IL35999A

IL35999A - Combustion apparatus

Info

Publication number: IL35999A
Application number: IL35999A
Authority: IL
Original assignee: Gen Electric
Priority date: 1970-04-30
Filing date: 1971-01-14
Publication date: 1973-07-30
Also published as: CA936371A; FR2086476A1; IL35999A0; FR2086476B1; DE2104171A1; NL7100863A; US3648457A; CH529973A; BE762244A; GB1333881A

Description

COMBUSTION APPARATUS COMBUSTION APPARATUS Abstract of the Disclosure: A combustion apparatus and fuel delivery means therefor having a spray nozzle projecting into a housing and adapted to direct fuel toward an annular array of vanes. The vanes are spaced radially outwardly of a housing outlet which is disposed in flow communication with the combustion chamber, and are adapted to receive pressurized air and direct it radially inwardly of the housin so as to generate a whirling mass of air within the housing and a vortical discharge from the outlet, whereby large fuel particles are centrifugally prevented from entering the combustion chamber until they have been sheared into small atomized droplets and small fuel droplets are entrained in the vortex and carried into the combustion chamber in a highly dispersed manner. 13D-4789 This invention relates to gas turbine engines and, more particularly, to combustion and fuel delivery apparatus for use in such engines.

Delivery of fuel into a continuous burning combustion apparatus, of the type commonly employed in gas turbine engines, in such a manner as to achieve complete and efficient combustion while minimizing the occurrence of fuel-rich pockets which, upon combustion, . produce carbon or visible smoke has posed a continuing design problem.

Solutions to the foregoing are complicated in gas turbine engines by the wide range of fuel flow rates and combustion air temperatures and pressures encountered in the normal operating range and by the required or desirable light-off and lean extinction characteristics of the combustion apparatus.

While spray atomizing nozzles of the well-known type adapted to utilize fuel pressure to deliver a single or dual cone of atomized fuel into the combustion chamber of a gas turbine engine through a small discharge orifice tend to exhibit good light-off and lean extinction characteristics, such nozzles are inclined to produce local fuel-rich pockets at high fuel flow rates and hence visible smoke efflux. On the other hand, fuel atomizing and/or vaporizing devices which utilize the energy of pressurized air, such as the gas turbine engine compressor discharge air, and/or the heat from the combustion process to deliver a fuel/air mixture to the combustion chamber may, in some installations, exhibit poor ignition or lean extinction characteristics due either to an overly lean or dispersed fuel/air mixture at low fuel flow rates or a lack 13D-4789 of sufficient energy in the combustion process or a lack of sufficient energy in the compressor discharge air to achieve the required fuel atomization. Additionally, such atomizing and/or vaporizing devices, of the type heretofore employed, generally introduce the fuel into the air stream at a point remote from or substantially upstream of the primary zone of the combustion chamber, which may under certain operating conditions encourage propagation of the flame upstream of the combustion chamber, flash-back or an otherwise unstable flame front.

The primary object of this invention is, therefore, to provide an apparatus for delivery of fuel into the combustion chamber of a gas turbine engine in a highly dispersed manner so as to substantially eliminate or mitigate the occurrence of visible smoke in the products of combustion.

A further object of this invention is to provide a low smoke, continuous burning combustion apparatus for a gas turbine engine which exhibits stable burning and possesses good light-off and lean extinction characteristics over a wide range of engine operating conditions.

Further objects and advantages of this invention will become apparent upon reading the following description of the preferred embodiments.

Briefly, the above and other objects of this invention are achieved by providing a housing having a downstream end wall formed with an outlet communicating with the combustion chamber. The housing includes an annular array of swirl vanes for directing pressurized air inwardly of the housing with a substantial tangential component so as to 13D-4789 generate a whirling mass of air within the housing and a vortical or cyclonic discharge from the outlet. Fuel injection means are provided for spraying fuel toward the vanes. The vanes are spaced radially outwardly of the outlet so that the large or heavy fuel particles are centrifugally retained within the housing until they have been sheared into small atomized droplets, whereupon such droplets are entrained in the vortex and carried into the combustion chamber.

By a further aspect of this invention, the fuel injection means is additionally adapted to provide a pilot conical spray of atomized fuel directly into the combustion chamber so as to enhance light -off characteristics during those portions of the engine operating regime wherein either fuel flow rates are low or the compressor discharge air lacks sufficient energy to satisfactorily atomize the fuel. The swirl vanes are preferably disposed in overlapping relationship so as to foreclose fuel discharge through the vanes.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of this invention, it is believed that the invention will be better understood upon reading the following description of the preferred embodiments in conjunction with the accompanying drawings wherein: Figure 1 is a fragmentary axial cross-sectional view of a gas turbine engine employing the fuel delivery and combustion apparatus of this invention; Figure 2 is a view like Figure 1 showing a further aspect of this invention; 1 3 D- 4789 · Figure 3 is an enlarged partial cross -sectional view of the discharge end of the fuel nozzle of Figure 2; and Figure 4 is a cross-sectional view taken along lines 4-4 of Figure 2.

Like reference numerals wi 11 be used in referring to like parts throughout the following description of the drawings.

With reference first to Figure 1 , a continuous burning combustion apparatus for a gas turbine engine has been shown generally at 10 disposed within suitable engine casing structure 11 and as comprising a hollow body 12 defining a combustion chamber 14 therein. The hollow body 12 includes a domed upstream end 16 having an inlet opening 18 therein for receiving a fuel/ air mixture. As will be understood by those skilled in the art, the combustion chamber 14 may be of the annular type, the cannular type, or the can type, with the apparatus 10 having a plurality of circumferentially spaced openings 18.

A snout assembly 20 is suitably secured to the upstream end of the hollow body 12 and is adapted to receive a pressurized flow of air from a suitable source, such as a compressor (not shown).

A fuel delivery apparatus 22 is provided at the upstream end of hollow body 12 and comprises a housing 24 having axi ally spaced upstream and downstream walls 26 and 28, respectively, with the downstream wall 28 formed with an outlet 30 in flow communication with the chamber 14 through inlet 18. An annular array of vanes 32 is provided to direct the pressurized air from within the snout assembly 20 inwardly 13D-4789 ί of the housing so as to igenerate a whirling mass of air within the housing 24 and a vortical or cyclonic discharge through outlet 30, as shown generally at 34.

For reasons which will hereinafter become apparent, the array of vanes 32 is spaced radially outwardly of the outlet 30 so as to define an annular chamber 36 between the radial inner edge 37 of each vane and the outlet 30.

Means for injecting fuel internally of the housing 24 and toward the vanes 32 have been shown at 38 in Figure 1 as comprising a fuel spray nozzle having a discharge end 40 of the well-known type adapted to utilize fuel pressure to generate a conical spray of atomized fuel 42. The fuel nozzle discharge end 40 projects through upstream wall 26 of housing 24 and is preferably disposed with its discharge axis coaxial to the housing outlet 30.

By a further aspect of this invention and with reference now to Figures 2 and 3, the discharge end 40 of fuel injection means 38 is adapted to provide the fuel spray 42 as a plurality of radial spokes or streams through openings 44 and a fuel flow passage 46, and, additionally, to provide a pilot spray cone of atomized fuel 48 directly into combustion chamber 14 through orifice 50 and passage 52. In this manner, it has been found that the ignition and lean extinction characteristics of the combustion apparatus 10 are greatly enhanced. This is particularly true in aircraft applications during altitude relight conditions when the compressor discharge air of a gas turbine engine may not have sufficient energy to finely atomize the fuel 42. 13D-4789 The housing 24 may include fluid directing means outwardly of the vanes 32 for efficient and streamlined delivery of the pressurized air thereto so as to enhance the strength of the vortical flow within the housing. For example, and with reference to Figures 2 and 4, the housing may include an outer wall 52, which extends between upstream and downstream walls 26, 28, outwardly of the vanes 32. In the embodiment of Figure 4, the outer wall 52 is involute or spiral in shape and forms a tangential inlet 54 for delivery of pressurized air to the housing 24. In addition, means 56, which extend upstream of the housing 24 and communicate with inlet 54, may be provided for streamline delivery of the pressurized air to the apparatus 22. It will be appreciated, however, that such fluid directing means may be widely varied.

In operation, air having a higher total pressure than that within chamber 14 is directed radially inwardly of the housing 24 with a substantial tangential velocity component by the array of vanes 32 so as to establish a whirling mass of air within the annulus 36 and a vortical or cyclonic discharge 34 to the combustion chamber 14 through outlet 30. Fuel is injected into the annulus 36 as a conical Jspray (Figure 1 ), as a plurality of radial streams (Figure 2), or otherwise by means 38. Upon discharge into the housing 24, a portion of the large fuel particles may be sheared into small atomized fuel droplets by the high velocity vortical airflow, while the remaining large fuel particles are centrifugally impinged against the vanes 32 by the vortical airflow within the housing 24. The fuel is then sheared off the radial inner edge 37 of each wetted vane as a finely atomized spray 13D-4789 58 by the airflow across the vane, as best shown in Figure 4. In this connection and as shown in Figure 4, the vanes 32 are preferably disposed in overlapped relationship or with . the leading edge 60 of each vane 32 circumferentially overlapping the trailing edge 37 of its immediately preceding vane so as to prevent the fuel from being sprayed or centrifuged through the vanes.

By spacing the vanes 32 radially outwardly of the outlet 30, large or heavy fuel particles, which if introduced into combustion chamber 14 would result in local over-rich burning and hence smoke, are centrifugally retained behind downstream wall 28 until they are atomized by one of the mechanisms described above into droplets of sufficientl small size that the centrifugal forces are overcome by the drag forces, whereupon such small particles are entrained in the swirling air and carried into chamber 14 with the vortex 34. In this manner, the present invention has been found highly effective in controlling the size of the fuel droplets entering the combustor 14.

In gas turbine engine applications having widely varying fuel flow rates, the fuel injection means 38 may be conveniently adapted to deliver a small amount of fuel in the form of a conical atomized spray 48 directly into the combustor 14 so as to enhance the ignition and lean extinction characteristics of the engine.

Since the fuel is introduced to the apparatus of this invention in close proximity to the combustor 14, problems involving flash-back or erratic propagation of the flame upstream of the combustor are eliminated. 13D-4789 From the foregoing, it will be appreciated that the present invention provides novel and highly effective means for delivery of an air/fuel mixture, which is characterized by highly dispersed small fuel particles, to a combustion chamber.

While several embodiments of the present invention have been depicted and described, it will be understood by those skilled in the art that numerous changes and modifications may be made thereto without departing from the invention's fundamental theme.

What is claimed is:

Claims

Appln. No. 3^ 9 2 C L A I M S t

1. A fuel delivery apparatus for a gas turbine engine, including, in combination, a housing formed with an outlet and including a plurality of fluid directing vanes disposed in a radially spaced annular array about said outlet, said vanes adapted to direct pressurized air radially inwardly thereof and generate a vortical flow of air internally of said housing and a vortical efflux from said outlet, and fuel injection means disposed in said housing adapted to deliver a first and second spray of fuel, said first spray of fuel being directed generally radially outwardly toward said vanes, whereby highly dispersed fuel droplets of controlled small size are discharged with said vortical efflux, and said second spray being directed through said outlet.

2. The fuel delivery apparatus of claim 1 further characterized in that said housing includes an upstream vail and a downstream wall, said vanes extending generally axially between s aid walls and disposed in overlapping relationship so as to prevent escape of said fuel through said vanes.

3. A continuous burning combustion apparatus including in combination, a hollow body defining a combustion chamber therein and formed with an inlet, a housing formed with an outlet in fluid flow communication with said inlet and including a plurality of generally axially extending fluid direetihg vanes disposed in an annular array outwardly of and about said outlet, fuel injection means projecting through an upstream wall of said housing for spraying fuel radially outwardly of said outlet toward said vanes, said Appln. o.35999/2 3-vanes adapted to receive a flow of pressurized air and direct said air radially inwardly of said housing so as to generate a vortical flow of air internally of said housing and a vortical discharge to said combustion chamber through said housing outlet, whereby the fuel droplets within said spray are sheared into minute particles and carried with said vortical discharge to said combustion chamber in a highly dispersed manner.

4. The combustion apparatus of claim 3 further characterized in that said fuel injection means is further adapted to deliver an atomized spray of fuel directly into said combustion chamber*

5. The combustion apparatus of claim 4 further characterized in that the leading edge of each vane is disposed in cireumferentially overlapped relationship to the trailing edge of the preceding vane.

6. A fuel delivery apparatus for a gas turbine engine, including, in combination, a housing formed with an outlet and ihcluding a plurality of fluid directing vanes disposed in a radially spaced annular array about said outlet, said vanes adapted to direct pressurized air radially inwardly thereof and generate a vortical flow of air internally of said housing and a vortical efflux from said outlet, and fuel injection means disposed in said housing for directing fuel radially outwardly toward said vanes, said fuel injection means, in cooperation with said vortical flow of air internally of said housing, being adapted to deposit at least a portion of said fuel on said vanes, whereby said fuel is sheared off a radial inner edge of each said wetted vane by the pressurized Appln.No. 35999/' air flow over said vane as a spra of fuel droplets of sufficiently small size to be entrained in the vortical flow and discharged from said outlet with said vortical efflux. Tel-Aviv, January 12, 1971 AGENT FOR APPLICANTS