Claims
- 1. A method for minimizing a fluid leakage flow rate across a rotor blade tip during operation of a rotor blade assembly having a casing, a rotor positioned within the casing, at least one rotor blade attached to the rotor, the rotor blade having a leading edge, a trailing edge, a tip including a tip surface spaced from the casing by a gap, a root portion, a pressure side and a suction side, a fluid flow across the blade tip from the pressure side to the suction side, the method comprising:
- (i) determining a fluid flow relationship between a fluid leakage flow rate across the blade tip surface, a fluid leakage flow area on the tip surface, and the gap between the casing and the tip surface according to the formula ##EQU2## where: w=leakage flow rate,
- A=leakage flow area between a shroud and a tip surface area (delta x chord fraction),
- g=gravitational constant (32.2 ft. per sec..sup.2),
- .DELTA.P=chordwise pressure differential (suction to pressure side),
- .rho.=leakage fluid density,
- C hd 1 l , C hd 2=flow constants for a given gap distance,
- N=number of recesses on at a tip surface area,
- (ii) deriving a number of recesses based on the derivative values of C hd 1 l and C hd 2 l of formula (1),
- (iii) machining the recesses into the blade tip surface in conformity with formula
- .ltoreq. D/Z.ltoreq.3 (a)
- wherein D is the recess depth and Z is the recess width, and the formula
- 1.ltoreq.Z/.delta..ltoreq.30 (b)
- wherein .delta. is the gap value between the casing and the blade tip surface and Z is as above,
- (iv) establishing suction vortices within each recess,
- (v) diverting at least a portion of the fluid flowing from the pressure side to the suction side into each recess; and
- (vi) minimizing the fluid flow across the blade tip surface.
- 2. A method according to claim 1 wherein the value of C hd 1 l is about 1.4.
- 3. A method according to claim 1 wherein the value of C hd 2 l is about 2.0.
- 4. A method according to claim 1 wherein the recesses are machined into the tip surface in a staggered configuration.
- 5. A method according to claim 1 wherein the recesses are machined into the tip surface to effect a concentration of recesses in the range of from about 6 to about 10 recesses per inch of blade width section.
Government Interests
The invention described herein was made in the performance of work under NASA Contract No. NAS8-27980 and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958 (72 Stat. 435; 42 USC 2457).
This is a continuation-in-part of co-pending application Ser. No. 661,950 filed on Oct. 17, 1984, now abandoned.
US Referenced Citations (9)
Foreign Referenced Citations (2)
Number |
Date |
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134451 |
Oct 1929 |
CHX |
2105415 |
Mar 1983 |
GBX |
Continuation in Parts (1)
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Number |
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661950 |
Oct 1984 |
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