USRE21382E - Turbine - Google Patents

Description

MachS, 1940. H. R. STUART TURBINE 2 Sheets-Sheet 1 original Filed Jan. 1'9, 1926 77p SPE@ RAT/o (fj I gmnmtoz March 5, 1940- H. R. sTuAT -TURBINE Original Filed Jarl. 19, 1925 2 Sheets-Sheet 2 gnmntoz 1M K 5M @aux Reissued Mar. 5,v 1940 V l 21,382 t UNITED STATES PATENT OFFICE -K :im

" llarve B. Stuart, Slifllltleld, Ollio,- assignor to Elllhl N. Nes, like Finest, Ill.

12' chime (Cl. zas-55) This invention relates to turbines, and more of the so-called American. the Dutch or other particularly to high-speed air turbines. types of windmills.

One of the principal objects of this invention is Fig. 1 illustrates a two-bladed high-speed wind to provide a turbine of such construction and turbine I constructed in accordance with the i design as to operate at a high speed as compared present invention and, as shown, the turbine is g with the velocity of the fluid power stream. mounted directlyupon and carried by the arma- Anotherobject of the present invention is to (ture shaft Il of a small generator I2 which' may provide a high-speed wind turbine or windmill be supported upon a suitable pedestal i3 in the adapted to be mounted directly upon the shaft of wind stream. v l. a small generator or other machine and to drive One preferred construction o! my two-bladed l. the same at high speed. high-speed windturbine is shown'in Figs. 2 and 3. Other objects of the invention will appear from The length of the blade from its hub to its tip is the following description when taken in connec- .considered as being divided into 100 stations, station with the accompanying drawings, in which: tion Il being at the hub and station |00 being at Il Fig. 1 shows a high-speed wind turbine mounted the tip of the blade.v It will be observed that the Il directly upon the shaft ot a small generator; blade of the wind turbine illustrated is warped,

Figs. 2' and 3 are face and edge views respecthe angle of the blade increasing from 1 42' at tively of a' two-bladed wind turbine; station lill to a little less than 40 at Station I2. Figs. 4 and 5 are face and edge views respec- The blade is constructed to have a good airfoil u tively of a single-bladed wind turbine; and section in accordance with the best modern pracn Fig. 6 is a diagram illustrating certain chartice and dependent upon the angle of the blade. acteristics of high-speed wind turbines. This blade has a no-load tip-speed-ratio oi' Il as Turbines or windmills of the type heretofore compared with the no-load tip-speed-ratms of known have as a general rule been of the type approximately 2 and 4 for the American and the which operate at low speeds, that is. at what is Dutch types of windmills, respectively. The tip gg known technically as low tip-speed-ratio, which speed-ratio of a turbine varie of course, with the is the ratio of the speed of the tip of the windmill load or resistance toturning, but for the p or turbine blade to the velocity oi the air stream of comparison the values of tip-speed-mtigg or wind. stated herein are all given for the condition of l'br example, the so-called 'American type of no-load, that is, when the turbineis runningrreen windmill consists generally of a large number of While Figs. 2 and 3 illustrate the prei' substantially sector shaped blades mounted upon form oi' two-bladed turbine. it will be understood a hub. This type of windmill is generally of that good results may be obtained from wind turquite large and heavy construction and revolves billes hVinB blades which depart somewhat from very slowly, having a no-load tip-speed-ratio oi' the blde illustrated 'TheV Preferred i'orm of 35 approximately 2. The so-called Dutch type of blade llllstl'ated ln these gill'es has an angle of windmill, consisting. generally of. 4 wide blades .4 at what is called the reference station, which made up usually of sticks and cloth, is in some reference statfion is station 5. Good results may respects an advance over the American type of obtains? rom blades ovmgh'llgles 3f 'the 40 windmill in that it commonly operates at a nofore e :Vxgamlladgsnol :is 1m 40 load tip-speed-ratio of about v4. However this being t p0 ru n d to h p ub type of blade also hasmany of the disadvantages o course pr po e armonia? with the angie at the reference station. A satisfactory of the American type of blade due to its great formula for dtermimn g the warp at any station. s weight which makes it unresponsive to gusts of N ora bla e constructed in accordance with wind, and further due to its slow operating speed which makes it unsuitable for direct-drive conyflltrion and nly preferred ail-tou section 1s nection with an electric motor or other higli-` speed machine. Both American and Dutch types @Foot-(WQ) cot-mmf) +25.5-1\.949f+ i I of windmills are inherently ineflcient due to their w construction requiring bracing members. pro- .06(N- 75)(i) jecting parts or other features which are not conll ducive to the good utilization of the air forces. where e f is the no-load tip-speed-ratio of the' The present `invention provides a high-speed blade and an is the angle of the blade at a particwind turbine which is free from the disadvantages ula!- station N. It has also been discovered that u stations or 10 and |00 is varied otherwise than in accordance with the warp formula given above, 0 such variation of blade angle being preferably conned to the range vf rom 0 to 12, and the blade may even be made of uniform angle between the stations referred to. It should be understood,

however, that lincreased variationfrom the. pre' l0 ferred vform of blade illustrated results l'to some degree in los's of the desirable characteristics inherent in the preferred form of blade, although blades embodying the modified constructions referred to are in all cases found to be superior to il the prior conventional forms of windmills, such as the American and the Dutch types.

As illustrated the preferred form of blade shown in Figs. 2 and 3 has an angle of about 40 at station l2, but it should be understood that. IU [that portion of the turbine blade between stations l and 50 or 60 may be varied considerably and certain sections may even depart from airfoil shapes as it hasvbeen found in practice that the lowervnumber stations do not exert the same in- 2 0 'fluence on the performance and efilciency of mY wind turbine blade as the higher number sta-V tions. Satisfactory results have been obtained with turbine blades having blade angles near the yhub as low as 4.

n I have discovered that the thickness or cami ber of the airfoil section of the blade has an im. portant bearing on the blade angle which may be utilized to obtain a blade of satisfactory high tipspeed-ratio. By adopting a blade of higher camil ber and a lsuitable contour the blade angle may be increased somewhat, and it hasbeen found that satisfactory results may be secured corresponding to those obtained with the lower camber blades above described, with blades having blade i angles as much as four degrees higher than those of the corresponding lower camber blades.

The principle of the present invention may be embodied to even a higher degree in afsinglebladed high-speed wind turbine. A preferred form of such a single-bladed high-speed turbine is illustrated in Figs.' 4 and 5, the blade illustrated having'a no-load-tip-speed-ratio of substantially Il, which'means that the tip of the blade moves at .a speed fourteen times as fast as the wind u, which actuates the blade. This blade is preferably also of good airfoil section and is warped accordingrto a formula analogous to the warp formula given above. 'It has also been found that the single-bladed turbine may be varied som'eu what in its form and construction, and satis'- factory results have been obtained from Yblades which vary in angles, warp and airfoil sections as described in connection with the two-bladed` turbine. Preferably however the ang-le of the blade in the tip portion is not greater than 9"4 or 10, and the angle of this particular portion of the blade can best be made about 3. From stations 00 or 10 out to station |00 the blade angle is les than 5 in forms shown in Figs. 4 and 5, al-` though this figure may be increased by several degrees and still give very satisfactory operation. 'rae single-blades turbine n provided with a.

f counterweight which may be in the form of al plate such asthat shown at the base of the blade 1. in Figure 5, and is preferably mounted for move- 'ment on its support about an axis transverse to the longitudinal axis of the blade. The ratio of blade length to blade width is preferably, though not necessarily. six to one asV clearly shown in Figsto.

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good results may be obtained from the blade'when' the angle of .the outer part of the blade between l High-speed wind turbines constructed in accordance with the present invention possessv numerous advantages over the prior types of windmills. Of prime importance is the fact that the high-speed wind turbines may be direct- 5 connected to a generator so as to drive the same at high speed. This makes possible thel elimination of gearing and special mounting which has heretofore been necessary to support the gearing and the heavy windmills. My high-speed wind l0 turbine is of light weight as compared with prior windmills, and hence it is cheap, and may be easily mounted on light weight supports. Owing to its lightness and low inertia, a high-speed wind turbine responds to wind gusts better than prior lo forms of windmills and may often be operated by gusts of wind which are of insufficient duration or of such a character that they could not be utilized by prior forms of windmills.. 'I'his ability to respond to gusts of wind is an important advantage at certain times. This will be apparent when it is appreciated that the energy available from the wind varies as the third power of the wind velocity and thatnthe gustsl of wind therefore represent the greater part of the energy 254 available at such times. For example, if a gust of wind should double the wind velocity. then the power of thev wind at the moment of the gust would be eight times the power ,before orafter the gust, andit will be apparent; therefore, that frequent gusts of this order may constitute a large portion of the available wind energy. Further, due'to the type of construction of the high-speed wind turbine, `it has great strength and can stand a much higher speed of revolution :is than the old-fashioned windmills without danger of injury to itself. It can thus utilize high winds which would requirethe conventional American and Dutch or other types of windmills to swing out and perhaps stop? running altogether. I 40 Fig. 6 illustrates iin diagrammatic 'form one advantage of my invention which is the ability of the high-speed wind turbine to obtain great power from the wind when it is direct-cbnnected wig a generator or other machine. In this diagra the tip-speed-ratio (f) is plotted against the\\ direct drive power factor (Cpfz), which represents the power obtainable from direct-connected windmills or turbines operating at /a given speed (R. P. M.) and in a given wind velocity, and whose diameter is adusted to attain the given R. P. M.l As is well understood,the prior types of windmills are essentially slow speed affairs, and high R.'P. M..can be attained only by reducing theY` diameter which in turn reduces the power that c an be taken from 'the wind by the windmill. The curve designated at 1I represents the direct drive power factor for a conventional American type windmill. Such a windmill has a no-load tip-speed-ratio of approximately 2. The mani- 6U -mum power available'from the American type of windmill is obtained when this windmill is loaded up, and hence slowed down to a point where its tip-speed-ratio 'is approximately '1.4, vat which point the power available is4, .6. 1 2 represents a (5.3 similar curve for thev conventional Dutch type of windmill having a no'-1oad tip-speed-ratio of 4.

In this case the maximum power obtainable is 2 at "a tip-speed-ratio of approximately 3. 13

represents the direct drive power factorA curve for 70.

my two-bladed high-speed wind turbine oonstructed substantially .as shown in Figs 2 and 3 and having a' no-load tipspeed-ratio of\approxi mately ll. This blade yields a maximum-power of I4 when the blade is' loaded to have a tip-speed 'lo "aises of approximately 8. The direct drive power factor for a single-'bladed high-speed wind turbine constructed substantially as Vshown in Figs.

4 and 5,.is indicated at 1I. This blade has a n0- load tip-speed-ratio of approximately 14 and yields a maximum power 01.60 when the blade is loaded and' its tip-speed-ratio is approximately 1l. These curves as previously stated correspond to blade designs all operating at the same rotational speed in a given wind speed, curve 'Il corresponding to 'a'windmiil ofsmall diameter, having short blades giving very small power, curve 12 corresponding to a mill of somewhat larger diameter, having longer blades productive oi' large power 'and curve 14 corresponding to a still longer blade productive oi still greater power. It one would attempt to increase the length of blade of the old type o! windmill to obtain more power than is represented by curve 1I the immediate result would be a decrease in speed oi rotation for direct-drive connecon with a work machine, is

also useful when gear-connected with work machines. The advantages pointed out, such as light weight oi turbine, low cost, 'quick response to wind gusts and so iorth are equally advantageous when the high tip-speed turbine is substituted for the prior windmills.

While the forms oi apparatus herein described constitute preferred embodiments o! the invention, it is to be understood that the invention is not limited to these precise forms oi' apparatus, and that changes maybe made in either without departing from the scope of the invention which' is deiined in the a'ppended'claims.

l A wind turbine having a no-load tip-speedratio greater than 5. having a very smallnumber of blades each having a blade angle between stations Il and Ill no greater than l2 degrees.

2. A fluid turbine having a no-load tip-speedratio greater than 5, having a very small number oi blades each having a blade angle between stations 1l vand Ill no greater than 'l degrees.

3. A wind turbine having a no-load tip-speedratio greater than 5, having a very small number oi warped blades whose angle at the reference station is not greater than 12 degrees. f

4. A high-speed wind hirbine ot the. character described having a no-load tip-speed-ratio greater than 5 and having afvery small numberoi ime peller blades each having an angle with the 'plane oi' rotation degrees.

plane of rotation at the tip of the blade of substantially three degrees.

5. A high-speed wind turbine of the character described having a no-load tip-speed-ratio greater than 5 and having a very small number oi' impeller blades each having an angle with the at the tip of the blade between zero and ten degrees.

6. A high-speed wind turbine of the character described having a no-load tip-speed-ratio greater than 5 and having a very small number oi'. blades each having an aeroioil section providing a curved side which faces away i'rom an approaching wind, said wind turbine having an impeller low-angle blade extending substantially continuously from the tip to the hub of the prop eller, the ratio of blade length to blade width being approximately sixto one, the blade angle at the tip of the blade being between 0 and 10 7. A uid power turbine having a very small ,number of blades each having an angle between greater than 7 and havstations 'l0 and Ilili no tillilg ai; operating no-load tip-speedA ratio greater 8. A wind turbine having a single impeller blade having a blade angle between stations 'Il and Ilill no greater than 5 and arranged to operate with a no-load tip-speed ratio of greater than 9. i

9. A two-bladed wind turbine having a no-load tip-speed-ratlo greater than 9, the blades having an vaeroi'oil cross-sectional shape of small blade angles with respect to theplane of revolution, the

angle at the tip of the blade being ls than 4 i degrees and the angle of the blade at station 'Il being less then 7 degrees.

l0. In combination, and a rotor shaft. anda wind turbine mounted on the shaft and adapted to drive thek same at high speed, theturbine having a no-load tipspeed-ratio greater than 5 and having a very small number of blades each having an angle between-'stations cn end 'm no' greater then i2 degrees.

l1. In combination. and a rotor shaft, and the shaft and adapted speed, the turbine having a no-load tip-speedratio greater than 9 and having not more than two blades, each -blade having an aerofoil section providing a curved side which faces away irom an approaching wind and having a blade angle between stations 'Il and- Ill no greater than 7.

12.- High-speed direct-drive means for the rotor oi' a light,l high-speed generator. comprising a wind/turbine having a no-load tlp-speed-ratio greatethan 9 and having a very small number of blades, each blade having an aeroi'oil section a wind turbine mounted on a generator having arotor a a generator having 'a rotor to drive the same at high.

providing a curved side which faces away from u an approaching wind and having a blade angle between stations 1I and Ill no greater than 7.

HARVE Vlt. STUART.

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