Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Reexamination Certificate
2002-09-09
2003-10-14
Nguyen, Ninh H. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
C416S18600A, C416S22300B, C416S243000
Reexamination Certificate
active
06632071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field
This invention relates to blower and pump impellers having overlapping curved blades forming long, narrow, constant width flow channels. More particularly it pertains to a blower, which provides high flow characteristics while minimizing flow resistance. It is an impeller employing a plurality of discs having equally spaced spirally curved radial blades therebetween forming constant width and constant height flow channels, which produce a higher vacuum and pressure than previous designs. It is particularly suited for use in mineshaft and tunnel ventilation. It is also very useful where space is limited and a high volume of air is required through a small duct.
2. State of the Art
A number of blowers and impellers are known. Pauly, U.S. Pat. No. 5,741,123, hereinafter referred to as Pauly '123, describes an impeller having constant cross section area along the length of the flow channels. The constant cross section is accomplished by reducing channel height in co-operation with an increasing blade spacing thereby providing a constant cross section area. Such a configuration causes the fluid being moved to flow with a twisting motion and is not optimum for keeping Reynolds' number effects at minimum. That is, channel shape is a factor in generating turbulent flow. The present invention maintains a constant channel cross sectional shape, width, and height permitting the fluid to flow smoothly and laminar throughout the length of the flow channels. Conversely, Pauly '123, FIG. 6, shows a multi-blade overlapping configuration of impeller. This configuration is described at Column 5 lines 16-32. Pauly '123 makes no teaching about the blade shape or its span from the inlet end to the outlet end.
Eiichi Sugiura, U.S. Pat. No. 4,666,373, describes an overlapping blade impeller having constant blade height. Sugiura uses a blade of circular form and clearly teaches that the blades spacing narrows as it approaches the rim of the impeller. The present invention uses spiral blades and constant width flow channels. The Sugiura blades are segments of circles. Circular blades with any serious overlap will always converge at the impeller rim. Furthermore, Sugiura fails to teach how to determine adequate, proper, or optimum blade shape radii, or what is optimum spacing or overlap, nor how to select the circle about which the radii are arrayed. Because of the lack of design parameter teaching, it is impossible to conclude any minimum or maximum blade length and angular span as part of the Sugiura disclosure.
D. I. Doyle, U.S. Pat. No. 2,767,906, describes an overlapping blade impeller. Doyle also teaches that the spacing should narrow as the blade approaches the rim of the impeller. Moreover, Doyle (Column 5, lines 7-15) specifically states that the blades should not be parallel, nor should they diverge. The Doyle blades are segments of a spiral generated by an involute of a circle function not centered on the central axis of the impeller. Doyle specifically rejects involute blades developed around the impeller center as too long to be effective.
Pauly '123 and Sugiura do not address minimizing Reynolds' numbers and have nozzles pointing somewhat radially away from the tangent. Doyle minimizes the problem by having long sweeping flow channels (and blades), which inherently exit as near to tangential as practical. Doyle, Pauly '123
FIG. 6
, and others in their drawings show flow channels spanning an arc of well over 90 degrees. None teach about an optimum length or how to conclude that the lengths shown are near optimal.
There thus remains a need for an impeller invention, which optimizes both the channel length and tangential nozzle angle by teaching the optimum span for flow channels. The present invention with a blade having unusual curvature and spanning approximately 60 degrees with flow channels starting out as Archimedes spirals and then near the periphery the channels turn inward to exit more tangentially as it would if a longer channel was utilized provides such an invention.
OBJECTS OF THE INVENTION
It is an object of the present invention to devise a blower impeller having an optimal compromise within the various conflicting parameters affecting impeller performance.
It is another object of the present invention to devise a blower impeller that runs quietly.
It is another object of the present invention to devise a blower impeller blade lofting process that does not rely on generating tables using complex mathematical formula.
It is another object of the present invention to devise a blower impeller that may be manufactured without expensive specialized tooling or machinery.
It is another object of the present invention to devise a blower impeller that can be substituted for the original equipment impeller thereby improving the efficiency of installed blowers.
Definition of Terms
Unless distinguished by the context of usage, the following general definitions apply to these terms:
FLUID: includes gasses and liquids
AIR: unless determined otherwise by context, should be interpreted as a “fluid”
BLOWER: general usage of “blower” is machinery for moving gasses, but in this context it should be interpreted as including pumps
PUMP: general usage of “pump” in centrifugal machinery is for moving liquids, but here it should be interpreted as also pumping gasses.
LOFTING: a graphical process for developing shapes of products such as blades for blowers and pumps from which templates and other production tools are produced. Generally lofting is done at 1 to 1, full scale, but may be done on expanded or reduced scale.
SCROLL CASE: The collection chamber for gathering the outflow from an impeller and directing it into ducting or the like. Most scroll cases are formed in one of several known spiral shapes.
MOTOR: Any source of rotating power including, but not limited to electric, hydraulic, pneumatic motors, turbines, engines, and transmission systems between the power source and the impeller.
ARCHIMEDES SPIRAL, or SPIRAL OF ARCHIMEDES: A spiral that increases radius proportional to the angle turned. The formula for an Archimedes Spiral is R=K*(theta) in polar coordinates. Where R is the distance of the point from the center of generation. In this case, the center of the impeller disk, and theta is the angle turned from the polar origin (r=0, theta=0). It is therefore intended that the term “Archimedes Spiral” refers to blade shapes defined by the Archimedes Spiral formula, or other equivalent spiral formulae, where the spiral shape is defined by a plurality of curved or straight line segments approximated by the formulae.
SUMMARY OF THE INVENTION
The present invention comprises two parts:
First, it is directed to a blower impeller for installation within an operating housing. In most uses, the operating housing will have a lateral central housing air intake in communication with an interior circulation chamber containing the impeller, a peripheral air collection chamber, and a tangential exhaust. A drive shaft is journal mounted to the housing to extend within the circulation chamber and attached to the center of the impeller opposite the air intake.
FIG. 6
illustrates the impeller installed in a common “snail” housing.
Second, it is directed to a method of lofting a specialized blade shape for production of impeller blades for the blower.
The present invention provides low turbulence flows with low Reynolds' numbers. The enemies of efficient impeller design are turbulences associated with high Reynolds' numbers, turbulences associate with exit streams crossing the flow in the collector scroll, surface drag (boundary effects) along the walls of the fluid flow channels, cavitation, entrance geometry at the inlet of the impeller flow channels, and inadequate inlet area in the impeller inlet eye. Reynolds' number effects are controlled primarily by the narrowest dimensions of rectangular flow channels, the fluid velocity through the channels, and the viscosity of the fluid. Decreasing the spa
Nguyen Ninh H.
Theodore Marcus G.
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