Method for distinguishing the power of steam turbine and gas turbine in single-shaft combined cycle generator set

Abstract

A method for distinguishing the power of a steam turbine and a gas turbine in a single-shaft combined cycle generator set. In actual engineering applications, only four parameters, namely, the total power of the unit, the steam turbine's steam inlet pressure, the steam inlet temperature, and the exhaust back pressure, need to be used to distinguish the power of the steam turbine and the gas turbine by consulting the steam turbine characteristic curve obtained by experiment. This method avoids a large amount of complex theoretical calculations and does not require higher theoretical foundations of engineers. Moreover, the steam turbine characteristic curve can be corrected through performance tests after each unit overhaul, thus avoiding calculation deviations caused by reasons such as unit performance aging, and facilitating engineering applications.

Description

Technical Field

[0001] The present invention relates to the field of single-shaft combined cycle generator sets, and in particular to a method for distinguishing the power of a steam turbine and a gas turbine of a single-shaft combined cycle generator set. Background Art

[0002] The gas turbine, steam turbine and generator set of a single-shaft combined cycle generator set are connected in series on the same shaft system. The gas turbine and steam turbine share a generator, and the output power of the generator is the sum of the output power of the gas turbine and steam turbine.

[0003] Accurately distinguishing gas turbine power from steam turbine power is of practical significance for unit performance analysis and diagnosis. Well-known foreign heavy-duty gas turbine manufacturers have embedded gas turbine and steam turbine power calculation modules in the control systems of their single-shaft combined cycle units.

[0004] The performance of gas and steam turbines inevitably changes over time. However, the parameters of the gas and steam turbine power calculation modules pre-installed in the control system by manufacturers are fixed. As a result, there is a discrepancy between the module's calculated results and the actual power, and this discrepancy increases over time. Because manufacturers maintain confidentiality regarding the calculation models for gas and steam turbines, users are unable to adjust the module's parameters. Therefore, it is necessary to develop a more practical and adaptable method for calculating gas and steam turbine power that is more suitable for engineering applications. Summary of the Invention

[0005] In order to overcome the deficiencies of the above technologies, the present invention provides a method for obtaining a characteristic curve of a steam turbine through experiments and obtaining the steam turbine power under actual operating conditions of a combined cycle unit using the characteristic curve.

[0006] The technical solution adopted by the present invention to overcome the technical problems is:

[0007] A method for distinguishing the power of a steam turbine and a gas turbine in a single-shaft combined cycle generator set comprises the following steps: a) stabilizing the full load of the unit, measuring the relevant parameters of the fuel and the air compressor intake air in accordance with the relevant requirements of the "GB / T14100-2016 Gas Turbine Acceptance Test", calculating the composition, enthalpy and energy of the gas turbine exhaust in accordance with the "DL / T1427-2015 Combined Cycle Waste Heat Boiler Performance Test Procedure", and obtaining the energy carried by the exhaust gas of the waste heat boiler through the flow balance and energy balance of the waste heat boiler, obtaining the exhaust enthalpy of the steam turbine through the energy balance calculation of the unit, and calculating the exhaust enthalpy of the steam turbine according to the actual The relative internal efficiency of the steam turbine is calculated using the measured steam turbine inlet temperature, pressure, exhaust pressure, and exhaust enthalpy. The saturated enthalpy, saturated specific volume, dry saturated enthalpy, and dry saturated specific volume of the steam turbine exhaust are obtained by looking up the enthalpy-entropy diagram based on the measured steam turbine exhaust pressure. The exhaust dryness of the steam turbine is obtained using the steam turbine exhaust enthalpy, saturated enthalpy, and dry saturated enthalpy. The exhaust specific volume of the steam turbine is then obtained using the steam turbine exhaust dryness, saturated specific volume, and dry saturated specific volume. The exhaust volumetric flow rate of the steam turbine is obtained by multiplying the exhaust specific volume of the steam turbine by the exhaust flow rate of the steam turbine.

[0008] b) The steam flow rate of the steam turbine is calculated by subtracting the steam leakage rate of the steam turbine gate rod and the steam leakage rate of the steam turbine front shaft seal from the steam production of the waste heat boiler. The characteristic flow area Fv of the steam turbine is calculated;

[0009] c) Stable unit load P e , changing the exhaust pressure of the steam turbine, repeating step a), obtaining the exhaust enthalpy and exhaust volume flow rate of the steam turbine and the corresponding relative internal efficiency of the steam turbine under different steam turbine exhaust pressures at the same load;

[0010] d) Steam turbine exhaust pressure P K is the independent variable, corresponding to the steam turbine exhaust volume flow FLOW V As the dependent variable, through the formula FLOW V =a·P K 2 +b·P K +c to get the fitting function, where a, b, and c are coefficients;

[0011] e) From the full load to the minimum load of the unit, change the load of the unit in sequence, repeat steps a) to d) n times, and obtain the fitting function FLOW under different loads Vi =a i ·P K 2 +b i ·P K +c i ,FLOW Vi is the fitting function after the i-th repetition, ai 、b i 、c i are the coefficients of the i-th repetition, i={1,2,...,n};

[0012] f) Take the unit load value P e As the independent variable, the fitting coefficients a, b, and c are taken as the dependent variables, and the fitting function is obtained. Among them, A2, A1, and A0 are quadratic polynomial fitting coefficients, B2, B1, and B0 are quadratic polynomial fitting coefficients, and C2, C1, and C0 are quadratic polynomial fitting coefficients;

[0013] g) Taking the relative internal efficiency η of the steam turbine as the dependent variable, the steam turbine exhaust volume flow FLOW under the corresponding operating conditions V As the independent variable, through the formula η=k2·FLOW V 2 +k1·FLOW V +k0 to get the fitting function, where k2, k1, and k0 are quadratic polynomial fitting coefficients;

[0014] h) Calculate the correction coefficient ξ of the characteristic flow area under different loads, taking the correction coefficient ξ of the characteristic flow area under each load as the dependent variable and the steam turbine inlet steam volume under the corresponding load as the independent variable through the formula ξ=K2·v0 2 +K1·v0+K0 fitting function, where v0 is the steam turbine inlet steam specific volume, K2, K1, and K0 are quadratic polynomial fitting coefficients;

[0015] i) Calculate the steam turbine flow rate G;

[0016] j) The shaft power of the steam turbine is calculated by combining the steam turbine flow rate G and the relative internal efficiency of the steam turbine with the measured steam turbine inlet and exhaust parameters. The shaft power of the gas turbine is obtained by dividing the operating load value of the combined cycle power generation unit by the electromechanical efficiency of the unit and then subtracting the steam turbine shaft power.

[0017] Furthermore, in step b), the formula The characteristic flow area Fv of the steam turbine is calculated, where G is the flow rate of the steam turbine, p0 is the steam turbine inlet steam pressure, v0 is the steam turbine inlet steam specific volume, and π is the ratio of the steam turbine exhaust pressure to the steam inlet pressure.

[0018] Furthermore, in step h), the formula ξ=F vn / Fv calculation to get the correction coefficient ξ, where F vn is the characteristic flow area of ​​the steam turbine under partial load.

[0019] Furthermore, through the formula The steam turbine flow rate G is calculated. The beneficial effects of the present invention are as follows: in actual engineering applications, only four parameters, namely, the total power of the unit, the steam turbine inlet pressure, the steam turbine inlet temperature, and the exhaust back pressure, need to be used to refer to the steam turbine characteristic curve obtained by the test to distinguish the power of the steam turbine from that of the gas turbine, thereby avoiding a large amount of complex theoretical calculations and not requiring higher theoretical foundations of engineers. Moreover, the steam turbine characteristic curve can be corrected through each performance test after the unit overhaul, thereby avoiding calculation deviations caused by reasons such as unit performance aging, and facilitating engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the principle of the single-shaft combined cycle generator set of the present invention. DETAILED DESCRIPTION

[0021] The following is combined with Figure 1 The present invention is further described.

[0022] The present invention is to solve the above-mentioned problem and proposes a more suitable method for calculating the power of steam turbines and gas turbines. This method obtains the characteristic curve of the steam turbine through experiments, and uses the characteristic curve to obtain the steam turbine power under the actual operating conditions of the combined cycle unit. The power of the gas turbine is obtained by subtracting the power of the steam turbine from the total power of the combined cycle unit. The gas turbine in the combined cycle unit can adopt a simple cycle, a complex cycle or a combination of multiple complex cycles. The steam-water system of the waste heat boiler matched with the gas turbine can adopt a single-pressure, double-pressure or triple-pressure steam-water system. The correspondingly configured steam turbine can be a single-cylinder, double-cylinder or three-cylinder steam turbine. As shown in the attached figure Figure 1 As shown, in order to highlight the key points, the calculation method of the present invention is explained by taking a simple cycle of a gas turbine matched with a single-pressure waste heat boiler and a single-cylinder condensing steam turbine as an example.

[0023] The specific steps include:

[0024] a) Stabilize the full load of the unit, measure the relevant parameters of fuel and air compressor intake air in accordance with the relevant requirements of "GB / T14100-2016 Gas Turbine Acceptance Test", calculate the composition, enthalpy and energy of gas turbine exhaust in accordance with "DL / T1427-2015 Combined Cycle Waste Heat Boiler Performance Test Procedure", and obtain the energy carried by the exhaust gas of the waste heat boiler through the flow balance and energy balance of the waste heat boiler. Calculate the exhaust enthalpy of the steam turbine through the energy balance calculation of the unit. According to the measured steam turbine inlet temperature, pressure and exhaust pressure, calculate the exhaust enthalpy of the steam turbine. The relative internal efficiency of the steam turbine is calculated based on the actual exhaust pressure of the steam turbine and the exhaust enthalpy. The saturated enthalpy, saturated specific volume, dry saturated enthalpy and dry saturated specific volume of the steam turbine exhaust are obtained by looking up the enthalpy-entropy diagram according to the measured exhaust pressure of the steam turbine. The exhaust dryness of the steam turbine is obtained by using the exhaust enthalpy of the steam turbine, the saturated specific volume of the steam turbine exhaust and the dry saturated specific volume. The exhaust specific volume of the steam turbine is obtained by multiplying the exhaust specific volume of the steam turbine by the exhaust flow rate of the steam turbine.

[0025] The calculation methods in the above steps are all conventional algorithms in the prior art and will not be described in detail here.

[0026] b) The steam flow rate of the steam turbine is calculated by subtracting the steam leakage of the steam turbine's gate rod and the steam leakage of the steam turbine's front shaft seal from the steam production of the waste heat boiler. The characteristic flow area Fv of the steam turbine is then calculated.

[0027] c) Stable unit load P e , change the exhaust pressure of the steam turbine, repeat step a), and obtain the exhaust enthalpy value and exhaust volume flow rate of the steam turbine and the corresponding relative internal efficiency of the steam turbine under different steam turbine exhaust pressures at the same load.

[0028] d) Steam turbine exhaust pressure P K is the independent variable, corresponding to the steam turbine exhaust volume flow FLOW V As the dependent variable, through the formula FLOW V =a·P K 2 +b·P K + c to obtain the fitting function, where a, b, and c are coefficients. This function can determine the exhaust volume flow rate corresponding to different exhaust pressures under the same load.

[0029] e) From the full load to the minimum load of the unit, change the load of the unit in sequence, repeat steps a) to d) n times, and obtain the fitting function FLOW under different loads Vi =a i ·P K 2 +b i ·P K +ci ,FLOW Vi is the fitting function after the i-th repetition, a i 、b i 、c i are the coefficients for the i-th repetition, i = {1, 2, ..., n}. Thus, a set of functions for the exhaust volume flow rate corresponding to different exhaust pressures under various loads is obtained.

[0030] f) Take the unit load value P e As the independent variable, the fitting coefficients a, b, and c are taken as the dependent variables, and the fitting function is obtained. Among them, A2, A1, and A0 are quadratic polynomial fitting coefficients, B2, B1, and B0 are quadratic polynomial fitting coefficients, and C2, C1, and C0 are quadratic polynomial fitting coefficients.

[0031] g) Taking the relative internal efficiency η of the steam turbine as the dependent variable, the steam turbine exhaust volume flow FLOW under the corresponding operating conditions V As the independent variable, through the formula η=k2·FLOW V 2 +k1·FLOW V +k0 to obtain the fitting function, where k2, k1, and k0 are quadratic polynomial fitting coefficients.

[0032] h) Calculate the correction coefficient ξ of the characteristic flow area under different loads, taking the correction coefficient ξ of the characteristic flow area under each load as the dependent variable and the steam turbine inlet steam volume under the corresponding load as the independent variable through the formula ξ=K2·v0 2 +K1·v0+K0 fitting function, where v0 is the steam turbine inlet steam specific volume, and K2, K1, and K0 are quadratic polynomial fitting coefficients.

[0033] Through the above steps a) to h), a method for calculating steam turbine power can be obtained: Substitute the operating load value into each function obtained in step 6 to calculate the a required under the operating load. i 、b i 、c i The value of , and then get the function FLOW of exhaust volume flow corresponding to different exhaust pressures under operating load Vi =a i ·P K 2 +b i ·P K +c i Substitute the exhaust pressure value of the steam turbine under the operating load into the function to obtain the exhaust volume flow rate of the steam turbine under the operating load, and substitute the calculated exhaust volume flow rate value into the fitting function η=k2·FLOW in step g). V 2+k1·FLOW V The relative internal efficiency of the steam turbine under the steam load under the operating load is obtained from the equation ξ = K2·v0, and the intake volume of the steam turbine under the operating load is substituted into the fitting function ξ = K2·v0 in step h). 2 +K1·v0+K0, the correction coefficient ξi) under this operating condition is obtained to calculate the steam turbine flow rate G.

[0034] j) The shaft power of the steam turbine is calculated by combining the steam turbine flow rate G and the relative internal efficiency of the steam turbine with the measured steam turbine inlet and exhaust parameters. The shaft power of the gas turbine is obtained by dividing the operating load value of the combined cycle power generation unit by the electromechanical efficiency of the unit and then subtracting the steam turbine shaft power.

[0035] The present invention provides a new method for calculating the steam turbine power and gas turbine power of a single-shaft combined cycle generator set. In actual engineering applications, only four parameters, namely, the total power of the unit, the steam turbine inlet pressure, the steam inlet temperature, and the exhaust back pressure, need to be used to distinguish the power of the steam turbine from that of the gas turbine by consulting the characteristic curve of the steam turbine obtained through the test. This avoids a large number of complex theoretical calculations and does not place higher requirements on the theoretical foundation of engineers. Moreover, the characteristic curve of the steam turbine can be corrected through performance tests after each unit overhaul, thus avoiding calculation deviations caused by reasons such as aging of the unit performance and facilitating engineering applications. Specifically, in step b), the formula The characteristic flow area Fv of the steam turbine is calculated, where G is the flow rate of the steam turbine, p0 is the steam turbine inlet steam pressure, v0 is the steam turbine inlet steam specific volume, and π is the ratio of the steam turbine exhaust pressure to the steam inlet pressure.

[0036] Specifically, in step h), the formula ξ=F vn / Fv calculation to get the correction coefficient ξ, where F vn is the characteristic flow area of ​​the steam turbine under partial load.

[0037] Specifically, through the formula The steam turbine flow rate G is calculated. Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalent features for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for distinguishing the power of a steam turbine and a gas turbine in a single-shaft combined cycle generator set, characterized in that: The steps include: a) Stabilize the unit at full load, measure the relevant parameters of fuel and air compressor intake, calculate the composition, enthalpy and energy of gas turbine exhaust, calculate the steam turbine exhaust enthalpy, calculate the relative internal efficiency of the steam turbine, and calculate the steam turbine exhaust volume flow rate; b) The steam flow rate of the steam turbine is calculated by subtracting the steam leakage rate of the steam turbine gate rod and the steam leakage rate of the steam turbine front shaft seal from the steam production of the waste heat boiler. The characteristic flow area Fv of the steam turbine is calculated; c) Stable unit load P e , changing the exhaust pressure of the steam turbine, repeating step a), obtaining the exhaust enthalpy and exhaust volume flow rate of the steam turbine and the corresponding relative internal efficiency of the steam turbine under different steam turbine exhaust pressures at the same load; d) Steam turbine exhaust pressure P K is the independent variable, corresponding to the steam turbine exhaust volume flow FLOW V As the dependent variable, through the formula FLOW V =a·P K 2 +b·P K +c to get the fitting function, where a, b, and c are coefficients; e) From the full load to the minimum load of the unit, change the load of the unit in sequence, repeat steps a) to d) n times, and obtain the fitting function FLOW under different loads Vi =a i ·P K 2 +b i ·P K +c i ,FLOW Vi is the fitting function after the i-th repetition, a i 、b i 、c i are the coefficients of the i-th repetition, i={1,2,...,n}; f) Take the unit load value P e As the independent variable, the fitting coefficients a, b, and c are taken as the dependent variables, and the fitting function is obtained. Among them, A2, A1, and A0 are quadratic polynomial fitting coefficients, B2, B1, and B0 are quadratic polynomial fitting coefficients, and C2, C1, and C0 are quadratic polynomial fitting coefficients; g) Taking the relative internal efficiency η of the steam turbine as the dependent variable, the steam turbine exhaust volume flow FLOW under the corresponding operating conditions V As the independent variable, through the formula η=k2·FLOW V 2 +k1·FLOW V +k0 to get the fitting function, where k2, k1, and k0 are quadratic polynomial fitting coefficients; h) Calculate the correction coefficient ξ of the characteristic flow area under different loads, taking the correction coefficient ξ of the characteristic flow area under each load as the dependent variable and the steam turbine inlet steam volume under the corresponding load as the independent variable through the formula ξ=K2·v0 2 +K1·v0+K0 fitting function, where v0 is the steam turbine inlet steam specific volume, K2, K1, and K0 are quadratic polynomial fitting coefficients; i) Calculate the steam turbine flow rate G; j) The shaft power of the steam turbine is calculated by combining the steam turbine flow rate G and the relative internal efficiency of the steam turbine with the measured steam turbine inlet and exhaust parameters. The shaft power of the gas turbine is obtained by dividing the operating load value of the combined cycle power generation unit by the electromechanical efficiency of the unit and then subtracting the steam turbine shaft power.

2. The method for distinguishing the power of a steam turbine and a gas turbine of a single-shaft combined cycle generator set according to claim 1, characterized in that: In step b), the formula The characteristic flow area Fv of the steam turbine is calculated, where G′ is the flow rate of the steam turbine before correction, p0 is the steam turbine inlet steam pressure, v0 is the steam turbine inlet steam specific volume, and π is the ratio of the steam turbine exhaust pressure to the steam inlet pressure.

3. The method for distinguishing the power of a steam turbine and a gas turbine of a single-shaft combined cycle generator set according to claim 1, characterized in that: In step h), the formula ξ=F vn / Fv calculation to get the correction coefficient ξ, where F vn is the characteristic flow area of ​​the steam turbine under partial load.

4. The method for distinguishing the power of a steam turbine and a gas turbine of a single-shaft combined cycle generator set according to claim 3, characterized in that: By formula The steam turbine flow rate G is calculated.

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