturated steam turbine in this embodiment includes the following steps:

[0036] S1: Acquire the equipment structural parameters of the feedwater heater and the operation data of the feedwater heater at a given time;

[0037] S2: Determine the extraction steam specific enthalpy at the given time according to the equipment structural parameters and operation data obtained in S1;

[0038] S3: Based on the extraction specific enthalpy obtained in S2, the real-time heat flow and heat transfer coefficient of the steam condensation section and the drain cooling section are calculated respectively;

[0039] S4: Based on the heat transfer coefficient obtained in S3, the tube feedwater model in the feedwater heater mechanism model is solved to obtain the temperature, specific enthalpy and flow rate distribution of the feedwater;

[0040] S5: Based on the extraction steam specific enthalpy obtained in S2 and the real-time heat flow obtained in S3, the shell-side steam condensation section model in the feedwater heater mechanism model is solved to obtain the extraction steam mass flow rate and condensate mass flow rate;

[0041] S6: Based on the temperature, specific enthalpy and flow rate distribution of the feed water obtained in S3 and the mass flow rate of the condensate obtained in S5, the shell-side drain cooling section model in the feed water heater mechanism model is solved to obtain the temperature, specific enthalpy and flow rate distribution of the drain;

[0042] S7: Substitute the results of S4-S6 back into S3, iterate S3-S6 several times, and terminate the calculation when the difference between the extraction steam mass flow rates obtained in S5 in two adjacent calculations is less than the threshold value, and use the extraction steam mass flow rate in S5 as the real-time calculated value of the turbine extraction steam mass flow rate.

[0043] The above-mentioned embodiment of the present invention can be used to determine the extraction mass flow rate of a nuclear power saturated steam turbine in real time, and the obtained result has the advantages of small calculation error, strong anti-interference and high real-time performance compared with the existing method.

[0044] In S1 of the above embodiment, the equipment structural parameters of the feedwater heater can be obtained from the equipment manual or provided by the manufacturer. The operation data may include the feedwater temperature, pressure and mass flow rate at the tube side inlet, the shell side extraction pressure, the specific enthalpy and mass flow rate of the upper drain at the shell side inlet, etc., all of which can be provided by the DCS real-time database.

[0045] As a preferred embodiment, in S2, in order to calculate the extraction specific enthalpy at a given time, the following formula can be used for calculation:

[0046]

[0047] In the formula, h es and h ms are the specific enthalpy of extraction steam and main steam, kJ / kg; x ms is the dryness of the main steam, dimensionless; Δh s is the isentropic enthalpy drop of the turbine stage, kJ / kg; η dry and α are the dry-base internal efficiency and Baumann coefficient of the steam turbine, respectively. They are dimensionless constants obtained from the steam turbine code. V,es and h L,esare the saturated steam specific enthalpy and saturated water specific enthalpy corresponding to the extraction pressure, kJ / kg; ρ es and ρ ms are the density of extraction steam and main steam, kg / m 3 ; κ is the logarithmic mean adiabatic index of the level group, dimensionless.

[0048] By using the above preferred embodiment to calculate the extraction steam specific enthalpy at a given time, an online estimation result of the extraction steam specific enthalpy can be obtained, which solves the problem that the extraction steam specific enthalpy cannot be measured online.

[0049] Further, as a preferred embodiment, the isentropic enthalpy drop Δh of the steam turbine stage group s It is calculated using the following formula:

[0050]

[0051]

[0052] Where κ is the logarithmic mean adiabatic index of the level group, dimensionless; p es and p ms are the pressures of extraction steam and main steam, MPa; ρ es and ρ ms are the density of extraction steam and main steam, kg / m 3 .

[0053] As a preferred embodiment, in S3, the real-time heat flow of the steam condensation section and the drain cooling section are calculated using the following formulas:

[0054]

[0055]

[0056] In the formula, Q V and Q L are the heat flow rates of the steam condensation section and the drain cooling section of the feedwater heater, kW; S V and S L are the heat exchange areas of the steam condensation section and the drain cooling section, m 2 ; K V and K L are the heat transfer coefficients of the steam condensation section and the drain cooling section, kW / m 2 / K;T es 、T fw and T dw They are extraction temperature, feed water temperature and drain temperature, K respectively.

[0057] The real-time heat flow of the steam condensation section and the drain cooling section obtained in the above preferred embodiment of the present invention describes the energy coupling relationship between the tube-side feed water and the shell-side working fluid, which is consistent with actual applications.

[0058] Further, as a preferred embodiment, the heat transfer coefficient K of the steam condensation section is V and the heat transfer coefficient K of the drain cooling section L The following formulas are used to calculate:

[0059] K V =(K fw -1 +K es -1 ) -1

[0060] K L =(K fw -1 +K dw -1 ) -1

[0061]

[0062]

[0063]

[0064] In the formula, K fw , K es and K dw They are the surface heat transfer coefficients of feed water, steam and drain, kW / m 2 / K;w fw and w dw are the flow rates of water supply and drainage, m / s; ρ fw and ρ dw are the densities of feed water and drain water, kg / m 3 ,λ fw and λ dw are the thermal conductivity of feed water and drain water, kW / m / K; c p,fw and c p,dw are the constant pressure specific heat capacity of feed water and drain respectively, kW / kg / K; μ fw and μ dw are the dynamic viscosities of feed water and hydrophobic water, Pa·s; d i is the inner diameter of the heat exchange tube, m; d e,dw h is the equivalent diameter of the shell side of the drain cooling section; V,es and h L,es They are the saturated steam specific enthalpy and saturated water specific enthalpy corresponding to the extraction pressure, kJ / kg; g is the gravitational acceleration, m / s2 ; L,es is the saturated water thermal conductivity corresponding to the extraction pressure, kW / m / K; ρ L,es is the saturated water density corresponding to the extraction pressure, kg / m 3 ;μ L,es is the saturated water dynamic viscosity corresponding to the extraction pressure, Pa·s; d o is the outer diameter of the heat exchange tube, m.

[0065] As a preferred embodiment, in S4, the pipe-side water supply model is as follows:

[0066]

[0067]

[0068] In the formula, ρ fw is the density of the feed water, kg / m 3 ;w fw is the water flow rate, m / s; h fw is the specific enthalpy of feed water, kJ / kg; K V and K L are the heat transfer coefficients of the steam condensation section and the drain cooling section, kW / m 2 / K;S V and S L are the heat exchange areas of the steam condensation section and the drain cooling section, m 2 ; T es 、T fw and T dw are respectively the extraction temperature, feed water temperature and drain temperature, K; V fw is the volume of space occupied by water supply, m 3 .

[0069] In the above preferred embodiment of the present invention, the temperature, specific enthalpy and flow rate distribution of the feed water in the heat exchange tube can be calculated by using the tube-side water supply model, thus solving the problem of no measurement values ​​of the above variables.

[0070] As a preferred embodiment, in S5, the shell-side extraction steam condensation section model is as follows, and the mass flow rate of extraction steam and condensate can be calculated by using this model:

[0071]

[0072]

[0073] M V =V V ρ V,es

[0074] E V =M V hV,es

[0075] Where M V is the total mass of steam, kg; E V is the total energy of steam, kJ; V V is the steam volume, m 3 ρ V,es is the saturated dry steam density corresponding to the extraction pressure, kg / m 3 ;h V,es and h L,es are the specific enthalpy of saturated dry steam and saturated water corresponding to the extraction pressure, kJ / kg; D es is the extraction steam mass flow rate, kg / s; h es is the specific enthalpy of extraction steam, kJ / kg; D dw,in is the mass flow rate of the upstream feedwater heater drain, kg / s; h dw,in is the specific enthalpy of the upstream feedwater heater drain, kJ / kg; D MSR is the steam-water separation reheater drain mass flow rate, kg / s; h MSR is the specific enthalpy of water separation reheater water discharge, kJ / kg; D con is the condensate mass flow rate, kg / s; Q V is the heat flow rate of the steam condensation section and the drain cooling section, kW.

[0076] As a preferred embodiment, in S6, the shell-side drain cooling section model is as follows, and the temperature, specific enthalpy, and flow rate distribution of the drain can be calculated using this model:

[0077]

[0078]

[0079] In the formula, ρ dw is the density of the hydrophobic substance, kg / m 3 ;w dw is the drainage flow rate, m / s; h dw is the specific enthalpy of hydrophobicity, kJ / kg; K L is the heat transfer coefficient of the drain cooling section, kW / m 2 / K;S L is the heat exchange area of ​​the drain cooling section, m 2 ; T fw and T dw are the feed water temperature and drain water temperature, K; V dw is the volume of the drain cooling section, m 3 .

[0080] As a preferred embodiment, the boundary conditions of the shell-side drain cooling section model are:

[0081]

[0082] h dw | x＝0 =h L,es

[0083] In the formula, w dw | x＝0 is the drain flow rate at the inlet of the drain cooling section, m / s; h dw | x＝0 is the specific enthalpy of the drain at the inlet of the drain cooling section, kJ / kg; A dw is the flow area of ​​the drain cooling section, m 2 ρ dw is the density of the drain in the drain cooling section, kg / m 3 ;h L,es is the specific enthalpy of saturated dry steam corresponding to the extraction pressure, kJ / kg.

[0084] As a preferred embodiment, in S7, S3-S6 are iterated several times, and the calculation is terminated when the difference between two adjacent results is less than a threshold. The termination condition is:

[0085] ||D es (i)-D es (i-1)||2<ε es

[0086] Where D es (i) represents the extraction steam mass flow rate obtained by the i-th iteration calculation, kg / s; ε es It is a threshold value set according to the accuracy requirement, and is set to 0.01 kg / s in this embodiment. Of course, in other embodiments, other threshold values ​​can also be set according to actual needs.

[0087] In the embodiment of the method for real-time determination of extraction flow rate of nuclear power saturated steam turbine based on feedwater heater mechanism model of the present invention, DCS measured data of the nuclear power unit under different loads of the embodiment is obtained. Among them, the unit output power is shown in Figure 4 .

[0088] Figure 5 , Figure 6The comparisons are respectively between the calculated values ​​of the extraction flow rates of the 7th and 6th stage high-pressure feedwater heaters in an embodiment of the present invention and the calculation results of several existing methods: compared with the commonly used enthalpy balance calculation method, the method of the embodiment of the present invention has strong anti-interference ability and the result has better stability; compared with the shell-side working fluid mass conservation method, the drain flow data it relies on is controlled by the drain regulating valve and cannot directly reflect the internal state of the feedwater heater, resulting in unreliable calculation results of this method, while the method of the embodiment of the present invention has the advantage of not being affected by the drain mass flow rate; compared with the Bernoulli equation and the Flugel formula, the method of the embodiment of the present invention has a small error and will not lead to the accumulation of mass errors.

[0089] Figure 7 The calculation results of the extraction steam flow of the 1st to 4th stage low-pressure feedwater heaters in one embodiment of the present invention are compared with the enthalpy balance calculation results, wherein the enthalpy balance results are averaged per minute, and the average relative error is about 0.6%.

[0090] Based on the same technical concept, in another embodiment of the present invention, a readable medium is also provided, on which instructions are stored. When the instructions are executed on an electronic device, the electronic device executes the real-time determination method of the extraction flow rate of a nuclear power saturated steam turbine according to any of the above embodiments.

[0091] Based on the same technical concept, in another embodiment of the present invention, an electronic device is also provided, including a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the program, it is used to execute the real-time determination method of the extraction flow rate of a nuclear power saturated steam turbine of any of the above embodiments.

[0092] The following takes the sixth-stage feedwater heater of the embodiment of the present invention as an example, and describes the implementation of the technical solution of the present invention in combination with the detailed equipment structure and its operation:

[0093] S1, obtaining the equipment structural parameters of the feedwater heater, including: the inner diameter of the heat exchange tube is 0.013m and the outer diameter is 0.016m, the length of the heat exchange tube is 8.2m, the length of the feedwater heater is 11.0m, and the inner diameter of the feedwater heater is 1.1m;

[0094] The operating data of the feedwater heater at a given time include: main steam specific enthalpy 2776kJ / kg; tube side inlet feedwater temperature 447.6K, pressure 7.927MPa and mass flow rate 1.565kg / s; shell side extraction pressure 1.824MPa, shell side inlet upper drain specific enthalpy 895.6kJ / kg and mass flow rate 82.4512kg / s;

[0095] S2, in order to calculate the extraction steam specific enthalpy at a given time, can be calculated using the following formula:

[0096]

[0097] In the formula, h ms is the specific enthalpy of the main steam, which is 2776 kJ / kg; x ms is the dryness of the main steam, which is 99.48%; η dry and α are the dry-base internal efficiency and Baumann coefficient of the steam turbine, which are 0.9626 and 1.1 respectively; h V,es and h L,es They are the saturated steam specific enthalpy and saturated water specific enthalpy corresponding to the extraction pressure, which are 2798 kJ / kg and 902.1 kJ / kg respectively;

[0098] Get the extraction steam specific enthalpy h at a given time es 2588kJ / kg;

[0099] Among them, the isentropic enthalpy drop of the turbine stage group Δh s It is 209.0 kJ / kg, calculated using the following formula:

[0100]

[0101]

[0102] Where κ is the logarithmic mean adiabatic index of the stage group, and the calculated result is 1.085; p es and p ms are the pressures of extraction steam and main steam, 1.944MPa and 6.005MPa respectively; ρ es and ρ ms The density of the extraction steam and main steam are 10.96 kg / m 3 and 31.00kg / m 3 .

[0103] S3, the real-time heat flow of the steam condensation section and the drain cooling section are calculated using the following formulas:

[0104]

[0105]

[0106] In the formula, S V and S L The heat exchange areas of the steam condensation section and the drain cooling section are 2127m 2 and 521m 2 ; K V and K L The heat transfer coefficients of the steam condensation section and the drain cooling section are 6.7261kW / m 2 / K to 12.76kW / m2 / K and 1.834kW / m 2 / K to 1.736kW / m 2 / K distribution; T es is the extraction temperature, which is 480.9K; T fw and T dw They are the extraction temperature, feed water temperature and drain temperature, which are distributed from 447.6K to 480.7K and 449.0K to 480.7K respectively.

[0107] Get the heat flow Q of the steam condensation section and drain cooling section of the feedwater heater V and Q L , respectively 9.655×10 4 kW and 1.823×10 4 kW;

[0108] Heat transfer coefficient of steam condensation section K V and the heat transfer coefficient K of the drain cooling section L The following formulas are used to calculate:

[0109] K V =(K fw -1 +K es -1 ) -1

[0110] K L =(K fw -1 +K dw -1 ) -1

[0111] In the formula, K fw is the surface heat transfer coefficient of the feed water, which is 16.74kW / m 2 / K to 18.00kW / m 2 / K distribution; K es is the surface heat transfer coefficient of steam, which is 11.25kW / m 2 / K to 43.79kW / m 2 / K distribution; K dw is the surface heat transfer coefficient of the hydrophobic surface, which is 2.059kW / m 2 / K to 1.922kW / m 2 / K distribution; calculated using the following formulas:

[0112]

[0113]

[0114]

[0115] w fw and w dw are the flow rates of water supply and drainage, which are distributed from 2.027m / s to 2.120m / s and 0.1352m / s to 0.1410m / s respectively; ρ fw and ρ dw The densities of feed water and drain water are 896.8kg / m 3 Up to 857.8kg / m 3 and 891.7kg / m 3 Up to 855.3kg / m 3 The distribution of fw and λ dw are the thermal conductivities of feed water and drain water, with distributions ranging from 0.6794kW / m / K to 0.6601kW / m / K and 0.6771kW / m / K to 0.6582kW / m / K, respectively; c p,fw and c p,dw are the constant pressure specific heat capacities of feed water and drain water, with distributions ranging from 4.3564kW / kg / K to 4.4964kW / kg / K and 4.386kW / kg / K to 4.534kW / kg / K respectively; μ fw and μ dw are the dynamic viscosities of water supply and water drainage, which are 1.572×10 -4 Pa·s to 1.310×10 -4 Pa·s and 1.544×10 -4 Pa·s to 1.295×10 -4 Distribution of Pa·s; d i is the inner diameter of the heat exchange tube, 0.013m; d e,dw is the equivalent diameter of the shell side of the drain cooling section, which is 0.023m; h V,es and h L,es They are the saturated steam specific enthalpy and saturated water specific enthalpy corresponding to the extraction pressure, which are 2796 kJ / kg and 887.6 kJ / kg respectively; g is the acceleration due to gravity, which is 9.8 m / s 2 ; L,es is the saturated water thermal conductivity corresponding to the extraction pressure, which is 0.6579kW / m / K; ρ L,es is the saturated water density corresponding to the extraction pressure, 855.4 kg / m 3 ;μ L,es is the saturated water dynamic viscosity corresponding to the extraction pressure, 1.293×10 -4 Pa·s;d o is the outer diameter of the heat exchange tube, 0.016m.

[0116] S4, pipe water supply model is as follows:

[0117]

[0118]

[0119] In the formula, ρ fw is the density of the feed water, kg / m 3 ; K V and K L are the heat transfer coefficients of the steam condensation section and the drain cooling section, kW / m 2 / K;S V and S L are the heat exchange areas of the steam condensation section and the drain cooling section, m 2 ; T es 、T fw and T dw are respectively the extraction temperature, feed water temperature and drain temperature, K; V fw is the volume of space occupied by water supply, m 3 .

[0120] Get the water flow rate w fw The distribution is from 2.027m / s to 2.119m / s; the specific enthalpy of feed water is h fw The distribution ranges from 741.3 kJ / kg to 888.0 kJ / kg;

[0121] S5, the shell side extraction steam condensation section model is as follows, using this model, the mass flow rate of extraction steam and condensate can be calculated:

[0122]

[0123]

[0124] M V =V V ρ V,es

[0125] E V =M V h V,es

[0126] Where M V is the total mass of steam, which is 275.9 kg; E V is the total energy of steam, which is 7.717×10 5 kJ; V V is the steam volume, which is 30.14m 3 ρ V,es is the saturated dry steam density corresponding to the extraction pressure, which is 9.179 kg / m 3 ;h V,es and hL,es The specific enthalpies of saturated dry steam and saturated water corresponding to the extraction pressure are 2796 kJ / kg and 887.6 kJ / kg respectively; h es is the specific enthalpy of extraction steam, which is 2588 kJ / kg; D dw,in is the mass flow rate of the upstream feedwater heater drain, which is 82.45 kg / s; h dw,in is the specific enthalpy of the upstream feedwater heater drain, which is 895.6 kJ / kg; D MSR is the water separation reheater drain mass flow rate, which is 129.0 kg / s; h MSR is the specific enthalpy of water removal in the steam-water separation reheater, which is 1030 kJ / kg;

[0127] Get the extraction steam mass flow rate D es 107.7kg / s; condensate mass flow rate D con 255.8kg / s;

[0128] S6, the shell-side drain cooling section model is as follows, using this model to calculate the temperature, specific enthalpy, and flow rate distribution of the drain:

[0129]

[0130]

[0131] In the formula, ρ dw is the density of the hydrophobic, which is 892.0 kg / m 3 Up to 855.7kg / m 3 The distribution of V dw is the volume of the drain cooling section, 11.67m 3 ;

[0132] Get the hydrophobic flow rate w dw The distribution is from 0.1412m / s to 0.1353m / s; the hydrophobic specific enthalpy h dw The distribution ranges from 744.9 kJ / kg to 887.3 kJ / kg;

[0133] S7, iterate and calculate S3-S6 several times, and terminate the calculation when the difference between two consecutive results is less than the threshold. The termination condition is:

[0134] ||D es (i)-D es (i-1)||2<ε es

[0135] Where D es (i) represents the extraction steam mass flow rate obtained by the i-th iteration calculation, kg / s; ε esIt is a threshold value set according to the accuracy requirement, and is set to 0.01 kg / s in this embodiment. The steam extraction mass flow rate that meets the termination condition is 108.320 kg / s.

[0136] The above-mentioned embodiment of the present invention improves the accuracy of obtaining parameters in each step through model design in each step, and can be used for real-time determination of steam extraction mass flow rate of nuclear power unit steam turbine. The result has the advantages of small calculation error, strong anti-interference and high real-time performance compared with the existing method. The measurement point data required for the real-time calculation of the extraction flow rate of nuclear power saturated steam turbine are all provided by the DCS real-time database. No additional measurement points or other expensive hardware are required on site. Only the corresponding software calculation module needs to be added to the existing control system, which is low in cost. The result obtained by the embodiment of the present invention can be directly used for real-time online monitoring of the extraction flow rate of nuclear power saturated steam turbine. Specifically, after obtaining the real-time value of the above-mentioned extraction mass flow rate, it can be compared with the set monitoring threshold. If it exceeds the set monitoring threshold, an early warning is issued, which plays an important auxiliary role in the operation of nuclear power saturated steam turbine.

[0137] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for real-time determination of extraction flow rate of a nuclear power saturated steam turbine, characterized in that: The method is based on a feedwater heater mechanism model, which includes a tube-side feedwater model, a shell-side steam condensation section model, and a shell-side drain cooling section model; The method comprises: S1: Acquire the equipment structural parameters of the feedwater heater and the operation data of the feedwater heater at a given time; S2: Determine the extraction steam specific enthalpy at the given time according to the equipment structural parameters and operation data obtained in S1; S3: Based on the extraction specific enthalpy obtained in S2 above, the real-time heat flow and heat transfer coefficient of the steam condensation section and the drain cooling section are calculated respectively; S4: Based on the heat transfer coefficient obtained in S3 above, solve the tube feedwater model in the feedwater heater mechanism model to obtain the temperature, specific enthalpy and flow rate distribution of the feedwater; S5: Based on the extraction steam specific enthalpy obtained in S2 and the real-time heat flow obtained in S3, the shell-side steam condensation section model in the feedwater heater mechanism model is solved to obtain the extraction steam mass flow rate and the condensate mass flow rate; S6: Based on the temperature, specific enthalpy and flow rate distribution of the feed water obtained in S3 and the mass flow rate of the condensate obtained in S5, the shell-side drain cooling section model in the feed water heater mechanism model is solved to obtain the temperature, specific enthalpy and flow rate distribution of the drain; S7: Substitute the results of S4-S6 back into S3, iterate S3-S6 several times, and terminate the calculation when the difference between the extraction steam mass flow rates obtained in S5 in two consecutive calculations is less than a threshold value, and use the extraction steam mass flow rate in S5 as the real-time calculated value of the steam turbine extraction steam mass flow rate; In S2, the extraction steam specific enthalpy is calculated using the following formula: in: In the formula, h es and h ms are the specific enthalpy of extraction steam and main steam, kJ / kg; x ms is the dryness of the main steam, dimensionless; Δh s is the isentropic enthalpy drop of the turbine stage, kJ / kg; η dry and α are the dry-base internal efficiency and Baumann coefficient of the steam turbine, respectively, which are dimensionless constants obtained from the steam turbine code; es and p ms are respectively the pressure of extraction steam and main steam, MPa; h V,es and h L,es are the saturated steam specific enthalpy and saturated water specific enthalpy corresponding to the extraction pressure, kJ / kg; ρ es and ρ ms are the densities of extraction steam and main steam, kg / m 3 ;κ is the logarithmic mean adiabatic index of the level group, dimensionless; In S3, the real-time heat flow of the steam condensation section and the drain cooling section is calculated using the following formulas: in: K V =(K fw -1 +K es -1 ) -1 K L =(K fw -1 +K dw -1 ) -1 In the formula, Q V and Q L are the heat flow rates of the steam condensation section and the drain cooling section, kW; S V and S L are the heat exchange areas of the steam condensation section and the drain cooling section, m 2 ; K V and K L are the heat transfer coefficients of the steam condensation section and the drain cooling section, kW / m 2 / K;T es , T fw and T dw are respectively the extraction temperature, feed water temperature and drain temperature, K; K fw , K es and K dw They are the surface heat transfer coefficients of feed water, steam and drain, kW / m 2 / K;w fw and w dw are the flow rates of water supply and drainage, m / s; ρ fw and ρ dw are the densities of feed water and drain water, kg / m 3 ,λ fw and λ dw are the thermal conductivity of feed water and drain water, kW / m / K; c p,fw and c p,dw are the constant pressure specific heat capacity of feed water and drain respectively, kW / kg / K; μ fw and μ dw are the dynamic viscosities of feed water and hydrophobic water, Pa·s; h V,es and h L,es They are the saturated steam specific enthalpy and saturated water specific enthalpy corresponding to the extraction pressure, kJ / kg; d i is the inner diameter of the heat exchange tube, m; d e,dw is the equivalent diameter of the shell side of the drain cooling section; g is the acceleration due to gravity, m / s 2 ; L,es is the saturated water thermal conductivity corresponding to the extraction pressure, kW / m / K; ρ L,es is the saturated water density corresponding to the extraction pressure, kg / m 3 ;μ L,es is the saturated water dynamic viscosity corresponding to the extraction pressure, Pa·s; d o is the outer diameter of the heat exchange tube, m; In S4, the pipe-side water supply model is as follows: In the formula, ρ fw is the density of the feed water, kg / m 3 ;w fw is the water flow rate, m / s, and the velocity distribution is obtained by solving the partial differential equation; h fw is the specific enthalpy of feed water, kJ / kg; K V and K L are the heat transfer coefficients of the steam condensation section and the drain cooling section, kW / m 2 / K;S V and S L are the heat exchange areas of the steam condensation section and the drain cooling section, m 2 ; T es , T fw and T dw are respectively the extraction temperature, feed water temperature and drain temperature, K; V fw is the volume of space occupied by water supply, m 3 ; In S5, the shell-side steam condensation section model is as follows: M V =V V r V,es E V =M V h V,es Where M V is the total mass of steam, kg; E V is the total energy of steam, kJ; V V is the steam volume, m 3 ρ V,es is the saturated dry steam density corresponding to the extraction pressure, kg / m 3 ;h V,es and h L,es are the specific enthalpy of saturated dry steam and saturated water corresponding to the extraction pressure, kJ / kg; D es is the extraction steam mass flow rate, kg / s; h es is the specific enthalpy of extraction steam, kJ / kg; D dw,in is the mass flow rate of the upstream feedwater heater drain, kg / s; h dw,in is the specific enthalpy of the upstream feedwater heater drain, kJ / kg; D MSR is the steam-water separation reheater drain mass flow rate, kg / s; h MSR is the specific enthalpy of water separation reheater water discharge, kJ / kg; D con is the condensate mass flow rate, kg / s; Q V is the heat flow rate of the steam condensation section and the drain cooling section, kW; In S6, the shell-side drain cooling section model is as follows: In the formula, ρ dw is the density of the hydrophobic substance, kg / m 3 ;w dw is the drainage flow rate, m / s; h dw is the specific enthalpy of hydrophobicity, kJ / kg; K L is the heat transfer coefficient of the drain cooling section, kW / m 2 / K;S L is the heat exchange area of ​​the drain cooling section, m 2 ; T fw and T dw are the feed water temperature and drain water temperature, K; V dw is the volume of the drain cooling section, m 3 ; The boundary conditions of the shell-side drain cooling section model are: h dw | x＝0 =h L,es In the formula, w dw | x＝0 is the drain flow rate at the inlet of the drain cooling section, m / s; h dw | x＝0 is the specific enthalpy of the drain at the inlet of the drain cooling section, kJ / kg; A dw is the flow area of ​​the drain cooling section; ρ dw is the density of the drain in the drain cooling section, kg / m 3 ;h L,es It is the specific enthalpy of saturated dry steam corresponding to the extraction pressure.

2. The method for real-time determination of extraction flow rate of a nuclear power saturated steam turbine according to claim 1, characterized in that: In S1, the operation data include the feed water temperature, pressure and mass flow rate at the tube side inlet, the shell side extraction steam pressure, and the specific enthalpy and mass flow rate of the upper drain at the shell side inlet.

3. The method for real-time determination of extraction flow rate of a nuclear power saturated steam turbine according to claim 1, characterized in that: In S7, iterate S3-S6 several times, and terminate the calculation when the difference between two consecutive results is less than the threshold. The termination condition is: ||D es (i)-D es (i-1)||2<ε es Where D es (i) represents the extraction steam mass flow rate obtained by the i-th iteration calculation, kg / s; ε es is a pre-set threshold, kg / s.

4. A readable medium, characterized in that: The readable medium stores instructions, which, when executed on an electronic device, enable the electronic device to execute the real-time determination method for the extraction flow rate of a nuclear power saturated steam turbine according to any one of claims 1 to 3.

5. An electronic device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that: When the processor executes the program, it is used to execute the real-time determination method of the extraction flow rate of the nuclear power saturated steam turbine according to any one of claims 1 to 3.

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