IN SITU OPTICAL PROBE AND METHODS

RELATED APPLICATIONS

[0001] This application claims priority from United States Provisional Patent

Application Serial No. 60/980,315, filed October 16, 2007, entitled "Single-Ended Probe and Methods for Spectroscopic Measurements in the Combustion Zone of a Gas Turbine Engine," which is hereby incorporated by reference.

STATEMENT REGARDING GOVERNMENT RIGHTS

[0002] This invention was made with government support under Contract FA

8650-06-C-2618 awarded by the Air Force Research Laboratory of the Department of the Air Force. The government has certain rights to this invention.

TECHNICAL FIELD

[0003] The present invention is directed toward an in- situ probe and a method for monitoring a combustion process, and more particularly toward a method and apparatus for spectroscopic measurements of combustion properties in a confined measurement area such as a jet engine afterburner (augmentor).

BACKGROUND OF THE INVENTION

[0004] Laser-based spectroscopic instruments have been implemented in a variety of environments to extract measurement data. Laser-based measurement apparatus can be implemented in situ and offer the further advantage of high speed feedback suitable for dynamic process control. One technique for measuring combustion species such as gas composition, temperature and other combustion parameters (collectively, "combustion properties") utilizes Tunable Diode Laser Absorption Spectroscopy (TDLAS). TDLAS is typically implemented with diode lasers operating in the near-infrared and mid-infrared spectral regions. Suitable lasers have been extensively developed for use in the telecommunications industry and are, therefore, readily available for TDLAS. Various techniques for TDLAS which are more or less suitable for sensing control of combustion processes have been developed. Commonly known techniques are wavelength modulation spectroscopy and direct absorption spectroscopy. Each of these techniques is based upon a predetermined relationship between the quantity and nature of laser light received by a

detector after the light has been transmitted through an area of interest for measurement of combustion properties (a "measurement area") which may include but is not limited to a combustion zone or combustion chamber, and absorbed in specific spectral bands which are characteristic of the combustion species present in the combustion zone. The absorption spectrum received by the detector is used to determine the combustion properties, including the quantity of the combustion species under analysis and associated combustion parameters such as temperature.

[0005] One particularly useful implementation of TDLAS utilizes wavelength- multiplexed diode laser measurements in order to monitor multiple combustion species and combustion parameters. One such system is described in PCT/US2004/010048 (International Publication No. WO 2004/090496) entitled "Method and Apparatus for the Monitoring and Control of Combustion" ("WO '496"), the content of which is incorporated by reference in its entirety herein.

[0006] Determining combustion properties can be used to improve combustion efficiency or reduce combustion instability in, for example, an afterburner of a jet engine, while simultaneously reducing the harmful emissions such as nitrogen oxides. Monitoring combustion properties within the afterburner section of a jet engine also has the potential to reduce a combustion phenomenon known as screech in which combustion instabilities at audible frequencies are reinforced and amplified by virtue of the fact that the afterburner structure serves as a remarkably good resonator. Screech can become so intense that it can severely damage or destroy the engine in short order. Screech can either be studied in an actual engine or in ground test rigs that are set up to mimic the operation of an afterburner. As used herein, "afterburner" is intended to mean an actual afterburner of a turbine jet engine under ground test or a ground test rig, unless the context clearly excludes ground test rigs. "Jet engine" means a turbine jet engine which may or may not include an afterburner.

[0007] While monitoring combustion properties in an afterburner would appear to have many potential benefits, making the measurements has proven extremely difficult. The difficulty stems primarily from the difficulty of obtaining optical access for in situ measurements. For an afterburner application, the optical access required is a penetration or penetrations in the engine casing through which one can direct a laser beam over a line of sight. Normally, this requires two penetrations, one for a transmitting optic and one for a receiving optic. This is very difficult to arrange in an operating afterburner even during ground test due to the harsh nature of the engine environment, the limited space available

for monitoring components and the need to minimize impact on critical components. It also limits the ability to obtain any kind of spatial resolution in the measurements since both the transmitting and receiving optic are nominally in a fixed position. Furthermore, the path length between transmitting and receiving optics is typically too great to provide suitable spatial resolution to study localized phenomena that are believed to cause screech. [0008] The present invention is directed toward overcoming one or more of the problems discussed above.

SUMMARY OF THE INVENTION

[0009] A first aspect of the invention is a method of measuring a combustion property within a select zone of a measurement area of a jet engine. The method comprises providing a port in an outer casing of the jet engine and providing an elongate housing defined by a housing wall having at its distal end a transmitting optic and a receiving optic. The distal end of the elongate housing is positioned to extend through the port in the outer casing and into a select zone within a measurement area inside the jet engine, the select zone comprising less than an entire width of the measurement area. The method further includes reflecting a beam from the transmit optic to the receiving optic off a reflecting surface in the select zone of the measurement area. [0010] In one embodiment the method may further include cantilevering the reflective surface from the distal end of the housing. The method may further include cooling an interior of the elongate housing to prevent thermal damage to the transmitting optic and the receiving optic. The cooling step may comprise providing a cooling jacket within the housing defined by an inner wall of the housing and the housing wall and circulating coolant through the cooling jacket. The cooling step may further comprise flowing a cooling gas in communication with the transmitting and receiving optics within an interior volume within the housing defined by the inner wall of the cooling jacket. [0011] In one embodiment the beam transmitted from the transmitting optic comprises a plurality of discrete multiplexed wavelengths. Such an embodiment would further include demultiplexing the beam received by the receiving optic into discrete wavelengths and detecting at least one discrete wavelength of the demultiplexed beam. This embodiment may further include determining the concentration of at least one combustion property based on the intensity of a discrete wavelength. This embodiment may further include determining the concentration of a plurality of combustion species based upon the intensity of a plurality of discrete wavelengths.

[0012] In one embodiment, the method further comprises reflecting the beam off more than one reflecting surface before directing it to the receiving optic. [0013] In one embodiment, the method further includes positioning the distal end of the elongate housing in a second select zone within the measurement area and reflecting a beam from the transmit optic to the receiving optic off the reflecting surface in the second select zone. In this embodiment, the repositioning step may be performed by moving the distal end of the probe linearly along an axis of the elongate housing. Alternatively or in addition, the repositioning step may comprise moving the distal end of the probe radially by gimballing the elongate housing within the port. [0014] In all embodiments, the measurement area may be within an afterburner of a jet engine.

[0015] A second aspect of the invention is an apparatus for measuring combustion properties within a measurement area. The apparatus comprises an elongate housing comprising a housing wall, the elongate housing having a distal end. A transmitting and receiving optics pair within is provided the distal end of the housing in optical communication with a volume outside the housing. A reflective surface is cantilevered from the distal end of the housing in the volume outside the housing, the reflective surface being configured to reflect a beam in optical communication from the transmitting optic to the receiving optic. The apparatus may further include means for cooling the interior of the housing. The means may comprise an inner wall within the housing cooperating with the housing wall to define a cooling jacket therebetween, and means for flowing a coolant through the cooling jacket. The cooling means may further comprise an inner volume defined by the inner wall, the transmitting and receiving optics pair residing within the inner volume and means for flowing a cooling gas through the inner volume. [0016] In one embodiment, the apparatus further comprises a laser generating beam of light optically coupled to the transmitting optic. The embodiment may further include a detector optically coupled the receiving optic. In another embodiment the apparatus further comprises the a plurality of lasers each generating a beam of a discrete wavelength and a multiplexer optically coupled to the plurality of lasers for multiplexing the discrete wavelength beams into a multiplexed beam, the multiplexer being optically coupled to the transmit optic to convey the multiplexed beam thereto. Such an embodiment may further comprise a demultiplexer optically coupled to the receiving optic and a detector optically coupled to the demultiplexer for detecting each discrete wavelength received by the receiving optic. Such an embodiment may further comprise a

computer coupled to each detector, the computer being programmed to determine a concentration of at least one combustion species based upon an output of the detectors. [0017] In each embodiment of the apparatus, the reflective surface may be treated to provide a desired property to the reflected beam. The reflective surface may be treated to provide a Lambertian reflection.

[0018] In any of the embodiments of the apparatus, at least one other reflective surface is in optical communication with the reflective surface to further reflect the transmitted beam before it is optically communicated to the receiving optic. [0019] In all embodiments of the apparatus, a distance between the distal end of the probe and the reflective surface is sufficient to provide a suitable signal for detection of a desired combustion property while facilitating a spatial resolution to detect the combustion property in several zones within the measurement area. In one embodiment the distance is less than about two inches. In another embodiment the distance is less than about one inch. The effective optical distance can be increased by further reflection of the transmitted beam before it reaches the receiving optic without altering the distance between the distal end of the housing and the reflective surface so as to maintain a desired spatial resolution.

[0020] The method and apparatus disclosed herein allows for measurement of combustion properties in discrete zones within a measurement area of a jet engine. Those embodiments providing cooling of the interior of the apparatus housing enhance the durability and length of time the apparatus can be used in the harsh environment of a jet engine and the afterburner portion of jet engine. Use of the cantilevered reflecting surface facilitates measurement of a number of zones within a measurement area of a jet engine. In this manner, spatially localized anomalies can be identified to enable redesign of jet engine or afterburner to correct the anomalies. Reflection of the transmit beam acts to increase the path length, thus the strength of a signal received by a receiving optic, without sacrificing spatial resolution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Fig. 1 is a perspective view of an apparatus for measuring combustion properties within a measurement area, and more particularly of a probe comprising the apparatus;

[0022] Fig. 2 is a partial cross-sectional view of the apparatus of Fig. 1 taken along line 2-2 of Fig 1;

[0023] Fig. 3 is a schematic representation of an alternate embodiment of cantilevered reflector of the apparatus depicted in Figs. 1 and 2;

[0024] Fig. 4 is a schematic diagram of a distal end of the apparatus of Fig. 1 illustrating the optical components;

[0025] Fig. 5 is a schematic representation of the apparatus of Fig. 1 incorporated into a test fixture;

[0026] Fig. 6 is a schematic representation of an embodiment of an apparatus for measuring combustion properties within a measurement area using a single wavelength beam input;

[0027] Fig. 7 is a schematic representation of an embodiment of an apparatus for measuring combustion properties within a measurement area using multiplexed beam input.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Fig. 1 is perspective view of a probe portion 10 of an apparatus for measuring combustion properties in a measurement area. The probe portion 10 comprises an elongate outer housing 12 comprising a housing wall having a distal end 14. An inner housing 16 comprising an inner wall is coaxially received in the outer housing 12. A cooling liquid inlet 18 extends radially from a proximal portion of the elongate outer housing 12 and cooling liquid outlet 20 also extends radially from the proximal end of the elongate outer housing 12. A cooling gas inlet 22 extends radially from the wall of the inner housing 16. A single mode transmitting fiber 24 and a multi-mode receiving fiber 26 extend from a proximal end of the inner housing 16. A cantilevered fitting 27 extends from the distal end 14 of the outer housing 14.

[0029] Fig. 2 is a partial cross-section of the probe portion of the apparatus for measuring combustion properties within a measurement area of Fig. 1 taken along lines 2- 2 of Fig. 1. As seen in this cross-section, the elongate outer housing 12 concentrically receives the elongate inner housing 16. A spiral insert 28 functions to maintain a space between the inner wall of the inner housing 16 and the outer housing 12. This space functions to form a cooling jacket about the inner periphery of the outer housing 12. The spiral insert 28 is configured to promote the flow of a cooling liquid such as water from the cooling liquid inlet 18 to the cooling liquid outlet 20 depicted in Fig. 1. The spiral insert 28 further functions to cause turbulence in the liquid flow to improve its heat transfer properties. An inner volume 30 is defined by the inner wall of the inner housing

16. Received within this inner volume 30 at the distal end of the housing 14 are transmitting optics 32 and receiving optics 34. A cover plate 36 substantially closes the distal end of the probe portion 10 with the exception of an axial orifice 38 along an optical axis of the transmitting optics 32 and the receiving optics 34.

[0030] A reflector 40 having a reflecting surface 42 extends in a cantilevered fashion from distal end 14 of the elongate outer housing 12. The reflector 40 is supported by the cantilevered fitting 27 which includes a collar 46 receiving the distal end 14 of the elongate outer housing 12 and a pair of supports 48 (one shown in Figs. 1 and 2) spaced approximately 180° apart from each other between the reflector 40 and the collar 46. Cantilevered fitting 44 is preferably made of a stable heat resistant material such as a ceramic, for example, alumina. The reflector 40 is also preferably made of a stable, heat resistant, yet highly reflective material, such as iridium.

[0031] The transmitting optics 32 comprise a single mode transmitting fiber 24 coupled to transmitting ferrule 50. The transmitting ferrule 50 positions a distal end of the transmit fiber 24 to emit a beam of light optically coupled to the single mode transmit fiber from a laser as described herein. A collimating lens 52 provides for collimation of the light transmitted from the transmission fiber 24. A transmitting/receiving lens 54 is in turn optically coupled to the collimating lens 52. The receiving optics 34 comprises the transmitting/receiving lens 54, a collimating lens 56 and the multimode receiving fiber 26 supported by a receiving ferrule 58. The collimating lenses 52, 56 may be two identical spherical ball lenses which have been ground flat on two sides and then glued together in a sandwich. Collimating lenses thus prepared may be easily mounted and will provide for the minimization of the distance between the ferrules 50, 58 when combined within the distal end of the inner volume 30 as illustrated in Fig. 2. Thus, the overall size of the probe portion of the apparatus can be minimized. Those skilled in the art will appreciate that other types of lenses may be used to collimate and couple light to and from the optical fibers 24, 26. In addition, the collimating lenses 52, 56 may be separate structures or may be fabricated directly onto the free ends of the fibers 24, 26. Preferably, the collimating lenses are configured to provide for collimation and coupling of light to and from a fiber even though the fiber is somewhat misaligned from a desired optical axis. [0032] The transmitting/receiving lens 54 through which the transmitting beam 60 and the receiving beam 64 are received (see Fig. 4) preferably provides for an optical layout known as Cat's Eye Geometry. Cat's Eye Geometry occurs when the focal length of the transmitting/receiving lens 54 is approximately equal to the spacing between the

probe and the reflecting surface 42 off which the transmitting beam 62 is reflected. A Cat's Eye Geometry has the advantage of being relatively tolerant of misalignment between the probe and the reflective surface 42 such as might be caused by vibration in a jet engine.

[0033] Cat's Eye Geometry may be implemented with a single lens having a focal length equal to or nearly equal to the desired distance between the lens and the reflecting surface 42. Alternative embodiments may include a more sophisticated transmitting/receiving lens 52 having a spherical surface or additional lens elements. For instance, the focus of the probe could be increased with a more sophisticated transmitting/receiving lens 54 leading to greater tolerance for variables such as change in probe reflecting surface 42 distance resulting from thermal expansion of the supports 48. [0034] In addition to flow of cooling water through the water jacket defined between the inner and outer housings, additional cooling is provided by flowing a cooling gas from the cooling gas inlet 22 through the inner volume 30, across the transmitting and receiving optics 32, 34 and out the orifice 38. The cooling gas is preferably an inert gas such as nitrogen. The orifice 38 is selected to be of a size sufficient to provide optical communication between the transmit and receiving optics 32, 34 while minimizing its outer diamater. Cooling gas is flowed through the probe at a rate sufficient to provide the necessary cooling, but not so fast as to cause turbulence near the axial orifice 38 which can disrupt the integrity of the optical signal. As depicted in Fig. 2, the reflector 40 is fixedly attached by the cantilevered fitting 44 to the distal end of the probe. One potential problem with this configuration is potential misalignment between the reflecting surface 42 and the transmitting and receiving optics 32, 34. To ease optical alignment, the reflector 40 may have a spherical backing 68 as depicted in Fig. 3. The spherical backing 68 may be received in an opening or corresponding receptacle form in a housing 69. As shown on Fig. 3 the gimbaled adjustment of the reflecting surface 42 may be accomplished by advancing or rotating the spherical backing 68 by means of a small handle 70. Alternatively the adjustment of the reflecting surface 42 may be accomplished by electromechanical actuators, solenoids, or other types of automated or semi- automated drives. After adjustment, the spherical backing 68 may be locked in position by a clamp, locking screw or similar clamping structure (not shown on Fig. 3). It is important to note that the gimbaled mount including the spherical backing 68 as shown in Fig. 3 is merely one representative embodiment of an alignment adjustment mechanism. Similar adjustment functionality could be implemented with tip tilt stages, flexible members,

hinges, spring loaded actuation platforms or other mechanical or electromechanical devices which provide for the adjustment of the angular alignment of the reflecting surface 42.

[0035] The reflective surface 42 may be subjected to a treatment to provide a desired property to the reflected beam. For instance, the surface may be highly polished to enhance specular reflection. Specular reflection as defined herein is reflection from a smooth surface, such as a mirror, which tends to maintain the integrity of the incident beam wave front.

[0036] Alternatively, the reflective surface 42 may be treated to enhance or provide a predominantly Lambertian reflection. Lambertian reflection occurs when the incident beam is scattered such that the apparent brightness of the beam on the reflective surface 42 is approximately the same to an observer regardless of the observer's angle of view. Thus, Lambertian reflection is a diffuse reflection. Lambertian reflection from the reflective surface 42 will tend to decrease the intensity of the reflected beam 64. However, Lambertian reflection will tend to overcome minor misalignments between the transmission and receiving optics 32, 34, respectively. Lambertian reflection may be enhanced by bead blasting, sanding, painting or otherwise treating the reflective surface 42 to provide for a diffuse reflection.

[0037] Fig. 5 illustrates an embodiment of an apparatus for measuring combustion properties within a measurement area incorporated into a test fixture 76. The probe portion 10 is depicted substantially as described above with regard to Figs. 1 and 2 using identical reference numbers. In this embodiment the test fixture 76 comprises an outer casing 78 from which a support bracket 80 extends. The support bracket 80 supports a motorized drive 82. The motorized drive 82 in turn is coupled by a link 84 to the outer housing 12. The outer housing 12 in turn is received in a port 86 in the outer casing 78. This configuration of the test fixture 76 allows for automated translational movement of the sensing region 71 defined between the distal end of the probe and reflecting surface 42 axially within a measurement area 72 of a combustion process. In other embodiments, the probe 10 may also be gimbaled about the port 86 to allow for access to select zones within the measurement area that are not solely along the axis 90 of the probe 10 illustrated in Fig. 5.

[0038] As discussed above, the space between the reflecting surface 42 and the distal end of the probe 14 forms the sensing region 71. The probe is configured so that the sensing region 71 can be moved to select zones of a measurement area to measure

combustion properties within the select zone. A distance between the distal end of the probe and the reflective surface is selected to be sufficient to provide a suitable signal for detection of desired combustion property while facilitating a spatial resolution to detect the combustion property in several zones within the measurement area. For example, referring to Fig. 5, the measurement area 72 is within a flow of combustion gases illustrated by the arrow 73. Movements of the probe 10 translationally along the axis 90 by the motor 82 allows measurements of various zones within the sensing region 71. In the embodiments illustrated in Figs. 1-5 providing a single reflective surface 42 between the transmit and receive optic, a distance of less than about two inches is believed to provide a suitable signal for detection of desired combustion properties while facilitating reasonable spatial resolution. A distance of less than about one inch is also believed to provide a suitable signal for detection of a desired combustion property while having a further advantage of facilitating greater spatial resolution to detect the combustion property in smaller zones within the measurement area. Other embodiments including more than one reflector to increase the effective length of the transmitting/receiving beams 60, 64 within the sensing region 71 are considered to be within the scope of the invention. For example, the outside end of the cover plate 36 could be made reflective and the reflective surface 42 configured to bounce the transmitting beam 60 off of the cover plate 36 to form a W-beam configuration effectively doubling the beam length within the sensing region 71 depicted in Fig. 4.

[0039] It should be appreciated that while a test fixture 76 is illustrated in Fig. 5, the outer casing 78 could be outer casing of a jet engine, including the outer casing of an afterburner of a jet engine. Thus, the apparatus depicted in Fig. 5 could be deployed, for example, in ground testing combustion properties within an afterburner of a jet engine, such as a military jet engine.

[0040] Fig. 6 illustrates schematically the embodiment in the form of sensing apparatus 92 for sensing and monitoring of a combustion process. The apparatus 92 comprises a tunable diode laser 94 that is optically coupled to optical fiber 24, which may be a single mode optical fiber. The optical fiber 24 is further optically coupled to a transmitting optic 32 which may include a collimating lens or other optic suitable for producing a collimated transmitted beam 60. As used herein, "coupled" or "optically coupled" or "in optical communication with" is defined as a functional relationship between counterparts where light can pass from a first component to a second component either through or not through intermediate components or free space. The transmitting

optic 32 and the receiving optic 34 are optically coupled to a port 86 in an outer casing of a jet engine, for example, an outer casing of an afterburner. The beam 60 is transmitted off the reflecting surface 42 to be received by the receiving optic 34, thus defining a sensing region 71.

[0041] The receiving optic 34 is optically coupled to optical fiber 26 which may be a multi-mode optical fiber. Optical fiber 26 is optically coupled to a detector 96, which typically is a photodetector sensitive to the frequency of laser light generated by laser 94. The detector 96 generates an electrical signal based upon the nature and quantity of the light transmitted to the detector 96. The electrical signal from the detector 96 is digitized and analyzed in a computer or data processing system 98. The computer 98 is programmed to determine a combustion property, such as a concentration of at least one combustion species, based upon the output of the detector. The detector may further be programmed to control engine input parameters such as air and fuel provided to a combustion zone as a function of the concentration of the combustion species, as illustrated by the arrow 100. Alternatively, or in combination, the computer 98 may be programmed to determine an engine malfunction based upon the concentration of a combustion species and produce a warning signal.

[0042] The embodiments contemplate the use of fiber optic coupling to the electronic and optical components on both the transmitting and receiving sides of the probe portion 10 to allow delicate temperature sensitive apparatus such as the tunable diode laser 94, the detector 96 and the data processing system or computer 98, to be located in a suitable operating environment away from the measurement area. Thus, only the relatively most robust transmitting and receiving optics 32, 34 need to be situated near the hostile environment of the measurement area.

[0043] Fig. 7 schematically illustrates a multiplexed sensing apparatus 101. As throughout the specification, like reference numbers refer to the same elements described herein. In this embodiment of a plurality of tunable diode lasers 94A-94D are optically coupled to an optical fiber 102 (which may be a single mode optical fiber) and routed to a multiplexer 104. Each of the tunable diode lasers 94A-94D output a beam at a distinct select frequency. Within the multiplexer 104 the laser light from some or all of the tunable diode lasers 94A-94D is multiplexed to form a multiplexed beam having multiple select frequencies. The multiplexed beam is optically coupled to a transmit fiber 24 transmitted to the transmitting optic 32. A receiving optic 34 forms a transmitting/receiving optics pair with the transmitting optic 32. The

transmitting/receiving optics pair 32, 34 are optically coupled to port 86 in a casing of a gas turbine engine as described above with respect to Fig. 6. As with Fig. 6, the transmitted beam 60, which in this case is a multiplexed beam, is reflected off the reflection surface 42 and received by the receiving optic 34, thus defining the sensing region 71. The receiving optic 34 communicates with the demultiplexer 106 via the transmitting optical fiber 26, which may be a multi-mode optical fiber. The demultiplexer 106 demultiplexes the multiplexed reflected beam 64 into discrete wavelengths and each wavelength is optically communicated to a corresponding detector 96A-96D, which in turn is coupled to the data processor or computer 98, which may be programmed as discussed above with respect to the computer 98 of Fig. 6.

[0044] The embodiment illustrated in Fig. 7 may include any number of tunable diode lasers 94A-94D and detectors 96A-96D generating and detecting a variety of wavelengths, but only four are illustrated for the sake of simplicity. [0045] Above various surface treatments which can be applied to the reflecting surface 42 are discussed. In addition, a reflecting surface could comprise a machined feature that acts as a corner cube to enhance reflectivity. In another embodiment, a Littrow mode diffraction grading may be etched on the reflective surface to provide high reflectivity when the beam is perpendicular to the surface. In another embodiment, ceramic spheres could be added to a thermal barrier coating (TBC) similar to 3M ScotchBright and applied to the reflective surface. Such ceramic spheres act as a corner cube to enhance reflectivity and provide a return beam directly along the path of the transmitted beam. In one embodiment the corner cubes may be implemented as a micro- machined array in order to make the receive signal more tolerant of misalignment, beam steering, vibration and the like.

[0046] Various embodiments of the disclosure could also include permutations of the various elements recited in the claims as if each dependent claim was multiple dependent claim incorporating the limitations of each of the preceding dependent claims as well as the independent claims. Such permutations are expressly within the scope of this disclosure. In addition, various embodiments disclosed herein can be combined if technically feasible even if disclosed as separate embodiments and such combinations are within the scope of the disclosure and the invention.

[0047] While the invention has been particularly shown and described with reference to a number of embodiments, it would be understood by those skilled in the art that changes in the form and details may be made to the various embodiments disclosed

herein without departing from the spirit and scope of the invention and that the various embodiments disclosed herein are not intended to act as limitations on the scope of the claims. All references cited herein are incorporated in their entirety by reference.