Fuel Delivery Apparatus

Abstract

Apparatus is disclosed for premixing air and fuel or carbureting air prior to introduction thereof into the primary zone of a combustor, said apparatus including a housing defining a spin chamber therein; the spin chamber is adapted to receive air and fuel and vaporize and/or atomize said fuel and deliver said air and fuel into said combustor as a vortical flow.

Description

This invention relates to combustion apparatus and, more particularly, to apparatus for supplying fuel to a combustion chamber.

Delivery of fuel into a continuous burning combustion apparatus, as for example in gas turbine engines, in a highly dispersed manner so as to achieve complete and efficient combustion of the fuel and, at the same time, minimize the occurrence of fuel-rich pockets which, upon combustion produce carbon or smoke, has posed a continuing design problem. Solutions of this problem are further complicated in applications such as gas turbine engines by the severe temperature environment of the combustion chamber as well as overall length limitations for the combustion apparatus.

While spray atomizing nozzles of the type adapted to deliver a single or dual atomized conical fuel spray through a small discharge orifice have heretofore enjoyed widespread usage, such devices are generally complex and expensive in nature and generally require a relatively expensive and complex high pressure fuel delivery or distribution system. Furthermore, such spray atomizing nozzles tend to produce local fuel-rich pockets and are sensitive to fouling by carbon deposits or other deleterious matter.

Another approach which has been heretofore employed involves the use of tubes which extend into the combustion chamber for delivery of air and fuel to a cup which is disposed in the primary combustion zone of the combustor and is adapted to extract energy from the combustor flame to vaporize the fuel. With such an approach, however, life problems are encountered with respect to the elements protruding into the hot region of the combustor.

This invention, then, is concerned with an efficient fuel delivery apparatus which overcomes the foregoing problems.

A primary object of this invention is to provide relatively simple and economical means for delivery of fuel into a combustion chamber in a highly dispersed manner.

Another object of this invention is a long life fuel delivery apparatus adapted to receive air and fuel, atomize and/or vaporize the fuel, and carburet the inlet air with such fuel or premix the fuel and air prior to introducing the fuel into the primary zone of the combustor.

A further object of this invention is an apparatus for supplying fuel to a combustion chamber which is relatively insensitive to fouling, does not require a high pressure fuel distribution system, and is of relatively short axial length.

Yet another object of this invention is an apparatus which is adapted to utilize the energy of the inlet air to effect delivery of the fuel to the combustion chamber in a highly dispersed manner.

The above and other objects are achieved in the present invention by providing a housing having a central or core outlet in flow communication with the combustion chamber and defining a spin chamber around the outlet. The spin chamber is adapted to receive and circulate pressurized air and fuel around the outlet and generate a vortical discharge of air from the outlet. In this manner, the fuel is vaporized and/or atomized and delivered into the combustion chamber with the air vortex. The spin chamber is preferably formed with an involute or spiral shaped outer wall and generally planar upstream and downstream end walls. Inlet passage means may be provided for receiving a generally axially directed flow of pressurized air and directing such air in a generally streamline manner into the spin chamber. The inlet passage means may also be adapted to receive and direct the fuel into the swirl chamber although separate passage means may be used. Swirl vanes may be employed to enchance the rotational velocity of the vortex discharge as well as accurately locate the vortex centrally of the outlet.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of this invention, it is believed the invention will be better understood upon reading the following description of the preferred embodiment in conjunction with the accompanying drawing wherein:

FIG. 1 is a fragmentary axial cross section view of an exemplary gas turbine engine combustion apparatus embodying the present invention;

FIG. 2 is a front elevational view, in partial cross section, of the fuel delivery apparatus of this invention;

FIG. 3 is a side view, in partial cross section, of the apparatus of FIG. 2; and

FIG. 4 is a cross sectional view taken along lines 4--4 of FIG. 2.

Referring now to the drawings, and particularly to FIG. 1, a continuous burning combustion apparatus of the type suitable for use in a gas turbine engine has been shown generally at 10 as comprising a hollow body 12 defining a combustion chamber 14 therein. The hollow body 12 includes a domed upstream end 16 having an 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.

An outer shell 20 may be provided to enclose the hollow body 12 and define passages 22 and 24 in cooperation with the hollow body 12 and a snout assembly 26. As will be understood, the passages 22 and 24 are adapted to deliver a flow of pressurized air from a suitable source, such as a compressor 28, into the combustion chamber 14 through suitable apertures or louvers 30 for cooling of the hollow body 12 and dilution of the gaseous products of combustion.

The snout assembly 26 is suitably secured to the upstream end of the hollow body 12 and is adapted to function as a flow splitter to divide the pressurized air delivered from the compressor 28 between passages 22, 24 and a passage 32 formed through the snout assembly.

The fuel injection or carbureting apparatus of this invention has been shown generally at 34 as comprising a housing having inlet passage means 36 for receiving pressurized air from snout assembly passage 32, a central or core outlet 38 in flow communication with the hollow body opening 18 for delivery of an air/fuel mixture into the combustion chamber 14 as a vortical flow 40, and means 42 for receiving fuel from a suitable conduit 44 which extends through the snout assembly 26 and outer shell 20 and communicates with a source of pressurized fuel. Although the fuel injection apparatus 34 is particularly suited for use with liquid fuel and will be hereinafter described in connection with a liquid fuel, it will be appreciated that fuel in the liquid state, gaseous state,, solid state or a combination thereof may be employed.

As will be understood, suitable ignition means (not shown) of well known construction are provided within the combustion chamber 14 to provide initial ignition of the combustible air/fuel mixture discharged through outlet 38.

Referring now to FIG. 2, the housing comprises an involute outer wall 48 and generally planar, spaced, upstream and downstream end walls 50 and 52, respectively, peripherally joining the outer wall and defining, in cooperation therewith, an air vortex generator or spin chamber 46 within the housing outwardly of the core opening 38. As shown in FIG. 2, the outer wall 48 is generally involute or spiral in shape with a progressively decreasing radius from the inlet passage 36 to a terminal edge or lip 54 which defines, in part, the inlet opening from the passage 36 to the spin chamber 46. The inlet passage 36 is formed with a generally axially facing, upstream end opening for receiving the flow of pressurized air from passage 32 and has one wall formed as a streamline continuation of the involute outer wall 48 so as to deliver the inlet air in a generally streamline manner into the spin chamber 46. In this manner, pressurized air is directed into the spin chamber 46 in a circular motion of ever-decreasing radius so as to generate the vortical or cyclonic discharge 40 having a hollow core 56. To further enhance the swirling motion of the air as well as accurately position the vortical flow 40 relative to the opening 38, a plurality of swirl vanes 58, each of which extends between the upstream and downstream walls 50 and 52, may be provided in a peripheral array about the outlet 38 as shown in FIG. 2. Such an array of swirl vanes may also be adapted to throttle the air passing therethrough so as to increase the rotational velocity of the vortical flow 40.

While the outer wall 48 of the spin chamber 46 and the passage means 36 have been shown and described as being involute, and such is the preferred construction, it should be understood that other vortex generator or spin chamber and passage means configurations may be employed. For example, the spin chamber may be circular and the passage means may be adapted to deliver the inlet air in a tangential manner.

In order to maintain a generally uniform rotational velocity of the inlet air within the spin chamber 46, outwardly of the vanes 58, the outlet 38 and swirl vanes 58 are preferably positioned with respect to the outer wall 48 so that the cross sectional flow area between the outer wall 48 and the vanes 58 or opening 38 progressively decreases from the inlet 36 to the lip 54.

The apparatus 34 may be secured in the position of FIG. 1 by any suitable means, such as by welding to the snout assembly 26 and/or the hollow body 12 or by employing suitable bracketry (not shown).

In operation, liquid fuel 60 is delivered to inlet passage 36 through means 42. Some of this fuel is immediately vaporized and/or atomized and picked up by or entrained within the high velocity inlet air and carried into the combustion chamber 14. The remaining fuel lands on the interior surface of the inlet passage 36 and is driven or pushed by the high velocity inlet air into the spin chamber 46 and centrifugally along the outer wall 48. During such flow, a portion of the fuel may be vaporized and entrained within the inlet air flow. A portion of the fuel flow along outer wall 48 which is not so evaporated is then sheared off the lip 54, as at 62, and again passes across the high velocity, generally high temperature, inlet air flow which results in more fuel being vaporized and/or atomized and entrained within the inlet air. Since the inlet air from the compressor 28 may be at an elevated temperature of 700.degree. F. or higher, it will be appreciated that significant vaporization may occur during such flow through the vortex generator or spin chamber 46. In addition to the above and with reference to FIG. 4, it has been found that the liquid fuel circulating within spin chamber 46 is carried in a swirling flow along the inner surface of upstream wall 50 by the swirling air flow. This swirling flow liquid fuel is carried through vanes 58 and forms a ring of fuel 64 where the fuel velocity forces are balanced by the centrifugal forces. During such flow along the inner surface of upstream wall 50 to the ring 64, some of the fuel may be vaporized from the surface by the high temperature inlet air and by radiant heat from the flames within the combustion chamber 14. It has been found that the liquid fuel within the ring of fuel 64 is spun off and atomized into extremely small fuel droplets by the high velocity vortical flow of air 40 and directed toward the combustion chamber 14 as a generally conical spray 66. Since these atomized fuel droplets are extremely small, they quickly vaporize and mix with the air vortex 40.

Since the vortex core 56 is at a reduced pressure, a reverse or recirculation flow is established from the combustion chamber 14 into the apparatus 34 as generally shown by the flow arrows 68 in FIGS. 2 and 4. This recirculation of high temperature gas from the chamber 14 into the central or core portion of the spin chamber 46 further enhances vaporization of the liquid fuel from the spin chamber surfaces, as well as vaporization of any atomized fuel droplets carried by the intake air or the atomized droplets expelled from the fuel ring 64.

Since the outlet 38 is relatively large as compared, for example, with the discharge orifice of prior fuel spray atomizing nozzles of the well known type, the apparatus of this invention is relatively insensitive to tolerance variations in construction and to problems of deteriorated performance due to clogging by carbon or other deleterious matter. Additionally, since the apparatus of this invention utilizes the energy of the inlet air and does not relay on fuel pressure to effect its atomized spray, lower fuel delivery pressures and, consequently, simplified and more economical fuel delivery or distribution systems may be employed. It will also be noted that since the apparatus of this invention is positioned externally of and does not project into the combustion chamber 14, it is not subjected to the severe environmental stresses of the chamber 14 and, accordingly, may readily be adapted to yield long and reliable service life.

From the foregoing, it will be appreciated that the present invention provides compact and economical means for carbureting air or premixing air and fuel prior to introduction thereof into the primary zone of combustor and, hence, for delivery of the fuel into a combustion chamber in a highly effective and dispersed manner.

While an exemplary embodiment of this invention has been depicted and described as including an involute outer wall 48, involute passage means 36 for introducing air and fuel into spin chamber 46, and a circular array of swirl vanes 58, it should be understood that the swirl vanes 58 may be eliminated and other suitable geometrical housing and inlet passage constructions may be employed to generate the circulation of fuel and air about outlet 38 and the vortical flow discharge 66. Additionally, although the passage 36 has been shown as being adapted to deliver both the fuel and the air to the spin chamber 46, and while such is the preferred construction, separate passages may be employed. Accordingly, although one embodiment of the present invention has been depicted and described, it will be appreciated by those skilled in the art that many modifications, substitutions and changes may be made thereto without departing from the invention's fundamental theme.

Claims

What is claimed is:

1. A combustion apparatus including, in combination:

a hollow body defining a combustion chamber therein, said hollow body formed with an opening therein, and

a housing disposed outwardly of said combustion chamber, said housing including a downstream wall formed with an outlet of generally circular flow area in the fluid flow communication with said hollow body opening, an upstream wall facing said outlet, an involute outer wall extending between and joining said upstream and downstream walls so as to define a spin chamber internally of said housing and a generally tangential inlet to said spin chamber, an annular array of swirl vanes extending between said upstream and downstream walls around said outlet, and passage means in fluid flow connection with said tangential inlet for delivery of liquid fuel and air to said spin chamber at a point radially outwardly of said vanes.

2. The apparatus of claim 14 further characterized in that said passage means is formed with an upstream facing inlet for receiving a generally axially directed flow of air and includes one side wall formed as a generally streamline continuation of said involute outer wall.