Steam supplementing valve optimization type selection method suitable for ultra-supercritical steam turbine

Abstract

The invention discloses a steam supplementing valve optimization type selection method suitable for an ultra-supercritical steam turbine, relates to the technical field of steam turbine structure optimization, and aims at solving the problems that due to unreasonable type selection of a steam supplementing valve of an existing ultra-supercritical steam turbine with the steam supplementing valve, unit economy becomes poor, and safe operation is affected. According to the steam supplementing valve optimization type selection method suitable for the ultra-supercritical steam turbine, firstly, the steam supplementing position is determined through the ratio of the pressure behind the steam supplementing valve to the pressure before the steam supplementing valve, the temperature difference value before the steam supplementing valve and the pressure behind the steam supplementing valve and the steam supplementing flow, then the valve diameter is calculated through the pressure difference before and after the steam supplementing valve and the steam supplementing flow, and the total stroke of a valve rod is estimated; and finally, a valve flow characteristic curve of the steam supplementing valve is obtained through steam distribution, and the model selection work of the steam supplementing valve is completed. The invention mainly provides a steam supplementing valve optimization type selection method suitable for an ultra-supercritical steam turbine.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine structure optimization, and in particular to a method for optimizing the selection of a supplementary steam valve suitable for an ultra-supercritical steam turbine. Background Art

[0002] At present, operation with a supplementary steam valve is one of the mainstream operating modes of 660MW and 1000MW ultra-supercritical units. The full-cycle steam inlet with a supplementary steam valve regulation unit achieves primary frequency regulation through the supplementary steam valve technology. The main steam does not need to be throttled during unit operation. The rated operating steam inlet pressure can reach the rated pressure value, and the unit has higher operating efficiency. After the supplementary steam valve is set, unreasonable supplementary steam position will cause the supplementary steam operating efficiency to decrease. The large temperature difference before and after the supplementary steam valve will affect the safe operation of the supplementary steam valve. The unreasonable selection of the supplementary steam valve caliber and stroke will cause poor valve control characteristics, unstable flow control under small opening, valve jitter and other problems, affecting the economy and safe operation of the unit. Therefore, it is urgent to propose an optimization selection method for supplementary steam valves suitable for ultra-supercritical steam turbines to solve the above problems. Summary of the invention

[0003] The present invention aims to solve the problems of poor unit economy and safety operation caused by unreasonable selection of supplementary steam valves in existing ultra-supercritical steam turbines with supplementary steam valves, and further provides a method for optimizing the selection of supplementary steam valves for ultra-supercritical steam turbines.

[0004] A method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine is implemented by the following steps:

[0005] Step 1: Determine the steam supply position: Set the steam supply valve opening point working condition according to the working condition definition, and select the steam supply position corresponding to the minimum steam supply flow rate according to the requirements that the pressure ratio between the supply valve and the supply valve is not less than the critical pressure ratio of 0.546 and the temperature difference between the supply valve and the supply valve is not more than 70°C, and obtain the maximum steam supply flow rate;

[0006] Step 2: Determine the valve diameter: Determine the pressure before the steam supply valve, the temperature before the steam supply valve, the pressure after the steam supply valve and the maximum steam supply flow rate according to the steam supply position, and calculate the diameter of the steam supply valve using the flow calculation formula;

[0007] Step 3: Calculate the relationship curve formula of the supply steam valve flow rate and the downstream pressure: By calculating the heat balance under different supply steam conditions, the supply steam flow rate and the corresponding downstream pressure are obtained, and the relationship curve formula of the supply steam valve flow rate and the downstream pressure is calculated;

[0008] Step 4: Estimate the total valve stem stroke of the steam supply valve: When the steam supply flow reaches the maximum flow, the steam supply valve opening is set to 50% according to operating experience, that is, the effective valve stem stroke is 1 / 2 times the total valve stem stroke; according to design experience, the effective stroke is 1 / 3 times the valve diameter, so the total valve stem stroke is estimated to be 2 / 3 times the valve diameter;

[0009] Step 5: Steam distribution of the steam supply valve: Based on the calculated valve diameter of the steam supply valve, the calculated relationship curve formula of the steam supply valve flow and the downstream pressure, and the estimated total stroke of the steam supply valve stem, the steam distribution calculation of the valve is completed. Based on the steam distribution result, it is determined whether the total stroke of the steam supply valve stem estimated in step 4 is reasonable. If it is unreasonable, the total stroke of the steam supply valve stem estimated in step 4 is adjusted, and the steam distribution calculation is performed according to this step 5 until the steam distribution result matches the total stroke of the steam supply valve stem estimated in step 4.

[0010] Step 6: Draw the flow characteristic curve of the steam supply valve and determine the type of steam supply valve;

[0011] Furthermore, the specific process of determining the supplementary steam position in step 1 is as follows:

[0012] Step 1a: Set the steam supply valve opening point according to the working condition definition. The turbine high-pressure cylinder has n stages, the inlet pressure is P0, the inlet temperature is T0, and the pressures after the first stage, the second stage, ... the nth stage are P1, P2, ... P n , the temperatures after the first, second, ...nth stages are T1, T2, ...T n ;

[0013] Step 1b: Calculate the maximum steam flow rate of the steam supply valve when the steam supply position is set at the 1st stage, the 2nd stage, and the nth stage respectively. When the steam supply position is set at the 1st stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M1. When the steam supply position is set at the 2nd stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M2. When the steam supply position is set at the nth stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M n ;

[0014] Step 1c: Calculate the pressure ratios of the inlet steam valve after the inlet steam valve and before the inlet steam valve when the inlet steam position is set at the 1st stage, the 2nd stage, ... the nth stage respectively. That is, the pressure ratio of the inlet steam valve after the inlet steam valve after the first stage to the inlet steam valve before the inlet steam valve is Π1=P1 / P0, the pressure ratio of the inlet steam valve after the inlet steam valve after the second stage to the inlet steam valve before the inlet steam valve is Π2=P2 / P0... The pressure ratio of the inlet steam valve after the inlet steam valve after the nth stage to the inlet steam valve before the inlet steam valve is Π n =P n / P0;

[0015] Step 1d: Calculate the temperature difference between the inlet steam valve and the inlet steam valve when the inlet steam position is set at the 1st stage, the 2nd stage, ... the nth stage, respectively. That is, when the inlet steam position is set at the first stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt1=T0-T1, when the inlet steam position is set at the second stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt2=T0-T2... When the inlet steam position is set at the nth stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt n =T0-T n ;

[0016] Step 1e: Based on the pressure ratio Π after the steam supply valve and before the steam supply valve not being lower than the critical pressure ratio 0.546 and the temperature difference Δt before and after the steam supply valve not being greater than 70°C, select the steam supply position corresponding to the minimum steam supply flow rate and set it as the kth stage, and the pressure after the stage is P k , the temperature after the stage is T k , the supplementary steam flow is M k The pressure ratio after the steam supply valve and before the steam supply valve is Π k ;

[0017] Furthermore, the specific process of determining the valve diameter in step 2 is as follows:

[0018] According to the adiabatic index κ = 1.3 and the pressure ratio of the steam supply valve to the valve, Π k Calculate the Pentaman coefficient β:

[0019]

[0020] Calculation of critical flow rate M by using Pentaman coefficient β cr =M k *β, the specific volume v0 is calculated by the pressure P0 and temperature T0 before the steam injection valve. The valve area S can be calculated based on the specific volume v0:

[0021]

[0022] The valve diameter d can be calculated based on the valve area S:

[0023]

[0024] Furthermore, the specific process of calculating the relationship curve formula of the steam injection valve flow and the downstream pressure in step 3 is as follows:

[0025] Calculate the heat balance between the maximum steam supply flow condition and the rated condition. k The corresponding pressure after the steam supply valve is P k When the rated operating condition supplementary steam flow is 0, the corresponding pressure after the supplementary steam valve is P e , calculate the relationship curve formula between the steam injection valve flow and the pressure after the valve;

[0026] Furthermore, the specific process of estimating the total stroke of the supplementary steam valve stem in step 4 is as follows:

[0027] When the supplementary steam flow reaches the maximum flow, the supplementary steam valve opening is set to 50% according to operating experience, that is, the effective valve stem stroke is 1 / 2 times the total valve stem stroke. According to design experience, the effective stroke is 1 / 3 times the valve diameter. The total valve stem stroke is estimated to be L m =2d / 3;

[0028] Set the valve stem stroke and the corresponding valve flow: Set the valve stem stroke to L1 = 0.05L m 、L2=0.10L m 、L3=0.20L m 、L4=0.40L m 、L5=0.50L m 、L6=0.70L m 、L7=0.90L m 、L8=L m , the corresponding flow through the valve is M L1 =M k L1 / L m 、M L2 =M k L2 / L m 、M L3 =M k L3 / L m 、M L4 =M k L4 / L m 、M L5 =M k L5 / L m 、M L6 =M k L6 / L m 、M L7 =M k L7 / L m 、M L8 =M k L8 / L m ;

[0029] Furthermore, the specific process of steam distribution of the supplementary steam valve in step 5 is as follows:

[0030] According to step 4, the valve stem travel L1, L2, L3, L4, L5, L6, L7, L8 corresponding to the valve back pressure are calculated as P by using the relationship curve formula of the steam supply valve flow and valve back pressure. L1 , P L2 , P L3 , P L4 , P L5 , P L6 , P L7 , P L8 ;

[0031] The valve stem stroke corresponds to the steam supply valve opening, and the steam supply valve opening is calculated as L1 / L m , L2 / L m 、L3 / L m 、L4 / L m 、L5 / L m 、L6 / Lm 、L7 / L m 、L8 / L m The corresponding valve area S L1 , S L2 , S L3 , S L4 , S L5 , S L6 , S L7 , S L8 , respectively calculate the corresponding critical flow M crL1 =0.667*S L1 *(P0 / v0)^0.5,M crL2＝ 0.667*S L2 *(P0 / v0)^0.5,M crL3 =0.667*S L3 *(P0 / v0),M crL4 =0.667*S L4 *(P0 / v0),M crL5 =0.667*S L5 *(P0 / v0),M crL6 =0.667*S L6 *(P0 / v0),M crL7 =0.667*S L7 *(P0 / v0),M crL8 =0.667*S L8 *(P0 / v0), after-valve pressure P L1 , P L2 , P L3 , P L4 , P L5 , P L6 , P L7 , P L8 Calculate the Pentaman coefficient β L1 , β L2 , β L3 , β L4 , β L5 , β L6 , β L7 , β L8 , get the calculated valve flow rate M ’ L1 =M crL1 *β L1 , M ’ L2 =M crL2 *β L2 , M ’ L3 =M crL3 *β L3 , M ’L4 =M crL4 *β L4 , M ’ L5 =M crL5 *β L5 , M ’ L6 =M crL6 *β L6 , M ’ L7 =M crL7 *β L7 , M ’ L8 =M crL8 *β L8 ;

[0032] Valve stem stroke corresponding to flow rate M L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 Flow rate M corresponding to valve opening ’ L1 、M ’ L2 、M ’ L3 、M ’ L4 、M ’ L5 , M ’ L6 , M ’ L7 , M ’ L8 The deviations are λ1=(M ’ L1 -M L1 ) / M L1 ,λ2=(M ’ L2 -M L2 ) / M L2 ,λ3=(M ’ L3 -M L3 ) / M L3 ,λ4=(M ’ L4 -M L4 ) / M L4 ,λ5=(M ’ L5 -M L5 ) / M L5 ,λ6=(M ’L6 -M L6 ) / M L6 ,λ7=(M ’ L7 -M L7 ) / M L7 ,λ8=(M ’ L8 -M L8 ) / M L8 If -0.5%≤λ≤0.5%, the valve steam distribution is completed and step (6) is executed; if λ>0.5% or λ<-0.5%, the valve stem strokes L1, L2, L3, L4, L5, L6, L7, L8 correspond to the supplementary steam flow through the valve respectively. L1 =M ’ L1 , M L2 =M ’ L2 , M L3 =M ’ L3 , M L4 =M ’ L4 , M L5 =M ’ L5 , M L6 =M ’ L6 , M L7 =M ’ L7 , M L8 =M ’ L8 ;

[0033] Determine the total travel L of the steam supply valve stem m :According to the above steam distribution results, the valve stem travel L1, L2, L3, L4, L5, L6, L7, L8 and the corresponding steam flow M through the valve are fitted L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 The relationship curve formula is used, and the fitting formula is used to calculate the total travel L of the steam distribution valve stem corresponding to the maximum steam injection flow rate. s When the deviation value -5% ≤ θ = (L s -L m ) / L m When θ≤5%, the total valve stem stroke of the steam supply valve estimated in step 4 is considered reasonable, and step 6 is executed; when θ>5% or θ<-5%, the total valve stem stroke of the steam supply valve estimated in step 4 is considered unreasonable and needs to be adjusted. The adjustment method is as follows:

[0034] When θ>5%, let L m =(1+5%)*2d / 3, repeat steps 4 and 5;

[0035] When θ<-5%, let L m =(1-5%)*2d / 3, repeat steps 4 and 5;

[0036] Furthermore, the specific process of drawing the flow characteristic curve of the steam supply valve and determining the type of the steam supply valve in step 6 is as follows: according to the above-mentioned valve stem strokes L1, L2, L3, L4, L5, L6, L7, L8 and the corresponding flow rate M passing through the valve L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 Draw the flow characteristic curve of the steam supply valve. According to the total travel L of the steam supply valve stem determined in step 5, m , and carry out corresponding steam supply valve selection work.

[0037] The beneficial effects of this application compared to the prior art are as follows:

[0038] 1. This application proposes a method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine, which can effectively solve the problem of confusion and non-standard selection of supplementary steam valves;

[0039] 2. This application proposes a method for optimizing the selection of a steam supply valve suitable for an ultra-supercritical steam turbine. The optimized characteristic curve of the selected steam supply valve can ensure that the opening of the steam supply valve is reasonable and the adjustability is good during the operation of the unit, avoiding the problems of small valve opening under small flow and frequent collision of the valve disc with the valve seat, solving the problem that the steam supply valve cannot be opened normally during actual operation, and improving the safe operation stability of the unit.

[0040] 3. This application proposes a method for optimizing the selection of a supplementary steam valve suitable for an ultra-supercritical steam turbine. By optimizing the supplementary steam position, the supplementary steam loss is reduced, the economy of the supplementary steam condition is improved, and the heat rate is reduced by 6 to 18 kJ / kW.h. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flow chart of a method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine as described in this application;

[0042] Figure 2 This is a characteristic curve diagram of the valve stem stroke and valve flow rate of the steam supplementary valve in step 6 described in this application. DETAILED DESCRIPTION

[0043] Specific implementation method 1: Combination Figure 1 to Figure 2 This embodiment is described. In this embodiment, a method for optimizing the selection of a supplementary steam valve applicable to an ultra-supercritical steam turbine is provided. The method is implemented by the following steps:

[0044] Step 1: Determine the steam supply position: Set the steam supply valve opening point working condition according to the working condition definition, and select the steam supply position corresponding to the minimum steam supply flow rate according to the requirements that the pressure ratio between the supply valve and the supply valve is not less than the critical pressure ratio of 0.546 and the temperature difference between the supply valve and the supply valve is not more than 70°C, and obtain the maximum steam supply flow rate;

[0045] Step 2: Determine the valve diameter: Determine the pressure before the steam supply valve, the temperature before the steam supply valve, the pressure after the steam supply valve and the maximum steam supply flow rate according to the steam supply position, and calculate the diameter of the steam supply valve using the flow calculation formula;

[0046] Step 3: Calculate the relationship curve formula of the supply steam valve flow rate and the downstream pressure: By calculating the heat balance under different supply steam conditions, the supply steam flow rate and the corresponding downstream pressure are obtained, and the relationship curve formula of the supply steam valve flow rate and the downstream pressure is calculated;

[0047] Step 4: Estimate the total valve stem stroke of the steam supply valve: When the steam supply flow reaches the maximum flow, the steam supply valve opening is set to 50% according to operating experience, that is, the effective valve stem stroke is 1 / 2 times the total valve stem stroke; according to design experience, the effective stroke is 1 / 3 times the valve diameter, so the total valve stem stroke is estimated to be 2 / 3 times the valve diameter;

[0048] Step 5: Steam distribution of the steam supply valve: Based on the calculated valve diameter of the steam supply valve, the calculated relationship curve formula of the steam supply valve flow and the downstream pressure, and the estimated total stroke of the steam supply valve stem, the steam distribution calculation of the valve is completed. Based on the steam distribution result, it is determined whether the total stroke of the steam supply valve stem estimated in step 4 is reasonable. If it is unreasonable, the total stroke of the steam supply valve stem estimated in step 4 is adjusted, and the steam distribution calculation is performed according to this step 5 until the steam distribution result matches the total stroke of the steam supply valve stem estimated in step 4.

[0049] Step 6: Draw the flow characteristic curve of the steam supply valve and determine the type of steam supply valve.

[0050] In this embodiment and the following embodiments, the pressure P is in MPa, the temperature T is in °C, and the specific volume v is in m 3 / kg, flow rate M is in t / h, diameter d is in cm, area S is in cm 2 , the valve stem stroke L is in cm;

[0051] The present embodiment proposes a method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine. The supplementary steam position is first determined by the pressure ratio between the front and rear pressures of the supplementary steam valve, the temperature difference between the front and rear pressures of the supplementary steam valve, and the supplementary steam flow rate. The valve diameter is then calculated by the pressure difference before and after the supplementary steam valve and the supplementary steam flow rate, and the total valve stem stroke is estimated. Finally, the flow characteristic curve of the supplementary steam valve is obtained by steam distribution, and the selection of the supplementary steam valve is completed.

[0052] Specific implementation method 2: Combination Figure 1 to Figure 2 This embodiment is described. The difference between this embodiment and the first embodiment is that the specific process of determining the supplementary steam position in step 1 is as follows:

[0053] Step 1a: Set the steam supply valve opening point according to the working condition definition. The turbine high-pressure cylinder has n stages, the inlet pressure is P0, the inlet temperature is T0, and the pressures after the first stage, the second stage, ... the nth stage are P1, P2, ... P n , the temperatures after the first, second, ...nth stages are T1, T2, ...T n ;

[0054] Step 1b: Calculate the maximum steam flow rate of the steam supply valve when the steam supply position is set at the 1st stage, the 2nd stage, and the nth stage respectively. When the steam supply position is set at the 1st stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M1. When the steam supply position is set at the 2nd stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M2. When the steam supply position is set at the nth stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M n ;

[0055] Step 1c: Calculate the pressure ratios of the inlet steam valve after the inlet steam valve and before the inlet steam valve when the inlet steam position is set at the 1st stage, the 2nd stage, ... the nth stage respectively. That is, the pressure ratio of the inlet steam valve after the inlet steam valve after the first stage to the inlet steam valve before the inlet steam valve is Π1=P1 / P0, the pressure ratio of the inlet steam valve after the inlet steam valve after the second stage to the inlet steam valve before the inlet steam valve is Π2=P2 / P0... The pressure ratio of the inlet steam valve after the inlet steam valve after the nth stage to the inlet steam valve before the inlet steam valve is Π n =P n / P0;

[0056] Step 1d: Calculate the temperature difference between the inlet steam valve and the inlet steam valve when the inlet steam position is set at the 1st stage, the 2nd stage, ... the nth stage, respectively. That is, when the inlet steam position is set at the first stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt1=T0-T1, when the inlet steam position is set at the second stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt2=T0-T2... When the inlet steam position is set at the nth stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt n =T0-T n ;

[0057] Step 1e: Based on the pressure ratio Π after the steam supply valve and before the steam supply valve not being lower than the critical pressure ratio 0.546 and the temperature difference Δt before and after the steam supply valve not being greater than 70°C, select the steam supply position corresponding to the minimum steam supply flow rate and set it as the kth stage, and the pressure after the stage is P k , the temperature after the stage is T k , the supplementary steam flow is M k The pressure ratio after the steam supply valve and before the steam supply valve is Π k The other components and connection methods are the same as those in the first embodiment.

[0058] Specific implementation method three: Combination Figure 1 to Figure 2 This embodiment is described. The difference between this embodiment and the third embodiment is that the specific process of determining the valve diameter in step 2 is as follows:

[0059] According to the adiabatic index κ = 1.3 and the pressure ratio of the steam supply valve to the valve, Π k Calculate the Pentaman coefficient β:

[0060]

[0061] Calculation of critical flow rate M by using Pentaman coefficient β cr =M k *β, the specific volume v0 is calculated by the pressure P0 and temperature T0 before the steam injection valve. The valve area S can be calculated based on the specific volume v0:

[0062]

[0063] The valve diameter d can be calculated based on the valve area S:

[0064]

[0065] Other components and connection methods are the same as those in the third specific implementation method.

[0066] Specific implementation method four: Combination Figure 1 to Figure 2 The present embodiment is described. The difference between the present embodiment and the third embodiment is that the specific process of calculating the relationship curve formula of the supplementary steam valve flow rate and the downstream pressure in step 3 is as follows: Calculate the heat balance of the maximum supplementary steam flow rate condition and the rated condition. k The corresponding pressure after the steam supply valve is P k When the rated operating condition supplementary steam flow is 0, the corresponding pressure after the supplementary steam valve is P e , calculate the relationship curve formula of the steam supplement valve flow and the pressure after the valve. Other components and connection methods are the same as those of the specific implementation method four.

[0067] Specific implementation method five: Combination Figure 1 to Figure 2The present embodiment is described. The present embodiment is different from the specific embodiment 5 in that the specific process of estimating the total stroke of the valve stem of the supplementary steam valve in step 4 is as follows: when the supplementary steam flow rate reaches the maximum flow rate, the opening of the supplementary steam valve is set to 50% according to the operating experience, that is, the effective stroke of the valve stem is 1 / 2 times the total stroke of the valve stem. According to the design experience, the effective stroke is 1 / 3 times the valve diameter. The total stroke of the valve stem is estimated to be L m =2d / 3;

[0068] Set the valve stem stroke and the corresponding valve flow: Set the valve stem stroke to L1 = 0.05L m 、L2=0.10L m 、L3=0.20L m 、L4=0.40L m 、L5=0.50L m 、L6=0.70L m 、L7=0.90L m 、L8=L m , the corresponding flow through the valve is M L1 =M k L1 / L m 、M L2 =M k L2 / L m 、M L3 =M k L3 / L m 、M L4 =M k L4 / L m 、M L5 =M k L5 / L m 、M L6 =M k L6 / L m 、M L7 =M k L7 / L m 、M L8 =M k L8 / L m The other components and connection methods are the same as those of the fifth embodiment.

[0069] Specific implementation method six: Combination Figure 1 to Figure 2 This embodiment is described. The difference between this embodiment and the sixth embodiment is that the specific process of the steam supply valve in step 5 is as follows:

[0070] According to step 4, the valve stem travel L1, L2, L3, L4, L5, L6, L7, L8 corresponding to the valve back pressure are calculated as P by using the relationship curve formula of the steam supply valve flow and valve back pressure. L1 , P L2 , PL3 , P L4 , P L5 , P L6 , P L7 , P L8 ;

[0071] The valve stem stroke corresponds to the steam supply valve opening, and the steam supply valve opening is calculated as L1 / L m , L2 / L m 、L3 / L m 、L4 / L m 、L5 / L m 、L6 / L m 、L7 / L m 、L8 / L m The corresponding valve area S L1 , S L2 , S L3 , S L4 , S L5 , S L6 , S L7 , S L8 , respectively calculate the corresponding critical flow M crL1 =0.667*S L1 *(P0 / v0)^0.5,M crL2＝ 0.667*S L2 *(P0 / v0)^0.5,M crL3 =0.667*S L3 *(P0 / v0),M crL4 =0.667*S L4 *(P0 / v0),M crL5 =0.667*S L5 *(P0 / v0),M crL6 =0.667*S L6 *(P0 / v0),M crL7 =0.667*S L7 *(P0 / v0),M crL8 =0.667*S L8 *(P0 / v0), after-valve pressure P L1 , P L2 , P L3 , P L4 , P L5 , P L6 , P L7 , P L8 Calculate the Pentaman coefficient β L1 , β L2 , β L3 , β L4 , β L5 , β L6, β L7 , β L8 , get the calculated valve flow rate M ’ L1 =M crL1 *β L1 , M ’ L2 =M crL2 *β L2 , M ’ L3 =M crL3 *β L3 , M ’ L4 =M crL4 *β L4 , M ’ L5 =M crL5 *β L5 , M ’ L6 =M crL6 *β L6 , M ’ L7 =M crL7 *β L7 , M ’ L8 =M crL8 *β L8 ;

[0072] Valve stem stroke corresponding to flow rate M L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 Flow rate M corresponding to valve opening ’ L1 、M ’ L2 、M ’ L3 、M ’ L4 、M ’ L5 , M ’ L6 , M ’ L7 , M ’ L8 The deviations are λ1=(M ’ L1 -M L1 ) / M L1 ,λ2=(M ’ L2 -ML2 ) / M L2 ,λ3=(M ’ L3 -M L3 ) / M L3 ,λ4=(M ’ L4 -M L4 ) / M L4 ,λ5=(M ’ L5 -M L5 ) / M L5 ,λ6=(M ’ L6 -M L6 ) / M L6 ,λ7=(M ’ L7 -M L7 ) / M L7 ,λ8=(M ’ L8 -M L8 ) / M L8 If -0.5%≤λ≤0.5%, the valve steam distribution is completed and step (6) is executed; if λ>0.5% or λ<-0.5%, the valve stem strokes L1, L2, L3, L4, L5, L6, L7, L8 correspond to the supplementary steam flow through the valve respectively. L1 =M ’ L1 , M L2 =M ’ L2 , M L3 =M ’ L3 , M L4 =M ’ L4 , M L5 =M ’ L5 , M L6 =M ’ L6 , M L7 =M ’ L7 , M L8 =M ’ L8 ;

[0073] Determine the total travel L of the steam supply valve stem m :According to the above steam distribution results, the valve stem travel L1, L2, L3, L4, L5, L6, L7, L8 and the corresponding steam flow M through the valve are fitted L1 、M L2 、M L3 、M L4 、ML5 、M L6 、M L7 、M L8 The relationship curve formula is used, and the fitting formula is used to calculate the total travel L of the steam distribution valve stem corresponding to the maximum steam injection flow rate. s When the deviation value -5% ≤ θ = (L s -L m ) / L m When θ≤5%, the total valve stem stroke of the steam supply valve estimated in step 4 is considered reasonable, and step 6 is executed; when θ>5% or θ<-5%, the total valve stem stroke of the steam supply valve estimated in step 4 is considered unreasonable and needs to be adjusted. The adjustment method is as follows:

[0074] When θ>5%, let L m =(1+5%)*2d / 3, repeat steps 4 and 5;

[0075] When θ<-5%, let L m =(1-5%)*2d / 3, repeat step 4 and step 5. Other components and connection methods are the same as those in the sixth embodiment.

[0076] Specific implementation method seven: Combination Figure 1 to Figure 2 This embodiment is described. The difference between this embodiment and the sixth embodiment is that the specific process of drawing the flow characteristic curve of the steam supply valve and determining the type of the steam supply valve in step 6 is as follows:

[0077] According to the above-mentioned valve stem strokes L1, L2, L3, L4, L5, L6, L7, L8 and the corresponding flow rate M through the valve L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 Draw the flow characteristic curve of the steam supply valve. According to the total travel L of the steam supply valve stem determined in step 5, m , and carry out the corresponding steam supply valve selection work. Other components and connection methods are the same as those of the specific implementation method six.

[0078] The present invention has been disclosed as above with preferred implementation cases, but it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent implementation cases with equivalent changes by using the above-disclosed structures and technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above implementation cases based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine, characterized in that: The method is achieved by the following steps: Step 1: Determine the steam supply position: Set the steam supply valve opening point working condition according to the working condition definition, and select the steam supply position corresponding to the minimum steam supply flow rate according to the requirements that the pressure ratio between the supply valve and the supply valve is not less than the critical pressure ratio of 0.546 and the temperature difference between the supply valve and the supply valve is not more than 70°C, and obtain the maximum steam supply flow rate; Step 2: Determine the valve diameter: Determine the pressure before the steam supply valve, the temperature before the steam supply valve, the pressure after the steam supply valve and the maximum steam supply flow rate according to the steam supply position, and calculate the diameter of the steam supply valve using the flow calculation formula; Step 3: Calculate the relationship curve formula of the supply steam valve flow rate and the downstream pressure: By calculating the heat balance under different supply steam conditions, the supply steam flow rate and the corresponding downstream pressure are obtained, and the relationship curve formula of the supply steam valve flow rate and the downstream pressure is calculated; Step 4: Estimate the total valve stem stroke of the steam supply valve: When the steam supply flow reaches the maximum flow, the steam supply valve opening is set to 50% according to operating experience, that is, the effective valve stem stroke is 1 / 2 times the total valve stem stroke; according to design experience, the effective stroke is 1 / 3 times the valve diameter, so the total valve stem stroke is estimated to be 2 / 3 times the valve diameter; Step 5: Steam distribution of the steam supply valve: Based on the calculated valve diameter of the steam supply valve, the calculated relationship curve formula of the steam supply valve flow and the downstream pressure, and the estimated total stroke of the steam supply valve stem, the steam distribution calculation of the valve is completed. Based on the steam distribution result, it is determined whether the total stroke of the steam supply valve stem estimated in step 4 is reasonable. If it is unreasonable, the total stroke of the steam supply valve stem estimated in step 4 is adjusted, and the steam distribution calculation is performed according to step 5 again until the steam distribution result matches the total stroke of the steam supply valve stem estimated in step 4. Step 6: Draw the flow characteristic curve of the steam supply valve and determine the type of steam supply valve.

2. The method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine according to claim 1, characterized in that: The specific process of determining the admission steam position in step 1 is as follows: Step 1a: Set the steam supply valve opening point according to the working condition definition. The turbine high-pressure cylinder has n stages, the inlet pressure is P0, the inlet temperature is T0, and the pressures after the first stage, the second stage, ... the nth stage are P1, P2, ... P n , the temperatures after the first, second, ...nth stages are T1, T2, ...T n ; Step 1b: Calculate the maximum steam flow rate of the steam supply valve when the steam supply position is set at the 1st stage, the 2nd stage, and the nth stage respectively. When the steam supply position is set at the 1st stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M1. When the steam supply position is set at the 2nd stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M2. When the steam supply position is set at the nth stage, the maximum flow rate of the steam supply valve passing through the steam supply valve is M n ; Step 1c: Calculate the pressure ratios of the inlet steam valve after the inlet steam valve and before the inlet steam valve when the inlet steam position is set at the 1st stage, the 2nd stage, ... the nth stage respectively. That is, the pressure ratio of the inlet steam valve after the inlet steam valve after the first stage to the inlet steam valve before the inlet steam valve is Π1=P1 / P0, the pressure ratio of the inlet steam valve after the inlet steam valve after the second stage to the inlet steam valve before the inlet steam valve is Π2=P2 / P0... The pressure ratio of the inlet steam valve after the inlet steam valve after the nth stage to the inlet steam valve before the inlet steam valve is Π n =P n / P0; Step 1d: Calculate the temperature difference between the inlet steam valve and the inlet steam valve when the inlet steam position is set at the 1st stage, the 2nd stage, ... the nth stage, respectively. That is, when the inlet steam position is set at the first stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt1=T0-T1, when the inlet steam position is set at the second stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt2=T0-T2... When the inlet steam position is set at the nth stage, the temperature difference between the inlet steam valve and the inlet steam valve is Δt n =T0-T n ; Step 1e: Based on the pressure ratio Π after the steam supply valve and before the steam supply valve not being lower than the critical pressure ratio 0.546 and the temperature difference Δt before and after the steam supply valve not being greater than 70°C, select the steam supply position corresponding to the minimum steam supply flow rate and set it as the kth stage, and the pressure after the stage is P k , the temperature after the stage is T k , the supplementary steam flow is M k The pressure ratio after the steam supply valve and before the steam supply valve is Π k .

3. The method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine according to claim 2, characterized in that: The specific process of determining the valve diameter in step 2 is as follows: According to the adiabatic index κ = 1.3 and the pressure ratio of the steam supply valve to the valve, Π k Calculate the Pentaman coefficient β: Calculation of critical flow rate M by using Pentaman coefficient β cr =M k *β, the specific volume v0 is calculated by the pressure P0 and temperature T0 before the steam injection valve. The valve area S can be calculated based on the specific volume v0: The valve diameter d can be calculated based on the valve area S:

4. The method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine according to claim 3, characterized in that: The specific process of calculating the relationship curve formula of the steam injection valve flow and the downstream pressure in step 3 is as follows: Calculate the heat balance between the maximum steam supply flow condition and the rated condition. k The corresponding pressure after the steam supply valve is P k When the rated operating condition steam supply flow is 0, the corresponding pressure after the steam supply valve is P e , calculate the relationship curve formula between the steam supply valve flow and the pressure after the valve.

5. The method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine according to claim 4, characterized in that: The specific process of estimating the total travel of the steam injection valve stem in step 4 is as follows: When the supplementary steam flow reaches the maximum flow, the supplementary steam valve opening is set to 50% according to operating experience, that is, the effective valve stem stroke is 1 / 2 times the total valve stem stroke. According to design experience, the effective stroke is 1 / 3 times the valve diameter. The total valve stem stroke is estimated to be L m =2d / 3; Set the valve stem stroke and the corresponding valve flow: Set the valve stem stroke to L1 = 0.05L m 、L2=0.10L m 、L3=0.20L m 、L4=0.40L m 、L5=0.50L m 、L6=0.70L m 、L7=0.90L m 、L8=L m , the corresponding flow through the valve is M L1 =M k L1 / L m 、M L2 =M k L2 / L m 、M L3 =M k L3 / L m 、M L4 =M k L4 / L m 、M L5 =M k L5 / L m 、M L6 =M k L6 / L m 、M L7 =M k L7 / L m 、M L8 =M k L8 / L m .

6. The method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine according to claim 5, characterized in that: The specific process of steam distribution of the steam supply valve in step 5 is as follows: According to step 4, the valve stem travel L1, L2, L3, L4, L5, L6, L7, L8 corresponding to the valve back pressure are calculated as P by using the relationship curve formula of the steam supply valve flow and valve back pressure. L1 , P L2 , P L3 , P L4 , P L5 , P L6 , P L7 , P L8 ; The valve stem stroke corresponds to the steam supply valve opening, and the steam supply valve opening is calculated as L1 / L m , L2 / L m 、L3 / L m 、L4 / L m 、L5 / L m 、L6 / L m 、L7 / L m 、L8 / L m The corresponding valve area S L1 , S L2 , S L3 , S L4 , S L5 , S L6 , S L7 , S L8 , respectively calculate the corresponding critical flow M crL1 =0.667*S L1 *(P0 / v0)^0.5,M crL2＝ 0.667*S L2 *(P0 / v0)^0.5,M crL3 =0.667*S L3 *(P0 / v0)^0.5,M crL4 =0.667*S L4 *(P0 / v0)^0.5,M crL5 =0.667*S L5 *(P0 / v0)^0.5,M crL6 =0.667*S L6 *(P0 / v0)^0.5,M crL7 =0.667*S L7 *(P0 / v0)^0.5,M crL8 =0.667*S L8 *(P0 / v0)^0.5, after-valve pressure P L1 , P L2 , P L3 , P L4 , P L5 , P L6 , P L7 , P L8 Calculate the Pentaman coefficient β L1 , β L2 , β L3 , β L4 , β L5 , β L6 , β L7 , β L8 , get the calculated valve flow rate M ’ L1 =M crL1 *β L1 ,M ’ L2 =M crL2 *b L2 ,M ’ L3 =M crL3 *b L3 ,M ’ L4 =M crL4 *b L4 ,M ’ L5 =M crL5 *b L5 ,M ’ L6 =M crL6 *b L6 ,M ’ L7 =M crL7 *b L7 ,M ’ L8 =M crL8 *b L8 ; Valve stem stroke corresponding to flow rate M L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 Flow rate M corresponding to valve opening ’ L1 、M ’ L2 、M ’ L3 、M ’ L4 、M ’ L5 , M ’ L6 , M ’ L7 , M ’ L8 The deviations are λ1=(M ’ L1 -M L1 ) / M L1 ,λ2=(M ’ L2 -M L2 ) / M L2 ,λ3=(M ’ L3 -M L3 ) / M L3 ,λ4=(M ’ L4 -M L4 ) / M L4 ,λ5=(M ’ L5 -M L5 ) / M L5 ,λ6=(M ’ L6 -M L6 ) / M L6 ,λ7=(M ’ L7 -M L7 ) / M L7 ,λ8=(M ’ L8 -M L8 ) / M L8 If -0.5%≤λ≤0.5%, the valve steam distribution is completed and step (6) is executed; if λ>0.5% or λ<-0.5%, the valve stem strokes L1, L2, L3, L4, L5, L6, L7, L8 correspond to the supplementary steam flow through the valve respectively. L1 =M ’ L1 ,M L2 =M ’ L2 ,M L3 =M ’ L3 ,M L4 =M ’ L4 ,M L5 =M ’ L5 ,M L6 =M ’ L6 ,M L7 =M ’ L7 ,M L8 =M ’ L8 ; Determine the total travel L of the steam supply valve stem m :According to the above steam distribution results, the valve stem travel L1, L2, L3, L4, L5, L6, L7, L8 and the corresponding steam flow M through the valve are fitted L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 The relationship curve formula is used, and the fitting formula is used to calculate the total travel L of the steam distribution valve stem corresponding to the maximum steam injection flow rate. s When the deviation value -5% ≤ θ = (L s -L m ) / L m When θ≤5%, the total valve stem stroke of the steam supply valve estimated in step 4 is considered reasonable, and step 6 is executed; when θ>5% or θ<-5%, the total valve stem stroke of the steam supply valve estimated in step 4 is considered unreasonable and needs to be adjusted. The adjustment method is as follows: When θ>5%, let L m =(1+5%)*2d / 3, repeat steps 4 and 5; When θ<-5%, let L m =(1-5%)*2d / 3, repeat steps 4 and 5.

7. The method for optimizing the selection of a supplementary steam valve for an ultra-supercritical steam turbine according to claim 6, characterized in that: The specific process of drawing the flow characteristic curve of the steam supply valve and determining the type of the steam supply valve in step 6 is as follows: According to the above-mentioned valve stem strokes L1, L2, L3, L4, L5, L6, L7, L8 and the corresponding flow rate M through the valve L1 、M L2 、M L3 、M L4 、M L5 、M L6 、M L7 、M L8 Draw the flow characteristic curve of the steam supply valve. According to the total travel L of the steam supply valve stem determined in step 5, m , and carry out corresponding steam supply valve selection work.

Images