CN106326531B - Industrial steam turbine exhaust system optimization method - Google Patents
Industrial steam turbine exhaust system optimization method Download PDFInfo
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- CN106326531B CN106326531B CN201610654117.0A CN201610654117A CN106326531B CN 106326531 B CN106326531 B CN 106326531B CN 201610654117 A CN201610654117 A CN 201610654117A CN 106326531 B CN106326531 B CN 106326531B
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Abstract
The invention discloses an optimization method of an industrial steam turbine exhaust system. The method is based on a SiPESC-OPT integrated software platform, and integrates multiple software such as modeling, grid division, numerical calculation, result extraction and optimization algorithm to construct a turbine low-pressure exhaust cylinder optimization design system. The optimization method realizes the parametric modeling of the exhaust cylinder; obtaining a more real steam flow parameter of the inlet of the exhaust cylinder by calculating the pneumatic performance of the low-pressure stage group; solving an N-S partial differential equation by adopting a proper turbulence model, and performing three-dimensional numerical simulation on the exhaust cylinder to obtain detailed flow conditions and pneumatic performance inside the exhaust cylinder; and realizing optimization iteration of the exhaust cylinder diffuser through an optimization algorithm until global convergence. The exhaust cylinder optimally designed by the invention can improve the pneumatic performance of the exhaust cylinder so as to improve the overall efficiency of the industrial steam turbine.
Description
Technical Field
The invention relates to an industrial steam turbine, in particular to an exhaust optimization method for a steam turbine exhaust casing.
Background
The improvement in turbine economy can be improved from two aspects. Firstly, the thermodynamic process of a steam turbine is improved by improving the parameters of new steam, such as pressure and temperature, and the working capacity of a single unit is increased, such as a supercritical and ultra-supercritical steam turbine; the second approach is to optimize the turbine structure, such as the admission valve, the blades at each stage, and the exhaust cylinder, to improve the turbine's through-flow capacity and thermal efficiency, thereby improving the efficiency of the whole unit.
In the condensing steam turbine, a low-pressure exhaust cylinder mainly comprises a diffuser and a volute, and the exhaust cylinder is connected with a last-stage movable blade of the steam turbine and a condenser. The exhaust cylinder is used for converting residual speed kinetic energy at the outlet of the last stage blade of the steam turbine into pressure energy and guiding wet steam from the last stage blade to the condenser. The final-stage residual speed kinetic energy of the steam turbine is 45 KJ/kg-60 KJ/kg, the steam exhaust loss is large, the energy loss of an exhaust cylinder is reduced by 0.1, and the overall efficiency of the steam turbine can be improved by about 0.15%. The loss coefficient of the low-pressure exhaust cylinder is reduced, so that the efficiency of the unit can be effectively improved, and considerable economic benefit is brought.
The internal flow of the exhaust cylinder is complex, three-dimensional, viscous and unsteady, and is influenced by the velocity distribution of the upstream blade outlet, so that the performance of the exhaust cylinder is difficult to accurately predict. In general, the optimum design of the exhaust cylinders, which treats the diffuser as a two-dimensional flow, does not take into account tangential flow. How to accurately predict the pneumatic performance of the exhaust cylinder is a subject with practical significance by controlling the structure of the diffuser and three-dimensionally optimizing the pneumatic performance of the exhaust cylinder.
Disclosure of Invention
The invention aims to: compared with the prior art, the method for optimizing the aerodynamic performance of the exhaust system of the industrial steam turbine is more accurate and has higher optimization speed.
A method for optimizing an exhaust system of an industrial steam turbine is characterized by comprising the following steps:
and 3, carrying out grid division on the steam exhaust cylinder with the parameterized structure by using grid division software, and encrypting the boundary layer to ensure that the grid quality meets the requirement of the Y + value of the selected turbulence model. Recording the grid division process, recording the grid division process as a macro, and calling the macro in the later optimization process to realize automatic grid division;
step 4, adding the pneumatic parameters of the outlet of the low-pressure blade group obtained in the step 2 into the inlet of the exhaust cylinder as the inlet condition of the exhaust cylinder, giving back pressure to the outlet of the exhaust cylinder, and analyzing the pneumatic performance of the exhaust cylinder by using three-dimensional fluid numerical calculation software; selecting a proper turbulence model to calculate the aerodynamic characteristics of the exhaust cylinder, wherein the calculated residual error is less than 10E-5 and is stable, and the flow field is considered to be convergent;
step 5, extracting numerical calculation results (total temperature, total pressure and speed of an inlet and an outlet of the exhaust cylinder) of the exhaust cylinder, and calculating to obtain a static pressure recovery coefficient and a total pressure loss coefficient of the exhaust cylinder;
and 6, integrating the steps 1 to 5 on a software optimization platform SiPESC. Namely: and (3) taking the angle and the length of the diffuser of the exhaust cylinder as control variables, and changing the size of the control variables to obtain different objective function values.
The invention provides an optimization method of an industrial steam turbine exhaust system, which is more accurate and has higher optimization speed compared with the prior art, based on the optimization theory of three-dimensional CFD calculation. In order to achieve the purpose, the method for solving the N-S equation is adopted to calculate the pneumatic performance of the exhaust cylinder; the structure of the diffuser of the exhaust cylinder is automatically modified through an optimization algorithm, the pneumatic performance of the exhaust cylinder is improved, the aim is to control the flow of steam in the exhaust cylinder, reduce flow separation and convert the residual speed kinetic energy of the steam flow into more pressure energy.
Drawings
FIG. 1 is a graph of the location of design variables in a geometric model according to the present invention;
FIG. 2 is a comparison of the geometry before and after optimization according to the present invention;
FIG. 3 is a three-dimensional flow chart of the interior of the present invention before optimization;
fig. 4 is a three-dimensional flow chart of the optimized interior of the present invention.
Detailed Description
The invention will be described in detail below with reference to the following drawings:
taking an example of the low-pressure exhaust cylinder of the industrial steam turbine with the exhaust mass flow of 70t/h and the condensation pressure of 0.09bar as an optimization, the exhaust cylinder comprises a diffuser and a volute, and the partial structure of the diffuser is shown in fig. 1 and fig. 2, so as to further describe the specific implementation mode of the invention.
The optimization design is carried out according to the following steps
Then, according to the process and strength and rigidity requirements of the exhaust cylinder, the upper limit and the lower limit of the four variables are determined, and the structure of the rest cylinder body part is unchanged. The parameters can facilitate the later-stage calling of the macro file to modify the structure of the exhaust cylinder diffuser, and the value range of the design variable of the exhaust cylinder
| D8(rad) | D9(m) | D10(rad) | D11(m) | |
| Initial value | 0.453786 | 0.0657551 | 0.695285 | 0.397202 |
| Upper limit of | 0.3490658 | 0.06 | 0.610865 | 0.25 |
| Lower limit of | 0.78539815 | 0.12 | 1.0471975 | 0.4 |
The initial value is the original design value.
And 2, modeling a low-pressure stage group in front of the exhaust cylinder, and performing single-channel grid division by adopting Turbogrid software to ensure that Y + is between 11.7 and 100. The boundary conditions of numerical calculation are design parameters, total temperature, total pressure and steam dryness are given at an inlet, static pressure is given at an outlet, and a high Reynolds number turbulence model is adopted: calculating a standard k-epsilon two-equation model, adding boundary conditions and loads by using CFX-Pre, selecting a Steam3Vl wet Steam model in IAPWS-97 as a calculation working medium, wherein the pressure range of the model is as follows: 0.1KPa to 200KPa, and the temperature range is as follows: 273K to 550K; scalable wall function selection for near wall flowMethod, residual convergence to 1 × 10-5(ii) a And calculating the distribution of pressure, temperature, airflow angle and other pneumatic parameters at the outlet of the low-pressure stage group.
And 3, carrying out grid division on the steam exhaust cylinder with the parameterized structure by using grid division software ICEM, and encrypting the boundary layer by using a triangular prism grid so that the grid quality meets the requirement of the Y + value of the selected turbulence model. Recording the grid division process into macros, calling the macros in the later optimization process, realizing automatic grid division, and ensuring that the grid distribution of the exhaust cylinders is consistent in each optimization calculation.
And 4, endowing the steam flow parameters of the outlet of the low-pressure stage group obtained by calculation in the step two to the inlet of the exhaust cylinder, and giving pressure boundary conditions to the outlet of the exhaust cylinder. Calculating the working medium as water vapor, and adopting a high Reynolds number turbulence model: calculating a standard k-epsilon two-equation model, adding boundary conditions and loads by using CFX-Pre, selecting a Steam3Vl wet Steam model in IAPWS-97 as a calculation working medium, wherein the pressure range of the model is as follows: 0.1KPa to 200KPa, and the temperature range is as follows: 273K to 550K; and calculating that the residual error is less than 10E-5 and stable, and then considering the convergence of the flow field. And saving the setting of the calculation process to ensure the consistency of the calculation setting of each optimization calculation. By this step, all the pneumatic parameters of the exhaust cylinder, such as the exhaust cylinder inlet pressure, outlet velocity profile, inlet temperature, outlet temperature, etc., are obtained.
And 5, extracting a calculation result, namely extracting the total temperature, the total pressure and the speed of the inlet and the outlet of the exhaust cylinder from the calculation result of the previous step. And calculating the static pressure recovery coefficient and the total pressure loss coefficient of the exhaust cylinder. For each sub-optimization calculation, CFD-Post executes the pre-recording operation stored in cse file, reads the calculation result, calculates the data such as pressure recovery coefficient, and writes the data into the file.
And 6, integrating the steps 1 to 5 on a software optimization platform SiPESC. And the circulation realizes the automation of the whole optimal design system. The optimization algorithm adopts an ant colony algorithm, and the principle of the ant colony algorithm is the process of searching food by ants. Starting from an initial point, each ant randomly selects a route to search for food; if the food is found, returning to the ant nest, and leaving pheromone along the way in the process of returning to the ant nest; the pheromone can attract other ants to search for hormone-containing routes randomly; on the path with short circuit, the time taken by ants to search for food is short, the probability of walking through the ants is increased, when more ants walk the same route, the concentration of pheromone in the route is enhanced, and other routes are reduced until the ants disappear. And finally, the ant colony finds the shortest route, namely the optimal solution. And the optimization algorithm ant colony algorithm is applied to optimize the static pressure recovery coefficient and the total pressure loss coefficient of the exhaust cylinder,
referring to fig. 2 and 2, the state of the diffuser pipe before optimization is indicated, and 1 indicates the state of the diffuser pipe after the parameters D10 and D11 are optimized. The static pressure recovery coefficient is improved to 0.15 from 0.06 after the optimization is verified, and the whole static pressure recovery coefficient is improved by 150%.
Fig. 3 is a three-dimensional flow chart of the interior of the present invention before optimization, and fig. 4 is a three-dimensional flow chart of the interior of the present invention after optimization. As can be seen from the figure, because the diffuser guide vane holding ring is optimized, the diffuser pipe of the guide vane holding ring is more reasonable in design, and the diffusion of the steam flow in the diffuser is more sufficient. The flow loss of the exhaust volute is small, and a steam flow acceleration area in a large range does not appear, so the static pressure recovery capability of the exhaust cylinder is better than that of the prior scheme.
Claims (5)
1. A method for optimizing an exhaust system of an industrial steam turbine is characterized by comprising the following steps:
step 1, setting the internal flow of the impeller machine to obey an N-S equation, considering the actual influence of viscosity and gap leakage, and carrying out three-dimensional structural feature parameterization on the diffuser part of the exhaust cylinder; so as to later call the macro file to modify the structure of the exhaust steam cylinder diffuser;
step 2, modeling a low-pressure stage group in front of the exhaust cylinder, and performing single-channel grid division and pneumatic calculation; the boundary condition is a design parameter, total temperature, total pressure and dryness of the steam are given at an inlet, static pressure is given at an outlet, and the steam is calculated as the working medium; analyzing the pneumatic performance of the low-pressure blade by using three-dimensional fluid numerical calculation software, and calculating to obtain the distribution of pressure, temperature and airflow angle at the outlet of the low-pressure blade group;
step 3, gridding division is carried out on the steam exhaust cylinder with the parameterized structure by using gridding division software, and a boundary layer is encrypted, so that the grid quality meets the requirement of a Y + value of a selected turbulence model; recording the grid division process, recording the grid division process as a macro, and calling the macro in the later optimization process to realize automatic grid division;
step 4, adding the pneumatic parameters of the outlet of the low-pressure blade group obtained in the step 2 into the inlet of the exhaust cylinder as the inlet condition of the exhaust cylinder, giving back pressure to the outlet of the exhaust cylinder, analyzing the pneumatic performance of the exhaust cylinder by applying three-dimensional fluid numerical calculation software, selecting a proper turbulence model to calculate the pneumatic characteristic of the exhaust cylinder, and considering that the flow field is convergent if the calculation residual is less than 10E-5 and is stable; saving the setting of the calculation process to ensure the consistency of the calculation setting of each optimization calculation;
step 5, extracting the numerical calculation result of the exhaust cylinder, and calculating the total temperature, total pressure and speed of the inlet and the outlet of the exhaust cylinder to obtain the static pressure recovery coefficient and the total pressure loss coefficient of the exhaust cylinder;
and 6, integrating the steps 1 to 5 on a software optimization platform SiPESC.
2. The optimization method according to claim 1, wherein the three-dimensional fluid numerical calculation software employs CFX or Fluent; the grid division software adopts Turbogid or ICEM or Gambit.
3. The optimization method according to claim 1, wherein the optimization algorithm in step 6 is an ant colony algorithm or a genetic algorithm.
4. The optimization method according to claim 1, wherein the parameterization of the three-dimensional structural characteristics of the exhaust-cylinder diffuser part in step 1 is a parameterization modeling of a guide vane carrier ring part of the diffuser structure, the guide vane carrier ring is divided into two segments, and four parameterization variables are defined, wherein the four parameterization variables are respectively D8 for the first segment starting angle of the diffuser, D9 for the first segment length of the diffuser, D10 for the second segment starting angle of the diffuser, and D11 for the second segment length of the diffuser.
5. The optimization method according to claim 4, wherein the four variables D8, D9, D10, D11 are determined as follows according to the process and strength stiffness requirements of the exhaust cylinder:
the range of D8 is: 0.3490658 rad-0.78539815 rad, D9 is: 0.06 m-0.12 m, and the range of D10 is as follows: 0.610865 rad-1.0471975 rad, D11 is: 0.25m to 0.4 m.
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| CN109614737A (en) * | 2018-12-24 | 2019-04-12 | 中国船舶重工集团公司第七0三研究所 | A kind of helium turbine loop parameter optimization method based on genetic algorithm |
| CN109948233A (en) * | 2019-03-14 | 2019-06-28 | 哈尔滨汽轮机厂有限责任公司 | The wide load blade design optimization system of small enthalpy drop and method based on CFD |
| CN110990939B (en) * | 2019-10-10 | 2024-04-19 | 西北工业大学 | Method for designing reliability of anti-icing cavity structure |
| CN111859733B (en) * | 2020-06-19 | 2023-06-27 | 江西五十铃汽车有限公司 | Method for optimizing reliability of automobile exhaust system based on ant colony algorithm |
| CN111927581B (en) * | 2020-09-08 | 2022-07-12 | 杭州汽轮机股份有限公司 | Multi-surface supported welding exhaust cylinder of industrial steam turbine |
| CN111927582B (en) * | 2020-09-10 | 2022-07-12 | 杭州汽轮机股份有限公司 | Exhaust casing of industrial steam turbine |
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| CN102749156B (en) * | 2012-07-13 | 2014-07-09 | 东南大学 | Method for detecting exhaust enthalpy of turbine |
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Address after: 310022 Building 1, No. 608, Kangxin Road, Linping District, Hangzhou, Zhejiang Patentee after: Hangzhou Turbine Power Group Co.,Ltd. Address before: 357 Shiqiao Road, Xiacheng District, Hangzhou City, Zhejiang Province Patentee before: HANGZHOU STEAM TURBINE Co.,Ltd. |
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Application publication date: 20170111 Assignee: Hangzhou Steam Turbine Machinery Equipment Co.,Ltd. Assignor: Hangzhou Turbine Power Group Co.,Ltd. Contract record no.: X2022330000771 Denomination of invention: An optimization method for exhaust system of industrial steam turbine Granted publication date: 20210323 License type: Common License Record date: 20221226 |
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