CONTROL OF NOISE AND INSTABILITIES IN JET ENGINES, COMPRESSORS, TURBINES, HEAT EXCHANGERS AND THE LIKE

• US 3,776,363 A
• Filed: 05/10/1971
• Issued: 12/04/1973
• Est. Priority Date: 05/10/1971
• Status: Expired due to Term

• Current Assignee: Arnold M. Kuethe, Board of Regents of the University of Michigan (University of Michigan), University of Michigan
• Original Assignee: Arnold M. Kuethe
• Inventors: Kuethe, Arnold M.
• Primary Examiner(s): Wilkinson, Richard B.
• Assistant Examiner(s): Gonzales, John F.
• Application Number:
  US05/141,617
• Time in Patent Office: 939 Days
• Field of Search: 181/33P,36A,33H,33HA,33HB,33HC,33HD,43,51,33C 415/119,DIG.1 244/41,1N,4A 416/500,235,228
• US Class Current: 181/213
• CPC Class Codes: B64C 2230/26 by using rib lets or hydrophobic surfaces
• CPC Class Codes: F01D 5/16 for counteracting blade vibration
• CPC Class Codes: F04D 29/681 especially adapted for elastic fluid pumps
• CPC Class Codes: Y02T 50/10 Drag reduction

Abstract

Intrinsic sound, noise and instabilities directly or indirectly due to the shedding of cross-stream vortices caused when air or fluid moves over the trailing edge of a plate, blade, vane or the like are reduced by the formation of relatively steady-state streamwise vortices upstream of the terminal edge. The invention is applied to turbine and compressor blades, jet tube inlets and exits, heat-exchanger tubes and the like by placing or forming streamwise vortex-inducing generators within the boundary layer on the shedding item so that the induced streamwise vortices trail off of the trailing edge and suppress the formation of cross-stream disturbances. Through this process, noise disturbances which would otherwise amplify to high sound intensitites and/or large flow disturbances, high structural stresses and loss of efficiency through passage over successive shedding items are suppressed in their early stages of development.

Claims

1. The method of reducing noise and vibration inducing Karman vortices at the trailing edge of a turbine blade or vane in a jet engine or the like comprising the step of forming a spanwise series of streamwise vortices at locations on the surface of the blade or vane upstream of the trailing edge thereof and no higher than the height of the boundary layer so that said vortices flow past said trailing edge and downstream thereof to provide an increase spanwise flow component at said trailing edge.

2. The method of claim 1 in which said streamwise vortices are formed by positioning elongated wave elements on said surface at an acute angle to the direction of flow thereover.

3. A jet engine, turbine or compressor blade element having reduced sound producing characteristics in which a curved flow control surface terminates at a cross-stream trailing edge, the improvement comprising means defining at least one elongated vortex producing element on said surface positioned slightly upstream of said trailing edge at an acute angle to the direction of flow over said surface and situated entirely within the boundary layer air effective to produce a streamise vortex extending off said trailing edge and into the region normally occupied by Karmancross-sTream vortices.

4. The blade of claim 3 further comprising a plurality of said elements positioned in a spanwise row adjacent said trailing edge.

5. The blade of claim 4 in which said elements are formed on each of the pressure and suction surfaces of said blade adjacent said trailing edge.

6. The method of suppressing the shedding of noise or vibration-producing cross-stream unsteady vortices which are otherwise produced downstream of the flow separation line of a body such as a tube, duct, turbine blade or vane, in a fluid stream comprising the steps of forming wholly within the boundary layer a plurality of spanwise-separated primary streamwise relatively steady-state vortices at locations adjacent the surface of said body upstream of the separation line, simultaneously inducing the formation of a plurality of counter-rotating streamwise vortices intermediate said primary vortices, and causing said streamwise vortices to extend downstream of such separation line into the downstream region normally occupied by cross-stream vortices to effect a spanwise velocity component at the flow separation line for the suppression of the shedding of cross-stream vortices.

7. The method of claim 6 in which said streamwise primary vortices are formed by elongated waves elements on said surface positioned at an acute angle to the direction of flow of said fluid stream.

8. In a jet engine having compressor and turbine blades, the improvement in jet engine structure reducing intrinsic sound emission therefrom, comprising means on the surface of a substantial number of said blades defining elongated vortex-producing elements, said elements being elongated in the streamwise sense, positioned wholly within the boundary layer upstream of the trailing edge of said blades and extending at an acute angle to the direction of air flow over the blade surface to produce streamwise, relatively steady-state vortices extending rearwardly of the corresponding trailing edges to suppress the formation of sound-producing cross-stream pressure disturbances behind said blades.

9. A body in a relatively moving fluid stream having a reduced tendency for producing noise and vibrations and having a surface exposed to said stream terminating in a terminal edge or a flow separation region, comprising means on said surface upstream of said edge or region defining a spanwise series of elongated surface elements positioned wholly within the fluid stream boundary layer and extending at an acute angle to the direction of flow of said fluid stream and which utilize the boundary layer vorticity to form a plurality of streamwise vortices in said fluid stream which trail downstream of said edge or region and which induce spanwise components of flow to suppress the formation of noise and vibration-inducing Karman vortices.

10. The body of claim 9 having opposed said surfaces which effectively terminate at a common edge defining said terminal edge or region, and said vortex-forming elements being associated with each of said surfaces.

11. The body of claim 10 in which the vortex-forming means on said surfaces are related in spanwise spacing to each other to form mutually reinforcing vortices downstream of said edge.

12. The body of claim 9 in which the spacing between adjacent spanwise said elements is sufficient to induce the formation of a counter-rotating vortex between an adjacent pair of primary element-inducing vortices.