Patent Grant
8550208
The subject matter disclosed herein relates generally to muffling systems, and, more specifically, to muffling devices capable of inducing high pressure drops and desirable flow properties.
In a gas turbine engine, air is pressurized in a compression module during operation. The air channeled through the compression module is mixed with fuel in a combustor and ignited, generating hot combustion gases which flow through turbine stages that extract energy therefrom for powering the fan and compressor rotors and generate engine thrust to propel an aircraft in flight or to power a load, such as an electrical generator.
In some gas turbine engines, a portion of the high-pressure air, such as, for example, bleed air from a compressor, may be extracted or bled from the compressor for various needs. These needs include, for example, compressor flow bleeding which may be used in order to improve operability as well as to provide turbine cooling, pressurize bearing sumps, purge air or provide aircraft environment control. The air may be bled off from the compressor using bleed slots located over specific portions or stages of the compressor.
The problem: In least some gas turbine engines, during engine operation occurring in some operating conditions, the compressor may pump more air than is required for needs including the combustion process. In order to manage operability of the engine and combustion performance, a portion of the excess bleed air from the compressor may be routed through bleed conduits and exhausted into the by-pass flow stream, engine exhaust, or to ambient. The pressure and temperature of the air stream bled from the compressor may be very high. For example, bleed air pressure may be greater than about 1375 kPa and the bleed air temperature may be greater than about 538 degrees C. A transient bleed valve system (TBV) system is sometimes used for bleeding and exhausting the air removed from the compressor. Certain conventional designs for bleed exhaust systems use large and/or heavy muffling devices to reduce the generated noise. For example, the exhaust area of some conventional bleed systems may be set to lower the flow velocity at the exhaust location to a level below that required to meet the acoustic limits for the application. The exhaust area, as well as the relatively gently expansions between the source pressure and exhaust, may contribute to the relatively large size and/or weight of these systems. In some applications (e.g., aircraft), it may be undesirable to use large and/or heavy components.
In addition, some conventional exhaust designs on aircraft may require extensive thermal shielding on other components near the exhaust location, once the exhaust velocities that meet the acoustic limits are achieved. Due to the nature of the high temperature air, once it is over-expanded to achieve lower velocities, the air it mixes with may overwhelm the bleed air, causing it to “lay down” on the surrounding structure around the engine. In some aircraft the surrounding structure may be made of lightweight composite material or of other metallic material with lesser temperature capability.
At least one solution for the above-mentioned problem(s) is provided by the present disclosure to include example embodiments, provided for illustrative teaching and not meant to be limiting.
An example muffling device according to at least some aspects of the present disclosure may include an inner flow conditioner shaped as a generally conical frustum including an upstream base and a downstream base. A diameter of the upstream base may be larger than a diameter of the downstream base. The inner flow conditioner may include an inlet approximate the upstream base, a generally circular inner flow conditioner downstream end wall having an inner flow conditioner downstream end wall area, the inner flow conditioner downstream end wall being generally orthogonal to a longitudinal axis of the conical frustum and comprising a plurality of generally longitudinally oriented inner flow conditioner downstream end wall holes, and an inner flow conditioner sidewall shaped generally as a truncated cone, the inner flow conditioner sidewall tapering inwardly from approximate the upstream base to approximate the inner flow conditioner downstream wall, the inner flow conditioner sidewall comprising a plurality of generally laterally oriented inner flow conditioner sidewall holes. The muffling device may include an exhaust can disposed substantially around the inner flow conditioner and shaped as a generally circular cylinder. The exhaust can may include a generally annular upstream end wall disposed approximate the upstream base of the inner flow conditioner and substantially circumscribing the upstream base of the inner flow conditioner, a generally circular exhaust screen comprising a plurality of exhaust screen holes, and a generally circular exhaust can sidewall extending from approximate the upstream end wall to approximate the exhaust screen. The inner flow conditioner and the exhaust can may be configured to conduct a fluid inward through the inlet into the inner flow conditioner, through the inner flow conditioner downstream end wall discharge openings and the inner flow conditioner sidewall discharge openings into the exhaust can, and outward through the exhaust screen discharge openings. The exhaust can and the inner flow conditioner downstream end wall may at least partially define a downstream end annular area therebetween. A ratio of the inner flow conditioner downstream end wall area to the downstream end annular area may be about 0.12 to about 0.97.
An example muffling device according to at least some aspects of the present disclosure may include an inner flow conditioner shaped as a generally conical frustum including an upstream base and a downstream base. A diameter of the upstream base may be larger than a diameter of the downstream base. The inner flow conditioner may include an inlet approximate the upstream base, a generally circular inner flow conditioner downstream end wall having an inner flow conditioner downstream end wall area, the inner flow conditioner downstream end wall being generally orthogonal to a longitudinal axis of the conical frustum and comprising a plurality of generally longitudinally oriented inner flow conditioner downstream end wall holes, and an inner flow conditioner sidewall shaped generally as a truncated cone, the inner flow conditioner sidewall tapering inwardly from approximate the upstream base to approximate the inner flow conditioner downstream wall, the inner flow conditioner sidewall comprising a plurality of generally laterally oriented inner flow conditioner sidewall holes. The muffling device may include an exhaust can disposed substantially around the inner flow conditioner and shaped as a generally circular cylinder. The exhaust can may include a generally annular upstream end wall disposed approximate the upstream base of the inner flow conditioner and substantially circumscribing the upstream base of the inner flow conditioner, a generally circular exhaust screen comprising a plurality of exhaust screen holes, and a generally circular exhaust can sidewall extending from approximate the upstream end wall to approximate the exhaust screen. The inner flow conditioner and the exhaust can may be configured to conduct a fluid inward through the inlet into the inner flow conditioner, through the inner flow conditioner downstream end wall discharge openings and the inner flow conditioner sidewall discharge openings into the exhaust can, and outward through the exhaust screen discharge openings. The exhaust can and the inner flow conditioner downstream end wall may at least partially define a downstream end annular area therebetween. A ratio of the downstream end annular area to the downstream end wall area may be proportional, by a factor of about 0.8 to about 1.9, to a ratio of an effective area of the inner flow conditioner sidewall holes to an effective area of the inner flow conditioner downstream end wall holes.
An example muffling device according to at least some aspects of the present disclosure may include an inner flow conditioner shaped as a generally conical frustum including an upstream base and a downstream base. A diameter of the upstream base may be larger than a diameter of the downstream base. The inner flow conditioner may include an inlet approximate the upstream base, a generally circular inner flow conditioner downstream end wall having an inner flow conditioner downstream end wall area, the inner flow conditioner downstream end wall being generally orthogonal to a longitudinal axis of the conical frustum and comprising a plurality of generally longitudinally oriented inner flow conditioner downstream end wall holes, and an inner flow conditioner sidewall shaped generally as a truncated cone, the inner flow conditioner sidewall tapering inwardly from approximate the upstream base to approximate the inner flow conditioner downstream wall, the inner flow conditioner sidewall comprising a plurality of generally laterally oriented inner flow conditioner sidewall holes. The muffling device may include an exhaust can disposed substantially around the inner flow conditioner and shaped as a generally circular cylinder. The exhaust can may include a generally annular upstream end wall disposed approximate the upstream base of the inner flow conditioner and substantially circumscribing the upstream base of the inner flow conditioner, a generally circular exhaust screen comprising a plurality of exhaust screen holes, and a generally circular exhaust can sidewall extending from approximate the upstream end wall to approximate the exhaust screen. The inner flow conditioner and the exhaust can may be configured to conduct a fluid inward through the inlet into the inner flow conditioner, through the inner flow conditioner downstream end wall discharge openings and the inner flow conditioner sidewall discharge openings into the exhaust can, and outward through the exhaust screen discharge openings. The exhaust can and the inner flow conditioner downstream end wall may at least partially define a downstream end annular area therebetween. The inner flow conditioner downstream end wall holes may have an inner flow conditioner downstream end wall hole diameter. The inner flow conditioner downstream end wall may be spaced from the exhaust screen by a dissipation distance. A ratio of the dissipation distance to the inner flow conditioner downstream end wall hole diameter may be greater than about 10.
The subject matter for which patent claim coverage is sought is particularly pointed out and claimed herein. The subject matter and embodiments thereof, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.
The present disclosure includes, inter alia, muffling systems, and more specifically muffling devices capable of inducing high pressure drops and desirable flow properties.
The present disclosure contemplates that modern, highly efficient turbofan engines may use high-pressure/high-temperature bleed from the aft compressor stages to improve operability and performance. This bleed air may be directed into the fan duct or other locations, which may generate additional noise during some phases of engine operation.
Some example embodiments according to the present disclosure provide a compact, lightweight transient/operability bleed exhaust muffling device (which may be referred to generally as a “pepperpot”) that has minimal acoustic impact. Acoustic benefit for the high pressure/temperature compressor discharge bleed may be achieved at a high exhaust velocity into the fan duct and, in some example embodiments, may use only a single flow conditioning element (which may be referred to as an “inner flow conditioner”) within the pepperpot body (which may be referred to as an “exhaust can”). Some such embodiments may be referred to as “single stage” muffling devices. The present disclosure contemplates that some “single stage” muffling devices are described in U.S. Provisional Patent Application No. 61/580,675, titled COMPACT HIGH-PRESSURE EXHAUST MUFFLING DEVICES, filed Dec. 28, 2011, and U.S. patent application Ser. No. 13/347,728, titled COMPACT HIGH-PRESSURE EXHAUST MUFFLING DEVICES, filed Jan. 11, 2012, which are incorporated herein by reference. The present disclosure contemplates that some other acoustic pepperpots may utilize multiple (e.g., three to five or more) inner flow conditioning elements, which may add weight to the engine.
In addition, the present disclosure contemplates that some other acoustically friendly pepperpots may necessitate extensive shielding on the thrust reverser structure to address thermal concerns. Some example embodiments according to the present disclosure may reduce or eliminate the need for such shielding by directing at least a substantial portion of the high-temperature bleed air generally to the middle of the cool fan duct flow, which may allow the hot plume to exit the fan duct without substantially impinging on thrust reverser or other aircraft surfaces.
In operation, air flows through fan blades 24 and is supplied to high-pressure compressor 14. The air discharged from fan assembly 22 is channeled to high-pressure compressor 14 where the airflow is further compressed and channeled to combustor 16. Products of combustion from combustor 16 are utilized to drive high-pressure turbine 18 and low-pressure turbine 20, and turbine 20 drives fan assembly 22 via shaft 31.
In an example gas turbine engine assembly 10, at certain operating conditions, a portion of the compressed air may be routed through the bleed system 40, thereby becoming bleed air 2. Bleed air 2 from high-pressure compressor 14 may enter a bleed flow conduit 44. Bleed air 2 may pass through the bleed flow conduit 44 and enter muffling device 50 that directs bleed air 2 into a flow path, such as the bypass flow path 4 and mixes that air with another flow, such as a fan flow stream 1. Flow through bleed flow conduit 44 may be controlled by a bleed air valve 45. Bleed flow conduit 44 may be made from a variety of materials, such as a metal, which may be selected to be capable of withstanding a bleed air 2 flow that is relatively hot and at high pressure.
Muffling device 50, described in more detail herein below, may be in flow communication with bleed flow conduit 44 such that the bleed air 2 is discharged as exit flow stream 5 into by-pass flow path 4, facilitating a reduction of the noise generated by the mixing of the exit flow stream 5 and fan flow stream 1.
As shown in
In some example embodiments according to at least some aspects of the present disclosure, an inner flow conditioner 110 may be disposed within exhaust can 102. Inner flow conditioner 110 may be generally in the form of a hollow, conical frustum arranged coaxially with exhaust can 102 about central axis 124. Inner flow conditioner 110 may include an inwardly tapering sidewall 112 and a downstream end wall 114, which may be generally circular. Sidewall 112 may be shaped generally as a truncated cone. Downstream end wall 114 may be generally orthogonal to central axis 124. Inner flow conditioner 110 may taper inwardly from an upstream base 136 (which may be substantially circumscribed by upstream end wall 126) to a downstream base 138 (which may be proximate downstream end wall 114). Sidewall 112 and downstream end wall 114 may at least partially define an interior 116 of inner flow conditioner 110. Sidewall 112 may include a plurality of generally laterally oriented holes 120 and/or downstream end wall 114 may include a plurality of generally axially oriented holes 122 through which pressurized air may be discharged into interior 108 of exhaust can 102. Inner flow conditioner 110 may be arranged to receive pressurized air from bleed flow conduit 44 through an inlet 118 (which may be proximate upstream base 136). Inner flow conditioner 110 may have an upstream base diameter 132 proximate inlet 118 and/or downstream base diameter 134 proximate downstream end wall 114. Upstream base diameter 132 may be larger than downstream base diameter 134. Inner flow conditioner 110 may be attached inside exhaust can 102 such that inlet 118 is disposed within upstream end wall 126 of exhaust can 102.
Downstream base 138 may at least partially define a downstream end wall area 133, which may be the generally axially downstream facing area of downstream end wall 114. Downstream base 138 and exhaust can 102 may at least partially define a downstream end annular area 135, which may be the generally axially downstream facing area between downstream end wall 114 and sidewall 128 of exhaust can 102. In some example embodiments, a ratio of downstream end wall area 133 to downstream end annular area 135 may be about 0.12 to about 0.97. In some example embodiments, a ratio of downstream end wall area 133 to downstream end annular area 135 may be about 0.16 to about 0.28. In some example embodiments, a ratio of downstream end wall area 133 to downstream end annular area 135 may be about 0.17 to about 0.20.
In operation, inner flow conditioner 110 and exhaust screen 102 may be configured to conduct pressurized air inward through inlet 118 into interior 116 of inner flow conditioner 110, through holes 120 and/or holes 122 of inner flow conditioner 110 into interior 108 of exhaust can 102, and outward through holes 106 of exhaust screen 104. In some example embodiments, interior 108 of exhaust can 102 may be substantially devoid of flow obstructions between holes 120 and holes 122 of inner flow conditioner and holes 106 of exhaust screen 104.
An example muffling device 50 may include holes 106, 120, 122 having individual hole sizes (e.g., diameters and/or slot length/width) and areas. An individual hole may have an effective area for fluid flow that differs from its measurable physical area. A hole's effective area for fluid flow may be determined by known methods, and may depend on the size and shape of the hole. A plurality of holes, e.g., holes 106 of exhaust screen 104, may have an effective area for fluid flow that may be calculated using known methods. For example, holes 120 of sidewall 112 of inner flow conditioner 110 may have an effective flow area and/or holes 122 of downstream end wall 114 of inner flow conditioner 110 may have an effective flow area.
In some example embodiments according to at least some aspects of the present disclosure, a ratio of downstream end annular area 135 to downstream end wall area 133 may be proportional, by a factor of about 0.8 to about 1.9, to a ratio of the effective area of holes 120 of sidewall 112 of inner flow conditioner 110 to the effective flow area of holes 122 of downstream end wall 114 of inner flow conditioner 110. Expressed mathematically,
where F, in some example embodiments, may be about 0.8 to about 1.9. In some example embodiments, F may be about 0.88 to about 1.58. In some example embodiments, F may be about 0.97 to about 1.26.
In some example embodiments according to at least some aspects of the present disclosure, a ratio of an effective flow area of the holes (e.g., holes 120 and holes 122) of an inner flow conditioner (e.g., inner flow conditioner 110) to an effective flow area of an inlet (e.g., inlet 118) may be about 0.7 to about 1.2. In some example embodiments according to at least some aspects of the present disclosure, a ratio of an effective flow area of the holes of the inner flow conditioner to an effective flow area of the inlet may be about 0.76 to about 0.91.
In some example embodiments according to at least some aspects of the present disclosure, inner flow conditioner 110 may be disposed within an exhaust can 102 such that airflow through holes 122 of downstream end wall 114 substantially dissipates before it reaches exhaust screen 104 of exhaust can 102. For example, downstream end wall 114 may be spaced from exhaust screen 104 by a dissipation distance 140. One or more holes 122 through downstream end wall 114 may have a hole diameter 142. In some example embodiments, a ratio of dissipation distance 140 to hole diameter 142 may be greater than 10. In some example embodiments, the ratio of dissipation distance 140 to hole diameter 142 may be greater than 15. In some example embodiments, the ratio of dissipation distance 140 to hole diameter 142 may be greater than 20.
Some example embodiments according to at least some aspects of the present disclosure may be arranged such that air flow 144 approaching exhaust screen 104 may be substantially uniform across diameter 130 of exhaust can 102.
Although some example embodiments have been described in connection with discharging exit flow stream 5 into by-pass flow path 4, it is within the scope of the disclosure to direct exit flow stream 5 elsewhere. For example, some muffling devices according to the present disclosure may be mounted at the engine pylon, the turbine rear frame, and/or core nozzle/center bleed tube. Some example embodiments may be arranged to direct exit flow stream 5 generally behind gas turbine engine assembly 10.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 700785 | Kull | May 1902 | A |
| 759964 | Bonar | May 1904 | A |
| 1473349 | Kach | Nov 1923 | A |
| 1539595 | Powell | May 1925 | A |
| 1697794 | Stranahan | Jan 1929 | A |
| 1794276 | Bowes | Feb 1931 | A |
| 1839192 | Baits | Jan 1932 | A |
| 2701557 | Ramey | Feb 1955 | A |
| 2716463 | Latulippe | Aug 1955 | A |
| 2919761 | Smith | Jan 1960 | A |
| 2929248 | Sprenkle | Mar 1960 | A |
| 3016972 | Dugas | Jan 1962 | A |
| 3092206 | Rene Moreau | Jun 1963 | A |
| 3105570 | Bezemes | Oct 1963 | A |
| 3120877 | Morris et al. | Feb 1964 | A |
| 3159238 | Shearer | Dec 1964 | A |
| 3196977 | Sanders | Jul 1965 | A |
| 3338331 | Jettinghoff | Aug 1967 | A |
| 3398881 | Greenberg et al. | Aug 1968 | A |
| 3493169 | Abild et al. | Feb 1970 | A |
| 3545492 | Scheid | Dec 1970 | A |
| 3572391 | Hirsch | Mar 1971 | A |
| 3632223 | Hampton | Jan 1972 | A |
| 3635309 | Nemcansky et al. | Jan 1972 | A |
| 3665965 | Baumann | May 1972 | A |
| 3692140 | Smith | Sep 1972 | A |
| 3777489 | Johnson et al. | Dec 1973 | A |
| 3840051 | Akashi et al. | Oct 1974 | A |
| 3894610 | Halter et al. | Jul 1975 | A |
| 3945759 | Bobo | Mar 1976 | A |
| 3951566 | Mattei et al. | Apr 1976 | A |
| 3964519 | De Baun | Jun 1976 | A |
| 4022112 | Putt et al. | May 1977 | A |
| 4072170 | Sagner et al. | Feb 1978 | A |
| 4113050 | Smith | Sep 1978 | A |
| 4128769 | Bons et al. | Dec 1978 | A |
| 4130173 | Cooksey | Dec 1978 | A |
| 4132285 | Milde et al. | Jan 1979 | A |
| 4142413 | Bellinga | Mar 1979 | A |
| 4156344 | Cuthbertson et al. | May 1979 | A |
| 4177780 | Pellerin | Dec 1979 | A |
| 4244440 | Matta et al. | Jan 1981 | A |
| 4244441 | Tolman | Jan 1981 | A |
| 4375841 | Vielbig | Mar 1983 | A |
| 4463552 | Monhardt et al. | Aug 1984 | A |
| 3191630 | Demyan | Jun 1985 | A |
| 4537277 | Bryce | Aug 1985 | A |
| 4610326 | Kirchweger et al. | Sep 1986 | A |
| 4685533 | Piesik | Aug 1987 | A |
| 4890691 | Ching-ho | Jan 1990 | A |
| 4979587 | Hirt et al. | Dec 1990 | A |
| 5205719 | Childs et al. | Apr 1993 | A |
| 5261228 | Shuba | Nov 1993 | A |
| 5266754 | Swift | Nov 1993 | A |
| 5327941 | Bitsakis et al. | Jul 1994 | A |
| 5428954 | Cowan, Sr. | Jul 1995 | A |
| 5429102 | Edwards et al. | Jul 1995 | A |
| 5491310 | Jen | Feb 1996 | A |
| 5495872 | Gallagher et al. | Mar 1996 | A |
| 5557917 | Jaw | Sep 1996 | A |
| 5758488 | Batey | Jun 1998 | A |
| 5760348 | Heuser | Jun 1998 | A |
| 5859393 | Cummins et al. | Jan 1999 | A |
| 6145544 | Dutertre et al. | Nov 2000 | A |
| 6343672 | Petela et al. | Feb 2002 | B1 |
| 6415747 | Asano et al. | Jul 2002 | B1 |
| 6558137 | Tomell et al. | May 2003 | B2 |
| 6565313 | Nikkanen et al. | May 2003 | B2 |
| 6588195 | Negulescu | Jul 2003 | B2 |
| 6695094 | Moffat et al. | Feb 2004 | B2 |
| 6776589 | Tomell et al. | Aug 2004 | B2 |
| 6880579 | Boger | Apr 2005 | B2 |
| 6968923 | Schmaeman | Nov 2005 | B2 |
| 6981842 | D'Angelo et al. | Jan 2006 | B2 |
| 7089963 | Meheen | Aug 2006 | B2 |
| 7146961 | Westcott | Dec 2006 | B1 |
| 7210912 | Tomell et al. | May 2007 | B2 |
| 7267297 | Campbell et al. | Sep 2007 | B2 |
| 7344107 | Campbell et al. | Mar 2008 | B2 |
| 7364116 | Nguyen et al. | Apr 2008 | B2 |
| 7367424 | Brown et al. | May 2008 | B2 |
| 7387188 | Keller et al. | Jun 2008 | B2 |
| 7387489 | Appleby et al. | Jun 2008 | B2 |
| 7431125 | Williams | Oct 2008 | B2 |
| 7448469 | Seyler et al. | Nov 2008 | B2 |
| 7451855 | Wang | Nov 2008 | B2 |
| 7513119 | Zielinski et al. | Apr 2009 | B2 |
| 7611093 | Campbell et al. | Nov 2009 | B2 |
| 7730995 | Hunt et al. | Jun 2010 | B2 |
| 7762374 | Turner et al. | Jul 2010 | B2 |
| 7765784 | Lwasa et al. | Aug 2010 | B2 |
| 7797945 | Appleby et al. | Sep 2010 | B2 |
| 7798285 | Chiou et al. | Sep 2010 | B2 |
| 7891605 | Nguyen et al. | Feb 2011 | B2 |
| 7921652 | Kirby | Apr 2011 | B2 |
| 7946104 | Frank et al. | May 2011 | B2 |
| 8016071 | Martinus et al. | Sep 2011 | B1 |
| 8128347 | Sokhey | Mar 2012 | B2 |
| 8307943 | Klasing et al. | Nov 2012 | B2 |
| 8430202 | Mason et al. | Apr 2013 | B1 |
| 20040238123 | Becknell et al. | Dec 2004 | A1 |
| 20050067218 | Bristow et al. | Mar 2005 | A1 |
| 20100043447 | Kirby | Feb 2010 | A1 |
| 20100236256 | Hussain et al. | Sep 2010 | A1 |
| 20110265490 | Klasing et al. | Nov 2011 | A1 |
| 20120006615 | Klasing et al. | Jan 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 2136053 | Dec 2009 | EP |
| 2184447 | May 2010 | EP |
| 2184448 | May 2010 | EP |
| Entry |
|---|
| US 7,270,294, 09/2007, Campbell (withdrawn) |
| Phong et al., “Noise Reduction of a Turbofan Bleed Valve,” 50th AIAA Aerospace Sciences Meeting, Nashville, Tennessee, Jan. 9-12, 2012. |
| GB Search Report and Opinion issued Oct. 26, 2011, in corresponding Application No. GB1112835.2. |
