Dual rotor wind power assembly (variants)

Abstract

The invention relates to propeller-type horizontal-axis wind turbine assemblies. All of the present assembly variants comprise, mounted on a tower, a wind turbine with two coaxial wind propellers on a rotating platform, a gearbox, systems for controlling the pitch angles of the blades and the position of the platform, and an electric generator. The design of the assemblies additionally includes improvements which make it possible to increase the efficiency with which the energy of the wind is utilized, increase electricity output, reduce service time, simplify manufacture and use, increase reliability and working life, and eliminate infrasound.

Claims

1. A double-rotor wind power plant, comprising: a wind turbine mounted on a tower with two coaxial wind propellers on a rotating platform, a transmission, systems for controlling pitch angles of blades and a position of the platform, an electric generator, wherein a generator rotor with a vertical axis of rotation is situated on a top of the tower, and a stator of this generator is fixed to the tower, and an electric generator rotor axis extends vertically and coincides with an axis of rotation of the platform.

2. A double-rotor wind power plant of claim 1, wherein a drive from the turbine to the generator is a bevel gear.

3. A double-rotor wind power plant, comprising: a wind turbine placed on a tower with two coaxial propellers on a rotating platform, a transmission, a control system for angle installation and position of blades and a platform position, an electric generator, wherein a step-up gear is a double-gear mechanism assembled in a single package, each circuit of which transmits motion and torque from one of turbine rotors independently of movement of another circuit, that a kinematic diagram of the circuit is the planetary gear and a single-step gear.

4. A double-rotor wind power plant, comprising: a wind turbine placed on a tower with two coaxial propellers on a rotating platform, a transmission, a control system for angle installation and position of blades and a platform position, an electric generator, wherein a coaxial three-shaft sprocket gear is installed between a step-up gear and a power generator rotor, that a three-shaft gear kinematic diagram is made according to a following condition
.sub.1=K.Math..sub.2, where .sub.3=const, where .sub.1a change of an angular velocity of an internal input shaft; .sub.2a change of an angular velocity of an external input shaft; Ka constant factor, which depends on a gear kinematic scheme; .sub.3a change in an angular velocity of an output shaft; consta constant.

5. A double-rotor wind power plant, comprising: a wind turbine placed on a tower with two coaxial propellers on a rotating platform, a transmission, a control system for angle installation and position of blades and a platform position, an electric generator, wherein a lengthening spacer is fixed on the external shaft of the turbine, at the end of which the front bearing the inner shaft is installed.

6. A double-rotor wind power plant, comprising: a wind turbine placed on a tower with two coaxial propellers on a rotating platform, a transmission, a control system for angle installation and position of blades and a platform position, an electric generator, wherein a control algorithm of rotation angles of the blades of a first rotor is
.sub.1=f(), i.e., a positioning of the blade angle depends only on a wind speed, and a control algorithm of another rotor is n.sub.gen=const, .sub.2=ar which means that a generator rotation speed is kept constant by changing angles of the other rotor blades, where .sub.1is an installation angle of the first rotor; is the wind speed; n.sub.genis an electric generator rotation speed; .sub.2is another angle of the rotor; aris a variable.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows the theoretical curves of wind energy efficiency of an ideal wind turbine.

(2) FIG. 2 shows decrease of the turbine speed with a decrease of the wind speed.

(3) FIG. 3 shows variation of the speed of a special three-shaft planetary mechanism (the differential).

(4) FIGS. 4 and 5 show the embodiments of double-rotor electric power installations which offers new solutions different from the conventional ones.

(5) FIG. 6 shows the step-up gear circuit.

(6) FIG. 7 shows the blade bearing unit.

(7) FIG. 8 shows the differential movement of units in the present invention.

(8) FIG. 9 shows the diagram of the energy exchange between the main flow and the turbine.

(9) FIG. 10 shows theoretical WEUC value of the ideal wind turbine based on the ejection effect.

(10) FIG. 11 shows kinematic diagram of the test stand.

(11) FIG. 12 and FIG. 13 show the results obtained after the processing of the measurements and related calculations of basic tests.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) Here the authors specify the basic design solutions of the novel double-rotor wind power installation.

(13) 1. The turbine blades comprise the rotating airfoil. The blade shell forming the aerodynamic surface is made of carbon-carbon composite material. The design is similar to an airplane wing: the spar, fibs, sheathing. The authors consider this blade stricture as novel. But the main thing is totally novel method for the calculation and design of the turbine. FIG. 1 shows the theoretical flow diagrams of the wind energy coefficients. Conventional curve is the A. Betz diagram. Maximum utilization of wind energy by Betz diagram is 0.5926, here the air passage cross-section area of the wind turbine to the flow is about 67% of the swept surface area. In the existing wind turbine the air passage cross-section area is 92-94%. About 60% of the air flow passes the turbine blades and the energy of this part of the wind is not utilized with the turbine. The novel wind turbine which is offered here is based on the use of E. Tikhonova's diagram shown in FIG. 1 (see Example 1). E. Tikhonova's diagram (or Tikhonova curve) is based on the assumption that the action of the air flow on the turbine leads to the effect of air ejection, for air which passes through the turbine drive, this effect is caused by air streams flowing around the turbine disk. As a result, the air pressure downstream of the turbine is reduced and the turbine output power increases.

(14) The share of the passage cross-sectional area of 0.55 is accepted. Based on the value of a passage cross-sectional area the optimum number of blades their aerodynamic profile and geometry can be calculated.

(15) Using this wind turbines design method the authors built model air turbines and studied their characteristics. Test results confirmed the high efficiency of these turbines, (See Example 2).

(16) 2. Structural diagram in FIG. 7 shows the blade bearing unit.

(17) The shank end of the blade 1 is mounted in the sleeve 2 of the propeller hub 3. Inside the sleeve two sliding bearing are placed consisting of ceramic sleeves 4 and the friction surface on the shank end of the blade.

(18) In the rotary sliding bearing of the wind turbine blade 5 solid lubricant is used which is based on metal dichalcogenides in combination with a ceramic sleeve. In conventional designs greases or liquid lubricants are used. Both require periodic changing which complicates maintenance and increases maintenance costs. There are also the problems with leaking lubricant. The use of sliding bearings with solid lubricant eliminates a lot of problems in the operation: there is no need to supply lubrication system for liquid oils or greases, no periodic maintenance, no frequent replacement of lubricants.

(19) 3. Electric power generator is mounted in the tower but not on a turntable, as m the conventional wind turbines, the variant of the generator mounting is shown in FIG. 4.

(20) The power generator is attached to the tower structure, its rotor axis coincides with the axis of rotation of the turntable support bearing. Power cables running from the generator are laid out vertically on the inner surface of the tower. The reliability of the cables is ensured whereas the cables are not twisted when the platform is rotated to any angle.

(21) 4. The rotor electric drive (see FIG. 4) is provided from the step-up gear through a bevel gear, the rotor axis coincides with the turntable bearing axis. The bevel gear casing is fixed to the turntable they both rotate when wind vector is changing. An electric clutch is installed between the output shaft of the bevel gear and the electric generator shaft to compensate some shaft misalignment. The bevel gear input shaft is connected to the a step-up gear with a transmission shaft.

(22) 5. The step-up gear is a dual gear mechanism. Its both circuits function independently. The torque of the second rotor of the turbine is applied to the first circuit, the torque from the first rotor is applied to the second circuit.

(23) The transmission is achieved by coaxial shafts up to the entrance of the three-shaft gearbox. Each circuit consists of a planetary mechanism with the inhibited crown gear wheel satellite and two sprocket wheels, with fixed axes. His structure has never been found or used before in the construction of wind power plants.

(24) 6. In this novel power installation there is a device which provides the most important function of the wind turbines. This three-shaft gear (see Pos. 16 in FIG. 4). It is designed to maintain a constant speed of the output shaft when changing the speed of two coaxial input shafts. The gearbox is a sprocket gear mechanism. One embodiment of this mechanism shown in FIG. 8 (the 3-shaft differential gear kinematics).

(25) This planetary gear mechanism comprises two drives 5 and 7. In the cage 5 the intermediate crown gear is secured. The driver 7 is rigidly connected to the inner input shaft 1 and the wheel 7 having the external crown gear 10. Satellites 8 are placed on the planetary driver 7. Between satellites 3 and 8 the intermediate gear rim 10 is mounted with inner and external sprocket teeth. Gear 6 with a fixed axis is used to change the direction of driver 5 rotation with respect to the driver 7. The external input shaft 2 is coaxial with the shaft 1 it has a crown 3 with internal toothing. The output central sprocket wheel 9 is engaged with satellites 8.

(26) In fact, this mechanism is a differential.

(27) The movement of a conventional differential links can be expressed mathematically as:
.sub.3=A.sub.1+B.sub.2,1)

(28) where

(29) A and Bconstant coefficients depending on the mechanism's kinematic scheme;

(30) .sub.1angular rotation speed of the input shaft;

(31) .sub.2angular rotation speed of the other input shaft:

(32) .sub.3angular rotation speed of the output shaft;

(33) If the speed of one of the mechanism links, such as .sub.2 increases at a constant speed, than at .sub.3 remaining constant the .sub.1 rotation speed decreases. When the .sub.2 goes down the .sub.1 speed increases. We assume that this differential is positive.

(34) If .sub.3 speed remains constant, than changing either .sub.3 or .sub.2 rotation speed, the differential movement expression shall be expressed as:
.sub.1+K.sub.2=0,1)

(35) where

(36) Kthe constant coefficient which depends on the kinematic scheme of the mechanism;

(37) .sub.1 and .sub.2variation of angular rotation speed;

(38) In the proposed novel wind power installation the differential movement of units is totally different (see FIG. 8.):
.sub.3=A.sub.1B.sub.2,a)

(39) or when .sub.332 0
.sub.1=K.sub.2b)

(40) If the speed of one shaft increases, it increases the speed of the other shaft. If the speed of the shaft is reduced, the speed of the other shaft is also reduced. This is a negative differentiation.

(41) The scheme of the proposed mechanism and the differentiation method are novel. No analogs are known. With such a mechanism one of their main tasks in wind power is achievedto maintain constant rotation speed of the electric generator with the decreasing wind speed. No additional devices such as shift boxes, electronic frequency inverters shall be required. The sine form of electric current is preserved without frequency noise.

(42) 7. To eliminate the occurrence of dangerous infrasound frequencies in the range of 0-12 Hz the number of blades in each rotor shall be selected on the condition that the number of the first rotor blades is z, and the number of the other rotor blades is (z+1).

(43) 8. An external rotor shaft 10 (see FIG. 5) is mounted on two ball bearings 11 and 12 that are placed in the rotary engine mounting platform 2. The inner shaft 9 is also mounted on two hearings 6 and 12a. The inner shaft protrudes to 2.5-3 m from the end of sleeve 3 of the external rotor. Console extension of the inner shaft may reach significant values when the mass of the front hub with blades is 6-7 ton. In order to improve the strength characteristics of the inner shaft the external shaft is lengthened artificially by placing a cylindrical spacer 7, which is attached to the flange of the second hub with bolts. At the end of the spacers the rotary bearing 6 is fixed, With its inside diameter it is coincided and mounted on the sleeve 4. Bearing 6 becomes the support of the inner front shaft. Inner shaft console length is therefore reduced to to 0.5 m instead of 3 m. The inner shaft 9 becomes more rigid and durable with its spacer 7.

(44) 9. The proposed double-rotor wind power installation each rotor is independent of the other, i.e, each one can rotate independently. For optimal use of the unique properties of negative differential a special control system has been developed for blades angles installation using only 2 knobs. To prevent speed pulsations and rotation speed swing have different blade rotor control rules are provided for the controllers. One knob adjusts the angle of the rotor blades in their direct dependence on the wind speed, as shown in:
.sub.1=f(),1)

(45) where

(46) .sub.1angle of the blades of one rotor;

(47) wind speed;

(48) The feedback signal from the encoder of the rotation angle sensor which measures the current position of the blade is fed to the wind speed measurement system.

(49) The controller sets the other rotor angle .sub.2 to a value sufficient to stabilize the electric generator rotation speed, keeping it at constant level:
.sub.2=f(n.sub.2), at n.sub.r=const,1)

(50) where

(51) .sub.2angle of the other rotor blades;

(52) n.sub.rrotation speed (rpm) of the electric generator;

(53) n.sub.2other rotor speed;

(54) constconstant

Example 1

(55) We propose a theory for calculating the WEUC (wind energy utilization factor) taking into account the ejection of turbine flow streams of the main air flow. FIG. 9 shows the aerodynamic configuration of the considered option.

(56) We introduce an assumption that the pressure wave propagation velocity is close to the velocity of air flow, the diffusion and mass transfer processes. This assumption is quite justified in the weather conditions of the Earth's atmosphere.

(57) The air flow runs over the turbine disk. Part of this flow with the mass m.sub.1 and initial cross-sectional area S.sub.0 fells on the disc and the flow velocity V.sub.0 is slowing around the disc to V.sub.1. The main air flow passes the active working sections of the disc with a velocity V.sub.0. Turbine flow having passed through the disk is ejected into the main air stream. The turbine flow V.sub.1 and V.sub.3 of the mixed flow rate is less than the speed V.sub.0 of the main stream.

(58) Due to the speed difference, the velocity vector of the sum of two passing by streams shall be directed towards the flow with lower speed. The main flow will exponentially transmit us kinetic energy to the turbine as long as the turbine flow rate becomes equal to V.sub.0. Therefore it is better to set the limit:
V.sub.4=KV.sub.00.97V.sub.0

(59) This process causes the vacuum on the back side of the turbine disk P1*. We assume that the efficiency of the ejector mixing jets is 1.

(60) FIG. 9 shows the diagram of the energy exchange between the main flow and the turbine.

(61) flow number in the cross section 4 is;
mV.sub.4=S.sub.1V.sub.4.sup.2

(62) flow number in the cross section of 1 is:
m.sub.1V.sub.1=S.sub.1V.sub.1.sup.2

(63) The difference in the number of movements, shall be, respectively:
F.sub.4-1=S.sub.1(V.sub.4.sup.2V.sub.1.sup.2)

(64) The difference of the flows between the sections 0 and S.sub.1 is:
F.sub.0-3=m.sub.3(V.sub.0V.sub.1)=S.sub.1V.sub.1(V.sub.0V.sub.3)

(65) The total force acting on the turbine disk is:
F.sub.=F.sub.4-1+F.sub.0-1=S.sub.1(V.sub.4.sup.2V.sub.1.sup.2)+S.sub.1V.sub.1(V.sub.0V.sub.1)

(66) And the corresponding energy, working on the disc is:
W.sub.1=F.sub.*V.sub.1

(67) As a result, the formula for determining the energy efficiency coefficient of the wind is as follows:

(68) $\begin{array}{cc}=\frac{W_T}{W}=2\frac{V_1}{V_0}\left(K^2-\frac{V_1^2}{V_0^2}\right)+2\frac{V_1^2}{V_0^2}\left(1-\frac{V_1}{V_0}\right)& \left(11\right)\end{array}$

(69) Exploring the function to the maximum we shall obtain the maximum WEUC:
0.999.a)

(70) The curve of

(71) $\frac{W_T}{W}$
changes shown in FIG. 10 (theoretical WEUC value of the ideal wind turbine based on the ejection effect).

(72) Whereas the

(73) $\frac{V_1}{V_0}=\frac{S_0}{S_1},$
then the optimum area of the live cross-section of the turbine disc should be in the range of 0.5-0.75 of the total disk area.

Example 2

(74) The test results of the experimental wind power installation with double-rotor wind turbine.

1. The Purpose of the Test

(75) 1.1 Determination of the Power Characteristics of the Wind Turbine.

(76) 1.2 Refinement of Methods of Calculation of Large Wind Turbines.

2. Test Object

(77) 2.1 Experimental Wind Turbine nC-B-5 M.

(78) Geometric and aerodynamic characteristics: Turbine scheme: double-rotor, coaxial, with the opposite rotation of the rotors; Rotor diameter5 m, Number of blades per rotor5 pcs. Blade aerodynamic profileGA airfoil blades (W)-2 (NASA terminology); Blade materialmultilayer aviation plywood; Blade shaperectangular, with constant chord; Chord length0.12 m; Installation of the attack angle mechanismrotation of die blade by hand. Fixing the blades;

(79) 2.2 Kinematic Diagram of the Test Stand is Shown in FIG. 11.

(80) Torque from the rotors of the wind turbine system 1 through V-belt and gears 2, 6 rotates the shaft of the electric generator 5. The generator is mounted on ball bearings and is rotatable about the axis of its rotor. The torque on the stator of the generator is applied through the balancing lever to the scale 3. Damping of the system oscillations is effected with the hydraulic damper 4. Power calculation is made using the torque and the rotation speed of the generator rotor, the calculation method is described in InS-W-16/1. In addition, the power is controlled with dropping resistors 7.

3. Test Results

(81) Tests were conducted in May and June 2008, The unit was installed on the flat roof of a 5-story building. Shading of the turbine for wind vector was not used.

(82) Electrical connections were made in accordance with the procedure InS-W-16/1, Measurements were carried out at a steady wind conditions. The following measurements were made: the generator rotation speed, the load on the balancer lever, wind speed, temperature and barometric pressure, the date and time of measurement. All parameters were recorded in the operating log.

(83) 3.1 The measurements were made according to the procedure of procedure InS-W-16/1. The utilization of wind energy in the area swept with the wind turbine was calculated with correction for air density.

(84) $=\frac{W_{\mathrm{mea}}.Math.1,23}{W.Math.{}_{\mathrm{fact}}}$
Where W.sub.meameasured wind turbine power, Wmaximum power of the wind, within the swept area; .sub.factmeasured air density at the time of power measurements.

(85) The results obtained after the processing of the measurements and related calculations of basic tests are shown in the graphs, FIG. 12 and FIG. 13.

(86) FIG. 12 double rotor wind turbine power vs the wind speed:

(87) The line of actual power measurements

(88) $=\frac{W_{\mathrm{mea}}.Math.1,23}{W.Math.{}_{\mathrm{fact}}}$

(89) Calculated power values curve

(90) Angular rotor speed of the wind turbine

(91) Wind energy utilization coefficient

(92) FIG. 13 Dependence of wind energy utilization coefficient

(93) $=\frac{W_{\mathrm{mea}}.Math.1,23}{W.Math.{}_{\mathrm{fact}}}$
on the Re number.

CONCLUSIONS

(94) Received power values obtained during the test of the experimental double-rotor turbine with counter-rotating rotors demonstrate sufficient coincidence with the calculated power values; according to the test results, the dependence of wind energy utilization coefficient in the form of

(95) $=\frac{W_{\mathrm{mea}}}{W}.Math.\frac{1,23}{{}_{\mathrm{fact}}}$ on the Re number (FIG. 2) was established. With an increasing Re number the wind energy utilization coefficient is increasing. The test of the experimental wind turbine MS-W-5 it showed its high efficiency; It is advisable to develop a number of wind turbines on the basis of double-rotor kinematic schemes. The use of a differential mechanism with a variable transmission ratio is recommended as a step-up gear; Test results are recommend for use for the improvement of the calculation method for wind turbines.

(96) The Example 2 is based on the test results of the experimental of the wind power plant with double-rotor wind turbines obtained by the authors.