Method and device for calculating medium-voltage bypass capacity of secondary reheating unit

Abstract

The invention discloses a medium-pressure bypass capacity calculation method and device for a secondary reheat unit, and the method comprises the steps: calculating the steam pressure of an inlet of a low-pressure bypass according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit; according to the low-pressure bypass inlet pressure and a secondary reheater preset steam parameter of the secondary reheating unit, a secondary reheater inlet steam parameter is calculated; according to the secondary reheater inlet steam parameters and medium-pressure bypass preset steam parameters of the secondary reheating unit, medium-pressure bypass inlet steam pressure and medium-pressure bypass inlet steam flow are calculated; and under the condition that the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow meet preset conditions, the medium-pressure bypass capacity is calculated according to the medium-pressure bypass inlet steam flow. According to the technical scheme provided by the embodiment of the invention, the reasonability and accuracy of medium-voltage bypass capacity selection and the safety of system operation are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-supercritical secondary reheat generator sets, and in particular to a method and device for calculating the medium-pressure bypass capacity of a secondary reheat generator set. Background Art

[0002] Ultra-supercritical double reheat units are the main models of units recently put into operation at home and abroad. In the face of the current power structure gradually transforming towards a more efficient and clean direction, higher requirements are put forward for the flexible operation of double reheat units. Under the current situation where rapid start and stop, rapid ramping, and ultra-low load operation have become the norm, the blockage and burst of boiler tubes caused by the peeling of oxide scale on the high-temperature heating surface and the erosion of solid particles in the turbine are one of the most prominent problems.

[0003] For the secondary reheat units that have been put into operation, in order to prevent boiler tube bursts and erosion of the turbine flow section caused by solid particles such as scale, and to improve the operating reliability and economy of the secondary reheat units, the high, medium and low three-stage series bypass scale large momentum flushing technology is usually adopted during the startup or shutdown stage. The selection of high, medium and low three-stage bypass capacity is crucial for the secondary reheat units.

[0004] At present, for the secondary reheat unit, the high-pressure bypass system selects 100% capacity while taking into account the boiler safety valve function; the low-pressure bypass system selects 65% capacity, which is limited by the condensing capacity of the condenser itself. There is no generally accepted configuration selection and calculation method for the selection of medium-pressure bypass system capacity. Compared with the 100% bypass capacity of a single million-unit unit and the 65% bypass capacity of a single million-unit unit, pipelines, valves, matching cooling water systems, and feedwater pump output all require increased investment. According to preliminary calculations, the difference between the two capacity bypass systems is about 50 million. Therefore, there is an urgent need for an accurate and reasonable method for calculating the configuration of medium-pressure bypass capacity for secondary reheat units. Summary of the invention

[0005] The present invention provides a method and device for calculating the medium-pressure bypass capacity of a secondary reheat unit, so as to solve the problem of unreasonable and inaccurate selection of the medium-pressure bypass capacity of the secondary reheat unit in the prior art.

[0006] According to one aspect of the present invention, a method for calculating the medium-pressure bypass capacity of a secondary reheat unit is provided, comprising:

[0007] Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit;

[0008] Calculating a secondary reheater inlet steam parameter according to the low-pressure bypass inlet pressure and a secondary reheater preset steam parameter of the secondary reheat unit;

[0009] Calculating the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit;

[0010] When the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate meet preset conditions, the medium-pressure bypass capacity is calculated according to the medium-pressure bypass inlet steam flow rate.

[0011] Optionally, the preset steam parameters of the low-pressure bypass include: low-pressure bypass outlet design steam temperature, low-pressure bypass outlet design steam pressure, low-pressure bypass inlet design steam flow, low-pressure bypass desuperheating water enthalpy value, low-pressure bypass inlet design steam temperature, and low-pressure bypass resistance coefficient;

[0012] The calculation of the low-pressure bypass inlet steam pressure according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit includes:

[0013] According to the low-pressure bypass outlet design steam temperature and the low-pressure bypass outlet design steam pressure, by querying the water and steam property calculation table and the steam enthalpy table, the low-pressure bypass outlet steam density and the low-pressure bypass outlet steam enthalpy are determined;

[0014] Obtain the initial value of the low-pressure bypass inlet steam pressure;

[0015] According to the initial value of the low-pressure bypass inlet steam pressure and the designed steam temperature at the low-pressure bypass inlet, by querying the water and steam property calculation table and the steam enthalpy table, the low-pressure bypass inlet steam density and the low-pressure bypass inlet steam enthalpy are determined;

[0016] Calculate the steam flow rate at the low-pressure bypass outlet according to the low-pressure bypass inlet design steam flow rate, the low-pressure bypass outlet steam enthalpy value, the low-pressure bypass inlet steam enthalpy value and the low-pressure bypass desuperheating water enthalpy value;

[0017] The low-pressure bypass inlet steam pressure is calculated according to the low-pressure bypass outlet steam flow rate, the low-pressure bypass outlet steam density, the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam pressure initial value, the low-pressure bypass resistance coefficient and the low-pressure bypass outlet design steam pressure.

[0018] Optionally, after calculating the low-pressure bypass inlet steam pressure according to the low-pressure bypass outlet steam flow rate, the low-pressure bypass outlet steam density, the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam pressure initial value, the low-pressure bypass resistance coefficient and the low-pressure bypass outlet design steam pressure, the method further includes:

[0019] Calculating a first deviation between the low-pressure bypass inlet steam pressure and an initial value of the low-pressure bypass inlet steam pressure;

[0020] Determining whether the first deviation is less than a first preset deviation threshold;

[0021] When the first deviation is less than or equal to the first preset deviation threshold, outputting the low-pressure bypass inlet steam pressure and the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam enthalpy, and the low-pressure bypass inlet steam flow rate corresponding to the low-pressure bypass inlet steam pressure;

[0022] When the first deviation is greater than the first preset deviation threshold, the step of obtaining the initial value of the low-pressure bypass inlet steam pressure is returned to, and the calculation is continued using the low-pressure bypass inlet steam pressure as the initial value.

[0023] Optionally, the preset steam parameters of the secondary reheater include: the secondary reheater outlet design steam temperature, the secondary reheater inlet design steam temperature and the secondary reheater resistance coefficient;

[0024] The secondary reheater inlet steam parameters include: secondary reheater inlet steam pressure, secondary reheater inlet steam flow rate and secondary reheater inlet steam density;

[0025] Calculating the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit three-stage bypass system includes:

[0026] Obtain the initial value of the secondary reheater inlet steam pressure;

[0027] According to the initial value of the steam pressure at the secondary reheater inlet and the designed steam temperature at the secondary reheater inlet, the steam density at the secondary reheater inlet is determined by querying a water and steam property calculation table;

[0028] Determine the inlet design steam flow rate in the low-pressure bypass preset steam parameters as the inlet steam flow rate of the secondary reheater;

[0029] The secondary reheater inlet steam pressure is calculated according to the secondary reheater inlet steam density, the low-pressure bypass inlet steam flow rate, the low-pressure bypass inlet steam density corresponding to the low-pressure bypass inlet steam pressure, the initial value of the secondary reheater inlet steam pressure, the secondary reheater resistance coefficient and the low-pressure bypass inlet pressure.

[0030] Optionally, after calculating the secondary reheater inlet steam pressure according to the secondary reheater inlet steam density, the low-pressure bypass inlet steam flow rate, the low-pressure bypass inlet steam density corresponding to the low-pressure bypass inlet steam pressure, the secondary reheater inlet steam pressure initial value, the secondary reheater resistance coefficient and the low-pressure bypass inlet pressure, the further comprising:

[0031] calculating a second deviation of the steam pressure at an inlet of the secondary reheater from an initial value of the steam pressure at an inlet of the secondary reheater;

[0032] Determining whether the second deviation is less than a second preset deviation threshold;

[0033] When the second deviation is less than or equal to the second preset deviation threshold, outputting the secondary reheater inlet steam pressure and the secondary reheater inlet steam density and the secondary reheater inlet steam flow rate corresponding to the secondary reheater inlet steam pressure;

[0034] When the second deviation is greater than the second preset deviation threshold, the process returns to the step of obtaining the initial value of the secondary reheater inlet steam pressure, and continues the calculation by taking the secondary reheater inlet steam pressure as the initial value.

[0035] Optionally, the preset steam parameters of the medium-pressure bypass include: the designed steam temperature at the outlet of the medium-pressure bypass, the enthalpy value of the medium-pressure bypass desuperheating water, the designed steam temperature at the inlet of the medium-pressure bypass, and the resistance coefficient of the medium-pressure bypass;

[0036] The calculating the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameter at the inlet of the secondary reheater and the preset steam parameter of the medium-pressure bypass of the three-stage bypass system of the secondary reheat unit comprises:

[0037] Obtain the initial value of the medium-pressure bypass inlet steam pressure;

[0038] According to the initial value of the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet design steam temperature, by querying the water and steam property calculation table and the water vapor enthalpy table, the medium-pressure bypass inlet steam density and the medium-pressure bypass inlet steam enthalpy are determined;

[0039] Calculate the steam flow rate at the inlet of the medium-pressure bypass according to the steam flow rate at the inlet of the secondary reheater corresponding to the steam pressure at the inlet of the secondary reheater, the enthalpy value of the medium-pressure bypass desuperheating water, the enthalpy value of the steam at the inlet of the secondary reheater and the enthalpy value of the steam at the inlet of the medium-pressure bypass;

[0040] The medium-pressure bypass inlet steam pressure is calculated according to the medium-pressure bypass inlet steam density, the secondary reheater inlet steam flow rate, the secondary reheater inlet steam density, the initial value of the medium-pressure bypass inlet steam pressure, the medium-pressure bypass resistance coefficient and the secondary reheater inlet steam pressure.

[0041] Optionally, after calculating the steam pressure at the medium-pressure bypass inlet according to the steam density at the medium-pressure bypass inlet, the steam flow rate at the secondary reheater inlet, the medium-pressure bypass resistance coefficient and the steam pressure at the secondary reheater inlet, the method further includes:

[0042] Calculating a third deviation between the medium-pressure bypass inlet steam pressure and an initial value of the medium-pressure bypass inlet steam pressure;

[0043] Determining whether the third deviation is less than a third preset deviation threshold;

[0044] When the third deviation is less than or equal to the third preset deviation threshold, output the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam density, medium-pressure bypass inlet steam enthalpy, and medium-pressure bypass inlet steam flow rate corresponding to the medium-pressure bypass inlet steam pressure;

[0045] When the third deviation is greater than the third preset deviation threshold, the process returns to the step of obtaining the initial value of the medium-pressure bypass inlet steam pressure, and continues the calculation by taking the medium-pressure bypass inlet steam pressure as the initial value.

[0046] Optionally, when the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, calculating the medium-pressure bypass capacity according to the steam flow rate at the medium-pressure bypass inlet includes:

[0047] When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, converting the steam flow rate at the medium-pressure bypass inlet to the steam flow rate at the medium-pressure bypass inlet under rated steam parameters;

[0048] The medium-pressure bypass capacity is calculated based on the medium-pressure bypass inlet steam flow rate under the rated steam parameters and the main steam flow rate under the maximum continuous evaporation capacity condition of the secondary reheat unit.

[0049] Optionally, the capacity calculation method further includes:

[0050] When the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate do not meet the preset conditions, return to execute the step of calculating the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate based on the secondary reheater inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit three-stage bypass system.

[0051] According to another aspect of the present invention, there is provided a medium-pressure bypass capacity calculation device for a secondary reheat unit, comprising:

[0052] A low-pressure bypass inlet steam pressure calculation module, which is used to calculate the low-pressure bypass inlet steam pressure according to the low-pressure bypass preset steam parameters of the secondary reheat unit;

[0053] A secondary reheater inlet steam parameter calculation module, the secondary reheater inlet steam parameter calculation module is used to calculate the secondary reheater inlet steam parameter according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameter of the secondary reheater unit;

[0054] A medium-pressure bypass inlet steam pressure and flow calculation module, the medium-pressure bypass inlet steam pressure and flow calculation module is used to calculate the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow according to the secondary reheater inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit;

[0055] A medium-pressure bypass capacity calculation module is used to calculate the medium-pressure bypass capacity according to the medium-pressure bypass inlet steam flow when the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow meet preset conditions.

[0056] An embodiment of the present invention provides a method and device for calculating the medium-pressure bypass capacity of a secondary reheat unit, wherein the method comprises: calculating the low-pressure bypass inlet steam pressure according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit; calculating the secondary reheat inlet steam parameters according to the low-pressure bypass inlet pressure and the preset steam parameters of the secondary reheater of the secondary reheat unit; calculating the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow according to the secondary reheat inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit; and calculating the medium-pressure bypass capacity according to the medium-pressure bypass inlet steam flow when the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow meet preset conditions. The technical solution provided in the embodiment of the present invention uses known design parameters to calculate the low-pressure bypass inlet steam pressure, secondary reheater inlet steam parameters, medium-pressure bypass inlet steam pressure and medium-pressure bypass inlet steam flow rate step by step, and then calculates the medium-pressure bypass capacity. Compared with the prior art, the technical solution provided in the embodiment of the present invention is for the accurate selection and configuration of the pipeline capacity of the medium-pressure bypass, provides an accurate, reasonable and scientific guiding basis, solves the problem of unreasonable and inaccurate selection in the prior art, and effectively improves the rationality and accuracy of the selection of the medium-pressure bypass capacity and the safety of system operation.

[0057] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0059] Figure 1 A flow chart of a method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0060] Figure 2 A flow chart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0061] Figure 3 A flow chart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0062] Figure 4 A flow chart of a method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0063] Figure 5 A flow chart of a method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0064] Figure 6 A flow chart of a method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0065] Figure 7 A flow chart of a method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention;

[0066] Figure 8 A schematic structural diagram of a medium-pressure bypass capacity calculation device for a secondary reheat unit provided in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0067] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0068] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0069] Figure 1 This is a flow chart of a method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention. This embodiment is applicable to the case of calculating and selecting the pipeline capacity of the medium-pressure bypass of a secondary reheat unit. This method can be executed by a medium-pressure bypass capacity calculation device of a secondary reheat unit. Figure 1 , the capacity calculation method includes:

[0070] S110. Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit.

[0071] The preset steam parameters of the low-pressure bypass can be preset based on the equipment selection parameters of the secondary reheat unit, such as the boiler model, condenser model and / or secondary reheater model. The preset steam parameters of the low-pressure bypass include parameters such as the low-pressure bypass outlet design steam temperature, the low-pressure bypass outlet design steam pressure, and the low-pressure bypass resistance coefficient.

[0072] Specifically, the steam pressure at the inlet of the low-pressure bypass is calculated according to the parameters such as the design steam temperature at the outlet of the low-pressure bypass, the design steam pressure at the outlet of the low-pressure bypass, and the design steam flow rate at the inlet of the low-pressure bypass. Since the three-stage bypass system of the secondary reheat unit includes the superheater, high-pressure bypass, primary reheater, medium-pressure bypass, secondary reheater, low-pressure bypass and condenser connected in sequence; pressure reducing valves are arranged on the high-pressure bypass, medium-pressure bypass and low-pressure bypass; the boiler steam passes through the high-pressure bypass, primary reheater, medium-pressure bypass, secondary reheater, low-pressure bypass and condenser in sequence from the outlet of the superheater, and the selection models of the primary reheater, secondary reheater and condenser have been determined following the selection model of the boiler, and belong to known parameters. Therefore, according to the known parameters, the low-pressure bypass connected to the condenser is selected to be calculated step by step to the medium-pressure bypass, and then the medium-pressure bypass capacity is calculated. Therefore, the steam pressure at the inlet of the low-pressure bypass is calculated first according to the preset steam parameters of the low-pressure bypass.

[0073] S120. Calculate the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit.

[0074] Among them, the preset steam parameters of the secondary reheater can be preset based on the equipment selection parameters of the secondary reheat unit, for example, the boiler model, condenser model and / or secondary reheater model and other selection parameters. The preset steam parameters of the secondary reheater include parameters such as the secondary reheater outlet design steam temperature, the secondary reheater outlet design steam pressure, the secondary reheater inlet design steam temperature, and the secondary reheater inlet design steam flow rate. The secondary reheater inlet steam parameters include parameters such as the secondary reheater outlet design steam temperature, the secondary reheater inlet design steam temperature, and the secondary reheater resistance coefficient.

[0075] Specifically, according to the low-pressure bypass inlet pressure, the secondary reheater outlet design steam temperature, the secondary reheater inlet design steam temperature, the secondary reheater resistance coefficient and other parameters, the secondary reheater inlet steam pressure and the secondary reheater inlet steam flow rate corresponding to the secondary reheater inlet steam pressure are calculated.

[0076] S130. Calculate the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit.

[0077] The preset steam parameters of the medium-pressure bypass can be preset based on the equipment selection parameters of the secondary reheat unit, such as the boiler model, condenser model and / or secondary reheater model. The preset steam parameters of the medium-pressure bypass include parameters such as the medium-pressure bypass outlet design steam temperature, the medium-pressure bypass desuperheating water enthalpy value, the medium-pressure bypass inlet design steam temperature, and the medium-pressure bypass resistance coefficient.

[0078] Specifically, the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate are calculated based on parameters such as the medium-pressure bypass inlet steam density, the secondary reheater inlet steam flow rate, the secondary reheater inlet steam density, the initial value of the medium-pressure bypass inlet steam pressure, the medium-pressure bypass resistance coefficient, and the secondary reheater inlet steam pressure.

[0079] S140. When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, calculate the medium-pressure bypass capacity according to the steam flow rate at the medium-pressure bypass inlet.

[0080] Among them, the preset conditions can be set in advance based on the objective laws and facts of system operation and engineering requirements.

[0081] Specifically, determine whether the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate meet the preset conditions. If so, calculate the medium-pressure bypass capacity according to the medium-pressure bypass inlet steam flow rate; if not, recalculate the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate according to the secondary reheater inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit until the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate meet the preset conditions.

[0082] The technical solution provided in the embodiment of the present invention uses known design parameters to calculate the low-pressure bypass inlet steam pressure, secondary reheater inlet steam parameters, medium-pressure bypass inlet steam pressure and medium-pressure bypass inlet steam flow rate step by step, and then calculates the medium-pressure bypass capacity. Compared with the prior art, the technical solution provided in the embodiment of the present invention is for the accurate selection and configuration of the pipeline capacity of the medium-pressure bypass, provides an accurate, reasonable and scientific guiding basis, solves the problem of unreasonable and inaccurate selection in the prior art, and effectively improves the rationality and accuracy of the selection of the medium-pressure bypass capacity and the safety of system operation.

[0083] Figure 2 The flowchart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention is a further refinement of the above embodiment on the basis of the above embodiment. The preset steam parameters of the low-pressure bypass include: the design steam temperature of the low-pressure bypass outlet, the design steam pressure of the low-pressure bypass outlet, the design steam flow rate of the low-pressure bypass inlet, the enthalpy value of the low-pressure bypass desuperheating water, the design steam temperature of the low-pressure bypass inlet, and the resistance coefficient of the low-pressure bypass; see Figure 2 , the capacity calculation method includes:

[0084] S210. According to the design steam temperature and the design steam pressure of the low-pressure bypass outlet, the steam density and the steam enthalpy value of the low-pressure bypass outlet are determined by consulting the water and steam property calculation table and the steam enthalpy value table.

[0085] Specifically, according to the design steam temperature and the design steam pressure of the low-pressure bypass outlet, the steam density of the low-pressure bypass outlet is determined by querying the water and steam property calculation table; according to the design steam temperature and the design steam pressure of the low-pressure bypass outlet, the steam enthalpy of the low-pressure bypass outlet is determined by querying the steam enthalpy table.

[0086] S211. Obtain the initial value of the low-pressure bypass inlet steam pressure.

[0087] Specifically, the initial value of the low-pressure bypass inlet steam pressure can be the low-pressure bypass inlet steam pressure at time 0 pre-set according to the low-pressure bypass resistance coefficient, or the low-pressure bypass inlet steam pressure obtained by iterative calculation at time i-1, and the low-pressure bypass inlet steam pressure is finally calculated through S212 to S214. Before starting the calculation, the low-pressure bypass inlet steam pressure pre-set at time 0 is used as the initial value of the low-pressure bypass inlet steam pressure to calculate the low-pressure bypass inlet steam pressure. If the deviation between the calculated low-pressure bypass inlet steam pressure and the initial value of the low-pressure bypass inlet steam pressure does not meet the allowable accuracy, the low-pressure bypass inlet steam pressure calculated this time is substituted into the initial value as the low-pressure bypass inlet steam pressure calculated at time i-1, and the calculation is performed at time i, and so on, to achieve iterative calculation until the deviation between the calculated low-pressure bypass inlet steam pressure and the initial value of the low-pressure bypass inlet steam pressure meets the allowable accuracy.

[0088] S212. According to the initial value of the low-pressure bypass inlet steam pressure and the designed steam temperature at the low-pressure bypass inlet, the steam density at the low-pressure bypass inlet and the steam enthalpy value at the low-pressure bypass inlet are determined by consulting the water and steam property calculation table and the steam enthalpy value table.

[0089] Specifically, according to the initial value of the low-pressure bypass inlet steam pressure and the low-pressure bypass inlet design steam temperature, the low-pressure bypass inlet steam density is determined by querying the water and steam property calculation table; according to the initial value of the low-pressure bypass inlet steam pressure and the low-pressure bypass inlet design steam temperature, the low-pressure bypass inlet steam enthalpy is determined by querying the steam enthalpy table. It should be noted that the low-pressure bypass inlet steam density and the low-pressure bypass inlet steam enthalpy change with the low-pressure bypass inlet steam pressure value.

[0090] S213. Calculate the steam flow rate at the low-pressure bypass outlet according to the designed steam flow rate at the low-pressure bypass inlet, the steam enthalpy value at the low-pressure bypass outlet, the steam enthalpy value at the low-pressure bypass inlet and the enthalpy value of the low-pressure bypass desuperheating water.

[0091] It should be noted that the steam flow rate at the low-pressure bypass outlet changes in real time with the steam enthalpy value at the low-pressure bypass inlet. When the initial value of the low-pressure bypass inlet steam pressure changes, the low-pressure bypass inlet steam density and the low-pressure bypass inlet steam enthalpy value obtained from the table according to the initial value of the low-pressure bypass inlet steam pressure will also change. The low-pressure bypass outlet steam flow rate calculated based on parameters such as the low-pressure bypass inlet steam enthalpy value will also change.

[0092] Specifically, the low-pressure bypass outlet steam flow rate is calculated using the following formula:

[0093]

[0094] Where Qm dp,out is the steam flow rate at the low-pressure bypass outlet, Design steam flow rate for low pressure bypass inlet, h dpout is the steam enthalpy at the low-pressure bypass outlet, h dpin is the steam enthalpy at the low-pressure bypass inlet, It is the enthalpy value of low-pressure bypass desuperheating water.

[0095] S214. Calculate the low-pressure bypass inlet steam pressure according to the low-pressure bypass outlet steam flow rate, the low-pressure bypass outlet steam density, the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam pressure initial value, the low-pressure bypass resistance coefficient and the low-pressure bypass outlet design steam pressure.

[0096] It should be noted that the low-pressure bypass inlet steam pressure changes in real time with the low-pressure bypass inlet steam flow rate. Since the low-pressure bypass outlet steam flow rate changes in real time with the low-pressure bypass inlet steam enthalpy value, when the low-pressure bypass inlet steam pressure initial value changes, the low-pressure bypass inlet steam density and low-pressure bypass inlet steam enthalpy value obtained by looking up the table will also change according to the low-pressure bypass inlet steam pressure initial value, and the low-pressure bypass outlet steam flow rate calculated according to the low-pressure bypass inlet steam enthalpy value and other parameters will also change, and then the low-pressure bypass inlet steam pressure calculated according to the low-pressure bypass outlet steam flow rate and other parameters will also change. In other words, a low-pressure bypass inlet steam pressure initial value corresponds to a low-pressure bypass inlet steam density, a low-pressure bypass inlet steam enthalpy value, a low-pressure bypass outlet steam flow rate, and a low-pressure bypass inlet steam pressure.

[0097] Specifically, the low-pressure bypass inlet steam pressure is calculated using the following formula:

[0098]

[0099] Where P dp,in is the low pressure bypass inlet steam pressure, Design steam pressure for low pressure bypass outlet, Qm dp,out is the steam flow rate at the low pressure bypass outlet, K dp is the low pressure bypass resistance coefficient, ρ dp,in is the steam density at the low pressure bypass inlet, ρ dp,out is the steam density at the low pressure bypass outlet, is the initial value of the low-pressure bypass inlet steam pressure, Design steam pressure for low pressure bypass outlet.

[0100] S215. Calculate a first deviation between the low-pressure bypass inlet steam pressure and the initial value of the low-pressure bypass inlet steam pressure.

[0101] Specifically, the steam pressure at the low-pressure bypass inlet is firstly subtracted from the initial value of the steam pressure at the low-pressure bypass inlet to obtain a difference, and then the difference is divided by the initial value of the steam pressure at the low-pressure bypass inlet to obtain a first deviation. That is, the first deviation = (steam pressure at the low-pressure bypass inlet - initial value of the steam pressure at the low-pressure bypass inlet) / initial value of the steam pressure at the low-pressure bypass inlet.

[0102] S216, determine whether the first deviation is less than a first preset deviation threshold; if so, execute S217; if not, return to execute S211.

[0103] The first preset deviation threshold may be preset based on engineering requirements. For example, the first preset deviation threshold is 1%.

[0104] S217. Output the low-pressure bypass inlet steam pressure and the low-pressure bypass inlet steam density, low-pressure bypass inlet steam enthalpy, and low-pressure bypass inlet steam flow rate corresponding to the low-pressure bypass inlet steam pressure.

[0105] Specifically, when a first deviation between the low-pressure bypass inlet steam pressure and the initial value of the low-pressure bypass inlet steam pressure is less than or equal to a first preset deviation threshold, the low-pressure bypass inlet steam pressure and the corresponding low-pressure bypass inlet steam density, low-pressure bypass inlet steam enthalpy, and low-pressure bypass inlet steam flow rate are output.

[0106] S218. Calculate the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit.

[0107] This step is the same as the step S120 in the above embodiment and will not be described again here.

[0108] S219. Calculate the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit.

[0109] This step is the same as the step S130 in the above embodiment and will not be described again here.

[0110] S220. When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, calculate the medium-pressure bypass capacity according to the steam flow rate at the medium-pressure bypass inlet.

[0111] This step is the same as the method step S140 in the above embodiment and will not be repeated here.

[0112] The technical solution provided by the embodiment of the present invention utilizes known design parameters, iteratively calculates the low-pressure bypass inlet steam pressure, and determines whether the first deviation of the calculated low-pressure bypass inlet steam pressure and the initial value of the low-pressure bypass inlet steam pressure meets the allowable accuracy. When the first deviation does not meet the allowable accuracy, the initial value of the low-pressure bypass inlet steam pressure is continuously corrected to improve the calculation accuracy of the low-pressure bypass inlet steam pressure, thereby further effectively improving the rationality and accuracy of the medium-pressure bypass capacity selection and the safety of the system operation.

[0113] Figure 3 A flowchart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention. The embodiment of the present invention further refines the above embodiments on the basis of the above embodiments. The preset steam parameters of the secondary reheater include: the secondary reheater outlet design steam temperature, the secondary reheater inlet design steam temperature and the secondary reheater resistance coefficient; the secondary reheater inlet steam parameters include: the secondary reheater inlet steam pressure, the secondary reheater inlet steam flow rate and the secondary reheater inlet steam density; see Figure 3 , the capacity calculation method includes:

[0114] S310. Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit.

[0115] This step is the same as the step in the above embodiment S110 and will not be described again here.

[0116] S311. Obtain the initial value of the secondary reheater inlet steam pressure.

[0117] Specifically, the initial value of the secondary reheater inlet steam pressure may be the secondary reheater inlet steam pressure at time 0 pre-set according to the secondary reheater resistance coefficient, or the secondary reheater inlet steam pressure obtained by iterative calculation at time i-1, and the secondary reheater inlet steam pressure finally calculated through S312 to S314. Before starting the calculation, the secondary reheater inlet steam pressure pre-set at time 0 is used as the initial value of the secondary reheater inlet steam pressure to calculate the secondary reheater inlet steam pressure. If it is determined that the deviation between the calculated secondary reheater inlet steam pressure and the initial value of the secondary reheater inlet steam pressure does not meet the allowable accuracy, the secondary reheater inlet steam pressure calculated this time is substituted into the initial value as the secondary reheater inlet steam pressure calculated at time i-1, and the calculation is performed at time i, and so on, to achieve iterative calculation until the deviation between the calculated secondary reheater inlet steam pressure and the initial value of the secondary reheater inlet steam pressure meets the allowable accuracy.

[0118] S312. According to the initial value of the steam pressure at the secondary reheater inlet and the design steam temperature at the secondary reheater inlet, the steam density at the secondary reheater inlet is determined by querying the water and steam property calculation table.

[0119] S313. Determine the inlet design steam flow rate in the low-pressure bypass preset steam parameters as the secondary reheater inlet steam flow rate.

[0120] Specifically, since the secondary reheater is connected to the condenser through a low-pressure bypass, the low-pressure bypass inlet is also the secondary reheater outlet, and the flow rates at the secondary reheater outlet and inlet are unchanged, so the design steam flow rate at the low-pressure bypass inlet = the secondary reheater outlet steam flow rate = the secondary reheater inlet steam flow rate.

[0121] S314. Calculate the steam pressure at the secondary reheater inlet according to the steam density at the secondary reheater inlet, the steam flow rate at the low-pressure bypass inlet, the low-pressure bypass inlet steam density corresponding to the low-pressure bypass inlet steam pressure, the initial value of the steam pressure at the secondary reheater inlet, the resistance coefficient of the secondary reheater and the low-pressure bypass inlet pressure.

[0122] Among them, the steam pressure at the inlet of the secondary reheater changes in real time. The principle of the change is the same as the steam pressure at the inlet of the low-pressure bypass in the above embodiment, and will not be repeated here.

[0123] Specifically, the secondary reheater inlet steam pressure is calculated using the following formula:

[0124]

[0125] Where P ez,in is the steam pressure at the secondary reheater inlet, P dp,in is the low pressure bypass inlet steam pressure, is the initial value of the steam pressure at the secondary reheater inlet, is the design steam pressure at the secondary reheater outlet, ρ dp,in is the steam density at the low-pressure bypass inlet corresponding to the low-pressure bypass inlet steam pressure, ρ ez,in is the steam density at the secondary reheater inlet, Design steam flow rate for low pressure bypass inlet, K ez is the secondary reheater resistance coefficient.

[0126] S315. Calculate a second deviation between the steam pressure at the secondary reheater inlet and the initial value of the steam pressure at the secondary reheater inlet.

[0127] Specifically, the steam pressure at the secondary reheater inlet is first subtracted from the initial value of the steam pressure at the secondary reheater inlet to obtain a difference, and then the difference is divided by the initial value of the steam pressure at the secondary reheater inlet to obtain the second deviation. That is, the second deviation = (steam pressure at the secondary reheater inlet - initial value of the steam pressure at the secondary reheater inlet) / initial value of the steam pressure at the secondary reheater inlet.

[0128] S316, determine whether the second deviation is less than the second preset deviation threshold; if so, execute S317; if not, return to execute S311.

[0129] The second preset deviation threshold may be preset based on engineering requirements. For example, the first preset deviation threshold is 1%.

[0130] S317. Output the secondary reheater inlet steam pressure, and the secondary reheater inlet steam density and secondary reheater inlet steam flow rate corresponding to the secondary reheater inlet steam pressure.

[0131] Specifically, when the second deviation between the secondary reheater inlet steam pressure and the initial value of the secondary reheater inlet steam pressure is less than or equal to the second preset deviation threshold, the secondary reheater inlet steam pressure and the corresponding secondary reheater inlet steam density and secondary reheater inlet steam flow rate under the secondary reheater inlet steam pressure are output.

[0132] S318. Calculate the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit.

[0133] This step is the same as the step S130 in the above embodiment and will not be described again here.

[0134] S319. When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, calculate the medium-pressure bypass capacity according to the steam flow rate at the medium-pressure bypass inlet.

[0135] This step is the same as the method step S140 in the above embodiment and will not be repeated here.

[0136] The technical solution provided by the embodiment of the present invention utilizes known design parameters, iteratively calculates the secondary reheater inlet steam pressure, and determines whether the second deviation of the calculated secondary reheater inlet steam pressure and the initial value of the secondary reheater inlet steam pressure meets the allowable accuracy. When the second deviation does not meet the allowable accuracy, the initial value of the secondary reheater inlet steam pressure is continuously corrected to improve the calculation accuracy of the secondary reheater inlet steam pressure, thereby further effectively improving the rationality and accuracy of the medium-pressure bypass capacity selection and the safety of the system operation.

[0137] Figure 4The flow chart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention is a further refinement of the above embodiments based on the above embodiments. The preset steam parameters of the medium-pressure bypass include: the design steam temperature at the outlet of the medium-pressure bypass, the enthalpy value of the medium-pressure bypass desuperheating water, the design steam temperature at the inlet of the medium-pressure bypass, and the resistance coefficient of the medium-pressure bypass; see Figure 4 , the capacity calculation method includes:

[0138] S410. Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit.

[0139] This step is the same as the step in the above embodiment S110 and will not be described again here.

[0140] S411. Calculate the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit.

[0141] This step is the same as the step S120 in the above embodiment and will not be described again here.

[0142] S412. Obtain the initial value of the medium-pressure bypass inlet steam pressure.

[0143] Specifically, the initial value of the medium-pressure bypass inlet steam pressure can be the medium-pressure bypass inlet steam pressure at time 0 pre-set according to the medium-pressure bypass resistance coefficient, or the medium-pressure bypass inlet steam pressure obtained by iterative calculation at time i-1. The medium-pressure bypass inlet steam pressure is finally calculated through S413 to S415. Before starting the calculation, the medium-pressure bypass inlet steam pressure pre-set at time 0 is used as the initial value of the medium-pressure bypass inlet steam pressure to calculate the medium-pressure bypass inlet steam pressure. If the deviation between the calculated medium-pressure bypass inlet steam pressure and the initial value of the medium-pressure bypass inlet steam pressure does not meet the allowable accuracy, the medium-pressure bypass inlet steam pressure calculated this time is used as the medium-pressure bypass inlet steam pressure calculated at time i-1 and substituted into the initial value to perform calculation at time i, and so on, to achieve iterative calculation until the deviation between the calculated medium-pressure bypass inlet steam pressure and the initial value of the medium-pressure bypass inlet steam pressure meets the allowable accuracy.

[0144] S413. According to the initial value of the steam pressure at the medium-pressure bypass inlet and the designed steam temperature at the medium-pressure bypass inlet, the steam density at the medium-pressure bypass inlet and the steam enthalpy value at the medium-pressure bypass inlet are determined by consulting the water and steam property calculation table and the water vapor enthalpy value table.

[0145] Specifically, according to the initial value of the steam pressure at the medium-pressure bypass inlet and the designed steam temperature at the medium-pressure bypass inlet, the steam density at the medium-pressure bypass inlet is determined by querying the water and steam property calculation table; according to the initial value of the steam pressure at the medium-pressure bypass inlet and the designed steam temperature at the medium-pressure bypass inlet, the steam enthalpy value at the medium-pressure bypass inlet is determined by querying the steam enthalpy value table. It should be noted that the steam density at the medium-pressure bypass inlet and the steam enthalpy value at the medium-pressure bypass inlet change with the steam pressure value at the medium-pressure bypass inlet.

[0146] S414. Calculate the steam flow rate at the intermediate-pressure bypass inlet according to the secondary reheater inlet steam flow rate, the intermediate-pressure bypass desuperheating water enthalpy value, the secondary reheater inlet steam enthalpy value and the intermediate-pressure bypass inlet steam enthalpy value corresponding to the secondary reheater inlet steam pressure.

[0147] Among them, the steam flow rate at the medium-pressure bypass inlet changes in real time with the steam enthalpy value at the medium-pressure bypass inlet. When the initial value of the medium-pressure bypass inlet steam pressure changes, the medium-pressure bypass inlet steam density and the medium-pressure bypass inlet steam enthalpy value obtained from the table will also change according to the initial value of the medium-pressure bypass inlet steam pressure. The medium-pressure bypass outlet steam flow rate calculated according to parameters such as the medium-pressure bypass inlet steam enthalpy value will also change.

[0148] Specifically, the steam flow rate at the medium pressure bypass inlet is calculated using the following formula:

[0149]

[0150] Where Qm zp,in is the steam flow rate at the medium pressure bypass inlet, Qm ez,in is the steam flow rate at the secondary reheater inlet corresponding to the steam pressure at the secondary reheater inlet, is the enthalpy of medium pressure bypass desuperheating water, h zp,in is the steam enthalpy at the medium pressure bypass inlet, h ez,in is the steam enthalpy at the secondary reheater inlet.

[0151] S415. Calculate the steam pressure at the inlet of the medium-pressure bypass according to the steam density at the inlet of the medium-pressure bypass, the steam flow rate at the inlet of the secondary reheater, the steam density at the inlet of the secondary reheater, the initial value of the steam pressure at the inlet of the medium-pressure bypass, the resistance coefficient of the medium-pressure bypass and the steam pressure at the inlet of the secondary reheater.

[0152] Among them, the steam pressure at the medium-pressure bypass inlet changes in real time with the steam flow at the medium-pressure bypass inlet. Since the steam flow at the medium-pressure bypass outlet changes in real time with the steam enthalpy at the medium-pressure bypass inlet, when the initial value of the steam pressure at the medium-pressure bypass inlet changes, the steam density at the medium-pressure bypass inlet and the steam enthalpy at the medium-pressure bypass inlet obtained by looking up the table will also change according to the initial value of the steam pressure at the medium-pressure bypass inlet. The steam flow at the medium-pressure bypass outlet calculated according to the parameters such as the steam enthalpy at the medium-pressure bypass inlet will also change, and then the steam pressure at the medium-pressure bypass inlet calculated according to the parameters such as the steam flow at the medium-pressure bypass outlet will also change. In other words, one initial value of the steam pressure at the medium-pressure bypass inlet corresponds to one steam density at the medium-pressure bypass inlet, one steam enthalpy at the medium-pressure bypass inlet, one steam flow at the medium-pressure bypass outlet, and one steam pressure at the medium-pressure bypass inlet.

[0153] Specifically, the medium pressure bypass inlet steam pressure is calculated using the following formula:

[0154]

[0155] Where P zp,in is the low pressure bypass inlet steam pressure, P ez,in is the secondary reheater inlet steam pressure, is the initial value of the medium pressure bypass inlet steam pressure, Design steam pressure for medium pressure bypass outlet, Qm ez,in is the steam flow rate at the secondary reheater inlet, K zp is the medium pressure bypass resistance coefficient, ρ zp,in is the steam density at the medium pressure bypass inlet, ρ ez,in is the steam density at the secondary reheater inlet.

[0156] S416. Calculate a third deviation between the steam pressure at the medium-pressure bypass inlet and the initial value of the steam pressure at the medium-pressure bypass inlet.

[0157] Specifically, the steam pressure at the medium-pressure bypass inlet is firstly subtracted from the initial value of the steam pressure at the medium-pressure bypass inlet to obtain a difference, and then the difference is divided by the initial value of the steam pressure at the medium-pressure bypass inlet to obtain the third deviation. That is, the third deviation=(steam pressure at the medium-pressure bypass inlet-initial value of the steam pressure at the medium-pressure bypass inlet) / initial value of the steam pressure at the medium-pressure bypass inlet.

[0158] S417, determine whether the third deviation is less than the third preset deviation threshold; if so, execute S418; if not, return to execute S412.

[0159] The third preset deviation threshold can be preset based on engineering requirements, for example, the third preset deviation threshold is 1%. The first preset deviation threshold, the second preset deviation threshold and the third preset deviation threshold can be the same or different, and the present invention does not limit this.

[0160] S418. Output the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam density, medium-pressure bypass inlet steam enthalpy, and medium-pressure bypass inlet steam flow rate corresponding to the medium-pressure bypass inlet steam pressure.

[0161] Specifically, when the third deviation between the medium-pressure bypass inlet steam pressure and the initial value of the medium-pressure bypass inlet steam pressure is less than or equal to the third preset deviation threshold, the medium-pressure bypass inlet steam pressure and the corresponding medium-pressure bypass inlet steam density, medium-pressure bypass inlet steam enthalpy, and medium-pressure bypass inlet steam flow rate are output.

[0162] S419. When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, calculate the medium-pressure bypass capacity according to the steam flow rate at the medium-pressure bypass inlet.

[0163] This step is the same as the method step S140 in the above embodiment and will not be repeated here.

[0164] The technical solution provided by the embodiment of the present invention utilizes known design parameters, iteratively calculates the medium-pressure bypass inlet steam pressure, and determines whether the third deviation between the calculated medium-pressure bypass inlet steam pressure and the initial value of the medium-pressure bypass inlet steam pressure satisfies the allowable accuracy. When the third deviation does not satisfy the allowable accuracy, the initial value of the medium-pressure bypass inlet steam pressure is continuously corrected to improve the calculation accuracy of the medium-pressure bypass inlet steam pressure, thereby further effectively improving the rationality and accuracy of the medium-pressure bypass capacity selection and the safety of the system operation.

[0165] Figure 5 This is a flow chart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention. The embodiment of the present invention further refines the above embodiments on the basis of the above embodiments. Figure 5 , the capacity calculation method includes:

[0166] S510. Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit.

[0167] This step is the same as the step in the above embodiment S110 and will not be described again here.

[0168] S520. Calculate the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit.

[0169] This step is the same as the step S120 in the above embodiment and will not be described again here.

[0170] S530. Calculate the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit.

[0171] This step is the same as the step S130 in the above embodiment and will not be described again here.

[0172] S540. When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, convert the steam flow rate at the medium-pressure bypass inlet to the steam flow rate at the medium-pressure bypass inlet under rated steam parameters.

[0173] Among them, the criteria for judging whether the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet the preset conditions are:

[0174] ① The calculated steam pressure at the medium-pressure bypass inlet is compared with the steam pressure at the medium-pressure bypass inlet during normal operation of the secondary reheat unit, which is consistent with objective laws and facts.

[0175] ② The steam corresponding to the calculated medium-pressure bypass inlet steam pressure is superheated steam, and the calculated medium-pressure bypass inlet steam pressure exceeds the minimum safety limit of the pressure corresponding to the saturated steam temperature.

[0176] ③ The calculated steam flow rate at the medium-pressure bypass inlet shall not exceed the steam flow rate at the medium-pressure bypass inlet under the rated steam parameters.

[0177] Specifically, the following formula is used to convert the medium-pressure bypass inlet steam flow rate to the medium-pressure bypass inlet steam flow rate under rated steam parameters:

[0178]

[0179] In the formula, Qm is the steam flow rate at the medium pressure bypass inlet under rated steam parameters, zp,in is the steam flow rate at the medium pressure bypass inlet, P zp,in is the steam pressure at the medium pressure bypass inlet, Design steam pressure for low pressure bypass inlet, Design steam density for the medium pressure bypass inlet, ρ zp,in is the steam density at the medium pressure bypass inlet.

[0180] S550. Calculate the medium-pressure bypass capacity based on the medium-pressure bypass inlet steam flow rate under rated steam parameters and the main steam flow rate under the maximum continuous evaporation condition of the secondary reheat unit.

[0181] Specifically, the medium pressure bypass capacity is calculated using the following formula:

[0182]

[0183] Where η zp is the medium pressure bypass capacity, Qm is the steam flow rate at the medium pressure bypass inlet under rated steam parameters, BMCR,out It is the main steam flow rate under the maximum continuous evaporation condition of the double reheat unit.

[0184] Figure 6 This is a flow chart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention. The embodiment of the present invention further refines the above embodiments on the basis of the above embodiments. Figure 6 , the capacity calculation method includes:

[0185] S610. Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit.

[0186] S620. Calculate the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit.

[0187] S630. Calculate the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit.

[0188] S640, determine whether the steam pressure and steam flow rate at the medium-pressure bypass inlet meet preset conditions; if so, execute S650; if not, return to execute S630.

[0189] S650. Calculate the medium-pressure bypass capacity based on the medium-pressure bypass inlet steam flow.

[0190] The following is a specific example to introduce the method for calculating the medium-pressure bypass capacity of the secondary reheat unit provided in the present application.

[0191] Figure 7 This is a flow chart of another method for calculating the medium-pressure bypass capacity of a secondary reheat unit provided in an embodiment of the present invention. The embodiment of the present invention further refines the above embodiments on the basis of the above embodiments. Figure 7 , the capacity calculation method includes:

[0192] S710. According to the design steam temperature and the design steam pressure of the low-pressure bypass outlet, the steam density and the steam enthalpy of the low-pressure bypass outlet are determined by consulting the water and steam property calculation table and the steam enthalpy table.

[0193] S711. Obtain the initial value of the low-pressure bypass inlet steam pressure.

[0194] S712. According to the initial value of the low-pressure bypass inlet steam pressure and the designed steam temperature at the low-pressure bypass inlet, the steam density at the low-pressure bypass inlet and the steam enthalpy value at the low-pressure bypass inlet are determined by consulting the water and steam property calculation table and the steam enthalpy value table.

[0195] S713. Calculate the steam flow rate at the low-pressure bypass outlet according to the designed steam flow rate at the low-pressure bypass inlet, the steam enthalpy value at the low-pressure bypass outlet, the steam enthalpy value at the low-pressure bypass inlet, and the enthalpy value of the low-pressure bypass desuperheating water.

[0196] S714. Calculate the low-pressure bypass inlet steam pressure according to the low-pressure bypass outlet steam flow rate, the low-pressure bypass outlet steam density, the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam pressure initial value, the low-pressure bypass resistance coefficient and the low-pressure bypass outlet design steam pressure.

[0197] S715. Calculate a first deviation between the low-pressure bypass inlet steam pressure and the initial value of the low-pressure bypass inlet steam pressure.

[0198] S716: Determine whether the first deviation is less than a first preset deviation threshold; if so, execute S717; if not, return to execute S711.

[0199] S717. Output the low-pressure bypass inlet steam pressure and the low-pressure bypass inlet steam density, low-pressure bypass inlet steam enthalpy, and low-pressure bypass inlet steam flow rate corresponding to the low-pressure bypass inlet steam pressure.

[0200] S718. Obtain the initial value of the secondary reheater inlet steam pressure.

[0201] S719. According to the initial value of the steam pressure at the secondary reheater inlet and the design steam temperature at the secondary reheater inlet, the steam density at the secondary reheater inlet and the steam enthalpy value at the secondary reheater inlet are determined by consulting the water and steam property calculation table and the water vapor enthalpy value table.

[0202] S720. Determine the inlet design steam flow rate in the low-pressure bypass preset steam parameters as the secondary reheater inlet steam flow rate.

[0203] S721. Calculate the steam pressure at the secondary reheater inlet according to the steam density at the secondary reheater inlet, the steam flow rate at the low-pressure bypass inlet, the steam density at the low-pressure bypass inlet corresponding to the steam pressure at the low-pressure bypass inlet, the initial value of the steam pressure at the secondary reheater inlet, the resistance coefficient of the secondary reheater and the low-pressure bypass inlet pressure.

[0204] S722. Calculate a second deviation between the steam pressure at the secondary reheater inlet and the initial value of the steam pressure at the secondary reheater inlet.

[0205] S723: Determine whether the second deviation is less than a second preset deviation threshold. If so, execute S724; if not, return to execute S718.

[0206] S724. Output the secondary reheater inlet steam pressure, and the secondary reheater inlet steam density and secondary reheater inlet steam flow rate corresponding to the secondary reheater inlet steam pressure.

[0207] S725. Obtain the initial value of the medium-pressure bypass inlet steam pressure.

[0208] S726. According to the initial value of the steam pressure at the medium-pressure bypass inlet and the design steam temperature at the medium-pressure bypass inlet, the steam density at the medium-pressure bypass inlet and the steam enthalpy value at the medium-pressure bypass inlet are determined by consulting the water and steam property calculation table and the water vapor enthalpy value table.

[0209] S727. Calculate the steam flow rate at the intermediate-pressure bypass inlet according to the secondary reheater inlet steam flow rate, the intermediate-pressure bypass desuperheating water enthalpy value, the secondary reheater inlet steam enthalpy value and the intermediate-pressure bypass inlet steam enthalpy value corresponding to the secondary reheater inlet steam pressure.

[0210] S728. Calculate the steam pressure at the medium-pressure bypass inlet according to the steam density at the secondary reheater inlet, the steam flow rate at the low-pressure bypass inlet, the steam density at the low-pressure bypass inlet corresponding to the steam pressure at the low-pressure bypass inlet, the initial value of the steam pressure at the secondary reheater inlet, the resistance coefficient of the secondary reheater and the low-pressure bypass inlet pressure.

[0211] S729. Calculate a third deviation between the steam pressure at the medium-pressure bypass inlet and the initial value of the steam pressure at the medium-pressure bypass inlet.

[0212] S730, determining whether the third deviation is less than a third preset deviation threshold, if so, executing S731; if not, returning to executing S725.

[0213] S731. Output medium-pressure bypass inlet steam pressure and medium-pressure bypass inlet steam density, medium-pressure bypass inlet steam enthalpy, and medium-pressure bypass inlet steam flow rate corresponding to the medium-pressure bypass inlet steam pressure.

[0214] S732, determine whether the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, if so, execute S733; if not, return to execute S725.

[0215] S733. Calculate the medium-pressure bypass capacity based on the medium-pressure bypass inlet steam flow rate.

[0216] The technical solution provided in the embodiment of the present invention utilizes known parameters to iteratively calculate the low-pressure bypass inlet steam pressure, the secondary reheater inlet steam parameters, the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate step by step, and then calculates the medium-pressure bypass capacity. Compared with the prior art, the technical solution provided in the embodiment of the present invention provides an accurate, reasonable and scientific guiding basis for the accurate selection and configuration of the pipeline capacity of the medium-pressure bypass, solves the problem of unreasonable and inaccurate selection in the prior art, and effectively improves the rationality and accuracy of the selection of the medium-pressure bypass capacity and the safety of system operation.

[0217] Figure 8 This is a schematic diagram of the structure of a medium-pressure bypass capacity calculation device for a secondary reheat unit provided in Embodiment 3 of the present invention. Figure 8 As shown, the device includes a low-pressure bypass inlet steam pressure calculation module 810, a secondary reheater inlet steam parameter calculation module 820, a medium-pressure bypass inlet steam pressure and flow calculation module 830 and a medium-pressure bypass capacity calculation module 840.

[0218] The low-pressure bypass inlet steam pressure calculation module 810 is used to calculate the low-pressure bypass inlet steam pressure according to the low-pressure bypass preset steam parameters of the secondary reheat unit.

[0219] The secondary reheater inlet steam parameter calculation module 820 is used to calculate the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheater unit.

[0220] The medium-pressure bypass inlet steam pressure and flow calculation module 830 is used to calculate the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow according to the secondary reheater inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit.

[0221] The medium-pressure bypass capacity calculation module 840 is used to calculate the medium-pressure bypass capacity according to the medium-pressure bypass inlet steam flow when the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow meet preset conditions.

[0222] The medium-pressure bypass capacity calculation device for a secondary reheat unit provided in an embodiment of the present invention can execute the medium-pressure bypass capacity calculation method for a secondary reheat unit provided in any embodiment of the present invention, and has functional modules and beneficial effects corresponding to the execution method.

[0223] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0224] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the medium-pressure bypass capacity of a secondary reheat unit, characterized in that: include: Calculate the steam pressure at the low-pressure bypass inlet according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit; Calculating a secondary reheater inlet steam parameter according to the low-pressure bypass inlet pressure and a secondary reheater preset steam parameter of the secondary reheat unit; Calculating the steam pressure at the inlet of the medium-pressure bypass and the steam flow rate at the inlet of the medium-pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the medium-pressure bypass of the secondary reheat unit; When the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate meet preset conditions, the medium-pressure bypass capacity is calculated according to the medium-pressure bypass inlet steam flow rate.

2. The method for calculating the medium-pressure bypass capacity according to claim 1, characterized in that: The preset steam parameters of the low-pressure bypass include: low-pressure bypass outlet design steam temperature, low-pressure bypass outlet design steam pressure, low-pressure bypass inlet design steam flow, low-pressure bypass desuperheating water enthalpy value, low-pressure bypass inlet design steam temperature, and low-pressure bypass resistance coefficient; The calculation of the low-pressure bypass inlet steam pressure according to the preset steam parameters of the low-pressure bypass of the secondary reheat unit includes: According to the low-pressure bypass outlet design steam temperature and the low-pressure bypass outlet design steam pressure, by querying the water and steam property calculation table and the steam enthalpy table, the low-pressure bypass outlet steam density and the low-pressure bypass outlet steam enthalpy are determined; Obtain the initial value of the low-pressure bypass inlet steam pressure; According to the initial value of the low-pressure bypass inlet steam pressure and the designed steam temperature at the low-pressure bypass inlet, by querying the water and steam property calculation table and the steam enthalpy table, the low-pressure bypass inlet steam density and the low-pressure bypass inlet steam enthalpy are determined; Calculate the steam flow rate at the low-pressure bypass outlet according to the low-pressure bypass inlet design steam flow rate, the low-pressure bypass outlet steam enthalpy value, the low-pressure bypass inlet steam enthalpy value and the low-pressure bypass desuperheating water enthalpy value; The low-pressure bypass inlet steam pressure is calculated according to the low-pressure bypass outlet steam flow rate, the low-pressure bypass outlet steam density, the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam pressure initial value, the low-pressure bypass resistance coefficient and the low-pressure bypass outlet design steam pressure.

3. The method for calculating the medium-pressure bypass capacity according to claim 2, characterized in that: After calculating the low-pressure bypass inlet steam pressure according to the low-pressure bypass outlet steam flow, the low-pressure bypass outlet steam density, the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam pressure initial value, the low-pressure bypass resistance coefficient and the low-pressure bypass outlet design steam pressure, the method further includes: Calculating a first deviation between the low-pressure bypass inlet steam pressure and an initial value of the low-pressure bypass inlet steam pressure; Determining whether the first deviation is less than a first preset deviation threshold; When the first deviation is less than or equal to the first preset deviation threshold, outputting the low-pressure bypass inlet steam pressure and the low-pressure bypass inlet steam density, the low-pressure bypass inlet steam enthalpy, and the low-pressure bypass inlet steam flow rate corresponding to the low-pressure bypass inlet steam pressure; When the first deviation is greater than the first preset deviation threshold, the step of obtaining the initial value of the low-pressure bypass inlet steam pressure is returned to, and the calculation is continued using the low-pressure bypass inlet steam pressure as the initial value.

4. The method for calculating the medium-pressure bypass capacity according to claim 1, characterized in that: The preset steam parameters of the secondary reheater include: the secondary reheater outlet design steam temperature, the secondary reheater inlet design steam temperature and the secondary reheater resistance coefficient; The secondary reheater inlet steam parameters include: secondary reheater inlet steam pressure, secondary reheater inlet steam flow rate and secondary reheater inlet steam density; Calculating the secondary reheater inlet steam parameters according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameters of the secondary reheat unit includes: Obtain the initial value of the secondary reheater inlet steam pressure; According to the initial value of the steam pressure at the secondary reheater inlet and the designed steam temperature at the secondary reheater inlet, the steam density at the secondary reheater inlet is determined by querying a water and steam property calculation table; Determine the inlet design steam flow rate in the low-pressure bypass preset steam parameters as the inlet steam flow rate of the secondary reheater; The secondary reheater inlet steam pressure is calculated according to the secondary reheater inlet steam density, the low-pressure bypass inlet steam flow rate, the low-pressure bypass inlet steam density corresponding to the low-pressure bypass inlet steam pressure, the initial value of the secondary reheater inlet steam pressure, the secondary reheater resistance coefficient and the low-pressure bypass inlet pressure.

5. The method for calculating the medium-pressure bypass capacity according to claim 4, characterized in that: After calculating the secondary reheater inlet steam pressure according to the secondary reheater inlet steam density, the low-pressure bypass inlet steam flow rate, the low-pressure bypass inlet steam density corresponding to the low-pressure bypass inlet steam pressure, the secondary reheater inlet steam pressure initial value, the secondary reheater resistance coefficient and the low-pressure bypass inlet pressure, the further comprising: calculating a second deviation of the steam pressure at an inlet of the secondary reheater from an initial value of the steam pressure at an inlet of the secondary reheater; Determining whether the second deviation is less than a second preset deviation threshold; When the second deviation is less than or equal to the second preset deviation threshold, outputting the secondary reheater inlet steam pressure and the secondary reheater inlet steam density and the secondary reheater inlet steam flow rate corresponding to the secondary reheater inlet steam pressure; When the second deviation is greater than the second preset deviation threshold, the process returns to the step of obtaining the initial value of the secondary reheater inlet steam pressure, and continues the calculation by taking the secondary reheater inlet steam pressure as the initial value.

6. The method for calculating the medium-pressure bypass capacity according to claim 1, characterized in that: The preset steam parameters of the medium-pressure bypass include: the designed steam temperature at the outlet of the medium-pressure bypass, the enthalpy value of the medium-pressure bypass desuperheating water, the designed steam temperature at the inlet of the medium-pressure bypass, and the resistance coefficient of the medium-pressure bypass; Calculating the steam pressure at the inlet of the intermediate pressure bypass and the steam flow rate at the inlet of the intermediate pressure bypass according to the steam parameters at the inlet of the secondary reheater and the preset steam parameters of the intermediate pressure bypass of the secondary reheat unit, including: Obtain the initial value of the medium-pressure bypass inlet steam pressure; According to the initial value of the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet design steam temperature, by querying the water and steam property calculation table and the water vapor enthalpy table, the medium-pressure bypass inlet steam density and the medium-pressure bypass inlet steam enthalpy are determined; Calculate the steam flow rate at the inlet of the medium-pressure bypass according to the steam flow rate at the inlet of the secondary reheater corresponding to the steam pressure at the inlet of the secondary reheater, the enthalpy value of the medium-pressure bypass desuperheating water, the enthalpy value of the steam at the inlet of the secondary reheater and the enthalpy value of the steam at the inlet of the medium-pressure bypass; The medium-pressure bypass inlet steam pressure is calculated according to the medium-pressure bypass inlet steam density, the secondary reheater inlet steam flow rate, the secondary reheater inlet steam density, the initial value of the medium-pressure bypass inlet steam pressure, the medium-pressure bypass resistance coefficient and the secondary reheater inlet steam pressure.

7. The method for calculating the medium-pressure bypass capacity according to claim 6, characterized in that: After calculating the steam pressure at the medium-pressure bypass inlet according to the steam density at the medium-pressure bypass inlet, the steam flow rate at the secondary reheater inlet, the medium-pressure bypass resistance coefficient and the steam pressure at the secondary reheater inlet, the method further includes: Calculating a third deviation between the medium-pressure bypass inlet steam pressure and an initial value of the medium-pressure bypass inlet steam pressure; Determining whether the third deviation is less than a third preset deviation threshold; When the third deviation is less than or equal to the third preset deviation threshold, output the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam density, medium-pressure bypass inlet steam enthalpy, and medium-pressure bypass inlet steam flow rate corresponding to the medium-pressure bypass inlet steam pressure; When the third deviation is greater than the third preset deviation threshold, the process returns to the step of obtaining the initial value of the medium-pressure bypass inlet steam pressure, and continues the calculation by taking the medium-pressure bypass inlet steam pressure as the initial value.

8. The method for calculating the medium-pressure bypass capacity according to claim 1, characterized in that: When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, calculating the medium-pressure bypass capacity according to the steam flow rate at the medium-pressure bypass inlet includes: When the steam pressure at the medium-pressure bypass inlet and the steam flow rate at the medium-pressure bypass inlet meet preset conditions, converting the steam flow rate at the medium-pressure bypass inlet to the steam flow rate at the medium-pressure bypass inlet under rated steam parameters; The medium-pressure bypass capacity is calculated based on the medium-pressure bypass inlet steam flow rate under the rated steam parameters and the main steam flow rate under the maximum continuous evaporation capacity condition of the secondary reheat unit.

9. The method for calculating the medium-pressure bypass capacity according to claim 1, characterized in that: Also includes: When the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate do not meet the preset conditions, return to execute the step of calculating the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow rate based on the secondary reheater inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit.

10. A medium pressure bypass capacity calculation device for a secondary reheat unit, characterized in that: include: A low-pressure bypass inlet steam pressure calculation module, which is used to calculate the low-pressure bypass inlet steam pressure according to the low-pressure bypass preset steam parameters of the secondary reheat unit; A secondary reheater inlet steam parameter calculation module, the secondary reheater inlet steam parameter calculation module is used to calculate the secondary reheater inlet steam parameter according to the low-pressure bypass inlet pressure and the secondary reheater preset steam parameter of the secondary reheater unit; A medium-pressure bypass inlet steam pressure and flow calculation module, the medium-pressure bypass inlet steam pressure and flow calculation module is used to calculate the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow according to the secondary reheater inlet steam parameters and the medium-pressure bypass preset steam parameters of the secondary reheat unit; A medium-pressure bypass capacity calculation module is used to calculate the medium-pressure bypass capacity according to the medium-pressure bypass inlet steam flow when the medium-pressure bypass inlet steam pressure and the medium-pressure bypass inlet steam flow meet preset conditions.

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