Compressor aerofoil

• US 9,046,111 B2
• Filed: 02/18/2011
• Issued: 06/02/2015
• Est. Priority Date: 02/24/2010
• Status: Expired due to Fees

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Harvey, Neil W., Bolger, John J.
• Primary Examiner(s): Wiehe, Nathaniel
• Assistant Examiner(s): Brownson, Jeffrey A
• Application Number:
  US13/030,609
• Publication Number:
  US 20110206527A1
• Time in Patent Office: 1,565 Days
• US Class Current: 1/1
• CPC Class Codes: F01D 5/141 Shape, i.e. outer, aerodynamic form F01D5/148 - F01D5/20 take precedence; blade construction F01D5/147
• CPC Class Codes: F04D 29/324 Blades
• CPC Class Codes: F04D 29/544 Blade shapes
• CPC Class Codes: F04D 29/666 by means of rotor construction or layout, e.g. unequal distribution of blades or vanes
• CPC Class Codes: F04D 29/681 especially adapted for elastic fluid pumps
• CPC Class Codes: F05D 2250/70 Shape

Abstract

An aerofoil for a compressor comprising a suction surface and a pressure surface with a thickness distribution defined therebetween, the aerofoil further comprising a first local maximum in the thickness distribution and a second local maximum in the thickness distribution, the second local maximum being downstream of the first local maximum and the second local maxima being formed by a first region of concave curvature in the suction surface between the first and second local maxima, wherein the second local maximum is disposed such that in use a boundary layer upstream of the second local maximum on the suction surface is thinned by the second local maximum, and in addition the boundary layer may be sufficiently thinned so that an interaction of an upstream flow feature with the thinned boundary layer is capable of generating a turbulent spot with a calmed region downstream of the turbulent spot.

Claims

1. A turbine engine compressor aerofoil comprising a leading edge, a trailing edge, a suction surface and a pressure surface between the leading edge and the trailing edge, the aerofoil further comprising in a region of a span of the aerofoil a maximum thickness of the aerofoil between the leading edge and a midpoint of the aerofoil chord and a maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge, the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge being downstream of the maximum thickness of the aerofoil between the leading edge and a midpoint of the aerofoil chord and a first region of concave curvature in the suction surface between the two maxima, wherein

the pressure surface has continuous concavity from the leading edge to at least 75% of the chord length,

the aerofoil further comprises a second region of concave curvature in the suction surface, the second region of concave curvature being downstream of the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge,

the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge immediately follows downstream of the maximum thickness of the aerofoil between the leading edge and a midpoint of the aerofoil chord,

is disposed at a point in the rear third of the aerofoil chord, corresponds to a maximum thickness of the aerofoil, and is greater than a thickness of the maximum thickness of the aerofoil between the leading edge and the midpoint of the aerofoil chord.

2. An aerofoil as claimed in claim 1, wherein the aerofoil further comprises a maximum thickness of the aerofoil between the maximum thickness between the midpoint of the aerofoil chord and the trailing edge and the trailing edge, the maximum thickness of the aerofoil between the maximum thickness between the midpoint of the aerofoil chord and the trailing edge and the trailing edge being downstream of the second region of concave curvature.

3. An aerofoil as claimed in claim 1, wherein the acceleration parameter near to and upstream of the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge exceeds a value in the range of 3.0×

10<sup>−

6</sup> to 3.5×

10⁶.

4. An aerofoil as claimed in claim 1, wherein the variation in the first derivative of the suction surface profile with respect to the axial chord is continuous.

5. An aerofoil as claimed in claim 1, wherein the value of the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge varies along the region of the span of the aerofoil.

6. An aerofoil as claimed in claim 1, wherein the region extends the whole span of the aerofoil.

7. An aerofoil as claimed in claim 6, wherein the aerofoil has a secured end and a tip separated by the aerofoil span and the region is located beyond a mid-span of the aerofoil measured from the secured end.

8. An aerofoil as claimed in claim 1, wherein the aerofoil has two secured ends separated by the aerofoil span and the region is located mid-span of the aerofoil.

9. A compressor comprising the aerofoil of claim 1.

10. An aerofoil as claimed in claim 1, wherein the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge is disposed such that in use a boundary layer upstream of the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge on the suction surface is thinned by the maximum thickness of the aerofoil between the midpoint of the aerofoil chord and the trailing edge.

11. An aerofoil as claimed in claim 1, wherein the first region of concave curvature in the suction surface between the two maxima has a full velocity profile resembling that of a laminar boundary layer.

12. An aerofoil as claimed in claim 1, wherein the first region of concave curvature in the suction surface between the two maxima is substantially laminar.

13. An aerofoil as claimed in claim 1, wherein the pressure surface has a portion that is convex that leads into a more sharply concave portion towards the trailing edge.

14. A turbine engine compressor aerofoil comprising a leading edge, a trailing edge, a suction surface and a pressure surface between the leading edge and the trailing edge with a thickness defined therebetween, the aerofoil further comprising in a range of the span of the aerofoil a maximum thickness of the aerofoil between the leading edge and a midpoint of the aerofoil chord in the thickness distribution disposed before the midpoint of the aerofoil chord, the suction surface having a primary region of concave curvature in the suction surface aft of the maximum thickness of the aerofoil between the leading edge and the midpoint of the aerofoil chord and a region of convex curvature disposed aft of the primary region of concave curvature and the pressure surface having a primary region of convex curvature aft of the maximum thickness of the aerofoil between the leading edge and the midpoint of the aerofoil chord, wherein the aerofoil has a further region of concave curvature in the suction surface aft of the primary region of concave curvature in the suction surface.

15. A turbine engine compressor aerofoil as claimed in claim 14, wherein the thickness of the compressor aerofoil falls monotonically along the chord from the maximum thickness of the aerofoil between the leading edge and the midpoint of the aerofoil chord to the trailing edge.

16. A turbine engine compressor aerofoil according to claim 14, wherein the aerofoil has a further region of convex curvature in the pressure surface aft of the primary region of convex curvature in the pressure surface.

17. A turbine engine compressor aerofoil according to claim 14, wherein the location of the primary region of pressure surface convex curvature varies along the range of the span of the aerofoil.

18. An aerofoil as claimed in claim 14, wherein the curvature of the primary region of pressure surface convex curvature varies along the range of the span of the aerofoil.

19. A compressor comprising the aerofoil of claim 18.

20. An aerofoil as claimed in claim 14, wherein the range extends the whole span of the aerofoil.

21. An aerofoil as claimed in claim 14, wherein the aerofoil has a secured end and a tip separated by the aerofoil span and the range is located beyond mid-span of the aerofoil measured from the secured end.

22. An aerofoil as claimed in claim 14, wherein the aerofoil has two secured ends separated by the aerofoil span and the region is located mid-span of the aerofoil.

23. An aerofoil as claimed in claim 14, wherein the aerofoil has a secured end and a tip wherein the normalised aerofoil exit angle at 70% of the aerofoil span measured from the secured end is greater than the normalised exit angle at the tip.