# US 9,518,739 B2 · Combustor heat shield with carbon avoidance feature

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- Number: US 9,518,739 B2
- Document ID: US9518739B2
- Status: Granted
- Kind: B2
- Application number: 13/790,451
- Filed: 2013-03-08
- Published: 2014-09-11
- Granted: 2016-12-13
- Earliest claimed: 2013-03-08
- Assignees: Pratt & Whitney Canada Corp.
- Applicants: Pratt & Whitney Canada Corp.
- Inventors: Tin Cheung John Hu; Robert Sze; Honza Stastny
- Web page: https://patentgrep.com/patent/US9518739B2

## CPC

- F23R 3/04: Air inlet arrangements
- F23R 3/002: {Wall structures (F23R3/02 and F23R3/007 take precedence)}
- F23R 3/005: {Combined with pressure or heat exchangers}
- F23R 3/007: {constructed mainly of ceramic components}
- F23R 3/06: Arrangement of apertures along the flame tube
- F23R 3/10: for primary air (F23R3/06, F23R3/045 take precedence)
- F23R 2900/00004: Preventing formation of deposits on surfaces of gas turbine components, e.g. coke deposits
- F23R 2900/03041: Effusion cooled combustion chamber walls or domes
- F23R 2900/03044: Impingement cooled combustion chamber walls or subassemblies
- F23R 2900/03045: Convection cooled combustion chamber walls provided with turbolators or means for creating turbulences to increase cooling
- Y02E 20/34: Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
- F23R: GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS (fluidised bed combustion apparatus specially adapted for operation at superatmospheric pressures F23C10/16)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

The build-up of carbon deposition on the front face of a combustor heat shield is discouraged by jetting air out from the front face of the heat shield with sufficient momentum to push approaching fuel droplets or rich fuel-air mixture way from the heat shield.

## Claims

### Claim 1

A gas turbine engine combustor comprising:
a combustor shell defining a combustion chamber;
a heat shield mounted to an inner surface of the combustor shell, the heat shield having a back face facing the inner surface of the combustor shell and being spaced therefrom to define an air gap, the heat shield having localized areas on an opposed front face thereof where carbon residues tend to build-up during engine operation; and
an airflow path extending along a generally straight line across the combustor shell, the air gap and the heat shield at each of said localized areas;
each airflow path comprising an impingement hole defined in the combustor shell and disposed directly on top of a group of carbon purge air holes defined in the heat shield so that an axial projection of the impingement hole onto the back face of the heat shield captures the group of carbon purge air holes, wherein the axial projection is taken along a longitudinal axis of the combustor, the carbon purge air holes having respective axes extending in a direction generally parallel to an axis of the impingement hole and generally normal to the front face of the heat shield, the impingement holes and the carbon purge air holes being sized to preserve enough air momentum at the exit of the purge air holes to deflect fuel droplets away from the front face of the heat shield to impede carbon build-up on said front face,
wherein rails extend from the back face of the heat shield in sealing engagement with the inner surface of the combustor shell to seal the air gap, and wherein effusion film cooling holes are defined in the heat shield, the cross-sectional area of the carbon purge air holes being greater than that of the of the effusion film cooling holes.

### Claim 2 (depends on 1)

The gas turbine engine combustor defined in claim 1, wherein the carbon purge air holes have a cross-sectional area which is smaller than the cross-sectional area of the impingement hole, the impingement hole directing an air impingement jet on an impingement zone on the back face of the heat shield, at least a plurality of said carbon purge air holes being disposed within the confines of said impingement zone.

### Claim 3 (depends on 1)

The gas turbine engine combustor defined in claim 1, wherein the carbon purge air holes have a diameter which is smaller than that of dilution holes defined in the combustor shell.

### Claim 4 (depends on 1)

The gas turbine engine combustor defined in claim 1, wherein the carbon purge air holes have a cross-sectional area greater than that of effusion-type cooling holes used for forming a cooling film over the front face of the heat shield.

### Claim 5 (depends on 1)

The gas turbine engine combustor defined in claim 1, further comprising impingement cooling holes defined in the combustor shell for directing impingement cooling jets against the back face of the heat shield, the impingement cooling holes having a smaller cross-sectional area than the impingement holes of the airflow path extending through the localized areas subject to carbon deposition.

### Claim 6 (depends on 1)

The gas turbine engine combustor defined in claim 1, wherein the localized areas subject to carbon deposition are located in a primary zone of the combustor near fuel injection points thereof.

### Claim 7 (depends on 1)

The gas turbine engine combustor defined in claim 1, wherein the airflow path defines a flow direction which is generally parallel to the axis of the impingement hole and the respective axes of the carbon purge air holes.

### Claim 8 (depends on 1)

The gas turbine engine combustor defined in claim 1, wherein the rails sealingly engage the combustor shell on opposed sides of the impingement hole and the group of carbon purge air holes.