CN106894853B - Condensing turbine cold end diagnosis of energy saving method - Google Patents

Condensing turbine cold end diagnosis of energy saving method Download PDF

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CN106894853B
CN106894853B CN201710059889.4A CN201710059889A CN106894853B CN 106894853 B CN106894853 B CN 106894853B CN 201710059889 A CN201710059889 A CN 201710059889A CN 106894853 B CN106894853 B CN 106894853B
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condenser
cold end
heat exchange
end factor
steam turbine
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CN106894853A (en
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徐曙
蒋北华
程贵兵
李明
焦庆丰
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State Grid Corp of China SGCC
Electric Power Research Institute of State Grid Hunan Electric Power Co Ltd
State Grid Hunan Electric Power Co Ltd
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State Grid Corp of China SGCC
Electric Power Research Institute of State Grid Hunan Electric Power Co Ltd
State Grid Hunan Electric Power Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F01D21/003—Arrangements for testing or measuring
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/17—Mechanical parametric or variational design
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2260/00—Function
    • F05D2260/80—Diagnostics

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  • Pure & Applied Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Evolutionary Computation (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
  • Control Of Turbines (AREA)

Abstract

The invention discloses a kind of condensing turbine cold end diagnosis of energy saving method, implementation steps include：Measure the exhaust temperature (or turbine back pressure) before the change of condensing turbine cold end factor；Measure recirculated water water-in and water-out temperature before cold end factor changes；Determine possible changed cold end factor, and determine the parameter of each cold end factor before and after change；Turbine discharge temperature after the change of cold end factor is calculated by above parameter, obtains the fall of turbine back pressure after the change of cold end factor.The present invention, which has, calculates that simple, required parameter is few, and accuracy is high, the advantages of being easily achieved, and overcomes the drawbacks of current cold end diagnosis of energy saving needs to provide whole cold end variables, realizes the energy saving real-time diagnosis of high-precision cold end.

Description

Condensing steam turbine cold end energy-saving diagnosis method
Technical Field
The invention relates to the technical field of electric power engineering, in particular to a cold end energy-saving diagnosis method for a condensing steam turbine.
Background
In the thermodynamic cycle of a condensing steam turbine unit of a modern large-scale power station, a condenser is taken as a core, a low-pressure cylinder of an internal steam turbine is connected, and a water supply system is connected externally to form a cold end system of the power station. Condenser pressure (namely, turbine backpressure) has a great influence on unit economy, and how to reduce the unit backpressure as far as possible within an allowable range of an external environment is the work of vital importance in energy conservation of a thermal power plant. The cold end factors influencing the back pressure mainly comprise circulating water inlet temperature, circulating water flow, condenser cleanliness, condenser heat load, condenser characteristics and the like. For the running unit, except the characteristic of the condenser is always unchanged, other cold end parameters are continuously changed along with the conditions of running adjustment, external environment, unit load and the like; in addition, cold end factors influence each other, interfering with each other, for example it may be advantageous to start a backup circulation pump when the condenser cleanliness is poor, but it may be disadvantageous to start a backup circulation pump when the condenser cleanliness is good. These problems increase the difficulty of cold end energy saving operation.
The influences of changes of cold end factors on backpressure can be obtained through calculation by a Coleman formula of a former Soviet Union thermal research institute and Standards for Stem Surface Condensers formulated by the American society for Heat transfer, but all accurate cold end parameters are required by the methods, and most power plants lack real-time parameters such as condenser cleanliness, so that the economy of cold end adjustment or modification is difficult to calculate quantitatively in real time. At present, cold end optimization of a thermal power plant mostly depends on experience of operators, partial power plants also perform condenser performance tests, changes of the cleanliness of the condenser are not considered, and the test result can be lost if the mode is long. How to accurately diagnose the influence of the change of the cold end factors on the backpressure of the unit is an urgent need for cold end optimization and energy-saving work of the thermal power plant.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: aiming at the problems in the prior art, the cold end energy-saving diagnosis method of the condensing steam turbine is simple in calculation, few in required parameters, high in accuracy and easy to realize, overcomes the defect that all cold end variables need to be provided in the conventional cold end energy-saving diagnosis, and realizes high-accuracy cold end energy-saving real-time diagnosis.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a cold end energy-saving diagnosis method for a condensing steam turbine comprises the following implementation steps:
1) Determining the turbine discharge temperature t of a condensing turbine before changes in energy-saving related cold end factors s,1 Inlet temperature t of circulating water 1,1 And the temperature t of the circulating water outlet 2,1 Calculating the temperature rise delta t of circulating water of the condenser, the end difference delta t of the condenser and the logarithmic mean temperature difference LMTD of the condenser before the cold end factor changes according to the data, and calculating the ratio tau = delta t/LMTD of the end difference of the condenser and the logarithmic mean temperature difference of the condenser before the cold end factor changes;
2) Determining cold end factors which are likely to change, wherein the cold end factors comprise the inlet water temperature of circulating water of a condenser, the heat load of the condenser, the circulating water flow, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser;
3) Determining parameters of cold end factors before cold end factor change, including condenser circulating water inlet water temperature t 1,1 And heat load Q of condenser 1 Heat exchange area A of condenser 1 Circulating water flow G w,1 Sectional area S of single-flow heat exchange pipeline of condenser 1 Coefficient of outer diameter C of heat exchange pipeline 1,1 Correction coefficient beta of cooling water inlet temperature t,1 Tube and wall thickness correction factor beta m,1 Cleanliness coefficient beta of condenser c,1 ；
4) Determining parameters of each cold end factor after the cold end factor changes, including the inlet water temperature t of the circulating water of the condenser 1,2 Thermal load Q of condenser 2 Heat exchange area A of condenser 2 Correction coefficient beta of cooling water inlet temperature t,2 Circulating water flow G w,2 Sectional area S of single-flow heat exchange pipeline of condenser 2 Coefficient of outer diameter C of heat exchange pipeline 1,2 Tube and wall thickness correction factor beta m,2 And the cleanliness coefficient beta of the condenser c,2 ；
5) Calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) s,2 ；
In the formula (1), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1,1 And t 1,2 Respectively representing the circulating water inlet temperature before and after the cold end factor changes, Q 1 And Q 2 Respectively representing the condenser heat load before and after the cold end factor change, C 1,1 And C 1,2 Respectively represents the external diameter coefficient of the heat exchange pipeline before and after the cold end factor changes, A 1 And A 2 Respectively representing the heat exchange area, beta, of the condenser before and after the change of the cold end factor t,1 And beta t,2 Respectively represents the inlet water temperature correction coefficient, beta, of the cooling water before and after the cold end factor changes m,1 And beta m,2 Respectively representing the correction coefficients of pipe material and wall thickness before and after cold end factor change, beta c,1 And beta c,2 Respectively representing the condenser cleanliness coefficients, G, before and after the cold end factor changes w,1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor change, S 1 And S 2 Respectively representing the cross sections of single-flow heat exchange pipelines of the condenser before and after the change of the cold end factor, wherein tau represents the ratio of the end difference of the condenser before the change of the cold end factor to the logarithmic mean temperature difference of the condenser;
6) Based on a preset water and steam property table or an enthalpy-entropy diagram, the exhaust temperature t of the steam turbine after the cold end factor change is obtained s,2 And looking up a table to obtain the back pressure of the steam turbine after the cold end factor changes, subtracting the back pressure of the steam turbine before the cold end factor changes from the back pressure of the steam turbine after the cold end factor changes to obtain the back pressure reduction range of the steam turbine before and after the cold end factor changes, and outputting the back pressure reduction range of the steam turbine as the cold end energy-saving diagnosis result of the condensing steam turbine.
Preferably, the steam turbine exhaust steam temperature t after the cold end factor change is calculated according to the formula (1) in the step 5) s,2 Meanwhile, the method also comprises the steps of calculating the steam turbine exhaust temperature error delta according to the expression shown in the formula (2), and correcting the steam turbine exhaust temperature error delta after the cold end factor change according to the steam turbine exhaust temperature error deltaTemperature t s,2 ；
In the formula (2), t s,2 Indicating the exhaust temperature, t, of the turbine after the cold end factor has changed 1,2 Shows the inlet water temperature Nu of the circulating water after the cold end factor changes 1 And Nu 2 Respectively represents the number of heat transfer units of the condenser before and after the change of the cold end factor 1 And τ 2 Respectively representing the ratio of the condenser end difference before and after the cold end factor change to the mean temperature difference of the condenser logarithm.
Preferably, the number Nu of heat transfer units of the condenser before the cold end factor is changed 1 The calculation expression of (c) is shown as formula (3);
in the formula (3), k 1 Represents the heat exchange coefficient of the condenser before the cold end factor changes, A 1 Represents the heat exchange area of the condenser before the cold end factor changes, C p Is a thermal equivalent coefficient, G w,1 Showing the circulating water flow before the cold end factor changes.
Preferably, the number Nu of heat transfer units of the condenser after the cold end factor is changed 2 The calculation expression of (b) is shown in formula (4);
in the formula (4), k 2 Represents the heat exchange coefficient of the condenser after the cold end factor changes, A 2 Represents the heat exchange area of the condenser after the cold end factor changes, C p Is a thermal equivalent coefficient, G w,2 Indicating the circulating water flow after the cold end factor is changed.
Aiming at the problem of unbalanced backpressure reduction amplitude of the steam turbine under different working conditions, the invention also provides a cold end energy-saving diagnosis method of the condensing steam turbine, which comprises the following implementation steps:
s1) determining the steam turbine exhaust temperature t of the condensing steam turbine before the energy-saving related cold end factor changes s,1 Inlet temperature t of circulating water 1,1 And the temperature t of the circulating water outlet 2,1 Calculating the temperature rise delta t of circulating water of the condenser, the end difference delta t of the condenser and the logarithmic mean temperature difference LMTD of the condenser before the cold end factor changes according to the data, and calculating the ratio tau = delta t/LMTD of the end difference of the condenser and the logarithmic mean temperature difference of the condenser before the cold end factor changes;
s2) determining cold end factors which are likely to change, wherein the cold end factors comprise the circulating water inlet temperature of a condenser, the heat load of the condenser, the circulating water flow rate, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of a single-pass heat exchange pipeline of the condenser;
s3) determining parameters of each cold end factor before the cold end factor changes, including the inlet water temperature t of circulating water of the condenser 1,1 Thermal load Q of condenser 1 Heat exchange area A of condenser 1 Circulating water flow G w,1 Sectional area S of single-flow heat exchange pipeline of condenser 1 Coefficient of outer diameter C of heat exchange pipeline 1,1 Correction coefficient beta of cooling water inlet temperature t,1 Tube and wall thickness correction factor beta m,1 Cleanliness coefficient beta of condenser c , 1 ；
S4) determining various typical working conditions in a period of time, wherein at least one of the inflow water temperature of condenser circulating water, the heat load of the condenser, the circulating water flow rate, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser is different from other working conditions under each working condition, and selecting one working condition as the current working condition;
s5) determining parameters of the condensing steam turbine after the cold end factors related to energy saving change according to the current working condition, wherein the parameters after the cold end factors change comprise the inlet water temperature t of circulating water of the condenser 1,2 And the heat load of the condenserLotus Q 2 Coefficient of outer diameter C of heat exchange pipeline 1,2 Heat exchange area A of condenser 2 Correction coefficient beta of cooling water inlet temperature t,2 Pipe and wall thickness correction factor beta m,2 Cleanliness coefficient beta of condenser c,2 Circulating water flow G w,2 Sectional area S of single-flow heat exchange pipeline of condenser 2 (ii) a Calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) s,2 ；
In the formula (1), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1,1 And t 1,2 Respectively representing the circulating water inlet temperature before and after the cold end factor changes, Q 1 And Q 2 Respectively representing the condenser heat load before and after the cold end factor change, C 1,1 And C 1,2 Respectively representing the external diameter coefficient, A, of the heat exchange pipeline before and after the cold end factor changes 1 And A 2 Respectively representing the heat exchange area, beta, of the condenser before and after the change of the cold end factor t,1 And beta t,2 Respectively representing the inlet water temperature correction coefficient, beta, of the cooling water before and after the cold end factor change m,1 And beta m,2 Respectively represents the correction coefficients of the pipe and the wall thickness before and after the cold end factor changes, beta c,1 And beta c,2 Respectively representing the condenser cleanliness coefficients, G, before and after the cold end factor changes w,1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor change, S 1 And S 2 Respectively representing the cross sections of single-flow heat exchange pipelines of the condenser before and after the change of the cold end factor, wherein tau represents the ratio of the end difference of the condenser before the change of the cold end factor to the logarithmic mean temperature difference of the condenser;
s6) based on a preset water and steam property table or an enthalpy-entropy chart, according to the steam turbine exhaust temperature t after the cold end factor changes s,2 Looking up a table to obtain the back pressure of the steam turbine after the cold end factor changes, and subtracting the back pressure of the steam turbine before the cold end factor changes from the back pressure of the steam turbine after the cold end factor changes to obtain the back pressure of the steam turbine before the cold end factor changesThe backpressure reduction amplitude of the steam turbine before and after the cold end factor changes under the current working condition;
and S7) carrying out weighted average on the backpressure reduction amplitude of the steam turbine under all working conditions, and outputting the result of the weighted average as the cold end energy-saving diagnosis result of the condensing steam turbine.
Preferably, in the step S5), the steam turbine exhaust temperature t after the cold end factor change is calculated according to the formula (1) s,2 Meanwhile, the method also comprises the steps of calculating the steam turbine exhaust temperature error delta according to the expression shown in the formula (2), and correcting the steam turbine exhaust temperature t after the cold end factor change according to the steam turbine exhaust temperature error delta s,2 ；
In the formula (2), t s,2 Indicating the exhaust temperature, t, of the turbine after the cold end factor has changed 1,2 Shows the inlet water temperature Nu of the circulating water after the cold end factor changes 1 And Nu 2 Respectively representing the number of heat transfer units, tau, of the condenser before and after the change of the cold end factor 1 And τ 2 Respectively representing the ratio of the condenser end difference before and after the cold end factor change to the mean temperature difference of the condenser logarithm.
Preferably, the number Nu of heat transfer units of the condenser before the cold end factor is changed 1 The calculation expression of (c) is shown as formula (3);
in the formula (3), k 1 Represents the heat exchange coefficient, A, of the condenser before the change of the cold end factor 1 Represents the heat exchange area of the condenser before the change of the cold end factor, C p Is a thermal equivalent coefficient, G w,1 Showing the circulating water flow before the cold end factor changes.
Preferably, the number Nu of heat transfer units of the condenser after the cold end factor is changed 2 The calculation expression of (a) is shown as formula (4);
in the formula (4), k 2 Represents the heat exchange coefficient of the condenser after the cold end factor changes, A 2 Represents the heat exchange area, C, of the condenser after the cold end factor changes p Is a thermal equivalent coefficient, G w，2 Indicating the circulating water flow after the cold end factor is changed.
The cold end energy-saving diagnosis method of the condensing steam turbine has the following advantages:
1. the existing method needs to determine all cold end parameters for calculation, but part of the parameters (such as the cleanliness of a condenser) are changed continuously, and a power plant usually lacks real-time data, so that the existing method is difficult to apply in real time. The method only needs to provide the actually measured exhaust steam pressure (or exhaust steam temperature), the circulating water inlet temperature, the circulating water outlet temperature and cold end parameters before and after change, is convenient and simple, has accurate calculation and controllable error range, and is convenient to implement and popularize. The condensing steam turbine cold end energy-saving diagnosis method is simple in calculation, few in required parameters, high in accuracy and easy to realize, overcomes the defect that all cold end variables need to be provided in the conventional cold end energy-saving diagnosis, and realizes high-accuracy cold end energy-saving real-time diagnosis.
2. The condensing steam turbine cold end energy-saving diagnosis method calculates the change condition of the back pressure of the condensing steam turbine generator unit along with the factors of each cold end according to the on-site measured parameters, realizes real-time quantitative treatment of cold end economic diagnosis, and guides the cold end optimization work of the thermal power plant and the economic budget of cold end reconstruction.
Drawings
FIG. 1 is a schematic diagram of a basic process of an embodiment of the present invention.
Detailed Description
The first embodiment is as follows:
as shown in fig. 1, the implementation steps of the cold end energy saving diagnosis method for the condensing steam turbine in this embodiment include:
1) Determining the turbine exhaust temperature t of a condensing turbine before changes in energy-saving related cold end factors s,1 And the inlet water temperature t of the circulating water 1，1 And the temperature t of the circulating water outlet 2,1 (wherein the turbine exhaust temperature t s，1 The measurement can be directly carried out under the condition of ensuring the measurement accuracy, or the measurement can be carried out by measuring the backpressure of the turbine and searching based on a preset water and steam property table or an enthalpy-entropy diagram), the temperature rise delta t of circulating water of the condenser before the cold end factor change, the end difference delta t of the condenser and the logarithmic mean temperature difference LMTD of the condenser are calculated according to the data, and the ratio tau = delta t/LMTD of the end difference of the condenser and the logarithmic mean temperature difference of the condenser before the cold end factor change is calculated;
2) Determining cold end factors which are likely to change, wherein the cold end factors comprise the circulating water inlet temperature of a condenser, the heat load of the condenser, the circulating water flow, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser;
3) Determining parameters of cold end factors before cold end factor change, including condenser circulating water inlet water temperature t 1,1 Thermal load Q of condenser 1 Heat exchange area A of condenser 1 Circulating water flow G w，1 Sectional area S of single-flow heat exchange pipeline of condenser 1 And the coefficient of outer diameter C of the heat exchange pipeline 1，1 And a correction coefficient beta of the inlet water temperature of the cooling water t，1 Pipe and wall thickness correction factor beta m,1 Cleanliness coefficient beta of condenser c，1 (ii) a Wherein, the heat exchange pipeline has an outer diameter coefficient C 1，1 Correction coefficient beta of cooling water inlet temperature t,1 Tube and wall thickness correction factor beta m,1 According to Standard for Stem Surface conditioners set by the American society for Heat transfer (HEI), C 1，1 Determined by the external diameter of the heat exchange pipeline of the condenser before the cold end factor changes, beta t,1 The correction system for the inlet water temperature of the circulating water before the cold end factor changes and the wall thickness of the pipeNumber beta m,1 The method is determined by the material and the wall thickness of a heat exchange pipeline of the condenser before the cold end factor changes;
4) Determining parameters of each cold end factor after the cold end factor changes, including the inlet water temperature t of the circulating water of the condenser 1,2 Thermal load Q of condenser 2 Heat exchange area A of condenser 2 Correction coefficient beta of cooling water inlet temperature t,2 Circulating water flow G w,2 Sectional area S of single-flow heat exchange pipeline of condenser 2 Coefficient of outer diameter C of heat exchange pipeline 1,2 Pipe and wall thickness correction factor beta m,2 And the cleanliness coefficient beta of the condenser c,2 (ii) a Wherein, the heat exchange pipeline has an outer diameter coefficient C 1,2 And a correction coefficient beta of the inlet water temperature of the cooling water t,2 Tube and wall thickness correction factor beta m,2 According to Standard for Stem Surface conditioners set by the American society for Heat transfer (HEI), C 1,2 Determined by the external diameter of the heat exchange pipeline of the condenser after the cold end factor changes, beta t,2 The water inlet temperature of the circulating water is determined by the cold end factor change, and the correction coefficient beta of the pipe and the wall thickness m,2 The material and the wall thickness of a heat exchange pipeline of the condenser are determined after the cold end factors are changed;
5) Calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) s,2 ；
In the formula (1), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1,1 And t 1,2 Respectively representing the inlet water temperature of the circulating water before and after the cold end factor changes, Q 1 And Q 2 Respectively representing condenser heat load before and after cold end factor change, C 1,1 And C 1,2 Respectively representing the external diameter coefficient, A, of the heat exchange pipeline before and after the cold end factor changes 1 And A 2 Respectively represents the heat exchange area, beta, of the condenser before and after the change of the cold end factor t,1 And beta t,2 Respectively representing the inlet water temperature correction coefficient, beta, of the cooling water before and after the cold end factor change m,1 And beta m,2 Respectively representing the correction coefficients of pipe material and wall thickness before and after cold end factor change, beta c,1 And beta c,2 Respectively representing the condenser cleanliness coefficients, G, before and after the cold end factor changes w,1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor change, S 1 And S 2 Respectively representing the cross sections of single-flow heat exchange pipelines of the condenser before and after the change of the cold end factor, wherein tau represents the ratio of the end difference of the condenser before the change of the cold end factor to the logarithmic mean temperature difference of the condenser;
6) Based on a preset water and steam property table or an enthalpy-entropy diagram, according to the steam turbine exhaust temperature t after the cold end factor changes s,2 Looking up a table to obtain the back pressure of the steam turbine after the cold end factor changes, and subtracting the back pressure of the steam turbine before the cold end factor changes from the back pressure of the steam turbine after the cold end factor changes (which can be based on a preset water and steam property table or an enthalpy-entropy diagram and according to the exhaust steam temperature t of the steam turbine before the cold end factor changes s,1 And looking up a table to obtain the back pressure of the steam turbine before the cold end factor changes, or directly measuring to obtain the back pressure of the steam turbine before the cold end factor changes) to obtain the back pressure reduction amplitude of the steam turbine before and after the cold end factor changes, and outputting the back pressure reduction amplitude of the steam turbine as the cold end energy-saving diagnosis result of the condensing steam turbine.
In this embodiment, the steam turbine exhaust temperature t after the cold end factor change is calculated s,2 The derivation process of equation (1) is as follows:
because the exhaust steam of the steam turbine is in a wet steam area, the exhaust steam pressure and the exhaust steam temperature are in one-to-one correspondence. The exhaust temperature of the steam turbine can be calculated by the following formula (1-1):
t s ＝t 1 +△t+δt (1-1)
in the formula (1-1), t s Indicating the exhaust temperature, t, of the steam turbine 1 The temperature of the circulating water inlet is represented, delta t represents the temperature rise of the circulating water and is the difference between the temperature of the circulating water inlet and the temperature of the circulating water outlet of the condenser, and delta t represents the end difference of the condenser and is the difference between the exhaust temperature of the steam turbine and the temperature of the circulating water outlet of the condenser.
In addition, the heat load of the condenser can be calculated by the following formula (1-2):
Q＝G w C p △t＝kA×LMTD (1-2)
in the formula (1-2), Q represents the heat load of the condenser, G w Indicating the circulating water flow rate, C p The heat-power equivalent coefficient is represented, delta t represents the temperature rise of circulating water, k represents the heat exchange coefficient of the condenser, A represents the heat exchange area of the condenser, and LMTD represents the logarithmic mean temperature difference of the condenser.
According to the heat transfer theory, the calculation formula of the logarithmic mean temperature difference LMTD of the condenser is shown as the formula (1-3):
in the formula (1-3), Δ t represents the temperature rise of circulating water, and δ t represents the end difference of the condenser.
The calculation formula of the condenser end difference deltat can be obtained by the formulas (1-2) and (1-3) and is shown as the formula (1-4):
in the formula (1-4), delta t represents the temperature rise of circulating water, k represents the heat exchange coefficient of the condenser, A represents the heat exchange area of the condenser, and C represents p Denotes the coefficient of thermal equivalent, G w Indicating the circulating water flow.
Differentiating formula (1-4), combining formula (1-2) can give formula (1-5):
in the formula (1-5), delta t represents the end difference of the condenser, delta t represents the temperature rise of circulating water, LMTD represents the logarithmic mean temperature difference of the condenser, k represents the heat exchange coefficient of the condenser, A represents the heat exchange area of the condenser, G represents the temperature rise of the circulating water w Indicating the circulating water flow.
At both ends of formula (1-5) are addedThe combination formula (1-1) can be arranged to obtain a formula (1-5-1):
in the formula (1-5-1), t s Indicating the exhaust temperature, t, of the steam turbine 1 The inlet water temperature of the circulating water is represented, delta t represents the end difference of the condenser, delta t represents the temperature rise of the circulating water, LMTD represents the logarithmic mean temperature difference of the condenser, k represents the heat exchange coefficient of the condenser, A represents the heat exchange area of the condenser, G w Indicating the circulating water flow.
The differential relational expression of the temperature rise of the circulating water obtained by the formula (1-2) is the formula (1-6):
in the formula (1-6), Q represents the heat load of the condenser, deltat represents the temperature rise of circulating water, and G w Indicating the circulating water flow.
Substituting formula (1-6) into formula (1-5-1) to obtain formula (1-6-1):
in the formula (1-6-1), t s Indicating the exhaust temperature, t, of the turbine 1 Representing the inlet water temperature of circulating water, Q representing the heat load of the condenser, delta t representing the end difference of the condenser, LMTD representing the logarithmic mean temperature difference of the condenser, A representing the heat exchange area of the condenser, G w And k represents the flow rate of circulating water, and k represents the heat exchange coefficient of the condenser.
Exhaust temperature t of steam turbine in formula (1-6-1) s As a result, the temperature t of the inlet water of the rest of the circulating water 1 Heat load Q of condenser, and circulating water flow G w The heat exchange area A of the condenser is the operation boundary of the condenser, so if a differential formula of the heat exchange coefficient k of the condenser is obtained, the exhaust steam temperature can be obtainedDifferential relation of degree to each factor of cold end.
At present, most of steam turbine principle teaching materials adopt a Coleman formula provided by the former Soviet Union Persu thermal engineering research institute to calculate the heat exchange coefficient of a condenser, but the former Soviet Union is disassembled for more than twenty years, and the provided condenser performance test standard is not updated for a long time, so that various electric academy of China adopt the standard provided by the American society for heat transfer to carry out the condenser performance test. The American society for Heat transfer (HEI) established in 1933 and updated the 'surface steam condenser standard' formulated in 2012 to the 11 th edition is an internationally recognized condenser authoritative institution, and the standard provided by the institution is cited in appendix C in the 'operating and maintaining guide rules of condensers and vacuum systems' in the standard DL/T932-2005 in the electric power industry of China. According to Standard for Steam Surface Condensers of HEI, the heat exchange coefficient k of the condenser is calculated by the following formula (1-7);
k＝k 0 β t β m β c (1-7)
in the formula (1-7), k 0 Represents the basic heat exchange coefficient; beta is a t The water inlet temperature correction coefficient is represented and is a single-value function of the water inlet temperature, and the HEI provides a table and a curve chart respectively; beta is a m The tube and wall thickness correction coefficient is represented and determined by the material and the wall thickness of a heat exchange pipeline of the condenser, and the HEI also provides a table; beta is a c The cleanliness factor is represented and is determined by the cleanliness of the heat exchange pipeline of the condenser; k is a radical of 0 The heat exchange coefficient is determined by the outer diameter of the heat exchange pipeline of the condenser and the flow rate of circulating water.
Basic heat transfer coefficient k in the latest standard of HEI 0 Determined by means of a look-up map, but in earlier standards, the basic heat transfer coefficient k 0 Calculated as follows (1-7-1):
in the formula (1-7-1), C 1 And the coefficient represents the outer diameter of the heat exchange pipe, and v represents the flow rate of circulating water. By contrast, only when the flow rate of the circulating water is very high or very low, the flow rate is earlyThe calculation result of the phase standard is obviously different from that of the current standard, and the calculation is still carried out by adopting the early standard for convenient differentiation.
According to (1-7) and (1-7-1), the formula (1-7-2) can be obtained:
in the formula (1-7-2), k represents the heat exchange coefficient of the condenser, C 1 Denotes the coefficient of the outer diameter, G, of the heat exchange tube w Represents the flow rate of the circulating water, rho represents the density of the circulating water, S represents the one-way cross section area of a heat exchange pipeline of the condenser, and beta t Denotes a correction coefficient, beta, of the intake water temperature m Expressing the correction coefficient of pipe and wall thickness, beta c The cleanliness factor is expressed.
Differentiating the formula (1-7-2) to obtain the formula (1-7-3):
in the formula (1-7-3), k represents the heat exchange coefficient of the condenser, C 1 Expressing the coefficient of the outer diameter, beta, of the heat exchange tube t Represents a correction coefficient of inlet water temperature, beta m Expressing the correction coefficient of pipe and wall thickness, beta c Denotes the cleanliness factor, G w The circulating water flow is shown, and S represents the one-way cross section area of a heat exchange pipeline of the condenser.
Substituting the formula (1-7-3) into the formula (1-6-1) can obtain the following formula (1-8):
in the above formula, t s Indicating the exhaust temperature, t, of the steam turbine 1 Representing the inlet water temperature of circulating water, Q representing the heat load of the condenser, delta t representing the end difference of the condenser, LMTD representing the logarithmic mean temperature difference of the condenser, C 1 Expressing the coefficient of the outer diameter of the heat exchange pipeline, A expressing the condenserArea of heat exchange, beta t Represents a correction coefficient of inlet water temperature, beta m Expressing the correction coefficient of pipe and wall thickness, beta c Denotes the cleanliness factor, G w The circulating water flow is shown, and S represents the one-way cross section area of a heat exchange pipeline of the condenser.
The formulae (1-8) can be converted to the following forms, which are described as formulae (1-9):
in the above formula, the variables and the reference symbols of the parameters are the same as those in the above formula (1-8).
The result of the multivariate function being expanded by taylor's formula to ignore infinitesimal quantities of the second and above, in terms of calculus, is that the first partial derivative of the function for each variable is actually treated as a constant. Thus, by integrating the above expression with τ = δ t/LMTD and τ as a constant value, expression (1-9-1) can be obtained:
in the formula (1-9-1), the variables and the reference symbols of the parameters are the same as those in the formula (1-8). The above derivation demonstrates that the calculation of the above equation is essentially invariant regardless of changes in cold end parameters. Adding subscript "2" to cold end parameter after change, adding subscript "1" to cold end parameter before change, then the steam turbine exhaust temperature t after cold end factor change s,2 Can be calculated as in equation (1). The formula (1) has wide application prospect, and the analysis is carried out by taking the start and stop of the standby circulating water pump as an example. In a thermal power plant, the back pressure and heat consumption of a steam turbine can be reduced by starting a standby circulating water pump, so that the economy of a unit is facilitated; however, the power consumption rises after the standby circulating water pump is started, the power consumption rate of a plant is not favorable, and how to balance the power consumption rate between the standby circulating water pump and the plant is the difficulty of cold end optimization. Equation (1) provides a quantitative solution to this problem.
The formula (1-9) is the result of mathematical conversion according to the heat transfer theory and the heat exchange coefficient formula of the condenser provided by HEI, and the formula (1) omits the second orderAnd infinitesimally above, and thus, errors must be present. In this embodiment, the steam turbine exhaust temperature t after the cold end factor changes is calculated according to the formula (1) in the step 5) s,2 Meanwhile, the method also comprises the steps of calculating the steam turbine exhaust temperature error delta according to the expression shown in the formula (2), and correcting the steam turbine exhaust temperature t after the cold end factor change according to the steam turbine exhaust temperature error delta s,2 ；
In the formula (2), t s,2 Indicating the steam-turbine discharge temperature, t, after the cold-end factor has changed 1,2 Shows the inlet water temperature Nu of the circulating water after the cold end factor changes 1 And Nu 2 Respectively represents the number of heat transfer units of the condenser before and after the change of the cold end factor 1 And τ 2 Respectively representing the ratio of the condenser end difference before and after the cold end factor change to the mean temperature difference of the condenser logarithm.
In this embodiment, the derivation process of equation (2) is as follows:
the formula (2-1) can be derived from the formula (1-9);
in the formula (2-1), t s Indicating the exhaust temperature, t, of the steam turbine 1 Representing the inlet water temperature of circulating water, Q representing the heat load of the condenser, delta t representing the end difference of the condenser, LMTD representing the logarithmic mean temperature difference of the condenser, C 1 Expressing the coefficient of the outer diameter of the heat exchange pipeline, A expressing the heat exchange area of the condenser, and beta t Represents a correction coefficient of inlet water temperature, beta m Expressing the correction coefficient of pipe and wall thickness, beta c Denotes the cleanliness factor, G w The method comprises the following steps of (1) representing the flow rate of circulating water, S representing the one-way cross section area of a heat exchange pipeline of the condenser, nu being the number of heat transfer units of the condenser, and the calculation expression of the Nu being shown as a formula (2-2);
in the formula (2-2), k represents the heat exchange coefficient of the condenser, A represents the heat exchange area of the condenser, and C represents p Denotes the coefficient of thermal equivalent, G w And the flow rate of circulating water is shown, delta t is the temperature rise of the circulating water, and delta t is the end difference of the condenser. The exhaust steam temperature calculated according to the formula (1) is recorded as t s ', since the formula (1) is taken as τ = τ 1 As a result of integration for a constant value, the formula (2-3) can be obtained;
in the formula (2-3), t s ' represents the exhaust steam temperature, t, calculated according to equation (1) 1 Represents the temperature of the circulating water inlet, G w Represents the flow rate of circulating water, Q represents the heat load of the condenser, and τ 1 And (3) representing the ratio of the end difference of the condenser before the change of the cold end factor to the mean logarithmic temperature difference of the condenser, wherein Nu is the number of heat transfer units of the condenser.
Subtracting the formula (2-1) from the formula (2-3) gives the formula (2-4):
in the formula (2-4), t s ' represents the exhaust steam temperature, t, calculated according to equation (1) 1 Expressing the inlet water temperature of circulating water, delta t expressing the end difference of the condenser, LMTD expressing the logarithmic mean temperature difference of the condenser, and tau 1 And (3) representing the ratio of the condenser end difference to the average logarithmic temperature difference of the condenser before the cold end factor changes, wherein Nu is the number of heat transfer units of the condenser.
The point xi is necessarily present by the Lagrange median theorem, and the formula (2-5) is established;
in the formula (2-5), t s,2 Indicating the exhaust temperature, t, of the turbine after the cold end factor has changed 1,2 Showing the inlet water temperature of the circulating water after the cold end factor changes, delta t showing the end difference of the condenser, LMTD showing the logarithmic mean temperature difference of the condenser, and tau 1 Represents the ratio of the condenser end difference before the change of the cold end factor to the mean logarithmic temperature difference of the condenser, nu 1 And Nu 2 Respectively representing the number of heat transfer units of the condenser before and after the change of the cold end factor. Therefore, the error of the calculation results according to the formula (1) and the formula (1-9) is the formula (2-6);
t 'in formula (2-6)' s,2 Steam turbine discharge temperature, t, calculated according to equation (1) after cold end factor change s,2 Steam turbine exhaust temperature, t, calculated according to HEI standard after cold end factor change 1,2 Showing the inlet water temperature of the circulating water after the cold end factor changes, delta t showing the end difference of the condenser, LMTD showing the logarithmic mean temperature difference of the condenser, and tau 1 Represents the ratio of the condenser end difference to the mean logarithmic temperature difference of the condenser before the cold end factor changes, nu 1 And Nu 2 Respectively representing the number of heat transfer units of the condenser before and after the cold end factor changes.
The expression of the number Nu of the heat transfer units of the condenser is Nu = ln (delta t/delta t + 1), wherein delta t represents the temperature rise of circulating water, delta 0t represents the end difference of the condenser, and the number Nu of the heat transfer units of the condenser monotonically decreases along with delta t/[ delta ] t; τ = δ t/LMTD = (δ t/. DELTA.t) ln (1 +. DELTA.t/δ t), according to mathematical analysis, 0<τ&lt, 1, monotonically increasing with δ t/. DELTA.t. Therefore, if δ t 2 /△t 2 >δt 1 /△t 1 Then Nu 2 /Nu 1 &lt 1 is true, τ 1 <(δt/LMTD) ξ <τ 2 Can judge t' s,2 <t s,2 Of which is t' s，2 Steam turbine exhaust temperature, t, calculated according to equation (1) after cold end factor change s,2 Steam turbine exhaust temperature, tau, calculated according to HEI standard after cold end factor change 1 And τ 2 Respectively representing the ratio of the condenser end difference before and after the cold end factor change to the mean temperature difference of the condenser logarithm. Therefore, the steam turbine exhaust temperature t 'calculated according to the formula (1) after the cold end factor change is obtained' s,2 And the steam turbine exhaust temperature t calculated according to the HEI standard after the cold end factor changes s,2 The exhaust steam temperature error delta of the steam turbine is shown as a formula (2). If δ t 2 /△t 2 <δt 1 /△t 1 The same conclusions can be drawn through the same analysis.
The error analysis shows that the result calculated according to the formula (1) is slightly lower than the result calculated according to the formula (1-9), and the error range can be calculated according to the formula (2), so that the steam turbine exhaust temperature t after the cold end factor change is corrected according to the steam turbine exhaust temperature error delta s,2 The specific term "time" means the steam turbine exhaust temperature t after the cold end factor is changed s,2 And adding the steam turbine exhaust temperature error delta to obtain the range of the steam turbine exhaust temperature after the corrected cold end factor changes.
In this embodiment, the number Nu of heat transfer units of the condenser before the cold end factor changes 1 The calculation expression of (c) is shown as formula (3);
in the formula (3), k 1 Represents the heat exchange coefficient, A, of the condenser before the change of the cold end factor 1 Represents the heat exchange area of the condenser before the cold end factor changes, C p Is a thermal equivalent coefficient, G w,1 Showing the circulating water flow before the cold end factor changes.
In this embodiment, the number Nu of heat transfer units of the condenser after the cold end factor changes 2 The calculation expression of (a) is shown as formula (4);
in the formula (4), k 2 Indicating changes in cold end factorsHeat exchange coefficient of the condenser A 2 Represents the heat exchange area of the condenser after the cold end factor changes, C p Is a thermal equivalent coefficient, G w，2 Showing the circulating water flow after the cold end factor is changed.
It should be noted that, based on a preset water and steam property table or an enthalpy-entropy chart, the table is looked up according to the turbine exhaust temperature to obtain the turbine back pressure before the cold end factor changes, which is the existing method of the condensing turbine, so the specific process is not described herein again.
To sum up, the condensing steam turbine cold end energy-saving diagnosis method of the embodiment performs differential derivation according to the heat transfer principle and the condenser heat exchange coefficient calculation formula provided by the authority, obtains the calculation formula by the taylor formula simplification, and analyzes the error range according to the lagrangian median theorem.
Example two:
the present embodiment is basically the same as the first embodiment, and the main differences are as follows: calculating the steam turbine exhaust temperature t after the cold end factor changes s,2 The formulas (a) and (b) are different, in this embodiment, on the basis of the formula (1), the condenser characteristics are assumed to be unchanged, and the condenser cleanliness is assumed to be unchanged in a short time, if the circulating water inlet temperature and the condenser heat load are assumed to be unchanged, the formula (1) is simplified to obtain the formula (5), and the formula (5) is adopted to calculate the turbine exhaust steam temperature t after the cold end factor changes s,2 。
In the formula (5), the reaction mixture is,t s,1 and t s,2 Respectively representing the steam turbine exhaust temperature, t, before and after cold end factor change 1 Represents the temperature of the circulating water inlet, G w,1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor changes, and tau representing the ratio of the condenser end difference to the condenser logarithmic mean temperature difference before the cold end factor changes. The method comprises the steps of directly calculating tau according to actually measured exhaust steam temperature (or saturated temperature corresponding to exhaust steam pressure), circulating water inlet temperature and circulating water outlet temperature on site, substituting the formula with circulating water flow passing through a condenser before and after starting and stopping the standby circulating pump to obtain the exhaust steam temperature after starting and stopping the standby circulating pump, searching the corresponding exhaust steam pressure by an enthalpy-entropy diagram, obtaining the variation of unit generating capacity by a back pressure correction curve, and comparing the variation with the increment of power consumption of the circulating pump to determine a reasonable starting and stopping mode of the circulating pump.
Example three:
the present embodiment is basically the same as the first embodiment, and the main differences are as follows: the embodiment is to calculate the steam turbine exhaust temperature t after the cold end factor changes aiming at the transformation of the cooling tower s,2 The formulas (1) are different, in this embodiment, on the basis of the formula (1), the characteristics of the condenser are considered to be unchanged, and the cleanliness of the condenser is not changed in a short time, if the circulating water flow and the heat load of the condenser are assumed to be unchanged, the formula (1) is simplified to obtain a formula (6), and the formula (6) is adopted to calculate the exhaust steam temperature t of the steam turbine after the cold end factor is changed s,2 。
In the formula (6), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1，1 And t 1,2 Respectively representing the inlet water temperature, beta, of the circulating water before and after the cold end factor changes t,1 And beta t，2 Respectively representing the inlet water temperature correction coefficients of cooling water before and after the change of the cold end factor, and tau representing the difference between the condenser end and the mean temperature difference between the condenser logarithm and the cold end factor before the changeAnd (4) the ratio.
In addition to the first to third embodiments, the equation (1) can be used for an economic budget for condenser modification, an economic budget for deep sea water modification, an economic calculation of a heat load change of a condenser, and the like. It should be particularly noted that the measurement point error has a large influence on the calculation result of the formula (1), so that the exhaust steam pressure is measured by a high-precision absolute pressure transmitter according to ASME PTC6 steam turbine performance test procedure or ASME PTC12 steam condensation equipment performance test procedure; the temperature of the circulating water inlet and outlet is preferably measured by a high-precision platinum resistance thermometer and multiple measuring points.
Example four:
the present embodiment is basically the same as the first embodiment, and the main differences are as follows: the first embodiment is detection of a single working condition, while the first embodiment is detection of multiple working conditions, weighted average is carried out on the backpressure reduction amplitude of the steam turbine under all the working conditions, and the weighted average result is output as the cold end energy-saving diagnosis result of the condensing steam turbine, so that the problem of unbalanced backpressure reduction amplitude of the steam turbine under different working conditions is solved.
The implementation steps of the condensing steam turbine cold end energy-saving diagnosis method of the embodiment comprise:
s1) determining the steam turbine exhaust temperature t of the condensing steam turbine before the energy-saving related cold end factor changes s,1 Inlet temperature t of circulating water 1,1 And the temperature t of the circulating water outlet 2,1 (wherein the turbine exhaust temperature t s,1 The measurement can be directly carried out under the condition of ensuring the measurement accuracy, or the measurement can be carried out by measuring the backpressure of the turbine and searching based on a preset water and steam property table or an enthalpy-entropy diagram), the temperature rise delta t of circulating water of the condenser before the cold end factor change, the end difference delta t of the condenser and the logarithmic mean temperature difference LMTD of the condenser are calculated according to the data, and the ratio tau = delta t/LMTD of the end difference of the condenser and the logarithmic mean temperature difference of the condenser before the cold end factor change is calculated;
s2) determining cold end factors which are likely to change, wherein the cold end factors comprise the circulating water inlet temperature of the condenser, the heat load of the condenser, the circulating water flow, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser;
s3) determining parameters of each cold end factor before the cold end factor changes, including the inlet water temperature t of circulating water of the condenser 1，1 And heat load Q of condenser 1 Heat exchange area A of condenser 1 Circulating water flow G w,1 Sectional area S of single-pass heat exchange pipeline of condenser 1 Coefficient of outer diameter C of heat exchange pipeline 1,1 Correction coefficient beta of cooling water inlet temperature t,1 Tube and wall thickness correction factor beta m,1 Cleanliness coefficient beta of condenser c , 1 (ii) a Wherein, the heat exchange pipeline has an outer diameter coefficient C 1,1 And a correction coefficient beta of the inlet water temperature of the cooling water t,1 Pipe and wall thickness correction factor beta m,1 According to Standards for Steel Surface connectors, established by the American society for Heat transfer (HEI), C 1,1 Determined by the external diameter of the heat exchange pipeline of the condenser before the cold end factor changes, beta t,1 The correction coefficient beta of the pipe and the wall thickness is determined by the inlet water temperature of the circulating water before the cold end factor changes m,1 The method is determined by the material and the wall thickness of a heat exchange pipeline of the condenser before the cold end factor changes;
s4) determining various typical working conditions within a period of time (for example, one year), wherein at least one of the inflow water temperature of circulating water of the condenser, the heat load of the condenser, the flow rate of the circulating water, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the cross section area of a single-pass heat exchange pipeline of the condenser under each working condition is different from other working conditions, and selecting one working condition as the current working condition;
s5) determining parameters of the condensing steam turbine after the cold end factors related to energy saving change according to the current working condition, wherein the parameters after the cold end factors change comprise the inlet water temperature t of circulating water of the condenser 1,2 Thermal load Q of condenser 2 Coefficient of outer diameter C of heat exchange pipeline 1,2 Heat exchange area A of condenser 2 Correction coefficient beta of cooling water inlet temperature t,2 A pipe andwall thickness correction factor beta m,2 And the cleanliness coefficient beta of the condenser c,2 Circulating water flow G w,2 Sectional area S of single-flow heat exchange pipeline of condenser 2 (ii) a Calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) s,2 ；
In the formula (1), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1,1 And t 1,2 Respectively representing the inlet water temperature of the circulating water before and after the cold end factor changes, Q 1 And Q 2 Respectively representing the condenser heat load before and after the cold end factor change, C 1,1 And C 1,2 Respectively representing the external diameter coefficient, A, of the heat exchange pipeline before and after the cold end factor changes 1 And A 2 Respectively representing the heat exchange area, beta, of the condenser before and after the change of the cold end factor t,1 And beta t,2 Respectively representing the inlet water temperature correction coefficient, beta, of the cooling water before and after the cold end factor change m,1 And beta m,2 Respectively representing the correction coefficients of pipe material and wall thickness before and after cold end factor change, beta c,1 And beta c,2 Respectively representing the condenser cleanliness coefficients, G, before and after the cold end factor changes w,1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor change, S 1 And S 2 Respectively representing the cross sections of single-flow heat exchange pipelines of the condenser before and after the change of the cold end factor, wherein tau represents the ratio of the end difference of the condenser before the change of the cold end factor to the logarithmic mean temperature difference of the condenser;
s6) based on a preset water and steam property table or an enthalpy entropy chart, according to the steam turbine exhaust temperature t after the cold end factor changes s,2 Looking up a table to obtain the back pressure of the steam turbine after the cold end factor changes, and subtracting the back pressure of the steam turbine before the cold end factor changes from the back pressure of the steam turbine after the cold end factor changes to obtain the back pressure reduction amplitude of the steam turbine before and after the cold end factor changes under the current working condition;
and S7) carrying out weighted average on the backpressure reduction amplitude of the steam turbine under all working conditions, and outputting the result of the weighted average as the cold end energy-saving diagnosis result of the condensing steam turbine.
In this embodiment, in step S5), the turbine exhaust steam temperature t after the cold end factor change is calculated according to the formula (1) s,2 Meanwhile, the method also comprises the steps of calculating the steam turbine exhaust temperature error delta according to the expression shown in the formula (2), and correcting the steam turbine exhaust temperature t after the cold end factor change according to the steam turbine exhaust temperature error delta s,2 ；
In the formula (2), t s,2 Indicating the exhaust temperature, t, of the turbine before and after changes in the cold end factor 1,2 Shows the inlet water temperature Nu of the circulating water after the cold end factor changes 1 And Nu 2 Respectively representing the number of heat transfer units, tau, of the condenser before and after the change of the cold end factor 1 And τ 2 Respectively representing the ratio of the condenser end difference before and after the cold end factor change to the mean temperature difference of the condenser logarithm.
In this embodiment, the number Nu of heat transfer units of the condenser before the cold end factor changes 1 The calculation expression of (c) is shown as formula (3);
in the formula (3), k 1 Represents the heat exchange coefficient of the condenser before the cold end factor changes, A 1 Represents the heat exchange area of the condenser before the cold end factor changes, C p Is a thermal equivalent coefficient, G w,1 Showing the circulating water flow before the cold end factor changes.
In this embodiment, the number Nu of heat transfer units of the condenser after the cold end factor changes 2 The calculation expression of (a) is shown as formula (4);
in the formula (4), k 2 Represents the heat exchange coefficient, A, of the condenser after the cold end factor changes 2 Represents the heat exchange area of the condenser after the cold end factor changes, C p Is a thermal equivalent coefficient, G w,2 Indicating the circulating water flow after the cold end factor is changed.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims (6)

1. The cold end energy-saving diagnosis method of the condensing steam turbine is characterized by comprising the following implementation steps of:
1) Determining the turbine discharge temperature t of a condensing turbine before changes in energy-saving related cold end factors s,1 Inlet temperature t of circulating water 1,1 And the temperature t of the circulating water outlet 2,1 Calculating the temperature rise delta t of circulating water of the condenser, the end difference delta t of the condenser and the logarithmic mean temperature difference LMTD of the condenser before the cold end factor changes according to the data, and calculating the ratio tau = delta t/LMTD of the end difference of the condenser and the logarithmic mean temperature difference of the condenser before the cold end factor changes;
2) Determining cold end factors which are likely to change, wherein the cold end factors comprise the circulating water inlet temperature of a condenser, the heat load of the condenser, the circulating water flow, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser;
3) Determining parameters of cold end factors before cold end factor change, including condenser circulating water inlet water temperature t 1,1 Thermal load Q of condenser 1 Heat exchange area A of condenser 1 Circulating water flow G w,1 Sectional area S of single-flow heat exchange pipeline of condenser 1 Outer diameter of heat exchange pipelineCoefficient C 1,1 Correction coefficient beta of cooling water inlet temperature t,1 Tube and wall thickness correction factor beta m,1 Cleanliness coefficient beta of condenser c,1 ；
4) Determining parameters of each cold end factor after the cold end factor changes, including the inlet water temperature t of the circulating water of the condenser 1,2 Thermal load Q of condenser 2 Heat exchange area A of condenser 2 And a correction coefficient beta of the inlet water temperature of the cooling water t,2 Circulating water flow G w,2 Sectional area S of single-flow heat exchange pipeline of condenser 2 Coefficient of outer diameter C of heat exchange pipeline 1,2 Tube and wall thickness correction factor beta m,2 Cleanliness coefficient beta of condenser c,2 ；
5) Calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) s,2 ；
In the formula (1), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1,1 And t 1,2 Respectively representing the circulating water inlet temperature before and after the cold end factor changes, Q 1 And Q 2 Respectively representing the condenser heat load before and after the cold end factor change, C 1,1 And C 1,2 Respectively representing the external diameter coefficient, A, of the heat exchange pipeline before and after the cold end factor changes 1 And A 2 Respectively representing the heat exchange area, beta, of the condenser before and after the change of the cold end factor t,1 And beta t,2 Respectively representing the inlet water temperature correction coefficient, beta, of the cooling water before and after the cold end factor change m,1 And beta m,2 Respectively representing the correction coefficients of pipe material and wall thickness before and after cold end factor change, beta c,1 And beta c,2 Respectively representing the condenser cleanliness coefficients, G, before and after the cold end factor changes w,1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor change, S 1 And S 2 Respectively representing the cross sections of the single-flow heat exchange pipeline of the condenser before and after the change of the cold end factor, and representing the difference of the condenser ends and the condensed steam before the change of the cold end factorRatio of log mean temperature difference;
6) Based on a preset water and steam property table or an enthalpy-entropy diagram, according to the steam turbine exhaust temperature t after the cold end factor changes s,2 Looking up a table to obtain the back pressure of the steam turbine after the cold end factor changes, subtracting the back pressure of the steam turbine before the cold end factor changes from the back pressure of the steam turbine after the cold end factor changes to obtain the back pressure reduction amplitude of the steam turbine before and after the cold end factor changes, and outputting the back pressure reduction amplitude of the steam turbine as a cold end energy-saving diagnosis result of the condensing steam turbine;
calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) in the step 5) s,2 Meanwhile, the method also comprises the steps of calculating the steam turbine exhaust temperature error delta according to the expression shown in the formula (2), and correcting the steam turbine exhaust temperature t after the cold end factor change according to the steam turbine exhaust temperature error delta s,2 ；
In the formula (2), t s,2 Indicating the exhaust temperature, t, of the turbine after the cold end factor has changed 1,2 Shows the inlet water temperature Nu of the circulating water after the cold end factor changes 1 And Nu 2 Respectively representing the number of heat transfer units, tau, of the condenser before and after the change of the cold end factor 1 And τ 2 Respectively representing the ratio of the condenser end difference before and after the cold end factor change to the mean temperature difference of the condenser logarithm.
2. The condensing steam turbine cold-end energy-saving diagnosis method according to claim 1, wherein the number Nu of heat transfer units of the condenser before the cold-end factor changes 1 The calculation expression of (c) is shown as formula (3);
in the formula (3), k 1 Represents the heat exchange coefficient of the condenser before the cold end factor changes, A 1 Condenser heat exchange surface before showing cold end factor changeProduct of qi and blood C p Is a thermal equivalent coefficient, G w，1 Showing the circulating water flow before the cold end factor changes.
3. The condensing steam turbine cold-end energy-saving diagnosis method according to claim 1, wherein the number Nu of heat transfer units of the condenser after the cold-end factor is changed 2 The calculation expression of (a) is shown as formula (4);
in the formula (4), k 2 Represents the heat exchange coefficient of the condenser after the cold end factor changes, A 2 Represents the heat exchange area of the condenser after the cold end factor changes, C p Is a thermal equivalent coefficient, G w，2 Indicating the circulating water flow after the cold end factor is changed.
4. The energy-saving diagnosis method for the cold end of the condensing steam turbine is characterized by comprising the following implementation steps of:
s1) determining the steam turbine exhaust temperature t of the condensing steam turbine before the energy-saving related cold end factor changes s，1 Inlet temperature t of circulating water 1,1 And the temperature t of the circulating water outlet 2,1 Calculating the temperature rise delta t of circulating water of the condenser, the end difference delta t of the condenser and the logarithmic mean temperature difference LMTD of the condenser before the cold end factor changes according to the data, and calculating the ratio tau = delta t/LMTD of the end difference of the condenser and the logarithmic mean temperature difference of the condenser before the cold end factor changes;
s2) determining cold end factors which are likely to change, wherein the cold end factors comprise the circulating water inlet temperature of the condenser, the heat load of the condenser, the circulating water flow, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser;
s3) determining parameters of each cold end factor before the cold end factor changes, including the inlet water temperature t of circulating water of the condenser 1，1 Thermal load Q of condenser 1 Heat exchange area A of condenser 1 Circulating water flow G w,1 Sectional area S of single-flow heat exchange pipeline of condenser 1 Coefficient of outer diameter C of heat exchange pipeline 1,1 Correction coefficient beta of cooling water inlet temperature t，1 Tube and wall thickness correction factor beta m，1 Cleanliness coefficient beta of condenser c，1 ；
S4) determining various typical working conditions in a period of time, wherein at least one of the inflow water temperature of circulating water of the condenser, the heat load of the condenser, the circulating water flow rate, the outer diameter of a heat exchange pipeline of the condenser, the heat exchange area of the condenser, the material of the heat exchange pipeline of the condenser, the wall thickness of the heat exchange pipeline of the condenser, the cleanliness of the condenser and the sectional area of the single-pass heat exchange pipeline of the condenser under each working condition is different from other working conditions, and selecting one working condition as the current working condition;
s5) determining parameters of the condensing steam turbine after the cold end factors related to energy saving change according to the current working condition, wherein the parameters after the cold end factors change comprise the inlet water temperature t of circulating water of the condenser 1，2 Thermal load Q of condenser 2 Coefficient of outer diameter C of heat exchange pipeline 1，2 Heat exchange area A of condenser 2 Correction coefficient beta of cooling water inlet temperature t,2 Tube and wall thickness correction factor beta m,2 Cleanliness coefficient beta of condenser c，2 Circulating water flow G w,2 Sectional area S of single-flow heat exchange pipeline of condenser 2 (ii) a Calculating the steam turbine exhaust temperature t after the cold end factor changes according to the formula (1) s，2 ；
In the formula (1), t s,1 And t s,2 Respectively representing the exhaust temperature, t, of the turbine before and after the cold end factor changes 1,1 And t 1,2 Respectively representing the inlet water temperature of the circulating water before and after the cold end factor changes, Q 1 And Q 2 Respectively representing the condenser heat load before and after the cold end factor change, C 1,1 And C 1,2 Respectively representing the external diameter coefficient, A, of the heat exchange pipeline before and after the cold end factor changes 1 And A 2 Respectively representing cold end factor changesHeat exchange area, beta, of front and rear condensers t，1 And beta t，2 Respectively representing the inlet water temperature correction coefficient, beta, of the cooling water before and after the cold end factor change m，1 And beta m，2 Respectively representing the correction coefficients of pipe material and wall thickness before and after cold end factor change, beta c，1 And beta c，2 Respectively representing the condenser cleanliness coefficients, G, before and after the cold end factor changes w，1 And G w,2 Respectively representing the circulating water flow before and after the cold end factor change, S 1 And S 2 Respectively representing the cross sections of single-flow heat exchange pipelines of the condenser before and after the change of the cold end factor, wherein tau represents the ratio of the end difference of the condenser before the change of the cold end factor to the logarithmic mean temperature difference of the condenser;
s6) based on a preset water and steam property table or an enthalpy-entropy chart, according to the steam turbine exhaust temperature t after the cold end factor changes s,2 Looking up a table to obtain the back pressure of the steam turbine after the cold end factor changes, and subtracting the back pressure of the steam turbine before the cold end factor changes from the back pressure of the steam turbine after the cold end factor changes to obtain the back pressure reduction amplitude of the steam turbine before and after the cold end factor changes under the current working condition;
s7) carrying out weighted average on the backpressure reduction amplitude of the steam turbine under all working conditions, and outputting the result of the weighted average as the cold end energy-saving diagnosis result of the condensing steam turbine;
in the step S5), the steam turbine exhaust temperature t after the cold end factor changes is calculated according to the formula (1) s,2 Meanwhile, the method also comprises the steps of calculating the steam turbine exhaust temperature error delta according to the expression shown in the formula (2), and correcting the steam turbine exhaust temperature t after the cold end factor change according to the steam turbine exhaust temperature error delta s,2 ；
In the formula (2), t s,2 Is the exhaust temperature t of the steam turbine after the cold end factor changes 1,2 Is the inlet water temperature of the circulating water after the cold end factor changes, nu 1 And Nu 2 Respectively representing the number of heat transfer units, tau, of the condenser before and after the change of the cold end factor 1 And τ 2 Respectively showing cold end causeThe ratio of the condenser end difference before and after element change to the mean temperature difference of the condenser logarithm.
5. The condensing steam turbine cold-end energy-saving diagnosis method according to claim 4, wherein the number Nu of heat transfer units of the condenser before the cold-end factor changes 1 The calculation expression of (c) is shown as formula (3);
in formula (3), k 1 Represents the heat exchange coefficient of the condenser before the cold end factor changes, A 1 Represents the heat exchange area of the condenser before the cold end factor changes, C p Is a thermal equivalent coefficient, G w,1 Showing the circulating water flow before the cold end factor changes.
6. The condensing steam turbine cold-end energy-saving diagnosis method according to claim 4, wherein the number Nu of heat transfer units of the condenser after the cold-end factor changes 2 The calculation expression of (a) is shown as formula (4);
in the formula (4), k 2 Represents the heat exchange coefficient, A, of the condenser after the cold end factor changes 2 Represents the heat exchange area of the condenser after the cold end factor changes, C p Is a thermal equivalent coefficient, G w,2 Showing the circulating water flow after the cold end factor is changed.
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