A steam turbine flow characteristic diagnosis method

Abstract

The application discloses a steam turbine flow characteristic diagnosis method, which is based on the principle of the steam turbine and the field regulating valve flow characteristic test, establishes a single numerical form steam turbine unit regulating valve flow characteristic diagnosis mathematical model, generates and outputs the deviation value X of the real-time flow characteristic factor and the benchmark flow characteristic factor T -X0; adds the deviation value X T -X0 to the DCS system historical database, presents the broken line trend chart of the single parameter changing over time in the DCS system historical trend, so as to realize the accurate evaluation and real-time early warning function of the steam turbine unit regulating valve flow linearity.

Description

Technical Field

[0001] The invention relates to a method for diagnosing flow characteristics of a steam turbine, and belongs to the technical field of steam turbine operation. Background Art

[0002] Modern steam turbine units widely use DEH (Digital Electro-Hydraulic Control System) digital electro-hydraulic control systems for valve management. During operation, the steam turbine increases the steam inlet flow by sequentially (or synchronously) opening several control valves. The numerical correspondence between the flow command (FDEM) or total valve position command and the actual steam inlet flow of the steam turbine is generally considered the flow characteristic of the steam turbine unit. Steam turbine flow characteristic testing is an effective means for accurately adjusting the steam turbine steam distribution function on site. Steam turbine unit flow characteristics with excellent linearity are the basis for steam turbine unit speed control system modeling, machine-network coordinated response, and main parameter optimization.

[0003] Field experience shows that due to changes in the characteristics of the steam inlet valve or the main equipment, the DEH steam distribution function cannot match the nonlinear characteristics of the steam inlet valve (group) in a timely manner, resulting in a decrease in the accuracy of the steam inlet flow control. However, during daily operation, the operating personnel have neither monitoring means nor analysis tools to determine whether the throttle flow characteristics are linear; often, only when the unit shows obvious control deterioration, such as primary frequency regulation, AGC performance degradation, or abnormal oscillation of the unit power, will it arouse the suspicion or vigilance of the operating personnel. To this end, the present invention proposes a turbine flow characteristic diagnosis mathematical model and evaluation method based on the turbine principle, and directly uses the historical trend chart of the DCS (Distributed Control System) system to achieve accurate evaluation of the turbine unit throttle flow linearity and real-time early warning functions. Summary of the Invention

[0004] The purpose of the present invention is to adapt to the characteristic that the DCS system historical trend chart only supports the display of line charts that change over time, directly utilize the DCS system historical trend chart to achieve accurate evaluation of the linearity of the turbine unit throttle flow rate and real-time early warning functions, and propose a turbine flow characteristic diagnosis method.

[0005] The present invention provides a method for diagnosing flow characteristics of a steam turbine, wherein:

[0006] Based on the steam turbine principle and on-site valve flow characteristic test, a single numerical form of steam turbine valve flow characteristic diagnosis mathematical model is established to generate and output the deviation value X between the real-time flow characteristic factor and the reference flow characteristic factor. T -X0;

[0007] The deviation value X T-X0 is added to the DCS system historical database, and a line trend chart showing changes over time is presented in the DCS system historical trend to accurately analyze the linearity of the turbine unit's regulating valve flow and provide real-time warnings.

[0008] Furthermore, the method specifically comprises the following steps:

[0009] Step 1: According to formula (1), calculate the baseline flow characteristic factor X0 and the uncorrected flow characteristic factor X of the computer group under operating conditions;

[0010]

[0011]

[0012] Where: X0 is the reference flow characteristic factor under the total valve position instruction of 100% in the operating condition; It is the regulating stage pressure under the total valve position instruction of 100% in the operating condition; is the main steam pressure under the total valve position instruction of 100% of the operating condition; X is the total valve position instruction of the operating condition Uncorrected flow characteristic factor under ; is the total valve position instruction; p t The total valve position instruction for the operating condition The regulating stage pressure under the condition of p0 is the total valve position instruction of the operating condition. Main steam pressure under

[0013] Step 2: Based on the test data of the flow characteristic of the steam turbine valve, the flow characteristic factors X1 and X2 under the test conditions are obtained according to formula (3) and formula (4);

[0014]

[0015]

[0016] Where: X1 is the flow characteristic factor characterized by the regulating stage parameters under the test conditions; X2 is the flow characteristic factor characterized by the regulating stage and high-pressure cylinder exhaust parameters under the test conditions; p 00 It is the main steam pressure under the total valve position instruction of 100% in the test condition; p 10 It is the regulating stage pressure under the total valve position instruction of 100% in the test condition; p 20 v is the exhaust steam pressure of the high-pressure cylinder under the total valve position instruction of 100% in the test condition; 10 is the regulating stage specific capacity under the test condition total valve position instruction 100%; p 01 is the main steam pressure under any main valve position instruction in the test condition; p 11 is the regulating stage pressure under any total valve position instruction in the test condition; p 21is the exhaust steam pressure of the high-pressure cylinder under any main valve position instruction of the test condition; v 11 It is the regulating stage specific volume under any total valve position instruction of the test condition;

[0017] Step 3: For any total valve position command under the test conditions, calculate the corresponding total valve position command correction coefficient according to formula (5):

[0018]

[0019] Where: It is the total valve position instruction correction coefficient under the test conditions.

[0020] Step 4: According to formula (6), calculate the unit real-time flow characteristic factor X under operating conditions T ;

[0021]

[0022] Step 5: Compile formula (1-6) into the DCS system configuration to generate and output the deviation value X between the real-time flow characteristic factor and the reference flow characteristic factor. T -X0; set the deviation value X T -X0 is added to the DCS system historical database, and a line trend chart showing changes over time is presented in the DCS system historical trend.

[0023] Furthermore, the method: the turbine unit valve flow characteristic test is carried out according to the main valve position instruction The actual flow rate G is equal to the actual flow rate to implement the setting of the DEH system steam distribution function; the actual flow rate is calculated according to formula (7):

[0024]

[0025] Where p 10 is the regulating stage pressure under the total valve position instruction of 100% in the test condition, p 20 is the high pressure cylinder exhaust pressure under the test condition total valve position instruction 100%, v 10 is the regulating stage specific capacity under the test condition total valve position instruction 100%, p 01 is the main steam pressure under any total valve position instruction under test conditions, p 11 is the regulating stage pressure under any total valve position instruction under the test condition, p 21 is the high pressure cylinder exhaust pressure under any main valve position instruction of the test condition, v 11 is the regulating stage specific volume under any total valve position instruction of the test condition. Further, the method: under the operating condition, when X T -X0<5%, the linearity of the valve flow characteristic is considered normal; when X TWhen -X0≥5%, the linearity of the throttle flow characteristic is considered abnormal, and a prompt is given to "re-adjust the steam distribution function."

[0026] The beneficial effect of the present invention is that it adapts to the characteristic that the historical trend graph of the DCS system only supports the display of a line graph that changes with time, and helps operating personnel to directly use the historical trend graph of the DCS system to scientifically and accurately evaluate the linearity of the throttle flow of the turbine unit and provide real-time early warning, so as to discover and eliminate the throttle flow characteristic faults at an early stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 Schematic diagram of the setting effect of the flow characteristic test of the regulating valve of the steam turbine unit according to the embodiment of the present invention;

[0029] Figure 2 Schematic diagram of flow characteristic factors X1 and X2 under test conditions of an embodiment of the present invention;

[0030] Figure 3 is the total valve position instruction correction coefficient under the test conditions of the embodiment of the present invention Schematic diagram;

[0031] Figure 4 Five months after the flow characteristics of the unit in the embodiment of the present invention are adjusted X T -X0 trend chart;

[0032] Figure 5 11 months after the flow characteristics of the unit in the embodiment of the present invention were adjusted T -X0 trend chart. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is shown in the figure. Figures 1-5 , clearly and completely describe the technical solutions in the embodiments of the present invention.

[0034] The unit in this embodiment is a steam turbine unit with a nozzle. First, the test personnel tested the flow characteristics of the steam turbine unit valve, and then, according to the main valve position instruction, =Equal to the actual flow rate G, the setting work of the steam distribution function of the DEH system of the unit is completed (such as Figure 1 In the following twelve months, the operator used the DCS system historical trend chart to observe the changes in the linearity of the throttle flow characteristics.

[0035] A method for diagnosing flow characteristics of a steam turbine according to an embodiment of the present invention includes the following steps:

[0036] Step 1: Calculate the baseline flow characteristic factor X0 and the uncorrected flow characteristic factor X of the computer group under operating conditions according to equations (1) and (2).

[0037]

[0038]

[0039] Where: X0 is the reference flow characteristic factor under the total valve position instruction of 100% in the operating condition; It is the regulating stage pressure under the total valve position instruction of 100% in the operating condition; is the main steam pressure under the total valve position instruction of 100% of the operating condition; X is the total valve position instruction of the operating condition Uncorrected flow characteristic factor under ; is the total valve position instruction; p t The total valve position instruction for the operating condition The regulating stage pressure at the bottom; p o The total valve position instruction for the operating condition Main steam pressure under .

[0040] Step 2: Based on the test data of the flow characteristic of the steam turbine valve, the flow characteristic factors X1 and X2 under the test conditions are obtained according to formula (3) and formula (4). Figure 2 shown).

[0041]

[0042]

[0043] Where: X1 is the flow characteristic factor characterized by the regulating stage parameters under the test conditions; X2 is the flow characteristic factor characterized by the regulating stage and high-pressure cylinder exhaust parameters under the test conditions; p 00 It is the main steam pressure under the total valve position instruction of 100% in the test condition; p 10 It is the regulating stage pressure under the total valve position instruction of 100% in the test condition; p 20 v is the exhaust steam pressure of the high-pressure cylinder under the total valve position instruction of 100% in the test condition; 10 is the regulating stage specific capacity under the test condition total valve position instruction 100%; p 01 is the main steam pressure under any main valve position instruction in the test condition; p 11 is the regulating stage pressure under any total valve position instruction in the test condition; p 21 is the exhaust steam pressure of the high-pressure cylinder under any main valve position instruction of the test condition; v 11It is the regulating stage specific capacity under any total valve position instruction of the test condition.

[0044] Step 3: For any total valve position command under the test conditions, calculate the corresponding total valve position command correction coefficient according to formula (5): (like Figure 3 shown).

[0045]

[0046] Where: It is the total valve position instruction correction coefficient under the test conditions.

[0047] Step 4: According to formula (6), calculate the unit real-time flow characteristic factor X under operating conditions T .

[0048]

[0049] Step 5: Compile formula (1-6) into the DCS system configuration to generate and output the deviation value X between the real-time flow characteristic factor and the reference flow characteristic factor. T -X0; set the deviation value X T -X0 is added to the DCS system historical database, and a line trend chart showing changes over time is presented in the DCS system historical trend.

[0050] The flow characteristic test of the steam turbine unit regulating valve is carried out according to the main valve position instruction. Equal to the actual flow G to implement the DEH system steam distribution function setting (such as Figure 1 The actual flow rate is calculated according to formula (7):

[0051]

[0052] Under operating conditions, when X T When -X0<5%, the linearity of the valve flow characteristic is considered normal. Figure 4 As shown, the fifth month after the flow characteristics of the unit in the embodiment of the present invention are adjusted X T The maximum value of -X0 is less than 4%; in this case, the linearity of the throttle flow characteristic can be considered normal.

[0053] When X T When -X0≥5%, the linearity of the valve flow characteristic is considered abnormal, and a prompt "Re-adjust the steam distribution function" is given. Figure 5 As shown, the flow characteristics of the unit according to the embodiment of the present invention are adjusted eleven months later. T The maximum value of -X0 exceeds 10%. In this case, the linearity of the throttle flow characteristic is considered abnormal and is marked in red in the historical trend chart of the DCS system as a warning.

[0054] The above has carried out the detailed introduction to the steam turbine flow characteristic diagnosis mathematical model and the evaluation method provided by the application, the principle and the implementation mode of the application are described by applying the specific example in the embodiment, the above embodiment is only used for helping the understanding of the method and the core idea of the application. It should be pointed out that for ordinary skilled person in the art, without departing from the principle of the application, the application can be improved and modified, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A method for diagnosing flow characteristics of a steam turbine, characterized in that: The method: Based on the steam turbine principle and on-site valve flow characteristic test, a single numerical form of steam turbine valve flow characteristic diagnosis mathematical model is established to generate and output the deviation value between the real-time flow characteristic factor and the reference flow characteristic factor. ; The deviation value Add to the DCS system history database and present a line trend chart that changes over time in the DCS system history trend to accurately analyze the linearity of the steam turbine unit valve flow and provide real-time warnings; The specific steps include: Step 1: Based on formula (1), the baseline flow characteristic factor of the computer group under operating conditions and uncorrected flow characteristic factors ; , formula (1) , formula (2) Where: It is the reference flow characteristic factor under the total valve position instruction of 100% in the operating condition; It is the regulating stage pressure under the total valve position instruction of 100% in the operating condition; is the main steam pressure under the total valve position instruction of 100% of the operating condition; X is the total valve position instruction of the operating condition Uncorrected flow characteristic factor under ; is the total valve position instruction; The total valve position command for the operating condition The regulating stage pressure at the bottom; The total valve position command for the operating condition Main steam pressure under Step 2: Based on the test data of the flow characteristic of the steam turbine unit valve, the flow characteristic factors under the test conditions are obtained according to formula (3) and formula (4). and ; , formula (3) , formula (4) Where: It is the flow characteristic factor characterized by the regulating stage parameters under the test conditions; It is the flow characteristic factor characterized by the exhaust parameters of the regulating stage and high-pressure cylinder under the test conditions; It is the main steam pressure under the test condition total valve position instruction of 100%; It is the regulating stage pressure under the total valve position instruction of 100% in the test condition; It is the exhaust steam pressure of the high-pressure cylinder under the total valve position instruction of 100% in the test condition; It is the regulating stage specific capacity under the test condition of total valve position instruction 100%; It is the main steam pressure under any main valve position instruction of the test condition; It is the regulating stage pressure under any total valve position instruction in the test condition; The exhaust steam pressure of the high-pressure cylinder under any main valve position instruction of the test condition; It is the regulating stage specific capacity under any total valve position instruction of the test condition; Step 3: For any total valve position command under the test conditions, calculate the corresponding total valve position command correction coefficient according to formula (5). ; , formula (5) Where: is the total valve position instruction correction coefficient under the test conditions; Step 4: Calculate the unit real-time flow characteristic factor under operating conditions according to formula (6): ; , formula (6) Step 5: Compile equations (1) to (6) into the DCS system configuration to generate and output the deviation value between the real-time flow characteristic factor and the reference flow characteristic factor. .

2. A steam turbine flow characteristic diagnosis method according to claim 1, characterized in that: The method: The steam turbine unit regulating valve flow characteristic test is carried out according to the main valve position instruction Equal to actual flow To implement the setting of the DEH system steam distribution function; the actual flow is calculated according to formula (7): , formula (7) Where, It is the regulating stage pressure under the total valve position instruction of 100% in the test condition. It is the exhaust steam pressure of the high pressure cylinder under the total valve position instruction of 100% in the test condition. It is the regulating stage specific capacity under the test condition total valve position instruction of 100%, is the main steam pressure under any main valve position instruction of the test condition, It is the regulating stage pressure under any total valve position instruction of the test condition, is the exhaust steam pressure of the high-pressure cylinder under any main valve position instruction of the test condition, It is the regulating stage specific capacity under any total valve position instruction in the test condition.

3. A steam turbine flow characteristic diagnosis method according to claim 2, characterized in that: The method: Under operating conditions, when When the linearity of the valve flow characteristic is considered normal; when When the linearity of the throttle flow characteristic is considered abnormal, the prompt "Re-adjust the steam distribution function" is displayed.

Images