Abstract:
The present invention provides in one embodiment of the present invention a surge margin power recuperation system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for recuperating power from surge margin bleed air. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application 61/290,619, filed Dec. 29, 2009, and is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to gas turbine engines, and more particularly, to surge margin bleed power recuperation. 
     BACKGROUND 
     Surge margin bleed systems remain an area of interest. Some existing systems have various shortcomings, drawbacks, and disadvantages relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present invention is a surge margin power recuperation system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for recuperating power from surge margin bleed air. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  schematically depicts a gas turbine engine having a surge margin bleed power recuperation system in accordance with an embodiment of the present invention. 
         FIG. 2  schematically illustrates a surge margin bleed power recuperation system in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the invention is intended by the illustration and description of certain embodiments of the invention. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present invention. Further, any other applications of the principles of the invention, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated as being within the scope of the present invention. 
     Referring now to the drawings, and in particular  FIG. 1 , a non-limiting example of a gas turbine engine  10  in accordance with an embodiment of the present invention is schematically depicted. Gas turbine engine  10  is an aircraft propulsion power plant in the form of an axial flow turbofan engine. Although the present embodiment is described with respect to an aircraft turbofan configuration, it will be understood that the present invention is equally applicable to other gas turbine engine configurations, for example, including turbojet engines, turboprop engines, and turboshaft engines having axial, centrifugal and/or axi-centrifugal compressors and/or turbines. In addition, the present invention is equally applicable to aero gas turbine engines, marine gas turbine engines and land-based gas turbine engines. 
     In the illustrated embodiment, gas turbine engine  10  includes a fan  12 , a compressor  14  with outlet guide vane (OGV)  16 , a surge margin bleed system  18 , an accessory drive system  20 , a power recuperation system  22 , a diffuser  24 , a combustor  26 , a high pressure (HP) turbine  28 , a low pressure (LP) turbine  30 , an exhaust nozzle  32  and a bypass duct  34 . Diffuser  24  and combustor  26  are fluidly disposed between OGV  16  of compressor  14  and HP turbine  28 . LP turbine  30  is drivingly coupled to fan  12  via an LP shaft  36 . HP turbine  28  is drivingly coupled to compressor  14  via an HP shaft  38 . Compressor  14 , HP shaft  38  and HP turbine  28  form, in part, an HP spool. Fan  12 , LP shaft  36  and LP turbine  30  form, in part, an LP spool. In one form, engine  10  is a two-spool engine. In other embodiments, engine  10  may have any number of spools, and may be, for example, a three-spool engine or a single spool engine. 
     Compressor  14  includes a plurality of blades and vanes  40  for compressing air. During the operation of gas turbine engine  10 , air is drawn into the inlet of fan  12  and pressurized by fan  12 . Some of the air pressurized by fan  12  is directed into compressor  14  and the balance is directed into bypass duct  34 . Bypass duct  34  directs the pressurized air to exhaust nozzle  32 , which provides a component of the thrust output by gas turbine engine  10 . Compressor  14  receives the pressurized air from fan  12 , which is compressed by blades and vanes  40 . 
     The pressurized air discharged from compressor  14  is then directed downstream by OGV  16  to diffuser  24 , which diffuses the airflow, reducing its velocity and increasing its static pressure. The diffused airflow is directed into combustor  26 . Fuel is mixed with the air in combustor  26 , which is then combusted in a combustion liner (not shown). The hot gases exiting combustor  26  are directed into HP turbine  28 , which extracts energy from the hot gases in the form of mechanical shaft power to drive compressor  14  via HP shaft  38 . The hot gases exiting HP turbine  28  are directed into LP turbine  30 , which extracts energy in the form of mechanical shaft power to drive fan  12  via LP shaft  36 . The hot gases exiting LP turbine  30  are directed into nozzle  32 , and provide a component of the thrust output by gas turbine engine  10 . 
     Surge margin bleed system  18  is in fluid communication with compressor  14 , and is operative to bleed interstage air from compressor  14  to control surge and increase surge margin at some gas turbine engine  10  operating points, e.g., during part power operation, such as in aircraft cruise conditions. In one form, surge margin bleed system  18  bleeds air from compressor  14  from one compressor stage. In other embodiments, gas turbine engine  10  bleeds air from compressor  14  at a plurality of compressor stages simultaneously. In yet other embodiments, surge margin bleed system  18  selectively bleeds air from one or more of a plurality of compressor stages. In one form, surge margin bleed system  18  includes one or more valves (not shown) configured to control surge margin bleed air flow. In various embodiments, the one or more valves may regulate the surge margin bleed flow to one or more desired flow rates, or may simply operate between a minimum flow position (which may yield a zero or non-zero flow area) and a maximum flow position, wherein the surge margin bleed air flow rate is governed by an effective flow area. In other embodiments, other means may be employed to control surge margin bleed flow. In still other embodiments, surge margin bleed flow may be continuous and not controlled by a valve system. 
     Power recuperation system  22  is in fluid communication with surge margin bleed system  18 . Power recuperation system  22  is operative to recapture energy from the air bled from compressor  14  for surge margin control that would otherwise be lost, e.g., by dumping the bleed air overboard. 
     Referring now to  FIG. 2 , gas turbine engine  10  includes an electrical rotor machine  42 , and a system electrical bus  44 . Electrical rotor machine  42  is mechanically coupled to accessory drive system  20  and electrically coupled to system electrical bus  44 . In one form, accessory drive system  20  is an accessory drive gearbox, although other drives system types may be employed in other embodiments. Accessory drive system  20  is operative to drive one or more accessories, such as accessories  46 ,  48  and  50 . The accessories may be engine accessories, such as one or more fuel pump, oil pump, generator, alternator, and/or may be aircraft and/or other accessories. In one form, system electrical bus  44  is the primary electrical bus for gas turbine engine  10 . In another form, system electrical bus  44  is an aircraft electrical bus. Electrical rotor machine  42  is configured to convert electrical power into mechanical power. In one form, electrical rotor machine  42  is a generator. In other embodiments, electrical rotor machine  42  may be an alternator or another type of electrical machine configured to convert electrical power into mechanical power. In yet other embodiments, electrical rotor machine  42  may also or alternatively be configured to convert mechanical power into electrical power, and may be, for example and without limitation, a motor/generator a motor/alternator, a generator or an alternator. 
     In one form, power recuperation system  22  includes an electrical rotor machine  52 , an auxiliary turbine, such as an air turbine  54 , and a controller  56 . Electrical rotor machine  52  is coupled to air turbine  54 . In one form, electrical rotor machine  52  is a high speed machine and is coupled to air turbine  54  in a direct drive arrangement. In other embodiments, electrical rotor machine  52  may be coupled to air turbine via one or more step-down and/or step-up gear drive systems or other types of mechanical power transmission systems. In one form, controller  56  is electrically coupled to system electrical bus  44 . In one form, electrical rotor machine  52  is electrically coupled to controller  56 . Power recuperation system  22 , in particular air turbine  54 , is in fluid communication with surge margin bleed system  18  and operative to receive bleed air from surge margin bleed system  18  that is used to preserve or enhance the surge margin of compressor  14 . Power recuperation system  22  is operative to convert power from the surge margin bleed air, that would otherwise be lost, into useful power that may be used by gas turbine engine  10 , and/or the aircraft or other system into which gas turbine engine  10  is installed. 
     Electrical rotor machine  52  is configured to convert mechanical power into electrical power. In one form, electrical rotor machine  52  is a generator. In another form, electrical rotor machine  52  is an alternator. In other embodiments, electrical rotor machine  52  may be another type of electrical machine configured to convert power into mechanical electrical power. In one form controller  56  is a dedicated power control logic unit. In another form, controller  56  is a part of another controller, such as a full authority digital electronic controller (FADEC) for operating gas turbine engine  10 , or another engine or aircraft controller. In one form, controller  56  is microprocessor based and the program instructions are in the form of software stored in a memory (not shown). However, it is alternatively contemplated that the controller and program instructions may be in the form of any combination of software, firmware and hardware, including state machines, and may reflect the output of discreet devices and/or integrated circuits, which may be co-located at a particular location or distributed across more than one location, including any digital and/or analog devices configured to achieve the same or similar results as a processor-based controller executing software or firmware based instructions. 
     Air turbine  54  receives the surge margin bleed air from surge margin bleed system  18 . Electrical rotor machine  52  is mechanically coupled to air turbine  54 , and produces electrical power from the air received by air turbine  54 . Absent the present invention, compressor surge margin control of a two-spool gas turbine engine is done via bleed air that is wasted, resulting in a loss of overall engine efficiency. Gas turbine engines typically use an engine rotor, such as the HP spool, for accessory power extraction for an accessory gear box, such as accessory drive system  20 . In addition to the lost bleed air, accessories also result in power lost in the overall gas turbine cycle. In one form, the present application uses the surge margin control bleed air flow to generate additional electrical power via driving an air turbine  54  directly coupled to a high-speed electrical rotor machine  52 . A power control logic unit, e.g., controller  56 , connected to or located on the system electrical bus  44 , takes advantage of the extra electrical power generated by the bleed air via electrical rotor machine  52 . This may lower the accessory gearbox mounted electrical rotor machine  42  power demand, and may result in additional surge margin capability to be utilized. 
     Typical gas turbine engines, such as two spool gas turbine engine applications, have a fixed set of operability limits. A given amount of surge margin is normally built into the engine as delivered to the customer. Continued need for additional power extraction demands from the end use customer often consumes the as-delivered baseline surge margin. If additional power extraction demands by the customer are agreed to, and not completely understood, the result may include negative surge margins in certain regions of the engine operability envelope. Power recuperation system  22  may, in one form, provide a potential means for gaining back additional surge margin. Assuming the additional weight of the power recuperation system  22  is outweighed by its own power production capacity, the system may in one form provide a means to answer increasing customer power extraction needs. Additionally, the system may offer additional solutions. Such as, but not limited to; allowing for varying the engine cycle to get more power out of certain operating regimes the customer desires, a means of offering the customer an off-the-shelf solution for augmenting capability of a given legacy engine(s), more flexibility in the preliminary design phase of a new engine program. These may also applicable to ground based and marine applications. Ground based and marine applications using a power recuperation system may give greater gains in system performance than flight systems—weight is normally not an issue—likely allowing for optimization, e.g., of the air turbine, generator, electrical bus, and power control logic unit. 
     Many embodiments of the present invention are envisioned. In one form, electrical rotor machine  42  is an accessory in the form of a generator, and electrical rotor machine  52  is a high speed generator directly driven by air turbine  54 . Bleed air pressure received into power recuperation system  22  is converted by air turbine  54  into shaft power, which is converted by electrical rotor machine  52  into electrical power. The electrical power is conditioned, and is supplied to system electrical bus  44  via controller  56 , thereby reducing the electrical load demand on electrical rotor machine  42  and mechanical load demand on accessory drive system  20 . 
     In another form, electrical rotor machine  42  is a motor (e.g., or a motor/generator) and electrical rotor machine  52  is a high speed generator directly driven by air turbine  54 . Bleed air pressure received into power recuperation system  22  is converted by air turbine  54  into shaft power, which is converted by electrical rotor machine  52  into electrical power. The electrical power is conditioned, and is supplied to electrical rotor machine  42  via controller  56 , which in turn supplies mechanical power to accessory drive system  20 . 
     In still another form, air turbine  54  may be mechanically coupled to accessory drive system  20  for delivering the shaft power to accessory drive system  20  without employing electrical rotor machine  52 , e.g., as indicated by dashed line  58  in  FIG. 2 , for example, to drive or help drive accessories  46 ,  48  and  50 . 
     Embodiments of the present invention include a gas turbine engine. The gas turbine engine includes a compressor; a combustor in fluid communication with the compressor; a turbine in fluid communication with the combustor; a surge margin bleed system in fluid communication with the compressor and operative to bleed air from the compressor to control surge margin; and a power recuperation system in fluid communication with the surge margin bleed system and operative to recapture power from the surge margin bleed air. 
     In one refinement, the power recuperation system includes an auxiliary turbine in fluid communication with the surge margin bleed system, wherein the auxiliary turbine is operative to receive bleed air from the surge margin bleed system and to extract the power from the surge margin bleed air. In another refinement, the gas turbine engine further includes an accessory drive system, wherein the auxiliary turbine is mechanically coupled to the auxiliary drive system and operative to transmit the power from the surge margin bleed air to the accessory drive system in the form of shaft power. 
     In yet another refinement, the power recuperation system further includes a first generator mechanically coupled to the auxiliary turbine. 
     In still another refinement, the gas turbine includes an accessory drive system operative to drive an accessory, wherein the power recuperation system further includes an electric motor mechanically coupled to the accessory drive system and electrically coupled to the first generator, and wherein the electric motor is operative to receive power from the first generator and to provide mechanical power to the accessory drive system based on the received power. 
     In yet still another refinement, the gas turbine engine includes a system electrical bus, wherein the first generator is electrically coupled to the system electrical bus and operative to provide power recaptured from the surge margin bleed air to the system electrical bus. 
     In a further refinement, the gas turbine engine further includes a controller communicatively coupled to the first generator and to the system electrical bus, and wherein the controller is configured to execute program instructions to control the power provided from the first generator to the system electrical bus. 
     In a yet further refinement, the gas turbine engine further includes an accessory drive system and a second generator powered by the accessory drive system and electrically coupled to the system electrical bus, wherein both the first generator and the second generator are operative to provide power to the system electrical bus. 
     In still a further refinement, the gas turbine engine further includes a controller coupled to the first generator, the second generator and to the system electrical bus, wherein the controller is configured to execute program instructions to control the power provided from the first generator and the second generator to the system electrical bus. 
     Embodiments of the present invention include a gas turbine engine, comprising: a compressor configured to discharge surge margin bleed air to control surge margin; a combustor in fluid communication with the compressor; a turbine in fluid communication with the combustor; an auxiliary turbine in fluid communication with the compressor and operative to recapture power from the surge margin bleed air; and an electrical rotor machine coupled to the auxiliary turbine and operative to convert mechanical power generated by the auxiliary turbine to electrical power. 
     In a refinement, an electrical bus is coupled to the electrical rotor machine and operative to receive the electrical power from the electrical rotor machine. 
     In another refinement, the electrical bus is an engine electrical bus. 
     In yet another refinement, the electrical bus is an aircraft electrical bus for an aircraft into which the gas turbine engine is installed. 
     In still another refinement, the electrical rotor machine is a first electrical rotor machine, further comprising a second electrical rotor machine electrically coupled to the first electrical rotor machine, wherein the second electrical rotor machine is operative to convert the electrical power from the first electrical rotor machine into mechanical power. 
     In yet still another refinement, the gas turbine engine further comprises an accessory drive system coupled to the second electrical rotor machine, wherein the second electrical rotor machine is operative to supply the mechanical power to the accessory drive system. 
     In a further refinement, the electrical rotor machine is a first electrical rotor machine, further comprising a second electrical rotor machine electrically coupled to the first electrical rotor machine, wherein the second electrical rotor machine is operative to convert the mechanical power received from the gas turbine engine into electrical power; and wherein the electrical power from the first electrical rotor machine is operative to reduce an electrical load on the second electrical rotor machine. 
     In a yet further refinement, the gas turbine engine further comprises an engine-driven accessory drive system coupled to the second electrical rotor machine, wherein the second electrical rotor machine is powered by the accessory drive system. 
     Embodiments include a gas turbine engine, comprising: a compressor configured to discharge surge margin bleed air to control surge margin; a combustor in fluid communication with the compressor; a turbine in fluid communication with the combustor; and means for recapturing power from the surge margin bleed air. 
     In a refinement, the means for recapturing includes an auxiliary turbine in fluid communication with the compressor and operative to recapture power from the surge margin bleed air. 
     In another refinement, the gas turbine engine further comprises an accessory drive system powered at least in part by the auxiliary turbine. 
     In yet another refinement, the gas turbine engine further comprises an electrical rotor machine coupled in a direct-drive arrangement to the auxiliary turbine and configured to convert the recaptured power to electrical power. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.