Combustor heat shield with integrated louver and method of manufacturing the same

Description

TECHNICAL FIELD

The present invention relates to gas turbine engine combustors and, more particularly, to combustor heat shields with film cooling louvers.

BACKGROUND OF THE ART

Heat shields are used to protect combustor shells from high temperatures in the combustion chamber. They are typically cast from high temperature resistant materials due to their proximity to the combustion flame. Casting operations are not well suited for complex-shaped parts and as such several constrains must be respected in the design of a combustor dome heat shield. For instance, a heat shield could not be cast with a film cooling louver due to the required tight tolerances between the louver and the heat shield. Also several secondary shaping operations must be performed on the cast heat shield to obtain the final product. Drilling and other secondary shaping operations into high temperature cast materials lead to high tooling cost as wear rates of drills and other shaping tools requires frequent cutting tool re-shaping or replacement.

There is thus a need for further improvements in the manufacture of combustor heat shields.

SUMMARY

In one aspect, there is provided a method for manufacturing a combustor heat shield, comprising the steps of: a) metal injection molding a green heat shield body; b) metal injection molding a green cooling louver; c) positioning said green cooling louver in partial abutting relationship with said green heat shield body so as to form an air cooling gap between a front face of the green heat shield body and the green cooling louver; and d) while said green heat shield body is in intimate contact with said green cooling louver, co-sintering said green heat shield body and said green cooling louver at a temperature sufficient to fuse them together into a one-piece component.

In a second aspect, there is provided a combustor dome heat shield and louver assembly, comprising a metal injection molded heat shield body, a metal injection molded louver, said metal injection molded heat shield and said metal injection molded louver having a pair of interfacing surfaces, and a seamless bond between said metal injection molded heat shield and said metal injection molded louver at said interfacing surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a gas turbine engine having an annular combustor;

FIG. 2 is an enlarged cross-sectional view of a dome portion of the combustor, the combustor shell being protected against excessive heat by a heat shield having a louver for directing a film of cooling air on a hot surface of the heat shield;

FIG. 3 is a back plan view of a heat shield segment; and

FIGS. 4
a and 4b are cross-sectional views illustrating the process by which a metal injection molded louver is permanently fused to a metal injection molded heat shield body by means of a co-sintering process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a gas turbine engine 10 generally comprising in serial flow communication a fan 12 (not provided with all types of engine) through which ambient air is propelled, a multistage compressor 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine 18 for extracting energy from the combustion gases.

The combustor 16 is housed in a plenum 17 supplied with compressed air from compressor 14. As shown in FIG. 2, the combustor 16 typically comprises a combustion shell 20 defining a combustion chamber 21 and a plurality of fuel nozzles (only one being shown at 22), which are typically equally spaced about the circumference of the combustion chamber 21 in order to permit a substantially uniform temperature distribution in the combustion chamber 21 to be maintained. The combustion shell 20 is typically made out from sheet metal. In use, fuel provided by a fuel manifold (not shown) is atomized by the fuel nozzles into the combustion chamber 21 for ignition therein, and the expanding gases caused by the fuel ignition drive the turbine 18 in a manner well known in the art.

As shown in FIG. 2, each fuel nozzle 22 is received in an opening 24 defined in a dome panel 23 of the combustor shell 20. A floating collar 26 is provided between the combustor shell 20 and the fuel nozzle 22. The floating collar 26 provides sealing between the combustor shell 20 and the fuel nozzle 22 while allowing relative movement therebetween. In the axial direction, the floating collar 26 is trapped between the dome panel 23 and a dome heat shield body 28. As shown in FIG. 3, the heat shield body 28 is provided in the form of an arcuate segment extending between a radially inner edge 28a and a radially outer edge 28b and two opposed lateral edges 28c and 28d. A plurality of heat shield bodies 28 are circumferentially disposed in an edge-to-edge relationship to form a continuous 360 degrees annular band on the dome panel 23 of the combustor shell 20. Each heat shield 28 is mounted to the dome panel 23 of the combustor shell 20 at a distance therefrom to define an air gap 30 (FIG. 2). In the illustrated example, the heat shield body 28 is attached to the combustor shell 20 by means of a number of threaded studs 32 (four the example illustrated in FIG. 3) extending at right angles from the back side of the heat shield body 28. The studs 32 protrude through corresponding holes in the dome panel 23 and are secured thereto by washers and self-locking nuts (not shown). Other fastening means could be used as well. A central circular opening 34 is defined in the heat shield body 28 for receiving the fuel nozzle 22. The heat shield body 28 is provided on the back side thereof with an annular flat sealing shoulder 36 which extends about the opening 34 for cooperating with a corresponding flat surface 38 on the front face of the floating collar 26. In operation, compressed air supplied from the engine compressor 14 into the plenum 17 in which the combustor 16 is mounted urges the flat surface 38 of the floating collar 26 against the flat surface 36 of the heat shield body 28, thereby providing a seal at the interface between the heat shield body 28 and the floating collar 26. Holes (not shown) are defined through the combustor shell 20 for directing cooling air into the air gap 30 to cool the back face of the heat shield 28. As shown in FIG. 3, heat exchange promoting structures such as pin fins 39, trip strips and divider walls 41 can be integrally formed on the back side of the heat shield 28 to increase cooling effectiveness.

As shown in FIG. 2, a film cooling louver 40 is provided on the front side of the heat shield body 28. The louver 40 has a radially extending annular deflector portion 42 bending smoothly into an axially rearwardly extending annular flange portion 44. The annular deflector portion 42 extends generally in parallel to and downstream of the front hot surface 35 of the heat shield body 28. The deflector portion 42 is axially spaced from the hot surface 35 of the heat shield 28 so as to define an air gap or plenum 45 therebetween. According to one embodiment, a gap of 0.040″ is provided between the deflector portion 42 and the heat shield 28. The gap is calculated for optimum cooling of the heat shield front face 35. A series of circumferentially distributed cooling holes 46 are defined through the heat shield body 28 about the central opening 34 for allowing cooling air to flow from the air gap 30 into plenum 45 between the louver 40 and the heat shield body 28. The louver 40 re-directs the cooling air flowing through the cooling holes 46 along the hot surface 35. The air deflected by the louver 40 forms a cooling air film on the hot front surface 35 of the heat shield 28. This provides a simple and economical way to increase the heat shield cooling effectiveness.

As can be appreciated from FIGS. 4a and 4b, the heat shield body 28 and the louver 40 are manufactured as separate parts by metal injection molding (MIM) and then the “green” heat shield body and the “green” louver are fused together by means of a co-sintering process. The heat shield body 28 and the louver 40 are made from a high temperature resistant powder injection molding composition. Such a composition can include powder metal alloys, such as IN625 Nickel alloy, or ceramic powders or mixtures thereof mixed with an appropriate binding agent. Other high temperature resistant compositions could be used as well. Other additives may be present in the composition to enhance the mechanical properties of the heat shield and louver (e.g. coupling and strength enhancing agents).

An interfacing annular recess 48 is molded in the front face 35 of the heat shield body 28 coaxially about the central opening 34 for matingly receiving the axially extending flange portion 44 of the louver 40 in intimate contact. The annular recess 48 is bonded by an axially extending shoulder 50 and a radially oriented annular shoulder 52 for interfacing in two normal planes with corresponding surfaces of the axially extending flange portion 44 of the louver 40. This provides for a strong bonding joint between the two parts. The engagement of the axially extending flange portion 44 in the recess 48 of the heat shield 28 also ensures proper relative positioning of the two metal injection molded parts. Accordingly, the louver 40 and the heat shield 28 can be accurately positioned with respect to each other without the need for other alignment structures or fixtures. However, it is understood that the louver 40 and the heat shield 28 could be provided with other suitable male and female aligning structures. The axial cooling gap 45 between the louver 40 and the heat shield 28 is determined by the length of the axially extending flange portion 44 of the louver 40 and the depth of the recess 48 of the heat shield body 28. The cooling holes 46 are molded in place through the heat shield 28. This eliminates the extra step of drilling holes through the heat shield body.

As shown in FIG. 4a, the MIM green louver 40 is placed on top of the MIM green heat shield body 28 while the same is being horizontally supported with its front surface 35 facing upwardly. This operation could also be accomplished in other orientations. The MIM green heat shield body 28 can be held by a fixture to prevent movement thereof while the MIM green louver 40 is being lowered into the interfacing recess 48 of the MIM green heat shield body 28. The MIM green louver 40 can be gently pressed downwardly by hand onto the MIM green heat shield body 28 to ensure intimate and uniform contact between flange portion 44 and shoulders 50 and 52. The applied force must be relatively small so as to not deform the green parts.

Once the MIM green louver 40 is appropriately positioned on the MIM green heat shield body 28, the resulting assembled green part is submitted to a debinding operation to remove the binder or the binding agent before the parts by permanently fused together by heat treatment. The assembled green part can be debound using various aqueous debinding solutions and heat treatments known in the art. It is noted that the assembly of the two separately molded parts could be done either before or after debinding. However, assembly before debinding is preferable to avoid any surface deformation at the mating faces of both parts during the debinding process. It also helps to bind the two parts together.

After the debinding operations, the louver 40 and the heat shield body 28 are co-sintered together to become a seamless unitary component as shown in FIG. 4b. The heat shield body 28 and the louver are preferably fused along their entire interface provided between shoulders 50 and 52 and the axially extending flange portion 44. The sintering operation can be done in inert gas environment or vacuum environment depending on the injection molding composition. Sintering temperatures are typically in the range of about 1100 to about 1200 Degrees Celsius depending on the base material composition of the powder. The co-sintering operation of the heat shield body 28 and the louver 40 takes about 4-8 hours followed by annealing (slow cooling). In some cases, it may be followed with hot isostatic pressing (HIP)—annealing under vacuum to minimize porosities. It is understood that the parameters of the co-sintering operation can vary depending on the composition of the MIM feedstock and on the configuration of the louver 40 and of the heat shield body 28.

It is noted that the density and size (i.e diameter and height) of the pin fins and the other heat exchange promoting structures on the back side of the heat shield have been selected to suit a MIM process and permit easy unmolding of the part. Some of the pin fins near the divider walls have also been integrated to the wall to avoid breakage during moulding.

The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without department from the scope of the invention disclosed. For example, the invention may be provided in any suitable heat shield and louver configuration and in and is not limited to application in reverse flow annular combustors. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.

Claims

1. A combustor dome heat shield and louver assembly for a gas turbine engine, the combustor dome heat shield and louver assembly comprising: a metal injection molded heat shield body,a metal injection molded louver, said metal injection molded heat shield body and said metal injection molded louver having a pair of interfacing surfaces, anda seamless bond between said metal injection molded heat shield body and said metal injection molded louver at said interfacing surfaces.
2. The combustor dome heat shield and louver assembly defined in claim 1, wherein said metal injection molded heat shield body and said metal injection molded louver are separately formed with mating male and female aligning portions, and wherein said pair of interfacing surfaces are provided on respective ones of said male and female aligning portions.
3. The combustor dome heat shield and louver assembly defined in claim 1, wherein said metal injection molded heat shield body has at least one opening for receiving a fuel nozzle tip, and wherein said metal injection molded louver has a flow diverting portion extending radially outwardly relative to said at least one opening at a distance from a front surface of the metal injection molded heat shield body, said flow diverting portion and said front surface defining an air gap.
4. The combustor dome heat shield and louver assembly defined in claim 3, wherein a series of holes are defined through the metal injection molded heat shield body, said series of holes being in flow communication with said air gap.
5. The combustor dome heat shield and louver assembly defined in claim 2, wherein said female aligning portion includes an annular recess formed in said metal injection molded heat shield body, and wherein said male aligning portion includes an annular flange projecting axially from a radially extending flow diverting flange of said metal injection molded louver.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 11/771,141 filed on Jun. 29, 2007, the content of which is hereby incorporated by reference.

US Referenced Citations (166)

Number	Name	Date	Kind
1751448	Campbell, Jr.	Mar 1930	A
2468824	Hughey	May 1949	A
2669090	Jackson	Feb 1954	A
2694245	Rogers et al.	Nov 1954	A
2775566	Crowley	Dec 1956	A
2939199	Striven	Jun 1960	A
3169367	Hussey	Feb 1965	A
3266893	Duddy	Aug 1966	A
3351688	Kingery et al.	Nov 1967	A
3410684	Print	Nov 1968	A
3413704	Addoms, Jr. et al.	Dec 1968	A
3416905	Waugh	Dec 1968	A
3523148	Boyer et al.	Aug 1970	A
3595025	Stöckel et al.	Jul 1971	A
3608309	Hill et al.	Sep 1971	A
3615054	La Botz	Oct 1971	A
3698849	Czerski	Oct 1972	A
3704499	Majkrzak et al.	Dec 1972	A
3775352	Leonard, Jr.	Nov 1973	A
3782989	Mansur	Jan 1974	A
3888663	Reichman	Jun 1975	A
3889349	Kaufman	Jun 1975	A
3925983	La Botz	Dec 1975	A
3982778	Spencer et al.	Sep 1976	A
4011291	Curry	Mar 1977	A
4029476	Knopp	Jun 1977	A
4076561	Lee et al.	Feb 1978	A
4094061	Gupta et al.	Jun 1978	A
4176433	Lee et al.	Dec 1979	A
4197118	Wiech, Jr.	Apr 1980	A
4225345	Adee et al.	Sep 1980	A
4226088	Tsukahara et al.	Oct 1980	A
4236923	Takahashi et al.	Dec 1980	A
4246757	Heberling	Jan 1981	A
4274875	Cadle et al.	Jun 1981	A
4280973	Moskowitz et al.	Jul 1981	A
4283360	Henmi et al.	Aug 1981	A
4386960	Iacovangelo et al.	Jun 1983	A
4415528	Wiech, Jr.	Nov 1983	A
4419413	Ebihara	Dec 1983	A
4472350	Urano	Sep 1984	A
4475344	Mumford et al.	Oct 1984	A
4535518	Jaqua	Aug 1985	A
4590769	Lohmann et al.	May 1986	A
4615735	Ping	Oct 1986	A
4661315	Wiech, Jr.	Apr 1987	A
4702073	Melconian	Oct 1987	A
4708838	Bandyopadhyay et al.	Nov 1987	A
4734237	Fanelli et al.	Mar 1988	A
4765950	Johnson	Aug 1988	A
4780437	Smith	Oct 1988	A
4783297	Ito et al.	Nov 1988	A
4792297	Wilson	Dec 1988	A
4816072	Harley et al.	Mar 1989	A
4839138	Filz	Jun 1989	A
4874030	Kuphal et al.	Oct 1989	A
4881431	Bieneck	Nov 1989	A
4898902	Nagai et al.	Feb 1990	A
4913739	Thümmler et al.	Apr 1990	A
5021208	Ludwig et al.	Jun 1991	A
5059387	Brasel	Oct 1991	A
5059388	Kihara et al.	Oct 1991	A
5064463	Ciomek	Nov 1991	A
5094810	Shira	Mar 1992	A
5098469	Rezhets	Mar 1992	A
5129231	Becker et al.	Jul 1992	A
5135712	Kijima et al.	Aug 1992	A
5155158	Kim	Oct 1992	A
5165226	Newton et al.	Nov 1992	A
5215946	Minh	Jun 1993	A
5244623	King	Sep 1993	A
5250244	Kimura et al.	Oct 1993	A
5279787	Oltrogge	Jan 1994	A
5284615	Ueda et al.	Feb 1994	A
5286767	Rohrbach et al.	Feb 1994	A
5286802	Uesugi et al.	Feb 1994	A
5307637	Stickles et al.	May 1994	A
5310520	Jha et al.	May 1994	A
5312582	Donado	May 1994	A
5328657	Kamel et al.	Jul 1994	A
5332537	Hens et al.	Jul 1994	A
5338617	Workinger et al.	Aug 1994	A
5350558	Kawato et al.	Sep 1994	A
5366679	Streicher	Nov 1994	A
5368795	Quadir	Nov 1994	A
5380179	Nishimura et al.	Jan 1995	A
5397531	Peiris et al.	Mar 1995	A
5398509	North et al.	Mar 1995	A
5403542	Weinl et al.	Apr 1995	A
5409650	Holme	Apr 1995	A
5415830	Zhang et al.	May 1995	A
5421853	Chen et al.	Jun 1995	A
5423899	Krall et al.	Jun 1995	A
5429792	Luk	Jul 1995	A
5437825	Jensen	Aug 1995	A
5450724	Kesseli et al.	Sep 1995	A
5472143	Bartels et al.	Dec 1995	A
5476632	Shivanath et al.	Dec 1995	A
5482671	Weber	Jan 1996	A
5525293	Kagawa et al.	Jun 1996	A
5547094	Bartels et al.	Aug 1996	A
5554338	Sugihara et al.	Sep 1996	A
5574957	Barnard et al.	Nov 1996	A
5590531	Desaulty et al.	Jan 1997	A
5609655	Kesseli et al.	Mar 1997	A
5641920	Hens et al.	Jun 1997	A
5665014	Sanford et al.	Sep 1997	A
5669825	Shira	Sep 1997	A
5722032	Gay	Feb 1998	A
5730929	Majumdar et al.	Mar 1998	A
5848350	Bulger	Dec 1998	A
5864955	Hirai	Feb 1999	A
5950063	Hens et al.	Sep 1999	A
5956955	Schmid	Sep 1999	A
5977230	Yang et al.	Nov 1999	A
5989493	La Salle et al.	Nov 1999	A
5993726	Huang et al.	Nov 1999	A
5993733	Kawai	Nov 1999	A
6008281	Yang et al.	Dec 1999	A
6051184	Kankawa	Apr 2000	A
6060017	Yang et al.	May 2000	A
6071325	Schmitt	Jun 2000	A
6075083	Peiris	Jun 2000	A
6119459	Gomez et al.	Sep 2000	A
6159265	Kinoshita et al.	Dec 2000	A
6171360	Suzuki et al.	Jan 2001	B1
6224816	Hull et al.	May 2001	B1
6224823	Lindenau et al.	May 2001	B1
6289677	Prociw et al.	Sep 2001	B1
6319437	Elsner et al.	Nov 2001	B1
6321449	Zhao et al.	Nov 2001	B2
6322746	LaSalle et al.	Nov 2001	B1
6350407	Sakata et al.	Feb 2002	B1
6399018	German et al.	Jun 2002	B1
6406663	Goransson	Jun 2002	B1
6427446	Kraft et al.	Aug 2002	B1
6428595	Hayashi et al.	Aug 2002	B1
6468468	Neubing et al.	Oct 2002	B1
6560964	Steinhorsson et al.	May 2003	B2
6592787	Pickrell et al.	Jul 2003	B2
6669898	Gressel et al.	Dec 2003	B2
6730263	Ernst et al.	May 2004	B2
6759004	Dwivedi	Jul 2004	B1
6764643	Sagawa et al.	Jul 2004	B2
6838046	Lu et al.	Jan 2005	B2
6843955	Ghosh et al.	Jan 2005	B2
6849230	Feichtinger	Feb 2005	B1
6871773	Fukunaga et al.	Mar 2005	B2
6939509	Kochanek	Sep 2005	B2
7018583	Berger et al.	Mar 2006	B2
7052241	Decker	May 2006	B2
7827800	Stastny et al.	Nov 2010	B2
8316541	Patel et al.	Nov 2012	B2
20020058136	Belhadjhamida	May 2002	A1
20020109260	Boechat	Aug 2002	A1
20030062660	Beard et al.	Apr 2003	A1
20030213249	Pacheco-Tougas et al.	Nov 2003	A1
20050036898	Sweetland	Feb 2005	A1
20050254987	Azzi et al.	Nov 2005	A1
20060127268	Yano et al.	Jun 2006	A1
20070017817	Mueller et al.	Jan 2007	A1
20070020135	Jackson et al.	Jan 2007	A1
20070102572	Bohdal	May 2007	A1
20070104585	Ochiai et al.	May 2007	A1
20070137208	Prociw et al.	Jun 2007	A1
20120073303	McCarren et al.	Mar 2012	A1

Foreign Referenced Citations (18)

Number	Date	Country
983215	Feb 1976	CA
990978	Jun 1976	CA
996784	Sep 1976	CA
2230994	Mar 1997	CA
2204841	Nov 1997	CA
2342328	Mar 2000	CA
2347639	Apr 2000	CA
2327759	May 2001	CA
2388359	May 2001	CA
2418265	Feb 2002	CA
2381828	Oct 2002	CA
0 511 428	Sep 1996	EP
1 046 449	Oct 2000	EP
03 039405	Feb 1991	JP
08 025151	Jan 1996	JP
08260005	Oct 1996	JP
WO 97 38811	Oct 1997	WO
WO 0012248	Mar 2000	WO

Non-Patent Literature Citations (24)

Entry
Powder Metallurgy 2007 Facts—“A Growth Industry Vital to Many Products”; Metal Powder Industries Federation.
Power Injection Moulding International (PIM International) “Flexibility Helps MIM Producer Meet the Demands of a Broad Client Base”.
“An Introduction to Powder Metallurgy Materials and Design”, Isabel J van Rooyen, Metals and Metals Processes, CSIR, Private bag X28, Auckland Park, 2006, South Africa.
NMC: “Enhanced Powder Metallurgy Processing of Superalloys for Aircraft Engine Components”.
NATO:“Powder Injection Molding (PIM) for Low Cost Manufacturing of Intricate Parts to Net-Shape”, Eric Baril et al., pp. 7-1 to 7-12.
NATO: “Metal Injection Moulding: A Near Net Shape Fabrication Method for the Manufacture of Turbine Engine Component”, Benoit Julien et al., pp. 8-1 to 8-16.
Polymer Technologies, Inc.; “Plastic and Metal Injection Molding”; www.polymertechnologies.com.
Phillips Plastics Corporation; “MIM Metal Injection Molding Design Guide”; Nov. 12, 2004; www.phillipsmetals.com.
Egide; “Advanced Material Injection Moulding (AMIM)”.
“The MIM Process”; www.epma.com.
“Powder Injection Molding”; www.powdermetinc.com/Technology.htm.
Cobef (Congresso Braileiro de Engenharia de Fabricacao); Paulo César G. Felix; Philip Frank Blazdel; Ricardo Emilio F.Q Nogueira; “Production of Complex Parts by Low-Pressure Injection Molding of Granite Powders”.
J.E. Zorzi; C.A. Perottoni; J.A. H. da Jornada; “Wax-Based Binder for Low-Pressure Injection Molding and the Robust Proudction of Ceramic Parts”.
Azom.com; “Powder Injection Moulding of Metals, Ceramics and Metal Matrix Composites”; www.azom.com.
Ceramic Industry; Ceratechno '06; Nov. 7-11, 2006; “Advancing Components with Low-Pressure Injection Molding”; www.ceramicindustry.com.
“Injection Molding Microstructures”: www.ecs.umass.edu.
TEMS—a division of ND Industries, Inc.; “Low Pressure Injection Overmolding Ruggedizing Electrical/Electronic Components”; www.temsnd.com.
Peltsman; “Low Pressure Injection Molding”; www.pelcor.com.
Peltsman; “Automatic LPM Machine MIGL—37”; www.pelcor.com.
Axom.com; “Low Pressure Powder Injection Moulding of Metals, Ceramics and Metal Matrix Composites”; www.azom.com.
Goceram; “Medium Pressure Powder Injection Molding (MEDPIMOLD) Process”; www.goceram.com.
Goceram; “Medium Pressure Injection Moulding Machines”; www.goceram.com.
U.S. Appl. No. 60/139,354, filed Jun. 15, 1999, Lasalle, et al.
U.S. Appl. No. 11/551,021, filed Oct. 19, 2006, Stastny et al.

Related Publications (1)

	Number	Date	Country
	20130031909 A1	Feb 2013	US

Divisions (1)

	Number	Date	Country
Parent	11771141	Jun 2007	US
Child	13648530		US

Combustor heat shield with integrated louver and method of manufacturing the same

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