Steam turbine valve group overlapping opening optimization method comprehensively considering shafting safety and economical efficiency

Abstract

The invention discloses a steam turbine valve group overlapping opening optimization method comprehensively considering shafting safety and economy, and belongs to the technical field of steam turbines. The method solves the problem that an existing valve opening rule optimization method based on data does not consider shafting safety and turbine economy. Valve flow, regulating stage pressure, shafting vibration, bearing bush temperature and efficiency data are obtained through tests, and then a fitting function of the valve flow, the bearing bush temperature, shafting vibration and efficiency is obtained according to valve test data under different opening sequences and overlapping degrees. Meanwhile, the relation that the total flow is equal to the sum of the flows of all the valves is introduced as limitation, and the result reliability is guaranteed. Finally, safety and economical efficiency serve as comprehensive indexes, a genetic algorithm is used for conducting self-adaptive optimization on the valve opening sequence and the overlapping degree, and therefore valve opening rule self-adaptive optimization design comprehensively considering shaft system safety and economical efficiency is achieved. The method can be applied to overlapping opening optimization of the steam turbine valve group.

Description

Technical Field

[0001] The invention belongs to the technical field of steam turbines, and in particular relates to a method for optimizing the overlapping opening of a steam turbine valve group by comprehensively considering shaft system safety and economy. Background Art

[0002] In the context of the rapid development of new energy and wind power, thermal power still plays an indispensable role. The stability and technical maturity of thermal power make it an important part of the power system. In particular, in the face of the volatility and uncertainty of new energy power generation, the flexibility of thermal power is crucial to the stable operation of the power grid. Thermal power can provide fast-response peak-shaving services to cope with the intermittent and unpredictable nature of wind power and photovoltaic power generation, and ensure the balance of supply and demand in the power grid.

[0003] As a key component in the thermal power system, the turbine regulating valve plays a vital role in improving the flexibility of thermal power. On the one hand, the valve directly controls the flow of steam. Inappropriate valve opening rules may also cause valve bearing overheating and excessive shaft vibration, which in turn affects the operational safety of the steam turbine. On the other hand, the opening of the valve also affects the steam pressure and flow characteristics, which in turn affects the economic efficiency of the turbine operation. By optimizing and upgrading the valve opening rules, the response speed and operational stability of the thermal power unit can be improved, and the workmanship of the steam turbine can be improved, so that it can more effectively adapt to changes in grid demand, thereby improving the flexibility and reliability of the entire power system. Therefore, under the background of new energy wind power and dual carbon, the transformation of key technologies such as valve operation rules can provide the necessary flexibility support for the power grid.

[0004] The existing steam turbine regulating valve operation rules mainly include sequential valve opening and single valve opening. Among them, single valve is mainly used in the steam turbine startup process, and sequential valve is used more frequently during the operation of the steam turbine. Therefore, it is of great significance and practical need to optimize the sequential valve opening rule. At present, the optimization of valve opening rules can be mainly divided into experience-based methods and data-based methods. Among them, the experience-based method mainly refers to the optimization of valve opening rules by using long-term operation rules and relying on the experience of field experts or operators. This method not only requires rich field experience, but also its effectiveness is often difficult to guarantee. The main idea of ​​the data-based method is to use a large amount of historical data to fit the relationship between valve flow characteristics and opening rules, and then optimize the opening rules. The existing data-based methods often optimize the valve overlap with the linearity of flow characteristics as the optimization target. There are two main shortcomings: one is that the impact of shaft safety is not considered, and the other is that the impact of valves on the economy of steam turbines is not considered.

[0005] The valve opening directly controls the steam flow, which will affect the throttling loss of the regulating valve on the one hand, resulting in the loss of the turbine's workability; on the other hand, unreasonable opening rules may cause excessive shaft vibration, bearing overheating and other problems, resulting in reduced turbine operation reliability. Safety and economic indicators are strongly nonlinear with the valve opening rules, and it is difficult to directly optimize them through experience or manual calculation. Therefore, it is urgent to introduce an optimization algorithm to develop an optimization method for overlapping opening of turbine valve groups that comprehensively considers shaft safety and operation economy. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the existing data-based valve opening law optimization method does not take into account the safety of the shaft system and the economy of the turbine, and to propose a turbine valve group overlapping opening optimization method that comprehensively considers the safety and economy of the shaft system.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a method for optimizing the overlapping opening of a steam turbine valve group taking into account the safety and economy of the shaft system, the method specifically comprising the following steps:

[0008] Step 1: Set various opening schemes of the steam turbine valve group, and obtain test data of the steam turbine valve group under various opening schemes at the rated main steam pressure P0;

[0009] The test data include the total steam flow G of the turbine valve group, throttling loss, regulating stage pressure P1, shaft system vibration amplitude value and bearing temperature value;

[0010] Step 2: Obtain the flow characteristics of the steam turbine valve group according to the total steam flow G and the regulating stage pressure P1, and then obtain the vibration characteristics, bearing temperature characteristics and efficiency characteristics of the steam turbine valve group according to the obtained flow characteristics, throttling loss, shaft vibration amplitude value and bearing temperature value;

[0011] Step 3: design a cost function based on the vibration characteristics, watt-temperature characteristics, and efficiency characteristics obtained in step 2;

[0012] Step 4: Using the cost function designed in step 3 as the fitness function of the genetic algorithm, the genetic algorithm is used to optimize the sequence number and overlap of the third opened valve to obtain the overlapped opening optimization result of the steam turbine valve group.

[0013] The beneficial effects of the present invention are:

[0014] The present invention first conducts a valve operation test to obtain valve flow, regulating stage pressure, shaft vibration, bearing temperature and efficiency data, and then obtains valve flow, bearing temperature, shaft vibration and efficiency fitting functions based on valve test data under different opening sequences and overlaps. Based on experience and mechanism, the valve opening sequence and overlap are simplified to improve optimization efficiency. At the same time, the relationship that the total flow is equal to the sum of the flows of each valve is introduced as a restriction to ensure the reliability of the results. Finally, with safety and economy as comprehensive indicators, a genetic algorithm is used to adaptively optimize the valve opening sequence and overlap, thereby realizing an adaptive optimization design of the valve opening law that comprehensively considers shaft safety and economy.

[0015] The method of the present invention solves the problem that the traditional optimization method only considers the linearity of the flow characteristics but ignores the safety and economy of the shaft system, ensures the safety and economy of the turbine operation, has a certain effect on improving the power regulation capability of the turbine, and therefore has a strong promotion significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the valve group and regulating stage configuration;

[0017] Figure 2 It is a schematic diagram of valve opening law;

[0018] Figure 3 It is the relationship diagram between valve overlap and shaft vibration;

[0019] Figure 4 It is the relationship between valve overlap and watt temperature;

[0020] Figure 5 It is the relationship diagram between valve throttling loss and overlap;

[0021] Figure 6 This is the graph showing the change in valve tile temperature with actual flow rate;

[0022] Figure 7 It is a graph showing the change of valve shaft vibration with actual flow rate;

[0023] Figure 8 It is the watt temperature characteristic diagram;

[0024] Fig. 9 It is the shaft vibration characteristic diagram. DETAILED DESCRIPTION

[0025] Specific implementation method 1: This implementation method is a method for optimizing the overlapping opening of a steam turbine valve group that comprehensively considers shaft system safety and economy. The method specifically includes the following steps:

[0026] Step 1: Set various opening schemes of the steam turbine valve group, and obtain test data of the steam turbine valve group under various opening schemes at the rated main steam pressure P0;

[0027] The test data include the total steam flow G of the turbine valve group, throttling loss, regulating stage pressure P1, shaft system vibration amplitude value and bearing temperature value;

[0028] Step 2: Obtain the flow characteristics of the steam turbine valve group according to the total steam flow G and the regulating stage pressure P1, and then obtain the vibration characteristics, bearing temperature characteristics and efficiency characteristics of the steam turbine valve group according to the obtained flow characteristics, throttling loss, shaft vibration amplitude value and bearing temperature value;

[0029] Step 3: design a cost function based on the vibration characteristics, watt-temperature characteristics, and efficiency characteristics obtained in step 2;

[0030] Step 4: Using the cost function designed in step 3 as the fitness function of the genetic algorithm, the genetic algorithm is used to optimize the sequence number and overlap of the third opened valve to obtain the overlapped opening optimization result of the steam turbine valve group.

[0031] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the position distribution of each valve in the steam turbine valve group is specifically as follows:

[0032] After dividing the two-dimensional plane where the turbine valve group is located into four quadrants, a valve is arranged on the angular bisector of each quadrant, and the valve in the first quadrant is recorded as valve 1, the valve in the second quadrant is recorded as valve 2, the valve in the third quadrant is recorded as valve 3, and the valve in the fourth quadrant is recorded as valve 4; and the distance between each valve and the origin of the two-dimensional plane (that is, the coordinate origin based on which the quadrants are divided) is the same.

[0033] The other steps and parameters are the same as those in the first embodiment.

[0034] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that the various opening schemes of the steam turbine valve group are:

[0035] (1) First open valve 1 and valve 3, and then open valve 2 after valve 1 and valve 3 are fully opened. The opening scheme of valve 4 is:

[0036] When valve 2 is opened to 25%, open valve 4;

[0037] When valve 2 is opened to 50%, open valve 4;

[0038] When valve 2 is opened to 75%, open valve 4;

[0039] When valve 2 is fully opened, open valve 4;

[0040] (2) First open valve 1 and valve 3, and then open valve 4 after valve 1 and valve 3 are fully opened. The opening scheme of valve 2 is:

[0041] When valve 4 is opened to 25%, open valve 2;

[0042] When valve 4 is opened to 50%, open valve 2;

[0043] When valve 4 is opened to 75%, open valve 2;

[0044] When valve 4 is fully opened, open valve 2;

[0045] (3) First open valve 2 and valve 4, and then open valve 1 after valve 2 and valve 4 are fully opened. The opening scheme of valve 3 is:

[0046] When valve 1 is opened to 25%, open valve 3;

[0047] When valve 1 is opened to 50%, open valve 3;

[0048] When valve 1 is opened to 75%, open valve 3;

[0049] When valve 1 is fully opened, open valve 3;

[0050] (4) First open valve 2 and valve 4, and then open valve 3 after valve 2 and valve 4 are fully opened. The opening scheme of valve 1 is:

[0051] When valve 3 is opened to 25%, open valve 1;

[0052] When valve 3 is opened to 50%, open valve 1;

[0053] When valve 3 is opened to 75%, open valve 1;

[0054] When valve 3 is fully opened, open valve 1;

[0055] That is, a total of 16 valve opening schemes are obtained in (1) to (4).

[0056] The other steps and parameters are the same as those in the first or second embodiment.

[0057] Specific implementation method 4: This implementation method is different from any one of the specific implementation methods 1 to 3 in that the flow characteristic of the steam turbine valve group is obtained in the following manner:

[0058] Steam flow rate G of valve i in the turbine valve group i for:

[0059]

[0060] Among them, f(·) is the fitting function, ε is the pressure ratio before and after the valve, z i is the opening of valve i;

[0061] The specific form of the fitting function f(·) is:

[0062] f(z i ,P1)=a1z i 2 +a2P1 2 +a3z i +a4P1+b

[0063] The function f(·) is fitted according to the total steam flow G and the regulating stage pressure P1 under all opening schemes, and the identification results of the coefficients a1, a2, a3, a4 and b are obtained;

[0064] And the fitting process of function f(·) satisfies the following constraints:

[0065]

[0066] The other steps and parameters are the same as those in Specific Embodiments 1 to 3.

[0067] The valve shaft vibration and bearing temperature are caused by the unbalanced force caused by the flow difference, and the flow difference and unbalanced force of each valve are unmeasurable variables. This implementation solves the flow function of each valve according to the relationship between the flow rate, pressure ratio and valve opening, realizes the flow difference calculation, and ensures the feasibility of optimization.

[0068] Specific implementation method 5: This implementation method is different from the specific implementation methods 1 to 4 in that the opening z of the valve i is i The calculation method is:

[0069] Taking valve 1 as an example, the opening of valve 2 z2 and valve 4 z4 are:

[0070] z2=z4=[1%…100%…100%…100%…100%]

[0071] The opening z1 of valve 1 is:

[0072] z1=[0%…1%…100%-c…100%…100%]

[0073] Where c is the overlap between the third opened valve and the fourth opened valve;

[0074] The opening z3 of valve 3 is:

[0075] z3=[0%...0%...1%...c+1%...100%].

[0076] The other steps and parameters are the same as those in Specific Embodiments 1 to 4.

[0077] Specific implementation method 6: This implementation method is different from any one of the specific implementation methods 1 to 5 in that the vibration characteristics, tile temperature characteristics and efficiency characteristics of the steam turbine valve group are obtained in the following manner:

[0078] For example, the third valve to be opened is valve n.

[0079] For any set of tests where the third opened valve is valve n, the steam flow rate of the third opened valve and the steam flow rate of the fourth opened valve are obtained according to the fitting result of the function f(·), and the steam flow rate of the third opened valve is subtracted from the steam flow rate of the fourth opened valve, and the flow difference result is recorded as ΔG;

[0080] Similarly, the flow difference results corresponding to each group of tests under the condition that the third opened valve is valve n are obtained;

[0081] Then, the difference between the shaft vibration amplitude and flow rate when the third valve opened is valve n is fitted to obtain the vibration characteristics when the third valve opened is n:

[0082] SV n =f 1,n (ΔG)

[0083] Among them, SV n is the shaft vibration amplitude value when the third valve is opened, 1,n (·) is the fitting function;

[0084] Then, the bearing temperature value and flow rate when the third opened valve is valve n are fitted to obtain the bearing temperature characteristics when the third opened valve is valve n:

[0085] T n =f 2,n (ΔG)

[0086] Among them, T n is the bearing temperature value when the third open valve is n, f 2,n (·) is the fitting function;

[0087] Then, the throttling loss and flow rate when the third valve opened is valve n are fitted to obtain the efficiency characteristics when the third valve opened is n:

[0088] η n =f 3,n (ΔG)

[0089] Among them, η n It is the throttling loss when the third valve opened is n.

[0090] The other steps and parameters are the same as those in Specific Implementation Methods 1 to 5.

[0091] The valve opening sequence does not affect the valve flow relationship, but it will affect the valve flow difference and thus affect the reference value of the unbalanced air flow force. Therefore, the method of the present invention takes the valve opening sequence as a premise and obtains the shaft system safety index relationship under different opening sequences.

[0092] Specific implementation method 7: This implementation method is different from the specific implementation methods 1 to 6 in that the specific process of step 3 is as follows:

[0093] For example, the third valve to be opened is valve n.

[0094] J n =K1SV n +K2T n +K3(1-η n )

[0095] Among them, J n is the total cost, K1, K2 and K3 represent weights.

[0096] The other steps and parameters are the same as those in Specific Embodiments 1 to 6.

[0097] Specific implementation eight: This implementation differs from any one of specific implementations one to seven in that the specific process of step four is as follows:

[0098] Step 41: Initialize the maximum number of iterations of the genetic algorithm to L and the number of populations to M;

[0099] Step 42: Initialize the third opened valve number n=1;

[0100] Step 43: Generate initial population P(0) = {X 0,1 ,X 0,2 ,…,X 0,M}, where X 0,1 is the overlap corresponding to the first individual in the initial population, X 0,2 is the overlap corresponding to the second individual in the initial population, X 0,M is the overlap corresponding to the Mth individual in the initial population;

[0101] Step 44, initialize the number of iterations l = 0;

[0102] Step 4: Calculate the four valve openings corresponding to the mth individual according to the overlap corresponding to the mth individual in the lth generation population, and then calculate the fitness function value J of the mth individual according to the four valve openings corresponding to the mth individual. n,l,m ;

[0103] Step 46: Determine whether the iteration stop condition is met;

[0104] If it is satisfied, the iteration is stopped, and the overlap corresponding to the minimum fitness function value obtained in the last iteration is used as the optimized overlap when the third opened valve number is n; and step 47 is continued;

[0105] If it is not satisfied, select, crossover and mutate according to the calculated fitness function values ​​of each individual to generate a new population {X l+1,1 ,X l+1,2 ,…,X l+1,M}, where X l+1,1 is the overlap corresponding to the first individual in the l+1 generation population, X l+1,2 is the overlap corresponding to the second individual in the l+1 generation population, X l+1,M is the overlap corresponding to the Mth individual in the l+1th generation population; let l=l+1, and return to step 4 and 5;

[0106] Step 47: Is n equal to 4?

[0107] If n is equal to 4, execute step 48;

[0108] If n is not equal to 4, set n=n+1 and return to step 43;

[0109] Step 48, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 1 as J1′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 2 as J2′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 3 as J3′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 4 as J4′, then select the minimum value from J1′, J2′, J3′ and J4′, and use the third opened valve number corresponding to the selected minimum value as the final third opened valve number, and use the optimized overlap corresponding to the selected minimum value as the final overlap.

[0110] The other steps and parameters are the same as those in Specific Embodiments 1 to 7.

[0111] This implementation method simplifies the optimization of valve opening sequence into the optimization of the third open valve, which improves the optimization efficiency. Finally, with safety and economy as comprehensive indicators, the genetic algorithm is used to adaptively optimize the valve opening sequence and overlap, thereby realizing the adaptive optimization design of the valve opening law that comprehensively considers the safety and economy of the shaft system.

[0112] Specific implementation method 9: This implementation method is different from any one of specific implementation methods 1 to 8 in that the iteration stop condition in step 46 is to satisfy the following condition ① or ②:

[0113] Condition ①: Reach the maximum number of iterations L;

[0114] Condition ②: The minimum fitness function value obtained in the current iteration is less than the set threshold.

[0115] The other steps and parameters are the same as those in Specific Embodiments 1 to 8.

[0116] Example

[0117] Steam turbine regulating valve and regulating stage mechanical structure such as Figure 1 As shown in the figure, it can be seen that the opening of the valve affects the airflow and pressure entering the regulating stage, and further affects the work and regulating capacity of the steam turbine. Since the valves are not opened at the same time, the airflow force acting on the shaft system is asymmetric, which will cause vibration and increased bearing temperature. At the same time, when the valves are opened in sequence, it is not that one valve is fully opened before the next valve is opened, but that they are opened in an overlapping manner. Therefore, the optimization of the valve opening law requires considering both the valve opening overlap and the opening sequence.

[0118] The steam flow force on the regulating stage can be decomposed into tangential force, radial force and axial force along the circumferential direction. The radial force and axial force have little effect on the shaft system. The tangential force causes the blades to rotate and generates a flipping torque. When the air intake is uniform throughout the whole circle, the torque can be self-balanced. When the sequence is opened, the torque manifests as unbalanced air flow force and acts on each bearing to generate additional load. Therefore, the essence of shaft vibration and bearing temperature increase is the unbalanced air flow force generated by the flow difference.

[0119] Common sequence valve opening rules generally follow the diagonal opening principle, such as Figure 2 As shown, GV1 and GV3 are opened first, GV2 is opened after they are fully opened, and finally GV4 is opened. When the valves are opened in sequence, that is, the next valve is opened after the previous valve is fully opened, the flow relationship of each valve is: G1=G3>G2>>G4. The large flow difference ΔG=G2 will produce a large unbalanced air flow force ΔF=F2, causing the shaft system vibration and the bearing temperature to increase, and the safety of the shaft system is reduced.

[0120] By increasing the overlap of each valve, the flow difference of the diagonal valves can be effectively reduced, thereby reducing the unbalanced force. At this time, the flow difference of the diagonal valves is reduced to ΔG = G2-G4, and the unbalanced air flow force is also reduced to ΔF = F2-F4. The relationship between valve overlap and shaft system safety can be obtained by Figure 3 and Figure 4 shown.

[0121] Depend on Figure 2 It can be seen that increasing the overlap is an effective measure to reduce shaft vibration and bearing temperature. Overlap opening of valves will reduce the efficiency of the regulating stage and increase the throttling loss of the valve, such as Figure 5 shown.

[0122] Depend on Figure 5 It can be seen that the valve overlap cannot be increased blindly to improve the safety of the shaft system, and the economic impact must also be considered. At the same time, the valve opening sequence determines the reference value of the shaft system vibration and bearing temperature. Therefore, the optimization of the valve opening law requires comprehensive consideration of the valve opening sequence and valve overlap.

[0123] To this end, this embodiment proposes a method for optimizing the overlapping opening of a steam turbine valve group by comprehensively considering shaft system safety and economy, and the method specifically includes the following steps:

[0124] Step 1: Set various opening schemes of the steam turbine valve group, and obtain test data of the steam turbine valve group under various opening schemes at the rated main steam pressure P0;

[0125] The position distribution of each valve in the steam turbine valve group is specifically as follows: after dividing the two-dimensional plane where the steam turbine valve group is located into four quadrants, a valve is arranged on the angular bisector of each quadrant, and the valve in the first quadrant is recorded as valve 1, the valve in the second quadrant is recorded as valve 2, the valve in the third quadrant is recorded as valve 3, and the valve in the fourth quadrant is recorded as valve 4; and the distances from each valve to the origin of the two-dimensional plane are the same;

[0126] The various opening schemes of the steam turbine valve group are:

[0127] (1) First open valve 1 and valve 3, and then open valve 2 after valve 1 and valve 3 are fully opened. The opening scheme of valve 4 is:

[0128] When valve 2 is opened to 25%, open valve 4;

[0129] When valve 2 is opened to 50%, open valve 4;

[0130] When valve 2 is opened to 75%, open valve 4;

[0131] When valve 2 is fully opened, open valve 4;

[0132] (2) First open valve 1 and valve 3, and then open valve 4 after valve 1 and valve 3 are fully opened. The opening scheme of valve 2 is:

[0133] When valve 4 is opened to 25%, open valve 2;

[0134] When valve 4 is opened to 50%, open valve 2;

[0135] When valve 4 is opened to 75%, open valve 2;

[0136] When valve 4 is fully opened, open valve 2;

[0137] (3) First open valve 2 and valve 4, and then open valve 1 after valve 2 and valve 4 are fully opened. The opening scheme of valve 3 is:

[0138] When valve 1 is opened to 25%, open valve 3;

[0139] When valve 1 is opened to 50%, open valve 3;

[0140] When valve 1 is opened to 75%, open valve 3;

[0141] When valve 1 is fully opened, open valve 3;

[0142] (4) First open valve 2 and valve 4, and then open valve 3 after valve 2 and valve 4 are fully opened. The opening scheme of valve 1 is:

[0143] When valve 3 is opened to 25%, open valve 1;

[0144] When valve 3 is opened to 50%, open valve 1;

[0145] When valve 3 is opened to 75%, open valve 1;

[0146] When valve 3 is fully opened, open valve 1;

[0147] A total of 16 valve opening schemes are obtained in (1) to (4).

[0148] The test data include the total steam flow G of the turbine valve group, throttling loss, regulating stage pressure P1, shaft system vibration amplitude value and bearing temperature value;

[0149] Step 2: Obtain the flow characteristics of the steam turbine valve group according to the total steam flow G and the regulating stage pressure P1, and then obtain the vibration characteristics, bearing temperature characteristics and efficiency characteristics of the steam turbine valve group according to the obtained flow characteristics, throttling loss, shaft vibration amplitude value and bearing temperature value;

[0150] The flow characteristics of the steam turbine valve group are obtained in the following manner:

[0151] The main reason for shaft vibration and bearing temperature rise is the unbalanced air flow force caused by the valve flow difference. i It has a clear relationship with the valve opening and the regulating stage pressure ratio. The steam flow rate G of valve i in the turbine valve group i for:

[0152]

[0153] Where, f(·) is the fitting function, ε is the pressure ratio before and after the valve (when the main steam pressure P0 is unchanged, it is only determined by the regulating stage pressure P1), z i is the opening of valve i;

[0154] The opening z of the valve i i The calculation method is:

[0155] Taking valve 1 as an example, the opening of valve 2 z2 and valve 4 z4 are:

[0156] z2=z4=[1%…100%…100%…100%…100%] (2)

[0157] Among them, the first 100 elements in the opening z2 are 1%, 2%, ..., 100%;

[0158] The opening z1 of valve 1 is:

[0159] z1=[0%…1%…100%-c…100%…100%] (3)

[0160] Wherein, c is the overlap between the third opened valve and the fourth opened valve (the overlap is a variable between [0, 100%)); the elements before 1% in the opening z1 are all 0%, the elements after 1% are 2%, the elements after 2% are 3%, and so on, until reaching 100%-c, the elements after 100%-c are 100%-c+1%, the elements after 100%-c+1% are 100%-c+2%, until reaching 100%, the elements after 100% are all 100%; and the 1% in formula (3) and the second 100% in formula (2) are in the same position in the vector;

[0161] The opening z3 of valve 3 is:

[0162] z3=[0%…0%…1%…c+1%…100%] (4)

[0163] Among them, the elements before 1% in the opening z3 are all 0%, the elements after 1% are 2%, the elements after 2% are 3%, and so on, until it reaches c+1%, the elements after c+1% are c+2%, the elements after c+2% are c+3%, until it reaches 100%; 1% in formula (4) and 100%-c in formula (3) are in the same position in the vector, and there is only one 100% in formula (4).

[0164] According to the operating experience, f is set as a quadratic polynomial, that is, the specific form of the fitting function f(·) is:

[0165] f(z i ,P1)=a1z i 2 +a2P1 2 +a3z i +a4P1+b (5)

[0166] The total steam flow rate G and the regulating stage pressure P1 both change with the opening scheme. The function f(·) is fitted according to the total steam flow rate G and the regulating stage pressure P1 under all opening schemes to obtain the identification results of the coefficients a1, a2, a3, a4 and b;

[0167] Since the total flow is the sum of the flow rates of each valve, the fitting process of the function f(·) satisfies the constraint of formula (6):

[0168]

[0169] In the formula, the proportional coefficient k is a constant, which can be directly obtained by fitting the total flow and regulating stage pressure data in the test. The total flow and regulating stage pressure are roughly in positive proportion.

[0170] The vibration characteristics and tile temperature characteristics of the steam turbine valve group are obtained as follows:

[0171] For example, the third valve to be opened is valve n.

[0172] For any set of tests where the third opened valve is valve n, the steam flow rate of the third opened valve and the steam flow rate of the fourth opened valve are obtained according to the fitting result of the function f(·), and the steam flow rate of the third opened valve is subtracted from the steam flow rate of the fourth opened valve, and the flow difference result is recorded as ΔG;

[0173] Similarly, the flow difference results corresponding to each group of tests under the condition that the third opened valve is valve n are obtained;

[0174] Then, the difference between the shaft vibration amplitude and flow rate when the third valve opened is valve n is fitted to obtain the vibration characteristics when the third valve opened is n:

[0175] SV n =f 1,n (ΔG) (7)

[0176] Among them, SV n is the shaft vibration amplitude value when the third valve is opened (varies with the overlap), f 1,n (·) is the fitting function; the fitting function f 1,n (·) can be a quadratic polynomial, but is not limited to a quadratic polynomial, and can also be a high-order polynomial, the specific order of which is determined according to the fitting accuracy of the experimental data;

[0177] Then, the bearing temperature value and flow rate when the third opened valve is valve n are fitted to obtain the bearing temperature characteristics when the third opened valve is valve n:

[0178] T n =f 2,n (ΔG) (8)

[0179] Among them, T n is the bearing temperature value when the third valve is opened (varies with the overlap), f 2,n (·) is the fitting function; the fitting function f 2,n (·) can be a quadratic polynomial, but is not limited to a quadratic polynomial, and can also be a high-order polynomial, the specific order of which is determined according to the fitting accuracy of the experimental data.

[0180] Then, the throttling loss and flow rate when the third valve opened is valve n are fitted to obtain the efficiency characteristics when the third valve opened is n:

[0181] η n =f 3,n (ΔG) (9)

[0182] Among them, η n is the throttling loss when the third valve is opened for n (which varies with the overlap), and the fitting function f 3,n (·) can be a quadratic polynomial, but is not limited to a quadratic polynomial, and can also be a high-order polynomial, the specific order of which is determined according to the fitting accuracy of the experimental data;

[0183] Similarly, the vibration characteristics, watt-temperature characteristics, and efficiency characteristics of each valve as the third open valve can be obtained respectively, and then the cost function of each valve as the third open valve can be obtained respectively;

[0184] Step 3: design a cost function based on the vibration characteristics, watt-temperature characteristics, and efficiency characteristics obtained in step 2;

[0185] This embodiment optimizes the valve opening law with the goal of achieving the best comprehensive result between shaft system safety and throttling loss, and then designs a cost function.

[0186] For example, the third valve to be opened is valve n.

[0187] J n =K1SV n +K2T n +K3(1-η n ) (10)

[0188] Among them, J n is the total cost, K1, K2 and K3 represent weights.

[0189] Step 4: Take the cost function designed in step 3 as the fitness function of the genetic algorithm, and use the genetic algorithm to optimize the serial number of the third valve to be opened (once the third valve to be opened is determined, the two adjacent valves will be opened synchronously first, and then this valve will be opened after it is fully opened, and finally the diagonal valve of this valve will be opened) and the overlap (i.e. the overlap between the third valve to be opened and the fourth valve to be opened) to obtain the optimization result of the overlapping opening of the turbine valve group.

[0190] The specific process of step 4 is as follows:

[0191] Step 41: Initialize the maximum number of iterations of the genetic algorithm to L and the number of populations to M;

[0192] Step 42: Initialize the third opened valve number n=1;

[0193] Step 43: Generate initial population P(0) = {X 0,1 ,X 0,2 ,…,X 0,M}, where X 0,1 is the overlap corresponding to the first individual in the initial population, X 0,2 is the overlap corresponding to the second individual in the initial population, X 0,M is the overlap corresponding to the Mth individual in the initial population;

[0194] Step 44, initialize the number of iterations l = 0;

[0195] Step 4: Calculate the four valve openings corresponding to the mth individual according to the overlap corresponding to the mth individual in the lth generation population, and then calculate the fitness function value J of the mth individual according to the four valve openings corresponding to the mth individual. n,l,m ;

[0196] After a given overlap, the known valve opening of each valve can be obtained according to equations (2), (3) and (4), and then the corresponding regulating stage pressure P1 can be obtained by equations (5) and (6), and then the pressure ratio ε can be obtained, and then the flow rate of each valve can be obtained by equation (5). Finally, the flow rate of each valve and equations (7), (8) and (9) are used to calculate the shaft system safety and economy indicators, and then the fitness function value is obtained;

[0197] Step 46: Determine whether the iteration stop condition is met;

[0198] If it is satisfied, the iteration is stopped, and the overlap corresponding to the minimum fitness function value obtained in the last iteration is used as the optimized overlap when the third opened valve number is n; and step 47 is continued;

[0199] If it is not satisfied, select, crossover and mutate according to the calculated fitness function values ​​of each individual to generate a new population {X l+1,1 ,X l+1,2 ,…,X l+1,M}, where X l+1,1 is the overlap corresponding to the first individual in the l+1 generation population, X l+1,2 is the overlap corresponding to the second individual in the l+1 generation population, X l+1,M is the overlap corresponding to the Mth individual in the l+1th generation population; let l=l+1, and return to step 4 and 5;

[0200] Step 47: Is n equal to 4?

[0201] If n is equal to 4, execute step 48;

[0202] If n is not equal to 4, set n=n+1 and return to step 43;

[0203] Step 48, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 1 as J1′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 2 as J2′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 3 as J3′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 4 as J4′, then select the minimum value from J1′, J2′, J3′ and J4′, and use the third opened valve number corresponding to the selected minimum value as the final third opened valve number, and use the optimized overlap corresponding to the selected minimum value as the final overlap.

[0204] It should be noted that the iteration stop condition in steps 4 and 6 is to meet the following conditions ① or ②:

[0205] Condition ①: Reach the maximum number of iterations L;

[0206] Condition ②: The minimum fitness function value obtained in the current iteration is less than the set threshold. The threshold here can be set according to actual requirements.

[0207] The process of step 4 is shown in Table 1:

[0208] Table 1 Optimization of valve overlap and opening sequence based on genetic algorithm

[0209]

[0210] In order to verify the effectiveness of the method of the present invention, a verification experiment was designed based on the actual operation data of the steam turbine. Figure 6 and Figure 7 shown.

[0211] It can be seen that there is a strong nonlinearity between the bearing temperature and the actual flow rate. As the actual flow rate increases, the bearing temperature first remains unchanged and then increases. At the same flow rate, the bearing temperature fluctuates violently. This is caused by uneven force due to different valve openings. The trend of shaft vibration related to flow rate is similar to that of bearing temperature, but the fluctuation is greater, indicating that the vibration is more obviously affected by asymmetric airflow. Then, the efficiency, bearing temperature and shaft vibration characteristics were obtained based on the experimental data. Some results are shown in the figure below. Figure 8 and Fig. 9 shown.

[0212] It can be seen that both bearing temperature and vibration increase with the increase of flow difference, that is, as the overlap increases, safety will increase. On the contrary, efficiency and safety will decrease with the increase of overlap. Finally, the use of genetic algorithm to optimize the valve opening sequence and overlap can effectively reduce bearing temperature and shaft vibration, while reducing throttling losses and improving the unit operation economy and reliability.

[0213] The above calculation examples of the present invention are only used to explain the calculation model and calculation process of the present invention in detail, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A steam turbine valve group overlapping opening optimization method that comprehensively considers shaft system safety and economy, characterized in that: The method specifically comprises the following steps: Step 1: Set various opening schemes of the steam turbine valve group, and obtain test data of the steam turbine valve group under various opening schemes at the rated main steam pressure P0; The test data include the total steam flow G of the turbine valve group, throttling loss, regulating stage pressure P1, shaft system vibration amplitude value and bearing temperature value; Step 2: Obtain the flow characteristics of the steam turbine valve group according to the total steam flow G and the regulating stage pressure P1, and then obtain the vibration characteristics, bearing temperature characteristics and efficiency characteristics of the steam turbine valve group according to the obtained flow characteristics, throttling loss, shaft vibration amplitude value and bearing temperature value; Step 3: design a cost function based on the vibration characteristics, watt-temperature characteristics, and efficiency characteristics obtained in step 2; Step 4: Using the cost function designed in step 3 as the fitness function of the genetic algorithm, the genetic algorithm is used to optimize the sequence number and overlap of the third opened valve to obtain the overlapped opening optimization result of the steam turbine valve group.

2. The method for optimizing the overlapping opening of a steam turbine valve group taking into account shaft system safety and economy as claimed in claim 1, characterized in that: The position distribution of each valve in the steam turbine valve group is specifically as follows: After dividing the two-dimensional plane where the turbine valve group is located into four quadrants, a valve is arranged on the angular bisector of each quadrant, and the valve in the first quadrant is recorded as valve 1, the valve in the second quadrant is recorded as valve 2, the valve in the third quadrant is recorded as valve 3, and the valve in the fourth quadrant is recorded as valve 4; and the distance from each valve to the origin of the two-dimensional plane is the same.

3. The method for optimizing the overlapping opening of a steam turbine valve group taking into account shaft system safety and economy as claimed in claim 2, characterized in that: The various opening schemes of the steam turbine valve group are: (1) First open valve 1 and valve 3, and then open valve 2 after valve 1 and valve 3 are fully opened. The opening scheme of valve 4 is: When valve 2 is opened to 25%, open valve 4; When valve 2 is opened to 50%, open valve 4; When valve 2 is opened to 75%, open valve 4; When valve 2 is fully opened, open valve 4; (2) First open valve 1 and valve 3, and then open valve 4 after valve 1 and valve 3 are fully opened. The opening scheme of valve 2 is: When valve 4 is opened to 25%, open valve 2; When valve 4 is opened to 50%, open valve 2; When valve 4 is opened to 75%, open valve 2; When valve 4 is fully opened, open valve 2; (3) First open valve 2 and valve 4, and then open valve 1 after valve 2 and valve 4 are fully opened. The opening scheme of valve 3 is: When valve 1 is opened to 25%, open valve 3; When valve 1 is opened to 50%, open valve 3; When valve 1 is opened to 75%, open valve 3; When valve 1 is fully opened, open valve 3; (4) First open valve 2 and valve 4, and then open valve 3 after valve 2 and valve 4 are fully opened. The opening scheme of valve 1 is: When valve 3 is opened to 25%, open valve 1; When valve 3 is opened to 50%, open valve 1; When valve 3 is opened to 75%, open valve 1; When valve 3 is fully opened, open valve 1; That is, a total of 16 valve opening schemes are obtained in (1) to (4).

4. The method for optimizing the overlapping opening of a steam turbine valve group taking into account shaft system safety and economy as claimed in claim 3 is characterized in that: The flow characteristics of the steam turbine valve group are obtained in the following manner: Steam flow rate G of valve i in the turbine valve group i for: Among them, f(·) is the fitting function, ε is the pressure ratio before and after the valve, z i is the opening of valve i; The specific form of the fitting function f(·) is: <h2 style=";text-align:left;direction:ltr">f(z<h2 style=";text-align:left;direction:ltr"> i <h2 style=";text-align:left;direction:ltr"> ,P1)=a1z<h2 style=";text-align:left;direction:ltr"> i <h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a2P1<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a3z<h2 style=";text-align:left;direction:ltr"> i <h2 style=";text-align:left;direction:ltr"> +a4P1+b The function f(·) is fitted according to the total steam flow G and the regulating stage pressure P1 under all opening schemes, and the identification results of the coefficients a1, a2, a3, a4 and b are obtained; And the fitting process of function f(·) satisfies the following constraints:

5. The method for optimizing the overlapping opening of a steam turbine valve group taking into account shaft system safety and economy as claimed in claim 4, characterized in that: The opening z of the valve i i The calculation method is: Taking valve 1 as an example, the opening of valve 2 z2 and valve 4 z4 are: z2=z4=[1%…100%…100%…100%…100%] The opening z1 of valve 1 is: z1=[0%…1%…100%-c…100%…100%] Where c is the overlap between the third opened valve and the fourth opened valve; The opening z3 of valve 3 is: z3=[0%...0%...1%...c+1%...100%].

6. A steam turbine valve group overlapping opening optimization method taking into account shaft system safety and economy as claimed in claim 5, characterized in that: The vibration characteristics, tile temperature characteristics and efficiency characteristics of the steam turbine valve group are obtained as follows: For example, the third valve to be opened is valve n. For any set of tests where the third opened valve is valve n, the steam flow rate of the third opened valve and the steam flow rate of the fourth opened valve are obtained according to the fitting result of the function f(·), and the steam flow rate of the third opened valve is subtracted from the steam flow rate of the fourth opened valve, and the flow difference result is recorded as ΔG; Similarly, the flow difference results corresponding to each group of tests under the condition that the third opened valve is valve n are obtained; Then, the difference between the shaft vibration amplitude and flow rate when the third valve opened is valve n is fitted to obtain the vibration characteristics when the third valve opened is n: SV n =f 1,n (ΔG) Among them, SV n is the shaft vibration amplitude value when the third valve is opened, 1,n (·) is the fitting function; Then, the bearing temperature value and flow rate when the third opened valve is valve n are fitted to obtain the bearing temperature characteristics when the third opened valve is valve n: T n =f 2,n (ΔG) Among them, T n is the bearing temperature value when the third open valve is n, f 2,n (·) is the fitting function; Then, the throttling loss and flow rate when the third valve opened is valve n are fitted to obtain the efficiency characteristics when the third valve opened is n: or n =f 3,n (ΔG) Among them, η n It is the throttling loss when the third valve opened is n.

7. A steam turbine valve group overlapping opening optimization method taking into account shaft system safety and economy as claimed in claim 6, characterized in that: The specific process of step three is: For example, the third valve to be opened is valve n. J n =K1SV n +K2T n +K3(1-η n ) Among them, J n is the total cost, K1, K2 and K3 represent weights.

8. The method for optimizing the overlapping opening of a steam turbine valve group taking into account shaft system safety and economy as claimed in claim 7, characterized in that: The specific process of step 4 is as follows: Step 41: Initialize the maximum number of iterations of the genetic algorithm to L and the number of populations to M; Step 42: Initialize the third opened valve number n=1; Step 43: Generate initial population P(0) = {X 0,1 ,X 0,2 ,…,X 0,M }, where X 0,1 is the overlap corresponding to the first individual in the initial population, X 0,2 is the overlap corresponding to the second individual in the initial population, X 0,M is the overlap corresponding to the Mth individual in the initial population; Step 44, initialize the number of iterations l = 0; Step 4: Calculate the four valve openings corresponding to the mth individual according to the overlap corresponding to the mth individual in the lth generation population, and then calculate the fitness function value J of the mth individual according to the four valve openings corresponding to the mth individual. n,l,m ; Step 46: Determine whether the iteration stop condition is met; If it is satisfied, the iteration is stopped, and the overlap corresponding to the minimum fitness function value obtained in the last iteration is used as the optimized overlap when the third opened valve number is n; and step 47 is continued; If it is not satisfied, select, crossover and mutate according to the calculated fitness function values ​​of each individual to generate a new population {X l+1,1 ,X l+1,2 ,…,X l+1,M }, where X l+1,1 is the overlap corresponding to the first individual in the l+1 generation population, X l+1,2 is the overlap corresponding to the second individual in the l+1 generation population, X l+1,M is the overlap corresponding to the Mth individual in the l+1th generation population; let l=l+1, and return to step 4 and 5; Step 47: Is n equal to 4? If n is equal to 4, then execute step 48; If n is not equal to 4, set n=n+1 and return to step 43; Step 48, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 1 as J1′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 2 as J2′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 3 as J3′, record the fitness function value corresponding to the optimized overlap when the third opened valve is numbered 4 as J4′, then select the minimum value from J1′, J2′, J3′ and J4′, and use the third opened valve number corresponding to the selected minimum value as the final third opened valve number, and use the optimized overlap corresponding to the selected minimum value as the final overlap.

9. A steam turbine valve group overlapping opening optimization method taking into account shaft system safety and economy as claimed in claim 8, characterized in that: The iteration stopping condition in step 46 is to meet the following conditions ① or ②: Condition ①: Reach the maximum number of iterations L; Condition ②: The minimum fitness function value obtained in the current iteration is less than the set threshold.

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