Fuel Spray Ignition Atomizer Nozzle

Abstract

A liquid fuel spray atomizer nozzle for use with a gas turbine during combustion chamber fuel ignition, comprising a member having a high pressure air blast passageway for directing a stream of air, angularly in relation to the direction of fuel spray from a nozzle into the combustion chamber, so as to atomize and forcibly blow at least a part of the fuel toward an ignition device into ignition proximity therewith. The air blast can be blown directly across the fuel spray pattern or may be directed toward a side of the spray pattern. In all cases, the air must be under sufficient pressure to deflect and atomize the fuel spray sufficiently to provide for its ignition by the spark gap or other igniter.

Description

BACKGROUND OF THE INVENTION

This invention relates to gas turbine combustion chamber liquid fuel supply atomization and ignition during a starting operation.

In the past, it has been found that air atomization of a liquid fuel spray assists in assuring reliable starting of gas turbine combustion chambers. This has been done by directing a plurality of air blasts with the conventional conical liquid fuel spray pattern. The use of this type prior system requires a costly air compressor to supply the required air.

SUMMARY OF THE INVENTION

The present invention provides a simplified efficient liquid fuel spray atomizer nozzle for use in a gas turbine combustion chamber during starting by providing a single air blast stream which is directed at a part of the fuel spray so as to deflect it toward the igniter into igniting proximity therewith and concurrently atomizing it to assist the ready ignition thereof. The air blast may be blown directly across the fuel spray pattern or may be aimed to deflect a part from a side of the spray. This is conveniently done by providing a member with an air blast passageway having an orifice adjacent to the fuel spray nozzle orifice and extending angularly so as to direct the air blast in the desired direction. The air blast passageway also preferably is made with an initial throat which flares outwardly to the blast orifice in the form of a diverging mouth to provide for rapid expansion of the high pressure air at the orifice and a spreading of the air blast. Further, the air preferably is supplied at a pressure high enough to provide substantially sonic air velocity at the input throat, and the mouth flare is such as to reduce the orifice pressure to about 0.53 of the input pressure and result in a supersonic air velocity at the orifice.

The limited amount of air required for this air blast can readily be supplied from a suitable storage tank of relatively small size which can be pumped up to the needed pressure between starts by the existing conventional air compressor. It has been found that even if a separate air compressor is provided, it can be reduced in size to about an eighth that required by the prior art.

The foregoing and other advantages and features of novelty of this invention will be apparent from the following description referring to the accompany drawing.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING

In the drawing:

FIG. 1 is an axial sectional view of part of a gas turbine combustion chamber provided with one embodiment of a liquid fuel spray atomizer nozzle according to this invention;

FIG. 2 is an elevational end view of another embodiment of the spray atomizer member according to this invention;

FIG. 3 is a fragmentary sectional view along line 3-3 of the atomizing member shown in FIG. 2; and

FIG. 4 is a fragmentary sectional view through the air blast passageway in an atomizing member, on a fuel nozzle, showing details of the passage geometry to provide the maximum atomizing effect.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing, FIG. 1 illustrates the upstream end of a gas turbine combustion chamber 10 provided with a liquid fuel spray nozzle 11 incorporating the present invention. The combustion chamber is only partially shown as it may comprise any suitable type for generating hot pressurized products of combustion for operating a gas turbine (not shown).

The illustrated combustion chamber 10 is of the cannister type and includes a tubular body 12 with an upstream end wall 13 to which a suitable nozzle-mounting wall 14 is secured by suitable detachable means, such as bolts 15. The chamber body 12 is formed with a plurality of axially and circumferentially spaced apertures 16 for the passage of compressed air into the combustion chamber from the surrounding space in a suitable conventional plenum chamber, not shown. The liquid fuel spray nozzle 11 is supplied with fuel under pressure from a suitable source, not shown, through a conduit 17 connected to a fuel inlet passage 18 in a nozzle body 19. The pressurized liquid fuel is adapted to be sprayed by the nozzle 11 into the combustion chamber in a pattern which is a substantially hollow conical fuel spray pattern 20 at atmospheric pressure; however, since the combustion chamber is under pressure, both when starting up, due to the compressed air therein, and during normal operation, due to the additional pressure of the combustion gases formed therein, the full wide angle conical spray pattern 20 tends to contract to a narrower conical spray angle. Any suitable fuel directing structure can be used to provide the desired conical spray pattern, and, in FIG. 1, includes a small throat 21 connected to and forming the inner end portion of the fuel passage 18 and terminates in an outwardly flaring mouth 22 which defines the spraying orifice of the nozzle.

It has been found that if the liquid fuel spray is finely atomized, it will ignite much more readily in intiating combustion in the combustion chamber. In addition, the normal spray angle pattern 20 does not spray fuel near enough to an igniter, such as a spark plug 23, to allow ignition of the fuel. According to this invention, a simplified and efficient atomizing of some of the fuel during starting and deflecting of at least a portion thereof into igniting proximity with the igniter 23 is provided by directing a single air blast at very high, preferably supersonic, velocity at a part of the fuel spray pattern 20 so as to atomize and blow it in the desired direction. In the FIG. 1 embodiment, this is conveniently done by providing a jet of high velocity air through an atomizing orifice 24 in a face plate 25 having an air-tight seat on the inner end of the nozzle body 19.

The desired supply of air for the atomizing air jet and a rigid air-tight assembly of the nozzle structure may readily be provided by forming the face plate 25 with a central frusto-conical seat 26 snugly fitted over a complementary frusto-conical face 27 on the inner end of the nozzle body 19 around the spraying orifice 22, and providing an enclosing air supply means for rigidly securing these in air-tight relationship. In the FIG. 1 structure, this is obtained by press fitting or otherwise suitably mounting a sleeve 28 around the nozzle body 19 and providing an air-tight seat of this sleeve 28 with a flange 29 on the nozzle body 19. This sleeve 28 is mounted in a central aperture in the mounting wall 14 and is secured in position in any suitable manner, as by bolts 30 extending through a sleeve flange 31 and the wall 14. The face plate is drawn onto its air-tight seat with the nozzle body by an enclosing cap 32. In this embodiment, the cap is formed with an inwardly extending lip 33 which engages a complementary circumferentially extending flange 34 on the outer edge of the face plate 25, and has a threaded engagement 35 with the adjacent end of the sleeve 28. The sleeve 28 is made shorter than the length of the nozzle body from the flange 29 to the conical face 27, thereby providing a space 36 between the end of the sleeve 28 and the adjacent side of the face plate 25, whereby tightening of the cap 32 threaded engagement 35 on the sleeve 28 draws the complete nozzle assembly into a rigid air-tight unit.

Air is supplied to the atomizing orifice 24 from a suitable source, such as a small tank 37, through a conduit 38-39 and a control valve 40. The conduit is connected to a passageway 41 in the sleeve 28, which passageway 41 opens into the space 36 between the end of the sleeve and the face plate 25.

In order to provide the desired air blast deflection of part of the liquid fuel from the conical fuel spray pattern 20 toward the igniter 23, the face plate 25 is formed with a passageway 42 extending substantially radially therethrough and at an angle between the faces thereof so as to direct an air blast from the orifice 24 angularly in the general fuel spray direction directly at and across the conical fuel spray pattern 20 toward the igniter 23. This air blast operation is controlled by the valve 40, and is made operative by opening the valve during the starting ignition of fuel in the combustion chamber, whereby part of the fuel pattern is atomized and at least a part 43 thereof is deflected to igniting proximity with the igniter 23. After the fuel has ignited, the valve 40 is closed, rendering the air blast atomizer inoperative. Thus, only a relatively small amount of air is required for a short time to provide this efficient ignition atomization and deflection of the fuel, and the small air storage pressure tank 37 can be pumped up between starts by the conventional air compressor or, if need be, by a relatively small auxiliary compressor. If desired, the valve 40 may be a suitable conventional electromagnetic type valve, which may be energized to open position when the igniter 23 is energized and deenergized to closed position at other times to thereby provide the desired air blast control.

FIGS. 2 and 3 illustrate another embodiment of the present invention in a modified air blast nozzle atomizer structure. Similar parts are indicated by the same reference numbers as in FIG. 1. In this embodiment, the general nozzle structure may be the same as in FIG. 1, wherein the nozzle body 19 terminates in a frusto-conical face 27 around an outwardly flared mouth 22 forming the fuel spray orifice connected to the fuel supply passage throat 21. The face plate 25 is mounted on the nozzle in the same manner as in FIG. 1 and is provided with an air blast passageway 50 between the faces thereof so as to direct an air blast angularly in the general fuel spray direction, but instead of being directed across the fuel spray pattern, it has an orifice 51 directed to engage a side of the conical spray pattern, whereby the air blast will deflect a part of the fuel spray toward the igniter 23 and concurrently atomize this deflected spray. In some cases, this almost tangential spray deflection blast may be advantageous because of the pressures involved or because of the relative placements of certain parts, such as the igniter 23.

FIG. 4 illustrates another embodiment of the nozzle atomizer structure which may be incorporated in either the FIG. 1 or the FIGS. 2 and 3 type atomizer face plates. Similar parts are identified by the same reference numbers as in the other figures. The additional feature in this embodiment over the previously described nozzles is the geometry of the atomizing passageway 59 in the face plate 25, the remainder of the structure being the same as that previously described.

In all embodiments, it is desirable that the pressure of the air at the intake to the face plate atomizing passageway be sufficient to give the air entering the passageway about sonic velocity in order for it to produce the desired results. The FIG. 4 passageway 59 is formed with an intake throat 60 of relatively small cross-sectional area into which the air passes at about sonic velocity under the correct pressure. This passageway throat opens abruptly into a diverging mouth 61 of much larger cross-sectional area to the atomizing air blast orifice 62, so proportioned that the rapid expansion of the air therethrough provides for a drop of the orifice air pressure to about 0.53 of the air pressure in the input throat 60. This provides a critical pressure drop which produces a supersonic air velocity at the air blast orifice 62, which has been found to improve greatly the fuel atomizing effect of the blast and also provides a broadening of the air jet with a consequent improvement in the efficiency of the starting ignition of the fuel.

While particular embodiments of this invention have been illustrated and described, many modifications thereof will occur to those skilled in the art. It is to be understood, therefore, that the invention is not to be limited to the exact details disclosed but only as required by the prior art.

Claims

The invention claimed is:

1. Combustion apparatus for a gas turbine, comprising

a combustion chamber,

a liquid fuel spray atomizer nozzle for atomizing liquid fuel sprayed into said combustion chamber,

said spray nozzle having a body defining a spraying orifice,

said body having fuel passage means for directing the liquid fuel through said orifice in a substantially hollow conical spray pattern at atmospheric pressure,

a fuel ignition device, and

means for providing an air blast directed at said fuel spray pattern from only one side thereof for atomizing at least a part of the liquid fuel forming said spray pattern and directing at least a part thereof into igniting proximity with said ignition device.

2. Combustion apparatus as defined in claim 1 wherein said air blast means includes means for controlling the operation thereof.

3. Combustion apparatus as defined in claim 2 wherein said controlling means is operative to render said air blast means operative during starting ignition of fuel in the combustion chamber and for rendering it otherwise inoperative.

4. Combustion apparatus as defined in claim 1 wherein said air blast means comprises a member having therein an air passageway with a blast orifice and constructed and arranged to direct an air blast to engage at least a part of said fuel spray pattern and to atomize the same and deflect at least a part of the atomized spray toward said ignition device into igniting proximity therewith.

5. Combustion apparatus as defined in claim 4 wherein said air blast passageway is constructed and arranged to direct an air blast directly at and across the conical fuel spray pattern toward said ignition device.

6. Combustion apparatus as defined in claim 4 wherein said air blast passageway orifice is closely adjacent to said spray nozzle orifice and said passageway is arranged to direct the air blast angularly in the general fuel spray direction and across the same.

7. Combustion apparatus as defined in claim 4 wherein said air blast passageway is constructed and arranged to direct an air blast angularly in the general fuel spray direction and so as to engage a side of said conical spray pattern and atomize and deflect at least part of the atomized fuel spray toward said ignition device.

8. Combustion apparatus as defined in claim 4 wherein the air blast passageway has an input throat and a diverging mouth of larger cross-sectional flow area than said throat forming said blast orifice and providing for rapid expansion of air at the orifice and a spreading of the air blast.

9. Combustion apparatus as defined in claim 4 including means for supplying air to said air blast means at a pressure to provide substantially sonic air velocity at the input to said air blast passageway.

10. Combustion apparatus as defined in claim 9 wherein the air blast passageway has an input throat and a diverging mouth forming said air blast orifice,

said diverging mouth being formed to provide a critical air pressure drop therethrough with a change in air pressure to about 0.53 of the air pressure in the input throat and a resultant supersonic air velocity at the air blast orifice.