Patent Application
20180195728
This application is based upon and claims the benefit from priority British Patent Application No. 1700459.9 filed 11 Jan. 2017, British Patent Application No. 1700465.6 filed 11 Jan. 2017, and British Patent Application No. 1705002.2 filed 29 Mar. 2017, the entire contents of each of which are incorporated herein.
The present invention concerns fuel injectors used for providing fuel to the combustion chamber of a gas turbine engine. More particularly, the fuel injector is of a jet-in-crossflow type.
In a gas turbine engine, fuel is mixed with air prior to delivery into a combustion chamber where the mixture is ignited. Arrangements for mixing the fuel and air vary. In prefilming arrangements, fuel is formed in a film along a prefilmer surface adjacent to a nozzle. Pressurised, turbulent air streams are directed against the prefilmer surface and serve to shear fuel from the surface and mix the sheared fuel into the turbulent air streams. In vaporiser designs fuel is forced through a small orifice into a more cavernous air filled chamber. The sudden pressure drop and acceleration of the fuel flow upon entering the chamber disperses the fuel into a spray. High temperatures subsequently vaporise the fuel. Turbulent air flows in the chamber again encourage mixing.
Both methods have associated advantages and disadvantages. Prefilming fuel injectors have highly complex and intricate designs that are expensive to manufacture. Design iterations are slow, due to complexity of the manufacturing process. Whilst relatively simple in design and generally cheaper in manufacture, vaporiser fuel injectors provide inferior fuel preparation when compared to prefilming fuel injectors thereby resulting in inferior engine performance.
Jet in crossflow is an air blast technique wherein the energy for atomisation is primarily provided by an airstream encountered by a fuel jet. The fuel is rapidly distributed over a range of radii, giving an opportunity for improved fuel/air mixing; and the mechanical design of the injector is simpler, permitting a reduction in manufacturing cost. A fuel passage is arranged centrally of an annular air swirler. Air flows generally from upstream to downstream in a direction substantially parallel with the fuel passage. The swirler imparts a spin on the air such that it spirals through the air swirler. One or more outlets of the fuel passage are arranged inclined to the flow direction of swirled air passing the outlet. The outlet is configured to deliver the fuel as a jet which crosses the swirled air flow. Walls of the swirler passages in the air swirler may be radially convergent in a manner which directs the exiting air flow towards the fuel passage outlet to encourage mixing of the fuel and air in the outlet chamber and minimise filming of fuel on walls of the air swirler. The radially convergent passages accelerate the air flow providing more kinetic energy to act upon the fuel and improve atomisation. The configuration ensures maximal atomisation of the fuel as it joins the relatively high velocity air stream.
In accordance with the invention there is provided a fuel injector comprising; at least one elongate fuel passage having an elongate axis extending from an upstream inlet end to a downstream outlet end;
Optionally the bridge is further supported by an axially extending support beam, the axially extending support beam extending axially from the centre of the bridge and in line with the elongate axis. An opposite end of the support beam may be joined with a wall of the fuel passage which extends substantially orthogonally to the elongate axis. The support beam may have an aerodynamic cross-section shape.
The arms of the bridge may extend both radially and axially, that is, they are not orthogonal to the elongate axis. The arms may form an apex at the centre, the apex being a point on the elongate access and in axial alignment with a centre of the nose. Alternatively, the arms may meet at a planar apex on the centre.
The fuel injector may further comprise a second annular cavity defined by an annular outer wall extending from downstream of the outlet end to a position upstream of the one or more outlets, the annular outer wall being convergent at a downstream end whereby to define an orifice centred nominally coincident with the elongate axis, the second annular cavity having a second annular cavity inlet at an upstream end and wherein the fuel passage outlets emerge at a radially outer surface of the annular outer wall.
The inner and outer skin may meet adjacently upstream of the one or more outlets.
In use, a stream of non-swirling air enters the second annular cavity inlet, passes over the fuel passage and exits at the orifice. The convergent end of the annular outer wall turns the annular air flow into a single jet of air.
Preferably the fuel passage has a plurality of outlets. The outlets are arranged obliquely with respect to the elongate axis and are directed radially outwards and in a downstream direction. The outlets may be inclined in a circumferential and/or axial direction. The plurality of outlets may be arranged in an annular array nominally centred on the elongate axis. The plurality of outlets may be equally spaced from each other. For example, the plurality of outlets may comprise 5 to 15, or more particularly 7 to 11 equally spaced outlets arranged in an annular array. The outlets may sit between adjacent arms of the bridge. Optionally the arms of the bridge are shaped to guide flow of fuel efficiently from the elongate fuel passage towards the outlets.
The annular outer wall may comprise an array of slots arranged to receive an array of fuel passage outlets. For example, the slots may extend in-line with the elongate axis. Alternatively, the annular outer wall may comprise an array of holes through which the outlets may be arranged to protrude. The annular outer wall may form part of an annular air swirler which surrounds the fuel passage.
Multiple fuel passages may be arranged, in use, to provide staged fuel staging within the injector.
The nose section may extend downstream of the fuel passage outlets. The nose section may be convergent towards the downstream end. For example the nose portion is cone shaped. The end of the nose portion may be arranged slightly upstream of the orifice.
In use, the fuel injector may be arranged nominally centrally of an annular air swirler to form a fuel spray nozzle. The annular air swirler may optionally be attached to the fuel injector, alternatively the air swirler is supported by a separate component such that it floats around the fuel injector. In such a configuration a spherical section may be incorporated into the outer surface of the injector where it interfaces with a cylindrical section of the air swirler or seal in order to accommodate axial and angular movement of the injector relative to the air swirler or seal. Radial displacement may be accommodated by a floating seal arrangement.
Such a fuel spray nozzle may comprise a component of a gas turbine engine. Optionally the fuel spray nozzle is one of a plurality of fuel injectors in the gas turbine engine. A plurality of fuel spray nozzles may be arranged in an annular array around an engine axis of a gas turbine engine.
Some embodiments of the invention will now be further described with reference to the accompanying Figures in which;
A cone shaped nose 31 of the fuel injector projects towards the outlet 40b to assist in directing air from the open ended annular cavity towards the outlet 40b where it is shaped to form a single jet.
An annular air swirler 34 (shown in outline only) typically mounted to the combustor (not shown) sits around the injector 26. The injector 36 is joined to a double skinned fuel feed tube 35, 35a by welds W1 and W2.
In use fuel is delivered through fuel passage 38 and exits through outlets 38a. The outlets 38a are directed so as to project fuel across an air flow path which passes over the outer wall 40a and through air swirler 34. Annular heatshield cavity 39 is closed at the injector outlet end and contains air to insulate the fuel passage 38. In contrast, annular cavity 40 is open at the injector outlet end and a continuous stream of air is channelled through this annular cavity 40 and out through the air outlet 40b which sits just downstream of the cone shaped nose 31. The converging outer wall 40a of cavity 40 and the cone shaped nose 31 together create a single jet of air at the outlet 40b. The outer wall 40a includes an array of holes 40c which encircle protruding fuel outlets 38a. Some air from the annular cavity 40 thus exits through these holes 40c insulating the outlets 38a and providing an air film that may prevent the build-up of fuel in this region reducing the incidence of local coke formation.
The gas turbine engine 610 works in the conventional manner so that air entering the intake 612 is accelerated by the fan 613 to produce two air flows: a first air flow into the high-pressure compressor 614 and a second air flow which passes through a bypass duct 621 to provide propulsive thrust. The high-pressure compressor 614 compresses the air flow directed into it before delivering that air to the combustion equipment 615.
In the combustion equipment 615 the air flow is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high and low-pressure turbines 616, 617 before being exhausted through the nozzle 18 to provide additional propulsive thrust. The high 616 and low 617 pressure turbines drive respectively the high pressure compressor 614 and the fan 613, each by suitable interconnecting shaft. An array of fuel injectors in accordance with the invention may conveniently be provided at an inlet end of the combustion equipment 615.
Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. three) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.
The second swirler portion 66 comprises a plurality of vanes 84 and a third member 86. The third member 86 is arranged coaxially around the second member 74. The vanes 84 of the second swirler 66 extend radially between the second and third members 74 and 86. The vanes 84 of the second swirler portion 66 have leading edges 88 and the third member 86 has an upstream end 90. The leading edges 88 of the vanes 84 of the second swirler portion 66 extend with radial and axial components from the upstream end 78 of the second member 74 to the upstream end 90 of the third member 86 and the radially outer ends 92 of the leading edges 88 of the vanes 84 of the second swirler portion 66 form arches 94 with the upstream end 90 of the third member 86. In particular the leading edges 88 of the vanes 84 extend with axial downstream components from the upstream end 78 of the second member 74 to the upstream end 90 of the third member 86.
The first member 72, the second member 74 and the third member 86 are generally annular members with a common axis Y. Thus, the upstream end of the first member 72 is upstream of the upstream end 78 of the second member 74 and the upstream end 78 of the second member 74 is upstream of the upstream end 90 of the third member 86.
The outer surface of the downstream end of the first member 72 tapers/converges towards the axis Y of the fuel injector head 60. The first member 72 The downstream end of the second member 74 tapers/converges towards the axis Y of the fuel injector head 60 and the inner surface of the downstream end of the third member 86 initially tapers/converges towards the axis Y of the fuel injector head 60 and then diverges away from the axis Y of the fuel injector head 60. An annular passage 104 is defined between the first member 72 and the second member 74 and an annular passage 106 is defined between the second member 74 and the third member 86. A central passage 108 is defined within the first member 74 in which a fuel passage can be received in accordance with the invention.
It is seen that the fuel injector head 60 is arranged such that the leading edges 76 and 88 of the vanes 70 and 84 respectively are arranged to extend with axial downstream components from the first member 72 to the upstream end 78 of the second member 74 and from the second member 74 to the upstream end 90 of the third member 86 respectively. In addition it is seen that the fuel injector head 60 is arranged such that the radially outer ends 80 and 92 of the leading edges 76 and 88 of the vanes 70 and 84 respectively form arches 82 and 94 with the upstream ends 78 and 90 of the second and third member 74 and 86 respectively. These features enable the fuel injector head 60 and in particular the first and second swirler sections 64 and 66 of the fuel injector head 60 to be manufactured by direct laser deposition. These features enable the vanes 70 of the first swirler 64 to provide support between the first member 72 and the second member 74 and the vanes 84 of the second swirler 66 to provide support between the second member 74 and the third member 86 during the direct laser deposition process.
In use fuel is delivered through fuel passage 802 and exits through outlets 803. The outlets 803 are directed so as to project fuel across an air flow path which passes over the outer wall 806 and through an air swirler (not shown). Annular heatshield cavity 804 optionally extends past the fuel outlets through a plurality of circumferentially disconnected passages to a tip 813. The cavity 804 is closed at the injector downstream tip by the nose 808. The cavity 804 contains air to insulate the fuel passage 802 from air that surrounds it. In particular, the cavity 804 at the tip 813 shields the fuel gallery from heat that is transmitted via radiation from the combustion zone (not shown) towards the nose 808. The sizes of the passages that pass between the fuel outlets 803 and connect with the tip 813 part of the cavity 804 may optionally be sized so as to allow solid material to escape from the tip part (813) of the cavity during/after manufacture of the component. For example, if the component were manufactured via additive methods, these passages may be sized to be greater than 0.3 mm in their smallest dimension in order to allow metal powder used in the additive manufacture to drain out of the tip part 813 of the cavity 804.
In contrast, annular cavity 805 is open at the injector outlet end and a continuous stream of air is channelled through this annular cavity 805 and out through the air outlet 807 which sits just downstream of the cone shaped nose 808. The converging outer wall 806 of channel 805 and the cone shaped nose 808 together create a single jet of air at the outlet 807. The outer wall 806 includes an array of holes 809 which encircle protruding fuel outlets 803. Some air from the annular cavity 805 thus exits through these holes 809 insulating the outlets 803 and providing an air film that may prevent the build-up of fuel in this region reducing the incidence of local coke formation. These holes 809 may optionally be sized to provide annular jets of air which help to shield the fuel jets from the air passing in crossflow and thereby cause the jets to penetrate further across the air stream.
Behind the nose 808 is a bridge 810 which spans the fuel passage 802. The bridge comprises an array radially extending arms 811 which meet at an apex 812 which sits in axial alignment with and apex of the nose cone 808. The bridge arms 811 are optionally shaped such that they converge at angles of from about 45° to about 65° to the injector axis. This may address a compromise between a requirements for manufacturability when constructed by additive methods, and minimising the size of a stagnant fuel zone (which can lead to coking) created in a local saddle at the convergence of the bridges 811 to apex 812.
The support beam 915 need not be extended all the way to the opposite end of the injector. Desirably it extends sufficiently far away from the outlets to provide that any wakes created as fuel flows around the support beam 915 are insignificant by the time the fluid enters the outlets. Beyond this distance, it could be shaped to meet any wall of the fuel gallery.
By providing the bean 915 to support the centre 916, the angle of the radially extending arms 912 to the axis of the fuel passage where they meet the centre 916 can be increased to around 90°. This can simplify manufacturability of the injector, and may eliminate the aforementioned saddle in which stagnant fuel can reside and any consequent occurrence of coking.
For any embodiments, the arms 811; 912; 112 of the bridge need not extend only in a radial direction. For example, the arms 811; 912; 112 may also extend axially forming a cone-like bridge structure. In another example, the arms 811; 912; 112 may include curvature forming a dome-like bridge structure. Optionally the arms 811; 912; 112 may have a circumferential component. The arms 811; 912; 112 may be arranged to generate different flow effective areas to the fuel outlet jets, so as to generate differences in the fuel flow through in different fuel jets.
In a fuel flow direction, the arms may be shaped aerodynamically to encourage efficient flow of the fuel towards the outlets 803;103. Similarly, spaced between the arms, the inner wall 113 may be profiled to guide fuel towards the outlets 803; 103 in an efficient manner. The number of arms 811; 912; 112 may equal the number of outlets 803; 103, the outlets being arranged circumferentially between adjacent arms 811; 912; 112.
The described bridge configurations may be conveniently manufactured using additive manufacturing techniques. For example, the bridge configurations may be manufactured using direct laser deposition (DLD). The bridge may be integrally formed with the injector nozzle.
The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects of the invention may be applied mutatis mutandis to any other aspect of the invention.
It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1700459.9 | Jan 2017 | GB | national |
| 1700465.6 | Jan 2017 | GB | national |
| 1705002.2 | Mar 2017 | GB | national |
