GB2319589A - Acoustic panel retention - Google Patents

Acoustic panel retention Download PDF

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Publication number
GB2319589A
GB2319589A GB9624301A GB9624301A GB2319589A GB 2319589 A GB2319589 A GB 2319589A GB 9624301 A GB9624301 A GB 9624301A GB 9624301 A GB9624301 A GB 9624301A GB 2319589 A GB2319589 A GB 2319589A
Authority
GB
United Kingdom
Prior art keywords
acoustic panel
boss
layers
perforate
acoustic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9624301A
Other versions
GB9624301D0 (en
GB2319589B (en
Inventor
Philip Ridyard
Jeremy Paul Goodwin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rolls Royce PLC
Original Assignee
Rolls Royce PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Priority to GB9624301A priority Critical patent/GB2319589B/en
Publication of GB9624301D0 publication Critical patent/GB9624301D0/en
Priority to FR9714435A priority patent/FR2756332A1/en
Publication of GB2319589A publication Critical patent/GB2319589A/en
Application granted granted Critical
Publication of GB2319589B publication Critical patent/GB2319589B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENTS OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/02—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/04—Air intakes for gas-turbine plants or jet-propulsion plants
    • F02C7/045—Air intakes for gas-turbine plants or jet-propulsion plants having provisions for noise suppression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/24—Heat or noise insulation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B5/00—Joining sheets or plates, e.g. panels, to one another or to strips or bars parallel to them
    • F16B5/01—Joining sheets or plates, e.g. panels, to one another or to strips or bars parallel to them by means of fastening elements specially adapted for honeycomb panels
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENTS OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/02—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes
    • B64D2033/0206—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes comprising noise reduction means, e.g. acoustic liners
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENTS OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D33/00—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for
    • B64D33/02—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes
    • B64D2033/0266—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes specially adapted for particular type of power plants
    • B64D2033/0286—Arrangements in aircraft of power plant parts or auxiliaries not otherwise provided for of combustion air intakes specially adapted for particular type of power plants for turbofan engines

Abstract

An acoustic panel (18) for a gas turbine engine (10) comprises a layer of honeycomb material (21) interposed between two layers of sheet material (19,20). At least one cell (22) of the honeycomb material contains a boss (23). The boss (23) has a passage (25) extending therethrough to receive a screw (27) for attaching the acoustic panel (18) to a fixed structure (29). Each of the boss (23) and one of the layers of sheet material (19) is provided with an indentation to receive the countersink head (28) of the screw (27).

Description

ACOUSTIC PANEL RETENTION This invention relates to the retention of acoustic panels on a support structure. It is particularly concerned with the retention of acoustic panels on the fan casing and other parts of a ducted fan gas turbine engine for aircraft propulsion.
Ducted fan gas turbine engines typically have air-washed surfaces within their fan ducts to which it is desirable to attach acoustic panels for sound attenuation purposes. Such panels conventionally comprise two sheets of material between which is interposed a layer of honeycomb material. The sheet which defines at least part of the air-washed surface is perforate in order to permit sound energy generated within the fan duct access to the cells of the honeycomb material.
The cells serve to attenuate that sound energy in the conventional manner. The use of such acoustic panels in ducted fan gas turbine engines is widespread and will not, therefore, be described in further detail.
It is necessary to attach such acoustic panels to a support structure, such as the fan casing of the ducted fan gas turbine engine, in such a way that the panels are easily removable in the event of damage. Conventionally, this is achieved by bolting the panels to the support structure.
However, the honeycomb material of the acoustic panels is easily damaged by crushing. Consequently it is necessary to provide local reinforcement of the honeycomb material in order to avoid such damage by the attachment bolts.
One common way of providing such local reinforcement is to fill a number of adjacent honeycomb cells in the region of each attachment bolt with a suitably strong material and then to machine a bolt reception feature in those filled cells.
There are drawbacks with this approach however. One drawback is that since a number of cells in the region of one bolt are filled, they can no longer provide sound attenuation. Consequently there is an adverse effect upon the overall sound attenuation efficiency of the acoustic panel. A further drawback is that it is very difficult to ensure that the mounting bolts do not stand proud of the air-washed surface of the acoustic panel and thereby impose performance penalties on the engine.
It is an object of the present invention to provide an acoustic panel which may be attached to a support structure in a way that has little effect upon the sound attenuation characteristics of the panel and also upon the aerodynamic efficiency of the air-washed surface of the panel.
According to the present invention, an acoustic panel comprises a layer of cellular honeycomb material interposed between and interconnecting two layers of sheet material, one of which is perforate, whereby at least one of the cells of said cellular honeycomb material interconnects said layers of sheet material and contains a boss which abuts both of said layers of sheet material, said boss and the portions of said layers of sheet material adjacent thereto being apertured to receive common means for attaching said acoustic panel to a support structure.
Said boss is preferably of cylindrical configuration so that it engages the walls of the cell it occupies.
Said boss and the portion of said perforate sheet it engages are preferably provided with corresponding indentations which are so configured that said fastener is positioned flush with the external surface of said perforate sheet.
Said indentations are preferably of generally frustoconical form to receive a fastener that is in the form of a screw having a countersink head.
The present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a partially sectioned side view of a ducted fan gas turbine engine provided with acoustic panels in accordance with the present invention.
Figure 2 is a perspective view of a portion of an acoustic panel on the engine shown in Figure 1 which is in accordance with the present invention and which has been partially broken away in order to reveal its internal structure.
Figure 3 is a sectioned side view of a portion of the acoustic panel shown in Figure 2.
Figure 4 is a view on the section line A-A of Figure 3.
With reference to Figure 1, a ducted fan gas turbine engine 10, is enclosed within a generally annular nacelle 11 and is supported from an aircraft (not shown) by a pylon 12, part of which can be seen in the Figure. The engine 10 is of conventional configuration comprising a core engine 13 which powers a propulsive fan 14 at its upstream end. The core engine 13 is of smaller diameter than the fan 14 so that an annular fan duct 15 is defined between the radially outer surface of the core engine and the radially inner surface of the nacelle 11.
In operation, the fan 14 is rotated by the core engine 13 to draw air into the nacelle 11 through an intake at its upstream end 16. The air so drawn in is compressed by the fan 14 before being divided into two flows. The first flow is directed into the core engine 13 where it is compressed further before being mixed with fuel and the mixture ignited.
The resultant hot combustion products then expand through turbines within the core engine 13 before exhausting through a propulsive nozzle 17 at the downstream end of the core engine 13 to provide propulsive thrust.
The second flow of air compressed by the fan 14 is directed into the annular fan duct 15 from where it is exhausted at the downstream end of the nacelle 11 to provide additional propulsive thrust.
The radially outer surface of the core engine 13 and the radially inner surface of the nacelle 11 ie those surfaces which define the annular duct 15, are covered by a plurality of acoustic panels 18, part of one of which can be seen in Figures 2 to 4. The acoustic panels are all of generally similar construction and serve to provide sound attenuation of the engine 10.
Essentially, each acoustic panel 18 is made up of two layers 19 and 20 of a suitable sheet metallic material, such as stainless steel, between which is interposed a layer of metallic honeycomb material 21. The honeycomb material 21 is arranged so that each of its cells 22 interconnects the two sheet metal layers 19 and 20. Thus, each cell 22 is generally radially extending. The sheet metal layers 19 and 20 are bonded to the honeycomb material 21 by any convenient medium such as braze or a suitable adhesive.
The sheet metal layer 19 which confronts the annular duct 15, as can be seen in Figure 2, contains a large number of small holes 30 so that it is perforate. This is so as to provide an interconnection between the fan duct 15 and the honeycomb cells 22, thereby permitting the honeycomb cells 22 to provide sound attenuation of the air flow through the annular duct 15. Thus, the acoustic panels 18 are of conventional configuration and function in the conventional manner. Although in this particular case, the sheet metal layer 19 is perforate through having a plurality of holes 30 in it, it may be desirable in certain cases for the sheet 19 to be perforate through being formed from a naturally perforate material such as metallic gauze.
The present invention is concerned with the manner in which the acoustic panels 18 are attached to the core engine 13 and to the nacelle 11.
The acoustic panels 18 are situated in a vulnerable location which makes them prone to damage by objects that may be ingested by the engine 10. It is highly desirable, therefore, that the panels 18 are attached to the nacelle 11 and core engine 13 in such a manner that they could be easily removed and replaced in the event of such damage. The present invention is directed to such a manner of attachment.
Specifically, one or more of the honeycomb cells 22 in each acoustic panel 18 contains a cylindrical boss 23 which has a central passage 25 extending therethrough as can be seen in Figures 3 and 4. Each boss 23 is of such a diameter that it abuts each of the walls of the honeycomb cell 22 in which is situated and is of such a length that it abuts both of the layers 19 and 20 of sheet metal material. The end of the boss 23 which abuts the non-perforate sheet metal layer 20 is flat. However, the end of the boss 23 which abuts the perforate sheet metal layer is provided with a countersink indentation 24. Thus the indentation 24 is of frusto-conical configuration.
The portion of the perforate sheet metal layer 19 adjacent the boss indentation 24 is locally deformed to follow the frusto-conical configuration of the indentation 24. An aperture 26 is provided in the perforate sheet metal layer 19 which is aligned with the central passage 25 of the boss 23. Similarly an aperture 31 is provided in the other sheet metal layer 20 which is aligned with the central passage 25 of the boss 23.
The apertures 26 and 31 in the perforate sheet metal layer 19 and the other sheet metal layer 20 respectively, and the central passage 25 of the boss 23 are dimensioned to receive a screw 27. The screw 27 is provided with a countersink head 28 which locates in the locally deformed portion of the perforate sheet metal layer 19. The screw 27 extends through the boss 23 to engage within a support structure 29, thereby attaching the panel 18 to the support structure 29 while avoiding crushing of the honeycomb material 21. In this particular case, the support structure 29 is a part of the casing 30 which surrounds the fan 14.
However, it will be appreciated that it could be any other suitable part of the core engine 13 or nacelle 11.
Each acoustic panel 18 is provided with sufficient of the screws 27 to retain it in position on the engine 10.
It will be seen, therefore, that the head of the screw 28 is flush with the outer surface of the perforate sheet metal layer 19. Consequently, the screw 28 has little effect upon the airflow which operationally flows over the outer surface of the perforate sheet metal layer 19. A further advantage of the arrangement of the present invention is that the boss 23 and screw 28 combination only occupy a single cell 22 of the honeycomb material 21 rather than a group of adjacent cells 22. This means that there is only minimal disruption to the sound attenuation properties of the acoustic panels 18 by this particular way of attaching the panels 18 to a suitable support structure 29. Moreover, since the manufacturing step of filling several cells with a suitable filler material is avoided, manufacture of the acoustic panels 18 is simplified.

Claims (8)

1. An acoustic panel comprising a layer of cellular honeycomb material interposed between and interconnecting two layers of sheet material, one of which is perforate, whereby at least one of the cells of said cellular honeycomb material interconnects said layers of sheet material and contains a boss which abuts both of said layers of sheet material, said boss and the portions of said layers of sheet material adjacent thereto being apertured to receive common means for attaching said acoustic panel to a support structure.
2. An acoustic panel as claimed in claim 1 wherein said boss is of cylindrical configuration.
3. An acoustic panel as claimed in claim 2 wherein said boss engages the walls of the cell it occupies.
4. An acoustic panel as claimed in any one preceding claim wherein said boss and the portion of said perforate sheet it engages are provided with corresponding indentations which are so configured that said fastener is positioned flush with the external surface of said perforate sheet.
5. An acoustic panel as claimed in claim 4 wherein said indentations are of generally frusto-conical form.
6. An acoustic panel as claimed in any one preceding claim wherein said boss and sheets are so configured as to receive a fastener that is in the form of a screw having a countersink head.
7. An acoustic panel as claimed in any one preceding claim wherein said acoustic panel is configured so as to locate in the fan duct of a ducted fan gas turbine engine.
8. An acoustic panel substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
GB9624301A 1996-11-22 1996-11-22 Acoustic panel retention Expired - Fee Related GB2319589B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB9624301A GB2319589B (en) 1996-11-22 1996-11-22 Acoustic panel retention
FR9714435A FR2756332A1 (en) 1996-11-22 1997-11-18 ACOUSTIC PANEL SUPPORT

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9624301A GB2319589B (en) 1996-11-22 1996-11-22 Acoustic panel retention

Publications (3)

Publication Number Publication Date
GB9624301D0 GB9624301D0 (en) 1997-01-08
GB2319589A true GB2319589A (en) 1998-05-27
GB2319589B GB2319589B (en) 1999-06-16

Family

ID=10803321

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9624301A Expired - Fee Related GB2319589B (en) 1996-11-22 1996-11-22 Acoustic panel retention

Country Status (2)

Country Link
FR (1) FR2756332A1 (en)
GB (1) GB2319589B (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001034986A1 (en) * 1999-10-26 2001-05-17 Swales Aerospace Anti-distortion insert for mounting optical elements on a honeycomb panel
GB2407344A (en) * 2003-10-22 2005-04-27 Rolls Royce Plc Gas turbine engine casing liner mounting
US7255528B2 (en) * 2003-10-22 2007-08-14 Rolls-Royce Plc Liner for a gas turbine engine casing
WO2011034469A1 (en) * 2009-09-17 2011-03-24 Volvo Aero Corporation A noise attenuation panel and a gas turbine component comprising a noise attenuation panel
WO2012175850A1 (en) * 2011-06-24 2012-12-27 Safran Turbomachine casing acoustic panels fitted with improved attachment devices
EP3719793A1 (en) * 2019-04-05 2020-10-07 Rolls-Royce Corporation Acoustic panel assembly with reinforced lip

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3038942B1 (en) * 2015-07-17 2018-03-02 Safran Ceramics MECHANICAL JOINT ASSEMBLY COMPRISING AT LEAST ONE PIECE OF COMPOSITE MATERIAL

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2066354A (en) * 1979-12-18 1981-07-08 United Technologies Corp Sound absorbing structure for use in gas turbine engines
US5344280A (en) * 1993-05-05 1994-09-06 General Electric Company Impact resistant fan case liner

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2784758A (en) * 1955-07-28 1957-03-12 Frederick W Rohe Weld nut with welding flange and spacer shoulder
US5275529A (en) * 1992-03-16 1994-01-04 General Electric Company Sandwich panel joint

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2066354A (en) * 1979-12-18 1981-07-08 United Technologies Corp Sound absorbing structure for use in gas turbine engines
US5344280A (en) * 1993-05-05 1994-09-06 General Electric Company Impact resistant fan case liner

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001034986A1 (en) * 1999-10-26 2001-05-17 Swales Aerospace Anti-distortion insert for mounting optical elements on a honeycomb panel
US6394722B1 (en) 1999-10-26 2002-05-28 Swales Aerospace Anti-distortion insert for mounting optical elements on a honeycomb panel
GB2407344A (en) * 2003-10-22 2005-04-27 Rolls Royce Plc Gas turbine engine casing liner mounting
GB2407344B (en) * 2003-10-22 2006-02-22 Rolls Royce Plc A liner for a gas turbine engine casing
US7255528B2 (en) * 2003-10-22 2007-08-14 Rolls-Royce Plc Liner for a gas turbine engine casing
US7866939B2 (en) 2003-10-22 2011-01-11 Rolls-Royce Plc Liner for a gas turbine engine casing
WO2011034469A1 (en) * 2009-09-17 2011-03-24 Volvo Aero Corporation A noise attenuation panel and a gas turbine component comprising a noise attenuation panel
US8464831B2 (en) 2009-09-17 2013-06-18 Volvo Aero Corporation Noise attenuation panel and a gas turbine component comprising a noise attenuation panel
WO2012175850A1 (en) * 2011-06-24 2012-12-27 Safran Turbomachine casing acoustic panels fitted with improved attachment devices
FR2976974A1 (en) * 2011-06-24 2012-12-28 Safran DEVICE FOR ASSEMBLING ACOUSTIC PANELS OF A TURBOMACHINE NACELLE
EP3719793A1 (en) * 2019-04-05 2020-10-07 Rolls-Royce Corporation Acoustic panel assembly with reinforced lip
US11352953B2 (en) 2019-04-05 2022-06-07 Rolls-Royce Corporation Acoustic panel with reinforced lip

Also Published As

Publication number Publication date
GB9624301D0 (en) 1997-01-08
GB2319589B (en) 1999-06-16
FR2756332A1 (en) 1998-05-29

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20031122