A steam turbine back pressure calculation method and electronic device based on iterative method

Abstract

The present invention relates to a method and electronic device for calculating steam turbine back pressure based on an iteration method. The calculation method comprises: S1: given an initial steam turbine back pressure P i And the heat of steam inlet per unit time Q 1 According to the turbine characteristic curve, the turbine power P changes with P i Variation of fitting function; S2: According to Q 1 , P i Substituting the fitted function into the obtained turbine power P and P i The corresponding saturated water enthalpy and turbine steam flow rate per unit time D s Get the condenser heat load Q 2 , D s is a given value; S3: according to Q 2 , Cooling water flow D w , condenser cleanliness φ, cooling water inlet temperature T 1 Get the calculated turbine back pressure P i+1 ,φ,D w 、T 1 is a given value; S4: judge P i ‑P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output P i If not, then P i+1 Instead of P i , and repeat S1, S2, S3, S4 until the set conditions are met, and the σ is a given value. The present invention does not need to analyze the properties of the implicit function, and can quickly calculate the result within a given accuracy through simple programming.

Description

Technical Field

[0001] The present invention relates to the field of steam turbine back pressure calculation methods, and in particular to a steam turbine back pressure calculation method based on an iteration method and an electronic device. Background Art

[0002] At present, the energy-saving diagnosis and optimization technology of power generation enterprises is developing towards a comprehensive platform, which places high demands on the programmability of the calculation program. On the other hand, some key variables in the program cannot be given explicit expressions, so they cannot be simplified by control variables. The existing steam turbine back pressure calculation method has complex loop nested calculations, which is difficult to program. It is also necessary to analyze the properties of the implicit function in the steam turbine back pressure calculation. The adjustment step size of each difference is not easy to determine, and the programmability is limited by the complexity of the equation. Summary of the invention

[0003] The purpose of the present invention is to provide a method for calculating the back pressure of a steam turbine based on an iteration method. The method for calculating the back pressure of a steam turbine based on an iteration method has the characteristics of not requiring detailed analysis of the properties of implicit functions, strong programmability, and good applicability.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for calculating steam turbine back pressure based on an iterative method, comprising:

[0006] S1: Given initial turbine back pressure P i and the unit time steam turbine inlet heat Q1, according to the steam turbine characteristic curve, the steam turbine power P is obtained as the P i Variation of the fitting function;

[0007] S2: According to Q1, P i Substitute the turbine power P and the P obtained by fitting the function into i The corresponding saturated water enthalpy and turbine steam flow rate per unit time D s The condenser heat load Q2 is obtained, where D s is a given value;

[0008] S3: According to Q2, cooling water flow D w , condenser cleanliness φ, cooling water inlet temperature T1 to calculate the turbine back pressure P i+1 , where the φ, the D w , said T1 is a given value;

[0009] S4: Determine the P i With the P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the Pi+1 Instead of the P i , and repeat the above steps until the setting conditions are completed, where σ is a given value.

[0010] Preferably, in step S2, the difference between Q1 and P is the exhaust heat Q of the steam turbine per unit time. 排 .

[0011] Preferably, in step S2, the saturated water enthalpy value corresponding to P and D s The product of is the heat Q taken away by condensed water per unit time 带 .

[0012] Preferably, in step S2, the condenser heat load Q2 is the Q 排 With the Q 带 The difference.

[0013] Preferably, in step S3, according to Q2, D w Get the cooling water inlet and outlet temperature difference ΔT.

[0014] Preferably, in step S3, according to the ΔT, T1, cooling water flow rate D w , condenser cleanliness φ to obtain the condenser temperature, and the saturated water vapor pressure corresponding to the condenser temperature is used to calculate the turbine back pressure P i+1 .

[0015] Preferably, in step S4, when the P i With the P i+1 If the absolute value of the difference is greater than σ, then P i+1 Instead of the P i , repeat step S1, and obtain the new turbine power P and the turbine exhaust heat per unit time Q 排 .

[0016] Preferably, in step S4, when the P i With the P i+1 If the absolute value of the difference is greater than σ, then P i+1 Instead of the P i , repeat step S2, and obtain the new heat Q taken away by the condensed water per unit time according to the condenser temperature T 带 , and then according to the new unit time steam turbine exhaust heat Q 排 Get the new condenser heat load Q2.

[0017] Preferably, in step S4, when the P i With the P i+1 If the absolute value of the difference is greater than σ, then P i+1 Instead of the Pi Repeat step S3 to obtain a new calculated turbine back pressure P i+1 , then execute step S4.

[0018] An electronic device includes a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steam turbine back pressure calculation method based on the iteration method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The above technical solution provides a method for calculating the steam turbine back pressure based on an iterative method, which can quickly calculate the result within a given accuracy through four steps. The four steps are:

[0021] S1: Given initial turbine back pressure P i and the unit time steam turbine inlet heat Q1, according to the steam turbine characteristic curve, the steam turbine power P is obtained as the P i Variation of the fitting function;

[0022] S2: According to Q1, P i Substitute the turbine power P and the P obtained by fitting the function into i The corresponding saturated water enthalpy and turbine steam flow rate per unit time D s The condenser heat load Q2 is obtained, where D s is a given value;

[0023] S3: According to Q2, cooling water flow D w , condenser cleanliness φ, cooling water inlet temperature T1 to calculate the turbine back pressure P i+1 , where the φ, the D w , said T1 is a given value;

[0024] S4: Determine the P i With the P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the P i+1 Instead of the P i , and repeat the above steps until the setting conditions are completed, where σ is a given value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method for calculating steam turbine back pressure provided in an embodiment of the present invention.

[0026] Figure 2 A schematic diagram of a method for calculating steam turbine back pressure provided in an embodiment of the present invention.

[0027] Figure 3 A schematic diagram of an iterative method provided by an embodiment of the present invention.

[0028] Figure 4 A schematic diagram of experimental data provided by an embodiment of the present invention.

[0029] Figure 5 A schematic diagram of the number of experimental iterations provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be described in more detail below in conjunction with the accompanying drawings. It should be noted that the description of the present invention with reference to the accompanying drawings is only illustrative and not restrictive. The various embodiments can be combined with each other to form other embodiments not shown in the following description.

[0031] See also Figure 1-2 In an embodiment of the present invention, a method for calculating steam turbine back pressure based on an iterative method is provided, comprising:

[0032] S1: Given initial turbine back pressure P i and the unit time steam turbine inlet heat Q1, according to the steam turbine characteristic curve, the steam turbine power P is obtained as the P i Variation of the fitting function;

[0033] S2: According to Q1, P i Substitute the turbine power P and the P obtained by fitting the function into i The corresponding saturated water enthalpy and turbine steam flow rate per unit time D s The condenser heat load Q2 is obtained, where the D s is a given value;

[0034] S3: According to Q2, cooling water flow D w , condenser cleanliness φ, cooling water inlet temperature T1 to calculate the turbine back pressure P i+1 , where the φ, the D w , said T1 is a given value;

[0035] S4: Determine the P i With the P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the P i+1 Instead of the P i , and repeat the above steps until the setting conditions are completed, where σ is a given value.

[0036] The turbine back pressure is affected by both the steam side and the water side. The steam side refers to the steam side of the condenser, and the water side refers to the cooling water side of the condenser. The present invention takes the pure condensing condition as an example, and S2 is the calculation step of the steam side, and S3 is the calculation step of the water side. That is, when the intermediate variable calculation value is given, only the calculation accuracy φ and the initial turbine back pressure P need to be set. i Then the calculated turbine back pressure P that meets the requirements can be obtained i+1 , which facilitates modular programming and makes it easier to monitor and determine the cause of failures during application deployment, thereby reducing the failure rate and fault handling time.

[0037] Among them, the functional relationship of the fitting function can be obtained by fitting the turbine characteristic curve and test data. Therefore, given the turbine inlet heat per unit time Q1, turbine back pressure P i The turbine power P can be obtained by numerical value and fitting function.

[0038] In step S2, the heat of steam inlet per unit time Q1 and the back pressure P of the steam turbine are calculated. i The corresponding steam turbine power P, and then the steam turbine exhaust heat per unit time Q 排 ; By calculating the saturated water enthalpy value corresponding to the steam turbine power P and the steam inlet flow rate D per unit time s The product of , we get the heat Q taken away by condensed water per unit time 带 ; By calculating the exhaust heat Q of the steam turbine per unit time 排 The heat Q taken away by condensed water per unit time 带 The difference between the two values ​​can be used to obtain the condenser heat load Q2. The steam flow rate per unit time D s is a given value.

[0039] In step S3, the condenser heat load Q2 and the cooling water flow D w The cooling water inlet and outlet temperature difference ΔT can be calculated, and then according to the cooling water inlet and outlet temperature difference ΔT, cooling water inlet temperature T1, cooling water flow rate D w , condenser cleanliness φ to obtain the condenser temperature, and the saturated water vapor pressure corresponding to the condenser temperature is used to calculate the turbine back pressure P i+1 .

[0040] In step S4, given the calculation accuracy σ, determine P i -P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the P i+1 Instead of the P i Repeat step S1 to get the new turbine power P, then repeat step S2 to get the new condenser heat load Q2, then repeat step S3 to get the new calculated turbine back pressure P i+1Finally, repeat step S4 to determine P i -P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the P i+1 Instead of the P i , and continue to repeat the above steps until the set conditions are completed.

[0041] Therefore, the steam turbine back pressure calculation method provided by the present invention starts with the analysis of the calculation principle, establishes the iterative calculation method of this type of implicit function, and reversely verifies the feasibility of this method in steam turbine back pressure calculation through quantitative calculation. Moreover, the steam turbine back pressure calculation method does not need to analyze the properties of the implicit function in detail, and can quickly calculate the result within a given accuracy through simple programming, which can be promoted and applied in similar key parameter calculations.

[0042] See also Figure 3 , where the straight line is all solutions that satisfy y=x, and the curve is the coordinate curve corresponding to the function f(x). The condition for direct iterative solution is that within the limited range of the solution value point A, the function f(x) curve is continuously differentiable, and the derivative at the solution value point A is less than 1.

[0043] The iterative calculation process is described as follows:

[0044] Step 1, arbitrarily give an initial value of x = a, the intersection point of the x-axis vertical line through a and the thin solid line is B, at this time the function value of f(x) is the y-coordinate value of point B, draw a x-axis horizontal line through B, and the intersection point with the thick solid line is C, the x-coordinate value corresponding to C is b, b is the function value of f(x) when x is equal to a;

[0045] Step 2, let x = b. If the absolute value of the difference between a and b is less than the set accuracy, then b is the solution. If it is greater than the set accuracy, return to step 1.

[0046] If the assumed value a is on the right side of the solution value point A, the algorithm has the same process, but the optimization direction is to the left and continuously approach the solution value.

[0047] See also Figure 4-5 The present invention also provides a set of experiments, in which various parameters required for the calculation method of the steam turbine back pressure are provided, among which the initial steam turbine back pressure P i is 3kPa, the calculation accuracy σ is 0.01kPa, the unit time steam turbine inlet heat Q1 is 274.634MW, and the unit time steam turbine inlet flow rate D s 233.32t·h -1 , cooling water flow D w 27000t·h -1 , the cooling water inlet temperature T1 is 28℃, and the condenser cleanliness φ is 0.75.

[0048] According to the calculation steps of the steam turbine back pressure calculation method of the present invention, the above condition parameters are input into the steam turbine back pressure calculation method and iterative calculation is performed. The key parameters in the iterative process are shown in FIG. Figure 4-5 , where the program terminates after the turbine back pressure calculation method iterates 3 times, and the output is the calculated turbine back pressure of 5.584 kPa that meets the accuracy requirements.

[0049] This embodiment further provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to execute the steps of the steam turbine back pressure calculation method.

[0050] Optionally, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0051] Optionally, in this embodiment, the processor may be configured to perform the following steps through a computer program:

[0052] S1: Given initial turbine back pressure P i and the unit time steam inlet heat Q1, according to the steam turbine characteristic curve, the steam turbine power P is obtained as the steam turbine back pressure P i Variation of the fitting function, where the Q1 and the P i is a given value;

[0053] S2: According to Q1, turbine back pressure P i Substitute the above fitting function to obtain the turbine power P, the P i The corresponding saturated water enthalpy and turbine steam flow rate per unit time D s The condenser heat load Q2 is obtained, where D s is a given value;

[0054] S3: According to Q2, cooling water flow D w , condenser cleanliness φ, cooling water inlet temperature T1 to calculate the turbine back pressure P i+1 , where the φ, the D w , said T1 is a given value;

[0055] S4: Determine the P i With the P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the P i+1 Instead of the P i , and repeat the above steps until the setting conditions are completed, where σ is a given value.

[0056] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for calculating steam turbine back pressure based on an iterative method, characterized in that: include: S1: Given initial turbine back pressure P i and the unit time steam turbine inlet heat Q1, according to the steam turbine characteristic curve, the steam turbine power P is obtained as the P i Variation of the fitting function; S2: According to Q1, P i Substitute the turbine power P and the P obtained by fitting the function into i The corresponding saturated water enthalpy and turbine steam flow rate per unit time D s The condenser heat load Q2 is obtained, where the D s is a given value; S3: According to Q2, cooling water flow D w , condenser cleanliness φ, cooling water inlet temperature T1 to calculate the turbine back pressure P i+1 , where the φ, the D w , said T1 is a given value; S4: Determine the P i With the P i+1 Is the absolute value of the difference less than the calculation accuracy σ? If so, output the P i If not, then the P i+1 Instead of the P i , and repeat S1, S2, S3, S4 until the set conditions are completed, wherein σ is a given value; In step S2, the difference between Q1 and P is the exhaust heat Q per unit time. 排 ; In step S2, the saturated water enthalpy value corresponding to P and D s The product of is the heat Q taken away by condensed water per unit time 带 ; In step S2, the condenser heat load Q2 is the Q 排 With the Q 带 The difference between In step S3, according to Q2, D w Get the cooling water inlet and outlet temperature difference ΔT; In step S3, according to the ΔT, T1, cooling water flow rate D w , condenser cleanliness φ to obtain the condenser temperature, and the saturated water vapor pressure corresponding to the condenser temperature is used to calculate the turbine back pressure P i+1 .

2. The method for calculating the steam turbine back pressure according to claim 1, characterized in that: In step S4, when the P i With the P i+1 If the absolute value of the difference is greater than σ, then P i+1 Instead of the P i , repeat step S1, and obtain the new turbine power P and the turbine exhaust heat per unit time Q 排 .

3. The method for calculating the steam turbine back pressure according to claim 2, characterized in that: In step S4, when the P i With the P i+1 If the absolute value of the difference is greater than σ, then P i+1 Instead of the P i , repeat step S2, and obtain the new heat Q taken away by the condensed water per unit time according to the condenser temperature T 带 , and then according to the new unit time steam turbine exhaust heat Q 排 Get the new condenser heat load Q2.

4. The method for calculating the steam turbine back pressure according to claim 3, characterized in that: In step S4, when the P i With the P i+1 If the absolute value of the difference is greater than σ, then P i+1 Instead of the P i Repeat step S3 to obtain a new calculated turbine back pressure P i+1 , then execute step S4.

5. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to run the computer program to execute the steam turbine back pressure calculation method based on an iterative method according to any one of claims 1 to 4.

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