Abstract:
An aircraft jet propulsion system is disclosed. The aircraft jet propulsion system may comprise a thermoelectric generator array (“TEG” array) coupled to a portion of the aircraft jet propulsion system, wherein the TEG array converts heat energy to electrical energy, and supplies power to the aircraft jet propulsion system, wherein the electrical energy is supplied to a power supply. The aircraft jet propulsion system may comprise an alternator that generates less energy than is required to power the aircraft jet propulsion system. The TEG array may supplement the energy generated by the alternator. The energy generated by the TEG array and the energy generated by the alternator may be sufficient to power the aircraft jet propulsion system and/or the electrical energy generated by the TEG array may be sufficient to power to aircraft jet propulsion system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of, claims priority to and the benefit of, PCT/US2014/053190 filed on Aug. 28, 2014 and entitled “SYSTEMS FOR GENERATING AUXILLARY ELECTRICAL POWER FOR JET AIRCRAFT PROPULSION SYSTEMS,” which claims priority from U.S. Provisional Application No. 61/878,494 filed on Sep. 16, 2013 and entitled “SYSTEMS FOR GENERATING AUXILLARY ELECTRICAL POWER FOR JET AIRCRAFT PROPULSION SYSTEMS.” Both of the aforementioned applications are incorporated herein by reference in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present disclosure relates to electrical power, and more particularly, to an auxiliary electrical power system for use with a jet aircraft propulsion system. 
       BACKGROUND OF THE INVENTION 
       [0003]    Jet aircraft propulsion systems (e.g., a gas turbine engine coupled to a nacelle) generate large amounts of heat energy. A variety of cooling systems are available to cool these systems. For example, propulsion systems may be cooled by air cooling systems, radiative cooling systems, and other like cooling systems. 
       SUMMARY OF THE INVENTION 
       [0004]    An aircraft jet propulsion system is disclosed. The aircraft jet propulsion system may comprise a thermoelectric generator array (“TEG array”) coupled to a portion of the aircraft jet propulsion system, wherein the TEG array converts heat energy to electrical energy. The aircraft jet propulsion system may also comprise a TEG array that converts heat energy to electrical energy and supplies the electrical energy to, a power supply. The power supply may supply power to the aircraft jet propulsion system. The aircraft jet propulsion system may comprise an alternator that generates less electrical energy than the amount of electrical energy associated with the electrical needs of the aircraft jet propulsion system. The TEG array may supplement the energy generated by the alternator. In various embodiments, the energy generated by the TEG array and the energy generated by the alternator may be sufficient to fulfill the electricity needs of the aircraft jet propulsion system and/or the electrical energy generated by the TEG array may be sufficient to fulfill the electricity needs of the aircraft jet propulsion system. 
         [0005]    In various embodiments, the TEG array may be coupled to an exhaust portion of the aircraft jet propulsion system, and the exhaust portion may comprise an exhaust nozzle. The TEG array may be coupled to any of: an outer surface of an inner fixed structure (“IFS”), an inner surface of a nacelle, between a heat blanket and an inner surface of a nacelle, to an outer surface of a heat blanket mounted to an inner surface of a nacelle, an air inlet, an air inlet outboard of an anti-ice system, and the like. 
         [0006]    The TEG array may comprise a plurality of TEGs electrically coupled in series and/or a plurality of sets of TEGs, each set electrically coupled in parallel. The TEG array may comprise six sets of TEGs, each set electrically coupled in parallel. The TEG array may comprise six TEGs coupled in series. The TEG array may, in various embodiments, generate from about 20 Volts to about 50 Volts and from about 1 W to about 500 W. 
         [0007]    A TEG array is disclosed. In various embodiments, the TEG array may comprise a first set of thermoelectric generators coupled in series and/or a second set of TEGs coupled in series, wherein the first set of TEGs and the second TEGs may be coupled in parallel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements. 
           [0009]      FIG. 1  illustrates, in accordance with various embodiments, a cross-sectional view of a turbofan engine. 
           [0010]      FIG. 2  illustrates, in accordance with various embodiments, a cross-sectional view of a TEG; 
           [0011]      FIG. 3  illustrates, in accordance with various embodiments, a circuit diagram of a TEG array; 
           [0012]      FIG. 4  illustrates, in accordance with various embodiments, a cross-sectional view of an exhaust portion of a jet aircraft propulsion system equipped with a TEG array; 
           [0013]      FIG. 5  illustrates, in accordance with various embodiments, a fan cowl anti-ice system of a jet aircraft propulsion system equipped with a TEG array; and 
           [0014]      FIG. 6  illustrates, in accordance with various embodiments, a cross-sectional view of an inner fixed structure of a jet aircraft propulsion system equipped with a TEG array. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the inventions, it should be understood that other embodiments may be realized and that logical, chemical and mechanical changes may be made without departing from the spirit and scope of the inventions. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
         [0016]    As used herein, “aft” refers to the direction associated with the tail (e.g., the back end) of an aircraft, or generally, to the direction of exhaust of the gas turbine. As used herein, “forward” refers to the direction associated with the nose (e.g., the front end) of an aircraft, or generally, to the direction of flight or motion. 
         [0017]    As described above, jet aircraft propulsion systems generate large amounts of heat energy. A variety of cooling systems are available to cool these propulsion systems. For example, propulsion systems may be cooled by air cooling systems, radiative cooling systems, and other like cooling systems. In operation, however, these cooling systems may bleed large amounts of heat energy away from the aircraft propulsion system, though the heat energy is largely dissipated as heat. Specifically, these systems may not recapture heat energy generated by the propulsion system during operation so that the heat energy may be harnessed for useful work. 
         [0018]    With reference to  FIG. 1 , an aircraft propulsion system  100  is shown and may generally comprise a nacelle  102  comprising an inner fixed structure (“IFS”)  104 . The aircraft propulsion system  100  may generally extend from forward to aft along the axis A-A′, with point A being forward of point A′ and point A′ being aft of point A In flight, air from point A may flow around and/or through aircraft propulsion system  100  in the direction from point A to point A′. The nacelle  102  may define an outer airflow surface of the aircraft propulsion system  100 . The nacelle  102  may include an air inlet  114  through which air may enter aircraft propulsion system  100 . An anti-ice system (not shown, and which may heat the air inlet to melt ice) may be disposed within the air inlet  114 . The IFS  104  may define an inner airflow surface of the aircraft propulsion system  100 . The IFS  104  may be disposed coaxially to engine core  106 . The engine core  106  may burn a hydrocarbon fuel in the presence of compressed air to generate exhaust gas  108 . The exhaust gas  108  may be expanded across a turbine  116  to drive turbofan  110  at the forward portion of the aircraft propulsion system  100 . The turbofan  110  may rotate to generate bypass fan airflow  112  between an interior surface of the nacelle  102  and an exterior surface of the IFS  104 . 
         [0019]    With reference to  FIG. 2 , a thermoelectric generator (“TEG”) may be coupled to one or more portions of aircraft propulsion system  100  to recapture heat energy generated by aircraft propulsion system  100 . Referring to  FIG. 2 , although TEGs may vary in the construction and/or composition, TEG  200  may generally comprise first substrate  202  and a second substrate  204 . The first substrate  202  may comprise any substrate capable of conducting heat, such as a metallic or ceramic wafer. The second substrate  204  may comprise any substrate capable of conducting heat, such as a metallic or ceramic wafer. The first substrate  202  may be in thermal contact with a heat source  206 . Thermal contact, as used herein, may mean that two objects may exchange heat. Heat may be exchanged by convection, conduction, and/or radiation. The second substrate  204  may be in contact with heat sink  208  and/or, in general, with any material or surface that is configured to dissipate heat. The heat source  206  may generate energy as heat, while the heat sink  208  may absorb and/or dissipate energy as heat. 
         [0020]    A plurality of thermoelectric semiconductors  210   a - 210   i  may be situated or laminated between the first substrate  202  and the second substrate  204 . Each thermoelectric semiconductor  210   a - 210   i  may comprise either of an n-type material (e.g.,  210   a,    210   c,    210   e,    210   g,  and  210   i ) or a p-type material (e.g.,  210   b,    210   d,    210   f,  and  210   f ). Each thermoelectric semiconductor  210   a - 210   i  may be electrically coupled through a respective electrical interconnect  216   a - 216   j.  Thus, each thermoelectric semiconductor  210   a - 210   i  may be thermally coupled in parallel and electrically coupled in series and together form TEG  200 . 
         [0021]    An n-type material may comprise a semiconductor doped with an electron donating material or impurity. A p-type material may comprise a semiconductor doped with an electron accepting material or impurity. An electron donating impurity may contribute free electrons to the semiconductor. These electrons may move within the semiconductor. An electron accepting impurity may contribute atoms capable of accepting electrons to the semiconductor. The absence of an electron in the valence band of an electron accepting impurity may be referred to as a “hole.” A hole may function as charge carrier that may move within the semiconductor. 
         [0022]    n-type and p-type materials may comprise a variety of semiconducting materials, and all are contemplated by this disclosure. However, in various embodiments, an n-type material may comprise an intrinsic semiconductor (such as Silicon, Germanium, Aluminum phosphide, Aluminum arsenide, Gallium arsenide, Gallium nitride, and the like) doped with any impurity that donates electrons (e.g., Phosphorous, Arsenic, Selenium, Tellurium, Silicon, Germanium, and the like). A p-type material may comprise an intrinsic semiconductor doped with any impurity that accepts electrons (e.g., Boron, Aluminum, Beryllium, Zinc, Cadmium, Silicon, Germanium, and the like). 
         [0023]    In operation, heat energy from the heat source  206  may be absorbed by the first substrate  202  and rejected, or dissipated, by the second substrate  204 . The temperature gradient between the heat source  206  and the heat sink  208  may drive electrons (in the n-type material) and/or holes (in the p-type material) through each material. Thus, an electric current may flow in the direction of heat flow, as depicted in  FIG. 2 . An external electrical connection comprising a positive contact  212  and a negative contact  214  may conduct electrical current generated by TEG  200  to an external circuit. In an embodiment, TEG  200  may utilize a thermoelectric effect (e.g., the Seebeck effect) to convert heat energy to electrical energy, however, it will be understood by those of ordinary skill in the art that any method of converting het energy into electric energy may be used. 
         [0024]    Thus, the TEG  200  (or a TEG array comprising a plurality of TEGs  200 , as described below) may be coupled or situated between any two surfaces between which a temperature gradient exists to generate electrical energy. For instance, TEG  200  may be situated between a first “hot” surface in a jet aircraft propulsion system and a second “cool” surface of the propulsion system, where the terms “hot” and “cool” are simply relative to one another during operation and between the two, define a temperature gradient. Thus, TEG  200  may recapture heat energy generated by a jet aircraft propulsion system 
         [0025]    Therefore, with reference to  FIG. 3 , a TEG array  302  is shown. The TEG array  302  may be electrically coupled to a power supply  304 , which may receive the output generated by TEG array  302  to supply power to engine mounted electronics  306  (as an example). In general, TEG  200  and/or TEG array  302  may be expected to generate any suitable voltage, current, and/or power. For example, in various embodiments, a TEG  200  may be expected to generate between two and five Volts and between one and four Amperes. Thus, although the electrical energy generated by a single TEG  200  may be useful for certain purposes, in other circumstances, greater electrical output may be generated by TEG array  302 . 
         [0026]    To this end, the TEG array  302  may comprise a plurality of sets of TEGs, e.g., sets  308 ,  310 , and  312 . Set  308  may comprise TEGs  308   a - 308   d.  Set  310  may comprise TEGs  310   a - 310   d.  Set  312  may comprise TEGs  312   a - 312   d.  Sets  308 ,  310 , and  312  may be electrically coupled in parallel with each other. Further, each of TEGs  308   a - 308   d  may be electrically connected in series with each other. Likewise, each of TEGs  310   a - 310   d  may be electrically connected in series with each other, and each of TEGs  312   a - 312   d  may be electrically connected in series with each other. 
         [0027]    In various embodiments, although three sets  308 ,  310 , and  312  of four TEGs  308   a - 308   d,    310   a - 310   d,  and  312   a - 312   d  each are shown, any number of TEGs may be coupled in series, and any number of sets of series coupled TEGs may be coupled in parallel to form a TEG array. In various embodiments, and as explained in additional detail below, six TEGs may be electrically coupled in series. In addition, in various embodiments, six sets of series coupled TEGs may additionally form a TEG array. 
         [0028]    Voltage adds in series coupled voltage sources. Therefore, in operation, TEG array  302  may generate an output voltage that is the sum of the voltages generated by a particular set of series coupled TEGs (e.g., any of sets  308 ,  310 , or  312 ). Thus, assuming an output voltage per TEG of approximately four to five Volts, a set of four TEGs coupled in series may be expected to produce between sixteen and twenty Volts. Similarly, a set of six TEGs coupled in series may be expected to produce between twenty-four and thirty Volts. In various embodiments, a TEG array  302  coupled in series may be expected to produce approximately twenty-eight Volts. However, a variety of other voltages may be achieved, depending upon the TEG selected, the number of TEGs, temperature differential, and the like. 
         [0029]    Current adds in parallel coupled voltage sources. Therefore, in operation, a TEG array  302  may generate an output current that is the sum of each of the sets  308 ,  310 , and  312  of TEGs. Assuming an output current of between one and four Amps, the TEG array  302  may be expected to produce between three and twelve Amps of current. However, a variety of other amperages may be achieved, depending upon the TEG selected, the number of TEGs, temperature differential, and the like. 
         [0030]    Approximately ten to fifty Volts (e.g., twenty-eight Volts), two to twenty amps, and fifty to five-hundred Watts may be typically required to power the electrical systems associated with an aircraft propulsion system  100 . Typically, an alternator (e.g., a permanent magnet alternator or “PMA”) is used to generate the electrical output needed to power the electrical systems associated with an aircraft propulsion system  100 . The PMA is situated within a gearbox within aircraft propulsion system  100 . Thus, the mechanical energy generated by aircraft propulsion system  100  is used to operate the PMA. This, in turn, leaches mechanical energy from aircraft propulsion system  100 . In addition, the PMA adds weight to the overall aircraft propulsion system  100  and adds a mechanical load to the total load on the gearbox. 
         [0031]    Thus, a TEG array (e.g., array  302 ) may be added to the aircraft propulsion system  100 , as needed and/or where possible to recapture heat energy generated by the aircraft propulsion system  100 . In various embodiments, a TEG array, such as the array  302  may be implemented to generate all or a portion of the electricity needed to operate the electrical systems associated with aircraft propulsion system  100 . Where a TEG array generates all the electricity needed, a PMA may be altogether excluded from the aircraft propulsion system  100 . Similarly, where a TEG array generates only a portion of the voltage and current needed to power aircraft propulsion system  100 , a PMA sized for a much lower (than typical) current draw may be implemented, thereby reducing the overall weight of the power generation system. 
         [0032]    Thus, TEG array  302  may be added to a propulsion system  100  to achieve a variety of advantages. Among these advantages, a TEG array  200  may save weight (in that the PMA may be removed from aircraft propulsion system  100  or reduced in size), reduce load, recapture what would otherwise constitute wasted heat generated by the system  100 , reduce a mechanical load on the gearbox, and add reliability to aircraft propulsion system  100 . With respect to the last advantage (reliability), TEGs  200 , which are solid state devices, do not include moving parts and are, in general, considered quite reliable. Thus, a TEG  200  may offer a reliability advantage of a moving or rotating power generating assembly, such as a PMA. 
         [0033]    Any suitable portion of aircraft propulsion system  100  may be equipped with a TEG array  302 . For example, any portion of aircraft propulsion system  100  in which a temperature gradient exists between a first portion of aircraft propulsion system  100  and a second portion of aircraft propulsion system  100  may be equipped with a TEG array  302 . Several example portions of aircraft propulsion system  100  which may be equipped with a TEG array  302  are shown in  FIGS. 4 ,  5 , and  6 . 
         [0034]    With reference to  FIG. 4 , an exhaust portion of aircraft propulsion system  100  may be equipped with a TEG array  302 . Specifically, a TEG array may be placed in contact with or coupled to the IFS  104  toward an aft (exhaust) portion of the IFS  104 , e.g., the exhaust nozzle  402 . The temperature gradient between the exhaust gas  108  and the bypass airflow  112  may be significant. Thus, placement of the TEG array  302  on the exhaust nozzle  402  separating these flows may result in significant energy production. 
         [0035]    With reference to  FIG. 5 , an air inlet  114  may be equipped with a TEG array  302 . As shown, the air inlet  114  (in cross-section) may be equipped with a TEG array. As described herein, an air inlet  114  may include an anti-ice system, which may heat the air inlet substantially to melt ice that develops around the air inlet  114 . The air entering the air inlet  114  is ambient air. Thus, a large temperature gradient may exist between the air inlet  114  and incoming air, making the air inlet (in particular the anti-ice portion of the air inlet  114 ) a suitable location for placement of a TEG array  302 . 
         [0036]    With reference to  FIG. 6 , an IFS  104  may be equipped with a TEG array  302 . As described herein, the IFS  104  may be disposed coaxially about an engine core, which may operate at extremely high temperatures. The nacelle  102  may surround the IFS  104 , and cooler bypass air may flow over the outer surface of the IFS  104 . Thus, a significant temperature gradient exists between the outer surface of the IFS  104  and the bypass airflow flowing around the IFS  104 . Accordingly, a TEG array  302  may generate significant electrical power in this area of the aircraft propulsion system  100 . 
         [0037]    Further, and more generally as described herein, a TEG array  302  may be suitably equipped on any portion of aircraft propulsion system  100  that experiences a temperature gradient. For instance, in addition to the examples discussed above, TEG arrays  302  may be placed on any hot bleed air ducts (e.g., the exhaust duct), on any engine coolers (e.g., on any air cooled or oil cooled surface of cooling system), between a heat blanket and an inner surface of the nacelle  102 , on an outer surface of a heat blanket mounted to an inner surface of the nacelle  102 , and the like. 
         [0038]    Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the inventions. The scope of the inventions is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
         [0039]    Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. 
         [0040]    Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.