GB2244551A

GB2244551A - Variable-geometry air swirler

Info

Publication number: GB2244551A
Application number: GB9110725A
Authority: GB
Inventors: Jack Rogers Taylor; Willard James Dodds; Edward Ernst Ekstedt
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1990-05-29
Filing date: 1991-05-17
Publication date: 1991-12-04
Also published as: ITMI911262A0; DE4116405A1; IT1248305B; GB9110725D0; JPH04227411A; FR2662783A1; ITMI911262A1

Abstract

An air swirler 60 having a self-actuated variable geometry vane system to initially mix the fuel and air includes a plurality of swirl vanes 84 made of a bimetallic temperature responsive material and movable between open and closed positions as a function of temperature when the swirl vanes are subjected to heat. <IMAGE>

Description

k 1 SWIRLER The present invention relates generally to gas turbine engine

combustion systems and, more particularly, to a swirler for mixing air and fuel in such combustion systems. An embodiment of the invention concerns a variable geometry swirler.

Many combustion Chwribers within gas turbine engines employ flow nodifying devices, such as swirlers, to mix fuel and air and to aid in distributing the resultant mixture within the combustion chamber. The swirling air increases the tendency of the fuel to atcmize, causing better mixing and thus mre efficient burning of the mixture in the combustion chamber.

Typically, the swirler my rise a swirl cup disposed about a fuel nozzle within a dame at the upstream end of a hollow liner forming the caffibustion chaniber. The swirl cup includes a plurality of radial, axial, or a hybrid combination of radial and axial, swirl vanes disposed within the swirl cup upstream of the exit plane of the fuel. The swirl vanes provide highly turbulent shear flow that causes rapid atcmization and mixing of the fuel and air. 0==1y, these swirlers have a fixed gecimetry. Iliat is, the amount of and direction of discharge, or swirl angle, of air frcm the swirler is relatively constant, regardless of the amount of fuel which is injected into the ccirbustion chr.

ever, these fixed geometry swirlers cannot provide stable operation and high efficiency over a wide range of trature rise conditions that is required in current advanced gas turbine tngines. At lower paweer conditions, low air flows in the ecubastor dame are needed for good combustion stability. Further, lightoff (i.e., engine ignition) and idle ccmclitims 1 require relatively rich fuel-air mixtures and low air velocitJ es in the combustor dcme for stable operation. on the other hand, at high power conditions, where the combustor exit taimperature approaches high values, the canbustor requires high air flow and high velocities in the combustor dome for high combustion efficiency and low smoke mid Mx generation.

This problem can be solved by using variable geometry swirlers where the fudl and air are initially mixed. Variable geometry swirlers have been used with good success to provide the desired ccmbustor dome stoichicimetry over a wide range of temperature rise conditions. Variable gecimetry swJxlers generally include a swirl cup with externally actuated swirl vane systems. However, the externally actuated swirl vane systems of the variable gecmtry swirlers require a very camplex arrangement of rotating shafts, large unison rings, and levers to mechanically Tnove the swirl vanes and vary the air flow in the swirl cup. These mechanically actuated systems result in added cost, weight and concern for the reliability of the ccabustion system.

Illustrative embodiments of the invention disclosed herein, seek to provide:

a variable geometry swirler that does not require an externally actuated system; a variable geometry swirler that does not require a complex mechanically actuated system; a variable geometry swirler that has fewer parts, resulting in reduced cost and engine weight; and/or an automatic actuated system, eliminating engine control requirements or mechanisms.

-he present invention a In a preferred embodiment of -11 variable geometry swirler is provided wi- th a self-actuated 2 C 1 variable geometry system to initially mix the fuel and air. More specifically, the variable geometry swirler includes a plurality of swirl vanes made of a temperature responsive material and movable between open and closed positions as a function of temperature when the swirl vanes are subjected to heat.

Accordingly, the embodiment does not require an externally actuated system for the variab le geometry swirler. As a result, the embodiment eliminates the need for external unison rings, levers, and control systems i-isuall',v fc.,j.rid in a complex mechanical actuating system. Further, the embodiment requires fewer parts which reduces the weight and mechanical complexity of the enaine, resultinq in a less costly engine. Still further, the embodiment provides an automatic actuated system, eliminating engine control requirements or mechanisms.

The present invention will become better understood.by reference to the following illustrative description when considered in connection with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a gas turbine engine.

FIG. 2 is an enlarged view of the circled portion of FIG. 1 illustrating a combustor.

3 1 FIG. 3 is a frag"tary view taken along line 3-3 of FIG. 2 illustrating the selfactuated variable geometry swirler acxxnding to the present invention.

Referring to the drawings, wherein like numerals correspond to like -elements, attention is first directed FIG. 1. in FIG. -1-, there is shown a conventional gas turbine engine 10, such as a turbofan gas turbine engine. The gas turbine engine 10 includes an outer casing or nacelle 12, the upstream end of which form an inlet, generally indicated at 14, sized to provide a predetermined air flow. Disposed within the inlet 14 is a fan, generally indicated at 16. The fan 16 pressurizes the air flow from the inlet 14. Downstream of the fan 16 is a core engine, generally shown at 18. The core engine 18 includes an axial flow c=pressor, generally indicated at 20. Pressurized air from the fan 16 enters the core engine 18 and is further CCEL1plessed by the compressor 20 and discharged to a canbustor, generally indicated at 22. In the cambustor 22, fuel is burned to provide high energy combustion crases which drive a core engine turbine, generally indicated at 24. The core engine turbine 24, in turn, drives the ccmpressor 20 thr a shaft 26 in the usual manner of a gas turbine engine. Hot cgwb-istion gases can then pass to and drive a fan turbine, generally indicated at 28, which, in turn, drives the fan 16 through a shaft 30 in the usual wanner of a gas turbine engine. A riore detailed description of the gas turbine engine 10 is disclosed in either U.S. Patent No. 3,879,941 --Sargisson or U.S. Patent No. 4,080,785 - Koff et al, both of which are assigned to the same assignee as the present invention.

Referring to FIG. 2, an enlarged view of the mstor 22 is shown.' Preferably, the cwbustor 22 is an annular ctor having multiple fuel 4 nozzles circumferentially arranged within the annular carbustor. It should be appreciated, however, that the ccubustor 22 may be a ccntmtor annular arrangement where mutliple combustors are circumferentially arranged around the gas turbine engine 10. The ccabustor 22 includes a hollow liner 32 defining a combustion chanix-x 34 therein. The hollow liner 32 includes a transverse, upstream dome 36 formed integrally therewith. As will be understood by those skilled in the art, the oaffbustion chaffber 34 way be of an annular or cannular type.

7he combustor 212 also includes an outer casing 38 and an inner casing 40 provided around the hollow liner 32 and, in cooperation with the hollow liner 32, define outer and inner passageways 42 and 44, respectively. As will be understood by those skilled in the gas turbine engine art, the passageways 42 and 44 are adapted to deliver a portion of pressurized air frcxn a suitable source, such as the ccxnpres-,-or 20, into the ccabastion chamber 34 through suitable apertures or louvers 46 in the hollow liner 32.

The pressurized air is delivered from the ccnpressor 20 through a step diffuser 50, whereupon the air is divided between the outer and inner passageways 42 and 44 with a portion of the air flow entering through an opening 52 formed by a snout meirber 54 which is positioned upstream of the dame 36 and cooperates therewith to form an annular cha:mber 56. The snout member 54 may be integral or attached to the dome 36 and can be secured to the outer casing 38 by means such as fasteners 58. The air flow from the annular chamber 56 enters a swirler# generally indicated at 60. The pressurized air delivered to the passageways 42 and 44 cools the hollow liner 32 and flows through the louvers 46 to dilute the gaseous products of combustion as is well knmm in the art. An ignitor 61 threadably engages the outer casing 38 and extends into the combustion chmrber 34 near the 1 1.

downstream end of the swirler 60 to ignite the fuel and air mixture as is f well known in the art.

7he fuel for ccwbustion is delivered frcm a fuel source (not shown) to a hollow fuel tube 62 which is connected to the outer casing 38 by mans of a mounting bracket 64. The mounting bracket 64 is secured to the outer casing 38 by means such as fasteners 66. The fuel tube 62 is curved so as to fit within the opening 52 of the snout meffber 54. A fuel nozzle 68 is disposed at the end of the fuel tube 62 within the annular chamber 56.

The swirler 60 is disposed about or surrounds the fuel nozzle 68 and is connected to the dame 36. The swirler 60 includes a generally cylindrical swirl cup 70 which ray be integral or attached to the dome 36.

The swirl cup 70 is surrounded by a flared trumpet outlet 72 at the downstream end which extends into the combustion chamber 34. The swirl cup 70 has an annular and radially extending flange 73 at the upstream end. A venturi shroud 74 is disposed partially within the swirl cup 70 and is disposed about or surrounds the end of the fuel nozzle 68. The venturi shroud 74 has an annular disc 76 which ray be integral or attached to the swirl cup 70. The annular disc 76 is spaced axially from the radial flange 73 to define a fluid passageway through which air enters frce a generally radial direction, as indicated by the arrows, for secondary flow to be mixed with fuel exiting the venturi shroud 74. The venturi shroud 74 includes a generally annular L shaped member 78 extending between the fuel nozzle 68 and the annular disc 76 and which may be integral or attached to the annular disc 76. The swirler 60 can also include a plurality of fluid ducts or openings 80, in the L- shaped member 78, through which air enters from a generally radial and axial direction, as indicated by the arrow, into the venturi shroud 74 for primary flow to be mixed with fuel in the venturi shroud 74.

6 Referring to Figures 2 and 3, the swirler 60 includes a plurality of swirl vanes 84 which are self-actuating to form a self-actuating variable geometry swirler according to the present invention. The swirl vanes 84 are radially extending and arranged circumferentially inside the swirler 60 between the radial flange 73 and annular disc 76. It should be appreciated that the swirler 60 my have a different geometry such that the swirl vanes 84 may be axially extending or a hybrid of radially and axially extending vanes.

The swirl vanes 84 have a first end 86 secured about a first pin 88 extending axially between the radial flange 73 and the annular disc 76. The swirl, vanes 84 have a second end 90, the travel of which nay be limited by stops such as a second and third pin 92 and 93, respectively, extending axially from either the radial flange 73 or annular disc 76. As shown in Figure 3, the second pin 012 limits vane travel and precisely positions the swirl vane 84 at the fully open position as shown in solid lines. The third pin 9i limits vane travel and precisely positions the swirl vane 84 at the fully closed position shown in dotted lines.

7he swirl vane 84 is made of a bimetallic material which is tmperature sensitive or responsive. The swirl vane 84 my comprise a first strip 94 of a first material and a second strip 96 of a second raterial attached or integral with the first r-trip 94. The second strip 96 is teffperature responsive to nx)ve the first strip 94 as a function of temperature when heated. In the preferred embodiment, the swirl vanes 84 deflect from the closed position in a counter-clockwise direction as the inlet air flow trature increases, thereby increasing the metering gaps and swirler air flow. A -preferred range for transition of the swirl vanes 84 is between 400OF (vanes closed) and 600OF (vanes open). It should be appreciated that a bimetallic strip could be used to actuate a lever that moves the swirl vanes 7 f 84, or a ' tqperature sensitive Offemry rnetal' material could be used to actuate the swirl vanes 84.

In eperation, pressurized air flow fran the compressor 20 enters through ing 52 into the annular chr 56. Air flow fram the amular chamLer 56 flaws through the fluid ducts 80 and the venturi shroud 74 for a primary flow. Air flow fran the annular eh 56 enters through the passageway between the annular disc 76 and radial flange 73. 7he swirl vanes 84 impart a swirling or vortical motion to the air flowing in the passageway for a secary flow. As the fuel exits the fuel nozzle 68, it is mixed with air in the swirler 60 and the resulting mixture enters the cartustion chamber 34 to beburned. The swirling or vortical motion of the air flow mixes the air with the fuel, emitted from the fuel nozzle 68 into the venturi shroud 74, causing atomization of the fuel and thereby pren ting better mixing.

Accordingly, the swirl vanes 84 are self-actuated to move between open and closed positions in response to the expansion and contraction of the bimetallic material or strip coaprising the swirl vane 84. The variable gecimetry of the swirl vanes 84, as a result of being =wed or actuated, provides positive control of combustor dam stoichiametry. Since externally actuated mechanisms for the swirl vanes 84 are eliminated, the swirl vanes 84 provide a simple, reliable and light weight system. Because the swirl vanes 84 are self-actuated, an automatic actuated system for the swirl vanes 84 is provided, eliminating engine control requirments.

The present invention has been described in an illustrative manner.

It is to be understood that the terminology which has been used is intended_ to be in the nature of words of description rather than of Uidtation.

8

Claims

Claims:

f 1. A swirler for surring a fuel nozzle in a gas turbine engine cotor, cising:

means forming a swirl cup having an upstream end surrounding the fuel nozzle and extending axially. to a downstream end to define an annular flow path therebetween. and self-actuating swirl vane weans disposed in said flow reth for generating a swirl flow of air at the downstream end thereof.
2. A swirler as set forth in claim 1 wherein said self-actuating vane means ccoprises a plurality of swirl vanes having a fixed first end and a movable second end.
3. A swirler as set forth in claim 2 wherein said pluralicy of swirl vanes are mde of a trature responsive Mterial adapted to mve said second end beetwe-en first and second positions as a function of temperature when said plurality of swirl vanes are subjected to heat.
4. A swirler as set forth in claim 3 including means for limiting the travel of said second end.

9
5. A swirler for surrounding a fuel nozzle in a gas turbine engine LX21bustor,' Clslng:

venturi shrcmd surrounding the fuel nozzle; swirl cup partially surrounding raid venturi shroud and "ting therewith to define an annular flow path therebetween; a plurality of swirl vanes disposed in c-aid flow path and adapted to swirl air flowing th said flow path; and terature responsive means for moving said swirl vanes between open and closed positions as a function of twperature when said swirl vanes are subjected to heat.
6. A swirler as set forth in claim 5 wherein said swirl vanes and said temperature responsive means define a bimetallic strip.
7. A swirler as set forth in claim 5 wherein said temperature responsive means rises at least one strip made of a temperature responsive material to move as a function of temperature.
8. A swirler as set forth in claim 7 wherein said strip moves between open and closed positions when the trature ranges between 400OF and 6000F, respectively.
9. A swirler as set forth in claim 8 wherein said strip has a fixed first end and a movable second end.
10. A swirler as set forth in claim 9 including means for limiting the travel of said second end.

1 A
11. A swirler for surrounding a fuel nozzle in a gas turbine engine ccimbustor, canprising: a venturi shroud having an upstream end surrounding the fuel nozzle and extending axially to a downstream end, said venturi shroud having a radially extending annular disc; a swirl cup surrounding said venturi shroud and having a radially extending flange spaced axially from said annular disc and cooperating therewith to define an annular flow path therebetween; a plurality of radial swirl vanes positioned between said annular disc and said radial flange and adapted to swirl air flowing through said flow path; a first pin extending axially between said annular disc and said radial flange; and said raclial swirl vanes having a first end secured to said first pin and a movable second end, said radial swirl vanes being made of a bimetallic material which moves said second end between open and closed positions as a function of tenperature ranging between 4000F and 6000F, respectively, when said radial swirl vanes are subjected to heat.
12. A swirler for a fuel nozzle of a qas turbine engine substantially as hereinbefore described with reference to the drawincTs.

11 q, Published 1991 at The Patent Office. Concept House, Cardiff Road. Newport, Gwent NP9 I RH. Further copies may be obtained from Sales Branch, Unit 6. Nine Mile Point, Cwmfehnfach. Cross Keys. Newport, NPI 7HZ. Printed by Multiplex techniques lid, St Mary Cray. Kent.