CN109214136A - A kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method - Google Patents
A kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method Download PDFInfo
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Abstract
The present invention discloses a kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method, belongs to impeller mechanical simulation technology.It include: the foundation and its grid dividing in three-dimensional basin of axial-flow pump inner flow passage, the building of clearance cavitation flowing mathematical calculation model, the numerical value of permanent cavitating flow calculates inside axial-flow pump, the solution of unsteady cavitating flow inside axial-flow pump, the numerical prediction of axial-flow pump impeller blade tip clearance cavitation zone with check.The present invention considers influence of the local vorticla motion of blade tip clearance to cavitating flows, the flow parameter for reflecting flow field part rotary motion characteristic is added in cavitation model, improve the confidence level of axial-flow pump impeller blade tip clearance cavitation numerical prediction, it is capable of the cavitation zone of Accurate Prediction axial-flow pump impeller blade tip clearance, there is important theoretical value and Practical meaning.
Description
Technical field
The invention belongs to impeller mechanical simulation technology more particularly to a kind of axial-flow pump impeller blade tip clearance cavitation numerical value
Prediction technique.
Background technique
In the impeller channel of axial-flow pump, there are gap, impeller blade tip clearances between rotating vane and leaf top outer rim pump case
It is the concentrated area that axial-flow pump cavitation is destroyed, blade tip clearance cavitation is an important factor for causing axial-flow pump unit failure.By axis
The restriction of impeller of pump blade tip clearance geometric scale and complex flowfield is flowed, the experiment testing cost in clearance cavitation flow field is high, difficulty is big,
Data are limited, and in contrast, the numerical simulation technology based on computational fluid dynamics method is with the obvious advantage.Axial-flow pump impeller leaf top
Gap flow field is rich in eddy motion, although existing scholar probes into the vortex method that disappears of axial-flow pump blade tip clearance, what is run at present
In axial-flow pump used in Large Axial Flow Pump Station and market, blade tip clearance vortex and its vortex cavitation phenomenon caused are still universal.
Since Influencing Mechanism of the eddy motion to vortex cavitation is still not clear, cause the numerical prediction precision of gap vortex cavitation to be improved,
For this reason, it is necessary to develop a kind of numerical computation method for capableing of reasonable prediction axial-flow pump impeller blade tip clearance cavitation.
Summary of the invention
The purpose of the present invention is in axial-flow pump used in current Large Axial Flow Pump Station and market, tip clearance vortex
Stream and its vortex cavitation phenomenon caused, the deficiencies such as vortex cavitation numerical prediction precision is low propose a kind of axial-flow pump impeller blade tip clearance
Cavitation Numerical Predicting Method, it can be considered that influence of the local vorticla motion to cavitating flows, improves axial-flow pump impeller blade tip clearance
The confidence level of cavitation numerical prediction has important theoretical value and Practical meaning.
The technical scheme is that a kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method, which is characterized in that
Include the following steps:
A. the geometrical model of axial-flow pump inner flow passage is established；
B. the grid dividing in axial-flow pump three-dimensional basin；
C. clearance cavitation flowing mathematical calculation model is established；
D. permanent cavitating flow calculates inside axial-flow pump；
E. unsteady cavitating flow calculates inside axial-flow pump；
F. axial-flow pump impeller blade tip clearance cavitation zone determines；
The geometrical model of axial-flow pump inner flow passage described in step A is established, comprising: water inlet flow channel, impeller channel, guide vane stream
The geometrical model of road and outlet passage is established；
Permanent cavitating flow calculates inside axial-flow pump described in step D, comprising: defines the flow boundary of computational domain and initial
Parameter, solution equal equation when can not press Reynolds, using SST-CC turbulence model；Cavitation model is empty using the gap that step C is established
Change flowing mathematical calculation model；
Unsteady cavitating flow calculates inside axial-flow pump described in step E, comprising: by the permanent cavitating flow meter of step D
Result is calculated as primary condition, unsteady computation is defined and solves time step, solves time and convergence, carry out in axial-flow pump
The unsteady cavitating flow in portion calculates；
Axial-flow pump impeller blade tip clearance cavitation zone described in step F determines that method is as follows: obtaining in step E unsteady
In cavitating flow calculated result, vapour phase volume fraction is used to check axial-flow pump impeller blade tip clearance cavitation area for 0.1 contour surface
Domain.
The geometrical model foundation of axial-flow pump inner flow passage described in step A is to be no more than impeller based on blade tip clearance width
2/1000ths of diameter.
The grid dividing of axial-flow pump three-dimensional basin described in step B is using in ANSYS Workbench
TurboGrid module carries out SST hexahedral meshes division to impeller and gate vane channel, and to mesh refinement near leaf top, so as to
Capture the minutia of blade tip clearance cavitating flows.
It is in the condensation item of Zwart cavitation model that clearance cavitation described in step C, which flows mathematical calculation model foundation,
Introduce modifying factor Cc:
In formula: αvFor vapour phase volume fraction, RBFor gas nuclear radius, ρvAnd ρlRespectively vapour phase, density of liquid phase, PvDistinguish with P
Indicate bubble pressure and surrounding fluid pressure, FcFor the coefficient for condensing item；The modifying factor C of introducingcMeet equation:
In formula: r is used to reflect the local rotary motion characteristic in flow field, is defined as:
In formula: S and Ω respectively indicates strain rate tensor and specific rotation tensor；
Thus ANSYS CFX solver is written by CEL sentence in the clearance cavitation mathematical calculation model established.
The invention has the benefit that a kind of axial-flow pump impeller blade tip clearance cavitation numerical prediction side provided by the invention
Method the flow parameter for reflecting flow field part rotary motion characteristic is added in cavitation model, it is contemplated that the whirlpool in vortex cavitation phenomenon
Influence to cavitating flow is flowed, the confidence level of Gap cirele cavitation numerical prediction is improved, obtained and be consistent with experimental result
Impeller leaf top cavitation phenomenon, methodological science, clear principle, the present invention being capable of more scientific prediction axial-flow pump impeller blade tip clearance cavitations
Flow field has important theoretical value and Practical meaning.
Detailed description of the invention
Fig. 1 is axial-flow pump impeller blade tip clearance cavitation numerical prediction flow chart of the invention.
Fig. 2 is middle period of embodiment of the present invention wheel blade top clearance cavitation region and grid schematic diagram.
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples:
A kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method, detailed process is as shown in Figure 1, mainly by following step
It is rapid to realize:
A. the geometrical model of axial-flow pump inner flow passage is established
According to the geometric parameter of certain axial-flow pump, established inside axial-flow pump using 3 d modeling software Unigraphics NX
The geometrical model of runner, including water inlet flow channel, impeller channel, gate vane channel and outlet passage；In impeller channel geometry mould
In type, impeller blade tip clearance width is 1.6/1000ths of runner diameter.
B. the grid dividing in axial-flow pump three-dimensional basin
The geometrical model for the water-in and water-out section runner established in step A is imported into the Mesh mould in ANSYS Workbench
Block, impeller, gate vane channel geometrical model import ANSYS Workbench in TurboGrid module, carry out grid dividing,
And mesh refinement is carried out to wall boundary layer；It checks mesh quality, obtains the grid file met the requirements；In the embodiment of the present invention
50 layers of grid are divided in impeller blade tip clearance width direction, impeller single channel grid node sum is 720,000, grid such as Fig. 2 institute
Show.
C. clearance cavitation flowing mathematical calculation model is established
Modifying factor C is introduced in the condensation item of Zwart cavitation modelc,
In formula: αvFor vapour phase volume fraction, RBFor gas nuclear radius, ρvAnd ρlRespectively vapour phase, density of liquid phase, PvDistinguish with P
Indicate bubble pressure and surrounding fluid pressure, FcFor the coefficient for condensing item；The modifying factor C of introducingcMeet equation:
In formula: r is used to reflect the local rotary motion characteristic in flow field, is defined as:
In formula: S and Ω respectively indicates strain rate tensor and specific rotation tensor；
ANSYS CFX solver is written into formula (1), (2) and (3) by CEL sentence, thus establishes clearance cavitation numerical value meter
Calculate model.
D. permanent cavitating flow calculates inside axial-flow pump
The grid file in the axial-flow pump three-dimensional basin established step B is imported into computational fluid dynamics solver ANSYS
CFX, sets wheel speed, the import section of given inlet segment runner be stagnation pressure boundary, water exit end runner outlet be stream
Interface type between amount boundary, rotary blade runner and stagnant zone is Frozen Rotor, remaining wall surface is fixation wall
Noodles part；Equal equation when can not press Reynolds is solved, using SST-CC turbulence model, i.e., selectes Shear in ANSYS CFX
On the basis of Stress Transport (SST) turbulence model, Curvature Correction option is chosen, enables SST-CC
Turbulence model；On the basis of selecting Zwart cavitation model in ANSYS CFX, the clearance cavitation that invocation step C is established flows
Mathematical calculation model corrects the condensation item of Zwart cavitation model；Numerical value, which calculates, obtains permanent cavitating flow inside axial-flow pump.
E. unsteady cavitating flow calculates inside axial-flow pump
Using the permanent cavitating flow calculated result of step D as primary condition, definition solves time step as impeller rotation
The 1/360 of period, convergence are that RMS reaches 10-4, carry out the unsteady cavitating flow numerical value of axial-flow pump and calculate, reach convergence mark
The flow field of 6 impeller swing circles is averaged after standard.
F. axial-flow pump impeller blade tip clearance cavitation zone determines
The calculated result of step E is imported into ANSYS CFX-Post module, use vapour phase volume fraction for 0.1 contour surface
Check axial-flow pump impeller blade tip clearance cavitation zone, as shown in Fig. 2, in figure by the region of grid dividing be leaf area, leaf top
The region for not drawing grid lines nearby is cavitation range.
A kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method proposed by the present invention, is applied to engineering practice and works as
In, do not increase the resource consumption of numerical value calculating, obtain the impeller leaf top cavitation phenomenon being consistent with experimental result, realizes pair
The reasonable prediction of blade tip clearance cavitation zone.
Claims (4)
1. a kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method, which comprises the steps of:
A. the geometrical model of axial-flow pump inner flow passage is established；
B. the grid dividing in axial-flow pump three-dimensional basin；
C. clearance cavitation flowing mathematical calculation model is established；
D. permanent cavitating flow calculates inside axial-flow pump；
E. unsteady cavitating flow calculates inside axial-flow pump；
F. axial-flow pump impeller blade tip clearance cavitation zone determines；
The geometrical model of axial-flow pump inner flow passage described in step A is established, comprising: water inlet flow channel, impeller channel, gate vane channel and
The geometrical model of outlet passage is established；
Permanent cavitating flow calculates inside axial-flow pump described in step D, comprising: defines the flow boundary of computational domain and initially joins
Number, solution equal equation when can not press Reynolds, using SST-CC turbulence model；The clearance cavitation that cavitation model uses step C to establish
Flow mathematical calculation model；
Unsteady cavitating flow calculates inside axial-flow pump described in step E, comprising: the permanent cavitating flow of step D is calculated knot
Fruit defines unsteady computation and solves time step, solves time and convergence, carry out non-inside axial-flow pump as primary condition
Permanent cavitating flow calculates；
Axial-flow pump impeller blade tip clearance cavitation zone described in step F determines that method is as follows: in the unsteady cavitation that step E is obtained
In Flow Field Calculation result, vapour phase volume fraction is used to check axial-flow pump impeller blade tip clearance cavitation zone for 0.1 contour surface.
2. a kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method according to claim 1, it is characterised in that: step
It is thousand points for being no more than impeller diameter based on blade tip clearance width that the geometrical model of axial-flow pump inner flow passage described in rapid A, which is established,
Two.
3. a kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method according to claim 1, it is characterised in that: step
The grid dividing in axial-flow pump three-dimensional basin described in rapid B is using the TurboGrid module in ANSYS Workbench to leaf
Wheel and gate vane channel carry out SST hexahedral meshes division, and to mesh refinement near leaf top, to capture blade tip clearance cavitation
The minutia of flowing.
4. a kind of axial-flow pump impeller blade tip clearance cavitation Numerical Predicting Method according to claim 1, it is characterised in that: step
Clearance cavitation flowing mathematical calculation model foundation described in rapid C is to introduce modifying factor in the condensation item of Zwart cavitation model
Sub- Cc:
As P >=Pv (1)
In formula: αvFor vapour phase volume fraction, RBFor gas nuclear radius, ρvAnd ρlRespectively vapour phase, density of liquid phase, PvIt is respectively indicated with P
Bubble pressure and surrounding fluid pressure, FcFor the coefficient for condensing item；The modifying factor C of introducingcMeet equation:
In formula: r is used to reflect the local rotary motion characteristic in flow field, is defined as:
In formula: S and Ω respectively indicates strain rate tensor and specific rotation tensor；
Thus ANSYS CFX solver is written by CEL sentence in the clearance cavitation mathematical calculation model established.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109977345A (en) * | 2019-01-29 | 2019-07-05 | 河海大学 | A kind of method for numerical simulation of axial-flow pump clearance leakage of blade tip vortex cavitation |
| CN110096812A (en) * | 2019-05-05 | 2019-08-06 | 湖南凯利特泵业有限公司 | A kind of cavitation performance of centrifugal pump automatic simulation method based on CFD platform |
| CN117172159A (en) * | 2023-11-01 | 2023-12-05 | 北京大学 | Method, apparatus, computer device and storage medium for determining cavitation area |
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| CN103309727A (en) * | 2013-06-19 | 2013-09-18 | 江苏大学 | Vane pump cavitation numerical simulation automatic operation method based on ANSYS-CFX software |
| CN107194145A (en) * | 2017-04-11 | 2017-09-22 | 江苏大学 | A kind of centrifugal pump cavitation corrosion Numerical Predicting Method |
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2018
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103309727A (en) * | 2013-06-19 | 2013-09-18 | 江苏大学 | Vane pump cavitation numerical simulation automatic operation method based on ANSYS-CFX software |
| CN107194145A (en) * | 2017-04-11 | 2017-09-22 | 江苏大学 | A kind of centrifugal pump cavitation corrosion Numerical Predicting Method |
Non-Patent Citations (1)
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| 郭嫱: "叶顶间隙泄漏涡流及空化流场特性研究", 《中国博士学位论文全文数据库（电子期刊）》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109977345A (en) * | 2019-01-29 | 2019-07-05 | 河海大学 | A kind of method for numerical simulation of axial-flow pump clearance leakage of blade tip vortex cavitation |
| CN110096812A (en) * | 2019-05-05 | 2019-08-06 | 湖南凯利特泵业有限公司 | A kind of cavitation performance of centrifugal pump automatic simulation method based on CFD platform |
| CN117172159A (en) * | 2023-11-01 | 2023-12-05 | 北京大学 | Method, apparatus, computer device and storage medium for determining cavitation area |
| CN117172159B (en) * | 2023-11-01 | 2024-02-02 | 北京大学 | Method, apparatus, computer device and storage medium for determining cavitation area |
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Application publication date: 20190115 |