U.S. patent application number 10/872510 was filed with the patent office on 2005-12-15 for ventilation channels in an afterburner chamber confluence sheet.
This patent application is currently assigned to SNECMA MOTEURS. Invention is credited to Baboeuf, Sebastien, Cortes, Thierry, Page, Alain, Roche, Jacques.
Application Number | 20050274114 10/872510 |
Document ID | / |
Family ID | 33396844 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050274114 |
Kind Code |
A1 |
Cortes, Thierry ; et
al. |
December 15, 2005 |
VENTILATION CHANNELS IN AN AFTERBURNER CHAMBER CONFLUENCE SHEET
Abstract
The invention relates to ventilating the confluence sheet of an
afterburner chamber of an aviation turbomachine, including,
upstream from the afterburner chamber: a diffuser defined by a
confluence sheet disposed inside a casing, said casing and said
confluence sheet defining between them an annular channel for a
cold secondary flow, upstream fuel injectors being disposed at the
inlet to said diffuser and flame-catchers being disposed downstream
from said upstream injectors, said confluence sheet presenting,
between the radial plane containing said upstream injectors and the
radial plane situated at the rear ends of said flame-catchers two
bends so as to flare downstream in order to slow down the primary
flow F1 downstream from said upstream injectors. An annular scoop
is provided around the upstream portion of said confluence sheet in
order to extract a flow of air from the cold flow, said extracted
flow being injected tangentially into the primary flow via a
plurality of channels formed in the wall of said confluence sheet
between the scoop and said diffuser.
Inventors: |
Cortes, Thierry; (Brunoy,
FR) ; Page, Alain; (Montgeron, FR) ; Baboeuf,
Sebastien; (Avon, FR) ; Roche, Jacques;
(Lisses, FR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SNECMA MOTEURS
PARIS
FR
|
Family ID: |
33396844 |
Appl. No.: |
10/872510 |
Filed: |
June 22, 2004 |
Current U.S.
Class: |
60/761 |
Current CPC
Class: |
F02K 3/10 20130101; F02K
1/386 20130101; Y02T 50/675 20130101; Y02T 50/60 20130101; F02K
1/822 20130101 |
Class at
Publication: |
060/761 |
International
Class: |
F02K 003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 25, 2003 |
FR |
03 07657 |
Claims
What is claimed is:
1. An aviation turbomachine including, upstream from a afterburner
chamber: a diffuser defined by a confluence sheet disposed inside a
casing, said casing and said confluence sheet defining between them
an annular channel for conveying a cold secondary flow, upstream
fuel injectors being disposed at the inlet to said diffuser and
flame-catchers being disposed downstream from said upstream
injectors, said confluence sheet presenting, between the radial
plane containing said upstream injectors and the radial plane
situated at the rear ends of said flame-catchers, two bends so as
to flare downstream in order to slow down the primary flow F1
downstream from said upstream injectors, wherein an annular scoop
is provided around the upstream portion of said confluence sheet in
order to extract a flow of air from the cold flow, this extracted
flow of air being injected tangentially into the primary flow via a
plurality of channels formed in the wall of said confluence sheet
between the scoop and said diffuser.
2. A turbomachine according to claim 1, wherein the channels
opening out circumferentially into the wakes from the injectors are
of section that is considerably greater than the section of the
other channels.
3. A turbomachine according to claim 2, wherein the scoop is
defined on the inside by a shell surrounding the upstream section
of the diffuser, and on the outside by the upstream portion of a
sheet which, downstream from the shell forms the middle zone and
the downstream zone of the confluence sheet, which zones are cooled
by the flow of air injected via the channels.
4. A turbomachine according to claim 3, wherein the shell and the
upstream portion present downstream junction zones, and the
channels are formed at the interface of said junction zones.
5. A turbomachine according to claim 4, wherein the channels are
formed in the outside face of the shell.
Description
FIELD OF THE INVENTION
[0001] The invention relates to aviation turbomachines, in
particular for military use, and that include afterburner chambers
presenting an upstream diffuser.
[0002] More precisely, the invention relates to an aviation bypass
turbomachine having an afterburner chamber and including, upstream
from said afterburner chamber: a diffuser defined by a confluence
sheet placed inside a casing, said casing and said confluence sheet
defining between them an annular channel for a cold secondary flow,
upstream fuel injectors being disposed at the inlet to said
diffuser, and flame-catchers being disposed downstream from said
injectors, the confluence sheet presenting, in the radial plane
containing said injectors and the radial plane containing the
flame-catchers, two bends so as to flare downstream in order to
slow down the primary flow downstream from said injectors.
BACKGROUND OF THE INVENTION
[0003] That type of turbomachine including a short diffuser between
the injectors and the flame-catchers is characterized by a small
bypass ratio seen from the rear body. The secondary flow serves in
particular to cool the parts situated downstream from the injectors
and must be used effectively for this purpose.
[0004] Conversely, the primary flow coming from the low pressure
turbine is flowing at a high rate. It is on this flow that the
performance of the engine relies for the most part. Consequently,
it must be subjected to a minimum amount of head losses and must be
as uniform as possible in temperature and speed. For this purpose,
the afterburner chamber diffuser constituted by the confluence
sheet serves to slow down the primary flow upstream from the
flame-catchers and to channel it so that, downstream, it occupies
the entire volume of the afterburner chamber. This function, which
is known as a "diffusion" function since it is accompanied by an
increase in static pressure, needs to take place without unwanted
turbulence forming along the stream, since such turbulence or
backflow leads to losses that can cause the fuel coming from the
upstream injectors to self-ignite.
[0005] In afterburner chambers having a large dilution ratio, the
primary flow and a portion of the secondary flow meet and mix.
Conversely, when the dilution ratio is small, the fraction of the
secondary flow available for mixing at the downstream end of the
confluence sheet is small once all of the flows needed for
ventilation have been taken off. The confluence sheet therefore
needs to be flared so that the primary flow occupies the full
extent of the afterburner chamber. If the sheet is not properly
shaped, backflow occurs in the vicinity of the confluence sheet
between the plane of the injectors and the plane of the
flame-catchers. This backflow is particularly encouraged when the
amount of gyration at the outlet form the low pressure turbine is
large.
[0006] A risk of backflow thus appears in the vicinity of a highly
diffusing confluence sheet associated with a large amount of
gyration in the primary flow. This backflow is predicted by
numerical 3D simulation of the flow. It appears in the primary flow
at the concave bend of the confluence sheet, where the sheet
provides an indentation suitable for a pocket of backflow.
[0007] Furthermore, at the junction between the convex bend portion
and the concave bend portion of the confluence sheet temperature
and temperature gradients are excessive. Steep temperature
gradients are due to the convection of the cold secondary flow
which blows against the outside surface of the sheet and the hot
primary flow which blows against its inside surface.
[0008] In order to eliminate turbulence, it would naturally be
possible to modify the shape of the confluence sheet by lengthening
the diffuser axially, but that solution increases the size of the
engine.
OBJECTS AND SUMMARY OF THE INVENTION
[0009] An object of the invention is to decrease the risk of
backflow and the temperature gradients without changing the shape
and the length of the diffuser.
[0010] According to the invention, this object is achieved by the
fact that an annular scoop is provided around the upstream portion
of said confluence sheet in order to extract a flow of air from the
cold flow, this extracted flow of air being injected tangentially
into the primary flow via a plurality of channels formed in the
wall of the confluence sheet between the scoop and said
diffuser.
[0011] These channels serve firstly to cool the confluence sheet by
convection, and secondly to create a film of cooling air along the
confluence sheet where it is subjected to radiation from the flame
in the afterburner chamber. This reduces the temperature of the
structure, and also leads to a reduction in the infrared signature
of the solid portions at the end of the chamber. The axial flow of
cooling air along the wall of the confluence sheet also makes it
possible to expel the flow disturbance from this zone.
[0012] Preferably, the channels that open out circumferentially in
the wake of the injectors are of a section that is significantly
greater than that of the other channels.
[0013] The greater flow of air coming from these wider channels
serves to blow away the backflow.
[0014] Advantageously, the scoop is defined on the inside by a
shell surrounding the upstream section of the diffuser, and on the
outside by the upstream portion of a sheet which, downstream of the
shell, forms the middle zone and the downstream zone of the
confluence sheet that are cooled by the flow of air injected via
the channels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other advantages and characteristics of the invention will
appear on reading the following description made by way of example
and with reference to the accompanying drawings, in which:
[0016] FIG. 1 is a half-section on a plane containing the axis of
symmetry of the upstream portion of the rear body of an aviation
turbomachine of the invention fitted with a diffuser upstream from
a post-combustion chamber; and
[0017] FIG. 2 is a perspective view of the inside shell defining
the upstream section of the diffuser.
MORE DETAILED DESCRIPTION
[0018] In FIG. 1, reference 1 designates the upstream portion of
the rear body of an aviation turbomachine of axis X, presenting a
diffuser 2 downstream from the low pressure turbine and upstream
from an afterburner chamber.
[0019] The diffuser 2 is defined by a confluence sheet 3 situated
radially inside a casing 4, the casing 4 and the confluence sheet 3
defining between them an annular channel 5 in which there flows a
cold secondary flow F2.
[0020] At the upstream end of the diffuser 2 there are mounted
radial fuel injectors 6 referred to as "upstream" injectors, which,
when operating in afterburner mode, deliver a flow of fuel into the
primary hot flow F1 penetrating into the diffuser 2. In a plane
perpendicular to the axis X and situated upstream from the upstream
injectors 6, there are radial flame-catchers 7 that are disposed in
circumferential alternation with the upstream injectors 6 on
meridian planes. These flame-catchers 7 are also fitted with fuel
injectors 8 referred to as "downstream" injectors. Reference 9
designates an annular flame-catcher that is circularly symmetrical
about the axis X and disposed at the end of the radial
flame-catchers 7.
[0021] As can be seen clearly in FIG. 1, the confluence sheet 3
flares strongly in a downstream direction between the region of the
upstream injectors 6 and the rear portions of the flame-catchers 7,
so that the speed of the gas in the primary flow F1 is reduced at
the flame-catchers 7. The confluence sheet 3 presents two bends
seen from inside the diffuser 2 relative to the axis X,
specifically a convex bend in the upstream region and a concave
bend in the downstream region.
[0022] The object of the invention is to ensure that the confluence
sheet 3 is cooled energetically in its middle zone and in its
downstream zone, which zones are subjected in operation to the high
temperatures that exist within the diffuser 2 and along which
backflow can occur, thereby generating intense heat fluxes.
[0023] In the invention, these middle and downstream zones are
cooled by a flow of air F3 taken from the secondary flow F2 by
means of a scoop 11 surrounding the upstream inside extension 10a
of the confluence sheet 3 in register with and downstream from the
upstream injectors 6, which flow is injected tangentially to the
inside face of said sheet 3 into the primary flow F1 via channels
12 formed in the wall of the confluence sheet between the inside of
the scoop 11 and the diffuser 2.
[0024] Advantageously, the scoop 11 is defined on the inside by a
shell 10a surrounding the upstream section of the diffuser 2, and
on the outside by the upstream portion 13 of a sheet which,
downstream from the shell 10a, forms the middle zone and the
downstream zone of the confluence sheet 3, which zones are cooled
by the flow of air F3 injected via the channels 12. This upstream
portion 13 has orifices with ventilation tubes 17 passing through
them with clearance to project the upstream injectors 6 so as to
enable a portion of the cold secondary flow F2 to be introduced
into the scoop 11. The shell 10a and the upstream portion 13
present at their downstream end axial junction zones 14a and 14b
with the channels 12 being arranged at the interface between
them.
[0025] FIG. 2 shows the shell 10a. The channels 12 are formed in
the outside face of the downstream portion 14a of the shell.
Reference 15 designates an orifice through which there passes a
ventilation tube 17 for an upstream injector 6. It can be seen in
this figure that the channels 12 are formed by axial grooves and
that they are distributed in two groups.
[0026] In the wake of the upstream injectors 6, there are provided
grooves 16 of considerable width which enable a large flow of
ventilation air to be brought into the diffuser 2 so as to blow
away any backflow that might start downstream from the upstream
injectors 6.
[0027] Outside the wakes from the upstream injectors, the channels
12 serve essentially for cooling the walls of the confluence sheet
3 in this zone by convection and for forming a cooling film on the
inside wall of said sheet 3 downstream from said zone. They are of
small section.
[0028] These channels 12 and the grooves 16 are made by machining
the junction zone 14a of the shell 10a prior to fixing it to the
junction zone 14b of the confluence sheet 3.
[0029] The channels 12 enable the wall of the confluence sheet 3
and the shell 10 to be cooled energetically in the zones that are
subjected to high temperatures.
* * * * *