Patent Publication Number: US-2023133397-A1

Title: Dual cycle intercooled hydrogen engine architecture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of U.S. patent application Ser. No. 17/331,942 filed May 27, 2021 the content of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to gas turbine engines, and more particularly to gas turbine engines with intercooling. There is always a need in the art for improvements to engine architecture in the aerospace industry. 
     SUMMARY 
     In one aspect of the present disclosure, there is provided a gas turbine engine. The gas turbine engine includes a primary gas path having, in fluid series communication: an air inlet, a compressor fluidly connected to the air inlet, a combustor fluidly connected to an outlet of the compressor, and a turbine section fluidly connected to an outlet of the combustor section. The turbine section is operatively connected to the compressor to drive the compressor; and an output shaft is operatively connected to the turbine section to be driven by the turbine section. In certain embodiments, the gas turbine engine includes a heat exchanger having a gas conduit fluidly connected to the primary gas path, and a fluid conduit in fluid isolation from the gas conduit and in thermal communication with the gas conduit, the fluid conduit having a liquid hydrogen inlet and a gaseous hydrogen outlet fluidly connected to the liquid hydrogen inlet. 
     In certain embodiments, the gas turbine engine includes an expansion turbine having a gas inlet fluidly connected to the gaseous hydrogen outlet and a gas outlet fluidly connected to the gas inlet, the gas outlet of the expansion turbine being fluidly connected to the combustor. In certain embodiments, the compressor has multiple compressor sections and the gas conduit of the heat exchanger is fluidly connected to the primary gas path at a location between adjacent compressor sections of the multiple compressor sections. 
     In certain embodiments, a liquid hydrogen pump is fluidly connected to the liquid hydrogen inlet of the heat exchanger and operable to supply liquid hydrogen to the liquid hydrogen inlet of the heat exchanger. In certain embodiments the gas turbine engine can include one or both of: a gaseous hydrogen accumulator downstream of the heat exchanger relative to hydrogen flow, such that the gaseous hydrogen accumulator is between the heat exchanger and the combustor, and a gaseous hydrogen meter downstream of the gaseous hydrogen accumulator relative to hydrogen flow for controlling flow of hydrogen to the combustor, such that the gaseous hydrogen meter is between the accumulator and the combustor. 
     In certain embodiments, the expansion turbine is operatively connected to the output shaft to drive the output shaft in parallel with the turbine section. In certain embodiments, the gas turbine engine includes a gearbox, where the gear box is operatively connected to a main shaft driven by a turbine section of the gas turbine engine. The gearbox can further include an output shaft driven by combined power from the turbine section and the expansion turbine. In certain embodiments, an outlet of the hydrogen expansion turbine is in fluid communication with the combustor to provide combustor ready hydrogen gas to the combustor and to add additional rotational power to the gearbox. 
     In certain embodiments, the expansion turbine is operatively connected to one or both of: an electrical power generator to drive the electrical power generator, and an auxiliary air compressor to drive the auxiliary air compressor. 
     In certain embodiments, a controller is operatively connected to the gaseous hydrogen meter and at least one sensor in any of the gearbox, the hydrogen expansion turbine, and/or the turbine section, The controller can include machine readable instructions that cause the controller to receive input for a command power, receive input from at least one of the gearbox, the hydrogen expansion turbine, and/or the turbine section, adjust the flow of gaseous hydrogen via the gaseous hydrogen meter to achieve the command power. 
     In another aspect of the present disclosure, there is provided a primary gas path having, in fluid series communication: an air inlet, a compressor fluidly connected to the air inlet, a combustor fluidly connected to an outlet of the compressor, and a turbine section fluidly connected to an outlet of the combustor, the turbine section operatively connected to the compressor to drive the compressor, wherein the compressor has multiple compressor sections. An output shaft is operatively connected to the turbine section to be driven by the turbine section. The gas turbine engine includes a heat exchanger having a gas conduit fluidly connected to the primary gas path, and a fluid conduit in fluid isolation from the gas conduit and in thermal communication with the gas conduit, the fluid conduit having a liquid hydrogen inlet and a gaseous hydrogen outlet fluidly connected to the liquid hydrogen inlet, wherein and gas conduit of the heat exchanger is fluidly connected to the primary gas path at a location between adjacent compressor sections of the multiple compressor sections. In certain embodiments, the compressor, combustor, and turbine section are part of one of: a gas turbine engine, a reciprocating heat engine, and a rotary heat engine. 
     In certain embodiments, a liquid hydrogen pump is in fluid communication with the liquid hydrogen inlet of the heat exchanger, where the combustor is also in fluid communication to receive hydrogen downstream of the heat exchanger relative to hydrogen flow for combustion of hydrogen and air. 
     In certain embodiments, the gas turbine engine includes a hydrogen expansion turbine in fluid communication to receive hydrogen from the gaseous hydrogen outlet of the heat exchanger, the expansion turbine including a rotatable component operatively connected to the expansion turbine to be rotated by rotation of the expansion turbine where the rotatable component is also operatively connected to a gearbox. In certain embodiments, an outlet of the hydrogen expansion turbine is in fluid communication with the combustor to provide combustor ready hydrogen gas to the combustor and to add additional rotational power to the gearbox. 
     In certain embodiments, the gas turbine engine includes a gaseous hydrogen accumulator downstream of the heat exchanger relative to hydrogen flow where the gaseous hydrogen accumulator is between the heat exchanger and the combustor. In certain embodiments, the gas turbine engine includes a gaseous hydrogen meter downstream of the gaseous hydrogen accumulator relative to hydrogen flow for controlling flow of hydrogen to the combustor, wherein the gaseous hydrogen meter is between the accumulator and the combustor. 
     In yet another aspect of the present disclosure, there is provided a method of operating an aircraft. The method comprises, expanding a flow of liquid hydrogen to a flow of gaseous hydrogen, extracting kinetic energy from the flow of gaseous hydrogen to rotate a rotatable component of the aircraft, after the extracting, combusting the flow of gaseous hydrogen in a combustor of a gas turbine engine of the aircraft. In certain embodiments, using rotation of the rotatable component, generating one or both of: thrust, and electrical power. 
     In embodiments, the method includes extracting power from a flow of gaseous hydrogen with a hydrogen expansion turbine downstream of the heat exchanger. In certain embodiments, the method includes combining power from the expansion turbine with power from a main shaft driven by a turbine section to drive an output shaft. In certain embodiments, the method includes receiving input from at least one of the gearbox, a hydrogen expansion turbine, and/or the turbine section, and outputting a command to the gaseous hydrogen meter to achieve a command power output at the output shaft. 
     In certain embodiments, the method includes retrofitting a gas turbine engine with a dual cycle intercooled architecture. In certain such embodiments, retrofitting can include introducing a liquid hydrogen supply, introducing the heat exchanger to a duct between the first stage compressor and the second stage compressor, introducing a gaseous hydrogen accumulator and a gaseous hydrogen meter between the heat exchanger and the second stage compressor, and introducing an expansion turbine between the heat exchanger and the gaseous hydrogen accumulator, the expansion turbine operatively connected to a gear box. In certain such embodiments, retrofitting can further include connecting the liquid hydrogen supply to the heat exchanger via a liquid hydrogen pump in a first line, connecting the heat exchanger to the expansion turbine via a second line, and connecting the expansion turbine to the second stage compressor via a third line, wherein the gaseous hydrogen accumulator and gaseous hydrogen meter are disposed in the third line. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG.  1    is a schematic view of an embodiment of an aircraft in accordance with this disclosure; 
         FIG.  2    is a schematic diagram of an embodiment of a gas turbine engine constructed in accordance with the present disclosure, showing a dual cycle intercooled engine architecture; and 
         FIG.  3    is a schematic diagram of another embodiment of a gas turbine engine constructed in accordance with the present disclosure, showing another dual cycle intercooled engine architecture. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown in  FIG.  1    and is designated generally by reference character  100 . Other embodiments and/or aspects of this disclosure are shown in  FIG.  2   . The systems and methods described herein can be used to improve engine efficiency, reduce carbon emissions, and improve power to weight ratio. 
     Traditionally, hydrocarbon fuels are used to power gas turbine engines, however, it is possible to use a variety of fuels for the combustion portion of the Brayton Cycle, for example pure hydrogen, non-hydrocarbon fuels, or mixes. When hydrogen is used as the fuel, it is possible to operate the gas turbine engine with little or no pollutants in the exhaust. Moreover, various means of intercooling/evaporating are also possible when using hydrogen fuel, as described and contemplated herein. As a non-limiting example, such means of intercooling/evaporating may include in-situ pre-coolers in the engine inlet or axial intercoolers between axial compressors. 
     In certain embodiments, referring to  FIG.  1   , an aircraft  1  can include an engine  100 , where the engine can be a propulsive energy engine (e.g. creating thrust for the aircraft  1 ), or a non-propulsive energy engine, and a fuel system  100 . As described herein, the engine  100  is a turbofan engine, although the present technology may likewise be used with other engine types. 
     The engine  100  includes a compressor section  102  having a compressor  104  in a primary gas path  106  to supply compressed air to a combustor  108  of the aircraft engine  100 , the primary gas path  106  including fluidly in series the combustor  108  and nozzle manifold  110  for issuing fluid to the combustor  108 . 
     More specifically the primary gas path  106  includes, in fluid series communication: an air inlet  112 , the compressor  104  fluidly connected to the air inlet  112 , the combustor  108  fluidly connected to an outlet  114  of the compressor  104 , and a turbine section  116  fluidly connected to an outlet  118  of the combustor  108 , the turbine section  116  operatively connected to the compressor  104  to drive the compressor  104 . 
     A main output shaft  120  is operatively connected to the turbine section  116  to be driven by the turbine section  116 . A heat exchanger  122  is fluidly connected between a liquid hydrogen supply  124  and the compressor  104 . A gas conduit  126  is fluidly connected to the primary gas path  106 , and a fluid conduit  128 , carrying liquid hydrogen from the liquid hydrogen supply  124 , in thermal communication with the gas conduit  126 , but is fluidly isolated from the gas conduit  126 , fluidly connects the liquid hydrogen supply  124  to the primary gas path  106 . 
     The fluid conduit  128  has a liquid hydrogen inlet  130  and a gaseous hydrogen outlet  132  fluidly connected to the liquid hydrogen inlet  130 . A liquid hydrogen pump  133  is fluidly connected to the liquid hydrogen inlet  130  of the heat exchanger  122  and operable to supply liquid hydrogen to the liquid hydrogen inlet  130 . It is contemplated that any suitable liquid hydrogen supply can be used, for example, the liquid hydrogen can be pumped from aircraft cryogenic tanks  131  using the liquid hydrogen pump  133  mounted on an accessory pad (e.g. on an engine accessory gearbox), or the pump  133  may be driven externally by other means. 
     An expansion turbine  134  having a gas inlet  136  is fluidly connected to the gaseous hydrogen outlet  132  and a gas outlet  138  fluidly connected to the gas inlet  136 , where the gas outlet  138  of the expansion turbine  134  is fluidly connected to the combustor  108  via conduit  139 . 
     In certain embodiments, the compressor  104  includes a first stage (e.g. low pressure) compressor  140  and a second stage (e.g. high pressure) compressor  142 . The second stage compressor  142  is in fluid communication with the first stage compressor  140  through an inter-stage duct  144 . The heat exchanger  122  is fluidly connected to the primary gas path  106  between the adjacent first and second stage compressors  140 ,  142  such that the inter-stage duct  144  forms a compressor air conduit through the heat exchanger  122 . For example, hot compressed air from the first stage compressor  140  passes through conduit  126  to the second stage compressor  142 , where heat is exchanged in the heat exchanger  122  so that liquid hydrogen in the fluid conduit  128  is evaporated to gaseous hydrogen. This heat exchange serves the dual purpose of converting the liquid hydrogen  119  to gaseous hydrogen  121  to be used as fuel in the combustor  108 , and while also cooling the air inlet  112  of the compressor  104 , improving engine efficiency. The hydrogen ( 119 ,  121 ) and compressor air are in fluid isolation from each other throughout their respective passages (conduits  126 ,  138 ) in the heat exchanger  122  to avoid mixing of air and hydrogen in the heat exchanger  122 , but are in thermal communication with one another for heat exchange between the hydrogen and compressor air in the heat exchanger  122 . 
     The hydrogen expansion turbine  134  is positioned downstream of the heat exchanger  122  and upstream of the combustor  108  relative to hydrogen flow ( 119 ,  121 ). A rotatable element of the expansion turbine  134  (e.g. a turbine shaft  146 ) is operatively connected to a gearbox  148  (e.g. a reduction gearbox for a propeller, accessory gearbox, or the like) to input additional rotational power to the gearbox  128 . More specifically, the expansion turbine shaft  146  is meshed with at least one gear  150  in the gearbox  148  such that when the liquid hydrogen  119  is converted to a gaseous state  121 , the power from the expanding gas is extracted through the expansion turbine  134 , driving the expansion turbine  134 , adding additional rotational power to the gearbox  148 . For example, the expansion turbine  134  is operatively connected to the main shaft  120  (e.g. via the gearbox  148  and output shaft  151 ) to drive the main shaft  120  in parallel with the turbine section  116 . In this manner, the main shaft  120  is driven by combined power from the turbine section  116  and the expansion turbine  134 . In certain embodiments, the hydrogen expansion turbine  134  can be operatively connected to one or both of an electrical power generator  152  to drive the electrical power generator  152 , and an auxiliary air compressor  154  to drive the auxiliary air compressor  154 . 
     In certain embodiments, a gaseous hydrogen accumulator  156  is disposed in conduit  139  downstream of the heat exchanger  122  relative to hydrogen flow, wherein the gaseous hydrogen accumulator  156  is between the heat exchanger  122  and the combustor  108 . A gaseous hydrogen meter  158  is disposed in the conduit  139  downstream of the gaseous hydrogen accumulator  156  relative to hydrogen flow for controlling flow of hydrogen to the combustor  108 , the gaseous hydrogen meter  158  being between the accumulator  156  and the combustor  108 . After the gaseous hydrogen  121  is evaporated and extracted through the expansion turbine  134 , the expanded low pressure gaseous hydrogen  121  is collected and stored in the gaseous hydrogen accumulator  156  and then regulated to a pressure where it can then be metered (e.g. via meter  158 ) to provide combustor ready hydrogen gas to the combustor  108 . 
     In certain embodiments, a controller  160  is operatively connected to the gaseous hydrogen meter  158  and at least one sensor included in any of the gearbox  148 , the hydrogen expansion turbine  134 , and/or the turbine section  116 . The controller  160  can include machine readable instructions that cause the controller to receive input  145  for a command power, receive input  147  from at least one of the gearbox  128 , the hydrogen expansion turbine  134 , and/or the turbine section  136 , and adjust the flow of gaseous hydrogen  121  via the gaseous hydrogen meter  158  to achieve the command power, based on the input (e.g. signals  161 ,  162 ,  163 ,  164 ) received by the controller  160 . In embodiments, the controller  160  can additionally receive input from a compressor pressure (e.g. P3 pressure, upstream of the accumulator  156 ) and input from the accumulator  156  downstream of the compressor pressure. 
     In yet another aspect of the present disclosure, there is provided a method. For example, the controller  160  can include machine readable instruction operable to execute the method. The method includes, supplying liquid hydrogen  119  to a heat exchanger  122  and expanding the liquid hydrogen  119  to gaseous hydrogen  121  with heat supplied to the heat exchanger  122 , supplying the heat to the heat exchanger  122  with compressed air from a first stage compressor  140 , where expanding the liquid hydrogen  119  to gaseous hydrogen  121  includes cooling the compressed air from the first stage compressor  140 , compressing cooled air from the heat exchanger  122 , and combusting the gaseous hydrogen  121  with the compressed cooled air in the combustor  108 . 
     In embodiments, the method includes extracting power from a flow of gaseous hydrogen  121  with a hydrogen expansion turbine  134  downstream of the heat exchanger  122 . In certain embodiments, the method includes combining power from the expansion turbine  134  with power from a main shaft  120  driven by a turbine section  116  to drive an output shaft  151  for example to generate thrust and/or electrical power. In certain embodiments, the method includes receiving input from at least one of the gearbox  148 , the hydrogen expansion turbine  134 , and/or the turbine section  116  (e.g. signals  161 ,  162 ,  163 ,  164 ) and outputting a command  165  to the gaseous hydrogen meter  158  to adjust flow of gaseous hydrogen  121  to the combustor  108  to achieve a command power output at the output shaft  151 . 
     It is contemplated that a dual cycle intercooled architecture as described herein can be retrofit on an existing, conventional gas turbine engine. For example, any or all of a liquid hydrogen supply  124 , heat exchanger  122 , a gaseous hydrogen accumulator  156 , a gaseous hydrogen meter  158 , an expansion turbine  134  between the heat exchanger  122  and the gaseous hydrogen accumulator  156 , can be introduced in an existing turbine engine. The system can then be connected as follows: connecting the liquid hydrogen supply  124  to the heat exchanger  122  via a liquid hydrogen pump  133  in a first line (e.g. fluid conduit  128 ), connecting the heat exchanger  122  to the expansion turbine  134  via a second line (e.g. an upstream portion of conduit  139 ), and connecting the expansion turbine  134  to the combustor via a third line (e.g. a downstream portion of conduit  139 ), wherein the gaseous hydrogen accumulator  156  and gaseous hydrogen meter  158  are disposed in the third line. 
     In certain embodiments, for example as provided in  FIG.  3   , an engine  200  can be similarly retrofit with similar architecture as in gas turbine engine  100 . For brevity, the description of common elements that have been described above are not repeated. The engine  200  can be a hydrogen powered aircraft engine  200 , for example the engine  200  can be a heat engine, a gas turbine engine, a reciprocating heat engine, a rotary heat engine, or the like. The engine  200  can be fed by primary gas path  106  (e.g. an air supply) and gaseous hydrogen  121 . 
     The liquid hydrogen tank  131  is fluidly connected to the liquid hydrogen supply  124  for supplying hydrogen to a hydrogen conversion module  266 . 
     The hydrogen conversion module  266  can be included within the engine  200 , for combustion of hydrogen within the combustor  108 . The hydrogen conversion module  266  is fluidly connected to the inlet  136  of the expansion turbine  134  for driving the expansion turbine  134 . In certain embodiments, the hydrogen conversion module  266  can includes all of heat exchanger  122 , liquid H2 pump  133 , accumulator  156 , and a meter  158 . However, it is contemplated that the hydrogen conversion module  266  can be any suitable different combination of elements interconnected to be operable to provide a supply of gaseous hydrogen, for example a combination that is suitable to the particular engine with which the hydrogen conversion module  266  is used. 
     A hydrogen combustion module  268  can be fluidly connected to the outlet  138  of the expansion turbine  134  and operatively connected to the output shaft  151 , for converting thermal energy into rotational energy to drive the output shaft  151 . The engine  200  is operatively connected to a driven component  270  via the output shaft  151 . The driven component  270  is driven by the output shaft  151  of the engine  200  and can be a rotor, for example, or any one of, or any combination of a propeller, a fan, a compressor, a gearbox, an electric generator, or the like. In certain embodiments, the expansion turbine  134  can optionally be operatively connected to another driven component  272  for driving the driven component  272  in series with driven component  270  via shaft  274 . It is contemplated that the driven component  272  can be the same or different than driven component  270 . It is also contemplated that the driven component  270  can be optionally operatively connected to driven component  272  via shaft  276  for driving driven component  272  in parallel with driven component  270 . 
     With this method, the power generated by burning the hydrogen and then extracting the power through a power turbine is compounded by the power extracted by the expansion turbine and then combined through the gearbox. This architecture allows dual cycles of expansion and combustion of hydrogen with intercooling to be packaged within an existing turboprop nacelle loft, for example. 
     This architecture differs from other intercooled or expansion turbine engines in that it combines several engine improvements by making use of cold liquid hydrogen for cooling and expansion. The methods and systems of the present disclosure, as described above and shown in the drawings, provide for improved engine efficiency through intercooling. Additionally, inclusion of the expansion turbine allows for a smaller engine without sacrificing power output, therefore improving power to weight ratio. Carbon emissions may also be reduced or eliminated. Finally, this arrangement accomplishes these improvements in a compact package which would fit in existing nacelle loft lines (e.g. for a turboprop) therefore minimizing drag. 
     While the apparatus and methods of the subject disclosure have been shown and described, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure. 
     For example, the following particular embodiments of the present technology are likewise contemplated, as described herein next by clauses. 
     Clause 1. A gas turbine engine ( 100 ), comprising: 
     a primary gas path ( 106 ) having, in fluid series communication: an air inlet ( 112 ), a compressor ( 104 ) fluidly connected to the air inlet, a combustor ( 108 ) fluidly connected to an outlet ( 114 ) of the compressor, and a turbine section ( 116 ) fluidly connected to an outlet ( 118 ) of the combustor section, the turbine section operatively connected to the compressor to drive the compressor; 
     an output shaft ( 151 ) operatively connected to the turbine section to be driven by the turbine section; 
     a heat exchanger ( 122 ) having:
         a gas conduit ( 126 ) fluidly connected to the primary gas path, and   a fluid conduit ( 128 ) in fluid isolation from the gas conduit and in thermal communication with the gas conduit, the fluid conduit having a liquid hydrogen inlet ( 128 ) and a gaseous hydrogen outlet ( 132 ) fluidly connected to the liquid hydrogen inlet;       

     an expansion turbine ( 134 ) having a gas inlet ( 136 ) fluidly connected to the gaseous hydrogen outlet and a gas outlet ( 138 ) fluidly connected to the gas inlet, the gas outlet of the expansion turbine being fluidly connected to the combustor. 
     Clause 2. The gas turbine engine of Clause 1, further comprising a liquid hydrogen pump ( 133 ) fluidly connected to the liquid hydrogen inlet of the heat exchanger and operable to supply liquid hydrogen to the liquid hydrogen inlet of the heat exchanger.
 
Clause 3. The gas turbine engine of Clause 1, further comprising one or both of:
 
     a gaseous hydrogen accumulator ( 156 ) downstream of the heat exchanger relative to hydrogen flow, wherein the gaseous hydrogen accumulator is between the heat exchanger and the combustor; and 
     a gaseous hydrogen meter ( 158 ) downstream of the gaseous hydrogen accumulator relative to hydrogen flow for controlling flow of hydrogen to the combustor, wherein the gaseous hydrogen meter is between the accumulator and the combustor. 
     Clause 4. The gas turbine engine of Clause 1, wherein the expansion turbine is operatively connected to the output shaft to drive the output shaft in parallel with the turbine section.
 
Clause 5. The gas turbine engine of Clause 4, further comprising a gearbox ( 148 ), and wherein the gear box is operatively connected to a main shaft ( 120 ) driven by the turbine section of the gas turbine engine, wherein the gearbox further includes an output shaft ( 151 ) driven by combined power from the turbine section and the expansion turbine.
 
Clause 6. The gas turbine engine of Clause 5, wherein the expansion turbine is operatively connected to one or both of: an electrical power generator ( 152 ) to drive the electrical power generator, and an auxiliary air compressor ( 154 ) to drive the auxiliary air compressor.
 
Clause 7. The gas turbine engine of Clause 1, wherein the compressor has multiple compressor sections and the gas conduit of the heat exchanger is fluidly connected to the primary gas path at a location between adjacent compressor sections of the multiple compressor sections, further comprising:
 
     a gaseous hydrogen accumulator downstream of the heat exchanger relative to hydrogen flow, wherein the gaseous hydrogen accumulator is between the heat exchanger and the combustor; 
     a gaseous hydrogen meter downstream of the gaseous hydrogen accumulator relative to hydrogen flow for controlling flow of hydrogen to the combustor, wherein the gaseous hydrogen meter is between the accumulator and the combustor; and 
     a hydrogen expansion turbine downstream of the heat exchanger and upstream of the combustor relative to hydrogen flow, wherein a turbine shaft of the hydrogen expansion turbine is operatively connected to a gearbox. 
     Clause 8. The gas turbine engine of Clause 7, wherein an outlet of the hydrogen expansion turbine is in fluid communication with the combustor to provide combustor ready hydrogen gas to the combustor and to add additional rotational power the gearbox, wherein the gear box is operatively connected to a main shaft driven by the turbine section of the gas turbine engine, wherein the gearbox further includes an output shaft driven by combined power from the turbine section and the expansion turbine.
 
Clause 9. The gas turbine engine of Clause 8, further comprising, a controller ( 160 ) operatively connected to the gaseous hydrogen meter and at least one sensor in any of the gearbox, the hydrogen expansion turbine, and/or the turbine section, wherein the controller includes machine readable instructions that cause the controller to:
 
     receive input for a command power; 
     receive input from at least one of the gearbox, the hydrogen expansion turbine, and/or the turbine section 
     receive input from compressor pressure; 
     receive input from accumulator downstream pressure; and 
     adjust the flow of gaseous hydrogen via the gaseous hydrogen meter to achieve the command power. 
     Clause 10. A gas turbine engine ( 100 ), comprising: 
     a primary gas path ( 106 ) having, in fluid series communication: an air inlet ( 112 ), a compressor ( 104 ) fluidly connected to the air inlet, a combustor ( 108 ) fluidly connected to an outlet ( 114 ) of the compressor, and a turbine section ( 116 ) fluidly connected to an outlet ( 118 ) of the combustor, the turbine section operatively connected to the compressor to drive the compressor, wherein the compressor has multiple compressor sections; 
     an output shaft ( 151 ) operatively connected to the turbine section to be driven by the turbine section; 
     a heat exchanger ( 122 ) having:
         a gas conduit ( 126 ) fluidly connected to the primary gas path, and   a fluid conduit ( 128 ) in fluid isolation from the gas conduit and in thermal communication with the gas conduit, the fluid conduit having a liquid hydrogen inlet ( 130 ) and a gaseous hydrogen outlet ( 132 ) fluidly connected to the liquid hydrogen inlet,       

     wherein the gas conduit of the heat exchanger is fluidly connected to the primary gas path at a location between adjacent compressor sections of the multiple compressor sections. 
     Clause 11. The gas turbine engine of Clause 10, wherein the compressor, combustor, and turbine section are part of one of: a gas turbine engine, a reciprocating heat engine, and a rotary heat engine.
 
Clause 12. The gas turbine engine of Clause 10, further comprising a liquid hydrogen pump in fluid communication with the liquid hydrogen inlet of the heat exchanger; and wherein the combustor is also in fluid communication to receive hydrogen downstream of the heat exchanger relative to hydrogen flow for combustion of hydrogen and air.
 
Clause 13. The gas turbine engine of Clause 10 or 11, further comprising a hydrogen expansion turbine in fluid communication to receive hydrogen from the gaseous hydrogen outlet of the heat exchanger, the expansion turbine including a rotatable component operatively connected to the expansion turbine to be rotated by rotation of the expansion turbine, wherein the rotatable component is also operatively connected to a gearbox.
 
Clause 14. The gas turbine engine of Clause 13, wherein an outlet of the hydrogen expansion turbine is in fluid communication with the combustor to provide combustor ready hydrogen gas to the combustor and to add additional rotational power to the gearbox.
 
Clause 15. The gas turbine engine of Clause 10, further comprising:
 
     a gaseous hydrogen accumulator ( 156 ) downstream of the heat exchanger relative to hydrogen flow, wherein the gaseous hydrogen accumulator is between the heat exchanger and the combustor; and 
     a gaseous hydrogen meter ( 158 ) downstream of the gaseous hydrogen accumulator relative to hydrogen flow for controlling flow of hydrogen to the combustor, wherein the gaseous hydrogen meter is between the accumulator and the combustor. 
     Clause 16. A method of operating an aircraft, comprising: 
     expanding a flow of liquid hydrogen to a flow of gaseous hydrogen; 
     extracting kinetic energy from the flow of gaseous hydrogen to rotate a rotatable component of the aircraft; and 
     after the extracting, combusting the flow of gaseous hydrogen in a combustor of a gas turbine engine ( 100 ) of the aircraft, supplying the heat to a heat exchanger ( 122 ) with compressed air from a first stage compressor ( 140 ), wherein expanding the liquid hydrogen to gaseous hydrogen includes cooling the compressed air from the first stage compressor; 
     compressing cooled air from the heat exchanger; and 
     combusting the gaseous hydrogen in the compressed cooled air. 
     Clause 17. The method of Clause 16, further comprising, using rotation of the rotatable component, generating one or both of: thrust, and electrical power.
 
Clause 18. The method of Clause 16, wherein the component is a turbine ( 116 ) of the gas turbine engine and the method further includes generating thrust by rotating an output shaft ( 151 ) of the gas turbine engine using rotation of the turbine, wherein the generating the thrust includes converting the rotation of the turbine into a slower rotation of the output shaft; and
 
     wherein the expanding the flow of liquid hydrogen includes cooling a compressed airflow passing through the gas turbine engine to heat up the flow of liquid hydrogen. 
     Clause 19. A method of retrofitting a gas turbine engine with a dual cycle intercooled architecture, wherein retrofitting includes: 
     introducing a liquid hydrogen supply ( 134 ); 
     introducing a heat exchanger ( 122 ) to a duct between the first stage compressor ( 140 ) and the second stage compressor ( 142 ); 
     introducing a gaseous hydrogen accumulator ( 156 ) and a gaseous hydrogen meter ( 158 ) between the heat exchanger and the second stage compressor, 
     introducing an expansion turbine ( 134 ) between the heat exchanger and the gaseous hydrogen accumulator, the expansion turbine operatively connected to a gear box. 
     Clause 20. The method as recited in Clause 19, further comprising, connecting the liquid hydrogen supply to the heat exchanger via a liquid hydrogen pump ( 133 ) in a first line, connecting the heat exchanger to the expansion turbine via a second line, and connecting the expansion turbine to the second stage compressor via a third line, wherein the gaseous hydrogen accumulator and gaseous hydrogen meter are disposed in the third line.