Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Patent
1995-05-03
1997-04-15
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
416188, F04D 2924, F04D 2930
Patent
active
056203063
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an impeller and especially to a pressure boost impeller suitable for compressing fluids such as gases and liquids.
BACKGROUND ART
Known impellers or fans can include an arrangement of airfoils. By airfoils is meant a foil or blade which is substantially a version of a wing. A typical wing or foil has a shape which creates a greater distance over one side, which is usually the topside, than the opposite side.
This configuration of a typical foil or wing when driven forward with its thickest end foremost splits the ambient fluid, be it gases or liquids to cause a portion to pass over the top and a portion to pass underneath. The greater distance the fluid travels over the side with the greatest curve, which is usually the top, forces that fluid to a tendency toward being attenuated.
This substantial attenuation causes a lowering of pressure. The lowered pressure attracts adjacent fluid and the effect is to create an upward suction. If the wing or foil cannot rise, the fluid travels down to meet it and usually passes mostly behind the trailing edge.
In this type of foil or wing it can be seen that there is a direct relationship between each side of the wing or foil.
If, because of a too coarse pitch (nose up) the pressure underneath becomes too high and the pressure above becomes too low, the foil or wing will stall. In this case the high pressure fluid from the underside creeps around the Trailing edge and forward along the topside and causes detachment of the topside fluid flow. Upwards suction is lost or greatly diminished and therefore loss of lift occurs.
High pressure air also travels around the foil or wing tips and creates vortices, which detracts from lift and creates a drag on the foil near its tips.
A typical conventional fan is almost always a circular arrangement of these foils or small wings and is subject to the same factors which cause a loss of efficiency.
In a typical conventional radial flow fan, the foils or miniature wings diverge from each other from a medial to a lateral area. In this situation, each foil or wing relies on the lower pressure air travelling over the low pressure side of the foil or wing to substantially reach the trailing edged to rejoin the higher pressure air being flung radially by the high pressure side of the foil. So in this type of fan is subject to having its blades or foils stall if a back pressure or head pressure is generated. If this type of fan is driven to too high tip speed each foil stalls and in certain circumstances fluid can actually travel back between each set of foils along the low or suction side of the foils. In effect there is created a counter current of fluid between any two foils.
DISCLOSURE OF THE INVENTION
It is an object of the invention to provide an impeller which may substantially overcome the abovementioned disadvantages or provide the public with a useful or commercial choice.
In one form, the invention resides in an impeller having a front intake area and a rear discharge area, a hub containing the rotational axis of the impeller, a plurality of blades extending about the hub, at least some of the blades being in an overlapping relationship to define a passageway between adjacent overlapping blades, the passageway having an inlet communicating with the front intake area, and an outlet communicating with the rear discharge-area, the inlet having an area larger than the area of the outlet to define a step down in volume of fluid passing through the passageway.
The blades extending about the hub may have a leading edge which can define part of the inlet, a trailing edge which can define part of the outlet, an outwardly extending tip, and a root which can be attached to the hub.
The blades can be attached to the hub at a distance spaced from the rotational axis to define a land portion between the blades and the rotational axis. This land portion can cover between 10% to 50% of the area of the hub, and typically comprises at least 30%. The root of the blades can be attached to the hub adjac
REFERENCES:
patent: 2284141 (1942-05-01), Funk
patent: 2484554 (1949-10-01), Concordia et al.
patent: 4647271 (1987-03-01), Nagai et al.
Look Edward K.
Magiview Pty. Ltd.
Verdier Christopher
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