Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Radial flow devices
Patent
1979-03-06
1984-07-10
Casaregola, Louis J.
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Radial flow devices
416242, 244 35R, B64C 1118
Patent
active
044590830
ABSTRACT:
This invention is an airfoil which has particular application to the blade or blades of rotor aircraft and aircraft propellers. The airfoil thickness distribution, camber and leading edge radius is shaped to locate the airfoil crest at a more aft position along the chord, and to increase the freestream Mach number at which sonic flow is attained at the airfoil crest. The upper surface of the airfoil has a general reduction in the surface slope back to the maximum ordinate which is about 40 percent of the airfoil chord. The reduced slope causes a reduction in velocity at the airfoil crest at lift coefficients from zero to the maximum lift coefficient. The leading edge radius is adjusted or shaped so that the maximum local Mach number at 1.25 percent chord and at the designed maximum lift coefficient is limited to about 0.48 when the Mach number normal to the leading edge is approximately 0.20. The lower surface leading edge radius is shaped so that the maximum local Mach number at the leading edge is limited to about 0.29 when the Mach number normal to the leading edge is approximately 0.20 and the lift coefficient is in the range of 0.0 to -0.2. This design moves the drag divergence Mach number associated with the airfoil to a higher Mach number over a range of lift coefficients resulting in superior aircraft performance.
REFERENCES:
patent: 1719293 (1929-07-01), Gripon
patent: 3558081 (1971-01-01), Williams
patent: 3902821 (1975-09-01), Robinson
Casaregola Louis J.
Manning John R.
Osborn Howard J.
The United States of America as represented by the Administrator
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