Fluid reaction surfaces (i.e. – impellers) – Articulated – resiliently mounted or self-shifting impeller... – Resilient bias or mount
Patent
1990-03-08
1992-03-17
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
Articulated, resiliently mounted or self-shifting impeller...
Resilient bias or mount
416138, 416140, 416163, 416168R, F03D 706
Patent
active
050963813
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a regulating device for maintaining constant the rotary speed in turbines, especially wind-powered turbines.
Swedish Patent Specifications 387,161 and 426,091 disclose the possibility of maintaining constant the speed of rotation in wind-powered turbines from a selected lower wind-force limit up to a selected upper wind-force limit, above which the rotary speed is again reduced, by means of a regulating device automatically operating in dependence upon the wind force.
This prior art speed-regulating device is useful in wind-powered turbines having turbine blades extending substantially radially outwards from the turbine shaft and axially connected to the turbine hub by means of torsion springs, so as to be rotatable about their longitudinal axes in relation to the hub. The turbine blades are therefore rotatably mounted in bearing sleeves extending radially outwards from the hub and connected thereto. The arrangement is such that the wind forces acting on the blade exert, because of the curvature of the blade profile mean chord, a torque, pitch moment, on the blade about the longitudinal axis thereof against the action of the torsion spring. The torsion spring is arranged with a bias between two abutments radially spaced apart in relation to the hub. One of the abutments may be located in the non-adjustable part, the bearing sleeve, and the other at a part connected to the blade. Because of its bias, the torsion spring will exert an elastic torque between the blade and the bearing sleeve, the torque exerted by the wind forces on the turbine blade being counter-balanced by the elastic torque from the biased torsion spring.
In practice, this arrangement has been found to operate excellently, but in some cases has entailed problems which the present invention aims at solving.
One of these problems is that the turbine blades, when the wind impinges obliquely thereon, tend to rotate unequally with respect to each other through excessive angles of displacement, which may give rise to wobbling with a consequential increased load on the turbine. Another problem is that it is not possible to feather the turbine blades by an intentional operation for stopping the turbine, for instance in critical situations. A third problem is that the bias of the respective torsion spring is difficult to readjust once the turbine has been started A fourth problem is the difficulty of complying with the desire to be able to modify the torsion torque of the spring within certain angular ranges to achieve more distinct speed-regulating and shut-off functions.
Finally, the invention has for its object, without any appreciable cost increase, to permit reducing the bending moment on the blade shafts and to improve the geometry and the space for synchronizing devices between the blades at the hub centre.
These objects have now been achieved by designing the inventive regulating device in accordance with the features described in the preferred embodiments.
The invention will now be described in more detail hereinbelow with reference to the accompanying drawings, in which
FIG. 1 is a schematic view of part of a turbine as seen in the direction of the turbine shaft, with certain portions removed to illustrate a regulating and synchronizing device according to the invention operating between the turbine blades via the turbine hub,
FIG. 2 is a longitudinal section taken along the line A--A in FIG. 1,
FIG. 3 is a cross-section taken along the line B--B in FIG. 2,
FIGS. 4 and 5 correspond to FIGS. 2 and 3, but illustrate the regulating device in a partially outwardly angled position and the turbine blade feathered correspondingly,
FIG. 6 is a perspective view of an alternative embodiment in which the synchronizing means generally is rotatable and actively actuable by a push rod and a wire,
FIG. 7 illustrates a modified embodiment in which the torsional load acting on the turbine blades is provided by means of a spring which is common to the blades and which acts directly on the actuator means for the device for co
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Larson James A.
Look Edward K.
Sven Svenning Konsult AB
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