Patent Publication Number: US-2022228505-A1

Title: Integrated hybrid propulsion system

Description:
FIELD 
     The present disclosure relates generally to the field of hybrid propulsion systems. More specifically, the present disclosure relates to an integrated hybrid propulsion system having a combination heat engine and electrical generator. 
     BACKGROUND 
     Various hybrid propulsion systems may implement a separate heat engine and generator to convert mechanical power to electrical power. Implementation of such separate elements often results in overall increased weight of the hybrid propulsion system. 
     SUMMARY 
     The present disclosure sets forth exemplary embodiments which provide an improved hybrid propulsion system that implements a combined heat engine and electrical generator to efficiently extract electrical power without undue increase in overall system weight or volume. 
     One embodiment of the disclosure relates to a propulsion system that includes a gas generator, an electrical power generator disposed upstream of the gas generator and configured to be driven by a power turbine, an output power shaft mated to the power turbine and extending through a central axis of the gas generator and the power generator unit, an engine enclosure, and a shroud disposed between the power generator and the engine enclosure. The engine enclosure is configured to circumferentially surround the power generator. The shroud may comprise one or more non-magnetic materials. The power generator may include one or more rotating members configured to rotate about an axis defined by the output power shaft, wherein the one or more rotating members includes a compressor stage or a radial flux rotor, and wherein each of the one or more rotating members includes a magnetic portion. The power generator may further include a plurality of conductive members, wherein at least one of the plurality of conductive members is a stationary conductive member, and wherein the stationary conductive member includes a plurality of conductive coils such that rotation of the one or more rotating members relative to the stationary conductive member generates a current that is transmissible by one or more coupled power output cables. 
     In various embodiments, the one or more rotating members are boost compressor stages. In some embodiments, each of the one or more boost compressor stages is driven by the output power shaft, which is mated to the power turbine located at a downstream end of the gas generator. 
     In various embodiments, each of the one or more boost compressor stages comprises a plurality of blades, the magnetic portion is formed by at least a subset of the plurality of blades, and each of the subset of the plurality of blades is made of one or more magnetic alloys. 
     In various embodiments, each of the one or more boost compressor stages comprises a plurality of blades, the magnetic portion is formed by at least a subset of the plurality of blades, and each of the subset of the plurality of blades includes a permanent magnet embedded within a tip portion of each blade such that only the subset of the plurality of blades is magnetized. 
     In various embodiments, the stationary conductive member is integrally formed within the engine enclosure. In some embodiments, the one or more rotating members comprise axial flux rotors. In various embodiments, the power generator further comprises at least one axial flux stator disposed adjacent at least one of the one or more axial flux rotors, wherein the at least one axial flux stator is coupled to the engine enclosure. In some embodiments, the stationary conductive member includes one or more coupled conductive coils. 
     In another embodiment of the present disclosure, a propulsion system includes a gas generator, an electrical power generator disposed upstream of the gas generator and configured to be driven by a power turbine, an output power shaft mated to the power turbine and extending through a central axis of the gas generator and the boost compressor, and an engine enclosure. The engine enclosure is configured to circumferentially surround at least the power generator, and includes a conductive portion comprising a plurality of coils. The power generator includes one or more compressor stages configured to rotate about an axis defined by the output power shaft, wherein each of the compressor stages includes a plurality of blades, a magnetic portion, and a non-magnetic portion, and wherein rotation of the one or more compressor stages relative to the engine enclosure generates a current transmissible by one or more power output cables coupled to the engine enclosure. 
     In various embodiments, the magnetic portion is formed by at least a subset of the plurality of blades, and wherein each of the subset of the plurality of blades is made of one or more magnetic alloys. In other embodiments, the magnetic portion is formed by at least a subset of the plurality of blades, and wherein each of the subset of the plurality of blades includes a permanent magnet embedded within a tip portion of each blade. 
     In various embodiments, the conductive portion is mounted to an inner surface of the engine enclosure. In some embodiments, the engine enclosure comprises a non-magnetic section, wherein the non-magnetic section surrounds the power generator. In various embodiments, the non-magnetic section of the engine enclosure is a composite. 
     In yet another embodiment of the present disclosure, a propulsion system includes a gas generator, an electrical power generator disposed upstream of the gas generator and configured to be driven by a power turbine, an output power shaft mated to the power turbine and extending through a central axis of the gas generator and the power generator, and an engine enclosure. The engine enclosure is configured to circumferentially surround the power generator. The power generator includes one or more axial flux rotors mated to the output power shaft and configured to rotate with the output power shaft about an axis defined by the output power shaft, wherein each of the axial flux rotors includes a magnetic portion and a non-magnetic portion, wherein the magnetic portion of each of the axial flux rotors generates a current within a stationary conductor portion when each of the axial flux rotors rotates about the axis relative to the engine enclosure, wherein a speed of rotation of the one or more axial flux rotors is regulated by a load requirement, and wherein a load requirement voltage varies within a predetermined range. 
     In various embodiments, the stationary conductor portion comprises at least one axial flux stator disposed adjacent at least one of the one or more axial flux rotors, wherein the at least one axial flux stator is coupled to the engine enclosure. In some embodiments, the engine enclosure transmits the current generated within the stationary conductor portion via one or more coupled output cables. 
     In various embodiments, the system further includes a variable load coupled to the power generator, wherein the variable load is configured to fulfill a minimum load requirement. In some embodiments, the magnetic portion comprises a plurality of circumferentially arranged permanent magnets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A clear conception of the advantages and features constituting the present disclosure, and of the construction and operation of typical mechanisms provided with the present disclosure, will become more readily apparent by referring to the exemplary, and non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which: 
         FIG. 1  is schematic representation of a side cross-sectional view of a propulsion system. 
         FIG. 2  is a schematic representation of a side cross-sectional view of a boosted propulsion system. 
         FIG. 3  is a schematic representation of a side cross-sectional view of an integrated hybrid propulsion system, according to an exemplary embodiment. 
         FIG. 4  is a schematic representation of an end cross-sectional view of the integrated hybrid propulsion system of  FIG. 3 . 
         FIG. 5  is a perspective view of an integrated hybrid propulsion system, according to an exemplary embodiment. 
         FIG. 6  is a schematic representation of a side cross-sectional view of an integrated hybrid propulsion system driving an axial flux rotor, according to another exemplary embodiment. 
         FIG. 7  is a schematic representation of a perspective view of the integrated hybrid propulsion system of  FIG. 6  as may be provided with an axial flux electrical power generator. 
     
    
    
     The foregoing and other features of the present disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure. 
     Referring to  FIG. 1 , a schematic representation of a side cross-sectional view of a propulsion system  10  is shown. The propulsion system  10  is a turboshaft engine configured to produce shaft power and includes a gas generator or gas generator section  15  and a power turbine  20 . As illustrated, the gas generator section  15  includes a compressor section  25 , a combustion section  30 , and a high-pressure turbine  35 . An output power shaft  40 , which is driven by the power turbine  20 , is disposed concentrically within a high-pressure turbine shaft  45  that couples the compressor section  25  and the high-pressure turbine  35 . The output power shaft  40  and the high-pressure turbine shaft  45  pass through the combustion section  30 , which is disposed between the compressor section  25  and the high-pressure turbine  35 . The gas generator section  15  and its components, along with the power turbine  20 , is contained within an enclosure  50 . 
     The compressor section  25  includes a multi-stage compressor  53  (e.g., a compressor having N stages), which is configured to compress air flowing into the propulsion system  10  in an airflow direction  55 . The multi-stage compressor  53  may include high-pressure axial and/or centrifugal stages. Air compressed within the compressor  53  flows through the combustion section  30  where the air is mixed with fuel (e.g., injected atomized fuel, gaseous fuel, natural gas, etc.) and ignited. The ignited mixture then flows into and through the high-pressure turbine  35  and the power turbine  20  to cause rotation thereof. The high-pressure turbine  35  may be a multi-stage (e.g., a high-pressure turbine having N-stage) axial-flow type or radial type turbine. 
     Rotation of the high-pressure turbine  35  and the power turbine  20  generate shaft power to then drive the high-pressure turbine shaft  45  and the output power shaft  40 . The power turbine  20 , which is also a multi-stage axial flow type turbine, may be mechanically separated from the compressor section  25 . For example, the power turbine  20  extracts energy (i.e., work) from cycling within the gas generator section  15  (e.g., from the combusted air/fuel mixture) but may not otherwise affect operation or performance of the components within the gas generator section  15 , including the compressor section  25 . The compressor section  25  is driven by the high-pressure turbine shaft  45 . As previously described, the power turbine  20  drives the output power shaft  40 , which is concentrically disposed within the high-pressure turbine shaft  45  and extracts energy (i.e., work) therein. 
       FIG. 2  shows propulsion system  10  further including a low-pressure compressor (“boost”) section  60  having a plurality of low-pressure compressor stages  65  therein. As illustrated, the boost section  60  is disposed upstream of the gas generator section  15  and is configured to increase power of the propulsion system  10 . The low-pressure compressor or boost stages  65  may be axial-flow compressor stages (e.g., similar to compressor stages  53 ). The boost stages  65  are driven by the output power shaft  40 , which is mated to and driven by the power turbine  20 . 
     During operation of propulsion system  10 , with or without boost stages  65 , a separate electrical power generator may be coupled downstream of the power turbine  20 . The electrical power generator may be configured to generate electricity to power traction motors and/or auxiliary components within and/or coupled to the propulsion system  10 . With such an arrangement, the propulsion system  10  has added weight and volume due to the requirement for multiple, separate power generation components. As a propulsion system such as propulsion system  10  is typically used in aviation applications, it would be advantageous to reduce both weight and volume without reducing power or engine efficiency. 
       FIG. 3  shows a schematic representation of a side cross-sectional view of an integrated hybrid propulsion system  100 , according to an exemplary embodiment. Integrated hybrid propulsion system  100  enables reduction of both weight and volume in comparison to typical propulsion systems (e.g., propulsion system  10 ) by implementing integrated electrical and gas power generation components. As shown in  FIG. 3 , the propulsion system  100  includes a gas generator section  115  and a power turbine  120 . In various embodiments, the power turbine  120  may be disposed at a downstream end of the gas generator section  115 . As illustrated, the gas generator section  115  includes a compressor section  125 , a combustion section  130 , and a high-pressure turbine  135 . In various embodiments, the compressor section  125  may have a compression ratio ranging from about 4:1 to about 25:1. The aforementioned sections  115 ,  125 ,  130  and  135  may also be referred to as a gas generator stage, a compressor stage, a combustion stage and a turbine stage, respectively. An output power shaft  140 , which is driven by the power turbine  120 , extends through a central axis of the gas generator section  115 . The output power shaft  140  is further disposed concentrically within a high-pressure turbine shaft  145  that couples the compressor section  125  and the high-pressure turbine  135 . The output power shaft  140  and the high-pressure turbine shaft  145  pass through the combustion section  130 , which is disposed between the compressor section  125  and the high-pressure turbine  135 . The gas generator section  115  and its components, along with the power turbine  120 , is contained within an engine enclosure  150 . 
     The compressor section  125  includes a multi-stage compressor  153  (e.g., N-stage compressor), which is configured to compress air flowing into the propulsion system  100  in an airflow direction  155 . The multi-stage compressor  153  may include high-pressure axial and/or centrifugal stages. Air compressed within the compressor  153  flows through the combustion section  130  wherein the air is mixed with fuel (e.g., injected atomized fuel, gaseous fuel, natural gas, etc.) and ignited. The ignited mixture then flows into and through the high-pressure turbine  135  and the power turbine  120  to cause rotation thereof. The high-pressure turbine  135  is a multi-stage (e.g., N-stage) axial-flow type turbine. 
     Rotation of the high-pressure turbine  135  and the power turbine  120  generate shaft power to drive the high-pressure turbine shaft  145  and the output power shaft  140 . The power turbine  120 , which is also a multi-stage axial flow type turbine, is mechanically separated from the compressor section  125  in that the power turbine  120  extracts energy (i.e., work) from cycling within the gas generator section  115  (i.e., from the combusted air/fuel mixture) but does not otherwise affect operation or performance of the components within the gas generator section  115 , including the compressor section  125 . 
     The compressor section  125  is driven by the high-pressure turbine shaft  145 . As previously described, the power turbine  120  drives the output power shaft  140 , which is concentrically disposed within the high-pressure turbine shaft  145  and extracts energy (i.e., work) therein. 
     As illustrated in  FIG. 3 , integrated hybrid propulsion system  100  further includes an electrical power generator section  160  disposed upstream of the gas generator section  115 . The electrical power generator section  160  may be a hybrid low-pressure compressor (“boost”) section having a plurality of low-pressure compressor (“boost”) stages  165  therein. The low-pressure compressor stages  165  are configured to facilitate generation of electrical power. The low-pressure compressor or boost stages  165  are axial-flow compressor stages (e.g., similar to compressor stages  153 ). The boost stages  165  are driven by the output power shaft  140 , which is mated to and driven by the power turbine  120 . In various embodiments, the enclosure  150  is configured to circumferentially surround the electrical power generator section  160  in addition to the gas generator section  115 . 
     Each of the axial-flow boost stages  165  includes a plurality of blades  170 . Each of the blades  170  may include a non-magnetic portion  175  and a magnetic portion  180 . In various embodiments, only a subset of the plurality of blades  170  includes a magnetic portion  180 . As shown in  FIG. 3 , the magnetic portion  180  may be disposed at a distal or tip end of each of the blades  170 . In various embodiments, the magnetic portion  180  may be disposed within a middle or proximal portion of the blades  170  with respect to the output power shaft  140 . In other embodiments, the magnetic portion  180  may be distributed along a length and/or across a surface of the blades  170 . 
     Conducting elements  185 , such as conductor coils, may be mounted within the enclosure  150 . In various embodiments, the conducting elements  185  may be integrally formed within the enclosure  150 . In various embodiments, the conducting elements  185  may be removably coupled to an interior surface of the enclosure  150 . Accordingly, during operation of the integrated hybrid propulsion system  100 , the axial-flow boost stages  165  are driven by the output power shaft  140  such that the boost stages  165  may rotate about an axis defined by the output power shaft  140 . During rotation of the boost stages  165 , the magnetic portions  180  of at least a subset of the plurality of blades  170  form a rotating magnetic field, which may induce a current within the conducting elements  185 . The induced current may then be extracted by one or more power output cables operably coupled to the conducting elements. 
     In various embodiments, the propulsion system  100  may include a Generator Integrated Control Unit (GICU), which may be integrated with an Engine Control Unit (ECU) and operably coupled to the power generator section  160 , compressor section  125 , power turbine  120 , and/or the output power shaft  140 . Accordingly, the GICU and/or ECU may be configured to control a rate of power generation within the power generator section  160  and/or adjust a speed of the power turbine  120  to correspondingly adjust a speed of the output power shaft  140  and/or the boost stages  165 . In various embodiments, the GICU may be configured to adjust the speed of the power turbine  120  based on a threshold power output of the power generator section  160 . Accordingly, the GICU may increase the speed of the power turbine  120  to increase the speed of the output shaft  140  and the boost stage  165  to cause an increase in power generation by the power generator section  160  to meet the threshold. Conversely, the GICU may decrease the speed of the power turbine  120  to cause a decrease in power generation by the power generator section  160  to meet the threshold. In various embodiments, the GICU may be configured to increase the power generated by the power generator section  160  to meet or anticipate a power demand. In various embodiments, the GICU and/or ECU may be controllers (e.g., microcontrollers each having microprocessors). 
     In various embodiments, the GICU and the ECU may collaboratively control the rate of power generation within the power generator section  160 . For example, in an embodiment where the propulsion system  100  is controlled based on a speed of the power turbine  120  (e.g., by either the GICU and/or the ECU), the ECU may increase a fuel flow with increasing electrical load to cause a corresponding increase in speed of the gas generator  115 . This speed increase provides increased flow and temperature energy to the power turbine  120 , which enables maintaining a constant, predetermined speed of the power turbine  120  to produce increased electrical power. The predetermined speed may be based on one or more design or use application requirements of the propulsion system  100 . In various embodiments, the produced electrical power could be used to drive one or more electric motors (e.g., to drive one or more pumps, actuators, etc.), an environmental control system, and/or a primary drive system for an aircraft (e.g., main rotor, tail rotor, etc.). 
     The GICU and/or ECU may each be implemented as a non-transitory computer readable medium, having computer-readable instructions stored thereon that, when executed, cause the processor to carry out the operations called for by the instructions. 
     In various embodiments, operation of the power turbine  120 , and thus a rotation speed (e.g., rpm) of the output shaft  140 , may be regulated to electrical power demand on an output from the power output cables. In various embodiments, in a boosted configuration, (e.g., including power generator section  160 ) there may be a reduction in a surge margin of the compressor section  125  as compared to a typical system (e.g., propulsion system  10 ), whereas the surge margin of the boost section (e.g., power generator section  160 ) may be unaffected. In other embodiments, power generation by the power generator section  160  may not affect a surge margin associated with one or more sections, such as the surge margin of the high-pressure compressor section  125 . In various embodiments wherein electrical power is extracted from the compressor section  125 , a compressor operating line may be artificially increased in response to electrical power demand, which would decrease the surge margin. Accordingly, since the propulsion system  100  is configured to also generate electrical power from the boost section (e.g., power generator section  160 ), the surge margin of the compressor section may be less impacted (i.e., by electrical power generation). 
     In various embodiments, the enclosure  150  may comprise one or more non-magnetic materials, which may include, but is not limited to, non-metallic and/or composite materials. In various embodiments, the magnetic portions  180  may include a magnetic alloy and/or a permanent magnet (e.g., samarium cobalt, neodymium iron boron, alnico, ferrite, etc.) mounted to or integrally formed within each corresponding blade  170 . In some embodiments, the blades  170  may not include a non-magnetic portion  175  and only have a magnetic portion  180 . In these embodiments, the blades  170  may be constructed of one or more magnetic and/or metallic alloys (e.g., titanium alloys, AM 355 stainless steel, etc.). In various embodiments, the blades  170  may be dual alloy blades. In various embodiments, a first subset of the blades  170  may include a magnetic alloy and/or a permanent magnet mounted to or integrally formed therein, and a second subset of the blade  170  may include or be formed of non-magnetic materials. In various embodiments, each of the blades  170  may be magnetized and include a magnetic portion  180  (e.g., including or being formed of one or more magnetic materials, including or having mounted thereto a permanent magnet). 
       FIG. 4  shows a schematic representation of an end cross-sectional view of the integrated hybrid propulsion system  100 , according to an exemplary embodiment. As shown, blades  170  of each of the boost stages  165  may be driven by the output power shaft  140  to rotate thereabout. Accordingly, blades  170  having a magnetic portion  180  generate a rotating magnetic field, which may induce current within the conducting elements  185 . Although  FIG. 4  shows each of the blades  170  having a non-magnetic portion  175  and a corresponding magnetic portion  180 , as described above, only a subset of the blades  170  or all of the blades  170  may include a magnetic portion  180  in accordance with various embodiments. 
     Although  FIG. 4  shows a same number of conducting elements  185  as a number of blades  170 , various embodiments of the integrated hybrid propulsion system  100  may include an unequal number of conducting elements and/or blades  170 . Furthermore, although  FIG. 4  shows boost stages  165  as having six blades  170 , various embodiments of the propulsion system  100  may include any number of blades  170 . Accordingly, various embodiments of the propulsion system  100  may include any number of conducting elements  185 . 
     As illustrated in  FIG. 4 , the integrated hybrid propulsion system  100  further includes a shroud  190 . The shroud  190  may be disposed between the electrical power generator section  160  and the enclosure  150 . The shroud  190  is configured to reduce a clearance between tips of the blades of the boost stages  165  as excess tip clearance may cause poor compressive performance (e.g., within the power generator section  160  and/or the compressor section  125 ). In various embodiments, the shroud may be disposed between the conducting elements  185  and the blades  170  of the boost stages  165 . In various embodiments, the shroud  190  may include or be formed of one or more non-magnetic materials including, but not limited to, non-metallic and/or composite materials or non-magnetic metallic materials (e.g., graphite epoxy composite or a nickel chromium material such as Iconel® alloy 718 made by Special Metals Corporation (Precision Castparts Corp., Portland, Oreg.), etc.). The propulsion system  100  may also include one or more bearings  195 , which may be concentrically disposed adjacent the output power shaft  140  and/or the high-pressure turbine shaft  145  to facilitate ease of rotation. In various embodiments, the one or more bearings  195  may be configured to preserve shaft (e.g., shafts  140  and/or  145 ) alignment while allowing rotation of other system  100  components (e.g., rotors). In various embodiments, the one or more bearings  195  may include pressure lubricated roller and/or ball bearings, sleeve bearings, air bearings, magnetic bearings, or a combination thereof. 
       FIG. 5  shows a perspective view of integrated hybrid propulsion system  100  near power output cables  196 , according to an exemplary embodiment. As shown, the propulsion system  100  includes a plurality of blades  170  contained within an enclosure  150 . A shroud  190  may be disposed between the blades  170  and the enclosure  150 . As described, at least a subset of the plurality of blades  170  may include a magnetic portion such that when the blades  170  rotate within the enclosure, a rotating magnetic field is generated that subsequently induces a current within conducting elements  185 , which are disposed between the shroud  190  and the enclosure  150 . Induced current within the conducting elements  185  may be output from the propulsion system  100  via output cables  196 , which may be coupled to the conducting elements  185  via a connection  198 . 
       FIGS. 6 and 7  show a schematic representation of side cross-sectional and perspective views of an integrated hybrid propulsion system  200 , according to an exemplary embodiment. In various embodiments, elements  215  through  255  are of the propulsion system  200  are the same or equivalent to corresponding operations of the propulsion system  100 . Accordingly, as illustrated in  FIG. 6 , integrated hybrid propulsion system  200  further includes an electrical power generator section  260  disposed upstream of the gas generator section  215 . The electrical power generator section  260  may include a plurality of axial flux components  265 , wherein the axial flux components  265  are configured to facilitate generation of electrical power. 
     The axial flux components  265  include at least one axial flux rotor  270  and at least one axial flux stator  275 , wherein the at least one axial flux rotor  270  is driven by the output power shaft  240 , which is mated to and driven by the power turbine  220 . The at least one axial flux rotor  270  is configured to induce a magnetic field, and thus a current, within the axial flux stator  275  and coupled electrical components (e.g., coils). Accordingly, rotation of the at least one axial flux rotor  270  relative to the at least one axial stator  275 , which remains stationary within the electrical power generator section  260 , results in electrical power generation that may be transferred by an electrical connection  285  to one or more power output cables  280 , which may be mounted to and/or embedded within the enclosure  250 . In some embodiments, a portion of enclosure  250  disposed around at least one axial flux rotor  270  and at least one axial flux stator  275  is made of composite material. For example, only composite material may be provided where the at least one axial flux rotor  270  or the at least one axial flux stator  275  is provided, and other portions of enclosure  250  may be non-composite material. In various embodiments, the at least one axial flux stator  275  may be coupled to the enclosure  250 . 
     As illustrated in  FIG. 7 , each of the at least one axial flux rotors  270  includes a non-magnetic portion  300  and a magnetic portion  305 . As shown in  FIG. 7 , the non-magnetic portion  300  and magnetic portion  305  may be disposed on opposite sides of each axial flux rotor  270 . In various embodiments, the magnetic portion  305  may be disposed at a distal end or edge of each of the axial flux rotors  270 . In various embodiments, the magnetic portion  305  may be disposed within a middle or proximal portion of the axial flux rotors  270  with respect to the output power shaft  240 . In yet other embodiments, the magnetic portion  305  may be distributed along a length and/or across a surface of axial flux rotors  270 . In various embodiments, the magnetic portion may include a plurality of permanent magnets, which may be circumferentially arranged on a surface of at least one axial flux rotor  270 . As illustrated, the at least one axial flux stator  275  may include a plurality of conducting elements  310 , such as conductor coils, which may be mounted to, wound about, embedded, and/or integrally formed within the at least one axial flux stator  277 . As shown, the at least one axial flux stator  275  may be coupled to one or more output cables  280  via at least one electrical connection  285 . In various embodiments, the one or more output cables may be mounted to the enclosure  250  (e.g., disposed within an inner surface thereof). 
     Accordingly, during operation of the integrated hybrid propulsion system  200 , the axial flux rotors  270  are driven by the output power shaft  240  such that the axial flux rotors  270  may rotate about an axis defined by the output power shaft  240  relative to the at least one axial flux stator  275  (which remains stationary). During rotation of the axial flux rotors  270 , the magnetic portions  305  of the axial flux rotors  270  form a rotating magnetic field, which may induce a current within the conducting elements  310  of the at least one axial flux stator  275 . The induced current may then be accessed and extracted by one or more power output cables  280  via at least one electrical connection  285 . In various embodiments, the propulsion system  200  may further include a coupled variable load (e.g., battery, power storage device) to facilitate voltage and current management therein. In various embodiments, the variable load may be configured to fulfill a minimum load requirement. In various embodiments, the variable load may be caused by one or more electric motors (e.g., to drive one or more pumps, actuators, etc.), an environmental control system, and/or a primary drive system for an aircraft (e.g., main rotor, tail rotor, etc.). 
     In various embodiments, the propulsion system  200  may include a GICU, which may be integrated with an ECU, wherein the GICU and/or ECU of the propulsion system  200  may carry out all or some operations within the propulsion system  200  in a manner equivalent to corresponding operations within the propulsion system  100 . 
     In various embodiments, one or more surge protectors (e.g., an overload surge protector) may be provided. Further, a surge margin may be provided for protection during power extraction. In various embodiments, power generation by power generator section  260  results in a reduction in surge margin of the propulsion system  200  as compared to a typical system (e.g., propulsion system  10 ). In other embodiments, power generation by the power generator section  260  may not affect the surge margin, such as the surge margin of the high-pressure compressor section  225 . In various embodiments, a speed of rotation of the axial flux rotors  270  is regulated based on an output power of the electrical power generator section  260 . In various embodiments wherein electrical power is extracted from the compressor section  225 , a compressor operating line may be artificially increased in response to electrical power demand, which would decrease the surge margin. Accordingly, since the propulsion system  200  is configured to also generate electrical power from the boost section (e.g., power generator section  260 ), the surge margin of the compressor section may be less impacted (i.e., by electrical power generation). 
     In any of the implementations and/or embodiments of integrated hybrid propulsion system  100  and  200 , integration of an electrical power generator (e.g., electrical power generator section  160  or  260 ) with a gas generator (e.g., gas generator section  115  or  215 ) reduces weight and volume compared to typical propulsion systems (e.g., propulsion system  10 ), which requires separate components. Furthermore, integrating the electrical power generator (e.g.,  160  or  260 ) at an upstream position relative to the electrical power generator (e.g.,  115  or  215 ) results in a cooler air temperature (e.g., in an airflow direction  155  or  255 ) within the electrical power generator (e.g.,  160  or  260 ), which reduces resistance and improves current induction from rotation of magnetic and non-magnetic components, and thus increases electrical power generation, therein. Accordingly, in any of the implementations and/or embodiments of integrated hybrid propulsion system  100  and  200 , the enclosure (e.g.,  150  or  250 ) may be contoured to facilitate improved airflow within the electrical power generator section (e.g.,  160  or  260 ) to cool conducting elements (e.g.,  185 ,  310 ). In various embodiments, the enclosure (e.g.,  150  or  250 ) may be configured to have a contour corresponding to a geometry of the electrical power generator section (e.g.,  160  or  260 ). Additionally or alternatively, the enclosure (e.g.,  150  or  250 ) may include one or more inlets and/or outlets to facilitate active and/or passive ventilation and cooling of the conducting elements (e.g.,  185 ,  310 ). 
     Notwithstanding the embodiments described above in reference to  FIGS. 1-7 , various modifications and inclusions to those embodiments are contemplated and considered within the scope of the present disclosure. 
     It is also to be understood that the construction and arrangement of the elements of the systems and methods as shown in the representative embodiments are illustrative only. Although only a few embodiments of the present disclosure have been described in detail, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter disclosed. 
     Accordingly, all such modifications are intended to be included within the scope of the present disclosure. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the preferred and other illustrative embodiments without departing from scope of the present disclosure or from the scope of the appended claims. 
     The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. 
     With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. It will be understood by those within the art that, in general, terms used herein, and especially in appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. 
     In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Similarly, unless otherwise specified, the phrase “based on” should not be construed in a limiting manner and thus should be understood as “based at least in part on.” Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” Further, unless otherwise noted, the use of the words “approximate,” “about,” “around,” “substantially,” etc., mean plus or minus ten percent.