CN111737859A - Improved steam turbine set variable-pressure operation consumption difference quantitative calculation model construction method - Google Patents
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Abstract
A method for constructing a consumption difference quantitative calculation model for variable-pressure operation of an improved steam turbine set takes the circulation heat absorption capacity, the effective enthalpy drop of a high-pressure cylinder and the enthalpy rise of a water feed pump of 1kg of unit steam as main characteristic variables and adopts an enthalpy drop correction coefficient
And thermodynamic system correction factor
The 'effective enthalpy drop of a high-pressure cylinder' and 'enthalpy rise of a feed pump' are respectively corrected, and a turbine set variable-pressure operation consumption difference quantitative calculation model based on 'relative comparison of unit heat consumption rates' is constructed. The model has simple structure, only needs to collect a small amount of easily and accurately measured temperature and pressure parameters in the constant-power variable-pressure operation of the steam turbine set, and does not need to collectFlow parameters that are relatively difficult to accurately measure; current enthalpy drop correction coefficient
And thermodynamic system correction factor
When the segmental correction is adopted, the unit heat rate recurrence deviation of the model is less than or equal to 1kJ/(kW.h), and the variation of the unit heat rate when the inlet steam pressure variation is greater than or equal to 0.1MPa under the constant power of the steam turbine unit can be accurately identified.
Description
Technical Field
The invention relates to a construction method of an improved steam turbine set variable-pressure operation consumption difference quantitative calculation model, and belongs to the technical field of steam turbine sets.
Background
When the steam turbine set operates at a constant power, the numerical correspondence between the steam admission pressure and the heat rate of the steam turbine set under the conditions of a given steam distribution mode and a valve opening sequence can be called as the thermal economic characteristic of the constant-power variable-pressure operation of the steam turbine set. Under an AGC power grid dispatching mode taking the 'unit generating power' as a tracking target, the thermal economic characteristics of variable-pressure operation of the steam turbine unit are researched, the continuous variation trend of the heat consumption rate of the steam turbine unit under different initial pressures in a feasible valve position interval under constant power is disclosed, and the inherent law of constant-power variable-pressure operation of different types of steam turbine units is shown.
Generally, the inlet steam pressure of a steam turbine changes by 0.1MPa, and the heat consumption rate of a unit changes by about 2 kJ/(kW.h).
The uncertainty of the high-accuracy test of the large condensing steam turbine given by ASME PTC6-2004 steam turbine Performance test Specification of American society of mechanical Engineers is 0.3% respectively (it is stated that ASME PTC6 requires the same test conditions and is repeatedly tested twice, if the test results of the two times are less than or equal to 0.3% each other, the result is considered to be an acceptable result, otherwise, the uncertainty is repeatedly tested for the third time). The heat consumption rate of the steam turbine set which is put into production is approximately 7000-8000 kJ/(kW.h), and even if the performance test is completed according to the severest ASME performance test regulation, the uncertainty of the test result is approximately 21.0-24.0 kJ/(kW.h). Obviously, according to ASME PTC6, the test cannot accurately distinguish the influence degree of small-amplitude steam inlet pressure change on the unit economy (such as 0.2MPa, the adjustment precision which can be achieved by the current coordinated control system).
The conventional turboset fixed-slip pressure test (also called a turboset optimal initial pressure optimization test or a turboset operation mode optimization adjustment test) is usually carried out according to the ASME PTC6 specification, however, degradation often exists in the aspects of test instruments, test conditions and the like, generally, one working condition is only arranged for single test instead of parallel working condition repeated test, and the concept of uncertainty cannot be naturally referred to. Therefore, objectively, it is difficult (or even impossible) to identify the heat loss difference of different steam admission pressures by the conventional constant-slip pressure test method.
Based on the valve point effect of the steam turbine unit, the optimization of the steam inlet pressure is carried out in a targeted manner by part of test units; however, if the overlap degree of the adjusting valve is set to be larger, the 'valve point' will be sharp and no matter what the overlap degree is. Taking the pressure overlap as an example, it is generally considered that when the front valve is opened to a pressure ratio of 0.85 to 0.90, the rear valve is opened properly, that is, the pressure overlap ξ p is between 0.10 and 0.15. Assuming that the pressure overlap is 10%, the throttling loss at the two valve points and the three valve points will reach 30-80 kJ/(kW.h), which almost exhausts the optimization potential of the constant-slip pressure test!
Some test units also propose to adopt a local energy consumption analysis method to compare the heat consumption rate of the unit under different test working conditions; however, the local consumption difference analysis method usually considers the influence of the change of a single characteristic parameter on the heat consumption rate of the unit in an isolated manner, and neglects the mutual coupling among the parameters; the theoretical basis of the method is not sufficient, and the analysis result has great deviation from the actual result.
In conclusion, the existing test methods are limited by precision, and it is difficult to accurately distinguish the thermal economic characteristics of the fixed-power variable-pressure operation of the steam turbine set.
According to the principle of the steam turbine, from the aspect of energy balance, in the process of constant-power variable-pressure operation of the steam turbine set, if the work capacity gain of a high-pressure cylinder (namely, the work capacity gain of main steam), the work capacity gain of a medium/low-pressure cylinder (namely, the work capacity gain of reheat steam) and the heat absorption gain of a cycle of 1kg of steam can be measured, the relative change of the heat economy of the set can be determined. As described above, no matter how to solve the work amount of the main steam in the high pressure cylinder or the work amount of the reheat steam in the medium/low pressure cylinder or the heat absorption amount of the cycle, hundreds of steam-water parameters including flow rate need to be measured, which not only is complicated to be tested, but also is difficult to ensure the measurement accuracy.
The professor Yinian of great Cai of Xian in the book of steam turbine (the university of Xian traffic, 1986) describes a method for quantitatively analyzing the difference of heat efficiency between different steam distribution modes and operation modes based on 'effective enthalpy drop of a high-pressure cylinder' and 'circulating heat absorption capacity'; the method has clear theoretical mechanism and simple implementation process. CN102998122B discloses a multi-factor-based overall optimization method for optimal initial pressure of a steam turbine set, which introduces a third main variable of 'water supply enthalpy rise' on the basis of two main variables of 'effective enthalpy drop of a high pressure cylinder' and 'circulating heat absorption' according to a steam turbine principle method, provides a fixed quantity model of variable pressure operation consumption difference of the steam turbine set, and applies the fixed quantity model to analysis and comparison of thermal and economic characteristics of constant power variable pressure operation of the same steam turbine set. The model is specifically as follows:
is provided with h0、h1Delta h, delta tau, H, Q, η and HR are respectively main steam enthalpy, high-pressure cylinder exhaust enthalpy, high-pressure cylinder effective enthalpy drop, water supply enthalpy rise, unit steam useful work, circulation heat absorption capacity, circulation efficiency and unit heat consumption rate h 'before variable working condition'0、h′1Delta H ', delta tau', H ', Q', η 'and HR' are respectively the main steam enthalpy, high-pressure cylinder exhaust enthalpy, high-pressure cylinder effective enthalpy drop, water supply enthalpy rise, unit steam useful work, circulation heat absorption capacity, circulation efficiency and unit heat consumption rate after changing working condition, delta H), (delta tau), (delta Q) are respectively the high-pressure cylinder effective enthalpy drop gain, water supply enthalpy rise gain and circulation heat absorption capacity gain before and after changing working condition, α is reheat coefficient, and delta η is the reheating coefficient before changing working conditionVariation in post cycle efficiency.
Before the variable working condition:
for the variable working condition:
after the working condition is changed, the gain of the effective enthalpy drop of the high-pressure cylinder is increased relative to that before the working condition:
(Δh)＝(h′0-h′1)-(h0-h1)＝Δh0-Δh1(5)
after the working condition is changed, the cyclic heat absorption gain is relative to that before the working condition:
(Δq)＝(h′0-h0)-α·(h′1-h1)＝Δh0-α·Δh1(6)
relative to the enthalpy gain of water supply before the working condition after the working condition is changed:
(Δτ)＝Δτ′-Δτ (7)
although the theoretical mechanism of the model is clear, in formula (2), the "high-pressure cylinder effective enthalpy drop gain (Δ h)" and the "feedwater enthalpy rise gain (Δ τ)" directly replace the high-pressure cylinder work capacity gain (main steam work capacity gain) and the medium/low-pressure cylinder work capacity gain (reheat steam work capacity gain) of 1kg of steam, that is, the coefficients of the "high-pressure cylinder effective enthalpy drop gain (Δ h)" and the "feedwater enthalpy rise gain (Δ τ)" are both set to "1", in the multi-factor based global optimum initial pressure optimization method for the steam turbine set disclosed in CN 102998122B. The attached figures 1 and 2 show the reappearance effect of the variable-pressure operation consumption difference quantitative calculation model of the original turboset on the variable-pressure operation thermal economic characteristics of a supercritical N600 type nozzle steam distributor type A and a supercritical N600 type overload steam compensator type B under 480MW load. In the figure, the coefficients of the 'effective enthalpy drop gain (delta h)' and the 'feedwater enthalpy rise gain (delta tau)' are both taken as '1', and the numerical mechanism is insufficient; although the trends of the model heat consumption rate and the simulation heat consumption rate are similar, certain deviation exists, and the effect is not ideal.
Obviously, the numerical mechanisms of the ' effective enthalpy drop gain (delta h) of the high-pressure cylinder and the ' enthalpy rise gain (delta tau ') of the feed water are clarified, and the improvement of the original consumption difference model is facilitated. Fig. 3 and 4 show the main steam work gain, reheat steam work gain, high pressure cylinder effective enthalpy drop gain and the change trend of the steam pump enthalpy rise gain along with the steam inlet pressure of the supercritical N600 type nozzle steam distributor type A and the supercritical N600 type overload steam supplementing type B under 480MW load. The graph shows that two curves of the effective enthalpy drop gain of the high-pressure cylinder and the work gain of the main steam are in the same-direction relation, and the similarity is higher; the enthalpy gain of the steam pump and the work gain of the reheated steam are in an inverse relationship and have certain similarity. The same trend of the effective enthalpy drop gain and the main steam work gain of the high-pressure cylinder and the enthalpy rise gain and the reheat steam work gain of the steam pump is a general rule of various types of steam turbine units through a great deal of simulation research. Meanwhile, compared with the work load of solving 1kg of steam, the effective enthalpy drop of the high-pressure cylinder or the enthalpy rise of the steam pump of 1kg of steam can be solved, only a few parameters such as the pressure and the temperature parameter of the inlet and the outlet of the high-pressure cylinder or the pressure and the temperature parameter of the inlet and the outlet of the feed water pump are needed to be known, and the test precision is also ensured. Therefore, numerically representing the main steam work capacity gain and the reheat steam work capacity gain which are difficult to measure by the high-pressure cylinder effective enthalpy drop gain (delta h) and the feedwater enthalpy rise gain (delta tau) which are easy to measure is a numerical mechanism of a steam turbine set variable-pressure operation consumption difference quantitative calculation model.
Disclosure of Invention
The invention aims to provide an improved method for constructing a variable-pressure operation consumption difference quantitative calculation model of a steam turbine unit, aiming at the defect that the existing test method is difficult to accurately distinguish the thermal economic characteristics of the fixed-power variable-pressure operation of the steam turbine unit.
The technical scheme of the invention is that the method for constructing the variable-pressure operation consumption difference quantitative calculation model of the improved steam turbine set comprises the following steps of taking the circulation heat absorption capacity, the high-pressure cylinder effective enthalpy drop and the water-feeding pump enthalpy rise of 1kg of unit steam as characteristic variables according to the correlation analysis of the internal mechanism and the characteristic variables of the variable-pressure operation heat economic characteristics, and respectively correcting the high-pressure cylinder effective enthalpy drop and the water-feeding pump enthalpy rise by adopting an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma to obtain the variable-pressure operation consumption difference quantitative calculation model of the steam turbine set based on the unit heat rate relative comparison:
Q＝(h0-hf)-α(hr-h1)；
H＝ηQ
(Δh)＝Δh′-Δh＝(h′0-h′1)-(h0-h1)
(Δτ)＝Δτ′-Δτ
H′＝H+β(Δh)-γ(Δτ)
Q′＝(h′0-h′f)-α(h′r-h′1)
ΔHR＝HR′-HR
in the formula, h0The main steam enthalpy before the variable working condition, h1The enthalpy of the exhausted steam of the high pressure cylinder before the variable working condition, the effective enthalpy drop of the high pressure cylinder before the variable working condition, the enthalpy rise of the feed water before the variable working condition, the unit useful work of the steam before the variable working condition, the circulation heat absorption capacity before the variable working condition, the HfThe final water supply enthalpy h before variable working conditionsrThe enthalpy of reheat steam before variable working condition, η the cycle efficiency before variable working condition and HR the unit before variable working conditionHeat rate; h'0Is main steam enthalpy and h 'after variable working conditions'1The enthalpy of the exhaust steam of the high-pressure cylinder after the variable working condition, the effective enthalpy drop of the high-pressure cylinder after the variable working condition, the enthalpy rise of the feed water after the variable working condition, the unit useful work of the steam, the Q ' of the circulating heat absorption amount and H ' after the variable working condition 'fIs the final feedwater enthalpy, h 'after the variable working condition'rThe enthalpy of reheat steam after the variable working condition, η ', the cycle efficiency after the variable working condition and HR', the heat rate of the unit after the variable working condition, (delta h) the effective enthalpy drop gain of the high-pressure cylinder before and after the variable working condition, (delta tau) the enthalpy rise gain of feed water before and after the variable working condition, α a reheat coefficient, β an enthalpy drop correction coefficient, gamma a thermodynamic system correction coefficient and delta HR the amplitude of the heat rate of the unit before and after the variable working condition.
The enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma can be corrected and calculated by adopting special simulation software of a steam turbine set or an EXCEL self-programming thermodynamic calculation program conforming to ASME PTC6A-1982 calculation examples according to unit design parameters or test parameters.
For the steam turbine set adopting a 'multi-step sequence' opening mode, a valve point is taken as a boundary point, and segmented correction accounting is carried out on an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma so as to reduce the set heat consumption rate recurrence deviation of a model. The nozzle steam distributor type A can be divided into three sections of four-valve-three-valve, three-valve-two-valve and two-valve throttling according to valve points in sequence; the overload steam compensating machine B can be divided into two sections of 'full open of a steam compensating valve, full close of the steam compensating valve, full open of a main regulating valve' and 'throttling of the main regulating valve' according to valve points.
The working principle of the invention is that the same trend of 'effective enthalpy drop gain and main steam work gain of a high-pressure cylinder' and 'enthalpy rise gain and reheat steam work gain' is a common rule of various types of steam turbine units through a great deal of simulation research. The invention provides a method for numerically representing the main steam work capacity gain and the reheat steam work capacity gain which are difficult to measure by using the high-pressure cylinder effective enthalpy drop gain (delta h) and the feedwater enthalpy rise gain (delta tau) which are easy to measure, and further solving the relative change of the heat economy of a unit.
The invention has the advantages that the improved steam turbine set variable-pressure operation consumption difference quantitative calculation model has a simplified structure, only needs to acquire a small amount of easily and accurately measured temperature and pressure parameters in the fixed-power variable-pressure operation of the steam turbine set, and does not need to acquire flow parameters which are relatively difficult to accurately measure; when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma adopt segmented correction, the unit heat consumption rate recurrence deviation of the model is less than or equal to 1kJ/(kW.h), and the variation of the unit heat consumption rate when the inlet steam pressure variation is more than or equal to 0.1MPa under the constant power of the steam turbine unit can be accurately identified; through a large number of simulation verifications, the model can reproduce the constant-power variable-pressure operation thermal economic characteristics of the steam turbine set with different capacity grades, different parameter grades, different steam distribution modes and different thermodynamic system structures at high precision; and the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma have excellent inheritance for the thermal economic characteristics of the fixed-power variable-pressure operation of the steam turbine set, and can be corrected and calculated by adopting special simulation software of the steam turbine set or an EXCEL self-programming thermodynamic calculation program conforming to ASME PTC6A-1982 calculation according to the design parameters or test parameters of the steam turbine set and directly transplanted into a field test. In practical application, the model can be combined with a steam turbine set constant-power global variable-pressure dynamic test, and can also be combined with a steam turbine set constant-slip pressure optimizing steady-state test following ASME PTC6-2004 steam turbine performance test regulations, and the solving precision of the heat consumption rate of the field test unit can be obviously improved.
Drawings
Fig. 1 shows the recurrence effect of the variable-pressure operation consumption difference quantitative calculation model of the steam turbine set before improvement on the variable-pressure operation thermal economic characteristics of the nozzle steam distributor type a under 480MW load (the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma both take the value of "1");
fig. 2 shows the recurrence effect of the variable-pressure operation consumption difference quantitative calculation model of the steam turbine set before improvement on the variable-pressure operation thermal economic characteristics of the nozzle steam distributor type a under the 480MW load (the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma both take the value of "1");
FIG. 3 shows the variation trend of main steam work gain, reheat steam work gain, high pressure cylinder effective enthalpy drop gain and steam pump enthalpy rise gain with inlet steam pressure of a nozzle steam distributor type A under 480MW load;
FIG. 4 shows the variation trend of main steam work gain, reheat steam work gain, high pressure cylinder effective enthalpy drop gain and steam pump enthalpy rise gain with inlet steam pressure of the overload steam supplement type B under 480MW load;
FIG. 5 is a diagram showing the recurring effect of the variable-pressure operation differential consumption quantitative calculation model of the improved steam turbine set on the variable-pressure operation thermal-economic characteristics of the nozzle steam distributor type A under the 480MW load when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma do not adopt the sectional correction;
FIG. 6 is a diagram showing the recurring effect of the variable-pressure operation energy consumption difference quantitative calculation model of the improved steam turbine set on the variable-pressure operation thermal economic characteristics of the nozzle steam distributor type A under the 480MW load when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma adopt the sectional correction;
fig. 7 shows the reappearance effect of the variable-pressure operation energy consumption difference quantitative calculation model of the improved steam turbine set on the variable-pressure operation thermal economic characteristic of the overload steam turbine type B under the 480MW load when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma do not adopt the sectional correction;
fig. 8 shows the reappearance effect of the variable-pressure operation energy consumption difference quantitative calculation model of the improved steam turbine set on the variable-pressure operation thermal economic characteristic of the overload steam turbine type B under the 480MW load when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma adopt the sectional correction.
Detailed Description
The detailed description of the invention is shown in the drawings. The technical solution in the embodiment of the present invention will be clearly and completely described below with reference to fig. 5 to 8 in the embodiment of the present invention.
The units of the embodiment are respectively a supercritical N600 type nozzle steam distributor type A and a supercritical N600 type overload steam compensator type B. Wherein, the model A is a four-valve nozzle steam distribution unit (the valve opening sequence is GV1/2 synchronous → GV3 → GV4), the model B is an overload steam-supplementing throttling steam distribution unit (the valve opening sequence is main regulating valve → steam-supplementing valve), and the rated parameters of the two types of the steam distribution units are 660MW/24.2MPa/566 ℃/566 ℃. Fig. 5-8 show the reappearance effect of the improved steam turbine set variable-pressure operation consumption difference quantitative calculation model on the thermal economic characteristics of variable-pressure operation of the model A and the model B under the load of 480 MW.
The improved steam turbine set variable-pressure operation consumption difference quantitative calculation model comprises the following steps:
step 1: the invention discloses an improved steam turbine set variable-pressure operation consumption difference quantitative calculation model, which is constructed by taking the 'circulation heat absorption capacity', 'high-pressure cylinder effective enthalpy drop' and 'water-feeding pump enthalpy rise' of 1kg unit steam as main characteristic variables according to the correlation analysis of an internal mechanism and the characteristic variables of variable-pressure operation heat economic characteristics, and respectively correcting the 'high-pressure cylinder effective enthalpy drop' and the 'water-feeding pump enthalpy rise' by adopting an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma.
Is provided with h0、h1、Δh、Δτ、H、Q、hf、hrη, HR are respectively the main steam enthalpy, high-pressure cylinder exhaust enthalpy, high-pressure cylinder effective enthalpy drop, water supply enthalpy rise, unit steam useful work, circulation heat absorption capacity, final water supply enthalpy, reheat steam enthalpy, circulation efficiency and unit heat consumption rate before variable working condition h'0、h′1、Δh′、Δτ′、H′、Q′、h′f、h′rη 'and HR' are respectively the main steam enthalpy, the high-pressure cylinder exhaust enthalpy, the high-pressure cylinder effective enthalpy drop, the water supply enthalpy rise, the unit steam useful work, the circulation heat absorption capacity, the final water supply enthalpy, the reheat steam enthalpy, the circulation efficiency and the unit heat consumption rate after the variable working condition, (delta h) and (delta tau) are respectively the high-pressure cylinder effective enthalpy drop gain and the water supply enthalpy rise gain before and after the variable working condition, α, β and gamma are respectively the reheat coefficient, the enthalpy drop correction coefficient and the thermodynamic system correction coefficient, and delta HR is the amplitude of the heat consumption rate of the unit before and after the variable working condition.
Q＝(h0-hf)-α·(hr-h1) (2)
H＝η·Q (3)
(Δh)＝Δh′-Δh＝(h′0-h′1)-(h0-h1) (4)
(Δτ)＝Δτ′-Δτ (5)
H′＝H+β·(Δh)-γ·(Δτ) (6)
Q′＝(h′0-h′f)-α·(h′r-h′1) (7)
ΔHR＝HR′-HR (10)
Step 2: completing the simulation calculation of constant-power variable-voltage operation of case units (type A and type B); and extracting part of characteristic parameters in the simulation working condition, substituting the extracted characteristic parameters into the improved steam turbine set variable-pressure operation consumption difference quantitative calculation model, and correcting and calculating an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma. The simulation calculation is carried out according to unit design parameters or test parameters, and can adopt special simulation software of the steam turbine unit or an EXCEL self-programming thermodynamic calculation program conforming to ASME PTC 6A-1982. For the steam turbine set adopting a 'multi-step sequence' opening mode, a valve point is taken as a boundary point, and segmented correction accounting is carried out on an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma so as to reduce the set heat consumption rate recurrence deviation of a model. The nozzle steam distributor type A can be divided into three sections of four-valve-three-valve, three-valve-two-valve and two-valve throttling according to valve points in sequence; the overload steam compensating machine B can be divided into two sections of 'full open of a steam compensating valve, full close of the steam compensating valve, full open of a main regulating valve' and 'throttling of the main regulating valve' according to valve points.
When the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma do not adopt the sectional correction, the reproduction effect of the model is shown in fig. 5 and 7; when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma adopt segmented correction, the reproduction effect of the model is shown in fig. 6 and 8; through observation, when the enthalpy drop correction coefficient beta and the thermodynamic system correction coefficient gamma adopt segmented correction, the unit heat consumption rate recurrence deviation of the model is less than or equal to 1 kJ/(kW.h).
The above detailed description is provided for the consumption difference quantitative calculation model for the variable-pressure operation of the improved steam turbine set, and the present embodiment applies a specific example to illustrate the principle and the implementation manner of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (3)
1. The method is characterized in that the method takes the circulation heat absorption capacity, the high-pressure cylinder effective enthalpy drop and the water feeding pump enthalpy rise of 1kg of unit steam as characteristic variables, and corrects the high-pressure cylinder effective enthalpy drop and the water feeding pump enthalpy rise respectively by adopting an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma to obtain the steam turbine set variable-pressure operation consumption difference quantitative calculation model based on the unit heat consumption rate relative comparison:
Q＝(h0-hf)-α(hr-h1)；
H＝ηQ
(Δh)＝Δh′-Δh＝(h′0-h′1)-(h0-h1)
(Δτ)＝Δτ′-Δτ
H′＝H+β(Δh)-γ(Δτ)
Q′＝(h′0-h′f)-α(h′r-h′1)
ΔHR＝HR′-HR
in the formula, h0The main steam enthalpy before the variable working condition, h1The enthalpy of the exhausted steam of the high pressure cylinder before the variable working condition, the effective enthalpy drop of the high pressure cylinder before the variable working condition, the enthalpy rise of the feed water before the variable working condition, the unit useful work of the steam before the variable working condition, the circulation heat absorption capacity before the variable working condition, the HfThe final water supply enthalpy h before variable working conditionsrThe enthalpy of reheat steam before variable working condition, η, HR, the heat rate of the unit before variable working condition, and h'0Is main steam enthalpy and h 'after variable working conditions'1The enthalpy of the exhaust steam of the high-pressure cylinder after the variable working condition, the effective enthalpy drop of the high-pressure cylinder after the variable working condition, the enthalpy rise of the feed water after the variable working condition, the unit useful work of the steam, the Q ' of the circulating heat absorption amount and H ' after the variable working condition 'fIs the final feedwater enthalpy, h 'after the variable working condition'rThe method comprises the steps of (1) reheating steam enthalpy after variable working conditions, η 'circulation efficiency after variable working conditions, HR' unit heat rate after variable working conditions, (delta h) high-pressure cylinder effective enthalpy drop gain before and after variable working conditions, (delta tau) feedwater enthalpy rise gain before and after variable working conditions, α reheating coefficient, β enthalpy drop correction coefficient, gamma thermodynamic system correction coefficient, and delta HR is the variation amplitude of the unit heat rate before and after variable working conditions.
2. The method for constructing the differential consumption quantitative calculation model for the variable-pressure operation of the improved steam turbine set according to claim 1, wherein the enthalpy drop correction coefficient β and the thermodynamic system correction coefficient γ are corrected and calculated by using special simulation software of the steam turbine set or an EXCEL self-programming thermodynamic calculation program according to ASME PTC6A-1982 calculation examples according to unit design parameters or experimental parameters.
3. The method for constructing the differential consumption quantitative calculation model for the variable-pressure operation of the improved steam turbine set according to claim 1, wherein for the steam turbine set adopting a multi-step sequence opening mode, a valve point is taken as a demarcation point, and segmented correction accounting is performed on an enthalpy drop correction coefficient beta and a thermodynamic system correction coefficient gamma so as to improve the set heat consumption rate change resolution precision of the model; the nozzle steam distributor type A can be divided into three sections of four-valve point-three-valve point, three-valve point-two-valve point and two-valve throttling according to valve points in sequence; the overload steam compensating machine B can be divided into two sections of 'full open of a steam compensating valve, full close of the steam compensating valve, full open of a main regulating valve' and 'throttling of the main regulating valve' according to valve points.
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