Manufacturing assembly and method for manufacturing a fan blade

Abstract

The present disclosure relates to an assembly for formation of a fan blade. The assembly comprises a suction panel; a pressure panel; and a membrane having a leading edge and a trailing edge. The membrane is sandwiched between the suction panel and pressure panel. The membrane comprises a gas entry slot extending in a radial direction, the gas entry slot having a radially outer receiving portion for receiving a pipe, and a radially inner portion. The radially inner portion of the gas entry slot has a substantially uniform width in a direction between the leading and trailing edge of the membrane.

Claims

1. An assembly for formation of a fan blade, the assembly comprising: a suction panel; a pressure panel; a membrane sandwiched between the suction panel and pressure panel, wherein: the membrane has a leading edge and a trailing edge, and the membrane comprises a gas entry slot extending in a radial direction, the gas entry slot having a radially outer receiving portion for receiving a pipe, and a radially inner portion wherein the radially inner portion of the gas entry slot has a uniform width in a direction between the leading and trailing edge of the membrane; and a pipe, having an internal cross-sectional area X, inserted into the receiving portion, wherein the width (W) of the radially inner portion in the direction between the leading and trailing edges is defined by: W=X/T, where T is the thickness of the membrane.

2. The assembly according to claim 1 wherein the width of the radially inner portion of the gas entry slot in the direction between the leading and trailing edges of the membrane is less than 3 mm.

3. The assembly according to claim 2 wherein the width of the radially inner portion of the gas entry slot in the direction between the leading and trailing edges of the membrane is between 1.1 and 0.8 mm.

4. The assembly according to claim 1 wherein the width (W) of the radially inner portion in the direction between the leading and trailing edges is defined:
W=0.785 mm.sup.2/T where T is the thickness of the membrane.

5. The assembly according to claim 1 wherein the radially inner portion of the gas entry slot comprises a hook portion where the radially inner portion deflects through greater than 90 degrees.

6. The assembly according to claim 5 wherein the radially inner portion deflects through 135 degrees.

7. The assembly according to claim 5 wherein the gas entry slot comprises a meander portion radially outwards of the hook portion.

8. The assembly according to claim 1 wherein the pipe is inserted into the receiving portion to a depth matching a depth of the receiving portion such that the pipe abuts the radially inner portion of the gas entry slot.

9. A method of forming a fan blade comprising providing the assembly according to claim 1 wherein the membrane has a thickness (T) and inserting the pipe having an internal cross-sectional area (X) into the gas entry slot in the membrane, wherein the radially inner portion has a width (W) in a direction between the leading and trailing edge of the membrane such that:
W=X/T.

10. The method according to claim 9 further comprising bonding peripheries of the pressure panel, suction panel and membrane prior to inserting the pipe.

11. The method according to claim 9 further comprising inserting the pipe into the receiving portion to a depth matching a depth of the receiving portion such that the pipe abuts the radially inner portion of the gas entry slot.

12. The method according to claim 9 comprising flowing gas into the assembly through the pipe in order to inflate the assembly.

13. The method according to claim 9 wherein the method further comprises sealing the gas entry slot.

Description

DESCRIPTION OF THE DRAWINGS

(1) Embodiments will now be described by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 shows an axial cross-section through a gas turbine engine;

(3) FIG. 2 shows a known assembly for manufacture of a fan blade;

(4) FIG. 3 shows the geometry of the gas entry slot in the known assembly;

(5) FIG. 4 shows the collapse of the gas entry slot after diffusion bonding in the known assembly; and

(6) FIGS. 5 and 6 show a gas entry slot in a membrane for inclusion in an assembly for forming a fan blade.

DETAILED DESCRIPTION

(7) FIGS. 5 and 6 show a membrane 32 having a gas entry slot 33 which extends in a radial direction. It has a radially outer receiving portion 34 and a radially inner portion having a uniform width (W) along its entire length from its outer end 42 (where it joins the receiving portion 34) to its inner end 43. The width (W) is the dimension in a direction extending between the leading edge 45 and the trailing edge 44

(8) The membrane has a thickness (T) of 0.76 mm. The thickness equates to the spacing between the pressure panel 30 and the suction panel 31.

(9) The thickness of the slot (in the direction between the pressure panel 30 and the suction panel 31) equals the thickness of the membrane such that the slot is open to both faces (i.e. the face facing the suction panel and the face facing the suction panel) of the membrane.

(10) The assembly further comprises an inflation pipe 46 (shown in FIG. 5) having an internal cross-sectional area X. For example, where the pipe has an internal diameter of 1 mm, the cross-sectional area is 0.785 mm.sup.2. The external diameter of the pipe is 6.35 mm. The receiving portion 34 has a width of 6.35 mm in order to accommodate the pipe 46.

(11) The width (W) of the radially inner portion of the gas entry slot 33 in the direction between the leading and trailing edges 45, 44 is defined by the following equation:
W=X/T

(12) where X is the cross-sectional area of the pipe and T is the thickness of the membrane.

(13) Accordingly, where the pipe has an internal diameter of 1 mm, the width (W) of the gas entry slot 33 in the direction between the leading and trailing edges 45, 44 is:
W=0.785/0.76=1.03 mm.

(14) This results in the cross-sectional area of the pipe 46 matching the cross-sectional area of the radially inner portion of the gas entry slot 33.

(15) The receiving portion 34 has a depth of 2 mm and the pipe 46 is inserted into the receiving portion to a depth of 2 mm such that the internal diameter of the pipe 46 opens directly into the radially inner portion of the gas entry slot 33 at its outer end 42.

(16) The radially innermost end of the radially inner portion of the gas entry slot 33 comprises a hook portion 47 where the gas entry slot 33 maintains its uniform width but deflects through 163 degrees. The deflection 48 causes the slot 33 to extend in a substantially radially inwards direction such that the inner end 43 of the slot 33 is inwardly spaced from the deflection 48 (the deflection 48 forming the innermost point of the gas entry slot 33).

(17) The hook portion 47 is provided radially inwards of an edge 39 where the eventual cavity within the fan blade will lie.

(18) The gas entry slot 33 also comprises a meander portion 38 radially outwards of the hook portion 47. The meander portion 38 has an external radius of 6.35 mm.

(19) The meander portion 38 is provided radially inwards of the eventual blade tip cone 37.

(20) The meander portion 38 is joined to the receiving portion 34 by a linear, radially-oriented portion 49 having a length of between 40 and 60 mm. The radial spacing between the receiving portion 34 and the radial centre of the meander portion 38 is between 50 and 70 mm.

(21) To manufacture a fan blade, the pressure panel 30, membrane 32 and suction panel 31 are assembled and an evacuation pipe (typically having an outer diameter of 6.35 mm and an inner diameter of 3 mm) is inserted (and welded) into the gas entry slot 33 to fill the receiving portion. The assembly is evacuated and then subjected to diffusion bonding to join the peripheries of the panels 30, 31 and membrane 32.

(22) Next, the evacuation pipe is drilled out and replaced with inflation pipe 46 (having an outer diameter of 6.35 mm and an internal diameter of 1 mm). The inflation pipe is inserted to fill the receiving section and welded into place. The assembly is subjected to super-plastic forming where gas is flowed into the assembly through the gas entry slot 33 to inflate the assembly to form a cavity. The cross-sectional area of the gas entry slot 33 matches the internal cross-sectional area (X) of the inflation pipe 46.

(23) The inventors have determined that eliminating stepped transitions in width within the gas entry slot 33 and/or reducing the width of the gas entry slot 33 reduces the collapse of the gas entry slot 33 during diffusion bonding. In turn, this allows better control of the gas flow (and reduced turbulence) during the cracking stage of super-plastic forming such that defects and therefore rejected components can be minimised.

(24) It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.