Embodiment
The technical scheme in the embodiment of the present invention is carried out below in conjunction with the accompanying drawing in the embodiment of the present invention clear, complete
Ground is described, it is clear that described embodiment is only a part of embodiment of the invention, rather than whole embodiments.Based on this
Embodiment in invention, the every other reality that those of ordinary skill in the art are obtained under the premise of creative work is not made
Example is applied, the scope of protection of the invention is belonged to.
The present invention provides a kind of hydraulic turbine draft cone drilling method,
Step 1, set up model measurement experimental system, design different draft cones punching models and carry out matching processing, according to
The draft cone of various configuration improves waterpower test experimental bed, carries out High frequency photographing measurement, obtains inside rotary wheel of water turbine and tail water
The experiment information of pipe vortex rope;
Step 2, selection turbulence model, carry out hydraulic turbine whole flow field three-dimensional non-steady using RANS analogy methods and simulate, catch
Vortex tape, draft tube vortex rope and entrance edge of blade separation of flow cavitation phenomenon between runner bucket are caught, is determined according to the phenomenon captured
The nascent place of vortex rope is produced, the place come into being in the vortex rope is punched;
Different draft cones under the inclined operating mode of different flow are punched mould by step 3, collective model experiment and numerical simulation data
Type is tested.
Measurement condition in the model measurement experimental system is using unit speed n11With specific discharge Q11It is complete to describe
Flow operating mode in runner, changes the ambient pressure level in test, by adjusting movable guide vane by adjusting means cavitation coefficient, cavitation factor, Toma coefficient σ
Aperture a changes unit speed and specific discharge;
Unit speed n11It is defined as:
D in formula1--- the runner diameter of model turbine, unit is m;
H --- model turbine tests head, and unit is m;
N --- the runner rotating speed in model turbine, unit is r/min;
Specific discharge Q11It is defined as:
Q in formula --- excessively stream flow in model francis turbine runner, unit is m3/s;
Plant cavitation coefficient σ is defined as:
H in formulava--- the vacuum values in model experiment circulation loop in tail tank, unit is m;
Ha--- the head that local atmospheric pressure is converted into experiment, unit is m;
Hs--- the draught-height of the hydraulic turbine in experiment, unit is m;
Hv--- the head that the saturated vapor pressure under experimental temperature is converted into, unit is m.
The model measurement experiment condition includes the inclined operating mode of low discharge and the inclined operating mode of big flow, and operating point parameter is:
The inclined duty parameter of low discharge takes a=16mm, n11=80.4r/min, Q11=0.486m3/ s, σ=0.258;
The inclined duty parameter of big flow takes a=28mm, n11=83.2r/min, Q11=0.768m3/ s, σ=0.277.
The turbulence model uses stress shear model.
The draft cone is the draft cone of short and straight type, and the draft cone punching is the draft cone for making a call to 2 holes, plays the sluicing in 2 holes
Bore as along axle center, the configuration of relative perforation.
The draft cone punching is the draft cone for making a call to 4 holes, along the axle center of draft cone relative to the draft cone for perforating into 2 holes,
It is vertical to wearing 2 holes in position relatively on the lower again on the basis of the draft cone in 2 holes.
Hydraulic turbine draft cone model experiment
Model experiment is the important method for studying flow behavior in the hydraulic turbine.In order to obtain the stream under the conditions of different draft cones
Field information and draft tube vortex rope information, experiment measurement has been carried out using model test of hydraulic turbine platform.
Rig for model test is located at Research Institute of Large Electrical Machinery hydraulic turbine research department of Harbin Electric Machine Co., Ltd., is one
High parameter, high-precision hydraulic machinery test stand, can carry out pump turbine, large pump and Francis Turbine with High Rated Head
Correlation test.
Waterpower experimental apparatus for testing numbering experiment 6, its test capability, the size of installable model, hydraulic performance
Method of testing and test water meet IEC60193-1999 requirement.Content of the test mainly includes:The energy examination of the hydraulic turbine
Test, the experiment of cavitation test, runaway speed, pressure fluctuation experiment, differential pressure flow measurement experiment, axial force experiment, stator Hydraulic Moment experiment,
Tonifying Qi experiment, abnormal low water head experiment etc., in addition, the fluidised form observation system of testing stand equipment can flow to the inside of hydraulic
State is observed.
As shown in figure 1, being waterpower test experimental bed critical component schematic diagram.This is equipped with high performance kinetic pump, stood
Formula structure dynamometer motor, high voltage bearing stainless steel pipe-line system, electrically operated valve, vavuum pump, high-precision tester and its original
Position calibration system etc..The high-precision electric control system of testing stand carries out quick to power-equipments such as supply-water pump and dynamometer motors
With high accuracy regulation control.The high-precision tester of testing stand equipment is measured to every test parameters.It is high performance
Data collection and precessing system is acquired and handled to data.
The main structure member of testing stand is as shown in table 1.
The testing stand main structural components of table 1
As described below is done to the said equipment:
Test speed:The rotating speed of experimental rig realized by dynamometer motor, dynamometer motor silicon controlled rectification power source
Power supply, can do four quadrant running, i.e., in forward and reverse rotation, can do generator operation can do motor running, therefore it again
The hydraulic turbine, water pump, the requirement of the various operating condition of test of pump-turbine different tests device can be met.
Test head and flow:Highest test head is 100m, and maximum stream flow is 1.0m3/s。
Test water:The efficient water treatment facilities of testing stand equipment are filtered to running water, used after sofening treatment
In experiment.This four experiments of the density of water, the viscosity of water, the gas content in water and steam pressure are primarily upon in test to use
The condition of water.
The measurement of atmospheric pressure:The atmospheric pressure of testing stand is measured using barometric pressure sensor, the atmospheric pressure
Measurement module is examined and determine in Weights and Measures Bureau of Heilongjiang Province every year, and calibration certificate is issued after assay approval.
The speed measuring system of hydraulic machinery test stand is made up of tachogenerator and the number of teeth for the 120 chi disk that tests the speed.
Speed probe is the MP-981 type speed probes that little Ye companies of Japan produce.The chi disk that tests the speed is arranged on hydraulic turbine arbor
Portion, the relative position of speed probe and the chi disk that tests the speed is as shown in Figure 2.The speed measuring system can measure 10000r/min's
Rotating speed.The electric impulse signal that velocity-measuring system is produced is directly entered data collecting system and data processing software is calculated.
On this waterpower test experimental bed, will also carry out runner in vortex tape and draft tube fluidised form observation, this mainly by
High-speed photography imaging system is completed.
Fluidised form observation system is by the stroboscope of German DRELLO companies, the fibre optic endoscopes of WOLF companies of Germany, number
Word industrial camera, synchronous trigger controller and image acquisition and processing work station are constituted, and can carry out real-time fluidised form observation, still image
Collection and dynamic files in stream media generation., can be existing to runner bucket front, the back side separation of flow and vortex tape cavitation by the system
As being observed.
, can be to the outlet edge of runner using fluidised form observation system in addition, by the transparent Taper Pipe at model test apparatus
The cavitation phenomenons such as karman vortex, cavitation inception, vortex rope are observed.The high-speed camera produced simultaneously using Olympus companies is entered
The high-frequency information of row vortex rope is caught.
The specification of fibre optic endoscopes is as follows:German WOLF companies production, size φ 10mm × 300mm × DOV50/
80/90 °, various visual angles are popped one's head in, diameter 10mm, and active length 300mm, 4m fix optical cable.
High-speed photography specification of equipment is as follows:Japanese Olympus companies production, model i-SPEED 2, cmos sensor, point
The valid pixel of resolution 800 × 600, frame rate reaches as high as highest 1000fps under 33000fps, minimum 1fps, full resolution, soon
The door microsecond of speed 5.Camera external controller display device, device is connect using standard LVDS, and 26 pin MDR are connected with photographic equipment
Connect.
In order to which the hydraulic stability to model hydraulic is estimated, pressure fluctuation experiment is generally carried out, pressure is carried out
Pulsation test is primarily to obtaining the pressure fluctuation relative magnitude and dominant frequency in the range of specific run and determining to reduce pressure
The optimal tonifying Qi mode of pulsation.
Pressure fluctuation is often measured using pressure pulsation sensor.The installation requirement diaphragm of pressure pulsation sensor with
Runner is concordant.As shown in figure 3, being mixed-flow, axial fixed blade propeller water turbine formula and the general installation site of pump turbine.Thoroughly do away with IEC test marks
The position of 4 pressure-measuring-points is as follows at standard, draft tube, and P1 is located at draft tube cone downstream, and P2 is located at draft tube cone upstream
Side, P3 is located at spiral case inlet, and the sensor that P4 separately increases is located at Taper Pipe and ell, in addition, setting P5 to survey between stator and runner
Point.
The 112A22 type dynamic pressure transducers that the measurement of pressure fluctuation is produced using PCB companies of the U.S., the sensor
Sensitivity 15mv/kPa, resolution ratio is less than 0.007kPa, and frequency range is 0.5-250kHz, and covering test machines can reach
Maximum excessively stream frequency, hydraulic pulse can quickly and accurately be responded.Testing stand high-speed data acquistion system is adopted with height
Sample rate is acquired to the response signal of pressure pulsation sensor, and usual sample frequency is 4000Hz.
The 903BO2 type dynamic pressures marking apparatus (essence that pressure pulsation sensor is produced with PCB companies of the U.S. before and after the test
Degree ± 0.2%FS) demarcated.
This waterpower test experimental bed, based on certain power station model turbine, hydraulic turbine maximum head 71m, minimum head
44m, rated head 57m.Model turbine runner (A1293) as shown in figure 4, the parameter of model runner and other important devices such as
Shown in table 2.
The model runner major parameter of table 2
In order to carry out flow measurement to various forms of draft cones, the draft cone various configuration in test, bag is given below
The situation for include the hole of prototype 0, making a call to 2 holes and make a call to 4 holes, as shown in Figure 5.
In model experiment, generally using unit speed n11With specific discharge Q11To describe flow operating mode in full runner, and if
Change the ambient pressure level in test, then need adjusting means cavitation coefficient, cavitation factor, Toma coefficient σ.Changed by adjusting movable guide vane aperture a
Unit speed and specific discharge.
Unit speed n11It is defined as:
D in formula1--- the runner diameter (low-pressure side) (m) of model turbine;
H --- model turbine experiment head (m);
N --- the runner rotating speed (r/min) in model turbine.
Specific discharge Q11It is defined as:
Q in formula --- excessively stream flow (m in model francis turbine runner3/s)。
For model measurement, plant cavitation coefficient has material impact for internal flow phenomenon.According to international electricity
The standard regulation of the work committee -60193, plant cavitation coefficient σ is defined as:
H in formulava--- the vacuum values (m) in model experiment circulation loop in tail tank;
Ha--- the head (m) that local atmospheric pressure is converted into experiment;
Hs--- the draught-height (m) of the hydraulic turbine in experiment;
Hv--- the head (m) that the saturated vapor pressure under experimental temperature is converted into.
According to being discussed above, using n11And Q11Carry out the operation operating mode of descriptive model experiment, as shown in table 3.These operating modes
In, including small guide vane operating mode and big aperture operating mode, it can observe the helical vortex under the tail water vortex rope of different shape, such as small guide vane
Column vortex rope under band, big aperture.
The experiment test operating point parameter of table 3
Hydraulic turbine whole flow field three-dimensional simulation method
Geometric Modeling
In the calculation, the full runner simulation of the hydraulic turbine has been used, and for the ease of numerical computations, has increased entering into spiral case
Mouth section part, import is round entrance, exports and is exported for elbow of draft tube.
Zoning be based on overall geometry model, it comprises volute inlet section, spiral case, fixed guide vane, movable guide vane, turn
7 parts such as wheel, draft tube and ell.
For this calculating, main Geometrical change part is draft cone, and Fig. 6 gives experimental study and numerically modeling
The draft cone of the middle different shaping used, including do not punch prototype draft cone, make a call to 2 hole draft cones and make a call to 4 hole draft cones.
Above-mentioned prototype draft cone is the draft cone of short and straight type, and the draft cone for making a call to 2 holes is the structure of relative perforation along axle center
Type, the draft cone for making a call to 4 holes is built on the basis of 2 holes are made a call to, vertical to wearing 2 holes in position relatively on the lower.
Grid is set
In order to preferably adapt to the 3D Flow Field Calculations that complexity is flowed in the full runner of the hydraulic turbine, to each portion of above-mentioned geometric configuration
Part has carried out mesh generation respectively, and the grid of different parts is attached using interface in the calculation, corresponding grid letter
Breath is as shown in table 4.
Each part gridding information of the full runner of table 4
It is that structured grid and unstructured grid are mixed to flow domain to calculate grid, under 7,000,000 quantity grids, Ke Yiman
The demand of sufficient numerical computations.
Numerical method
For full fluid flow on channel numerical simulation, this research is calculated using commercial CFD software ANSYS, is solved using CFX
Device is solved.CFX is the limited bulk discrete method based on finite element, and 24 point interpolations are used to hexahedral mesh unit, and
Simple finite volume method is only with 6 point interpolations.Calculated using multi-node parallel, difference scheme uses higher-order forms.
Calculating convergence criterion is residual error 10-5, Steady Flow calculating is first carried out, then using Steady Flow result as initial fields, enter
Row Unsteady flow computation.Because each part is using the method for building grid respectively in full runner, so on sound interface
Data transfer is needed to use, i.e., between movable guide vane and runner basin, Frozen is used between runner and draft tube basin
And Rotor series interfaces are combined.In addition, in the processing of flow field wall area, being described using Wall-function.
Boundary condition is set
Set according to the operating mode of model experiment, numerical simulation takes identical to calculate operating mode.
Given runner low-pressure side diameter D1After model experiment head H, the unit speed n provided according to experiment condition11、
Movable guide vane aperture a, now can obtain specific discharge Q by combined characteristic11.Therefore from n11And Q11Set out, have:
Actual speed:
Actual flow:
If the cross-sectional area at spiral case inlet is S, inlet velocity is:
V=Q/S (6)
In addition, according to plant cavitation coefficient σ calculating formulas above, needing to set draft tube outlet pressure in numerical simulation.
According to the above, the boundary condition in numerical computations sets as follows:
Entrance:Using volute inlet extension as entrance, using mass flow condition for import, while setting reference pressure, just
The parameters such as beginning turbulence intensity.
Outlet:Exported by flowing of ell outlet, using pressure export condition, the value is provided by above-mentioned cavitation conditions,
Provided with absolute pressure numerical value.
Wall:All solid wall surfaces are used without slip boundary condition, and near wall region flowing carries out mould using Wall-function
Intend.
Governing equation
Consider that the flowing in the full runner of the hydraulic turbine is incompressible Three-dimensional Flow, and ignore and extraneous energy exchange, then
Governing equation includes continuity equation and the equation of momentum.
Continuity equation (when incompressible, density p does not change with time and space):
The equation of momentum:
When solving the full runner Three-dimensional Flow of the hydraulic turbine, average flow field calculation is carried out using Reynolds average method (RANS), and
Corresponding turbulence model is set to carry out eddy stress closing.In the present invention, using k- ω SST, (stress shears mould to closing turbulence model
Type) model, the model got up standard k-ε model with k- ω models couplings using mixed function, is contained and is turned to twist and shear choosing
.K- ω SST model equation is as follows.
K equations:
ω equation:
Wherein, G, Г and Y represent respective generating item, effective diffusion term and dissipative term respectively, and D represents orthogonal diverging item, S
For user-defined source item.
In addition, the model and standard k- ω model differences are α∞Value, the parameter in standard k- ω models
For constant, and in k- ω SST models, α∞It is defined as follows:
α∞=F1α∞,1+(1-F1)α∞,2 (11)
Wherein have:
K- ω SST model combinations derive from the cross-diffusion in ω equation, and turbulent viscosity take into account that turbulent flow cuts should
The propagation of power.It the advantage is that there is preferable processing near wall region and main flow area, and model is without complicated nonlinear dampling
Function, therefore more stablize and accurate.
In order to analyze influence and the corresponding Pressure Fluctuation in Draft Tube information that full runner flow field flows to draft tube, herein
4 pressure-measuring-points that the standard of International Electrotechnical Commission -60193 have chosen draft tube region are analyzed, i.e., below Taper Pipe away from
From outlet of rotary wheel side 0.3D2Measuring point (Taper Pipe+the Y0.3D of left and right 2 at place2、-Y0.3D2), and draft tube and a left side for ell junction
Right 2 measuring points (on the inside of ell, on the outside of ell).There is identical pressure fluctuation measuring point in model measurement and numerical simulation.
In the pressure fluctuation experiment of model measurement, what measuring system was collected is only voltage change signal, passes through voltage
Demarcation and conversion after obtain pressure signal value.And in numerical computations, by the simulation in flow field, flow field letter will be directly obtained
Velocity fluctuation and pressure fluctuation signal value in breath, the pressure fluctuation acted on wall will be carried out directly with model experiment results
Compare.
In order to be analyzed the pressure fluctuation in time domain, it is necessary to obtain the amplitude information and frequency information of pressure fluctuation,
Simultaneously in order to do dimensionless processing to frequency, frequency multiplication f ' is defined, frequency multiplication f ' can be obtained by given frequency f divided by a turn frequency.From
Time-domain information is transformed into frequency domain information, it is necessary to by Fourier transformation:
Formula also turns into Fourier's direct transform above, can so obtain the pulsation energy under pressure fluctuation signal each frequency
Information.
Under certain frequency f, the amplitude of pressure fluctuation A for decompositing signal is calculated as follows:
R is the real part of frequency-domain function in formula, and I is imaginary part, and n is sampling number.
Due to the geometry spacing between entrance edge of blade and movable guide vane closely, the interference that both high fdrequency components are produced
The raising of the high frequency pressure pulsations amplitude interference effect will be caused to be further magnified pressure fluctuation, cause operation stability
It is deteriorated.
Finally, the amplitude under each frequency is drawn on frequency domain axle, has just obtained the frequency domain variation diagram of pressure fluctuation signal
Spectrum.
Hydraulic turbine flow field numerical computations
According to model experiment introduction, the present invention is calculated the flow field under inclined operating mode, chooses two differences under aperture
Flow operating mode, specific duty parameter is as shown in table 5.
The numerical computations operating point parameter of table 5
In above-mentioned operating mode, calculated for 3 kinds of different draft cone configurations, i.e. the geometry in the hole of prototype 0,2 holes and 4 holes
Shape.It is pointed out that guide vane opening a=16mm is close to optimal aperture line 17mm, unit speed n11=80.4r/min also connects
The unit speed value 74.5r/min of nearly optimum operating condition;Guide vane opening 28mm is close to power limit line, the measurement condition unit speed
Also it is higher, it is 83.2r/min.Therefore the 1st operating mode is the inclined operating mode of low discharge, the 2nd operating mode is the inclined operating mode of big flow.
It is more smooth for the flowing inside runner on the runner flow field information under the conditions of low flow rate condition, but in leaf
The porch of piece suction surface occurs in that streamline inflection, it is meant that flowing flow back, backflow generally mean that vortex appearance and
The presence of low-pressure area, so in this case, easily there is the presence of the cavitation band, i.e. vortex tape in impeller clearance.
In order to further illustrate the flow field situation in runner, from axial flow direction, choose three horizontal cross-sections to carry
Velocity field is taken, the entrance of blade suction surface occurs in that certain flow starts back, and back-flow velocity is larger, but impeller clearance
Downstream, flowing is more smooth and more uniform, and flowing circumferentially is gentle.Meanwhile, during close to outlet edge, flowing velocity has become
Very little, because herein close to draft cone, therefore be the nascent place of vortex rope.
The inclined operating mode lower tail water flow field comparative analysis of low discharge
Vortex rope in experiment under inclined operating mode occurs vibrating and coming into being change in location, is first provided used here as method for numerical simulation
Pressure lowermost extent near draft cone.For the position punched in guiding experiment, inclined operating mode lower tail water pipe sections are provided first
Pressure distribution.In inclined operating mode (a=16mm, σ=0.258, n11=80.4r/min) under, Fig. 7 gives the hole draft cone of prototype 0
Draft tube partial pressure top view.
From figure 7 it can be seen that the pressure distribution partially under operating mode in draft cone and draft tube partial cross sectional is asymmetric, it is circumferential
Pressure distribution somewhere has minimum value.Provide separately below along the pressure distribution on one week its surface of draft cone, such as Fig. 8 institutes
Show.
From figure 8, it is seen that the pressure distribution of draft cone and draft tube partially circumferentially also occurs asymmetric, draft cone is leaned on out
There is pressure minimum point in oral area point, after the pressure is less than local local pressure, that is, vortex rope occur., it was also found that should in experiment
Place is the place for producing vortex rope, but under the operating mode, the phenomenon of vortex rope bob also occurs.In order to eliminate the phenomenon, in whirlpool
The nascent place of band, implements punching measure, it is therefore an objective to will balance the inside and outside water flow pressure of draft cone, utilize flow equilibrium shadow
Pressure distribution is rung, and then vortex rope position is further moved down, and reduces vortex rope up and down motion, while reducing its caused pressure arteries and veins
It is dynamic.
Fig. 9 further provides the tail water flow field plane pressure distribution top view that inclined operating mode is made a call under the conditions of 2 holes.Figure 10 is further
Provide draft cone surface pressure distribution under inclined operating mode and (make a call to 2 holes, a=16mm, σ=0.258, n11=80.4r/min), it is necessary to note
, Fig. 9 is consistent with Fig. 7 and Fig. 8 with the pressure distribution threshold value that Figure 10 is provided.As can be seen that after punching, draft cone
It is obviously improved with draft tube partial interior pressure.And the difference of the maxima and minima of pressure distribution diminishes.
In Figure 10, draft cone surface pressure distribution on circumferencial direction is given.As can be seen that the stress level around punching
Also there is lifting.Meanwhile, compare above and below two row figures as can be seen that the pressure size around punching in relative position is different, this is
Because tail water vortex rope is the reason from side generation.
Predictably, after pressure distribution improvement near draft cone, the form of tail water vortex rope should also become
Change, while its pressure fluctuation will also change.
Continue with the distribution of tail water partial pressure and the draft cone surface pressure distribution for providing and making a call in the case of 4 holes.
Figure 11 is tail water partial pressure distribution when making a call to 4 hole.As can be seen that making a call under the conditions of 4 holes, pressure in draft tube distribution water
It is flat further to have been lifted, while the difference of the maxima and minima of pressure also diminishes.The pressure distribution of same sluicing poppet surface
As shown in figure 12, the press water around punching averagely has lifting.It can be seen that, under inclined working condition, punch for stress level
Lifting serves positive effect, and the gradient of pressure distribution has also slowed down.
In order to further illustrate influence of the punching measure for flowing, the vortex rope situation of change under inclined operating mode is given below:
When vortex rope shape is extracted, identical vorticity criterion is used under three kinds of configurations, using identical cavitation pressure
Determine void volume fraction.Compare three kinds of situations to can be seen that first, with the implementation of punching measure, the leaf road inside runner
Whirlpool is gradually decreased, and its void volume diminishes, and vortex structure becomes in small, broken bits;Secondly, the whirlpool below draft cone region, draft cone
The nascent region of band, its cavitation whirlpool volume is obviously reduced.The reduction of cavitation site, contribute to reduce vortex rope itself vibration and
Bounce, has positive effect for reducing pressure fluctuation.
Vortex rope after above-mentioned punching induces pressure fluctuation level, can provide, can obtain in follow-up pressure fluctuation is calculated
To the pressure fluctuation substantially weakened.
Big flow optimum operating condition lower tail water flow field comparative analysis
Under the inclined working condition of low discharge, it can be seen that punching measure substantially reduces stress level, this is given below and arranges
Apply the performance under big flow operating mode.Optimum operating condition is farther out in the operating mode, however it remains vortex rope, and simply different shapes are presented in vortex rope
State.
In the inclined operating mode of big flow (a=28mm, σ=0.277, n11=83.2r/min) under, Figure 13 gives the hole of prototype 0 and let out
Water cone draft tube partial pressure top view.As can be seen that the pressure distribution of draft cone and draft tube partially circumferentially has well
Symmetry, low-pressure area is located at draft cone peripheral part, and this part is the nascent place of vortex rope.
Figure 14 gives the vortex rope point shape under the operating mode, shows column vortex rope.And then, the pressure point of sluicing poppet surface
Cloth is presented in Fig. 15, including the pressure distribution on 4 directions of draft cone one week.As can be seen that in one week side of draft cone
Upwards, low-pressure area is present in the place of draft cone outlet, here, and pressure is less than after local pressure for vaporization, will produce cavitation
Vortex rope.This and pressure distribution are consistent.
Pressure in draft tube distribution and draft cone surface pressing score that nearly optimum operating condition is made under the conditions of 2 hole draft cones is given below
Cloth.As shown in FIG. 16 and 17, although the pressure distribution of draft cone outlet changes, but still symmetrically, and its stress level
Lifted.Identical trend can also observe under the conditions of the draft cone in 4 holes is made a call to, as shown in Figure 18 and Figure 19.
Although above-mentioned pressure distribution is similar, with the implementation of punching measure, stress level has lifting, and this will influence the work
The vortex rope shape of condition.Figure 20 has been given under nearly optimum operating condition, is made a call to 2 holes and is played the draft cone vortex rope distribution in 4 holes.
In the case of above two draft cone, the straight vortex rope of elongated column is presented in tail water cavitation, and cavitation band is smaller.And with
Number increase is punched, cavitation band diminishes, this is the vortex rope change basic condition under big flow operating mode.Simultaneously it can also be seen that punching
Afterwards, the cavitation whirlpool distribution at outlet of rotary wheel is obviously reduced, and is only a small amount of concentrate on around draft cone outlet.This should be by
The flow regime of vortex rope is changed in punching measure.
Under these conditions, stronger cyclone structure is still suffered from draft tube, but vortex rope form is relatively stable, also has one
Fixed pressure fluctuation.
Pressure fluctuation result of calculation under inclined operating mode
Under big flow operating mode, the unit typically chance of operation in this place is smaller, or run time is shorter.It is primarily upon below
Pressure fluctuation under the inclined operating mode of low discharge.
When pressure fluctuation is calculated, the stable state Three-dimensional simulation under the operating mode is carried out first, and wait is flowed into fully
After state of development, then the numerical simulation of transient state is carried out, 1 ° is often rotated with runner for material calculation, while monitoring pressure fluctuation water
It is flat.
The inclined operating mode of low discharge (a=16mm, σ=0.258, n is given below11=80.4r/min) lower three kinds of draft cone configurations
Under pressure fluctuation result, for 4 measuring points result as shown in figure 21, pressure fluctuation using Fourier change carries out
Frequency domain is converted, and EDF (PSD) distribution corresponding under each frequency is provided in figure.
As can be seen from Figure 21, under inclined operating mode, the pressure fluctuation level on the right side of Taper Pipe is minimum, and on the left of Taper Pipe, ell
The equal highest of pressure fluctuation level on the outside of inner side and ell.After punching measure is implemented, with the increase of punching quantity, pressure arteries and veins
Dynamic energy is gradually reduced, and this is consistent with the development trend of pressure distribution in flow field and vortex rope.
In addition, with punching quantity increase, ell inner side and the pressure fluctuation energy on the outside of ell decline the most substantially, energy
Enough drop to 1/2 of original level or so.This suppression of explanation punching measure really for pressure fluctuation plays an important roll.
Finally, it can be seen that the Energy distribution on the outside of ell also occurs compared with multi -components at upper frequency, although this illustrates
At dominant frequency, pressure fluctuation occupies most energy, but still has very important contribution at upper frequency.It can obtain,
If all pressure fluctuation energy of superposition, then the pressure fluctuation energy in ell outside is highest in 4 measuring points, this
Experiment measurement with back is consistent.But, because the population value of pressure fluctuation energy is to decline after punching, unit
Noise during operation will be substantially reduced, and also having obtained experiment confirms.
Turbine draft tube flow field experimental study
The inclined operating mode of low discharge is mainly selected in experiment, energy and efficiency experiment have been carried out first.
The energy and efficiency experiment parameter of the different draft cone configurations of table 6
As shown in table 6, under the operation of inclined operating mode, frequency about 18.6Hz is turned, the dominant frequency of tail water vortex rope is 0.242 relative to frequency is turned
Times, this is basically identical under three kinds of draft cone configurations.Efficiency is derived according to energy, it is known that whole efficiency changes after punching
Very little, only there is a little reduction when making a call to 2 hole, and has been raised on the contrary making a call to 4 holes.Change and the pressure fluctuation change of efficiency should have
Relation, pulsation energy reduction, energy loss then reduces, and efficiency has then been lifted.
As can be seen that punching measure does not interfere with the overall operation efficiency of unit substantially, therefore very little is influenceed on Energy Test.
It may be speculated that punching measure can only influence the downstream part flow field in full runner, it will cause the speed arteries and veins in draft tube flow field
Dynamic and pressure fluctuation reduces, and such noise also accordingly reduces.Therefore it is a kind of effective measures of Local application cavitation optimization.
Experimental analysis will be carried out to draft tube flow field below.Laboratory facilities are model experiment, in transparent tail water tube portion, are adopted
Flowed with the method for high-speed photography and vortex rope shooting, prototype draft cone draft tube vortex rope evolution sequential is observed.
Under above-mentioned operating mode, cavitation vortex rope runs one week about 216ms, it is known that tail water vortex rope frequency is about 4.5Hz.
Helical form is presented in vortex rope under the operating mode, is revolved round the sun around draft cone center.Examining vortex rope operation sequential can
To find out, the vortex rope in 36ms, 96ms and 108ms has vortex rope 2 to 3 strands thinner to overlap, and its around itself
Helical center is also in rotation.Also, the initial position of vortex rope also occurs in that the phenomenon along sluicing poppet surface bob.
A plurality of thin vortex rope produce should with vortex rope at draft cone come into being position it is relevant, have low on sluicing poppet surface
Nip zone is larger, then many places cavitation inception region easily occurs.And numerical simulation is also indicated that, the hole of prototype 0 is let out under the operating mode
Water cone surface bottom portion has many places vortex rope to come into being point, it is seen then that numerical simulation result and experiment meet preferably.
If in addition, considering cavitation vortex rope for the contribution of pressure fluctuation energy, can reasonably speculate has:The public affairs of vortex rope
Turn to contribute to the dominant frequency of pressure fluctuation, and itself rotation around helical center then contribute to the higher-frequency energy of pressure fluctuation.
High fdrequency component of the Francis turbine without the pressure fluctuation of leaf area be not obvious, and the ratio that amplitude accounts for mixing amplitude is smaller.
Also there is the multiple frequence component of blade passing frequency without the pressure fluctuation of leaf area, high frequency arteries and veins all in all is presented without the pressure fluctuation of leaf area
Dynamic feature.For punching measure, it is possible to reduce dominant frequency energy, be also possible to reduce higher-frequency energy, or also have can
It can reduce simultaneously.
In order to systematically analyze influence of the punching to pressure fluctuation, different sluicing are given below under the inclined working condition of low discharge
The vortex rope evolution condition of cone.Vortex rope evolution sequential when observation makes a call to 2 holes and makes a call to 4 hole respectively.As can be seen that for letting out after punching
Water cone, although the region of the local cavitation inception exported in draft cone is substantially reduced and (makes a call to 2 holes) or even disappears (making a call to 4 holes), but by
In the presence of punching, using hole as starting point, comparatively fine vortex rope is occurred in that, the thick spiral vortex of the hole draft cone of prototype 0 is instead of
Band.And with the application of punching measure, the phenomenon of vortex rope bob weakens or eliminated, originally thicker especially when making a call to 4 hole
Spiral vortex band be dispersed through very thin single vortex rope, and almost disappeared at some moment.
It is pointed out that under the conditions of above-mentioned punching, although the volume of cavitation has reduced, but it can be seen that sometimes
Still exist there are still thinner dual vortex rope, the i.e. cavitation energy under high frequency state, will be according on pressure fluctuation frequency spectrum
Old higher-frequency peak value is present.
Finally, to (a=28mm, σ=0.277, n under the inclined operating mode of big flow11=83.2r/min) vortex rope form seen
Survey, it can be seen that under the inclined operating mode of big flow, regardless of draft cone configuration, column is presented in vortex rope form, and its diameter becomes
Change very much not.But from experiment from the point of view of vibration and noise observation, the noise level for punching draft cone is relatively low.In addition, above-mentioned whirlpool
The shape of band and the result of numerical simulation are consistent.
Pressure fluctuation in draft tube of water turbine is analyzed
While vortex rope develops and observed, the monitoring of pressure fluctuation has also been carried out.The method according to model experiment is tested, will
Pressure probe is embedded to draft tube wall, so as to detect flow field effect and the pressure value on draft tube wall, and records it with the time
Situation of change.The pressure fluctuation experimental result to 4 monitoring points is analyzed below.
Fourier's change is carried out to initial pressure ambient experiment data, directly Energy distribution of being pulsed under inclined operating mode can be entered
Row analysis.The inclined working condition experimenting result of low discharge shows that after punching measure is implemented, the integral level of pressure fluctuation has all declined,
On the outside of ell, dominant frequency amplitude is reduced by up to.For the pressure-measuring-point (+Y0.3D2 ,-Y0.3D2) of Taper Pipe part, after punching,
The pulsation energy of higher-frequency is decreased obviously, and is disappeared in the operating mode for making a call to 4 holes.
In addition, test result indicate that, before punching, the pressure fluctuation energy on the outside of ell is maximum, its amplitude after punching
Decline the most notable.Compared with numerical simulation result, experimental result demonstrates the result of numerical simulation, pressure fluctuation well
Integral level have decline after punching, it is effective also to illustrate the measure punched on draft cone.
In order to which the energy to pressure fluctuation is quantitatively illustrated, it is given below under different operating modes and is directed to different sluicing wimble structures
Obtain ambient experiment data.According to IEC testing standards, the assessment to pressure fluctuation uses mixing double-amplitude amplitude (peak-to-peak value)
Δ H/H is represented.As shown in table 7,8,9 and 10, on the outside of respectively Taper Pipe+Y0.3D2, Taper Pipe-Y0.3D2, ell inner side and ell
The pressure fluctuation characteristic data of measuring point.
As can be seen that in the inclined operating mode of low discharge, spiral vortex band is more stable, dominant frequency and the ratio for turning frequency are about 0.24,
With the increase of punching quantity, pulsation peak-to-peak value constant interval is little.The change more significant pressure under the inclined operating mode of big flow
Power is pulsed, except on the inside of ell, remaining measuring point is in punching configuration, and its dominant frequency is substantially reduced with turning the ratio of frequency, and dominant frequency reduces
Prototype draft cone operating mode of the value more than 1/2 times.Also, the reduction of dominant frequency has likely via the decrease and disappearance of vortex rope in experiment
Close, some moment, have the discontinuous phenomenon of vortex rope in draft tube.Particularly, for making a call to the operating mode in 4 holes, sluiced all
Bore in configuration, the energy peak-to-peak value of dominant frequency, which has, to be substantially reduced, it is seen then that punching measure is effective.
Taper Pipe+Y0.3D under the different operating modes of table 7 and draft cone configuration2The pressure fluctuation characteristic of point
Taper Pipe-Y0.3D under the different operating modes of table 8 and draft cone configuration2The pressure fluctuation characteristic of point
The pressure fluctuation characteristic of ell inner side measuring point under the different operating modes of table 9 and draft cone configuration
Under the different operating modes of table 10 and draft cone configuration on the outside of ell measuring point pressure fluctuation characteristic
In addition, it should be noted that when movable guide vane aperture increases, the dominant frequency pulsation of draft tube inlet and ell outlet
Peak-to-peak value decreases, and this means that the corresponding high fdrequency component of pressure fluctuation becomes readily apparent from.Beaten to further determine that
Energy magnitude behind hole, here by first three order frequency (f1, f2, f3) energy of pressure fluctuation carried out plus and, it is whole for characterizing
Physical efficiency amount, as shown in table 11.As can be seen that first three rank energy summation reduces with the increase of punching quantity.On the whole, punch
Generation and relevant pressure pulsation of the measure for weakening vortex rope have positive effect.
First three order frequency energy feature Δ H/H (%) of pressure fluctuation under the different draft cone configurations of table 11
Above to a kind of hydraulic turbine draft cone drilling method provided by the present invention, it is described in detail, herein should
The principle and embodiment of the present invention are set forth with specific case, the explanation of above example is only intended to help and managed
Solve the method for the present invention and its core concept;Simultaneously for those of ordinary skill in the art, according to the thought of the present invention,
It will change in embodiment and application, in summary, this specification content should not be construed as to this hair
Bright limitation.