US20020164249A1 - Gas turbine engine exhaust nozzle - Google Patents
Gas turbine engine exhaust nozzle Download PDFInfo
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- US20020164249A1 US20020164249A1 US10/175,809 US17580902A US2002164249A1 US 20020164249 A1 US20020164249 A1 US 20020164249A1 US 17580902 A US17580902 A US 17580902A US 2002164249 A1 US2002164249 A1 US 2002164249A1
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- Prior art keywords
- nozzle
- tabs
- exhaust nozzle
- gas turbine
- turbine engine
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02K—JET-PROPULSION PLANTS
- F02K1/00—Plants characterised by the form or arrangement of the jet pipe or nozzle; Jet pipes or nozzles peculiar thereto
- F02K1/46—Nozzles having means for adding air to the jet or for augmenting the mixing region between the jet and the ambient air, e.g. for silencing
- F02K1/48—Corrugated nozzles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2260/00—Function
- F05D2260/96—Preventing, counteracting or reducing vibration or noise
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
Definitions
- the present invention relates generally to gas turbine engine exhaust nozzles, and in particular to noise reduction improvements to nozzle arrangements used on gas turbine engines used for aircraft propulsion.
- Gas turbine engines are widely used to power aircraft. As is well known, the engine basically provides propulsive power by generating a high velocity stream of gas which is exhausted rearwards through an exhaust nozzle. A single high velocity gas stream is produced by a turbojet gas turbine engine. More commonly nowadays however two streams, a core exhaust and a bypass exhaust, are generated by a ducted fan gas turbine engine or bypass gas turbine engine.
- exhaust noise The high velocity gas stream produced by gas turbine engines generates a significant amount of noise, which is referred to as exhaust noise.
- This noise is generated due to the high velocity of the exhaust stream, or streams, and the mixing of the streams with the surrounding atmosphere, and in the case of two streams, as the bypass and core streams mix.
- the degree of the noise generated is determined by the velocity of the stream and how the streams mix as they exhaust through the exhaust nozzle.
- lobed type nozzle which comprises a convoluted lobed core nozzle (sometimes called a mixer) with alternate circumferentially disposed lobes which direct the core exhaust stream radially outwardly into bypass exhaust stream, and the bypass exhaust stream radially inwardly into the core exhaust stream as well as generating mixing flows between the two streams.
- this type of nozzle is relatively complex both to manufacture and design.
- the performance and aerodynamic losses generated by the lobed mixer are significant.
- a gas turbine engine exhaust nozzle comprising a substantially frusto-conical nozzle wall, and a plurality of circumferentially disposed nozzle tabs which extend in a generally downstream direction from a downstream periphery of the nozzle wall; characterised in that the nozzle tabs are radially inwardly angled at an angle of up to 20° relative to the nozzle wall.
- An exhaust nozzle as described above provides improved exhaust noise characteristics. It is believed that the angling of the tabs, at angles up to 20°, generates stronger vortices in an exhaust flow through the nozzle. These stronger vortices provide improved control and enhanced mixing of the exhaust flow so reducing the perceived exhaust noise generated by the exhaust flow.
- the tabs circumferentially taper in a downstream direction.
- the tabs may particularly be of a substantially trapezoidal shape.
- the tabs may be of a substantially rectangular or square shape.
- the tabs are circumferentially disposed about the periphery of the nozzle to define substantially trapezoidally shaped notches between adjacent tabs.
- the tabs may be circumferentially disposed about the periphery of the nozzle to define substantially V shaped notches between adjacent tabs.
- edges of the tabs may be curved.
- the nozzle tabs are radially inwardly angled at an angle of up to 10° relative to the nozzle wall.
- the exhaust nozzle is a core engine nozzle.
- the exhaust nozzle may also or alternatively be a bypass exhaust nozzle.
- a ducted fan gas turbine engine exhaust nozzle assembly comprising a core exhaust nozzle and a bypass exhaust nozzle both as described above and/or as claimed in any one of claims 1 to 8.
- the ducted fan gas turbine engine exhaust nozzle assembly may comprise an outer bypass exhaust nozzle as described above and/or as claimed in any one of claims 1 to 8, and an inner core exhaust nozzle of a lobed mixer type.
- downstream end of the bypass nozzle is upstream of the downstream periphery of the core exhaust nozzle.
- downstream end of the bypass nozzle is further downstream than the downstream periphery of the core exhaust nozzle.
- FIG. 1 is a schematic section of a ducted fan gas turbine engine incorporating a exhaust nozzle according to the present invention
- FIG. 2 is a more detailed schematic perspective view of the exhaust nozzle of the ducted fan gas turbine engine shown in FIG. 1;
- FIG. 3 a part cutaway schematic view of the core exhaust nozzle of the ducted fan gas turbine engine and exhaust nozzle shown in FIGS. 1 and 2.
- FIG. 4 shows the effect of nozzle tabs on broadband shock-associated noise against frequency for model data scaled to full size, in a loss-less atmosphere.
- a ducted fan gas turbine engine 10 comprises, in axial flow series an air intake 5 , a propulsive fan 2 , a core engine 4 and an exhaust nozzle assembly 16 all disposed about a central engine axis 1 .
- the core engine 4 comprises, in axial flow series, a series of compressors 6 , a combustor 8 , and a series of turbines 9 .
- the direction of airflow through the engine 10 in operation is shown by arrow A and the terms upstream and downstream used throughout this description are used with reference to this general flow direction.
- Air is drawn in through the air intake 5 and is compressed and accelerated by the fan 2 .
- the air from the fan 2 is split between a core engine 4 flow and a bypass flow.
- the core engine 4 flow enters core engine 4 , flows through the core engine compressors 6 where it is further compressed, and into the combustor 8 where it is mixed with fuel which is supplied to, and burnt within the combustor 8 .
- Combustion of the fuel with the compressed air from the compressors 6 generates a high energy and velocity gas stream which exits the combustor 8 and flows downstream through the turbines 9 .
- the high energy gas stream from the combustor a still has a significant-amount-of energy and velocity and it is exhausted, as a core exhaust stream, through the engine exhaust nozzle assembly 16 to provide propulsive thrust.
- the remainder of the air from, and accelerated by, the fan 2 flows within a bypass duct 7 around the core engine 4 .
- This bypass air flow which has been accelerated by the fan 2 , flows to the exhaust nozzle assembly 16 where it is exhausted, as a bypass exhaust stream to provide further, and in fact the majority of, the useful propulsive thrust.
- the velocity of the bypass exhaust stream is significantly lower than that of the core exhaust stream.
- Turbulent mixing of the two exhaust streams in the region of, and downstream of, the exhaust nozzle assembly 16 , as well as mixing of both streams with the ambient air surrounding and downstream of the exhaust 16 generates a large component of the noise generated by the engine 10 . This noise is known as exhaust noise.
- Effective mixing and control of the mixing of the two exhaust streams with each other and the ambient air is required in order to reduce noise generated. The mixing and its control is effected by the exhaust nozzle assembly 16 .
- the exhaust nozzle assembly 16 comprises two concentric sections, namely a radially outer bypass exhaust nozzle 12 and an inner core exhaust nozzle 14 .
- the core exhaust nozzle 14 is defined by a generally frusto-conical core nozzle wall 15 . This defines the outer extent of an annular core exhaust duct 30 through which the core engine flow is exhausted from the core engine 4 .
- the inner extent of the core exhaust duct 30 is defined by an engine plug structure 22 .
- a plurality of circumferentially spaced tabs 20 extend from the downstream end of the core exhaust nozzle 14 and core nozzle walls 15 . The tabs 20 and exhaust nozzles 12 , 14 are shown more clearly in FIG. 2.
- the tabs 20 are of a trapezoidal shape with the sides of the tabs 20 circumferentially tapering towards each other in the downstream direction.
- the tabs 20 are evenly circumferentially disposed so that a notch 21 or space is defined by and between adjacent tabs 20 .
- the notches 21 are complimentary to the shape of the tab 20 and accordingly are of a trapezoidal shape on the core nozzle 14 , with the notches 21 circumferentially opening out in a downstream direction.
- the nozzle 14 is generally similar to those described and shown in GB 2,289,921 which is incorporated herein by reference.
- the number of tabs 20 , and so notches 21 defined in the core exhaust nozzle 14 and also bypass exhaust nozzle 12 (described below), the width of the notches 21 , angle of the notches 21 , width of notch 21 , angular offset between notches 21 , and angular gap between notches 21 are all essentially the same and within the same ranges as described in GB 2,289,921. It should be noted however that in GB 2,289,921 only the core nozzle 14 is provided with tabs 20 and notches 21 whereas, as described below, according to the present invention the bypass exhaust nozzle 12 may also be provided with tabs 20 and notches 21 .
- the tabs 20 of the core exhaust nozzle 14 are radially inwardly angled so that the tabs 20 impinge into the core duct 30 (relative to an extended line 24 , shown in FIG. 3, of the profile of the core nozzle wall 15 immediately upstream of the tabs 20 ) and are, in operation, incident on the core exhaust flow which is exhausted through the core exhaust nozzle 14 .
- the angle of incidence ⁇ of the tabs 20 is defined relative to an extended line 24 of the profile of the core exhaust nozzle wall 15 immediately upstream of the tabs 20 .
- the profile of the core nozzle wall 15 immediately upstream of the tabs 20 itself is at an angle ⁇ (typically between 10° and 20°) to the engine axis 1 .
- the tabs 20 and angling of the tabs 20 reduces the mid and low frequency noise generated by the exhaust and engine 10 , typically in the frequency range 50-500 kHz. It does however, in some cases increase the noise generated at higher frequencies.
- the noise at low and mid frequencies though is the most critical in terms of the perceived noise level and the higher frequency noise is masked by noise generated from elsewhere in the engine 10 . Therefore overall the tabs 20 provide a reduction in the perceived exhaust noise generated.
- the increase in high frequency noise sometimes associated with the angled tabs 20 at higher angles of incidence ⁇ is a further reason why the tabs 20 are preferably angled at angles of incidence ⁇ up to 10°.
- the tabs 20 induce streamwise vortices in the exhaust flow through and around the nozzle 14 . These vortices are generated and shed from the sides of the tabs 20 and increase the local turbulence levels in a shear layer that develops between the core and bypass exhaust streams downstream of the exhaust nozzle assembly 16 . This vorticity and turbulence increases and controls the rate of mixing between the core exhaust stream, bypass exhaust stream, and the ambient air. This reduces the velocities downstream of the exhaust assembly 16 , as compared to a conventional nozzle, and so reduces the mid to low frequency noise generated by the exhaust streams.
- the increased turbulence generated by the tabs 20 in the initial part of the shear layers immediately downstream of the exhaust nozzle assembly 16 causes an increase in the high frequency noise generated.
- Angling of the tabs 20 radially inwards increases the strength of the vortices produced and so improves the reduction in perceived noise.
- the angle of incidence ⁇ of the tabs 20 must not be too large since this can induce flow separation which will generate, rather than reduce the noise as well as adversely affecting aerodynamic performance of the nozzle 14 .
- the bypass exhaust nozzle 12 is also defined by a generally frusto-conical bypass nozzle wall 17 which is concentric with and disposed radially outwardly of the core exhaust nozzle 14 .
- the bypass nozzle wall 17 defines the outer extent of an annular bypass exhaust duct 28 through which the bypass engine flow is exhausted from the engine 10 .
- the inner extent of the bypass exhaust duct 28 is defined by an outer wall of the core engine 4 .
- the bypass nozzle is similar to the core exhaust nozzle 14 and a plurality of circumferentially spaced tabs 18 extend from the downstream end of the bypass exhaust nozzle 12 and bypass nozzle walls 17 .
- the tabs 18 are of a trapezoidal shape with the sides of the tabs 18 circumferentially tapering in the downstream direction.
- the tabs 18 are evenly circumferentially disposed so that a V shaped notch 19 or space is defined by and between adjacent tabs 18 .
- the bypass nozzle tabs 18 affect the bypass exhaust flow and noise generated in a similar way to the core exhaust nozzle tabs 20 .
- the separation between vortices produced from the same tab 18 , 20 (and so circumferential width of the tab 18 , 20 ) must be greater than the separation (and so circumferential width of notch 19 , 21 ) between vortices produced from adjacent tabs 18 , 20 . This is due to the direction of rotation of the vortices produced, with the vortices generated from the same tab 18 , 20 rotating in such a way that they are more likely to interact and coalesce.
- trapezoidal tabs 18 , 20 are preferred. It will be appreciated though that square or rectangular tabs could also be used. The edges of the tabs 18 , 20 and the tabs 18 , 20 themselves could also be curved. Triangular tabs are not however desirable since the vortices produced from either side of such a tab will tend to be coincident therefore producing less vortices of reduced strength around the circumference and so less noise reduction. The length of such a tab is also longer than required so adding unnecessary weight to the exhaust nozzle 12 , 14 , and adding further aerodynamic drag and a performance loss without significantly improving the noise. Furthermore the stress produce in such a shaped tab will tend to increase the likelihood of mechanical failure of such a triangular tab in operation.
- V shaped notches The aerodynamic performance affect of V shaped notches is however better than trapezoidal notches with V shaped notches being aerodynamically more efficient. Since the bypass exhaust provides the majority of the engine thrust loss of aerodynamic performance of the bypass exhaust nozzle 12 has a greater affect on overall engine performance than the aerodynamic performance of the core exhaust nozzle 14 . Consequently it is preferable to use V shaped notches on the bypass exhaust nozzle 12 and accept any problems described above that they may cause. On the core exhaust nozzle 14 however since the aerodynamic performance losses are less significant trapezoidal shaped notches are preferred to eliminate the above problems.
- the tabs 20 should have a length L sufficient to generate the required streamwise vortices as described below and GB 2,289,921 specifies that the tabs 18 , 20 must have a length L of between 5% to 50% of the nozzle diameter Dc, Db. It has been found however that using long tabs, towards the 50% end of the range given, induces excessive aerodynamic losses which adversely affect the performance particularly when they are angled. Accordingly it has been determined that the core tabs 20 should have a length L of approximately 10% of the core exhaust nozzle diameter Dc, whilst the bypass tabs 18 should have a length L of approximately 5% of the bypass exhaust nozzle diameter Db.
- bypass tabs 18 have a smaller percentage length since the bypass provides more of the propulsive thrust of the engine and so any performance loss on the bypass will have a greater affect on the overall engine performance. In addition although the percentage size is less, since the bypass is of a greater diameter than the core the actual physical size of the core tabs 20 and bypass tabs 20 not so different.
- FIG. 4 shows the effect of nozzle tabs 18 , 20 on broadband shock-associated noise for model data scaled to full size, in a loss-less atmosphere.
- FIG. 4 is associated to test results derived from an arrangement of tabs 18 , 20 as shown in FIG. 2.
- FIG. 4 shows experimental results obtained during a model-scale rig test of a high bypass ratio engine exhaust 16 at typical cruise nozzle pressure ratios.
- FIG. 4 shows the effect of nozzle tabs 18 , 20 on broadband shock-associated noise against frequency for model data scaled to full size, in a loss-less atmosphere.
- Line 32 relates to an exhaust with no tabs and line 34 relates to the exhaust 16 having tabs 18 , 20 as displayed in FIG. 2. It can be seen that there is a frequency shift and a general reduction in noise up to a certain frequency. The shift of peak noise from one frequency to a higher frequency is beneficial as the higher frequency noise is attenuated more readily and is less obtrusive to passengers in the cabin.
- a bypass exhaust nozzle using tabs as described above can be used in conjunction with a conventional forced lobed type core exhaust nozzle/mixer.
- Such an arrangement has also been tested and has shown improved noise suppression over an exhaust assembly which uses a lobed type core nozzle/mixer with a conventional bypass exhaust nozzle.
- the invention is also not limited to ducted fan gas turbine engines 10 with which in this embodiment it has been described and to which the invention is particularly suited. In other embodiments it can be applied to other gas turbine engine arrangements in which either two exhaust streams, one exhaust stream or any number of exhaust streams are exhausted from the engine though an exhaust nozzle(s).
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Abstract
A gas turbine engine exhaust nozzle for reducing exhaust noise comprising a substantially frusto-conical nozzle wall, and a plurality of circumferentially disposed nozzle tabs which extend in a generally downstream direction from a downstream periphery of the nozzle wall. The nozzle tabs are radially inwardly angled at an angle (β) of up to 20°, but preferably up to 10°, relative to the nozzle wall. Preferably tabs are of a substantially trapezoidal shape and substantially trapezoidally shaped notches are defined between adjacent tabs. Substantially V shaped notches may however be defined between the tabs. The angled tabs are particularly suitable for a ducted fan gas turbine engine and can be provided on the core exhaust nozzle or the bypass exhaust nozzle or on both nozzles. A bypass exhaust nozzle with such angled tabs can also be used with a lobed core exhaust nozzle.
Description
- The present invention relates generally to gas turbine engine exhaust nozzles, and in particular to noise reduction improvements to nozzle arrangements used on gas turbine engines used for aircraft propulsion.
- Gas turbine engines are widely used to power aircraft. As is well known, the engine basically provides propulsive power by generating a high velocity stream of gas which is exhausted rearwards through an exhaust nozzle. A single high velocity gas stream is produced by a turbojet gas turbine engine. More commonly nowadays however two streams, a core exhaust and a bypass exhaust, are generated by a ducted fan gas turbine engine or bypass gas turbine engine.
- The high velocity gas stream produced by gas turbine engines generates a significant amount of noise, which is referred to as exhaust noise. This noise is generated due to the high velocity of the exhaust stream, or streams, and the mixing of the streams with the surrounding atmosphere, and in the case of two streams, as the bypass and core streams mix. The degree of the noise generated is determined by the velocity of the stream and how the streams mix as they exhaust through the exhaust nozzle.
- Increasing environmental concerns require that the noise produced by gas turbine engines, and in particular aircraft gas turbine engines, is reduced and there has been considerable work carried out to reduce the noise produced by the mixing of the high velocity gas stream(s). A large number of various exhaust nozzle designs have been used and proposed to control and modify how the high velocity exhaust gas streams mix. With ducted fan gas turbine engines particular attention has been paid to the core stream and the mixing of the core and bypass exhaust streams. This is because the core stream velocity is considerably greater than the bypass stream and also the surrounding atmosphere and consequently the core exhaust stream generates a significant amount of the exhaust noise. Mixing of the core stream with the bypass stream has also been found to generate a significant proportion of the exhaust noise due to the difference in velocity of the core and bypass streams.
- One common current exhaust nozzle design that is widely used is a lobed type nozzle which comprises a convoluted lobed core nozzle (sometimes called a mixer) with alternate circumferentially disposed lobes which direct the core exhaust stream radially outwardly into bypass exhaust stream, and the bypass exhaust stream radially inwardly into the core exhaust stream as well as generating mixing flows between the two streams. This forces the streams to mix which improves the mixing of the streams and so reduces the noise generated. Whilst providing a degree of noise suppression this type of nozzle is relatively complex both to manufacture and design. Furthermore when such nozzles are applied to high bypass ratio turbofan engines the performance and aerodynamic losses generated by the lobed mixer are significant. In addition such nozzles generally require, for optimum performance, an extended bypass nozzle with the downstream end of the bypass nozzle disposed downstream of the downstream end of the lobed core nozzle/mixer. This adds considerable weight, drag, and cost to the installation and nowadays short bypass nozzles are favoured with which the lobed type core nozzles are less effective and are also more detrimental to the engine performance than when used on a long cowl arrangement.
- An alternative nozzle design that is directed to reducing exhaust noise is proposed and described in GB 2,289,921. In this proposal a number of circumferentially spaced notches, of various specified configurations, sizes, spacing and shapes, are provided in the downstream periphery of a generally circular core exhaust nozzle. Such a nozzle design is considerably simpler to manufacture than the conventional lobed designs. This prior proposal describes that the notches generate vortices in the exhaust streams. These vortices enhance and control the mixing of the core and bypass streams which it is claimed reduces the exhaust noise.
- Model testing of nozzles similar to those described in GB 2,289,921 has shown that significant noise reduction and suppression can be achieved. However the parameters and details of the design proposed in GB 2,289,921 are not optimal and there is a continual desire to improve the nozzle design further.
- It is therefore desirable to provide an improved gas turbine engine exhaust nozzle which is quieter than conventional exhaust nozzles and/or which offers improvements generally.
- According to a first aspect of the present invention there is provided a gas turbine engine exhaust nozzle comprising a substantially frusto-conical nozzle wall, and a plurality of circumferentially disposed nozzle tabs which extend in a generally downstream direction from a downstream periphery of the nozzle wall; characterised in that the nozzle tabs are radially inwardly angled at an angle of up to 20° relative to the nozzle wall.
- An exhaust nozzle as described above provides improved exhaust noise characteristics. It is believed that the angling of the tabs, at angles up to 20°, generates stronger vortices in an exhaust flow through the nozzle. These stronger vortices provide improved control and enhanced mixing of the exhaust flow so reducing the perceived exhaust noise generated by the exhaust flow.
- Preferably the tabs circumferentially taper in a downstream direction. The tabs may particularly be of a substantially trapezoidal shape. Alternatively the tabs may be of a substantially rectangular or square shape.
- Preferably the tabs are circumferentially disposed about the periphery of the nozzle to define substantially trapezoidally shaped notches between adjacent tabs. Alternatively the tabs may be circumferentially disposed about the periphery of the nozzle to define substantially V shaped notches between adjacent tabs.
- The edges of the tabs may be curved.
- Preferably the nozzle tabs are radially inwardly angled at an angle of up to 10° relative to the nozzle wall.
- Preferably the exhaust nozzle is a core engine nozzle. The exhaust nozzle may also or alternatively be a bypass exhaust nozzle.
- According to a second aspect of the present invention there is provided a ducted fan gas turbine engine exhaust nozzle assembly comprising a core exhaust nozzle and a bypass exhaust nozzle both as described above and/or as claimed in any one of
claims 1 to 8. - The ducted fan gas turbine engine exhaust nozzle assembly may comprise an outer bypass exhaust nozzle as described above and/or as claimed in any one of
claims 1 to 8, and an inner core exhaust nozzle of a lobed mixer type. - Preferably the downstream end of the bypass nozzle is upstream of the downstream periphery of the core exhaust nozzle. Alternatively the downstream end of the bypass nozzle is further downstream than the downstream periphery of the core exhaust nozzle.
- The present invention will now be described by way of example only with reference to the following figures in which:
- FIG. 1 is a schematic section of a ducted fan gas turbine engine incorporating a exhaust nozzle according to the present invention;
- FIG. 2 is a more detailed schematic perspective view of the exhaust nozzle of the ducted fan gas turbine engine shown in FIG. 1;
- FIG. 3 a part cutaway schematic view of the core exhaust nozzle of the ducted fan gas turbine engine and exhaust nozzle shown in FIGS. 1 and 2.
- FIG. 4 shows the effect of nozzle tabs on broadband shock-associated noise against frequency for model data scaled to full size, in a loss-less atmosphere.
- With reference to FIG. 1 a ducted fan
gas turbine engine 10 comprises, in axial flow series anair intake 5, apropulsive fan 2, acore engine 4 and anexhaust nozzle assembly 16 all disposed about acentral engine axis 1. Thecore engine 4 comprises, in axial flow series, a series of compressors 6, acombustor 8, and a series ofturbines 9. The direction of airflow through theengine 10 in operation is shown by arrow A and the terms upstream and downstream used throughout this description are used with reference to this general flow direction. Air is drawn in through theair intake 5 and is compressed and accelerated by thefan 2. The air from thefan 2 is split between acore engine 4 flow and a bypass flow. Thecore engine 4 flow enterscore engine 4, flows through the core engine compressors 6 where it is further compressed, and into thecombustor 8 where it is mixed with fuel which is supplied to, and burnt within thecombustor 8. Combustion of the fuel with the compressed air from the compressors 6 generates a high energy and velocity gas stream which exits thecombustor 8 and flows downstream through theturbines 9. As the high energy gas stream flows through theturbines 9 it rotates turbine rotors extracting energy from the gas stream which is used to drive thefan 2 and compressors 6 viaengine shafts 11 which drivingly connect theturbine 9 rotors with the compressors 6 andfan 2. Having flowed through theturbines 9 the high energy gas stream from the combustor a still has a significant-amount-of energy and velocity and it is exhausted, as a core exhaust stream, through the engineexhaust nozzle assembly 16 to provide propulsive thrust. The remainder of the air from, and accelerated by, thefan 2 flows within abypass duct 7 around thecore engine 4. This bypass air flow, which has been accelerated by thefan 2, flows to theexhaust nozzle assembly 16 where it is exhausted, as a bypass exhaust stream to provide further, and in fact the majority of, the useful propulsive thrust. - The velocity of the bypass exhaust stream is significantly lower than that of the core exhaust stream. Turbulent mixing of the two exhaust streams in the region of, and downstream of, the
exhaust nozzle assembly 16, as well as mixing of both streams with the ambient air surrounding and downstream of theexhaust 16 generates a large component of the noise generated by theengine 10. This noise is known as exhaust noise. Effective mixing and control of the mixing of the two exhaust streams with each other and the ambient air is required in order to reduce noise generated. The mixing and its control is effected by theexhaust nozzle assembly 16. - In the embodiment shown the
exhaust nozzle assembly 16 comprises two concentric sections, namely a radially outerbypass exhaust nozzle 12 and an innercore exhaust nozzle 14. Thecore exhaust nozzle 14 is defined by a generally frusto-conicalcore nozzle wall 15. This defines the outer extent of an annularcore exhaust duct 30 through which the core engine flow is exhausted from thecore engine 4. The inner extent of thecore exhaust duct 30 is defined by anengine plug structure 22. A plurality of circumferentially spacedtabs 20 extend from the downstream end of thecore exhaust nozzle 14 andcore nozzle walls 15. Thetabs 20 andexhaust nozzles tabs 20 are of a trapezoidal shape with the sides of thetabs 20 circumferentially tapering towards each other in the downstream direction. Thetabs 20 are evenly circumferentially disposed so that anotch 21 or space is defined by and betweenadjacent tabs 20. Thenotches 21 are complimentary to the shape of thetab 20 and accordingly are of a trapezoidal shape on thecore nozzle 14, with thenotches 21 circumferentially opening out in a downstream direction. - The
nozzle 14 is generally similar to those described and shown in GB 2,289,921 which is incorporated herein by reference. The number oftabs 20, and sonotches 21 defined in thecore exhaust nozzle 14 and also bypass exhaust nozzle 12 (described below), the width of thenotches 21, angle of thenotches 21, width ofnotch 21, angular offset betweennotches 21, and angular gap betweennotches 21 are all essentially the same and within the same ranges as described in GB 2,289,921. It should be noted however that in GB 2,289,921 only thecore nozzle 14 is provided withtabs 20 andnotches 21 whereas, as described below, according to the present invention thebypass exhaust nozzle 12 may also be provided withtabs 20 andnotches 21. - Referring to FIG. 3, the
tabs 20 of thecore exhaust nozzle 14 are radially inwardly angled so that thetabs 20 impinge into the core duct 30 (relative to anextended line 24, shown in FIG. 3, of the profile of thecore nozzle wall 15 immediately upstream of the tabs 20) and are, in operation, incident on the core exhaust flow which is exhausted through thecore exhaust nozzle 14. The angle of incidence β of thetabs 20 is defined relative to anextended line 24 of the profile of the coreexhaust nozzle wall 15 immediately upstream of thetabs 20. The profile of thecore nozzle wall 15 immediately upstream of thetabs 20 itself is at an angle α (typically between 10° and 20°) to theengine axis 1. - It has been found that by angling the
tabs 20, and the angle of incidence β, has a effect on noise suppression. As the angle of incidence β is increased up to 20° the noise reductions are improved. However at angles of incidence β above 20° there is little further improvement in noise suppression. Furthermore at these higher angles of incidence β aerodynamic losses due to the effect thetabs 20 have on the core exhaust flow increase. Therefore preferably thetabs 20 are angled at angles of incidence β up to 10°. - The
tabs 20 and angling of thetabs 20 reduces the mid and low frequency noise generated by the exhaust andengine 10, typically in the frequency range 50-500 kHz. It does however, in some cases increase the noise generated at higher frequencies. The noise at low and mid frequencies though is the most critical in terms of the perceived noise level and the higher frequency noise is masked by noise generated from elsewhere in theengine 10. Therefore overall thetabs 20 provide a reduction in the perceived exhaust noise generated. The increase in high frequency noise sometimes associated with theangled tabs 20 at higher angles of incidence β is a further reason why thetabs 20 are preferably angled at angles of incidence β up to 10°. - It is believed that the
tabs 20 induce streamwise vortices in the exhaust flow through and around thenozzle 14. These vortices are generated and shed from the sides of thetabs 20 and increase the local turbulence levels in a shear layer that develops between the core and bypass exhaust streams downstream of theexhaust nozzle assembly 16. This vorticity and turbulence increases and controls the rate of mixing between the core exhaust stream, bypass exhaust stream, and the ambient air. This reduces the velocities downstream of theexhaust assembly 16, as compared to a conventional nozzle, and so reduces the mid to low frequency noise generated by the exhaust streams. The increased turbulence generated by thetabs 20 in the initial part of the shear layers immediately downstream of theexhaust nozzle assembly 16 causes an increase in the high frequency noise generated. Angling of thetabs 20 radially inwards increases the strength of the vortices produced and so improves the reduction in perceived noise. However the angle of incidence β of thetabs 20 must not be too large since this can induce flow separation which will generate, rather than reduce the noise as well as adversely affecting aerodynamic performance of thenozzle 14. - The
bypass exhaust nozzle 12 is also defined by a generally frusto-conicalbypass nozzle wall 17 which is concentric with and disposed radially outwardly of thecore exhaust nozzle 14. Thebypass nozzle wall 17 defines the outer extent of an annularbypass exhaust duct 28 through which the bypass engine flow is exhausted from theengine 10. The inner extent of thebypass exhaust duct 28 is defined by an outer wall of thecore engine 4. The bypass nozzle is similar to thecore exhaust nozzle 14 and a plurality of circumferentially spacedtabs 18 extend from the downstream end of thebypass exhaust nozzle 12 andbypass nozzle walls 17. As with thecore nozzle 14, thetabs 18 are of a trapezoidal shape with the sides of thetabs 18 circumferentially tapering in the downstream direction. Thetabs 18 are evenly circumferentially disposed so that a V shapednotch 19 or space is defined by and betweenadjacent tabs 18. Thebypass nozzle tabs 18 affect the bypass exhaust flow and noise generated in a similar way to the coreexhaust nozzle tabs 20. - Increasing the number of vortices generated with such exhaust nozzle designs, by providing
more tabs nozzle tabs such exhaust nozzle same tab 18,20 (and so circumferential width of thetab 18,20) must be greater than the separation (and so circumferential width ofnotch 19,21) between vortices produced fromadjacent tabs same tab - It is due to this reason that
trapezoidal tabs tabs tabs exhaust nozzle - With the arrangement of
tabs 18 shown on thebypass exhaust nozzle 12, withV notches 19 betweentabs 18, a large number oftabs 18 and so a larger number of vortices can be generated whilst still maintaining the required separation of the vortices. A similar arrangement could be used on thecore exhaust nozzle 14, however due to the smaller diameter of the core exhaust nozzle 14 a trapezoidal shapednotch 21 is preferred to provide the required separation betweenadjacent tabs 20. Furthermore on smaller diameter nozzles, such as thecore exhaust nozzle 14, it has been found that use of V shaped notches may restrict flow between the tabs which reduces the strength and generation of the individual vortices produced and so the noise suppression. This may outweigh the advantages of generating more vortices by providing more tabs. In addition V shaped notches result in a stress concentration at their apex which in high stress situations can lead to stress problems and failure of the nozzle. - The aerodynamic performance affect of V shaped notches is however better than trapezoidal notches with V shaped notches being aerodynamically more efficient. Since the bypass exhaust provides the majority of the engine thrust loss of aerodynamic performance of the
bypass exhaust nozzle 12 has a greater affect on overall engine performance than the aerodynamic performance of thecore exhaust nozzle 14. Consequently it is preferable to use V shaped notches on thebypass exhaust nozzle 12 and accept any problems described above that they may cause. On thecore exhaust nozzle 14 however since the aerodynamic performance losses are less significant trapezoidal shaped notches are preferred to eliminate the above problems. - It is believed that the angling of the
tabs core exhaust nozzle 14. This is because the relative pressure difference between the core and bypass is greater than that between the bypass and the ambient surrounding air with the result that the bypass exhaust stream restricts and constrains the core exhaust stream more than the ambient atmosphere restricts and constrains the bypass exhaust stream. Consequently, in order to enhance and control the mixing of the core exhaust stream and provide noise suppression, stronger vortices, generated byangled tabs - The
tabs 20 should have a length L sufficient to generate the required streamwise vortices as described below and GB 2,289,921 specifies that thetabs core tabs 20 should have a length L of approximately 10% of the core exhaust nozzle diameter Dc, whilst thebypass tabs 18 should have a length L of approximately 5% of the bypass exhaust nozzle diameter Db. Thebypass tabs 18 have a smaller percentage length since the bypass provides more of the propulsive thrust of the engine and so any performance loss on the bypass will have a greater affect on the overall engine performance. In addition although the percentage size is less, since the bypass is of a greater diameter than the core the actual physical size of thecore tabs 20 andbypass tabs 20 not so different. - In model tests of the
exhaust nozzle assembly 16 shown in FIG. 2 and described above a 5 dB reduction in the peak sound pressure level over a conventional plain frusto conical nozzle arrangement has been achieved. It has also been found that the noise reductions provided by usingtabs 18 on thebypass exhaust nozzle 12 and by usingtabs 20 on thecore exhaust nozzle 14 are cumulative. It will therefore be appreciated that inother embodiments tabs bypass exhaust nozzle 12 or thecore exhaust nozzle 14 alone to give some improved degree of noise suppression. The coreexhaust nozzle tabs 20 and the bypassexhaust nozzle tabs 18 can also be angled at different angles of incidence FIG. 4 shows the effect ofnozzle tabs tabs - When the pressure ratio of a
convergent nozzle assembly 16 becomes supercritical the exhaust flow downstream of thenozzle - As the noise propagates from the
engine 10 to the cabin there will be a small amount of attenuation by the atmosphere. However, in order to reduce the noise in the cabin to comfortable or acceptable levels the airframe manufacturers need to take measures to attenuate the noise as it propagates through the aircraft fuselage. Since the noise can reach the cabin via a number of transmission paths, such treatment inevitably results in significant increases in the cost and weight of the aircraft. - Application of the
nozzle tabs bypass nozzle 12, results in an increase in the frequency of the peak shock noise. These higher frequencies are more readily attenuated by acoustic treatment and the increase in frequency therefore assists in reducing the noise levels in the cabin. Furthermore, it could reduce the cost and weight of the fuselage acoustic treatment for the same cabin noise level since it does not need to be so extreme. - FIG. 4 shows experimental results obtained during a model-scale rig test of a high bypass
ratio engine exhaust 16 at typical cruise nozzle pressure ratios. FIG. 4 shows the effect ofnozzle tabs Line 32 relates to an exhaust with no tabs andline 34 relates to theexhaust 16 havingtabs - Furthermore in yet further embodiments of the invention a bypass exhaust nozzle using tabs as described above can be used in conjunction with a conventional forced lobed type core exhaust nozzle/mixer. Such an arrangement has also been tested and has shown improved noise suppression over an exhaust assembly which uses a lobed type core nozzle/mixer with a conventional bypass exhaust nozzle.
- Although the invention has been described and shown with reference to a short cowl type engine arrangement in which the
bypass duct 28 andbypass exhaust nozzle 12 terminate upstream of thecore exhaust duct 30 andnozzle 14, the invention may also be applied, in other embodiments, to long cowl type engine arrangements in which thebypass duct 28 andbypass exhaust nozzle 12 terminate downstream of thecore exhaust duct 20 andnozzle 14. The invention however is particularly beneficial to short cowl arrangements since with such arrangements conventional noise suppression treatments of the exhaust are not practical in particular where high by pass ratios are also used. - The invention is also not limited to ducted fan
gas turbine engines 10 with which in this embodiment it has been described and to which the invention is particularly suited. In other embodiments it can be applied to other gas turbine engine arrangements in which either two exhaust streams, one exhaust stream or any number of exhaust streams are exhausted from the engine though an exhaust nozzle(s).
Claims (14)
1. A gas turbine engine exhaust nozzle comprising a substantially frusto-conical nozzle wall having a downstream periphery, and a plurality of circumferentially disposed nozzle tabs, the nozzle tabs extend in a generally downstream direction from the downstream periphery of the nozzle wall;
wherein the nozzle tabs are radially inwardly angled at an angle of up to 20° relative to the nozzle wall.
2. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the tabs circumferentially taper in a downstream direction.
3. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the tabs are of a substantially trapezoidal shape.
4. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the tabs are of a substantially rectangular or square shape.
5. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the tabs are circumferentially disposed about the periphery of the nozzle to define substantially trapezoidally shaped notches between adjacent tabs.
6. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the tabs are circumferentially disposed about the periphery of the nozzle to define substantially V shaped notches between adjacent tabs.
7. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the edges of the tabs are curved.
8. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the nozzle tabs are radially inwardly angled at an angle of up to 10° relative-to the nozzle wall.
9. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the exhaust nozzle is a core engine nozzle.
10. A gas turbine engine exhaust nozzle as claimed in claim 1 in which the exhaust nozzle is a bypass exhaust nozzle.
11. A ducted fan gas turbine engine exhaust nozzle assembly as claimed in claim 1 , the assembly comprising a core exhaust nozzle and a bypass exhaust nozzle.
12. A ducted fan gas turbine engine exhaust nozzle assembly nozzle as claimed in claim 1 comprising an outer bypass exhaust and an inner core exhaust nozzle of a lobed mixer type.
13. A ducted fan gas turbine engine exhaust nozzle assembly as claimed in claim 12 in which the downstream end of the bypass nozzle is further downstream than the downstream periphery of the core exhaust nozzle.
14. A ducted fan gas turbine engine exhaust nozzle assembly as claimed in claim 10 in which the downstream end of the bypass nozzle is upstream of the downstream periphery of the core exhaust nozzle.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/175,809 US20020164249A1 (en) | 1999-10-26 | 2002-06-21 | Gas turbine engine exhaust nozzle |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9925193.6 | 1999-10-26 | ||
GBGB9925193.6A GB9925193D0 (en) | 1999-10-26 | 1999-10-26 | Gas turbine engine exhaust nozzle |
US69089600A | 2000-10-18 | 2000-10-18 | |
US10/175,809 US20020164249A1 (en) | 1999-10-26 | 2002-06-21 | Gas turbine engine exhaust nozzle |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US69089600A Continuation | 1999-10-26 | 2000-10-18 |
Publications (1)
Publication Number | Publication Date |
---|---|
US20020164249A1 true US20020164249A1 (en) | 2002-11-07 |
Family
ID=10863315
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/175,809 Abandoned US20020164249A1 (en) | 1999-10-26 | 2002-06-21 | Gas turbine engine exhaust nozzle |
Country Status (3)
Country | Link |
---|---|
US (1) | US20020164249A1 (en) |
FR (1) | FR2800129A1 (en) |
GB (2) | GB9925193D0 (en) |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060059891A1 (en) * | 2004-09-23 | 2006-03-23 | Honeywell International, Inc. | Quiet chevron/tab exhaust eductor system |
US20060272800A1 (en) * | 2005-06-02 | 2006-12-07 | Paccar Inc | Radiator fan shroud with flow directing ports |
US7305817B2 (en) | 2004-02-09 | 2007-12-11 | General Electric Company | Sinuous chevron exhaust nozzle |
FR2902836A1 (en) * | 2006-06-26 | 2007-12-28 | Snecma Sa | Ring bonnet for separate-flow nozzle of aircraft turbomachine, has jet noise reduction units with each side connected to trailing edge based on bent contour with bend radius higher than or equal to that of bent contour of apex of units |
EP1873388A1 (en) | 2006-06-26 | 2008-01-02 | Snecma | Turbomachine cowl having noise suppression triangular tabs with double crests |
US20090068006A1 (en) * | 2007-05-17 | 2009-03-12 | Elliott Company | Tilted Cone Diffuser for Use with an Exhaust System of a Turbine |
JP2009127625A (en) * | 2007-11-23 | 2009-06-11 | Snecma | Fan nozzle having adjustable section |
US20140144152A1 (en) * | 2012-11-26 | 2014-05-29 | General Electric Company | Premixer With Fuel Tubes Having Chevron Outlets |
US9279387B2 (en) | 2012-11-08 | 2016-03-08 | Rolls-Royce Deutschland Ltd & Co Kg | Nozzle with guiding devices |
US20160138416A1 (en) * | 2006-10-12 | 2016-05-19 | United Technologies Corporation | Variable fan nozzle using shape memory material |
US9605621B2 (en) | 2012-11-08 | 2017-03-28 | Rolls-Royce Deutschland Ltd & Co Kg | Nozzle with guiding devices |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6612106B2 (en) | 2000-05-05 | 2003-09-02 | The Boeing Company | Segmented mixing device having chevrons for exhaust noise reduction in jet engines |
DE20118939U1 (en) * | 2000-12-01 | 2002-04-25 | Papst-Motoren GmbH & Co. KG, 78112 St Georgen | Fan housing, especially for axial fans |
GB0105349D0 (en) * | 2001-03-03 | 2001-04-18 | Rolls Royce Plc | Gas turbine engine exhaust nozzle |
GB2372780A (en) * | 2001-03-03 | 2002-09-04 | Rolls Royce Plc | Gas turbine engine nozzle with noise-reducing tabs |
US6718752B2 (en) * | 2002-05-29 | 2004-04-13 | The Boeing Company | Deployable segmented exhaust nozzle for a jet engine |
US7458221B1 (en) | 2003-10-23 | 2008-12-02 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Variable area nozzle including a plurality of convexly vanes with a crowned contour, in a vane to vane sealing arrangement and with nonuniform lengths |
FR2873166B1 (en) * | 2004-07-13 | 2008-10-31 | Snecma Moteurs Sa | TURBOMACHINE TUBE WITH PATTERNS WITH JET NOISE REDUCTION |
FR2921700A1 (en) | 2007-09-28 | 2009-04-03 | Snecma Sa | HOUSING FOR A TURBOMACHINE TUBE WITH PATTERNS WITH JET NOISE REDUCTION |
DE102007063018A1 (en) | 2007-12-21 | 2009-06-25 | Rolls-Royce Deutschland Ltd & Co Kg | Nozzle with guide elements |
RU2615309C1 (en) * | 2015-10-26 | 2017-04-04 | Акционерное общество "Объединенная двигателестроительная корпорация" (АО "ОДК") | Chevron nozzle of gas turbine engine |
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NL98695C (en) * | 1952-07-25 | |||
US3055174A (en) * | 1957-01-14 | 1962-09-25 | Boeing Co | Retractable noise suppressor for jet engines |
FR1164936A (en) * | 1957-01-21 | 1958-10-15 | Bertin Et Cie Soc | Silencers for exhaust ducts and in particular for jet thruster nozzles |
FR2388243A1 (en) * | 1977-04-21 | 1978-11-17 | Europ Propulsion | DEVICE FOR GIVING A ROTATIONAL MOVEMENT TO A UNIT WHEN IT IS LAUNCHED |
US4284170A (en) * | 1979-10-22 | 1981-08-18 | United Technologies Corporation | Gas turbine noise suppressor |
GB2289921A (en) * | 1994-06-03 | 1995-12-06 | A E Harris Limited | Nozzle for turbofan aeroengines |
US6360528B1 (en) * | 1997-10-31 | 2002-03-26 | General Electric Company | Chevron exhaust nozzle for a gas turbine engine |
US6314721B1 (en) * | 1998-09-04 | 2001-11-13 | United Technologies Corporation | Tabbed nozzle for jet noise suppression |
US6487848B2 (en) * | 1998-11-06 | 2002-12-03 | United Technologies Corporation | Gas turbine engine jet noise suppressor |
-
1999
- 1999-10-26 GB GBGB9925193.6A patent/GB9925193D0/en not_active Ceased
-
2000
- 2000-10-20 GB GB0025727A patent/GB2355766A/en not_active Withdrawn
- 2000-10-25 FR FR0013692A patent/FR2800129A1/en active Pending
-
2002
- 2002-06-21 US US10/175,809 patent/US20020164249A1/en not_active Abandoned
Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7305817B2 (en) | 2004-02-09 | 2007-12-11 | General Electric Company | Sinuous chevron exhaust nozzle |
US20060059891A1 (en) * | 2004-09-23 | 2006-03-23 | Honeywell International, Inc. | Quiet chevron/tab exhaust eductor system |
US20060272800A1 (en) * | 2005-06-02 | 2006-12-07 | Paccar Inc | Radiator fan shroud with flow directing ports |
FR2902836A1 (en) * | 2006-06-26 | 2007-12-28 | Snecma Sa | Ring bonnet for separate-flow nozzle of aircraft turbomachine, has jet noise reduction units with each side connected to trailing edge based on bent contour with bend radius higher than or equal to that of bent contour of apex of units |
EP1873388A1 (en) | 2006-06-26 | 2008-01-02 | Snecma | Turbomachine cowl having noise suppression triangular tabs with double crests |
EP1873389A1 (en) * | 2006-06-26 | 2008-01-02 | Snecma | Turbomachine nozzle cowl with triangular noise suppression tabs having an inflexion point |
US7581384B2 (en) | 2006-06-26 | 2009-09-01 | Snecma | Turbomachine nozzle cover provided with triangular patterns having a point of inflexion for reducing jet noise |
US20160138416A1 (en) * | 2006-10-12 | 2016-05-19 | United Technologies Corporation | Variable fan nozzle using shape memory material |
US10371001B2 (en) * | 2006-10-12 | 2019-08-06 | United Technologies Corporation | Variable fan nozzle using shape memory material |
US20090068006A1 (en) * | 2007-05-17 | 2009-03-12 | Elliott Company | Tilted Cone Diffuser for Use with an Exhaust System of a Turbine |
US7731475B2 (en) | 2007-05-17 | 2010-06-08 | Elliott Company | Tilted cone diffuser for use with an exhaust system of a turbine |
JP2009127625A (en) * | 2007-11-23 | 2009-06-11 | Snecma | Fan nozzle having adjustable section |
US9279387B2 (en) | 2012-11-08 | 2016-03-08 | Rolls-Royce Deutschland Ltd & Co Kg | Nozzle with guiding devices |
US9605621B2 (en) | 2012-11-08 | 2017-03-28 | Rolls-Royce Deutschland Ltd & Co Kg | Nozzle with guiding devices |
US20140144152A1 (en) * | 2012-11-26 | 2014-05-29 | General Electric Company | Premixer With Fuel Tubes Having Chevron Outlets |
Also Published As
Publication number | Publication date |
---|---|
GB0025727D0 (en) | 2000-12-06 |
GB9925193D0 (en) | 1999-12-22 |
GB2355766A (en) | 2001-05-02 |
FR2800129A1 (en) | 2001-04-27 |
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Legal Events
Date | Code | Title | Description |
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STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |