Increased impact resistance in hollow airfoils

• US 5,584,660 A
• Filed: 04/28/1995
• Issued: 12/17/1996
• Est. Priority Date: 04/28/1995
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Carter, David B., Weisse, Michael A.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): LARSON, JAMES
• Application Number:
  US08/430,948
• Time in Patent Office: 599 Days
• Field of Search: 416/232, 416/233, 416/DIG. 2, 29/889.72
• US Class Current: 416/233
• CPC Class Codes: B23P 15/04 turbine or like blades from several pieces
• CPC Class Codes: F01D 5/147 Construction, i.e. structural features, e.g. of weight-saving hollow blades F01D5/148, F01D5/16 and F01D5/20 take precedence; blade shape F01D5/141; blades with cooling or heating channels or cavities F01D5/18; heating, heat-insulating or cooling means on blades F01D5/18
• CPC Class Codes: F05D 2200/23 Logarithm
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10S 416/02 Formulas of curves
• CPC Class Codes: Y10T 29/49339 Hollow blade

Abstract

A hollow airfoil (10) for a gas turbine engine having a leading edge (12), a trailing edge (14), a pressure side (20), and a suction side (22) includes a plurality of internal spanwise stiffening ribs (31-35) that are arranged in a logarithmic pattern. The particular arrangement of internal fibs (31-35) optimizes stiffness of the airfoil (10) without significantly increasing the weight thereof.

Claims

1. A hollow blade for a gas turbine engine, said blade having a leading edge and a trailing edge extending radially spanwise from a bottom portion to a top portion of said blade, said blade having a suction side and a pressure side extending chordwise from said leading edge to said trailing edge, said blade having a leading edge solidity formed at said leading edge thereof, said hollow blade characterized by:

a plurality of internal spanwise stiffening ribs extending substantially radially spanwise and joining said pressure side with said suction side, said plurality of spanwise stiffening ribs defining a plurality of cavities therebetween, said plurality of spanwise ribs having logarithmic spacing to reduce stiffness discontinuity in said hollow blade.

2. The hollow blade according to claim 1 further characterized by:

said logarithmic spacing adhering to formula;

space="preserve" listing-type="equation">D=A e.sup.xt

wherein t=0, 1, 2, 3 etc. and represents a sequential number of each said spanwise stiffening rib following said leading edge solidity with said leading solidity being defined as the zero rib;

A and x are empirically derived coefficients;

e is a natural logarithmic function; and

D is the distance from said leading edge to said t^th rib.

3. The hollow blade according to claim 2 further characterized by:

said empirically derived coefficient A being set equal to chordwise distance between said leading edge and an end of said leading edge solidity.

4. The hollow blade according to claim 3 further characterized by:

the chordwise distance between said leading edge and said end of said leading edge solidity for deriving said coefficient A being measured at approximately eighty percent (80%) of radial span from said bottom portion of said hollow blade.

5. The hollow blade according to claim 4 further characterized by:

said coefficient x being derived after location of one of said spanwise stiffening ribs was ascertained.

6. The hollow blade according to claim 1 further characterized by:

said logarithmic spacing being maintained approximately from sixty percent (60%) to one hundred percent (100%) of radial span from said bottom portion towards said top portion of said hollow blade.

7. The hollow blade according to claim 1 further characterized by:

said plurality of spanwise stiffening ribs having uniform spacing from said bottom portion of said hollow blade to approximately sixty percent (60%) of radial span thereof.

8. The hollow blade according to claim 1 further characterized by:

said logarithmic spacing being maintained within first sixty percent (60%) of chordwise span of said hollow blade.

9. The hollow blade according to claim 1 further characterized by:

a plurality of chordwise ribs extending chordwise and interconnecting with said plurality of spanwise stiffening ribs.

10. The hollow blade according to claim 1 further characterized by:

each said spanwise stiffening rib having a curvilinear shape.

11. The hollow fan blade according to claim 1 further characterized by:

said logarithmic spacing adhering to formula;

space="preserve" listing-type="equation">D=A 10.sup.yt

wherein t=0, 1, 2, 3 etc. and represents a sequential number of each said spanwise stiffening rib following said leading edge solidity with said leading solidity being defined as the zero rib;

A and y are empirically derived coefficients; and

D is the distance from said leading edge to said t^th rib.

12. A hollow airfoil for a gas turbine engine, said airfoil having a leading edge and a trailing edge extending radially spanwise from a bottom portion to a top portion of said airfoil, said airfoil having a suction side and a pressure side extending chordwise from said leading edge to said trailing edge, said airfoil having a leading edge solidity formed at said leading edge thereof, said hollow airfoil characterized by:

a plurality of internal spanwise stiffening ribs extending substantially radially spanwise and joining said pressure side with said suction side, said plurality of spanwise ribs being arranged in a logarithmic pattern to reduce stiffness discontinuity in said hollow airfoil, said logarithmic pattern adhering to formula;

space="preserve" listing-type="equation">D=A e.sup.xt

wherein t=0, 1, 2, 3 etc. and represents a sequential number of each said spanwise stiffening rib following said leading edge solidity with said leading solidity being defined as the zero rib;

A and x are empirically derived coefficients;

e is a natural logarithmic function; and

D is the distance from said leading edge to said t^th rib.

13. A method for fabricating a hollow airfoil having a leading edge and a trailing edge extending radially spanwise, said airfoil having a suction side and a pressure side extending chordwise from said leading edge to said trailing edge, said airfoil having a leading edge solidity formed at said leading edge thereof, said method comprising the steps of:

determining chordwise length of said leading edge solidity;

setting an optimum spacing for a first spanwise stiffening rib extending radially spanwise and joining said pressure side with said suction side so that a first cavity is defined between said first stiffening rib and said leading edge solidity;

spacing subsequent spanwise stiffening ribs in a logarithmic pattern to reduce stiffness discontinuity in said hollow airfoil.

14. The method for fabricating a hollow airfoil according to claim 13 wherein said logarithmic pattern being expressed as:

space="preserve" listing-type="equation">D=A e.sup.xt

wherein t=0, 1, 2, 3 etc. and represents a sequential number of each said spanwise stiffening rib following said leading edge solidity with said leading solidity being defined as the zero rib;

A and x are empirically derived coefficients;

e is a natural logarithmic function; and

D is the distance from said leading edge to the t^th rib.

15. The method for fabricating a hollow airfoil according to claim 13 wherein said logarithmic pattern being expressed as:

space="preserve" listing-type="equation">D=A 10.sup.yt

wherein t=0, 1, 2, 3 etc. and represents a sequential number of each said spanwise stiffening rib following said leading edge solidity with said leading solidity being defined as the zero rib;

A and y are empirically derived coefficients; and

D is the distance from said leading edge to the t^th rib.