阅读说明：本技术 一种汽轮机低压缸鼓风监测位置的确定方法 (Method for determining blast monitoring position of low-pressure cylinder of steam turbine ) 是由 屈杰 高庆 朱蓬勃 居文平 马汀山 高登攀 张永海 谷伟伟 曾立飞 潘渤 祁文玉 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种汽轮机低压缸鼓风监测位置的确定方法,本发明通过计算流体动力学的方法对汽轮机低压流动区进行湍流流动换热分析,可以更加透彻的了解小容积流量下低压通流区域的流动状况,通过分析不同进汽流量工况及不同叶高位置叶栅通道的速度矢量分布、温度分布以及压力分布,可以得到精准的得到低压通流区的鼓风发热高温区坐标,并对鼓风温升进行定量分析,能够精准地对鼓风发热温升进行评估,对保障火电机组常态化调峰运行的安全性具有重大的意义。(The invention discloses a method for determining a blast monitoring position of a low-pressure cylinder of a steam turbine, which is used for carrying out turbulent flow heat exchange analysis on a low-pressure flow area of the steam turbine by a computational fluid dynamics method, so that the flow condition of the low-pressure flow area under small volume flow can be known more thoroughly, the coordinates of a blast heating high-temperature area in the low-pressure flow area can be obtained accurately by analyzing the speed vector distribution, the temperature distribution and the pressure distribution of cascade channels at different steam inlet flow working conditions and different blade height positions, the blast heating temperature rise can be quantitatively analyzed, the blast heating temperature rise can be evaluated accurately, and the method has great significance for ensuring the safety of the normalized peak regulation operation of a thermal power unit.)

1. A method for determining a blowing monitoring position of a low-pressure cylinder of a steam turbine is characterized by comprising the following steps:

step one, establishing a full-circle multi-stage model of a low-pressure through-flow area according to a drawing according to a real through-flow structure of a low-pressure cylinder of a steam turbine;

step two, carrying out grid planning on the fluid calculation domain of the full-circle multi-level model in the low-pressure through-flow area to generate a plurality of structured grids;

determining the boundary condition of a fluid calculation model of the low-pressure final-stage flow area;

solving a Navier-Stokes equation set during Reynolds through the numerical value of a flow solver, and introducing a Boussinesq turbulence model hypothesis to seal the Navier-Stokes equation set during Reynolds calculation for turbulence;

solving the equation set in the step four to obtain a converged multi-working-condition flow calculation analysis result, and analyzing to obtain velocity vector distribution, temperature distribution and pressure distribution in the blade grid channels at different steam inlet flow working conditions and different blade height positions;

and sixthly, analyzing the velocity vector distribution, the temperature distribution and the pressure distribution of the flow area, finding out a blowing highest temperature area and a flow stable area, and determining the installation position of the low-pressure cylinder blowing monitoring sensor.

2. The method for determining the position of monitoring the air blowing of the low-pressure cylinder of the steam turbine according to claim 1, wherein in the step one, the static rotating parts in the full-circle multi-stage model of the low-pressure through-flow area are respectively arranged in a static calculation domain and a rotating calculation domain according to the physical boundary of the full-circle multi-stage model of the low-pressure through-flow area.

3. The method for determining the blowing monitoring position of the low pressure cylinder of the steam turbine as claimed in claim 1, wherein in the second step, the maximum aspect ratio of the calculation grid is less than 30, and the orthogonal angles are all more than 45 degrees.

4. The method for determining the blast monitoring position of the low-pressure cylinder of the steam turbine according to claim 1, wherein in the second step, when a plurality of pieces of structured grids are generated, the grids are encrypted on the wall surface so as to meet the requirement of Y + < 1; when a plurality of structured grids are generated, O-shaped skin grids are arranged on the surfaces of the circulating stage moving and static blades, and H-shaped grids are arranged at the inlet and outlet extension sections of the main runner.

5. The method for determining the position of monitoring the blowing of the low-pressure cylinder of the steam turbine as claimed in claim 1, wherein in the third step, the boundary conditions are set according to the boundary of the main flow inlet of the low-pressure cylinder, the static pressure boundary is set at the outlet of the steam exhaust guide ring of the low-pressure cylinder, the rotating speed is set in the rotating field, the mixed surface model is set at the dynamic and static interface, and the rest solid wall surfaces are set to be smooth and adiabatic.

6. The method for determining the blowing monitoring position of the low-pressure cylinder of the steam turbine as claimed in claim 1, wherein in the fourth step, the specific form of the Navier-Stokes equation group at the time of Reynolds is as follows:

in the formula: the index value ranges of i and j are 1-3, rho is density, S_MAs source terms of momentum equations, S_EFor the source terms of the energy equation, τ is the tensor of shear stress,in order to take the Reynolds stress term into account,in order to be a turbulent flux, the flow,a work term for stickiness.

7. The method for determining the blowing monitoring position of the low-pressure cylinder of the steam turbine as claimed in claim 6, wherein in the fourth step, the Boussinesq turbulence model in the fourth step is in the following specific form:

in the formula: mu.s_effIs effectively adhesive.

8. The method for determining the blowing monitoring position of the low-pressure cylinder of the steam turbine as claimed in claim 1, wherein in the fourth step, the discrete format of the solver is a high-precision second-order-difference cellular format.

9. The method for determining the blowing monitoring position of the low-pressure cylinder of the steam turbine according to claim 1, wherein in the fifth step, the multi-working-condition flow calculation analysis results comprise the meridional velocity vector distribution, the meridional temperature distribution and the pressure distribution of the low-pressure through-flow area under different steam inlet flow conditions, the velocity vector distribution, the temperature distribution and the pressure distribution in the cascade channel at the blade height of 10-90%, and the absolute values of the physical quantities of the pressure, the temperature and the velocity value at the grid node in the calculation domain.

10. The method for determining the blowing monitoring position of the low-pressure cylinder of the steam turbine according to claim 1, wherein in the sixth step, the coordinate position of the grid node with the highest temperature value of the low-pressure through-flow area is the mounting position of the blowing temperature monitoring sensor.

Technical Field

The invention belongs to the field of thermal power generation, and particularly relates to a method for determining a blast monitoring position of a low-pressure cylinder of a steam turbine.

Background

With the increase of global energy demand and the emergence of environmental problems, the proportion of renewable energy in energy structures needs to be improved urgently. In consideration of the fact that the installed capacity of new energy is rapidly increased in recent years, the thermal power generating unit needs flexible deep peak shaving to meet and solve the problem of consumption of renewable energy in a power system, and new challenges are provided for adjustment of the operation mode of the thermal power generating unit.

The steam inlet flow of the thermal power generating unit is reduced along with the reduction of the load rate of the thermal power generating unit in the deep peak shaving of the thermal power generating unit, so that the thermal power generating turbine works under the working condition of small volume flow. With the further reduction of the steam inlet flow, the flow form of the low-pressure through-flow area of the steam turbine is changed, the air flow does not push the blades to do work any more, but the air flow is extruded out of the blade channel by the blade fan row in an inert form, and the blowing phenomenon is realized. The blast friction phenomenon can lead to the steam turbine blade cascade passageway local high temperature region that appears, and serious person will make the inner casing thermal deformation, influences the central uniformity of quiet part, and then can threaten the safe operation of unit.

Therefore, in the low-pressure through-flow area of the steam turbine, the position of the highest blast temperature area under the working condition of small-capacity flow is reasonably determined and monitored, the blast heating temperature rise is accurately evaluated, and the method has great significance for guaranteeing the safety of the normalized peak regulation operation of the thermal power unit.

Disclosure of Invention

The invention aims to overcome the defects and provides a method for determining the blast monitoring position of the low-pressure cylinder of the steam turbine.

In order to achieve the above object, the present invention comprises the steps of:

step one, establishing a full-circle multi-stage model of a low-pressure through-flow area according to a drawing according to a real through-flow structure of a low-pressure cylinder of a steam turbine;

step two, carrying out grid planning on the fluid calculation domain of the full-circle multi-level model in the low-pressure through-flow area to generate a plurality of structured grids;

determining the boundary condition of a fluid calculation model of the low-pressure final-stage flow area;

solving a Navier-Stokes equation set during Reynolds through the numerical value of a flow solver, and introducing a Boussinesq turbulence model hypothesis to seal the Navier-Stokes equation set during Reynolds calculation for turbulence;

solving the equation set in the step four to obtain a converged multi-working-condition flow calculation analysis result, and analyzing to obtain velocity vector distribution, temperature distribution and pressure distribution in the blade grid channels at different steam inlet flow working conditions and different blade height positions;

and sixthly, analyzing the velocity vector distribution, the temperature distribution and the pressure distribution of the flow area, finding out a blowing highest temperature area and a flow stable area, and determining the installation position of the low-pressure cylinder blowing monitoring sensor.

In the first step, the static rotating components in the low-pressure through-flow area full-circle multi-level model are respectively arranged in static and rotary calculation domains according to the physical boundary of the low-pressure through-flow area full-circle multi-level model.

In the second step, the maximum aspect ratio of the calculation grid is less than 30, and the orthogonal angles are all larger than 45 degrees.

In the second step, when a plurality of structured grids are generated, the grid encryption is carried out on the wall surface so as to meet the requirement of Y + < 1; when a plurality of structured grids are generated, O-shaped skin grids are arranged on the surfaces of the circulating stage moving and static blades, and H-shaped grids are arranged at the inlet and outlet extension sections of the main runner.

In the third step, the boundary condition is set according to the boundary of the main flow inlet of the low pressure cylinder inlet, the static pressure boundary is set at the outlet of the low pressure cylinder exhaust steam guide ring, the rotating speed is set in the rotating domain, the mixed surface model is set at the dynamic and static interface, and the other solid wall surfaces are set to be smooth and heat-insulating conditions.

In the fourth step, the specific form of the Navier-Stokes equation set at Reynolds time is as follows:

in the formula: the index value ranges of i and j are 1-3, rho is density, S_MAs source terms of momentum equations，S_EFor the source terms of the energy equation, τ is the tensor of shear stress,in order to take the Reynolds stress term into account,in order to be a turbulent flux, the flow,a work term for stickiness.

In step four, the specific form of the Boussinesq turbulence model in step four is as follows:

in the formula: mu.s_effIs effectively adhesive.

In the fourth step, the discrete format of the solver is a high-precision second-order-difference cellular format.

And fifthly, calculating and analyzing results of the multi-working-condition flow, wherein the results comprise meridional plane velocity vector distribution, meridional plane temperature distribution and pressure distribution of the low-pressure through-flow area under different steam inflow flow conditions, velocity vector distribution, temperature distribution and pressure distribution in a cascade channel at the position of 10-90% of the blade height, and physical quantity absolute values of pressure, temperature and velocity values at grid nodes in the calculation domain.

And step six, the coordinate position of the grid node with the highest temperature value of the low-pressure through-flow area is the mounting position of the blast temperature monitoring sensor.

Compared with the prior art, the turbulent flow heat exchange analysis is carried out on the low-pressure flow area of the steam turbine by a computational fluid dynamics method, the flow condition of the low-pressure through-flow area under small volume flow can be known more thoroughly, the coordinates of the blast heating high-temperature area in the low-pressure through-flow area can be obtained accurately by analyzing the speed vector distribution, the temperature distribution and the pressure distribution of the cascade channels at different steam inlet flow working conditions and different blade height positions, the blast heating temperature rise can be quantitatively analyzed, the blast heating temperature rise can be accurately evaluated, and the method has great significance for guaranteeing the safety of the normalized peak regulation operation of the thermal power unit.

Drawings

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

FIG. 2 is a diagram of a grid model according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a meridian temperature field calculation result of a low-pressure flow area under 2.5% THA working condition in an embodiment of the invention;

FIG. 4 is a schematic diagram of a pressure field calculation result in a blade cascade channel with 2.5% THA working condition and 90% blade height according to an embodiment of the invention;

FIG. 5 is a schematic diagram of the calculation result of the velocity field in the cascade channel with 2.5% THA working condition and 90% blade height according to the embodiment of the invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1, the present invention comprises the steps of:

the method comprises the steps of firstly, establishing a full-circle multi-stage model of a low-pressure flow area by referring to a real flow structure of a low-pressure cylinder of the steam turbine through three-dimensional modeling software according to a geometric drawing, generating a model fluid calculation domain through fluid analysis software, and respectively arranging static rotating components in the model in static and rotary calculation domains according to actual physical boundaries of the model.

And step two, carrying out grid planning on the fluid calculation domain by adopting commercial software to generate a plurality of structured grids, wherein the calculated grids need to meet the technical requirements that the maximum length-width ratio is less than 30 and the orthogonal angles are all more than 45 degrees so as to ensure better orthogonality. When the grids are generated, the grids are encrypted on the wall surface to meet the requirement of Y⁺<1, requirement of; when the grids are generated, O-shaped attached grids are arranged on the surfaces of the movable and stationary blades of the through-flow stage, and H-shaped grids are arranged at the inlet and outlet extension sections of the main runner.

And step three, determining the boundary conditions of the fluid calculation model of the low-pressure final-stage flow area, wherein a main flow inlet of an inlet of a low-pressure cylinder is provided with a total temperature and total pressure boundary according to an actual boundary, an exhaust steam guide ring outlet of the low-pressure cylinder is provided with a static pressure boundary, a rotating domain is provided with a rotating speed, a mixed surface model is arranged on a dynamic and static interface, and the rest solid wall surfaces are set to be smooth and heat-insulating conditions. The calculation working medium adopts water vapor of an IAPWS-IF97 model.

Step four, solving a Navier-Stokes equation set at Reynolds time through the numerical value of a flow solver, wherein the specific form is as follows:

in the formula: the value ranges of the i index and the j index are 1, 2 and 3, rho is density and the unit is kg.m³，S_MAs source terms of momentum equations, S_EFor the source terms of the energy equation, τ is the tensor of shear stress,in order to take the Reynolds stress term into account,in order to be a turbulent flux, the flow,a work term for stickiness.

And introducing a Boussinesq turbulence model hypothesis, closing a Navier-Stokes equation set when turbulence is calculated and reynolds, wherein the specific form is as follows:

in the formula: mu.s_effIs effectively adhesive.

The discrete format of the solver is a high-precision second-order difference cellular format. When the root mean square residual of the continuous equation, the momentum equation, the energy equation and the turbulence equation reaches 10^-5And in the stage, when the flow imbalance rate of the inlet and the outlet of each calculation domain is less than 0.1%, the calculation is considered to be converged.

And fifthly, obtaining and post-processing a converged multi-working-condition flow calculation analysis result, and further obtaining the meridional plane velocity vector distribution, the meridional plane temperature distribution and the pressure distribution of the low-pressure through-flow area under different steam inflow flow conditions, and the velocity vector distribution, the temperature distribution and the pressure distribution in the cascade channel at the blade height of 10-90%. And calculating the absolute values of physical quantities such as pressure, temperature and speed values at grid nodes in the domain. The calculated conditions include 2.5% THA, 5% THA, 10% THA, 20% THA, 25% THA, 50% THA, and 100% THA conditions. The calculation is carried out by iteration, firstly, the calculation of THA working conditions is carried out to obtain a calculation initial field, and then, the calculation of working conditions such as 50% THA, 30% THA, 20% THA, 10% THA, 5% THA, 2.5% THA and the like is carried out in sequence by iteration.

Analyzing the velocity vector distribution, the temperature distribution and the pressure distribution of the blade grid channels at different inlet steam flow working conditions and different blade height positions, and finding out a grid node with the highest temperature value in the low-pressure through-flow region, wherein the coordinate position of the grid node is the installation position of the blast temperature monitoring sensor.

Example (b):

referring to fig. 1 to 5, the present invention includes the steps of:

the method comprises the steps of firstly, establishing a full-circle multi-stage model of a low-pressure flow area by referring to a real flow structure of a low-pressure cylinder of the steam turbine through three-dimensional modeling software according to a geometric drawing, generating a model fluid calculation domain through fluid analysis software, and respectively arranging static rotating components in the model in static and rotary calculation domains according to actual physical boundaries of the model.

And step two, referring to fig. 2, carrying out mesh planing on the fluid calculation domain by using commercial software to generate a plurality of structured meshes, wherein the calculated meshes need to meet the technical requirements that the maximum length-width ratio is less than 30 and the orthogonal angles are all more than 45 degrees, so as to ensure better orthogonality. When the grids are generated, the grid encryption is carried out on the wall surface so as to meet the requirement of Y + < 1; when the grids are generated, O-shaped attached grids are arranged on the surfaces of the movable and stationary blades of the through-flow stage, and H-shaped grids are arranged at the inlet and outlet extension sections of the main runner. In order to guarantee the solution accuracy, the generated computational grid guarantees one-to-one correspondence of grid nodes in the linked areas, each stage of stationary blades is circumferentially provided with at least 55 nodes, each stage of moving blades is axially provided with at least 73 nodes, each stage of moving blades is circumferentially provided with at least 48 nodes, each stage of moving blades is axially provided with at least 82 nodes, a main flow channel is axially provided with at least 65 nodes along the blade height direction, and the number of final grid computational nodes is 786 ten thousand.

Determining the boundary condition of the fluid calculation model of the low-pressure final-stage flow area, wherein a main flow inlet of a low-pressure cylinder inlet is provided with a total temperature and total pressure boundary according to an actual boundary, and specifically, the total pressure P is given to a THA working condition inlet_INSetting a static pressure boundary, specifically P, at the total temperature of 210 ℃ and the outlet of the low-pressure cylinder exhaust steam guide ring of 0.244MPa_OUTThe rotating speed of the rotating field is set to be 3000rpm, a mixed surface model is arranged on a dynamic and static interface, and the other solid wall surfaces are set to be smooth and heat-insulating conditions. The calculation working medium adopts water vapor of an IAPWS-IF97 model.

Step four, solving a Navier-Stokes equation set at Reynolds time through the numerical value of a flow solver, wherein the specific form is as follows:

in the formula: the value ranges of the i index and the j index are 1, 2 and 3, rho is density and the unit is kg.m³，S_MAs source terms of momentum equations, S_EFor the source terms of the energy equation, τ is the tensor of shear stress,in order to take the Reynolds stress term into account,in order to be a turbulent flux, the flow,a work term for stickiness.

And introducing a Boussinesq turbulence model hypothesis, closing a Navier-Stokes equation set when turbulence is calculated and reynolds, wherein the specific form is as follows:

in the formula: mu.s_effIs effectively adhesive.

The discrete format of the solver is a high-precision second-order difference cellular format. When the root mean square residual of the continuous equation, the momentum equation, the energy equation and the turbulence equation reaches 10^-5And in the stage, when the flow imbalance rate of the inlet and the outlet of each calculation domain is less than 0.1%, the calculation is considered to be converged.

And fifthly, obtaining and post-processing a converged multi-working-condition flow calculation analysis result, and further obtaining the meridional plane velocity vector distribution, the meridional plane temperature distribution and the pressure distribution of the low-pressure through-flow area under different steam inflow flow conditions, and the velocity vector distribution, the temperature distribution and the pressure distribution in the cascade channel at the blade height of 10-90%. And calculating the absolute values of physical quantities such as pressure, temperature and speed values at grid nodes in the domain. The calculated conditions include 2.5% THA, 5% THA, 10% THA, 20% THA, 25% THA, 50% THA, and 100% THA conditions. The calculation is carried out by iteration, firstly, the calculation of THA working conditions is carried out to obtain a calculation initial field, and then, the calculation of working conditions such as 50% THA, 30% THA, 20% THA, 10% THA, 5% THA, 2.5% THA and the like is carried out in sequence by iteration.

Analyzing the velocity vector distribution, the temperature distribution and the pressure distribution of the blade grid channels at different inlet steam flow working conditions and different blade height positions, and finding out a grid node with the highest temperature value in the low-pressure through-flow region, wherein the coordinate position of the grid node is the installation position of the blast temperature monitoring sensor.