Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Plural distributing means immediately upstream of runner
Patent
1982-07-14
1985-04-16
Garrett, Robert E.
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Plural distributing means immediately upstream of runner
415207, 415213C, F04D 2952
Patent
active
045113084
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to axial or mixed flow blowers or suction fans and more particularly to such blowers and fans which exhibit improved stability of operation.
BACKGROUND ART
It is known that conventional fans suffer from the problem of stalling when the gas flow past the fan blades breaks away from the surface of the blades and/or the housing surrounding the fan. The fans and blowers according to the present invention are designed to significantly reduce the liability of a stall condition occurring over a wide range of possible operating conditions.
DISCLOSURE OF THE INVENTION
The present invention consists in an axial or mixed flow blower or suction fan comprising an elongate tubular casing within which is disposed an impeller comprising a hub rotatable about the longitudinal axis of the casing and a plurality of blades extending radially therefrom, the casing comprising a tubular inlet portion which terminates in a tubular intermediate portion of larger cross sectional dimensions than the inlet portion which in turn terminates in a tubular outlet portion which is no larger in its cross sectional dimensions than the inlet portion, the impeller being so positioned that the leading edge of the tip of each blade is positioned within the intermediate portion while the trailing edge thereof is positioned within the outlet portion.
The casing of the blower or fan is preferably circular in cross sectional shape. The inlet portion is preferably frusto-conical or cylindrical while the intermediate and outlet portions are preferably cylindrical. The diameter of the outlet portion should not be greater than the minimum diameter of the inlet portion and is preferably slightly smaller than that minimum diameter. As is conventional in such fans the diameter of the outlet portion should be only slightly larger than the diameter of the circle swept by the rotating blades of the impeller.
The diameter of the intermediate portion is larger than the diameter, or minimum diameter, of the inlet and outlet portions. It is preferred that the diameter of the enlarged intermediate portion be from 1.1 to 1.5 times the diameter of the impeller and most preferably between 1.2 and 1.4 times that diameter.
There are preferably provided a plurality of fixed vanes within the intermediate portion which vanes are preferbly disposed radially of the hub and axially of the casing. It is particularly preferred that these vanes narrow in a downstream direction.
The commencement and termination of the intermediate portion are preferably both abrupt, with the intermediate portion being joined to the inlet or outlet portion by an annular wall portion which lies in a plane at right angles to the longitudinal axis of the fan or blower casing. While it is not essential that the intermediate portion terminates abruptly in a downstream direction, it is essential that this termination takes place, in an axial direction, between the leading and trailing edges of the impeller blades.
The arrangement according to this invention may be used with equal advantage in fixed or variable pitch fans and blowers.
In certain cases it is desirable to provide in the inlet portion a plurality of radially directed guide vanes which are each rotatable about its own longitudinal axis. These guide vanes preferably extend between the wall of the inlet portion and a cylindrical stator disposed coaxially with the casing. These guide vanes are preferably used in axial flow fans and blowers in which the blades of the impeller are not themselves rotatable about their own longitudinal axes. These variable pitch guide vanes may be positioned at angles relative to the longitudinal axis of the fan of from +45.degree. to -90.degree.. The angle is considered to be positive if the vanes cause the incoming gas stream to be moved so as to increase the angle through which the direction of movement of the gas stream is changed by the impeller; it is considered negative when that angle is reduced. A similar convention is used when considering the fixed va
REFERENCES:
patent: 3477382 (1969-11-01), Watson
patent: 3535540 (1970-10-01), Boulogne
patent: 3677660 (1972-07-01), Taniguchi et al.
Abdel-Fattah Adnan M.
Russell Bruce A.
Garrett Robert E.
James Howden Australia Pty. Limited
Pitko Joseph M.
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