Fluid reaction surfaces (i.e. – impellers) – Multiple axially spaced working members – Circumferentially offset
Patent
1990-07-09
1992-03-17
Kwon, John T.
Fluid reaction surfaces (i.e., impellers)
Multiple axially spaced working members
Circumferentially offset
416124, 416127, B64C 1148
Patent
active
050963830
ABSTRACT:
A propeller for an aircraft or fan comprises an even number of propeller blades, at least six in number, which are unsymmetrically arranged around the axis of roation of the propeller in two circumferentially equidistantly spaced groups of at least three blades each. Each blade of each group is paired and longitudinally aligned with a respective blade of another group at the opposite side of the axis of rotation of the propeller, and each two next adjacent blades in each group are offset relative to each other by a spacing angle of between about 15.degree. and 40.degree.. For a selected speed of rotation of the propeller corresponding to a particular blade-tip Mach number, the magnitude of the spacing angle is inversely related to the magnitude of that blade-tip Mach number, for effecting a reduction of the level of the rotational sound harmonics by interference.
REFERENCES:
patent: 1868008 (1932-07-01), Gardner
patent: 4514146 (1985-04-01), Nojiri et al.
Deutsche Forschungsanstalt fur Luft - und Raumfahrt e.V.
Kwon John T.
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