aerodynamics of small wind turbine a new game on old ground

7/30/2019 AERODYNAMICS OF SMALL WIND TURBINE A NEW GAME ON OLD GROUND

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R.A. Izmaylov, S. Y. Dudnikov, A.A. Lebedev et al.

Fig. 6. Wind tunnel of SPSPU

CIEPLNE MASZYNY PRZEPLYWOWETURBOMACHINERY 2011

Rudolf A. IZMAYLOVProf., Dr. Sci. (Tech), St. Petersburg State Polytechnic University, Russia e-mail:

Sergey Y. DUDNIKOVCand. Sci. (Phys-Math), Optiflame Solutions, e-mail:

Alexander A. LEBEDEVCand. Sci. (Tech), St. Petersburg State Polytechnic University, Russia e-mail:

Evgeny N. KHOROSHEVDirector, Optiflame Solutions, e-mail:

Yuri S. CHUMAKOVProf., Dr. Sci. (Tech), St. Petersburg State Polytechnic University, Russia e-

mail:

Yuri B. MELNIKOVCand. Sci. (Phys-Math), Optiflame Solutions e-mail:

AERODYNAMICS OF SMALL WIND TURBINE:

A NEW GAME ON OLD GROUND

Abstract: A new design of small wind turbine is presented. The proposed

system consists of axial flow turbine, located in aerodynamically profiled ring

shroud, and modern alternating current generator. Results of CFD three-

dimensional modelling of the system operation are presented.

System prototype (diameter 0.5 m) was tested in open air on a moving car and

in wind tunnel of SPSTU. Experiments were carried out at different air

velocities with the measurements of flow using hotwire anemometer and

pressure pick-ups. The results confirm preliminary estimations and open

possibilities to produce small wind turbine up to diameter 10 m.Keywords: small wind turbine, CFD, wind tunnel test.

Our predecessors were Pierre Bollee [4], producing wind turbine for pump

drive, based on shrouded axial flow turbine (Fig. 1-a), and Seiiti Awano [l],

constructing similar turbine for Antarctic polar station (Fig. 1-b). Using Awano designas a prototype we use aerodynamically profiled ring shroud based on Kort Nozzle

(Fig. 1-c) [3], which increases to some extent the level of flow inlet velocity in front of

the guiding vanes. In such a way we get a new construction permitting to overcome

unfavorable features of well known typical wind turbine with propeller blades. Inlet

guide vanes are the means for protection of avian, the shroud is useful as a means

for protection in case of rotor blades
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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R.A. Izmaylov, S. Y. Dudnikov, A.A. Lebedev et al.destruction, all the design excludes flicker effects of TV signals and decreases

radiated noise level.

The inlet air velocity in front of the shroud at the design point was 10 m/s,

ambient condition - standard atmosphere. Hub to tip ratio - 0.5, overall diameter -

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. (See Fig. 2) Airfoil NACA 4415

was chosen for ring shroud, relative thickness 0.1875 Overall length - 160 mm.

Inlet contraction ratio at the guide vanes is 0.942, outlet diffuser ratio 1.176.

Hemisphere is located in front of the turbine hub, outlet portion is conical. AC

generator (direct drive permanent magnet) is located inside the hub. Basic idea of

the aerodynamic design is shown on Fig. 3.

The flow in the designed system (turbine and ring shroud) was calculated with

the aid of commercial CFD. Navier-Stokes equation with appropriate boundary

conditions was numerically solved for different inlet velocities. This has allowed the

proper choice of the form of the ring shroud including optimal contraction/diffuser

ratio. An example of flow distribution (CFD) is presented on Fig. 3. There one can

clearly see some acceleration of the flow at the turbine inlet attained by the ring

shroud.

a) b) c)

Fig. 1. Predecessors: a) Eolienne Bollee [4], Awano NU-102 [1], Kort Nozzle [3]

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

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


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Aerodynamics of Small Wind Turbine

Fig. 4. Simplified wind turbine in inverted Eiffel wind tunnel

After choosing the proper geometrical parameters of the system we have

started experimental investigation of the model. We constructed a simplified wind

tunnel (inverted Eiffel type) to check the ability of the turbine to generate electric

power and calibrate the AC generator with Proni type torque meter. The design was

simplified (plastic blades and cylindrical shroud, removed in Fig. 4).

Fig. 3. Axial flow distribution (CFD)

The next step was carried out on a car. The turbine was installed onthe roof of the car and was tested at different velocities (Fig. 5). Tomeasure the generator characteristics a special portable data acquisitionsystem was designed for the measurements of air velocities with the aidof vane and thermistor anemometers.

Fig. 5. Complete turbine installed on the roof ofa car

H370TH47


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R.A. Izmaylov, S. Y. Dudnikov, A.A. Lebedev et al.Finally, complete aerodynamic tests were carried in aerodynamic

wind tunnel (Fig. 6) of StPSU (courtesy permission of prof. E. Smirnov,Head of Aerodynamic department). This tunnel of Gottingen type hasdiameter of section 2 m, level of turbulence is less than 0.2%, axialfan drive allows to get all the range of necessary air velocities (werestricted the upper limit to 15 m/s).

In this series of experiments, besides electrical generator data, detailed

aerodynamics measurements were carried out with the aid of Prandtl tube (inlet flow

control), vaned and thermistor anemometers, and hot wire anemometer (single

wire), as well as semiconductor pressure pick-ups (Endevco and Honeywell types)(Fig. 7).

The results are presented on figures below (Fig. 8-11). They clearlydemonstrate the influence of the number of the blades on attainable electric power

and the useful function of the ring shroud.

Fig. 7. Complete wind generator test in the SPSPU wind tunnel


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Fig. 4. Simplified wind turbine in inverted Eiffel wind tunnel

Nomenclature for Fig. 8-11:

R- resistance of the electric circuit

T] - turbine efficiency

Aeromechanical power and efficiency dependence on air velocity (shrouded, z32/16, 2D)

air velocity, m/spower, R=10 Q ~M~ power, R= 23 Q -A- power, R= 37 Q -O- r, R= 10 Q -El- r, R= 23 Q A r, R= 37 Q

Fig. 8. Aeromechanical power and r dependence on air velocity (shrouded, z32/16, 2D)


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Fig. 9. Aeromechanical power and ^ dependence on air velocity (z32/16, 2D)

air velocity, m/s

-?-power, R=10 Q power, R= 23 Q -A-power, R= 37 Q -^-^, R= 10 Q -B-^, R= 23 Q A ^, R= 37 Q

echanical power and efficiency dependence on air velocity (shrouded, z32/16, 3D)

Aeromechanical power and efficiency dependence on air velocity (without shroud, z32/16, 2D)

Fig. 10.Aeromechanical power and ^ dependence on air velocity (shrouded, z32/16, 3D)

air velocity, m/s

--power, R=10 Q power, R= 23 Q -A- power, R= 37 Q R= 10 Q ^=h^, R= 23 Q A R= 37 Q


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Fig. 12. Flow field (hot wire anemometer results) around the wind turbine

On Fig 12 results of hotwire anemometer measurements around the wind

turbine are presented (for inlet air velocity 5 m/s). They illustrate acceleration effect

due to shroud at the inlet guide vanes.

ACKNOWLEDGEMENTS

Authors appreciate gratitude to Mr. V.V. Kanin for his kind support of the

project resulting in participation in Skolkovo project, as well as to prof. E.M.

Smirnov for his support during experimental investigation in the wind tunnel of

Aeromechanical power and efficiency dependence on air velocity (without shroud, z32/32, 2D)

air velocity, m/s

power, R=10 Q power, R= 23 Q -k- power, R= 37 Q -O-r, R= 10 Q B r, R= 23 Q A r, R= 37 Q

Fig. 11. Aeromechanical power and r dependence on air velocity (z32/32, 2D)

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SPSU.

REFERENCES

[1 ] Awano, Seiiti.Axial Flow Wind Air-Turbine NU-102 with Electric Eddy- Current

Brake. y

tfy.- Memoirs of National Institute of Polar Research. Ser.

F, Logistics 3, pp. 1-57, 1979; Also: Transactions of JSME, Ser. B, vol. 46,

Na 401, pp. 57-66, 1980 (in Japanese).

2]Horlock J.H.Axial Flow Turbines: Fluid Mechanics and Thermodynamics.

Butterworths, London, 1966, 266 pp.3]Kort Nozzle. Wikipedia, Free encyclopaedia. 2011.

4]Eolienne Bollee. Wikipedia, Free encyclopedia.

aerodynamics of small wind turbine a new game on old ground

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