SMALL WIND TURBINE AERODYNAMICS: OLD WINE IN NEW BOTTLE

7/30/2019 SMALL WIND TURBINE AERODYNAMICS: OLD WINE IN NEW BOTTLE

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SMALL WIND TURBINE AERODYNAMICS: OLD WINE IN NEW BOTTLE

Rudolf A. Izmaylov HonourableProfessor, Dr. Sci (Tech)

Saint Petersburg State Polytechnic University,St. Petersburg, Russia,[email protected]

Sergey Y. Dudnikov Cand. Sci. (Phys-Math), Optiflame Solutions, SaintPetersburg, Russia

Alexander A. Lebedev Cand. Sci. (Tech),

St. Petersburg State PolytechnicUniversity,

Saint Petersburg, Russia,

Evgeny N. Khoroshev Optiflame Solutions,Saint Petersburg, Russia,

Yuri S. Chumakov Prof., Dr. Sci. (Tech),St. Petersburg State PolytechnicUniversity, Saint Petersburg,Russia

ABSTRACTResults of aerodynamic design and detailed tests

of small wind power generator fulfilling the condionof safety for avians and living beings are presented.Based on the idea of Seiti Awano and ring airfoil

shroud proposed by Kort the small wind tubine usedaxial flow turbine. Detailed CFD calculations andseries of tests in wind tunnel and towing by car ptrmitto fulfil the goal.

INTRODUCTIONOur predecessors were Pierre Bollée [4],

producing wind turbine for pump drive, based onshrouded axial flow turbine (fig. 1-a), and SeiitiAwano [1], constructing similar turbine for Antarctic polar station (fig. 1-b). Using Awano design as a prototype we applied aerodynamically profiled ringshroud based on Kort nozzle (fig. 1-c) [3], which

increases to some extent the level of flow inletvelocity in front of the guiding vanes. In such a waywe get a new construction permitting to overcomeunfavorable features of well known typical windturbine with propeller blades. Inlet guide vanes arethe means for protection of avian, the shroud is usefulas a means for protection in case of rotor bladesdestruction, all the design excludes flicker effects of TV signals and decreases radiated noise level.

a)

b)

c) Fig. 1. Predecessors: a) Éolienne Bollée [4], Awano

NU-102 [1], Kort Nozzle [3]



Aerodynamic design of the axial flowturbine was based on J.H. Horlock methods [2].

Fig. 2. Cross-sectional view of the axial flow turbine[1]

The inlet air velocity in front of the shroudat the design point was 10 m/s, ambient condition –

standard atmosphere. Hub to tip ratio – 0.5, overalldiameter – 0.5 m. Number of blades – variable.Profiles are of TA6 type (due to manufacturing problems we choose simple circular arcs for the test).Profile chord is 30 mm, relative thickness 0.05.

Inlet/outlet angles 0◦

/45◦

.(Fig. 2)

Airfoil NACA 4415 was chosen for ringshroud, relative thickness 0.1875. Overall length – 160 mm.As the ring wing airfoil was selected profile NACA4415 and were made of different optionsconfigurations of the model table 1, 2 for thedetection of numerical modeling of CFD(Computational fluid dynamics) of the most suitablevariant. These data allowed us to choose aerodynamicscheme of things we do wind turbinesPROF4415_AT750100.

Table 1. Model selection based of the profile 4415.

Profile

chordlength,mm

profilecurvature

internaldiameter,mm

PROF4415_LD500 500 0,5 1000PROF4415_LD750 750 0,5 1000PROF4415_LD1000 1000 0,5 1000PROF4415_LD1250 1250 0,5 1000PROF4415_LD1500 1500 0,5 1000

PROF4415_LD50015 500 0,5 1500PROF4415_LD75015 750 0,5 1500PROF4415_LD100015 1000 0,5 1500PROF4415_LD150015 1500 0,5 1500PROF4415_LD50007 500 0,5 700PROF4415_LD75007 750 0,5 700PROF4415_LD100007 1000 0,5 700PROF4415_LD125007 1250 0,5 700PROF4415_LD150007 1500 0,5 700PROF4415_KR500 500 0,2 1000PROF4415_KR750 750 0,2 1000

PROF4415_KR1000 1000 0,2 1000PROF4415_KR1250 1250 0,2 1000PROF4415_KR1500 1500 0,2 1000PROF4415_KR5001 500 1 1000PROF4415_KR7501 750 1 1000PROF4415_KR10001 1000 1 1000PROF4415_AT75095 750 0,1 1000PROF4415_AT100095 1000 0,1 1000PROF4415_AT750100 750 0,1 1000PROF4415_AT1000100 1000 0,1 1000PROF4415_AT1250100 1250 0,1 1000PROF4415_AT1500100 1500 0,1 1000PROF4415_ATL175095 750 0,1 1500PROF4415_ATL1100095 1000 0,1 1500PROF4415_ATL1125095 1250 0,1 1500



Table 2 Characteristics of calculated models:.

ModelOutputarea, m2

InputPressure,

Pa

Power,Wt

Entrancespeed,

m/s

Outputspeed,

m/s

Averagethroatspeed,

m/s

Maximumthroat speed,

m/sPROF4415_LD500 2,320 101332 602,21 9,38 10,06 13,81 16,67PROF4415_LD750 2,406 101334 659,74 9,23 9,54 13,74 15,59PROF4415_LD1000 2,493 101333 672,25 9,71 9,76 14,37 15,68PROF4415_LD1250 2,581 101331 619,42 9,50 9,53 14,26 15,27PROF4415_LD1500 2,671 101328 594,16 9,72 9,54 14,94 15,70PROF4415_LD50015 1,304 101332 395,59 9,67 8,35 15,49 17,62PROF4415_LD75015 1,390 101333 198,67 9,66 8,17 15,71 17,05PROF4415_LD100015 1,477 101332 452,51 10,34 8,66 17,58 18,84PROF4415_LD150015 1,655 101328 405,58 10,06 8,17 17,35 18,41PROF4415_LD50007 2,741 101330 567,19 9,42 9,89 13,01 15,94PROF4415_LD75007 2,827 101328 523,13 9,71 9,78 13,27 15,35

PROF4415_LD100007 2,914 101325 430,89 10,08 9,91 13,98 15,76PROF4415_LD125007 3,003 101320 275,08 10,36 10,20 14,78 15,94PROF4415_LD150007 3,092 101314 160,36 10,82 10,40 15,50 16,42PROF4415_KR500 2,222 101335 581,53 9,17 10,11 13,48 16,29PROF4415_KR750 2,257 101336 599,13 9,16 9,86 13,40 14,97PROF4415_KR1000 2,293 101338 607,07 8,80 9,82 13,55 14,87PROF4415_KR1250 2,328 101333 524,11 9,25 9,83 13,73 14,70PROF4415_KR1500 2,364 101332 516,28 9,44 10,41 14,96 15,83PROF4415_KR5001 2,487 101330 724,09 9,53 9,82 14,21 17,35PROF4415_KR7501 2,661 101331 744,00 9,51 9,31 14,28 16,24PROF4415_KR10001 2,840 101328 751,02 9,80 9,24 14,79 16,38

PROF4415_AT75095 2,618 101328 600,06 9,49 9,69 14,23 16,1PROF4415_AT100095 2,781 101330 713,37 9,43 9,43 14,29 15,58PROF4415_AT750100 3,059 101323 760,23 10,17 9,3 14,66 16,53

PROF4415_AT1000100 3,389 101321 691,30 10,36 8,79 14,65 16,34PROF4415_AT1250100 3,731 101318 743,53 10,81 8,70 15,50 17,29PROF4415_AT1500100 4,087 101318 682,55 10,75 8,05 15,37 17,06PROF4415_ATL175095 1,602 101324 425,32 10,29 8,14 15,63 17,26

To confirm the correctness of the choice of the

form of the profile model shells of the carried outexperimental research on the measurement of profilesof speeds with the help of hot wire anemometers (Fig.

3). Results of numerical modelling of flow around aCFD model wind turbine are presented in Fig.4, 5.The flow patterns obtained in the experiment and thenumerical simulation has qualitative coincidence, andalso the coincidence of the power, this testifies to thecorrectness of a choice of the wind turbine geometryand techniques for its calculation.

Figure 3. Aerodynamics of wind turbine velocity profiles, model Ø500, wind tunnel experiment.



Figure 4. CFD calculation results of flow condition insmall wind turbine.

Figure 5. CFD calculation results of flow in windsmall wind turbine.

To confirm the calculated wind turbinecharacteristics the size of more than 2 meters wasrequired to consider and select the methodology of experimental research. For the research of the modelcame several variants of this test in a large windtunnel, full-scale field trials in places with strongwinds, as well as the method of towing on a platformwith a constant speed. Of all the options we haveselected the method of towing, as the large windtunnel is very expensive and is available at the priceof only large manufacturers of aerospace field, andfield trials are not feasible because of its timingrestrictions. test method of towing wind turbine waschosen with different velocities. The advantage of this method in comparison with tests in the windtunnel are: low price, availability, the possibility of amore accurate measurement of small velocities.

The velocity of the incoming flow was measured by anemometer with access to USB, laptop withmulti-channel digital oscilloscope for registration of acurrent and voltage on resistor load. Also wasrecorded air temperature and atmospheric pressure.

Wind turbine was towed at different speeds, inmotion with a constant velocity. The register of theelectrical parameters to get the values of the power for different selected by the operator of the electricalload. Before towing was determined by therelationship between the mechanical power, lodgedon the axis of the electric generator and the output of electric power at various speeds working range of wind turbines. As coefficient of conversion of mechanical power into electricity, knowledge of thisfactor allowed us, then the output of electrical power,registered in the on-board computer was transformedin aeromechanical power of the wind power plant.

Before carrying out the towing of the models of more than 2m it was decided to carry a comparison of methods of towing and blowing in the wind tunnel of model 500 mm, and carried out numericalmodelling of flow around the car to determine themounting height of the model over the roof of the car,in order to obtain a homogeneous the oncoming flowof the wind-turbine. This study has shown that at awind speed 5 and 10 m/with height mounting model1 m from the roof of the car to the lower overalldimensions of the shhroud is sufficient for satisfactory quality of the homogeneity of the flow(not more than 10%).

Fig. 6 shows photos of wind turbines withanemometers (on the right photo on the backgroundof the sky), and wind-driven electric plants with thetug. Wind tunnel of University (fig 7) was chosen for detailed test with measurements of velocities byhotwire anemometers and pressure pulsations on theshroud.

For towing a platform for small model car VAZ21074 was chosen, as a result of testing of the modeltowing was obtained characteristics of power (fig 8).Aerodynamic wind tunnel St. Petersburg StatePolytechnic The tunnel has a diameter of theworking area 2 m. The mode of the output of the

generator connected discrete variable three-phaseelectrical load, thus varied power generated at thegenerator, and registered characteristics of the wind power plant.

Comparison of experiments method of towing and in a wind tunnel model Ø 500.of the samegeometry, namely the configuration of the ring wingshroud, the flowing part of the diffuser and theimpeller on the basis of the received results fig.8 andfig. 9, we can see that the characteristics are similar,and the values of capacities power characteristics atthe two test methods allow to make a conclusionabout the suitability of the application of the method

of towing to obtain the characteristics of windturbine.



Fig. 6. Complete turbine Ø500mm installed on theroof of a car

Figure 7. Wind tunnel of SPSU and wind generator

Experimental study of aerodynamic windturbine size of more than 2m when towing the vehicle

consisted of five stages. The first step is to install therequired resistor load; the second stage is the beginning of the movement of the car with thesubsequent acceleration up to the required speed tomode, the velocity was determined by anemometer;

the third stage - motion with constant speed for thestabilization of the frequency of rotation of a rotor of the turbine, the power of the turbine mode; the fourthstep is the registration of information with the dataacquisition devices, oscilloscope and theanemometer; the fifth stage - smooth stop.

As a power meter was selected electricalgenerator, but to accurately determine theаэромеханической power it took an experimentalstudy of the generator (figure 10) under differentloads in the range rotation frequency of the generator,expected in the tests of wind turbine.

Electrically generator is a three-phase electric AC,

with a rotor with permanent magnets. In the chain of transmission of the aeromechanical energy there ismultirib belt transmission, its efficiency is highenough (0.95 0.97%).



Figure 8. Power of wind turbine model Ø500, obtained by towing.

Figure 9. Characteristics of wind generator model Ø500 obtained in a wind tunnel.



As an electric power from the generator performed load, collected from resistor under thescheme «star», with a step of discrete load 0.5, 1, 2,

3, 5 Ohms. In the wind turbine test the geometry of the model and velocity defined the set of the resistor load for five regimes.

To measure the speed of air flow on the roof of the car was set anemometer Unit 362.(UNI-TUT362), speed sensor was placed so as to minimizethe impact of both on the side of the car and on theside of wind turbine, the control unit was in thecockpit and on the measured values of the establishedspeed of the decision about the recording mode, thevalues of the speed of the device was transmitted andstored in a computer. The measurement of electricalquantities carried out by 2-channel oscilloscope, to

determine the electric power with symmetrical load itis necessary to measure the voltage and the current inone phase, oscilloscope allowed to determine thefrequency of rotation of the wind turbine. The voltagemeasured between the phase and the common point,and the current is measured at a bypass installed between the general point and load, so theoscilloscope there was common ground to a common point.

Determination of electric power produced bydependence for three-phase AC circuits with

consumers, 3 ph phel U I N , Вт, where -

ph I phase current alternator, A, phU - phasegenerator voltage, V, 3 - phase number of generator..

Figure 10 Wind-turbine Ø2000mm in the process of towing.

Figure 11. Torque moment measurement



Definition of aeromechanical power includes thesum of electric power plus losses in the generator andmechanical losses in the belt transfer, or electrical power, divided by the multiplication of the efficiencyof the generator and belt transmission:

.. dr g el wg N N , W, where el N - electric-

power of wind generator, W, %88 g - average

value of the efficiency of generator (when processed

by each load value changed), %96. dr -

efficiency of the belt transmission.

In the test of this series in wind generator wereinstalled 33 inlet blades of foam (fig. 12), and thewheel consisting of 32-reinforced plastic blades, wasalso carried out an experiment with fewer bladesimpeller with 16 blades. Experimental research for

this series was conducted for different blade angles of the impeller with 33 blades (26 ..45 degrees) and for modes with 16 blades on the wheel with the angles of setting 30, 37.5, 42.5 degrees. On the graphs (fig. 13...17) are presented the results of the experimentaldepending aeromechanical power from the load,frequency of rotation, wind speed for some modes.

Figure 12 .Wind-turbine Ø2000 test

Figure 13. Dependence of the power from the load, angle of installation 37.5



Figure 14. Dependence of power from the load, the installation angle of 35 degrees

Figure. 15. Dependence of the power from the load, angle of installation 32.5 degrees



Figure 16. Dependence of the power from the load, angle of installation 32.5 degrees

Figure 17. Dependence of the power of the flow velocity, angle of installation 37.5 degrees

Conclusion

Results of series of design, CFD calculations, tests inwind tunnel and towing of wind power generator,consisting of round wing shroud and axial flowturbine showed applicability of the concepts and principles for generating electric power from air evenon roof of building. The proposed design fulfilled therequirements of safety for avian andlivings as well as absence of influence on TV set andflicker effects.

REFERENCES1. Awano, Seiiti. Axial Flow Wind Air-Turbine NU-

102 with Electric Eddy-Current Brake. うず電流形

電磁ブレーキをそなえた静翼付風力タービン .- Memoirs of National Institute of Polar Research. Ser.

F, Logistics 3, pp. 1-57, 1979; Also: Transactions of JSME, Ser. B, vol. 46, №401, pp. 57-66, 19802. Horlock, J.H. Axial Flow Turbines: Fluid Mechanics and Thermodynamics. Butterworths,London, 1966, 266 pp.3. Kort Nozzle. Wikipedia, Free encyclopaedia. 20114. Walter, J., Girard R. The Eollinne Bolle. An Illustrated History of the Unique French Wind-

turbine, from 1868 to Today. Archiving Industry,Portslade, 16 pp., 2010

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SMALL WIND TURBINE AERODYNAMICS: OLD WINE IN NEW BOTTLE