Patent Publication Number: US-11655038-B2

Title: Aircraft air supply and contaminant detection system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Division of U.S. application Ser. No. 16/028,999 filed Jul. 6, 2018, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This disclosure relates to aircraft and on-board air supply systems, and more particularly to an on-board air delivery system with contaminant detection 
     Aircraft equipped to fly at elevations above 10,000 feet can include an air supply system that supplies pressurized air to the aircraft cabin. Such systems generally draw a bleed of air from a compressor section of a gas turbine engine used for propulsion as a source of pressurized air, but can also utilize compressed air from other sources such as an electrically-powered compressor. The compressed air supply can be subject to further conditioning such as in an air cycle machine in which the compressed air can be cooled, subjected to one or more compression and expansion steps by turbine and compressor blades on a shared rotary power connection, and dried before delivery to a cabin air recirculation loop. As with any occupied enclosed conditioned air space, it is desirable to maintain an acceptable air quality, and air treatment processes such as ozone removal and various types of filtration or other air quality treatments have been used or proposed. However, testing for contaminants can be challenging in an aircraft environment where conditions can be adverse and performance specifications can be demanding. 
     BRIEF DESCRIPTION 
     A method of testing for tricresyl phosphate is disclosed. According to the method, light is directed from a light source to a light detector. A test gas is contacted with a metal organic framework on an exterior surface of an optical guide in communication with the light between the light source and the light detector, and a change is detected in light intensity or spectral properties of light received by the light detector caused by adsorption of tricresyl phosphate by the metal organic framework. 
     In any of the above embodiments, the optical guide can comprise a fiber optic element including a core comprising an optical material with a first refractive index, said metal organic framework on a first exterior surface portion of the core, and a cladding optically coupled to a second exterior surface portion of the core, said cladding comprising an optical material with a second refractive index lower than the first refractive index and configured to reflect light from the core at an interface between the core and the cladding. 
     In any one or combination of the foregoing embodiments, further comprising a filament, the first exterior surface portion can be disposed at a central portion along a length of the filament, and the cladding disposed on each side of the central portion along the length of the filament. 
     In any one or combination of the foregoing embodiments, the metal organic framework can include pore sizes greater than a molecular kinetic diameter of the tricresyl phosphate. 
     In any one or combination of the foregoing embodiments, the metal organic framework can include functional groups interactive with tricresyl phosphate. 
     In any one or combination of the foregoing embodiments, the metal organic framework can include pores larger than 1.5 nm. 
     In any one or combination of the foregoing embodiments, the metal organic framework can include polar functional groups. 
     In any one or combination of the foregoing embodiments, the system can further comprise a heat source in controllable thermal communication with the metal organic framework for regeneration. 
     In any one or combination of the foregoing embodiments, the system can further comprise a controller configured to detect a contaminant based on output from the light detector, and to generate a response thereto. 
     In any one or combination of the foregoing embodiments, the method can include, or the response generated by the controller can be selected from: providing a system alarm to the presence of the contaminant or activating an air contaminant removal protocol. 
     In any one or combination of the foregoing embodiments, the method can include, or the response generated by the controller can include regenerating the metal organic framework with heated air. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter of this disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG.  1 A  is a schematic illustration of an aircraft that can incorporate various embodiments of the present disclosure; 
         FIG.  1 B  is a schematic illustration of a bay section of the aircraft of  FIG.  1 A ; 
         FIG.  2    is a schematic depiction of an example embodiment of an aircraft air cycle environmental conditioning system; 
         FIG.  3    is a schematic depiction of a contaminant sensor. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS.  1 A- 1 B , an aircraft includes an aircraft body  101 , which can include one or more bays  103  beneath a center wing box. The bay  103  can contain and/or support one or more components of the aircraft  101 . For example, in some configurations, the aircraft can include environmental control systems and/or fuel inerting systems within the bay  103 . As shown in  FIG.  1 B , the bay  103  includes bay doors  105  that enable installation and access to one or more components (e.g., environmental control systems, fuel inerting systems, etc.). During operation of environmental control systems and/or fuel inerting systems of the aircraft, air that is external to the aircraft can flow into one or more ram air inlets  107 . The outside air may then be directed to various system components (e.g., environmental conditioning system (ECS) heat exchangers) within the aircraft. Some air may be exhausted through one or more ram air exhaust outlets  109 . 
     Also shown in  FIG.  1 A , the aircraft includes one or more engines  111 . The engines  111  are typically mounted on wings of the aircraft and are connected to fuel tanks (not shown) in the wings, but may be located at other locations depending on the specific aircraft configuration. In some aircraft configurations, air can be bled from the engines  111  and supplied to environmental control systems and/or fuel inerting systems, as will be appreciated by those of skill in the art. 
     An aircraft environmental control system, also referred to as an ECS or ECS pack, can include customary components for air cycle cooling systems, including heat exchangers, compressors (e.g., turbine-blade compressors), turbines, and heat exchanger/water removal units. Air cycle cooling systems can be based on three-wheel architecture (a fan, a compressor, and a turbine) or four-wheel architecture (a fan, a compressor, and two turbines). In some embodiments, the ECS pack cools bleed air in a ram air heat exchanger, partially re-compresses it in a turbine-powered compressor, cools the partially re-compressed air in a second pass through the ram air heat exchanger, expands and further cools the air flow and removes water with a turbine in a flow loop with a heat exchanger water removal unit, and, in the case of a four-wheel architecture further expands and cools the air in a second turbine. 
     An example embodiment of on-board air cycle cooling system  140  is schematically shown in  FIG.  2   . Air cycle cooling system depicts a so-called “four-wheel” system, referring to the four rotating devices (a ram air fan, one compressor, and two turbines), but “three-wheel” systems having only a single turbine are also contemplated. As shown in  FIG.  2   , compressed air  212  from a compressed air source (not shown) such as a pre-cooled turbine engine bleed, an APU bleed, or an electrically-powered compressor is delivered through control valve  214 . From there, the compressed air is directed to a heat exchanger  215  (also referred to in the art as a primary heat exchanger) where it rejects heat to ambient air flowing through or across a heat absorption side of heat exchanger  215 . Cooled compressed air is discharged from heat exchanger  215  to compressor  220 . A portion of the air going to heat exchanger  215  can be controllably diverted through conduit  217  and control/expansion valve  219  to mix with the outlet of turbine  244  and control the temperature of the conditioned air exiting the system. Compressor  220  compresses its portion of the air from the heat exchanger  215 , which also results in heating of the air. The further compressed air is discharged from compressor  220  through conduit  224  to heat exchanger  226  (also referred to in the art as a secondary heat exchanger) where it rejects heat to ambient air flowing through or across a heat absorption side of heat exchanger  226 . 
     The ambient air  213  flowing through or across the heat absorption sides of heat exchangers  215  and  226  can be a ram air flow from a forward-facing surface of the aircraft. In conditions under which insufficient airflow is generated by the forward motion of the aircraft for operation of the heat exchangers  215 ,  226 , the air flow can be assisted by operation of fan  228 . Check/bypass valve  229  allows for bypass of the fan  228  when ram air flow is sufficient for the needs of the heat exchangers  215  and  226 . Heat exchangers  215  and  226  can share a flow path for the ambient cooling air, and can be integrated into a single unit with heat exchanger  215  sometimes referred to as a primary heat exchanger and heat exchanger  226  sometimes referred to as a secondary heat exchanger. Cooled air discharged from heat exchanger  226  is delivered through conduit  232  to a heat rejection side of heat exchanger  230 . In the heat rejection side of heat exchanger  230 , the air is further cooled to a temperature at or below the dew point of the air and flows into water removal unit  235  where liquid water  236  condensed from the air is removed. The dehumidified air flows through a heat absorption side of heat exchanger  230  where it is re-heated before being delivered through conduit  238  to turbine  240 , where work is extracted as the air is expanded and cooled by turbine  240 . A portion of the air going to turbine  240  can be diverted by valve  241  if needed to allow the temperature of the air at the inlet to the heat absorption side of heat exchanger  230  to be above freezing. The cooled expanded air discharged from the turbine  240  is delivered through conduit  242  to a heat absorption side of heat exchanger  230  where it along with the dehumidified air discharged from water collection unit  235  provides cooling needed to condense water vapor from air on the heat rejection side of heat exchanger  230 . The air streams on the heat absorption side of the heat exchanger  230  are thus reheated. Heat exchanger  230  is also sometimes referred to as a condenser/reheater, and can be integrated with water removal unit  235  in a single unit. The reheated air from conduit  242  exiting from the heat absorption side of heat exchanger  230  flows through conduit  243  to turbine  244 , where it is expanded and cooled, and then discharged from the system  140  through conduit  245  to mix manifold  250  where it is mixed with recirculating air  252  from the cabin or other pressurized zones before being discharged to back to the aircraft cabin or other pressurized zones of the aircraft. The environment air conditioning system  140  also includes a power transfer path  247  such as a rotating shaft that transfers power to the compressor  220  and fan  228  from work extracted by turbines  240  and  244 . 
     As mentioned above, this disclosure includes a contaminant sensor disposed on an air flow path between a source of compressed air and pressurized zones of the aircraft such as the cabin, cockpit, cargo hold, and some equipment bays. Example locations of a contaminant sensor can include the ECS conduit  245 , the mix manifold  250 , or any portion of a looped flow path for recirculating cabin air  252 . 
     An example embodiment of a contaminant sensor assembly  300  is schematically shown in  FIG.  3   . As shown in  FIG.  3   , an optical guide in the form of a fiber optic element shown in a cross-sectional view with a fiber optic element core  302  and a fiber optic element cladding  304  around the core  302 . The core and cladding can be made of various types of glass or plastic with high transmissivity and appropriate refractive indices to guide light within the core axially along the length of the fiber. This is accomplished with a refractive index differential at the interface along which the core is optically coupled to the cladding such that light transmitting through the core that is incident on the interface totally reflected back into the core according to Snell&#39;s Law. This phenomenon is known as total internal reflection, and is the basis for fiber optic technology, camera and binocular prisms, automotive windshield rain sensors, and numerous other technologies. A portion of the fiber optic element has a layer comprising a metal organic framework (MOF) 306 instead of cladding on the surface of the core  302 . 
     Metal organic framework materials are well-known in the art, and comprise metal ions or clusters of metal ions coordinated to organic ligands to form one-, two- or three-dimensional structures. A metal-organic framework can be characterized as a coordination network with organic ligands containing voids. The coordination network can be characterized as a coordination compound extending, through repeating coordination entities, in one dimension, but with cross-links between two or more individual chains, loops, or spiro-links, or a coordination compound extending through repeating coordination entities in two or three dimensions. Coordination compounds can include coordination polymers with repeating coordination entities extending in one, two, or three dimensions. Examples of organic ligands include but are not limited to bidentate carboxylates (e.g., oxalic acid, succinic acid, phthalic acid isomers, etc.), tridentate carboxylates (e.g., citric acid, trimesic acid), azoles (e.g., 1,2,3-triazole), as well as other known organic ligands. Metal organic frameworks are further described by Batten, S R; Champness, N R; Chen, X-M; Garcia-Martinez, J; Kitagawa, S; Öhrstrom, L; O&#39;Keeffe, M; Suh, M P; Reedijk, J (2013). “Terminology of metal-organic frameworks and coordination polymers (IUPAC Recommendations 2013)”, Pure and Applied Chemistry. 85 (8): 1715. doi:10.1351/PAC-REC-12-11-2, the disclosure of which is incorporated herein by reference in its entirety. 
     A wide variety of metals can be included in a metal organic framework. In some embodiments, the metal organic framework comprises a transition metal, including but not limited to any of the transition metals described above with respect to transition metal oxide adsorbents. Examples of metals that can be included in the metal organic framework include Cu, Mg, Cr, Al, Mn, Co, Zr Zn. Lanthanide metals can include Ln, Eu, Ce, Er. Examples of specific metal organic framework materials include UIO-66 Zr-bdc, UiO-66-NH 2  ({Zr(bdc-NH 2 ) 2 } with (bdc-NH 2 )=2-amino-1,4-benzenedicarboxylate)), UIO-67 (Zr-bpdc) with bpdc=biphenyl-4,4′-dicarboxylic acid), MIL-101 ([Cr 3 (O)X(bdc) 3 (H 2 O) 2 ] (X=OH or F) with bdc=1,4-benzene dicarboxylate), NU-1000 ({Zr 6 (μ 3 -OH) 8 (—OH) 8 (TBAPy) 2  with TABAPy=1,3,6,8,-tetrakis(p-benzoic-acid)pyrene)), PCN-777 ({[Zr 6 (O) 4 (OH) 10 (H 2 O) 6 (TATB) 2  with TATB=4,4′,4″-s-triazine-2,4,6-triyl-tribenzoate), MOF-808 Zr 6 O 4 (OH) 4 (BTC) 2 (HCOO) 6  with BTC=1,3,5-benzenetricarboxylate), MOF-200 and MOF-210 [Zn 4 O(BBC) 2  and (Zn 4 O) 3 (BTE) 4 (BPDC) 3 , respectively; BBC=4,4′,4″-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate; BTE=4,4′,4″-(benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)) tribenzoate; BPDC=biphenyl-4,4′-dicarboxylate], MOF-177 [Zn4O(BTB)2; BTB=4,4′,4″-benzene1,3,5-triyl-tribenzoate], [MOF-399, Cu3(BBC)2] with BBC3-=4,4′,4″-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate. MOF&#39;s can be synthesized by hydrothermal or solvothermal techniques, where crystals are slowly grown from a hot solution. Templating for the MOF structure can be provided by a secondary building unit (SBU) and the organic ligands. Alternate synthesis techniques are also available, such as chemical vapor deposition, in which metal oxide precursor layers are deposited followed by exposure of the precursor layers to sublimed ligand molecules to impart a phase transformation to the MOF crystal lattice. 
     In some embodiments, the MOF 306 can be configured to promote absorption or adsorption of target contaminant(s). For example, tricresyl phosphate is commonly used as an anti-wear or anti-corrosion additive in hydraulic fluids used on aircraft. Tricresyl phosphate is toxic and has a low vapor pressure, which can make it a problematic contaminant for aircraft pressurized air, even at low concentrations. In some embodiments, the MOF 306 can be configured to deter absorption or adsorption of potential cross-contaminants (i.e., compounds that could produce a false positive) by the MOF 306. For example, the MOF can include functional groups appended to metal or organic portions of the framework that can attract or otherwise interact the contaminant(s). The MOF can also be configured with a porosity adapted for adsorption of the contaminant(s). In the case of testing for TCP, the pore size of the MOF 306 should be larger than at least 1.5 nm, as the TCP molecule kinetic diameter is larger than 1.5 nm. In some embodiments, the MOF can include pore sizes from 1.5 nm to 4 nm. Polar groups can be included in the MOF 306 to attract or otherwise interact with polar contaminants such as tricresyl phosphate. Examples of polar substituent groups that can be included in the MOF 306 can include hydroxyl, carbonyl, carboxyl, amino. In some embodiments, the MOF 306 can be immobilized in a polymer matrix in order to increase the sensitivity of the target analyte. In some embodiments, metal oxides (e.g., zinc oxide, iron oxide, titania, vanadium oxide) can be incorporated within the pore system of MOF 306 for enhanced selectivity of the target analyte. In some cases, metal nanoparticles (e.g., gold, platinum, palladium, copper, and nickel) can be impregnated in the pore system of MOF 306 to enhance the selectivity of the target analyte. 
     With reference again to  FIG.  3   , the portion of the fiber optic element with the metal organic framework 306 is disposed inside of a flow cell  308  equipped with an inlet  310  and an outlet  312 . The inlet  310  receives an air sample from an air source such as one of the locations mentioned above (e.g., ECS conduit  245 ,  FIG.  2   ), and can optionally be equipped with supplemental equipment such as a sampling pump or fan  314  or a heater  316 . The core  302  is optically connected on one end to a light source  318  (e.g., a laser at a wavelength, e.g., a near-infrared (NIR) laser, that is absorbed by the contaminant but not by other likely components of the gas sample). The light source  318  is connected to the core  302  through an optical connection  320 . The optional connection  320  can be any type of optical connection such as a fiber optic cable extension of the fiber optic element in the flow cell  308 , or a direct connection of the light source  318  to the fiber optic element in the flow cell  308 . The core  302  is optically connected on another end to a light detector  322  through an optical connection  324 , which can be the same or different type of optical connection as the optical connection  320 . An electronic processing unit  326  is shown connected to read the output of the light detector  322 , and can be operationally connected (e.g., through wired connections (not shown) or through wireless connections) to other system components such as the light source  318 , the sampling pump or fan  314  or the heater  316 , or to other on-board systems and operational structures. 
     During operation, sampled air is introduced to the flow cell  308  through the inlet  310 . In the presence of a contaminant  328  such as tricresyl phosphate, the contaminant  328  is adsorbed by the MOF 306 to concentrate the contaminant molecules at the interface with the fiber optic core  302 , where the contaminant molecules provoke a change of the evanescent field of traveling light in the fiber optic core  302 , which in turn impacts signal intensity as well as spectral changes in the light received by light detector  322 . Elution of bound contaminant molecules can be carried out by exposing the MOF 306 to a heat source such as directing air heated by heater  316  (e.g., 80° C.) into the flow cell  308 . In some embodiments, the electronic processing unit  326  can generate a response (or can engage with a master system controller to generate a response), including but not limited to providing a system alarm to the presence of the contaminant, reducing a flow rate of compressed outside air to the air cycle machine, or increasing a recirculation flow rate in the aircraft pressurized zone. 
     While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.