BACKGROUND OF THE INVENTION The following U. S. Patents are believed to represent the current state of the art: 1,906,180; 3,953,148; 4,710,099,4,958,986; 4,968,216; 4,984,630; 5,221,181; 5,277,549; 5,362,203; 5,486,091 and 6,042,335.

Reference is also made to co-pending U. S. Patent Application 60/227,334, filed August 23,2000, one of the inventors of which is one of the inventors of the present application.

SUMMARY OF THE INVENTION The present invention seeks to provide an improved radial centrifugal turbine.

There is thus provided in accordance with a preferred embodiment of the present invention a turbine including a central fluid inlet pathway arranged about an axis, a fluid director, which includes a plurality of blades, for directing fluid received along the central fluid inlet pathway to have a component of motion which is radially outward from the axis and a rotor including a plurality of blades, which are driven by the fluid having a radially outward component of motion. The rotor is driven in rotary motion about the axis by the fluid.

There is also provided in accordance with a preferred embodiment of the present a turbine including a fluid inlet pathway and a rotor including a plurality of blades, which are impinged upon by the fluid. The rotor includes a pair of side elements each centered about a common axis of rotation and each of the plurality of blades is secured to both of the side elements There is further provided in accordance with a preferred embodiment of the present invention a turbine including a central fluid inlet pathway arranged about an axis, a fluid director for directing fluid received along the central fluid inlet pathway to

have a component of motion, which is radially outward from the axis, a rotor including a plurality of blades, which are impinged upon by the fluid having a radially outward component of motion. The rotor is arranged to be driven in rotary motion about the axis by the fluid, which exits from the rotor and a controller which governs the operation of the turbine in a manner that seeks to minimize the difference between velocity of the fluid exiting from the rotor and the velocity of the rotor.

There is also provided in accordance with yet another preferred embodiment of the present invention a turbine including a pair of side elements both arranged for rotation about an axis of rotation and extending from a radially inward central location to a radially outward location, a fluid inlet pathway providing a flow of moving fluid to the central location and a plurality of blades secured to the pair of side elements and are arranged to be driven by the flow of moving fluid. The blades are arranged such that at least a radially outward portion thereof extends generally tangentially to a radius extending from the axis of rotation to the outward portion.

Further in accordance with a preferred embodiment of the present invention the fluid director for directing the fluid has a component of motion, which is tangential.

Still further in accordance with a preferred embodiment of the present invention the rotor includes a pair of side elements each centered about a common axis of rotation, the plurality of blades each being secured to both of the side elements.

Additionally in accordance with a preferred embodiment of the present invention the plurality of blades are bowed inwardly to better withstanding centrifugal forces applied thereto as the result of rotation of the rotor.

Further in accordance with a preferred embodiment of the present invention the plurality of blades are arranged such that at least a radially outward portion thereof extends generally tangentially to a radius extending from the axis to the outward portion.

Preferably, the rotor includes a pair of side elements each centered about a common axis of rotation, the plurality of blades each being secured to both of the side elements.

Additionally in accordance with a preferred embodiment of the present invention the plurality of blades are bowed inwardly to better withstand the centrifugal

Forces applied thereto as the result of rotation of the rotor.

Further in accordance with a preferred embodiment of the present invention the plurality of blades are arranged such that at least a radially outward portion thereof extends generally tangentially to a radius extending from the axis to the outward portion.

Further in accordance with a preferred embodiment of the present invention the turbine also includes a fluid director upstream of the rotor for directing the fluid to have a component of motion which is tangential.

Still further in accordance with a preferred embodiment of the present invention the plurality of blades are curved so as to be aligned increasingly tangentially as they extend radially outwardly from the axis.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which : Fig. 1 is a simplified partially exploded view, partially block diagram illustration of a radial centrifugal turbine constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 2 is a partially cut-away pictorial illustration of a portion of the turbine of Fig. 1; Fig. 3 is a sectional illustration of the turbine of Fig. 1, taken along the lines III-III in Fig. 1; and Figs. 4A and 4B are sectional illustrations of part of a rotor of the turbine of Figs. 1-3, taken along the lines IVA-IVA and IVB-IVB, respectively, in Fig. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Fig. 1, which is a simplified exploded view illustration of a radial centrifugal turbine constructed and operative in accordance with a preferred embodiment of the present invention and to Fig. 3, which is a sectional illustration of the turbine of Fig. 1, taken along the lines III-III in Fig. 1.

As seen in Figs. 1 and 3, the turbine preferably comprises an axial fluid

inlet element 10 defining an axial fluid inlet pathway centered about a longitudinal axis 12. Fixedly attached to element 10 is a stator 14 which defines an axial fluid inlet pathway 16 arranged along longitudinal axis 12 which leads into a multiplicity of circumferentially distributed inclined radial fluid outlet pathways 18, which lie generally in a plane perpendicular to longitudinal axis 12.

A rotor 20 is mounted onto a shaft 22 for rotation about longitudinal axis 12 at a location radially outward of fluid outlet pathways 18. As seen in Fig. 1, the direction of rotation of rotor 20, as indicated by arrows 24, is the same as the tangential component of the fluid passing out of pathways 18, as indicated by arrows 26.

A housing element 30 is disposed about rotor 20 and is fixed onto fluid inlet element 10. Additional housing elements 32 and 34 are fixed to housing element 30, so as to define a sealed enclosure whose inlet is axial, as defined by inlet element 10 and whose outlet is preferably radial and tangential, as defined by an outlet portion 36 of housing element 30.

In accordance with a preferred embodiment of the present invention, the rotational velocity of the rotor 20 is preferably measured in a conventional manner by a rotational velocity sensor 37 associated with shaft 22. An automatic rotation velocity controller 38 receives an output from sensor 37 and controls the input energy of the fluid input to pathway 16, via a fluid input controller 39. It is a particular feature of a preferred embodiment of the present invention that the rotation velocity of the rotor 20, indicated by arrows 24 is generally equal and opposite to the exhaust velocity of fluid leaving the blades of the rotor 20 (as indicated by arrows 27), thereby resulting in the absolute velocity of the fluid leaving the rotor 20 to be nearly zero. This condition substantially reduces fluid exit losses in the turbine and maximizes the extraction of energy from the inlet fluid. A substantial reduction in turbine noise is also realized.

Reference is now made to Fig. 2, which is a partially cut-away pictorial illustration of a portion of the turbine of Fig. 1, to Fig. 3, which is a sectional illustration of the turbine of Fig. 1, taken along the lines III-III in Fig. 1 and to Figs. 4A and 4B, which are sectional illustrations of part of a rotor of the turbine of Figs. 1-3, taken along the lines IVA-IVA and IVB-IVB, respectively, in Fig. 1.

As seen in Fig. 2, an axial flow of fluid (as indicated by arrows 39) entering stator 14 along axial pathway 16 undergoes two changes of direction. The axial

Mow 39 encounters a generally conical deflector surface 40, which converts the axial flow 39 to a generally circumferential radial flow. This generally circumferential radial flow impinges on a multiplicity of inclined vanes 42, which define pathways 18 (Fig. 1), which provide expansion and a change of direction from a generally pure radial flow to a plurality of separate flows having both radial and tangential components. These flows are indicated by arrows 44.

As also seen in Fig. 2, the fluid flows out of pathways 18 in the stator 14, indicated by arrows 44, drive rotor 20 in rotary motion about axis 12 in a tangential direction, indicated by arrows 24, which is the same direction as the tangential components of flows 44.

Rotor 20 is preferably formed with first and second side walls 50 and 52, to which are fixed therebetween a plurality of blades 54. Blades 54 are highly inclined with respect to the radial direction, the inclination being in a direction opposite to the direction of inclination of vanes 42 of the stator 14. Preferably blades 54 are sealed at their sides to side walls 50 and 52 to prevent leakage of fluid between the blades and the side walls.

Blades 54, as seen particularly in Figs. 4A and 4B are preferably constructed to have variable thickness as they extend radially outward with respect to axis 12. It is a particular feature of the present invention that blades 54 are curved so as to be aligned increasingly tangentially as they extend radially outwardly from axis 12.

Preferably, at their extreme outward edge, blades 54 are nearly tangential, preferably within about 4 degrees.

It is also a particular feature of the present invention that, as seen particularly in Fig. 4A, the blades 54 are bowed radially inwardly, so as to better withstand centrifugal forces applied thereto as the result of rotation thereof about axis 12.

It is appreciated that the variable thickness of the blades 54 is determined mathematically according to the thermodynamical properties of the flow, as is known in the art. It is further appreciated that although the cross-sectional shape of the blades 54, shown in Fig. 4A, is convex, other cross-sectional forms for the blades 54 may be used, such as blades with a planar surface.

It will be appreciated by persons skilled in the art that the present

invention is not limited by what has been particularly shown and described hereinabove.

Rather the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove as well as variations and modifications which would occur to persons skilled in the art upon reading the specification and which are not in the prior art.