The cambered airfoil section then responds exactly like the symmetrical airfoil section just described, weathervaning in the same manner. Cofiguration IV Like III, but larger, and simpler, without formed coning of whirling disk. The blade flattening action is quantitatively described in the section “Centrifugal Glade Angle Control,” but further qualitative description may be useful. The teetering pivot at the blade root is only a part of a larger free pivoting dynamic system which assures against destructive stresses due to severe weather. All the parts deflect elastically, and every deflection is accompanied by stresses in the materials. Instead of producing bending stresses in the blade and in mill shaft 20, body 25, and mast 22, the blade teeters temporarily on pivot 21. Similar actions, with stress relief, occur whenever airfoil tip 4 is driven forward or rearward, whatever the cause may be. Similar stress-relief actions occur by means of the combined actions of pivots 23 and 24. If centrifugal mass unbalance occurs in the whirling plane of the blade, whatever the cause, the front end of mill shaft 20 will move in a circle lying generally in the whirling plane.
Some lift increase, in this case, occurs on the blade, but it is a small part of the change which would occur without weathervaning, and it is a necessary residual effect. If torque is increased, the reverse occurs; the blade goes to a blade angle which is not as “flat.” The response is that of the desired automatic change of blade angle: At small torque and high RPM, the blade is in “flat pitch,” flat to the whirling disk; at conditions of heavy torque and low RPM, the blade automatically takes the coarse pitch required to avoid stalling angles and to develop strong torque. 1A, it is necessary to distribute the centrifugal masses on the aerodynamic portion of the blade to be certain that the “natural” mass distribution of the blade will not have such a strong “blade flattening” action of its own that it will not nose down when the preload torque is exceeded.
An exception to this trend is a roller/airfoil machine designed to produce strong torque, rather than the most effecient power recovery. Dolor muscular en el muslo izquierdo . Able to operate productively both at lower wind speeds and higher wind speeds than existing equipment. Suitable for use in locations of high wind turbulence, where present equipment cannot operate without unacceptable loss of efficiency and threat of structural damage. Consequently, at the present time the dollar cost of delivering each unit of wind energy tends to be high, even though the wind energy itself costs nothing. This anti-flattening mass has its greatest effect when masses 41 are separated from each other as far as possible.
Table I identifies the types and indicates the field of application and the features of each type. Practical and versatile in a wide range of uses, a turbine, for example, being competitive with the familiar farm/ranch windmill for pumping water, and an application to a sailing ship being commercially competitive on the world’s shipping lanes. 1A through 1E are diagrams illustrating the interaction of aerodynamic and centrifugal moments which govern the aerodynamic angle of attack of the freely weathervaning blade of this invention, on a horizontal axis wind turbine, maintaining essentially constant blade lift during wind gusts, and controllable by changing the positions of centrifugal masses. 1A, standing perpendicular to the plane of airfoil 2, one of which masses may be seen in FIG. FIG. 7 shows sailing ship 8 equipped with the aerodynamic blade of this invention. 12, shows internal parts in the hub region.
Also some time is required for any lift change to develop aerodynamically on the blade.
13), increasing the nose-up centrifugal pitching moments on the blade, increasing blade angle of attack and blade lift, increasing RPM, as desired. FIG. 6 shows the cross section of a ship-propelling roller blade, taken at section 6–6 of FIG. 2) and tip plate 5, as seen in FIG. Their positions outboard of the outer tip of roller 1 sharply reduce this induced drag, making the blade aerodynamically efficient. Also some time is required for any lift change to develop aerodynamically on the blade. Now, we repeat this action with the difference that blade angle β is now free to decrease but is prevented from doing so at the start of the action by a constant nose-up pitching moment, not shown, equal and opposite to the initial nose-down pitching moment on the section. 1) At low values of U/V, a turbulent wake exists downstream from the roller, causing high drag in the manner of any blunt-tailed object.
Tipos De Dolor De Cabeza
This variation of U/V, occurring naturally, accomplishes largely the same effect as the use of taper and twist on the plain airfoil blade, and does so in a simple non-tapered non-twisted structure. In the usual vertical wind velocity gradient caused by the surface of the earth stronger winds act at the top of the swing of the blade, and weaker winds act at the bottom of the swing. 0 degrees, which it takes when the wind is blowing and roller 1 is not spinning. Dolor de espalda y dificultad para respirar . Consequently, large machines, relative to their blade weight, have smaller centrifugal forces, and large roller blades have smaller gyroscopic moments than do small roller blades. This support permits a relatively small diameter roller to be used, since large internal space in the roller is no longer needed for structural support.
By design, within limits, this restoring moment may be made large or small. The blade may be designed to whirl in one direction only, with the roller spinning in one direction only. Outside that range, at higher RPM, the aerodynamic efficiency would reduce, correspondingly reducing high wind runaway whirl speeds to acceptable levels while still generating power. Both the local resultant wind direction and the blade section will have moved through the same angle. From expression (2) it may be seen that for any local cross sectional segment of a wind machine blade having a specific airfoil section, with a specific blade chord C, operating at a specific resultant wind velocity VR, at any given instant (ρ is constant), all of the quantities are constant, so that the aerodynamic pitching moment on the blade section around its aerodynamic center is constant.
This enables the roller/airfoil to operate at a high angle of attack, as compared to convetional airfoils, before aerodynamic stalling occurs. The blade of this invention reduces this aeroelastic risk by its insensitivity to the sources of excitation, and by its roller/airfoil structure which, for blades of any particular blade aspect ratio, substantially increases the bending and torsional stiffnesses, as compared to a purely airfoil type blade.
This increased weight at the blade end of the body requires increased balancing weight at the opposite end of the body. 1A shows how to be certain of this. When balanced in this manner, the action of FIG. To increase the blade angle, when a balanced pair of masses is in quadrants (i) and (iii) of FIG. FIGS. 12 and 13 have illustrated a blade with fixed position blade flattening masses and variable position anti-flattening masses. Causa de dolor de espalda baja . In FIG. 15, details of mill shaft 20, teetering pivot 21, and mounting base 3A including blade hub tube 31 and bearings 32, as shown in FIGS. When the preload torque has not been reached, the airfoil of FIG.
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12 and 13, have been omitted for clarity. All information concerning power beyond the mill shaft (generation of electricity, pumping of water, etc.) has been omitted. The total hinge moment, HMmass, produced by all the elemental masses Δm, as they are distributed in the blade by design, is determined by summation. Seen in greater detail, conductor 49 instantly signals the circuit interruption, current stops flowing, motor 42 stops turning, masses 41 retain their separation and RPM is controlled. Centrifugal Blade Angle Control Pitching moments are exerted on the weathervaning blade by centrifugal masses to balance and oppose the nose-down aerodynamic pitching moments described above. FIGS. 1A through 1E and the descriptions below explain the aerodynamic center of airfoils, the location of a free pivot axis which permits free pitching weathervaning of such airfoils, and the use of mass/centrifugal moments to control the angle of attack of these airfoils. In the present invention, these combined bending moments are eliminated by means of a teetering pivot at the blade root.