Fuel distribution device

The invention concerns a fuel distribution device in a high velocity gase flow. The device consists of two coaxial, toric injection manifolds placed in close proximity with respect to each other, pierced by small diameter uniformly distributed orifices and arranged to introduce fuel into the flow. The orifices in the manifold located downstream with respect to the direction of the flow of gases, are arranged on the face turned upstream of the manifold, in a circular row coaxial with it. It is the object of the invention to reduce the drag induced in the flow by the devices presently in use, while improving the distribution of the fuel; it finds particularly advantageous applications in the afterburner ducts of gas turbine engines.

BACKGROUND OF THE INVENTION 
The present invention concerns a device to distribute fuel in a high 
velocity gaseous flow, for use particularly in the afterburner duct of a 
turbojet engine. 
Afterburner devices provided on turbojet engines are for the purpose of 
increasing the thrust of the turbojet engines by burning additional fuel 
after the passage of gases through the turbine. This combustion generally 
takes place in a duct of generally cylindrical form, in which one or more 
fuel injection and distribution devices are located, having annular 
shapes, followed in the downstream direction by one or several flame 
stabilizes, also of an annular shape. The fuel injected generally by means 
of toric manifolds with orifices for the introduction of the fuel into the 
flow. Hereinafter, a torus will be defined as a volume generated by a 
surface rotating around an axis located in the plane of the surface but 
not cutting it. The distribution of the fuel is effected by obstacles, or 
anvils, located in front of orifices drilled into manifolds. Flame 
stabilizers consist of generally "V" shaped annular elements located 
downstream of the injection manifolds. Particular attention must be paid 
to the concept and the disposition of the different elements in the duct 
in order to obtain homogeneous distribution and the finest possible 
atomization of the fuel,while reducing to a minimum the loss of pressure 
caused in the jet. The latter condition is especially critical in the case 
of flow at high Mach numbers such as encountered in the afterburner ducts 
of the propulsion units of supersonic aircraft. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a system for the injection and 
distribution of fuel, or a distributor device, which satisfies the above 
conditions. 
According to the invention, every toric fuel injection manifold used in the 
conventional system is replaced by two toric manifolds coaxial with the 
jet, having essentially identical right cross section, each smaller than 
that of a single manifold, located adjacent to each other, the diameter of 
the toric annulus constituting each manifold being of the order of the 
diameter of the single manifold. If the flow channel is not cylindrical, 
but of the shape of a truncated cone, the median radius of the two 
manifolds will preferentially "follow" the profile of the channel, i.e. 
the ratio of the median radius of a torus and the radius of the channel in 
the same transverse plane will remain constant. It should be understood 
that the entirety of the two manifolds will be able to produce the same 
maximum flow rate as the single manifold. 
The division of the single manifold into two parts as described hereinabove 
results in a reduction of the loss of pressure in the flow because of the 
reduced maximum cross section of the injection system. The division into 
two manifolds also has the advantage of easier control of the flow rate by 
providing for separate regulation of the fuel supply to the two manifolds. 
The fuel supply to the two ramps may also be effect at diametrically 
opposed points, which favors a more homogeneous distribution of the fuel 
in the channel. Fuel is injected into the channel by means of orifices 
drilled into the two manifolds. 
According to the invention, the orifices of the manifold for the injection 
of fuel located downstream with respect to the direction of the flow of 
the gases are distributed uniformly on a circle coaxial with said 
manifold. The axis of each of the orifices is located in an axial plane of 
the channel and intercepts the torus located upstream without intersecting 
the portion of the axis common to both tori situated between the 
transverse planes in which said tori are located. This arrangement makes 
it possible to inject the fuel supplied to the downstream manifold with a 
large velocity component in the direction opposed to that of the flow of 
gases. Additionally, in the absence of other devices, the fuel injected by 
the downstream manifold will strike the upstream manifold thus assuring 
its distribution in the channels; the fuel jets thus being dispersed 
toward the inside and the outside of the tori. It should be noted that the 
distribution of the fuel between the inside and the outside of the tori 
may be modulated by providing a suitable orientation of the axes of the 
injection orifices. 
Concerning the manifold located upstream, various modes of embodiment are 
envisioned, according to the disposition of the injection orifices drilled 
into said manifold, according to the relative position of the said 
orifices with respect to the orifices of the downstream manifold and 
according to the design of the fuel distribution devices or anvils. 
In a first variant of embodiment the injection orifices drilled in the 
manifold located upstream are distributed uniformly throughout an annular 
row, coaxial with the manifold and on the face of said manifold turned 
into the upstream direction. The axis of each of said orifices is located 
in an axial plane of the channel and its orientation is such that the 
component parallel to the axis of the flow of the velocity of the fuel 
injected is greater than its transverse component; the fuel thus injected 
therefore has a large velocity component in the direction opposed to that 
of the flow of the gases. To insure the homogenous distribution of the 
fuel, an anvil is placed upstream of the manifold so as to intercept the 
jets of fuel issuing from said manifold. The anvil consists of an annular 
element coaxial with the manifold, having a median diameter identical with 
that of the upstream manifold and a maximum radial dimension of its right 
cross section at the most equal to the maximum radial dimension of the 
right cross section of the torus, and a concavity facing the injection 
orifices. 
In a second variant, the orifices of the manifold located upstream are 
uniformly distributed in an annular row over the downstream face of said 
manifold. The axis of each of these orifices is contained in axial plane 
of the channel and intercepts the upstream torus without intersecting the 
common axis of the tori between the transverse planes containing the tori. 
The planes containing the axes of the orifices of the two tori are 
interposed between them; in this manner alternating locations of the 
orifices of each manifold are obtained. To assure the distribution of the 
fuel issuing from the two rows of orifices, a single annular element 
assuming the role of an anvil is interposed between the two manifolds so 
as to intercept the jets of fuel issuing from said manifolds. This anvil 
is coaxial with the channel, its median radius being proportional to the 
radius of the channel in its own plane in the same ratio as the median 
radii of the manifolds are proportional to the radius of the channel in 
their plane. The maximum radial dimension of the right section of the 
anvil is of the same order of magnitude as that of the tori. Various 
configurations may be considered for this element, such as a common 
annular type, flat ring, annulus with an "I" cross section or an annulus 
presenting a concavity facing each manifold. The latter arrangement makes 
it possible to influence the distribution of the fuel between the outside 
and the inside of the tori by providing evolutive radii of curvature for 
the concavities; it will be recalled that another means of affecting said 
distribution is the orientation of the orifices drilled into the 
manifolds. 
In a third variant each of the manifolds carries an anvil consisting of an 
annular part coaxial and integral with it. The arrangement of the 
injection orifices is identical with that of the preceding variant. The 
anvil is form by a flat ring coaxial with the manifold and a diameter 
identical with that of said manifold; the radial width of the ring is 
approximately equal to the maximum radial dimension of the right cross 
section of the torus carrying it. Holes are provided in the ring opposite 
the injection orifices of the manifold to which the ring is fastened. The 
ring that is integral with one manifold plays the role of anvil for the 
orifices of the opposing manifold. The effective portion of the anvil is 
limited to the regions effectively stricken by the jets of the fuel. It is 
thus possible to retain only these regions and interrupt the rings in 
between. The anvil may thus consist, as a variant, of a series of 
elemental anvils proper to each orifice and forming a succession of 
annular segments arranged between the injection orifices of each manifold. 
In a fourth mode of embodiment the injection orifices of the upstream 
manifold are distributed in an annular row on the face of said manifold 
turned into the downstream direction. In contrast to the last two variants 
described, the axis of each of the orifices is located in an axial plane 
containing the axis of one orifice the downstream manifold, the axes of 
the two types of orifices are thus mingled or secant in this plane. In 
this case, the fuel is dispersed by means of the interactio-between the 
jets of fuel issuing from the two manifolds; in this manner, "fluid 
anvils" are produced. This arrangement, however, reduces the possibility 
of regulating the flow of the two manifolds, if good dispersion is to be 
achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the figures the section of the tori was chosen to be circular fo 
convenience of representation, it should be understood, however, that 
other shapes may be employed, for example, oblong. For the same reason, 
the tori are shown with identical diameters. 
The gas turbine engine shownin FIG. 1 comprises from upstream to downstream 
one or more compressor stages 1, a combustion device 2, one or more 
turbines 3, and an afterburner duct 4, in which the gases flow in the 
direction indicated by the arrow f, preceding the jet nozzle 5. In the 
afterburner duct 4, fuel distribution devices and flame stabilizing 
devices are placed. One of each of these devices is shown. The fuel 
distribution device is formed by a toric manifold 6 pierced by orifices 
which issue jets of fuel upstream with respect to the direction of the 
flow of gases in the example chosen, and an annular obstacle or anvil 7 
placed upstream of the manifold 6, which intercepts the jets of fuel in 
order to disperse them. The flame stabilizing device 7' is located 
downstream from the fuel distributing device and consists of a gutter with 
a "V" section. 
For high afterburning rates, the fuel flow required in the duct 4 makes it 
necessary to use manifolds with large cross section, which leads to an 
increase in the loss of pressure in said duct. In addition, it is 
difficult to vary the flow of fuel within a large range without affecting 
the quality of its atomization. 
According to the invention, the conventional one manifold with a large 
transverse cross section is replaced by two manifolds placed closely 
adjacent to each other, having essentially identical cross sections but 
with reduced transverse cross section. FIG. 2 shows diagrammatically a 
first form of embodiment of the fuel distribution device according to the 
invention to semi-section in an axial plane of the channel. The flame 
stabilizing devices are omitted. The distribution system of the invention 
consists of two tori 8, 9, coaxial with the duct 4 and supplied separately 
with fuel, and an anvil 10 located upstream from the torus 8. The torus 9 
is pierced by the orifices 11, distributed uniformly in an annular row 
over the upstream face of said torus, the axis of each of the orifices 
being in a plane containing the common axis X'X of the two tori and 
intercepting the torus 8 without intersecting said axis. The fuel supplied 
to the torus 9 is thus introduced in the channel in the form of jets which 
strike the downstream face of the torus 8, which thus plays the role of an 
anvil. The positions and orientations chosen for the orifices 11 may 
differ from those shown, in view of what had been said hereinabove. The 
torus 8 is pierced by orifices 12, uniformly distributed in an annular row 
on the face of said torus turned upstream. The axis of each of the 
orifices 12 intercepts the anvil 10 and is located in an axial plane of 
the channel. The fuel jets thus injected impinge upon the anvil 10 which 
disperses them in the channel. The anvil 10 is formed by an annular 
element with an average diameter equal to that of the tori, having a right 
section with a maximum radial height equal to the maximum radial dimension 
of the tori and displaying a concavity turned toward the orifices 12. The 
radius of curvature of said concavity may be evolutive to affect the 
distribution of fuel between the inside and the outside of the element 10. 
The median radii R8, R9, R10 of the manifolds 8, 9 and of the anvil 10, 
respectively, are in a constant proportional relationship with the radius 
of the channel in the plane in which they are measured. This enables the 
distribution system of the invention to follow the profile of the channel. 
FIG. 3 represents a fuel distribution system according to the invention 
conforming to the second variant of embodiment. The distribution system 
comprises two coaxial tori 13 and 14, with essentially equal cross 
sections and diameters and an anvil 15 interposed between said tori. The 
anvil 15 here is formed by a planar ring. The torus 13, located 
downstreams, is pierced on its face turned in the upstream direction by 
orifices 16 uniformly distributed in an annular row coaxial with it. The 
axis of each of the orifices 16 is located in an axial plane of the 
channel and intercepts the torus 14 without cutting the portion of the 
axis X'X common to both tori, between the transverse planes containing the 
tori. The torus 14 is pierced on its face turned in the downstream 
direction by orifices 17, uniformly distributed over an annular row 
coaxial with it. The axis of each of the orifices 17 is located in an 
axial plane of the channel interposed between two planes containing the 
axes of the orifices 16 and intercepting the anvil 15. This arrangement 
enables the fuel issuing from the orifices 16 and 17 to retain substantial 
velocity components parallel to the flow. The fuel jets issuing from the 
orifices 16 and 17 impinge the anvil 5, which disperses them. 
FIG. 4 is analogous to the preceding figure, only the anvil 15 being 
modified. It consists of a planar ring 18 coaxial with the channel, two 
ferrules 19, 20 being fastened to the external and internal periphery of 
said ring and the assembly thus displaying an "I" shaped cross section, in 
an axial plane. 
FIG. 5 which is analogous to the two preceding figures, shows another form 
of the anvil. The latter here consists of an annular element 21 coaxial 
with the channel and presenting a concavity to face the injection orifices 
of each tori. The curvature of the concave faces is determined so as to 
obtain a suitable distribution of the fuel between the outside and the 
inside of the anvil. 
In a general fashion, the median diameters of the anvils 15, 18 and 21 of 
FIG. 3, 4 and 5, respectively, and the median diameters of the manifolds 
13 and 14, maintain a constant proportional relationship with the diameter 
of the channel at the location where they are measured, so as to follow 
the profile of the channel. The maximum radial height of the right section 
of each of the anvils 15, 18 and 21 is of the order of magnitude of those 
of the tori 13 and 14. 
FIG. 6 corresponds to the third variant of embodiment of a distribution 
device according to the invention. The two manifolds 13 and 14 into which 
the orifices 16 and 17 are pierced, each carry an annular element 22, 23 
consisting of a ring having a "U" shaped cross section in an axial plane, 
with its cohcavity turned toward the manifold to which it is secured and 
presenting a flat surface facing the opposite manifold. Orifices such as 
24 are pierced into each ring at the height of the orifices of injection 
of the manifold to which it is fastened. The height of the flat surface of 
each ring measured in the radial direction is of the order of magnitude of 
the maximum radial dimension of the torus which carries it. It should be 
noted that the effective part of each anvil is limited to the area 
impacted by the fuel. It is, therefore, possible to eliminate the 
inoperative parts of the ring and to design for each orifice of the 
manifold a particular anvil located between the orifices of the opposite 
manifold, each of these elemental anvils representing a segment of a ring, 
such as 22 or 23. 
It is also possible to employ a fourth variant (not shown) is which the 
injection holes of the two tori are not offset angularly, but face each 
other. In this case, the anvil may be eliminated. A type of fluid anvil is 
thus created. 
The distribution device of the invention, in addition to reducing the 
obstruction of the channel to which it belongs produces an appreciable 
improvement of the distribution and homogenization of the fuel in the 
flow. It also serves to extend the range of fuel flow variation.