Note: Descriptions are shown in the official language in which they were submitted.
- ~7~i~'7~7
1 - 13DV~7453
FUEL NO Z ZLE FOR A GAS
TURB I NE ENGI NE
: BACKG~OUND OF THE INVENTION
.
The present invention relates to a fuel nozzle for a
gas turbine enginet and more particularly, to such a nozzle
which exhibits reduced carbon formation without requiring
an air shroud.
In a conventional gas turbine engine, a combustor
section is utilized to provide a zone in which fuel and
compressor discharge air may be burned with the resultant
energy release employed to drive other operating parts of
the engine. The combustor includes at least one fuel nozzle
located therein for supplying fuel to the combustor section.
One conventional type of fuel nozzle is often referred to
as a fuel pressure atomizing nozzle indicating that fuel
pressure is utilized to provide an atomized fuel flow from
an orifice in the output tip portion of the nozzle into
the combustor for desirable combustor operation.
To provide desirable engine starting performance, it
is often necessary to provide a dual fuel flowpath, i.e.,
primary and secondary paths, from the Puel nozzle to the
combustor. Although such dual flowpath nozz~les are satisfactory
for many applications, it is known that conventional dual
path nozzles are likely to develop undesirable carbon deposits
on the nozzle surfaces adjacent to the output portion thereof.
Accordingly, a present solution to the formation of such
undesirable carbon deposits is to provide the nozzle with
an air shroud structure which encircles the output portion
of the nozzle. The air shroud functions to direct airflow
;~
7~ 7
13DV-7453
-- 2
entering the combustor section from the compressor section
through a sweeping motion which tends to reduce the formation
of the undesirable carbon deposits. A problem with this
solution, however, is that additional struc-ture, i.e., an
air shroud, i5 required. The air shroud adds weight and
cost to the nozzle assembly. This added weight is particularly
undesirable as it is well known that reduced nozzle tip
we'`ght results in improved vibratory patterns, e.g., reduced
tip mass reduces the possibility of resonance in the
fundamental bending frequency, and hence, improved part life.
In addition, for many applications, additional swirler and
venturi components are provided at the output of the nozzle
for improving the fuel and air mixing in the primary zone
of the combustor. Typically, such swirler and venturi
components are circumferentially disposed around the output
portion of the fuel nozzle. When such swirler and venturi
components are employed in combination with the conventional
; fuel nozzle having an air shroud, the result is an undesirably
large outer diameter structure.
Accordingly, it is a general object of the present
invention to provide an improved fuel nozzle for a gas turbine
engine.
It is another object of the present invention to provide
such a fuel nozzle which exhibits reduced carbon formation
without requiring an air shroud.
It is another object of the present invention to provide
such a fuel no2zle which is relatively simple to manufacture.
It is another object of the present invention to provide
such a fuel nozzle which can be conveniently inserted in-to
and removed from its operating position in -the combustor
section.
It is another object of the present invention to provide
such a fuel nozzle with improved operational life.
~'7~'7~7
13DV-7453
-- 3 --
SUMMARY OF THE IN~ENTION
In one form of our invention, we provide a dual fuel
path fuel nozzle for use in a combustor section of a gas
turbine engine. The nozzle includes primary path means
with a central longitudinal axis. The primary path means
has an input end for receiving a primary ~low of fuel and
an opposing output end for developing a primary output
flow having a predetermined rotational motion at the output
end. The nozzle includes secondary path means having an
input end for receiving a secondary flow of fuel and an
1~ opposing output end for developing a secondary output flow.
The secondary output flow has a rotational motion which
generally corresponds in direction to -the predetermined
rotational motion of the primary output flow. The secondary
path means is circumferentially disposed in fixed relation
around the primary path means with the secondary path means
output end being circumferentially disposed around the
primary path means output end, thereby forming an interacting
nozzle output flow. Nozzle discharge means is circumferentially
disposed around the primary and secondary path means ou-tput
2Q ends for receiviny the interacting output flow and developing
; a processed nozzle output therefrom for use in subsequent
ignition in the combustor section. The nozzle discharge
means includes a conical portion ~aving an input end of
relatively smaller diameter which increases along the central
longitudinal axis to an output end of relatively larger
diameter. The con:ical portion defines an included solid
angle therein of at least ~5 degrees with respect to the
central longitudinal axis of the primary path.
BRIEF DESCRIPTI N OF TEIE DRAWINGS
For a better understanding of the invention, reference
may be had to the following description, taken in conjunction
with the accompanying drawings~ wherein:
Figure 1 is a partially broken away schematic
representation of an exemplary gas turbine engine to which
the present invention relates.
. . .
~:~'7~'~'7~7
13DV-7453
-- 4 --
Figure 2 is a sectional view ~howing a fuel nozzle of
the Prior Art.
Figure 3 is a sectional view, taken as in Figure 2,
showing one form of the fuel nozzle of the present
invention. For purposes of clarity, the fuel nozzle of
Figure 3 is illustrated as a larger structure than the fuel
nozzle of Figure 2.
D~TAILED DESCRIP~ION OF THE IN~ENTION
Referring initially to E'igure 1, one form of exemplary
gas turbine engine to which the present invention relates
is generally designated 10. The gas turbine engine 10 includes
a fan section 12, a compressor section 14, a combustor section
16, a high pressure turbine section 18, a low pressure turbine
section 20, and an exhaust section 22. The combustor section
16 includes a plurality of nozzles 19 which receive the fuel
flow to the enegine and develop an atomi2ed fuel flow for
ignition in the combustor 16. The nozzle 19 is coupled
through a fuel ste,m 21 to a fuel injector inlet 23. The fuel
inlet 23 is coupled to receive the engine fuel and controllably
pass the engine fuel to the nozzle 19 for subsequent atomization
and ignition.
Referring now to Figure 2, a typical Prior Art dual fuel
path fuel pressure atomizing nozzle 19 is shown in further
detail. The fuel nozzle 19 of Figure 2 includes an input
end l9A and an output end l9B. The nozzle 19 includes a
primary ~uel path 26 having an input end 26A for receiving
the primary fuel flow from the fuel ste~ 21 (not .shown in
Figure 2). The primary path 26 also includes an axially
opposi.ng output end 26B. Slots 28 are coupled to the primaxy
path 26 at a location between the input end 26 A and the
output end 26B thereof. The 310ts 28 function to direct the
primary fuel flow (see arrows) through additional spin slots
29. After passing through the slots 28 and 29, the primary
fuel flow is passed through a primary spin chamber 30 before
being directed out of primary output 26B. As is well known
in the art, the slots 28 and 29, and spin chamber 30, function
7'~
13DV 7453
-- 5
to impart a predetermined rotational motion of the primary
fuel flow as it is directed from the output 26B.
The Prior Art fuel nozzle 19 includes a secondary fuel
path 32 for receiving the secondary fuel flow from the fuel
stem 21. The secondary path 32 includes an input end 32A
and an output end 32B. The secondary path 32 is circum-
ferentially disposed in fixed relation around the primary
path 26. The output end 32B of the secondary path 32 is
circumferentially disposed around the primary path output
26B. The secondary path 32 also includes a number of
swirl vanes 33 through which the secondary fuel flow passes
before entering a secondary spin charnber 34. AS a result
of its passage through secondary path 32, the secondary fuel
10w output 32B iS provided with a rotational motion which
generally corresponds in direction to the rotational motion
of the primary flow at output 26B.
The nozzle 19 includes a nozzle discharge portion 36
which is circumferentially disposed around the primary and
secondary outpu-ts 26B and 32B. The nozzle discharge portion
36 functions to receive the interacting output flow from
outputs 26B and 32B and to develop an output therefrom or
use in subsequent ignition in the combustor section (not
shown in Figure 2). The nozzle discharge portion 36 includes
a conical portion 38. The conical portion 38 has an input
end 39 of relatively ,æmaller inside diameter (d), e.g.,
typically about .:15 inches, which increase along the longi-
tudinal central axis to an output end 4:L oE relatively larger
inside diameter (D)l e.g., typicalLy about .44 inches. The
conical poxtion 38 includes an interior surface 40 which
typically deEines an included solicl angle~therein o less
than 36 degrees with respect to -the central longitudinal
axis of the primary pa-th 26. The longitudinal length (1)
of the interior surace 40 is typically about .150 inches.
As noted previously, the Prior Art nozzle is typically
provided with a conventional air shroud structure 42 having
slots 43. The air shroud 42 is disposed circumferentially
13DV~7~53
-- 6
around the Euel nozzle 19 and Eunctions to receive and
direct air entering (see arrows) the combustor section
(not shown in Figure 2) through the slots 43 in a manner
so as to reduce the carbon formations on the interior conical
surface 40.
Referring now to Figure 3, one form of Euel nozzle c)f
the present invention is generally designated 50. The fuel
nozzle S0 of Figure 3 is similar in many respects to the
Prior Art fuel nozzle l9 of Figure 2 so that, wherever
possible, like reference numbers have been used to represent
like elements. The fuel nozzle 50 of Figure 3, however,
differs from the Prior Art fuel nozzle l9 of Figure 2 in
at least two significant respects. The fuel nozz:Le 50
is provided with a modified nozzle portion and includes no
air shroud structure.
More particularly, the nozzle discharge portion 36 of
the fuel nozzle 50 of the present invention is provided
with a conical portion 38 thereof having an interior surface
40 which defines a solid angle ~ of at least 45 degrees with
respect to the central longitudinal axis thereof. The
solid angle~ is preferably in the range of from about 50
degrees to abou~ 65 degrees with about 60 degrees being
a particularly preferred value. The longitudinal length
(1) of the interior surface 40 is typically about .080
inches. In addition, typical inside diameters (d) and (D)
of the nozzle 50 are .18 inches and .40 inches, respectively.
The fuel nozzle 50 is preferably providecl with a wear coating
52 along its exposecl exterior Eor protecting the Euel nozzle
50 Erom the harsh rubbing ac-tion between itself and the
combustor paxt in which it is inserted. Typically, the
wear coating 52 comprises a conventional high temperature-
resistant material. An exemplary wear coating 52 may
comprise, for example, .015 inches of chromium carb:ide.
Although, for purposes of illustration, the fuel nozzle
of the present invention has been described as being of
certain exemplary dimensions, other dimensions may be
7'-~
13D~-7453
-- 7 --
appropriate for certain applications.
Referring now to the operation of the nozzle 50 of
Figure 3, -the primary flow through primary path 26 and its
output end 26B is shown as resulting in a primary spray
60 which does not impinge on the interior conica' surface
portion 40. The secondary fuel flow through the secondary
path 32 and its secondary output end 32B is shown as
resulting in a secondary spray 620 An outer portion 62A
of the secondary spray 62 passes on and along the conical
surface portion 40. However, as mentioned previously, the
particular configuration of the discharge portion 36, i.e.,
the solid angle~ of at least 45 degrees, results in reduced
carbon formation along the surface portion 40. Indeed, the
configuration shown in the fuel nozzle 50 o~ Figure 3
obviates the need for an addltional air shroud structure,
such as the air shroud 42 shown in the Prior Art ~uel nozzle
of Figure 2. In this connection, the outer diameter of the
fuel nozzle 50 of Figure 3 may be abou-t the same as the
outer diameter of the fuel nozzle 19 of Figure 2, without
20 ~ the s~ shroud 42.
Although the uel nozzle of the present invention is
suitable for use in combination with many conventional fuel
stems, a preferred fuel stem is described in Canadian
~ patent application 3~ of J.M. Richey, et al, entitled,
"Dual Fuel Path Stem for a Gas Turbine Engine," ~iled
~bb~ ~3,lq~1. This Canadian paterlt application is assigned
to the assignee of the present application.
For some applications, it may be desirable to employ
the ~uel nozzle of the present invention in combination
with additional components for providing highly desirable
ignition in the combustor section. In this connection,
conventional structures, including airblast discs, venturi
shrouds, and secondary swirlers, may be employed. Such
conventional structures are shown in U.S. Patent ~,198,815,
issued April 22r 1980, to Bobo, et al, entitled, "Central
Injection Fuel Carburetor." This patent is assigned to the
assignee of the present invention.
~ 7~477
13DV-7453
-- 8
Although the fuel nozzle of the present inven-tion has
been illustrated as having a linear central longitudinal
a~is with axially opposing input and output ends, other
nozzle configurations may be appropriate for certain nozzle
applications. For example, for certain applications, the
central longitudinal axis may be curvilinear. In addition,
it is to be appreciated that the fuel nozzle of the present
invention is suitable for engine applications other than
the previously-discussed exemplary gas turbine engine.
Indeed, the fuel nozzle of the present inven~ion is applicable
to any gas turbine engine, such as one which includes only
a compressor section, a combustor section, and an exhaust
sec*ion.
Thus, there is provided by the present invention a fuel
nozzle which exhibits reduced carbon formation without
requiring an air shroud. The fuel nozzle of the present
invention is relatively simple to manufacture. Further,
the fuel nozzle of the present invention can be conveniently
inserted into and removed from its operating position in
the combustor section without the need to remove other
associated parts in the combustor section. AlSo, the fuel
nozzle of the present invention, as a result of its relatively
low weight, provides a desirable operational part life.
While the present invention has been described with
reference to specific embodiments thereof, it will be
obvious to those skilled in the art that various changes
and modifications may be made without departin~ from the
invention in its broader aspects. It is contemplatecl in
the appended claims to cover all variations and modifications
of the invention which come within the true spirit and
scope of our invention.
