阅读说明：本技术 一种汽轮机变背压特性试验的改进方法 (Improvement method for variable back pressure characteristic test of steam turbine ) 是由 邢乐强 薛志恒 王伟锋 吴涛 张朋飞 杜文斌 于 2021-09-18 设计创作，主要内容包括：本发明公开的一种汽轮机变背压特性试验的改进方法,包括以下步骤：按照汽轮机全面性热力性能试验方法,安装性能试验测点；进行热力系统隔离；在不同负荷工况下,调整机组背压,维持负荷稳定,收集试验数据,测定不同背压下的发电机电功率和热耗率；根据热力性能试验数据,将同一负荷点、不同背压工况下汽轮机进汽流量修正至相同值,然后通过热平衡计算对其他系统参数进行一类修正计算,再通过二类修正计算,获得各负荷点下背压变化对机组电功率和热耗率的影响量。本发明能够更加精确地评估机组背压变化对机组电功率和热耗率的影响量,从而为机组验收考核试验和冷端系统优化提供可靠的技术数据,进一步降低火电机组供电煤耗,提高发电厂经济效益。(The invention discloses an improvement method for a variable back pressure characteristic test of a steam turbine, which comprises the following steps: installing performance test points according to a comprehensive thermal performance test method of the steam turbine; isolating a thermodynamic system; under different load working conditions, adjusting the backpressure of the unit, maintaining the load stable, collecting test data, and measuring the electric power and heat consumption rate of the generator under different backpressure; according to the thermal performance test data, the steam inlet flow of the steam turbine at the same load point and under different backpressure working conditions is corrected to the same value, then one-class correction calculation is carried out on other system parameters through heat balance calculation, and then the influence quantity of backpressure change at each load point on the electric power and the heat consumption rate of the unit is obtained through two-class correction calculation. The method can more accurately evaluate the influence of the backpressure change of the unit on the electric power and the heat consumption rate of the unit, thereby providing reliable technical data for checking and accepting the unit and optimizing a cold end system, further reducing the power supply coal consumption of the thermal power unit and improving the economic benefit of a power plant.)

1. An improved method for testing the variable back pressure characteristic of a steam turbine is characterized by comprising the following steps;

A. b, mounting performance test points according to a comprehensive thermal performance test method of the steam turbine, and entering the step B;

B. referring to the requirements of ASME PTC6-2004 steam turbine performance test regulations, isolating a thermodynamic system, isolating the flow inconsistent with the designed thermal equilibrium diagram, measuring the flow of the valve and the pipeline which can not be isolated actually, and entering the step C;

C. under different load working conditions, adjusting the backpressure of the unit, maintaining the load stable, collecting test data, measuring the electric power and heat consumption rate of the generator under different backpressure, and entering the step D;

D. according to the thermal performance test data, performing a type of correction calculation: correcting the steam inlet flow of the steam turbine to the same value under the same load point and different backpressure working conditions, then correcting other system parameters through heat balance calculation to obtain a type of corrected electric power and heat consumption rate, and entering the step E;

E. performing second-class correction calculation on the electric power and the heat rate of each working condition, correcting the boundary conditions except the backpressure of the unit to design parameters, and entering the step F;

F. and obtaining the influence quantity of the backpressure change on the electric power and the heat consumption rate of the unit at each load point.

2. The improved method for testing the variable back pressure characteristic of the steam turbine according to claim 1, wherein in the step a, the comprehensive test method is a test method recommended by ASME PTC6-2004 "turbine performance test code", a main flow measuring device is installed on a main condensation water pipeline, and parameters such as low-pressure cylinder extraction pressure, low-pressure heater end difference, steam inlet pipeline pressure loss and the like need to be measured, so that the low-pressure cylinder exhaust flow, exhaust loss and low-pressure cylinder efficiency are further calculated.

3. The improved method for testing the variable back pressure characteristic of the steam turbine according to claim 1, wherein in the step D, the specific contents are as follows:

under different working conditions of the same load point, the back pressure p of the slave unit_b,1，p_b,2，p_b,3...p_b,nIn the above, the minimum value p is selected_b,minTaking the working condition corresponding to the minimum back pressure as a reference working condition, and correcting the working condition until the steam inlet flow of the steam turbine under the designed main steam pressure and main steam temperature is taken as a reference flow M_c,bThe actual steam inlet flow M of the steam turbine under the working condition 1 is calculated_m,1Correcting the steam inlet flow of the steam turbine to be M under the designed main steam pressure and main steam temperature_c,1：

Calculating a flow correction factor alpha₁I.e. M_c,1With reference flow rate M_c,bThe ratio of (A) to (B):

calculating new steam turbine inlet flow M under the working condition by using a formula (3)_m,1And M_c,1：

Then recalculate alpha₁If the cyclic variable ε₁＝|α₁The value of-1 |, is less than or equal to 0.001, the iterative computation is converged, and the computation is finished;

for other conditions, the iterative calculation makes the loop variable epsilon₂，ε₃...ε_nThe convergence condition is met, and a new type of corrected electric power and heat consumption rate under each working condition are obtained.

4. The improved method for testing the variable back pressure characteristic of the steam turbine as claimed in claim 1, wherein in the step E, the influence of the main steam pressure on the electric power and the heat rate of the unit under the load conditions except the 100% rated load condition is not considered.

5. The improvement method for the variable back pressure characteristic test of the steam turbine according to claim 1, wherein in the step F, the back pressure P of different units is obtained by calculation under each load working condition_b,iCorresponding corrected electric power P_c,iAnd heat rate HR_c,iCalculating the influence coefficient g of the back pressure on the electric power by using the formula (4) and the formula (5):

g＝average(g₁，g₂…g_n) (5)

likewise, the influence factor of the back pressure on the heat rate is calculated using equation (6) and equation (7):

f＝average(f₁，f₂…f_n) (7)。

Technical Field

The invention belongs to the technical field of power generation of a steam turbine of a thermal power generating unit, and particularly relates to an improvement method for a variable back pressure characteristic test of the steam turbine.

Background

In the daily operation process of the thermal power generating unit, the back pressure of the unit has very important influence on the output and the economy of the steam turbine, but for different parameters and different types of steam turbine generating units, the back pressure of the unit generates the same variation to cause different changes of electric power and heat consumption rate, so that the influence factors of the back pressure of the unit on the electric power and the heat consumption rate of the steam turbine need to be accurately obtained through a variable back pressure characteristic test. In addition, the influence of accurate back pressure change on the output and heat consumption rate of the steam turbine is required in the process of a steam turbine acceptance check test, a cold end system optimization test and a conventional steam turbine performance test of a new production unit.

The variable backpressure characteristic test requires that the steam turbine steam inlet flow is kept unchanged under a certain load working condition, thermal performance tests are carried out under different backpressure working conditions, and the electric power and the heat consumption rate of a unit are measured.

Disclosure of Invention

In order to overcome the technical problems, the invention provides an improved method for a variable back pressure characteristic test of a steam turbine, which can more accurately evaluate the influence quantity of the back pressure change of a unit on the electric power and the heat consumption rate of the unit, thereby providing reliable technical data for the unit acceptance check test and cold end system optimization, further reducing the power supply coal consumption of a thermal power unit and improving the economic benefit of a power plant.

In order to achieve the purpose, the invention adopts the technical scheme that:

an improved method for testing the variable back pressure characteristic of a steam turbine comprises the following steps;

A. according to the comprehensive thermal performance test method of the steam turbine, installing performance test points (mainly comprising reference flow, auxiliary flow, main steam parameters, reheated steam parameters, steam extraction parameters, water supply temperature, inlet and outlet parameters (including steam side and water side) of heaters at all levels, unit backpressure and generator power), and entering step B;

B. referring to the requirements of ASME PTC6-2004 steam turbine performance test regulations, isolating a thermodynamic system, isolating pipelines and flows which are inconsistent with a designed thermal equilibrium diagram, measuring the flows of the pipelines which can not be isolated actually, and entering a step C;

C. under different load working conditions, adjusting the backpressure of the unit, maintaining the load stable, collecting test data, measuring the electric power and heat consumption rate of the generator under different backpressure, and entering the step D;

D. according to the thermal performance test data, performing a type of correction calculation: correcting the steam turbine inlet steam flow under the same load point and different backpressure working conditions to the same value, then correcting other system parameters (including temperature reduction water flow, auxiliary steam flow, pressure loss of each stage of steam extraction pipelines, heater end difference, water level change of each water storage container, condensate supercooling degree and water feeding pump enthalpy rise) through heat balance calculation, obtaining a class of corrected electric power and heat consumption rate, and entering the step E;

E. performing second-class correction calculation on the electric power and the heat rate of each working condition, correcting boundary conditions (main steam pressure, main steam temperature, reheated steam temperature and reheater pressure loss) except for unit backpressure to design parameters, and entering step F;

F. and obtaining the influence quantity of the backpressure change on the electric power and the heat consumption rate of the unit at each load point.

In the step A, the comprehensive test method is a test method recommended by ASME PTC6-2004 steam turbine performance test regulations, the main flow measuring device is installed on a main condensation water pipeline, and parameters such as low-pressure cylinder extraction pressure, low-pressure heater end difference, steam inlet pipeline pressure loss and the like need to be measured, so that the low-pressure cylinder exhaust flow, exhaust loss and low-pressure cylinder efficiency are further calculated.

In the step D, the specific contents are as follows:

under different working conditions of the same load point, the back pressure p of the slave unit_b,1，p_b,2，p_b,3...p_b,nIn the above, the minimum value p is selected_b,minTaking the working condition corresponding to the minimum back pressure as a reference working condition, and correcting the working condition until the steam inlet flow of the steam turbine under the designed main steam pressure and main steam temperature is taken as a reference flow M_c,bThe actual steam inlet flow M of the steam turbine under the working condition 1 is calculated_m,1Correcting the steam inlet flow of the steam turbine to be M under the designed main steam pressure and main steam temperature_c,1：

Calculating a flow correction factor alpha₁I.e. M_c,1With reference flow rate M_c,bThe ratio of (A) to (B):

calculating new steam turbine inlet flow M under the working condition by using a formula (3)_m,1And M_c,1：

Then recalculate alpha₁If the cyclic variable ε₁＝|α₁The value of-1 |, is less than or equal to 0.001, the iterative computation is converged, and the computation is finished;

for other conditions, the iterative calculation makes the loop variable epsilon₂，ε₃...ε_nThe convergence condition is met, and a new type of corrected electric power and heat consumption rate under each working condition are obtained.

In the step E, the influence of the main steam pressure on the electric power and the heat rate of the unit under other load conditions except the 100% rated load condition is not considered.

In the step F, calculating to obtain the back pressures P of different units under each load working condition_b,iCorresponding corrected electric power P_c,iAnd heat rate HR_c,iCalculating the influence coefficient g of the back pressure on the electric power by using the formula (4) and the formula (5):

g＝average(g₁，g₂...g_n) (5)

likewise, the influence factor of the back pressure on the heat rate is calculated using equation (6) and equation (7):

f＝average(f₁，f₂...f_n) (7)。

the invention has the beneficial effects that:

the influence of steam turbine steam inlet flow deviation on the electric power and heat consumption rate of the unit is considered in the test process, and the influence of the backpressure change of the unit on the electric power and heat consumption rate of the unit can be more accurately evaluated through correction calculation, so that reliable technical data are provided for unit acceptance check tests and cold end system optimization, the power supply coal consumption of the thermal power unit is further reduced, and the economic benefit of a power plant is improved.

Drawings

FIG. 1 is a schematic flow chart of the present invention.

FIG. 2 is a comprehensive back pressure characteristic test point layout diagram.

FIG. 3 is a logic diagram of a steam turbine inlet flow correction calculation.

Detailed Description

The present invention will be described in further detail with reference to examples.

As shown in fig. 1, the present invention provides an improved method for testing the variable back pressure characteristic of a steam turbine, which comprises the following steps:

1) according to the comprehensive thermal performance test method of the steam turbine, performance test points (mainly comprising reference flow, auxiliary flow, main steam parameters, reheated steam parameters, steam extraction parameters, water supply temperature, inlet and outlet parameters (including steam side and water side) of heaters at all levels, unit backpressure and generator power) are installed. The specific location is shown in figure 2.

2) And (4) performing thermodynamic system isolation according to the requirements of ASME PTC6-2004 steam turbine performance test regulations.

3) Under different load working conditions, the backpressure of the unit is adjusted, the load stability is maintained, test data are collected, and the electric power and the heat consumption rate of the generator under different backpressure are measured.

4) According to the thermal performance test data, performing a type of correction calculation: the steam turbine inlet steam flow under the same load point and different backpressure working conditions is corrected to the same value, and then other system parameters (including temperature reduction water flow, auxiliary steam flow, pressure loss of each stage of steam extraction pipelines, heater end difference, water level change of each water storage container, condensate supercooling degree and enthalpy rise of a water feeding pump) are corrected through heat balance calculation, so that the electric power and heat consumption rate after the first class of correction are obtained.

5) And performing two types of correction calculation on the electric power and the heat rate of each working condition, and correcting boundary conditions (main steam pressure, main steam temperature, reheat steam temperature and reheater pressure loss) except for the unit backpressure to design parameters.

6) And obtaining the influence quantity of the backpressure change on the electric power and the heat consumption rate of the unit at each load point.

Examples illustrate that:

fig. 2 is a layout diagram of the testing points required for a typical 1000MW ultra supercritical, wet and cold steam turbine generator set to perform a comprehensive back pressure characteristic test. The reference flow of the test is determined by the flow of the condensate entering the deaerator, and the flow measuring device is a low beta ratio long-diameter throat pressure-taking flow nozzle. Before the variable back pressure characteristic test, performance test points are installed according to the layout chart and the effectiveness of the performance test points is tested.

And (3) according to the requirements of ASME PTC6-2004 steam turbine performance test regulations, isolating the thermodynamic system, and according to a unit thermodynamic system diagram and the field condition, isolating the flow rate inconsistent with the design thermal equilibrium diagram as much as possible, so that the unit thermodynamic system is circularly operated according to the design thermal equilibrium diagram. The pipeline to be isolated mainly comprises a starting bypass system, an auxiliary steam pipeline, a water spraying temperature reduction device, a valve drainage pipeline, a steam pipeline drainage device, a heater bypass, a heater water drain device, a heater exhaust device, a boiler soot blowing device, a condenser water supply pipeline and a water feeding pump steam turbine auxiliary steam source.

The variable back pressure characteristic test is carried out under 1000MW, 750MW and 500MW load working conditions, test data are collected under 3 different back pressures of each load working condition, and the specific working condition is shown in the following table.

TABLE 1 backpressure characteristic test condition table

And calculating the heat rate and the low-pressure cylinder efficiency under each working condition according to the collected test data, and then performing a type of correction calculation, wherein the steam inlet flow correction calculation process of the steam turbine is shown in fig. 3. The experimental calculation results for each condition under 1000MW, 750MW and 500MW loads are shown in Table 2, Table 3 and Table 4.

Table 21000 MW load under each working condition calculation result

TABLE 3750 MW load calculation results for each operating mode

TABLE 4500 MW load calculation

According to the test data, the following conclusion is calculated: under the 1000MW load working condition, the electric power of the unit is reduced by about 0.67 percent when the exhaust steam pressure is increased by 1 kPa; under the working condition of 750MW load, the electric power of the unit is reduced by about 0.93% when the exhaust steam pressure is increased by 1 kPa; under the 500MW load working condition, the electric power of the unit is reduced by about 1.51% when the exhaust steam pressure is increased by 1 kPa;

the drawings are only for purposes of illustrating the invention and are not to be construed as limiting the scope of the invention, which is intended to be covered by the claims, since certain insubstantial modifications and adaptations of the invention may occur to those skilled in the art in light of the foregoing description.