Combustor heat shield

Patent metadata

Field	Value
Publication number	US-9534786-B2
Application number	US-201414455159-A
Country	US
Kind code	B2
Filing date	Aug 8, 2014
Priority date	Aug 8, 2014
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

There is provided a combustor comprising a dome and a shell extending from the dome defining a combustion chamber. A dome heat shield is mounted to the dome inside the combustion chamber. A front heat shield is mounted to the shell and spaced therefrom. The dome heat shield has a lip extending generally away from the dome heat shield and generally parallel to the shell and spaced inwardly of the front heat shield to define a gap between the lip and the front heat shield. The front heat shield has a leading edge opposite the lip. The combustor has impingement holes extending through the shell and disposed to direct impingement cooling jets to the upstream portion of the front heat shield. The leading edge, of the front heat shield has at least one scallop defining an opening and disposed to allow the impingement cooling jets to impinge directly on a portion of the peripheral lip adjacent the scallop.

First claim

What is claim is:

1. A gas turbine engine combustor comprising a dome and a shell extending from the dome, the dome and shell cooperating to define a combustion chamber within them, a dome heat shield mounted to the dome inside the combustion chamber, a front heat shield mounted to the shell inside the combustion chamber, the dome heat shield having a peripheral lip extending generally away from the dome heat shield and generally parallel to the shell and spaced inwardly of the front heat shield to define a gap between the peripheral lip and the front heat shield, at least one circumferentially arranged row of impingement holes extending through the shell and disposed to direct impingement cooling jets towards a leading edge of the front heat shield, the cooling jets generally aligned with the peripheral lip, and the leading edge of the front heat shield having at least one peripheral edge scallop defining an opening through the leading edge and disposed to allow the impingement cooling jets to impinge directly on a portion of the peripheral lip adjacent the scallop.

2. The combustor as defined in claim 1 , wherein the front heat shield is provided with effusion holes extending at an angle downstream of the leading edge, the effusion holes defining the limit of an upstream portion of the front heat shield.

3. The combustor as defined in claim 1 , wherein the scallop is cut out in an area of the front heat shield at the leading edge thereof wherein the area is a radial projection of the portion of the peripheral lip.

4. The combustor as defined in claim 3 , wherein the portion of the peripheral lip defines a hot spot.

5. The combustor as defined in claim 4 , wherein the portion of the peripheral lip has a geometric area.

6. The combustor as defined in claim 5 , wherein the scallop is an area between 1.5 and 2 times the geometric area.

7. The combustor as defined in claim 6 , wherein the scallop is a cut-out from the leading edge terminating in concave end portions each having a similar radius of curvature.

8. The combustor as defined in claim 7 , wherein the concave ends have a radius and the slot has a length sufficient to avoid stress cracking at the concave ends.

9. The combustor as defined in claim 7 , wherein the concave ends have a radius sufficient to avoid stress cracking.

10. The combustor as defined in claim 2 , wherein the axis of each effusion hole extends at an angle of between 20° and 25° to the plane of the front heat shield.

11. A heat shield arrangement for a gas turbine engine combustor having an annular dome and inner and outer shells extending from the annular dome, the annular dome and the inner and outer shells defining a combustion chamber; the heat shield arrangement comprising: a dome heat shield mounted to the dome inside the combustion chamber, said dome heat shield having inner and outer lips parallel and spaced from the inner and outer shells respectively; at least two front heat shields mounted to the inner and outer shells respectively; the front heat shields having upstream portions terminating in leading edges so as to define an inner gap and an outer gap with the inner lip and outer lip respectively; the combustor having at least one circumferentially arranged row of impingement holes through the inner and outer shells and disposed to direct impingement cooling jets to the upstream portions of the front heat shields respectively; and the leading edges, of the front heat shields having scallops defining openings allowing the impingement cooling jets to impinge selected portions of the inner and outer lips.

12. A method for cooling hot spots occurring in portions of a lip of a dome heat shield mounted in a spaced relationship to the dome of a combustor in a gas turbine engine, the combustor having a shell depending from the dome and at least one front heat shield mounted to and spaced from the shell; the method including the steps of providing for the formation of a starter film of cooling air, from the dome cooling air, to pass through a gap formed between the lip and the front heat shield; determining a hot spot in an area of the lip, selecting an area of the front heat shield corresponding to a radial projection of the hot spot on the lip; cutting out a scallop along a leading edge of the front heat shield at the selected area of the front heat shield; and providing impingement holes in the shell in an area surrounding the leading edge of the front heat shield, whereby the impingement jets of cooling air can pass by the scallop to impinge on the hot spot area of the lip.

13. The method as defined in claim 12 , wherein the scallop is 1.5 to 2 times the area of the hot pot.

14. The method as defined in claim 12 , wherein the scallop is cut out as a narrow elongated open portion from the leading edge, the scallop having concave corners, the scallop having a length sufficient to avoid local cracking at the corners.

15. The method as defined in claim 12 , wherein the scallop is cut out as a relatively short elongated open portion from the leading edge, the scallop with gradual concave corners sufficient to avoid local cracking at the corners.

16. A method of cooling a dome heat shield having front and back surfaces mounted in a combustor of a gas turbine engine, the dome heat shield having a lip; the method comprising: recuperating air leaking from a combustor dome portion, and directing the leakage air in a gap defined by the lip and a front heat shield mounted in a spaced apart manner to a shell of the combustor; determining the location of hot spots on the lip and a leading edge of the front heat shield; forming scallops in the leading edge of the front heat shield to provide openings allowing impingement air to pass by the front heat shield and impinge the hot spots on lip.

Assignees

• Pratt & Whitney Canada

Inventors

• Sreekanth Sri
• Papple Michael
• Sze Robert

Classifications

• F23R2900/03041

  Effusion cooled combustion chamber walls or domes · CPC title

• F23R2900/00005

  Preventing fatigue failures or reducing mechanical stress in gas turbine components · CPC title

• F23R3/10 Primary

  for primary air (F23R3/06, F23R3/045 take precedence) · CPC title