US 3638865 A
A fuel spray nozzle for delivery of a conical spray of fuel droplets into a gas turbine engine combustion apparatus includes a shrouded and shielded discharge head arranged to establish a stable fuel spray angle, maintain low-operating temperatures and prevent accumulations of deleterious matter on the surfaces of the nozzle which are exposed to the combustion process.
Description (OCR text may contain errors)
United States Patent McEneny et al.
 FUEL SPRAY NOZZLE  Inventors: Gregory E. McEneny; Edward E. Ekstedt,
both of Cincinnati, Ohio  Assignee: General Electric Company  Filed: Aug. 31, 1970 ] Appl. No.: 68,194
[4 Feb. 11,1972
3,028,l02 4/1962 Davies et al. ..239/404 3,029,029 4/1962 Webster .239/404 3,520,480 7/1970 Halvorsen ..239/424 X  US. Cl ..239/424, 239/404  ABSTRACT  Int. Cl ..B05b 7/06  Field ofSearch ..239/404,4l6.5,417.5,418, A fuel SPmy "Mlle dellvery a sPray of fuel 239/422 423 424 426 427 3 427 5 428 433 droplets into a gas turbine engine combustion apparatus in- 3 cludes a shrouded and shielded discharge head arranged to establish a stable fuel spray angle, maintain low-operating temperatures and prevent accumulations of deleterious matter  References cued on the surfaces of the nozzle which are exposed to the com- UNITED STATES PATENTS bustion P 3,013,732 12/1961 Webster et al ..239/404 5 Claims, 2 Drawing Figures .54 m0 fZ .i if
i 24 h w M 73 7 l; ea /V M PATENTEU FEB 1 I972 GREGORY E. MCENENY EDWARD E. E'KSTEDT FUEL SPRAY NOZZLE This invention relates to fuel spray nozzles and, more particularly, to improvements therein which are particularly ap plicable to spray nozzles used in gas turbine engines. The invention herein described was made in the course of or under a contract, or a subcontract thereunder, with the US. Department of the Air Force.
Gas turbine engines commonly employ fuel spray nozzles for delivery of a single cone or dual concentric cones of fuel droplets into the engine combustion apparatus. Each fuel spray nozzle generally includes an axially extending discharge head which is formed with a single orifice or dual concentric orifices and projects through an upstream wall of the apparatus and into the combustion chamber. In such applications, the fuel nozzle discharge head is exposed to the extremely high temperatures, pressure variations and recirculation flows of the combustion apparatus, the combination of which may result in the deposition of fuel particles and the formation of carbon or coke on the exposed surfaces of the discharge head. To the end of preventing such deposition or accumulation, it has been the practice to provide an air shroud for directing a sweeping flow of compressor pressurized air over the exposed surfaces of the discharge head. In high pressure ratio engines, however, the air available for such purposes may be at high temperature, making it desirable that the discharge head be insulated therefrom. Additionally, such prior shroud arrangements, while in most cases effectively preventing accumulations in the immediate vicinity of the discharge orifice or orifices, tend to accumulate carbon or coke on the exposed surfaces of the shroud itself.
A further problem in shroud arrangements used heretofore is found in the fragile nature of the fuel spray cone and its susceptibility to being closed down or narrowed by the shroud airflow. When this occurs, overrich fuel pockets may develop and cause visible smoke in the products of combustion.
A primary object of this invention is a fuel spray nozzle discharge head which overcomes the foregoing problems.
A further object of the present invention is a fuel spray nozzle discharge head having low operating temperature characteristics.
Another object of this invention is a low temperature fuel nozzle discharge head which includes means for sweeping all surfaces exposed to the combustion process so as to prevent coke or carbon accumulation thereon.
A still further object is a heat shield arrangement for the discharge head of a fuel spray nozzle which permits unrestrained relative thermal growth between the shield and the discharge head.
Yet another object of this invention is an insulated fuel nozzle discharge head which is adapted to deliver a conical fuel spray, of stable and predictable apex angle, and wash all surfaces exposed to the combustion process with either fuel or air.
Briefly stated, the above and other objects and advantages of the present invention are achieved by forming an annular, axially extending support surface on the outer periphery of the discharge head, adjacent its downstream end. An annular shield is telescoped over the head and defines an annular insulating airspace therebetween and intermediate the ends of the shield. The upstream end of the shield is rigidly connected to the head while the downstream end extends into close fitting engagement with the head support surface so as to close the downstream end of the airspace and permit unrestrained relative axial movement between the head and the shield so as to accommodate differential thermal growth or shrinkage during engine operation. An annular shroud is connected at its upstream end in telescoping relationship to the shield and the head and defines, in cooperation with the shield and the head, an annular, generally axially extending air passage. The discharge head is formed with an annular orifice of small axial extent which terminates in a downstream opening, frustoconical guide surface which extends to the downstream end of the head. The outer peripheral surface of the head is flared to its downstream end to define a relatively sharp downstream edge in cooperation with the guide surface. The inner surface of the shroud is flared to its downstream end and defines a divergent outlet for the shroud air passage for delivery of shroud air as a hollow cone about the fuel spray in close parallel proximity thereto. A plurality of peripherally spaced, axially extending ribs project radially from the outer peripheral surface of the shroud to space the shroud from the combustion apparatus wall member through which it projects so as to provide means for establishing a film flow along such surface. The shroud outer peripheral surface converges to its downstream end, preferably in a streamline arcuate manner, and defines, in cooperation with the flared inner surface, a downstream edge of small radial extent whereby the film flow is efficiently directed to the downstream shroud edge without separation. The exposed external surfaces of the shroud are minimized and the downstream end of the head is protected by terminating the shroud in a plane downstream of and closely spaced to that of the downstream end of the head. The radial extent of the ribs is small relative to the radial extent of the shroud air passage so that the air efflux from the latter will turn the film at the downstream edge of the shroud and prevent the film from closing down the fuel spray angle.
While the specification concludes with claims particularly pointing out the novel aspects of the present invention, it is believed the invention will be better understood upon reading the following description of the preferred embodiment in conjunction with the accompanying drawings, wherein:
FIG. 1 is a partial cross-sectional view of a gas turbine engine employing the improved fuel spray nozzle of this invention; and
FIG. 2 is an enlarged partial cross-sectional view of the discharge end of the fuel nozzle of FIG. 1.
With reference now to FIG. 1 of the drawings, a continuousburning 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 is formed with a domed upstream end 16 and may be annular, cylindrical or a combination thereof.
In the annular configuration, the domed end 16 is formed with a plurality of circumferentially spaced openings 18, each respectively communicating with a suitable conduit 20 adapted to deliver into chamber 14 at least a portion of the air required to burn the fuel and dilute the gaseous products of combustion. The conduit 20 is secured to the hollow body 12 at 22, as by welding or other suitable means, and extends upstream of the opening 18 and terminates in a radial flange 24.
The hollow body 12 may be formed with a plurality of cooling air passages 26 adapted to deliver a protective boundary layer ofcooling air along the inner surfaces of the hollow body and a plurality of dilution holes 28 for delivery of the remaining portion of the required combustion and dilution air.
The hollow body 12 may be enclosed by a suitable shell 30 having an upstream end passage 32 communicating with a source of compressed air, as for example the discharge end of a gas turbine engine compressor.
An annular snout assembly 34 may be employed to direct the compressed air from passage 32 to the opening 18, to the cooling air passages 26 and to the dilution air passages 28. The snout assembly 34 is secured to the hollow body 12 and extends upstream thereof, defining a chamber 36 and a passage 38 for delivery of compressed air thereto.
The outer shell 30 is sized in relation to the snout assembly 34 and hollow body 12 so as to define annular passages 40 and 42 therebetween which function, in part, to deliver compressed air from passage 32 to cooling and dilution air passages 26 and 28.
A fuel spray nozzle 44 is provided for each hollow body opening 18 and includes an inlet 45 for connection with a source of pressurized fuel and a discharge end 46 for delivery of dual concentric, generally hollow conical sprays of fuel droplets, as at 48 and 49, about fuel spray axis 51. Each spray nozzle 44 is suitably secured to shell 30, as at 50, and extends inwardly through the shell 30 and the snout assembly 34, terminating at discharge end 46. A suitable member 52 is connected to the flange 24 to close the upstream end of conduit and combustion chamber 14. The discharge end 46 extends into the combustion chamber 14 through an opening 54 formed in the combustion apparatus closure member 52.
Referring now to FIG. 2, the discharge end 46 of fuel spray nozzle 44 has been shown as comprising a main body portion 56, a discharge head 58, a shield 60, a shroud 62, and primary and secondary plugs 64 and 67.
The main body 56 is formed with a primary passage 57 for delivery of pressurized fuel from inlet 45 to plug 64, which includes a plurality of peripherally spaced, axial swirl slots 66 for imparting a swirling motion to the fuel prior to discharge through a primary orifice 68 which generates the primary fuel spray cone 49. In a like manner, the main body 56 is formed with a secondary passage 70 for delivery of pressurized fuel to a plurality of spaced, radial swirl slots 72 which are defined by the secondary plug 67 in cooperation with the discharge head 58. The swirling fuel from slots 72 is directed to a secondary orifice 74 which is formed in the discharge head 58 and is of relatively small axial extent. The orifice 74 terminates in a downstream opening, frustoconical guide surface 76 which extends to the downstream end 78 of the discharge head and directs the swirling fuel effluxing from orifice 74 to end 78 as an attached conical fuel film having an apex angle generally equal to the desired spray or apex angle ofspray 48.
The head includes an upstream tubular portion 80 which telescopes over the main body portion 56 and is connected thereto, preferably at a location outside the chamber 14 and upstream of the closure member 52, as by welding, threaded engagement or other suitable means.
The outer peripheral surface of the discharge head 58 is flared, as at 82, to its downstream end 78 so as to define a downstream edge which is relatively sharp or of small radial extent to thereby minimize the possibility of collecting carbon or coke thereon. By way of example, it has been found that a radial height of between 0.015 and 0.025 inches on an inner diameter of approximately one-half inch provides satisfactory operation.
The shield 60 has been shown as being generally annular and telescoped over the head 58 so as to define an annular air space 84 which extends axially along a substantial portion of the outer boundary of the head to insulate the head from the high temperature fluid passing therearound. The shield is connected to the head at its upstream end by welding, as at 86, by brazing or by other suitable means.
The downstream end of the shield 60 extends into closefitting sliding relationship with an axially extending, annular support surface 88 which is formed on the outer peripheral surface of the head 58, adjacent its downstream end 78. In this manner, a closure is provided for the downstream end of the insulating airspace 84 and unrestrained relative thermal growth and contraction between the head and the shield is accommodated.
The shroud 62 is telescoped over the head 58 and shield 60 and radially spaced therefrom so as to define a generally axially extending, annular air passage 90 therebetween for receiving compressor pressurized air from chamber 36 and directing same into the chamber 14. The shroud is connected to the shield adjacent its upstream end, through a plurality of circumferentially spaced ribs 92 which may be carried by either the shield or the shroud.
The inner surface of the shroud is flared, as at 94, to its downstream end 96 and defines, in cooperation with the flared portion 82 of the head, a divergent outlet 98 for effluxing shroud airflow in the form of a hollow conical stream about and along the fuel spray 48. The apex angle of the conical shroud efflux is approximately equal to the desired spray angle of fuel cone 48 so as to stabilize the fuel cone in the vicinity of the fuel nozzle and effectively shield it from any disruptive pressure variations and reverse flows in the chamber l4.
The shroud 62 includes a plurality of peripherally spaced, axially extending ribs 100, of small radial extent relative to the radial height of shroud air passage 90, which maintain the outer surface 102 of the shroud centrally spaced from the closure member opening 54 and establish a flow, in the form of a thin film, from chamber 36 along the exposed outer surface 102 of the shroud. The shroud outer surface 102 is tapered as at 104, preferably in a streamline arcuate manner, to its downstream end 96 to minimize the radial extent of the downstream edge 96 and, at the same time, efficiently direct the film flow to the downstream end of the shroud.
By making the ribs 100 of small radial extent relative to the radial height of shroud air passage 90, the film flow is suffcient to sweep surface 102 and prevent any carbon and coke accumulations thereon, but is weak enough to merge with and be turned by the relatively stronger shroud airflow at downstream end of the shroud without affecting the spray angle of the fuel cone 48. By way of example, a shroud rib radial height of about 0.015 inches, from an outer shroud surface diameter of about 0.75 inches, with a shroud air passage radial height of approximately 0.045 inches has been found to provide satisfactory sweeping without adverse affect to the fuel spray angle.
As shown in FIG. 2, the downstream shroud edge 96 resides in a plane parallel to and closely spaced downstream (for example, 0.005 to 0.015 inch) of the plane of the head downstream end 78. In this manner, the surface area of the shroud which is exposed to the combustion process is minimized and protection to the edge 78 during handling is provided.
By interconnecting the head 58, the shield 60 and the shroud 62 only at their upstream ends and at a location spaced from the high temperatures of the combustion chamber 14, unrestrained relative thermal growth or contraction between such components is accommodated and high stresses in the connecting joints are prevented.
Since the fuel from passage 57 is at a relatively low temperature compared to the temperature of the air within chamber 36 and the combustion temperatures within chamber 14, relatively low operating temperatures are maintained in the head 58 by the fuel flow therethrough and along guide surface 76, coupled with the thermal resistance of insulating airspace 84.
From the foregoing, it will be noted that the present invention provides a fuel spray nozzle discharge head, having a stable and predictable fuel spray angle, in which all surfaces exposed to the combustion process are washed with either air or fuel to thereby prevent accumulation of coke and carbon and maintain low operating temperatures in the discharge head.
While the invention has been depicted and described in connection with a so-called dual spray nozzle, it will be understood that the primary orifice 68 and plug 64 may be eliminated. Additionally, while a particular arrangement for swirling the primary and secondary fuel flows, using the primary and secondary plugs 64 and 67, has been shown, numerous other arrangements which are well known in the art may be used to generate such swirl.
While one embodiment has been depicted and described, such embodiment is intended to be exemplary only and not definitive and it will be appreciated that many substitutions, modifications and variations may be made thereto without departing from the fundamental theme of the invention.
What is claimed is:
l. A fuel spray nozzle comprising a main body having an inlet for receiving pressurized fuel and a discharge head formed with an orifice and adapted to discharge at least one generally hollow conical spray of fuel droplets at a predetermined spray angle into a gas turbine engine combustion apparatus, an annular, axially extending support surface formed on the outer periphery of said head adjacent its downstream end, an annular shield having an upstream end and a downstream end, said shield telescoped over said head and defining, in cooperation therewith, an annular, axially extending insulating airspace therebetween, with the upstream end of said shield connected to said head and the downstream end of said shield extending into close-fitting engagement with said head support surface to close said airspace at its downstream end and to permit unrestrained relative axial movement between said head and said shield, an annular shroud telescoped over said head and secured to said shield in radial spaced relationship thereto and defining, in cooperation with said shield and said head, an annular, generally axially extending air passage for directing fluid flow along the exposed outer surfaces of said shield and said head, said shroud includes a plurality of peripherally spaced, generally axially extending ribs projecting radially outwardly from the outer peripheral surface of said shroud, said ribs adapted to be slidingly received within an opening of said combustion apparatus and define, between said outer surface and said opening, a space for directing a film of fluid along said outer surface to prevent accumulation of deleterious matter thereon, said outer shroud surface being tapered to its downstream end.
2. The fuel spray nozzle of claim 1 further characterized in that said orifice terminates in a downstream opening, frustoconical guide surface having an apex angle approximately equal to said predetermined spray angle, said guide surface being of substantial axial length relative to the axial length of said orifice and extending to the downstream end of said discharge head, said discharge head formed with a divergently flared outer surface which defines, in cooperation with said guide surface, a sharp downstream edge for said discharge head, the inner surface of said shroud being flared at its downstream end so as to define, in cooperation with the flared outer surface of said discharge head, a divergent annular outlet for effluxing air from said air passage in close parallel proximity to the desired course of fuel droplets from said nozzle, the outer peripheral surface of said shroud converging to its downstream end so as to define, in cooperation with said flared inner surface, a generally downstream edge for said shroud.
3. The fuel spray nozzle of claim 2 further characterized in that the downstream end of said shroud and the downstream end of said head reside in closely spaced planes normal to said spray axis.
4. The fuel spray nozzle of claim 2 further characterized in that said convergent shroud surface is arcuate so as to establish a generally streamline flow of said fluid film therealong, the radial height of said ribs being substantially less than the radial depth of said shroud air passage, whereby said film merges with the conical flow from said divergent outlet without affecting the fuel spray angle.
5. In a gas turbine engine combustion apparatus of the type including a hollow body defining a combustion chamber therein, an upstream closure for said combustion chamber, and a fuel spray nozzle having a discharge head projecting into said combustion chamber through an opening in said upstream closure, said fuel spray nozzle including a main body having an inlet for receiving pressurized fuel, the improvement comprising:
said discharge head formed with an orifice terminating in a downstream opening, frustoconical guide surface which extends to the downstream end of said discharge head for delivery of a generally hollow conical spray of fuel droplets into said combustion chamber, the outer peripheral surface of said discharge head being divergently flared to its downstream end, to define a sharp edge at the downstream end of the head and including an axially extending, annular guide surface, an annular shield having an upstream end fixedly connected to said discharge head, upstream of said combustion chamber, and a downstream end extending into close-fitting, sliding engagement with said guide surface, said shield defining an annular airspace intermediate its ends and about said discharge head, an annular shroud telescoped over said discharge head and said shield and defining an annular, generally axially extending air passage therebetween, said shroud having an upstream end fixedly connected upstream of san combustion chamber, to said shield, and a downstream end residing in a plane closely spaced downstream of said discharge head downstream end, said shroud including a plurality of peripherally spaced radial ribs slidably received in said closure opening and defining a small passage between the outer periphery of said shroud and said closure opening, with the inner surface of said shroud being divergently flared to its downstream end and the outer peripheral surface of said shroud being convergently tapered to its downstream end, whereby all surfaces of said fuel nozzle exposed to the combustion chamber are washed with either fuel or air without adverse effect to the fuel spray angle and low operating temperatures are maintained in said discharge head.