US 20090260366A1

(19) United States

(54) FLAME HOLDER FOR AN AFTERBURNER (22) Filed: Feb. 27, 2009
DUCT OF AUET ENGINE WITH A SPACER
SHOE, AFTERBURNER DUCT AND JET (30) Foreign Application Priority Data
ENGINE COMPRISING AN AFTERBURNER
DUCT Feb. 29, 2008 (FR) ...................................... O8 O1138
(75) Inventors: Jacques Marcel Arthur BUNEL, Publication Classification
Thiais (FR); Yann Francois (51) Int. Cl.
Jean-Claude Vuillemenot, Paris FO2K 3/10 (2006.01)
(FR) (52) U.S. Cl. .......................................................... 6Of765
Correspondence Address: (57) ABSTRACT
OBLON, SPIVAK, MCCLELLAND MAIER &
NEUSTADT, L.L.P. The invention relates to a flame holder (10) for an afterburner
194O DUKE STREET duct of a jet engine, comprising an arm (100) in the form of a
ALEXANDRIA, VA 22314 (US) gutterforming a cavity, a shield (110) for protecting the cavity
of the arm (100) from heat, and an air supply baffle (120)
(73) Assignee: SNECMA, Paris (FR) housed in the cavity. The arm (100), the protective shield
(110) and the air supply baffle (120) are held together by a
(21) Appl. No.: 12/394,570 one-piece spacer shoe (150).
Patent Application Publication Oct. 22, 2009 Sheet 2 of 4 US 2009/0260366 A1
Patent Application Publication Oct. 22, 2009 Sheet 3 of 4 US 2009/0260366 A1
Patent Application Publication Oct. 22, 2009 Sheet 4 of 4 US 2009/0260366 A1
US 2009/0260366 A1 Oct. 22, 2009

FLAME HOLDER FOR AN AFTERBURNER 0009. This alternative is not satisfactory since it requires
DUCT OF AUET ENGINE WITH A SPACER piercing the arm 100 and therefore entails all of the disadvan
SHOE, AFTERBURNER DUCT, AND JET tages mentioned above.
ENGINE COMPRISING AN AFTERBURNER
DUCT
SUMMARY OF THE INVENTION
BACKGROUND OF THE INVENTION AND 0010. In order to rectify at least some of these disadvan
DESCRIPTION OF THE PRIOR ART tages, the Applicant proposes an afterburner flame holder
which does not require performing machining operations on
0001. The present invention relates to the field of jet the body of the arm 100 and/or on the heat shield 120 that
engines comprising an afterburner duct for reheating the mechanically and/or thermally weaken the flame holder.
gases emanating from the gas generator.
0002 Jet engines with afterburners comprise, from Such a flame holder is simple in design and easy to assemble,
upstream to downstream, a gas generator, consisting of a gas thereby reducing its production cost. Moreover, it offers
turbine engine, producing gases heated by combustion, an increased thermal resistance and mechanical strength owing
afterburner duct, and an exhaust nozzle for exhausting the to the absence of weak spots.
gases into the atmosphere. The engine is usually of the 0011. The invention relates to a flame holder for an after
double-flow type, with a central primary flow and a peripheral burner duct of a jet engine, comprising an arm in the form of
secondary flow. a gutter forming a cavity, a shield for protecting the cavity of
0003. The afterburner duct is provided with a liner made of the arm from heat, and an air supply baffle housed in the
a material which is resistant to the gas combustion tempera cavity, wherein the arm, the protective shield and the air
ture, said liner being suitably cooled. At the inlet of the duct, Supply baffle are held together by a one-piece spacer shoe
fuel injection means are arranged in the gas flow path, com comprising at least one spacer lug designed to form a gap (e)
bined with means forming flame holders. between the protective heat shield and at least one wall of the
0004. With reference to FIG. 1, the flame holder means 10 a.

are in the form of radial arms which are arranged in a star 0012 Such a shoe makes it possible to maintain separa
pattern with respect to the engine axis and which pass through tions between the various elements, thus preventing wear
the two flow paths for the primary and secondary flows, said during a vibratory operation.
arms being connected to one another by elements in the form 0013 The gap-producing lug advantageously makes it
of annular sectors 9. With reference to FIG. 2, the integrally possible to form a channel between the protective shield and
cast arms 100 in the form of gutters have a U- or V-shaped the arm So as to allow carbureted air to pass through.
cross section which is open in the downstream direction so as
to create a negative pressure region capable of stabilizing the 0014 Preferably still, the shoe comprises a means for
combustion therein. In at least part of the flame holders 10, retaining the baffle.
fuel injectors 130 are placed inside within the cavity formed 0015 The shoe advantageously makes it possible to retain
between the walls, upstream and in the vicinity of the apex, the baffle without weakening the arm or its protective heat
together with air ventilation baffles 120. Air is bled from the shield.
secondary flow and distributed by the baffles 120 toward the 0016. According to one embodiment of the invention, a
injectors 130. In order to protect these elements, a protective fuel injector is placed inside said cavity of the arm.
heat shield 110 is placed as a covering over this part of the arm 0017 Preferably, the shoe comprises a means for center
100 containing the fuel injectors 130 and the ventilation baffle ing the injector.
120.
0005 Traditionally, as represented in FIG. 2, the air ven 0018. The shoe advantageously makes it possible to center
the injector without weakening the arm or its protective heat
tilation baffle 120 is centered at its upper part and at its lower shield. That makes it possible, advantageously still, to main
part in the cavity of the arm 100. It is held in a radial position tain a constant distance between the injector and the air baffle,
via a tenon 5 on the base of the tube which passes through the thereby facilitating the distribution of air from the air baffle
protective heat shield 110 and thereby rotationally immobi toward the injectors.
lizes the baffle 120 in the arm 100.
(0019 Preferably, the shoe is welded to the air supply
0006. However, it is not desirable to weaken the heat baffle, thus making it possible to avoid any translational
shield 110 by piercing it in order to retain the air baffle 120. movement of the baffle in the arm.
Specifically, the protective heat shield 110, which is generally
made of CMC (ceramic matrix composite), is damaged by (0020 Preferably still, the shoe takes the form of a Y defin
peening and delamination, something which is particularly ing a central branch and two lateral branches, the central
detrimental during vibratory operation. branch comprising a through orifice for retaining the baffle.
0007 Similarly, piercing and machining operations per 0021. The shape of the shoe advantageously makes it pos
formed on protective metal shields lead to a concentration of sible to overcome differential expansions between the arm
and the shoe.
stresses, thereby reducing the efficiency and useful life of said
shields. 0022. The through orifice for retaining the baffle advanta
0008. It is also known practice to pierce the arm 100 at its geously makes it possible to guide and to lock the air baffle.
lower end so as to introduce there the air ventilation baffle 0023 Preferably still, the central branch comprises a
120, which is fastened via a washer 16 welded to the lower through orifice for centering the injector.
end of the air ventilation baffle 120, outside the arm 100, as 0024. The invention relates to a jet engine afterburner duct
represented in FIG. 3. comprising at least one such flame holder.
US 2009/0260366 A1 Oct. 22, 2009

0025. The invention also relates to a jet engine comprising FIG. 5 in the direction II-II shown in FIG. 4. The arm 100
such an afterburner duct. defines a cavity, between the upstream apex and the free
downstream edges of the two walls 101a and 101b, which is
BRIEF DESCRIPTION OF THE DRAWINGS occupied by abaffle 120 which supplies airbled from the flow
0026. The invention will be better understood with refer
path for the secondary flow, a tubular fuel injector 130, and a
ence to the appended drawings, in which: protective heat shield 110. The shield 110 is in the form of a
curved metal sheet whose concave side faces in the down
0027 FIG. 1 represents a perspective view of an after stream direction.
burner case with flame holders; 0039. The air supply baffle 120, the tubular fuel injector
0028 FIG. 2 represents a sectional view of part of a tur 130 and the protective heat shield 110 are held in the arm 100,
bofan engine with a flame holder according to a first prior art; at the top, in the afterburner case and, at the bottom, by a
0029 FIG.3 represents a sectional view of the lower part spacer shoe 150 whose function is to prevent them from
of a flame holder according to a second prior art; coming into contact, in particular during vibratory operation.
0030 FIG. 4 represents a sectional view of a flame holder The shoe 150 makes it possible to fasten the air supply baffle
according to the invention; 120 and the injector 130 in the arm 100 without the need for
0031 FIG. 5 represents a sectional view of the flame piercings in thermally stressed regions of both the shield 110
holder in FIG. 4 in the direction II-II; and the arm 100, thus making it possible to limit wear.
0032 FIG. 6 represents a perspective view of a spacer shoe 0040. In this example, the arm 100 and the tubular fuel
according to the invention; injector 130 are directly fastened in the afterburner case.
0033 FIG. 7 represents a perspective view of the shoe in 0041. With reference to FIG. 6, the spacer shoe 150 sub
FIG. 6, retaining an air supply baffle: stantially takes the form of a Y comprising a central branch
0034 FIG. 8A represents a partial perspective view of the 150c, extending lengthwise in a directionX, from which there
shoe and the baffle in FIG. 7, which are mounted in a flame extend two substantially parallel lateral branches 150a, 150b.
holder; and Each lateral branch 150a, 150b, extending in the direction X,
0035 FIG.8B is a close-up view of FIG. 8A representing is terminated at its end by a circular spacer lug. 151a, 151b
the connection, produced by the shoe, between a flame holder each comprising a fastening orifice 152a, 152b formed in the
arm and its protective heat shield. lateral branch 150a, 150b in a direction Y orthogonal to the
direction X.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
0042. The lateral branches 150a, 150b have a small thick
ness So as to make it possible to overcome differential expan
0036 FIG. 2 represents part of a turbofan engine. All that Sions between the arm 100 made of CMC and the shoe 150
can be seen of this engine is the ogive shape of the exhaust made of metal. This equally applies to an arm made of a metal
case 3 at the rear of the gas turbine engine, inside the outer material, with differential expansions occurring due to tem
cylindrical casing 4. The engine Supplies a hot primary gas perature differences between the metal components.
flow, represented by the arrow P. at the outlet of the turbine of 0043. The central branch 150c of the spacer shoe 150,
the gasturbine engine. Some of the air Sucked in by the engine which is wider than the lateral branches 150a, 150b, is pierced
is simply compressed and bypasses the combustion chamber at two locations within its thickness in a direction Z. A first
of the engine. This air constitutes the secondary flow, repre retaining through orifice 154 is formed at the base of the
sented by the arrow S. The two flows here mix downstream of central branch 150c and is intended to retain an axial portion
a confluence section formed by an annular metal sheet. of the air supply baffle 120. This orifice will be designated
0037. This engine section is extended, particularly in mili hereinafter as baffle retention orifice 154. A second retaining
tary-type aircraft, by a cylindrical afterburner duct 1 for through orifice 156 is formed in the central branch 150c,
reheating the gases that is situated ahead of the exhaust between the baffle retention orifice 154 and the lateral
nozzle. The upstream part of the afterburner duct 1 is shown, branches 150a, 150b. This orifice156 is intended to center the
but not the nozzle. In certain flight phases, it is necessary to tubular fuel injector 130 in the arm 100. This orifice will be
Supply additional energy to the gases producing the thrust. designated hereinafter as injector centering orifice 156.
This is provided by reheating, or afterburning, the gases in the 0044) Still with reference to FIG. 6, the spacer shoe 150
afterburner duct. Fuel is injected into the gases by injectors also comprises locking through orifices 155 formed within
like those represented at 7, radially passing through the two, the width of the central branch 150c in the direction Y,
primary and secondary, flow paths. Downstream of these orthogonally to the baffle retention orifice 154. Thus, with
injectors, means forming flame holders 10 are configured so reference now to FIG. 7, when the air supply baffle 120 is
as to allow the gases to be retained during their combustion. introduced into the spacer shoe 150 via its baffle retention
These means comprise partly rectilinear flame holders 10 orifice154, the outer surface of the baffle 120 is visible via the
arranged radially in a star pattern in a plane Substantially locking orifices 155, the function of which will be described
perpendicular to the engine axis, in this case immediately in detail hereinafter.
downstream of the confluence of the two primary and sec 0045. The invention will be understood better still from
ondary flows. They are connected by arms 9 in the form of a the description of the mounting of the spacer shoe 150 in the
ring sector which, in this type of afterburner device, are on the arm 100, as represented in FIGS. 4, 5, 7, 8a and 8b.
secondary flow path side. 0046) With reference to FIG. 4, the air supply baffle 120
0038. With reference to FIG.4, the radial flame holders 10 and the tubular fuel injector 130 are centered, at the top, in the
are formed by radial arms 100 in the form of gutters, with a V flame holder 10 and held, at the bottom, by the spacer shoe
or U-shaped cross section, whose apex faces in the upstream 150. In this example, the air baffle 120 comprises, at the top,
direction with respect to the gas flow direction. The structure a swiveling head enabling it to be centered in the arm. The air
of the flame holder 10 is visible from the sectional view in supply baffle 120 is introduced axially, in the direction Z. into
US 2009/0260366 A1 Oct. 22, 2009

the spacer shoe 150 via its baffle retention orifice 154 and is mounting is also valid for mounting a protective heat shield in
locked axially with the shoe 150 by welding. During the a flame holder in the form of a ring sector Such as those
welding step, material is applied to the outer Surface of the connecting the radial arms.
baffle 120, which is visible via the locking orifices 155. The
air baffle 120 is then fixedly retained by the shoe 150, as 1. A flame holder for an afterburner duct of a jet engine,
represented in FIG. 7. comprising an arm in the form of a gutter forming a cavity, a
0047. The tubular fuel injector 130 is, for its part, intro shield for protecting the cavity of the arm from heat, and an air
duced axially in the direction Z into the injector centering supply baffle housed in the cavity, wherein the arm, the pro
orifice 156 in order to maintain it at a distance from the air tective shield and the air supply baffle are held together by a
supply baffle 120. The distance between the baffle 120 and the one-piece spacer shoe comprising at least one spacer lug
injector can be set by adapting the spacing between the injec designed to form a gap between the protective heat shield and
tor centering orifice 156 and the baffle retention orifice 154 of at least one wall of the arm.
the shoe 150. 2. The flame holder as claimed in claim 1, wherein the shoe
0.048. During the mounting operation, the circular gap comprises a means for retaining the baffle.
producing lugs 151a, 151b of the spacer shoe 150 are 3. The flame holder as claimed in claim 1, wherein a fuel
arranged between the walls of the protective shield 110 and injector is placed inside said cavity of the arm.
the walls of the arm 100. With reference to FIG. 5, the lug 4. The flame holder as claimed in claim3, wherein the shoe
151a is interposed between the wall 111a of the protective comprises a means for centering the injector.
shield 110 and the wall 101a of the arm 100, the thickness of
the lug. 151a defining a gap thickness (e) between said walls 5. The flame holder as claimed in claim 4, wherein the shoe
101a, 111a. The gap (e) forms a channel allowing carbureted comprises a means for retaining the baffle.
air to pass through. 6. The flame holder as claimed in claim 1, wherein the shoe
0049. For each spacer lug of the shoe 150, a cylindrical is welded to the air supply baffle.
stud 160 successively passes through the wall 111a of the 7. The flame holder as claimed in claim 1, wherein the shoe
shield 110, the fastening orifice 152a of the lug, and the wall takes the form of aY defining a central branch and two lateral
101a of the arm 100. The stud 160 is retained by a washer 161 branches, the central branch comprising a through orifice for
welded to the outside of the arm 100. The assembly formed by retaining the baffle.
the wall 101a of the arm 100, the wall 111a of the shield 110 8. The flame holder as claimed in claim 7, wherein a fuel
and the lug. 151a is held clamped between the welded washer injection is placed inside said cavity of the arm, the central
161 and the head 162 of the cylindrical stud. branch comprising a through orifice for centering the injector.
0050. It goes without saying that other fastening means 9. A jet engine afterburner duct comprising at least one
could also be suitable, such as those described in application flame holder as claimed in claim 1.
FRO655241. 10. Ajet engine comprising an afterburner duct as claimed
0051 What has been described is the mounting of a pro in claim 9.
tective heat shield on a flame holder of rectilinear shape. The
invention is not limited to this application. This type of