U.S. patent number 3,577,878 [Application Number 04/783,009] was granted by the patent office on 1971-05-11 for flame tubes for gas turbine engines.
This patent grant is currently assigned to Joseph Lucas (Industries) Limited. Invention is credited to Kenneth Greenwood, Alwin Harrison, Alban Heaton, Squire Ronald Jackson.
United States Patent |
3,577,878 |
Greenwood , et al. |
May 11, 1971 |
FLAME TUBES FOR GAS TURBINE ENGINES
Abstract
A flame tube for a gas turbine engine includes a plurality of
primary combustion air inlets, a plurality of secondary combustion
air inlets and a plurality of dilution air inlets and variable flow
restricting means associated with at least some of the inlets for
varying the ratio of primary combustion air to secondary combustion
air to dilution air.
Inventors: |
Greenwood; Kenneth (Burnley,
EN), Heaton; Alban (Gt. Harwood, nr. Blackburn,
EN), Harrison; Alwin (Burnley, EN),
Jackson; Squire Ronald (Burnley, EN) |
Assignee: |
Joseph Lucas (Industries)
Limited (Birmingham, EN)
|
Family
ID: |
27258686 |
Appl.
No.: |
04/783,009 |
Filed: |
December 11, 1968 |
Current U.S.
Class: |
60/39.23; 60/794;
60/759 |
Current CPC
Class: |
F23R
3/26 (20130101); F05B 2250/411 (20130101); F05B
2260/70 (20130101); F23R 2900/00001 (20130101) |
Current International
Class: |
F23R
3/02 (20060101); F23R 3/26 (20060101); F02c
009/14 () |
Field of
Search: |
;60/39.65,39.23,39.26,39.27,39.29 ;431/351,352 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hart; Douglas
Claims
We claim:
1. An annular section flame tube for a gas turbine engine
comprising an annular chamber having an annular primary combustion
air inlet passage and at least one coaxial annular secondary
combustion air inlet passage opening into said chamber downstream
of said primary combustion air inlet passage, and airflow
restricting means at the upstream ends of said passages
displaceable in one direction to increase the intake area of the
primary combustion air inlet passage and simultaneously to decrease
the intake area of the secondary combustion air inlet passage and
movable in the opposite direction to decrease the intake area of
the primary combustion air inlet passage and simultaneously to
increase the intake area of the secondary combustion air inlet
passage.
2. An annular section flame tube for a gas turbine engine
comprising an annular chamber having an annular primary combustion
air inlet passage and at least one coaxial annular secondary
combustion air inlet passage opening into said chamber downstream
of said primary combustion air inlet passage, and airflow
restricting means at the upstream ends of said passages
displaceable in one direction to increase the intake area of the
primary combustion air inlet passage and decrease the intake area
of the secondary combustion air inlet passage and movable in the
opposite direction to decrease the intake area of the primary
combustion air inlet passage and increase the intake area of the
secondary combustion air inlet passage, a tubular wall separating
said primary combustion air inlet passage from said secondary
combustion air inlet passage, said airflow restricting means
comprising a plurality of flaps arranged in an annular row at the
upstream end of said tubular wall and pivoted on axes tangential to
said wall and means for displacing said flaps in one direction
across the secondary combustion air inlet passage and in the
opposite direction across the primary combustion air inlet
passage.
3. An annular section flame tube as claimed in claim 2 in which the
secondary combustion air inlet passage surrounds the primary
combustion air inlet passage.
4. An annular section flame tube as claimed in claim 3 further
comprising an additional annular secondary combustion air inlet
passage arranged coaxially within the primary combustion air inlet
passage and divided therefrom by a further tubular wall, further
flaps arranged in an annular row at the upstream end of said
further tubular wall and pivotable on axes tangential to said
further tubular wall, and further means for displacing said further
flaps outwardly across the primary combustion air inlet passage and
inwardly across the additional secondary combustion air inlet
passage.
5. An annular section flame tube as claimed in claim 4 in which
said means for displacing said flaps and said further means for
displacing said further flaps comprise the combination of a common
axially movable structure, means connecting said structure to said
flaps for inward displacement thereof by axial movement of said
structure in one direction and outward displacement of the flaps by
axial movement of the structure in the opposite direction and means
connecting said further flaps to the structure for outward
displacement of said further flaps by axial movement of said
structure in said one direction and inward displacement of said
further flaps by axial movement of said structure in the opposite
direction.
Description
BACKGROUND OF THE INVENTION
This invention relates to flame tubes for gas turbine engines.
In the flame tubes of such engines, it is the practice for a minor
amount of air, about 25--40 percent of the total air intake, to be
employed for the combustion of fuel, with the remainder being
employed for cooling the flame tube, diluting of the flame and of
the products of combustion before the latter are allowed to enter
the turbine stage of the engine. The air for combustion purposes is
itself normally separated into primary and secondary streams
entering along separate paths to the interior of the flame tube. In
some engines which are required to operate over a wide range of
fuel/air ratios, the combustion and dilution air quantities over
some parts of the operating range are incorrect thus impairing
combustion and dilution air quantities over some parts of the
operating range are incorrect thus impairing combustion efficiency
and giving rise to loss of performance over that part of the engine
operating range.
The object of the invention is to provide a flame tube for a gas
turbine engine in which this disadvantage is overcome or
reduced.
In accordance with the invention there is provided a flame tube for
a gas turbine engine having a plurality of primary combustion air
inlets, a plurality of secondary combustion air inlets, a plurality
of dilution air inlets and variable airflow restricting means
associated with at least some of said inlets for varying the ratio
of primary combustion air to secondary combustion air to dilution
air.
Reference is now made to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial section through an annular flame tube
incorporating one example of the present invention,
FIG. 2 is a view on the arrow X in FIG. 1,
FIG. 3 is a fragmentary view on the arrow Y in FIG. 2,
FIG. 4 is a pneumatic circuit diagram illustrating the manner in
which the arrangement shown in FIGS. 1, 2, 3 is operated,
FIG. 5 is a section through an annular flame tube illustrating
another embodiment of the present invention,
FIG. 6 is a fragmentary front view of the arrangement shown in FIG.
5,
FIG. 7 is a fragmentary sectionlike FIG. 5 showing another example
of the invention,
FIG. 8 is a view on the arrow 8 in FIG. 7,
FIG. 9 is another sectional view through an annular flame tube
showing yet another embodiment of the invention,
FIG. 10 is a similar section showing a further embodiment of the
invention,
FIG. 11 is a fragmentary sectional view showing yet a further
embodiment of the invention,
FIG. 12 is a view on the arrow 12 in FIG. 11,
FIG. 13 is a section of another annular flame tube incorporating
yet a further embodiment of the invention,
FIG. 14 is a section on line 14-14 in FIG. 13,
FIG. 15 is a section like FIG. 13 showing yet another embodiment of
the invention.
FIG. 16 is a section on line 16-16 in FIG. 15,
FIG. 17 is a sectional view illustrating a still further embodiment
of the invention,
FIG. 18 is a section of a primary combustion air inlet variable
flow restrictor,
FIG. 19 is a view on arrow `X` in FIG. 18; and
FIGS. 20 to 26 are views showing alternative forms of primary
combustion air inlet variable flow restrictors.
DETAILED DESCRIPTION OF THE INVENTION
Referring firstly to the embodiment shown in FIGS. 1 to 4 of the
drawings, the flame tube incorporates an inner annular passage 30
for the primary combustion air, a surrounding annular passage 31
for secondary combustion air and an outer annular passage 32 for
the dilution air. The passage 30 has an annular intake 33 whereas
the passage 31 has a pair of annular intakes 34, 35 disposed
respectively inside and outside the intake 33. A row of vanes 36
are mounted in the intake 33 and rows of vanes 37, 38 are likewise
mounted in the intakes 34, 35 respectively. The vanes 36, 37 and 38
are on a series of common shafts arranged so that when the vanes 36
lie in planes parallel to the axis of the engine, the vanes 37, 38
are offset and vice versa. Thus when positioned as shown in full
lines in FIG. 2 the primary combustion airflow will be restricted
while the secondary combustion airflow will be substantially
unrestricted.
The vanes, are, however, associated with pneumatic actuators 39
associated with pipework 40, 41 whereby the vanes can be turned to
the positions shown in dotted lines in FIG. 2 such that the vanes
36 scarcely restrict airflow into the intake 33 whereas the vanes
37, 38 restrict airflow into the intakes 34, 35. As will be seen
from FIG. 3 the actuators 39 are arranged to turn alternate ones of
the shafts on which the vanes are mounted in one direction and the
remaining shafts in the opposite direction so that no swirl is
introduced either into the primary combustion air or secondary
combustion air.
FIG. 4 shows how a single valve 42 can be employed to control the
supply of compressed air to the pipework 40, 41 and the exhausting
of air therefrom to enable all the vanes 36, 37, 38 to be adjusted
simultaneously.
Turning now to FIGS. 5 and 6, the flame tube has a series of
primary air inlets 50 each provided with swirler vanes which are
known per se. Secondary combustion air is introduced via inwardly
directed nozzles 51, of which there are two in association with
each of the primary air inlets. Dilution air is introduced at two
stages in the flame tube, mainly through a first series of nozzles
52 downstream of the nozzles 51 and through a second series of
nozzles 53 downstream of the nozzles 52. The nozzles 53 are
supplied via ducts 54 which open into intakes upstream of the
nozzles 51. The flame tube si provided with axially movable
deflector vanes 55 which can be moved from the positions shown in
FIG. 5 in which they cover the intakes to the ducts 54, to
positions in which they cover intakes to the secondary combustion
air nozzles 51.
Referring now to the examples shown in FIGS. 7 and 8, the basic
layout of the flame tube is similar to that shown in FIG. 1, that
is to say there is an annular primary air duct 60 surrounded
externally by a first secondary air duct 61 and internally by a
second annular secondary air duct 62. There are also dilution air
passages 63, 64 respectively outside the duct 61 and inside the
duct 62.
For controlling the proportions of primary and secondary air there
are provided three annular flow restricting members 65, 66, and 67.
These three restrictors are joined together by means of radial arms
68 so as to be movable axially relative to the flame tube by means
of rods like the rod 69. At one limit of the travel, as shown in
FIG. 7 the annular restrictors 65, 66 restrict the entry of
secondary combustion air to the ducts 6l, 62 respectively. In this
position the restrictor 67 is deep inside the duct 60 and provides
little restriction of the airflow therethrough. It will be noted,
however, that the duct 60 diverges markedly from its intake so that
when the restrictors are moved the their other position (as shown
in dotted lines in FIG. 7) the restrictor 67 will provide a
considerable restriction in the intake of the duct 60, whereas the
restrictors 65, 66 will have little effect on the airflow into the
ducts 61, 62 respectively.
In the example shown in FIG. 9 the secondary air intake is defined
by an outer tube 70 and an inner tube 71. The outer tube 70 lies
outside an inner tube 72 forming the outer wall of the primary air
duct the inner wall 73 of which is outside the tube 71. The
primary/secondary combustion air proportions are varied by means of
a pair of annular rows of flaps 74, 75. These flaps are pivoted on
tangential axes and when, as shown in FIG. 9 the outer row of flaps
74 are pivoted inwardly and the inner row of flaps 75 are pivoted
outwardly there is a minimum area for primary airflow and a maximum
area for secondary airflow. A mechanism is provided for pivoting
the flaps 74 and 75 simultaneously be means of an axially movable
structure to the dotted positions shown in FIG. 9 in which the
secondary airflow is minimized and the primary combustion airflow
is at a maximum.
A similar flap arrangement is shown in FIG. 10 but, in this case,
all the secondary combustion airflow enters through a single outer
duct 80 which is controlled by a single row of annular flaps 81
movable by means of piston and cylinder units 82 and bell cranks
83.
In FIG. 11 an arrangement is shown for varying the secondary
airflow by means of a series of louvre-type flow restrictors 90
controlling ducts 91 terminating in nozzles 92 whereby secondary
air enters and mixes with the primary airflow and the flame. The
louvres 90 are movable by means of a Bourdon tube 93 which receives
pressure from a common manifold 94. Dilution air enters the
combustion chamber at a position downstream of the secondary air
inlet nozzles 92 via nozzles 95 which are controllable by closure
members 96 movable into the nozzles 95 by means of pressure
operable bellows 97.
In the example shown in FIG. 13 and 14 the flame tube has an
axially slidable portion 100 which telescopes with a portion 101
formed with secondary air inlets 102. The portion 100 is formed
with dilution air inlets 103. In the position shown in full lines
in FIG. 13 the secondary air inlets 102 are fully open whereas the
dilution air inlets 103 are restricted by a fixed wall 104.
Movement of the portion 100 of the flame tube, however, causes
partial closing of the secondary air inlets 102 while the dilution
air inlets 103 are fully opened.
Turning now to FIGS. 15 and 16 the flame tube in this case includes
an outer rotatable wall 110 and an inner rotatable wall 111. These
rotatable walls carry a plurality of valve elements 112, 113 to
coact with secondary air inlet ports 114, 115 respectively and may
additionally carry further valve members 116, 117 to coact with
dilution air inlets 118, 119 respectively. The outer and inner
rotatable walls 110 and 111 have ring gears 120, 121 respectively
which engage pinions 123, 124 respectively on shafts linked by
bevel gear trains to provide reverse rotation of the inner and
outer walls on turning an input shaft 125.
In FIG. 17 the secondary air inlets 130 and the dilution air inlets
131 are respectively controlled by valve members 132, 133 on
opposite ends of a rockable lever 134 movable by a push rod 135 so
that, in the position shown in full lines the secondary air inlets
are restricted, whereas in the position shown in dotted lines the
dilution air inlets 131 are restricted.
FIG. 18 shows an annular primary air conduit wall 140 having
positioned circumferentially thereabout as shown in FIG. 19, a
plurality of bimetallic segments 141. The segments 141 each extend
into the conduit from outside the wall and the outer end of each
segment is connected to an electrically heated retaining ring 142.
In operation of the arrangement, the outer ends of the segments are
heated in order to effect deflection of each bimetallic element
towards the axis of the conduit thereby restricting airflow through
the conduit. The flame tube has a series of the conduits 140
opening via swirlers 143 in a common annular combustion space. A
burner (not shown) extends into the combustion space through the
swirler 143.
FIG. 20 shows an arrangement similar to that shown in FIGS. 18 and
19. In this embodiment, however, the bimetallic strips 141a are
wholly outside the primary air conduit wall apart from an angled
end piece 141b, with these end pieces being directed slightly in
the direction of airflow through the conduit. On heating the
bimetallic strips by means of the electrically heated retaining
ring 142, the angled pieces 141b are caused to project across the
cross section of the conduit in order to restrict airflow to the
desired extent.
The embodiment shown in FIG. 21 has a flow restrictor comprising
four curved shutters 150, 151 and 152, 153 each of which is movable
radially into the primary flow conduit through slots in an annular
wall 154. The segments 150, 151 are provided with integral lugs
155, 156 respectively and each of which has a pin 157 which extends
through a slot in an eye 158 secured to one end of a pair of
bimetallic strips 159, 160 interconnected to a common electrically
heated element 161. The shutters 152, 153 are also connected in
similar fashion to double bimetallic strips 162, 163 which are in
turn connected to heating element 164. In operation, the heating
elements control radially inward or outward movement of the
shutters to restrict the flow path for primary air. It should be
noted that FIG. 21 shows the shutters 150, 151 closed and the
shutters 152, 153 open. This condition does not, of course, occur
in actual use.
The flow restrictor illustrated in FIG. 22 comprises a butterfly
shaped bimetallic element 170 carried by an electrically heated bar
172 which extends diametrically across the primary air conduit. On
applying heat to the heating bar 172 the "wings" of the element 170
diverge to restrict the airflow through the conduit
The embodiment shown in FIG. 23 comprises arcuate Bourdon tubes 180
connected at one end to a pressure manifold 181. The other end of
each tube 180 has a pin 182 which is slidable within a slot 183 in
an eye 184 at one end of restrictor segments 185 which extend into
the conduit, with the restrictor segments being pivoted at 186. On
pressure being applied within the tubes 180, the 180 tend to extend
so as to pivot the elements 185 about pivots 186 to remove the
elements 185 from the conduit thereby restricting airflow
therethrough. On removal of pressure form the tubes 180 the
elements 185 are pivoted to extend into the conduit to restrict
airflow therethrough. There are a series of the segments 186 about
the conduit, each having its own Bourdon tube.
The embodiment of FIG. 24 is a modification of that shown in FIG.
23 with the difference that the separate elements 185 are dispensed
with and restriction of the airflow is effected merely by the
closed ends of the Bourdon tubes 187.
In FIG. 25 restriction of the primary airflow is effected by a
Bourdon tube 190 in spiral form and which extends across a conduit
191. The spiral tube 190 is retractable to the position shown in
dotted lines in order to restrict airflow on removal of pressure
from the interior of the tube.
The arrangement shown in FIG. 26 is a modification of that of FIG.
25 and embodies a solid spiral restrictor 200. Extension and
retraction of the restrictor 200 is effected by a pressurizable
bellows 201 slidably mounted on a central spindle 202 through the
intermediary of sealing rings 203. The interior of the bellows is
in communication with the exterior of the conduit through the
intermediary of a pipe 204. In this embodiment, increase in
pressure within the bellows 201 causes extension of the bellows
which results in closure of the spiral restrictor 200 and hence
restriction of the primary air conduit.
* * * * *