CN108052775A - A kind of turbine draft tube vortex rope analysis method based on jet stream - Google Patents
A kind of turbine draft tube vortex rope analysis method based on jet stream Download PDFInfo
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Abstract
The present invention proposes a kind of turbine draft tube vortex rope analysis method based on jet stream, comprises the following steps：Step 1, selected 15mm apertures down-off are 0.73QBEP, rotating speed be 900r/min operating point, QBEP=0.215m3/s；Step 2, selected turbulence model and multiphase flow model, determine boundary condition；Step 3 carries out single-phase jet stream unsteady computation according to operating point information, turbulence model, multiphase flow model and definite boundary condition, so as to obtain the amount of jet information of the operating point；Step 4 analyzes the shape of draft tube vortex rope according to amount of jet information；Step 5 analyzes the distribution situation of X-direction axial velocity radially on the streamline of draft tube meridional plane and draft tube right cone section cross section according to amount of jet information；The Entropy generation distribution situation of step 6, the performance to be recovered energy according to amount of jet information to draft tube and draft tube meridional plane is analyzed.
Description
Technical field
The invention belongs to pump turbine draft tube vortex rope technical field, more particularly to a kind of hydraulic turbine based on jet stream
Draft tube vortex rope analysis method.
Background technology
Due to the complexity of draft tube internal flow, although have a large amount of scholars carries out correlative study to its flow process,
But theoretical side never has the progress of making a breakthrough property, and the conclusion of uniformity is not drawn on vortex rope formation mechenism yet.It closes
In experimental study, real machine test it is inconvenient, spend it is larger etc. due to and it is commonly used less, be mainly nonetheless focused upon mould
Type is tested.In test a series of sophisticated equipments such as high-speed motion picture camera, Doppler anemometer and PIV technologies and method are all put into
It uses, but since the generation of draft tube vortex rope with liquid-gas phase transition and is the process of a transient state, on its formation mechenism
The experimental study achievement of aspect is also very limited.The main side still generated around control vortex rope of current experimental study both domestic and external
In method, such as tonifying Qi, jet stream, change draft tube and sluicing cone-shaped, laying gusset and stabilier, and separately verified above-mentioned side
The feasibility and quality of method.With developing by leaps and bounds for computer technology, numerical value emulation method is slowly more favored.On
The research of draft tube vortex rope, the current work of numerical simulation both at home and abroad are mostly carried out around the following aspects：Difference calculates basin
Selection (part basin and full runner)；The selection of different turbulent models；The calculating of single-phase flow and multiphase flow, including single-phase numerical value
Simulation, two-phase tonifying Qi and the calculating of two-phase cavitation etc..By numerical simulation, the weight that many theoretical and experiment can not all obtain is obtained
Information is wanted, help is provided for further improving theoretical and guidance experiment.
It makes a general survey of both at home and abroad to the research in terms of draft tube vortex rope, still still has several drawbacks：(1) draft tube vortex rope is produced
Raw mechanism understanding is thorough not enough, it is most of Francis turbine all is built upon to the research of vortex rope on the basis of, rarely have
It is studied for the vortex rope under pump turbine variable working condition；(2) due to the limitation of computing resource, the country is to draft tube vortex rope
Numerical simulation also rests on single-phase or only considers that the cavitation under the basin of part calculates mostly, for pump turbine in different dresses
The full runner vortex rope cavitation calculating put under cavitation number is also less；(3) although the experimental study on tonifying Qi is had it long ago, but
The numerical simulation pertinent literature of this respect is also seldom, need on air compensation to the control effect of pump turbine vortex rope into
One step is analyzed, and in addition jet stream also has the value further studied to the effect for improving vortex rope.
The content of the invention
The present invention proposes a kind of turbine draft tube vortex rope analysis side based on jet stream to solve the technical issues of existing
Method.
The purpose of the present invention is achieved through the following technical solutions：A kind of turbine draft tube vortex rope analysis side based on jet stream
Method comprises the following steps：
Step 1, selected 15mm apertures down-off are 0.73QBEP, rotating speed be 900r/min operating point, QBEP=
0.215m3/s；
Step 2, selected turbulence model and multiphase flow model, determine boundary condition；
Step 3 carries out single-phase penetrate according to operating point information, turbulence model, multiphase flow model and definite boundary condition
Unsteady computation is flowed, so as to obtain the amount of jet information of the operating point；
Step 4 analyzes the shape of draft tube vortex rope according to amount of jet information；
Step 5, according to amount of jet information to X-direction on the streamline of draft tube meridional plane and draft tube right cone section cross section
The distribution situation of axial velocity radially is analyzed；
The Entropy generation of step 6, the performance to be recovered energy according to amount of jet information to draft tube and draft tube meridional plane
Distribution situation is analyzed.
Further, the turbulence model be RNG k- ε models, multiphase flow model be mixture models, the perimeter strip
Part is volute inlet liquid flow, draft tube outlet pressure and short tube inlet gas mass flow.
Further, the amount of jet is expressed as volume flow percentage, and the step 3 obtains 4 groups of amount of jet information altogether,
I.e. amount of jet is respectively 2%, 4%, 6% and 8% amount of jet information.
Description of the drawings
Fig. 1 is original vortex rope shape graph；
Vortex rope shape graph under Fig. 2 different jet amounts；
Draft tube meridional flow line chart under Fig. 3 different jet amounts；
Draft tube cross section axis is to the radially distributed figure of speed under Fig. 4 different jet amounts；
Turbine efficiency variation diagram under Fig. 5 different jet amounts；
Draft tube energy loss distribution map under Fig. 6 different jet amounts；
Draft tube meridional plane Entropy generation distribution map under Fig. 7 different jet amounts.
Specific embodiment
The technical solution in the embodiment of the present invention is carried out below in conjunction with the attached drawing in the embodiment of the present invention clear, complete
Ground describes, it is clear that described embodiment is only part of the embodiment of the present invention, instead of all the embodiments.Based on this
Embodiment in invention, the every other reality that those of ordinary skill in the art are obtained without making creative work
Example is applied, belongs to the scope of protection of the invention.
The present invention proposes a kind of turbine draft tube vortex rope analysis method based on jet stream, comprises the following steps：
Step 1, selected 15mm apertures down-off are 0.73QBEP, rotating speed be 900r/min operating point, QBEP=
0.215m3/s；
Step 2, selected turbulence model and multiphase flow model, determine boundary condition；
Step 3 carries out single-phase penetrate according to operating point information, turbulence model, multiphase flow model and definite boundary condition
Unsteady computation is flowed, so as to obtain the amount of jet information of the operating point；
Step 4 analyzes the shape of draft tube vortex rope according to amount of jet information；
Step 5, according to amount of jet information to X-direction on the streamline of draft tube meridional plane and draft tube right cone section cross section
The distribution situation of axial velocity radially is analyzed；
The Entropy generation of step 6, the performance to be recovered energy according to amount of jet information to draft tube and draft tube meridional plane
Distribution situation is analyzed.
The turbulence model is RNG k- ε models, and multiphase flow model is mixture models, and the boundary condition is spiral case
Entrance liquid flow, draft tube outlet pressure and short tube inlet gas mass flow.
The amount of jet is expressed as volume flow percentage, and the step 3 obtains 4 groups of amount of jet information, i.e. amount of jet altogether
The amount of jet information of respectively 2%, 4%, 6% and 8%.
Numerical simulation principle
The generation of vortex rope in draft tube is because foring pressure value in draft tube less than current saturation under corresponding temperature
The low-pressure area of vapour pressure by subregional pressure rise in the middle part of tonifying Qi current, while introduces certain damping and breaks
Vacuum area in bad tail water vortex rope reduces the quantity of cavitation bubble, so as to achieve the purpose that weaken vortex rope.
For the present invention when unsteady numerical simulations are carried out, it is 0.73Q to select 15mm apertures down-offBEP, rotating speed be
The operating point of 900r/min calculated by the single-phase jet stream of the short tube of medium of water, and turbulence model is RNG k- ε models, by giving
It is boundary condition to determine volute inlet liquid flow, draft tube outlet pressure, short tube inlet gas mass flow, and multiphase flow model selects
Mixture models are selected, surface tension coefficient is set to 0.072N/m, and the influence of cavitation is not considered in calculating process.It penetrates
The volume flow of stream calculates 2%, 4%, 6%, 8% totally 4 groups, and the amount of jet details for calculating operating point are as shown in table 1.
1 jet quality flow (kg/s) of table
Jet stream effect analysis
Fig. 1 is the vortex rope shape for not taking corrective measure, and Fig. 2 is the shape graph of draft tube vortex rope under different jet amount, from
As can be seen that when amount of jet is 2% in Fig. 2, vortex rope shape is almost without changing；When amount of jet is 4%, in vortex rope
Portion starts block cavitation zone occurred, and vortex rope afterbody is tapered；When amount of jet is 6%, vortex rope becomes very thick, distortion
Degree decreases；When amount of jet be 8% when, vortex rope becomes cylindric, and torsion resistance almost disappears, at this time with vortex rope under big flow
Shape it is much like.
Draft tube meridional plane streamline under the conditions of jet stream as shown in figure 3, from figure 3, it can be seen that when amount of jet for 2%,
When 4%, the spiral structure of draft tube right cone section is similar, and vortex is larger and is interspersed.When amount of jet is 6%, can substantially see
To the track of right cone section top jet stream, spiral structure also becomes smaller.When amount of jet be 8% when, jet path become apparent from and speed more
Greatly, right cone section vortex almost disappears, and tail water Bottomhole pressure becomes simple.Above-mentioned phenomenon explanation, when amount of jet reaches certain value,
The powerful percussion of jet stream can effectively smash the spiral structure in draft tube, improve the flowing in draft tube.But due to penetrating
Stream also accelerates the speed of right cone section centre liquid stream simultaneously so that and pressure reduces, therefore therefore vortex rope can't disappear, and
It is to become cylindric from helical form.
Fig. 4 is the distribution situation of x directions axial velocity radially on draft tube right cone section cross section under different jet amount, from
As can be seen that the fluid axial velocity of draft tube near wall is influenced by amount of jet variation less, when close at wall surface in Fig. 4
Fluid axial velocity is acted on by wall friction and there are a decelerations.When amount of jet is 2% and 4%, in draft tube central part
The fluid axial velocity of position increases with amount of jet and slightly reduces, when amount of jet increases to 6% and 8%, in tail water tube hub
The axial velocity of position fluid from becoming downward upwards, and absolute value sharply increases, and which results in pressure reduction, therefore also may be used
Illustrate why the volume that amount of jet increase can not effectively reduce vortex rope.
Draft tube is in addition to there is the liquid stream by outlet of rotary wheel smoothly to guide downstream effects into, moreover it is possible to by outlet of rotary wheel liquid stream
Kinetic energy and it is transformed into addition of vacuum higher than downstream tail water geopotential energy, recycles excess energy, and then improves turbine efficiency.
Usually use energy recovery factor ηwTo characterize the performance that draft tube recovers energy：
In formula：v1--- draft tube inlet average speed (m/s)；v2--- draft tube average exit speed (m/s)；
Δh1-2--- draft tube energy loss (m)；G --- acceleration of gravity (m/s2)。
The energy loss of draft tube and energy recovery factor are as shown in table 1 under different jet amount, and turbine efficiency is with amount of jet
Change curve is as shown in Figure 5.As can be seen from Table 2, with the increase of amount of jet, the energy loss of draft tube also becomes larger.When
When amount of jet is 2%~6%, the energy recovery factor of draft tube is raised with the increase of amount of jet, but when amount of jet rises to 8%
When, the unexpected rapid drawdown of energy recovery factor, thus it is speculated that this is because the loss of draft tube self-energy excessively causes.
Decline from figure 5 it can be seen that the efficiency of the hydraulic turbine is almost linear with the increase of amount of jet, this is because with
Runner acting is not flowed through in the current of jet stream, and energy possessed by the part current will be counted to hydraulic turbine institute aqueous stream
In gross energy, this will result in the waste of a part of flow energy, cause the decline of turbine efficiency.Any improvement is not taken to arrange
The efficiency of the hydraulic turbine is 88.7% when applying, and turbine efficiency is 87.6% when amount of jet is 2%, has dropped 1 percentage point；When
When amount of jet is 8%, turbine efficiency 83.6% has dropped 5 percentage points, declines by a big margin.Therefore, jet stream is being passed through
When mode improves draft tube vortex rope, it is impossible to only pursue the improvement of vortex rope, and a suitable amount of jet to be selected to make water
The efficiency of turbine is unlikely to decline excessive.
Draft tube energy recovery factor under 2 different jet amount of table
Fig. 6 is the energy loss distribution situation of draft tube right cone section, curved elbow section and diffuser under different jet amount, from Fig. 6
In as can be seen that the energy loss of draft tube focuses primarily upon right cone section, with the increase right cone section of amount of jet under the conditions of jet stream
Energy loss becomes larger, and when amount of jet be 6% and 8% when right cone section energy loss occur being significantly increased.Curved elbow section energy
Amount loss increases with amount of jet and is gradually reduced, but amplitude of variation very little, and diffuser energy loss increases almost with amount of jet
It has no change.Above-mentioned phenomenon explanation, influence of the jet stream to right cone section is maximum, and to the influence very little of curved elbow section and diffuser.
The flow process mechanical energy that invariably accompanies is converted into the irreversible loss of interior energy in the hydraulic turbine, and the loss is from thermodynamics
Angle can be described with entropy production, this makes it possible to the distribution situations for knowing clearly energy loss.
Two parts of turbulent dissipation caused by with instantaneous velocity pulsation are moved when the Entropy generation of fluid particle includes, this
Two parts are known as turbulent dissipation item, can be calculated by following formula：
In formula, T is thermodynamic temperature, μeffFor virtual viscosity, turbulence viscosity μ can be passed throughtCarry out table with dynamic viscosity μ
Show：
μeff=μ+μt (5)
The RNG k- ε turbulence models that the present invention uses, turbulent dissipation item can be by following formula approximate calculation：
In formulaρFor fluid density, ε is tubulence energy dissipative shock wave.
Fig. 7 is the Entropy generation distribution situation of draft tube meridional plane under different jet amount, is penetrated it can be seen from figure 7 that working as
Flow is smaller when being 2%, and the loss of draft tube self-energy is focused primarily upon at right cone section wall surface, and Entropy generation is larger.With amount of jet
Gradually increase is from 2% to 8%, and the loss of draft tube self-energy is slowly to mobile, the Entropy generation maximum area at this in the middle part of right cone section
Domain scope constantly expands elongated, thus it is speculated that is and the tail water because jet stream is so that axial velocity straight down becomes larger in the middle part of draft tube
The original recirculating zone there are speed straight up in the middle part of pipe, the two converge collision and loss are caused to increase.In addition can be seen that, in curved elbow
The energy loss of section focuses primarily upon inside, the Entropy generation very little of diffuser.
Above to a kind of turbine draft tube vortex rope analysis method based on jet stream provided by the present invention, carry out in detail
It introduces, specific case used herein is set forth the principle of the present invention and embodiment, the explanation of above example
It is only intended to help the method and its core concept for understanding the present invention；Meanwhile for those of ordinary skill in the art, according to this
The thought of invention, there will be changes in specific embodiments and applications, in conclusion this specification content should
It is interpreted as limitation of the present invention.
Claims (3)
1. a kind of turbine draft tube vortex rope analysis method based on jet stream, it is characterised in that：Comprise the following steps：
Step 1, selected 15mm apertures down-off are 0.73QBEP, rotating speed be 900r/min operating point, QBEP=0.215m3/s；
Step 2, selected turbulence model and multiphase flow model, determine boundary condition；
Step 3, to carry out single-phase jet stream according to operating point information, turbulence model, multiphase flow model and definite boundary condition non-
Permanent calculating, so as to obtain the amount of jet information of the operating point；
Step 4 analyzes the shape of draft tube vortex rope according to amount of jet information；
It is step 5, axial to X-direction on the streamline of draft tube meridional plane and draft tube right cone section cross section according to amount of jet information
The distribution situation of speed radially is analyzed；
The Entropy generation of step 6, the performance to be recovered energy according to amount of jet information to draft tube and draft tube meridional plane is distributed
Situation is analyzed.
2. according to the method described in claim 1, it is characterized in that：The turbulence model be RNG k- ε models, multiphase flow model
For mixture models, the boundary condition is volute inlet liquid flow, draft tube outlet pressure and short tube inlet gas quality
Flow.
3. according to the method described in claim 2, it is characterized in that：The amount of jet is expressed as volume flow percentage, described
Step 3 obtains 4 groups of amount of jet information altogether, i.e. amount of jet is respectively 2%, 4%, 6% and 8% amount of jet information.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114091366A (en) * | 2021-10-23 | 2022-02-25 | 昆明理工大学 | Analysis method for influence of flow change on energy dissipation position in water turbine runner |
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| CN103726973A (en) * | 2013-12-30 | 2014-04-16 | 浙江理工大学 | Mixed-flow turbine draft tube improvement method based on energy gradient theory |
| CN106870247A (en) * | 2017-02-28 | 2017-06-20 | 哈尔滨工业大学 | A kind of draft cone drilling method based on hydraulic turbine whole flow field three-dimensional simulation method |
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2018
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| CN103726973A (en) * | 2013-12-30 | 2014-04-16 | 浙江理工大学 | Mixed-flow turbine draft tube improvement method based on energy gradient theory |
| CN106870247A (en) * | 2017-02-28 | 2017-06-20 | 哈尔滨工业大学 | A kind of draft cone drilling method based on hydraulic turbine whole flow field three-dimensional simulation method |
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| ALBERT RUPRECHT等: "《SIMULATION OF VORTEX ROPE IN A TURBINE DRAFT TUBE》", 《PROCEEDINGS OF THE HYDRAULIC MACHINERY AND SYSTEMS 21ST IAHR SYMPOSIUM》 * |
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| CN114091366A (en) * | 2021-10-23 | 2022-02-25 | 昆明理工大学 | Analysis method for influence of flow change on energy dissipation position in water turbine runner |
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Application publication date: 20180518 |