Patent Description:
<CIT> discloses a hybrid expander cycle with a turbo-generator and cooled power electronics.

<CIT> discloses a hybrid expander cycle with intercooling and a turbo-generator.

<CIT> discloses a gas turbine using a cryogenic fuel and extracting work therefrom.

According to an aspect of the present invention, there is provided a gas turbine engine in accordance with claim <NUM>.

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, 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 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.

According to another aspect of the present invention, there is provided a method of retrofitting a gas turbine engine with a dual cycle intercooled architecture in accordance with claim <NUM>.

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.

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> and is designated generally by reference character <NUM>. Other embodiments and/or aspects of this disclosure are shown in <FIG>. 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>, an aircraft <NUM> can include an engine <NUM>, where the engine can be a propulsive energy engine (e.g. creating thrust for the aircraft <NUM>), or a non-propulsive energy engine, and a fuel system <NUM>. As described herein, the engine <NUM> is a turbofan engine, although the present technology may likewise be used with other engine types. The engine <NUM> includes a compressor section <NUM> having a compressor <NUM> in a primary gas path <NUM> to supply compressed air to a combustor <NUM> of the aircraft engine <NUM>, the primary gas path <NUM> including fluidly in series the combustor <NUM> and nozzle manifold <NUM> for issuing fluid to the combustor <NUM>.

More specifically the primary gas path <NUM> includes, in fluid series communication: an air inlet <NUM>, the compressor <NUM> fluidly connected to the air inlet <NUM>, the combustor <NUM> fluidly connected to an outlet <NUM> of the compressor <NUM>, and a turbine section <NUM> fluidly connected to an outlet <NUM> of the combustor <NUM>, the turbine section <NUM> operatively connected to the compressor <NUM> to drive the compressor <NUM>.

A main output shaft <NUM> is operatively connected to the turbine section <NUM> to be driven by the turbine section <NUM>. A heat exchanger <NUM> is fluidly connected between a liquid hydrogen supply <NUM> and the compressor <NUM>. A gas conduit <NUM> is fluidly connected to the primary gas path <NUM>, and a fluid conduit <NUM>, carrying liquid hydrogen from the liquid hydrogen supply <NUM>, in thermal communication with the gas conduit <NUM>, but is fluidly isolated from the gas conduit <NUM>, fluidly connects the liquid hydrogen supply <NUM> to the primary gas path <NUM>.

The fluid conduit <NUM> has a liquid hydrogen inlet <NUM> and a gaseous hydrogen outlet <NUM> fluidly connected to the liquid hydrogen inlet <NUM>. A liquid hydrogen pump <NUM> is fluidly connected to the liquid hydrogen inlet <NUM> of the heat exchanger <NUM> and operable to supply liquid hydrogen to the liquid hydrogen inlet <NUM>. It is contemplated that any suitable liquid hydrogen supply can be used, for example, the liquid hydrogen can be pumped from aircraft cryogenic tanks <NUM> using the liquid hydrogen pump <NUM> mounted on an accessory pad (e.g. on an engine accessory gearbox), or the pump <NUM> may be driven externally by other means.

An expansion turbine <NUM> having a gas inlet <NUM> is fluidly connected to the gaseous hydrogen outlet <NUM> and a gas outlet <NUM> fluidly connected to the gas inlet <NUM>, where the gas outlet <NUM> of the expansion turbine <NUM> is fluidly connected to the combustor <NUM> via conduit <NUM>.

In certain embodiments, the compressor <NUM> includes a first stage (e.g. low pressure) compressor <NUM> and a second stage (e.g. high pressure) compressor <NUM>. The second stage compressor <NUM> is in fluid communication with the first stage compressor <NUM> through an inter-stage duct <NUM>. The heat exchanger <NUM> is fluidly connected to the primary gas path <NUM> between the adjacent first and second stage compressors <NUM>, <NUM> such that the inter-stage duct <NUM> forms a compressor air conduit through the heat exchanger <NUM>. For example, hot compressed air from the first stage compressor <NUM> passes through conduit <NUM> to the second stage compressor <NUM>, where heat is exchanged in the heat exchanger <NUM> so that liquid hydrogen in the fluid conduit <NUM> is evaporated to gaseous hydrogen. This heat exchange serves the dual purpose of converting the liquid hydrogen <NUM> to gaseous hydrogen <NUM> to be used as fuel in the combustor <NUM>, and while also cooling the air inlet <NUM> of the compressor <NUM>, improving engine efficiency. The hydrogen (<NUM>, <NUM>) and compressor air are in fluid isolation from each other throughout their respective passages (conduits <NUM>, <NUM>) in the heat exchanger <NUM> to avoid mixing of air and hydrogen in the heat exchanger <NUM>, but are in thermal communication with one another for heat exchange between the hydrogen and compressor air in the heat exchanger <NUM>.

The hydrogen expansion turbine <NUM> is positioned downstream of the heat exchanger <NUM> and upstream of the combustor <NUM> relative to hydrogen flow (<NUM>, <NUM>). A rotatable element of the expansion turbine <NUM> (e.g. a turbine shaft <NUM>) is operatively connected to a gearbox <NUM> (e.g. a reduction gearbox for a propeller, accessory gearbox, or the like) to input additional rotational power to the gearbox <NUM>. More specifically, the expansion turbine shaft <NUM> is meshed with at least one gear <NUM> in the gearbox <NUM> such that when the liquid hydrogen <NUM> is converted to a gaseous state <NUM>, the power from the expanding gas is extracted through the expansion turbine <NUM>, driving the expansion turbine <NUM>, adding additional rotational power to the gearbox <NUM>. For example, the expansion turbine <NUM> is operatively connected to the main shaft <NUM> (e.g. via the gearbox <NUM> and output shaft <NUM>) to drive the main shaft <NUM> in parallel with the turbine section <NUM>. In this manner, the main shaft <NUM> is driven by combined power from the turbine section <NUM> and the expansion turbine <NUM>. In certain embodiments, the hydrogen expansion turbine <NUM> can be operatively connected to one or both of an electrical power generator <NUM> to drive the electrical power generator <NUM>, and an auxiliary air compressor <NUM> to drive the auxiliary air compressor <NUM>.

A gaseous hydrogen accumulator <NUM> is disposed in conduit <NUM> downstream of the heat exchanger <NUM> relative to hydrogen flow, wherein the gaseous hydrogen accumulator <NUM> is between the heat exchanger <NUM> and the combustor <NUM>. A gaseous hydrogen meter <NUM> is disposed in the conduit <NUM> downstream of the gaseous hydrogen accumulator <NUM> relative to hydrogen flow for controlling flow of hydrogen to the combustor <NUM>, the gaseous hydrogen meter <NUM> being between the accumulator <NUM> and the combustor <NUM>. After the gaseous hydrogen <NUM> is evaporated and extracted through the expansion turbine <NUM>, the expanded low pressure gaseous hydrogen <NUM> is collected and stored in the gaseous hydrogen accumulator <NUM> and then regulated to a pressure where it can then be metered (e.g. via meter <NUM>) to provide combustor ready hydrogen gas to the combustor <NUM>.

In certain embodiments, a controller <NUM> is operatively connected to the gaseous hydrogen meter <NUM> and at least one sensor included in any of the gearbox <NUM>, the hydrogen expansion turbine <NUM>, and/or the turbine section <NUM>. The controller <NUM> can include machine readable instructions that cause the controller to receive input <NUM> for a command power, receive input <NUM> from at least one of the gearbox <NUM>, the hydrogen expansion turbine <NUM>, and/or the turbine section <NUM>, and adjust the flow of gaseous hydrogen <NUM> via the gaseous hydrogen meter <NUM> to achieve the command power, based on the input (e.g. signals <NUM>, <NUM>, <NUM>, <NUM>) received by the controller <NUM>. In embodiments, the controller <NUM> can additionally receive input from a compressor pressure (e.g. P3 pressure, upstream of the accumulator <NUM>) and input from the accumulator <NUM> downstream of the compressor pressure.

In yet another aspect of the present disclosure, there is provided a method, which is not part of the claimed subject-matter. For example, the controller <NUM> can include machine readable instruction operable to execute the method. The method includes, supplying liquid hydrogen <NUM> to a heat exchanger <NUM> and expanding the liquid hydrogen <NUM> to gaseous hydrogen <NUM> with heat supplied to the heat exchanger <NUM>, supplying the heat to the heat exchanger <NUM> with compressed air from a first stage compressor <NUM>, where expanding the liquid hydrogen <NUM> to gaseous hydrogen <NUM> includes cooling the compressed air from the first stage compressor <NUM>, compressing cooled air from the heat exchanger <NUM>, and combusting the gaseous hydrogen <NUM> with the compressed cooled air in the combustor <NUM>.

In embodiments, the method includes extracting power from a flow of gaseous hydrogen <NUM> with a hydrogen expansion turbine <NUM> downstream of the heat exchanger <NUM>. In certain embodiments, the method includes combining power from the expansion turbine <NUM> with power from a main shaft <NUM> driven by a turbine section <NUM> to drive an output shaft <NUM> for example to generate thrust and/or electrical power. In certain embodiments, the method includes receiving input from at least one of the gearbox <NUM>, the hydrogen expansion turbine <NUM>, and/or the turbine section <NUM> (e.g. signals <NUM>, <NUM>, <NUM>, <NUM>) and outputting a command <NUM> to the gaseous hydrogen meter <NUM> to adjust flow of gaseous hydrogen <NUM> to the combustor <NUM> to achieve a command power output at the output shaft <NUM>.

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 <NUM>, heat exchanger <NUM>, a gaseous hydrogen accumulator <NUM>, a gaseous hydrogen meter <NUM>, an expansion turbine <NUM> between the heat exchanger <NUM> and the gaseous hydrogen accumulator <NUM>, can be introduced in an existing turbine engine. The system can then be connected as follows: connecting the liquid hydrogen supply <NUM> to the heat exchanger <NUM> via a liquid hydrogen pump <NUM> in a first line (e.g. fluid conduit <NUM>), connecting the heat exchanger <NUM> to the expansion turbine <NUM> via a second line (e.g. an upstream portion of conduit <NUM>), and connecting the expansion turbine <NUM> to the combustor via a third line (e.g. a downstream portion of conduit <NUM>), wherein the gaseous hydrogen accumulator <NUM> and gaseous hydrogen meter <NUM> are disposed in the third line.

In certain embodiments, for example as provided in <FIG>, an engine <NUM> can be similarly retrofit with similar architecture as in gas turbine engine <NUM>. For brevity, the description of common elements that have been described above are not repeated. The engine <NUM> can be a hydrogen powered aircraft engine <NUM>, for example the engine <NUM> can be a heat engine, a gas turbine engine, a reciprocating heat engine, a rotary heat engine, or the like. The engine <NUM> can be fed by primary gas path <NUM> (e.g. an air supply) and gaseous hydrogen <NUM>.

The liquid hydrogen tank <NUM> is fluidly connected to the liquid hydrogen supply <NUM> for supplying hydrogen to a hydrogen conversion module <NUM>.

The hydrogen conversion module <NUM> can be included within the engine <NUM>, for combustion of hydrogen within the combustor <NUM>. The hydrogen conversion module <NUM> is fluidly connected to the inlet <NUM> of the expansion turbine <NUM> for driving the expansion turbine <NUM>. In certain embodiments, the hydrogen conversion module <NUM> can includes all of heat exchanger <NUM>, liquid H2 pump <NUM>, accumulator <NUM>, and a meter <NUM>. However, it is contemplated that the hydrogen conversion module <NUM> 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 <NUM> is used.

A hydrogen combustion module <NUM> can be fluidly connected to the outlet <NUM> of the expansion turbine <NUM> and operatively connected to the output shaft <NUM>, for converting thermal energy into rotational energy to drive the output shaft <NUM>. The engine <NUM> is operatively connected to a driven component <NUM> via the output shaft <NUM>. The driven component <NUM> is driven by the output shaft <NUM> of the engine <NUM> 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 <NUM> can optionally be operatively connected to another driven component <NUM> for driving the driven component <NUM> in series with driven component <NUM> via shaft <NUM>. It is contemplated that the driven component <NUM> can be the same or different than driven component <NUM>. It is also contemplated that the driven component <NUM> can be optionally operatively connected to driven component <NUM> via shaft <NUM> for driving driven component <NUM> in parallel with driven component <NUM>.

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.

Claim 1:
A gas turbine engine (<NUM>), comprising:
a primary gas path (<NUM>) having, in fluid series communication: an air inlet (<NUM>), a compressor (<NUM>) fluidly connected to the air inlet (<NUM>), a combustor (<NUM>) fluidly connected to an outlet of the compressor (<NUM>), and a turbine section (<NUM>) fluidly connected to an outlet of the combustor section (<NUM>), the turbine section (<NUM>) operatively connected to the compressor (<NUM>) to drive the compressor (<NUM>);
an output shaft (<NUM>) operatively connected to the turbine section (<NUM>) to be driven by the turbine section (<NUM>);
a heat exchanger (<NUM>) having:
a gas conduit (<NUM>) fluidly connected to the primary gas path (<NUM>); and
a fluid conduit (<NUM>) in fluid isolation from the gas conduit (<NUM>) and in thermal communication with the gas conduit (<NUM>), the fluid conduit (<NUM>) having a liquid hydrogen inlet (<NUM>) and a gaseous hydrogen outlet (<NUM>) fluidly connected to the liquid hydrogen inlet (<NUM>); and
an expansion turbine (<NUM>) having a gas inlet (<NUM>) fluidly connected to the gaseous hydrogen outlet (<NUM>) and a gas outlet (<NUM>) fluidly connected to the gas inlet (<NUM>), the gas outlet (<NUM>) of the expansion turbine (<NUM>) being fluidly connected to the combustor (<NUM>), characterised in that:
the compressor (<NUM>) has multiple compressor sections and the gas conduit (<NUM>) of the heat exchanger (<NUM>) is fluidly connected to the primary gas path (<NUM>) at a location between adjacent compressor sections of the multiple compressor sections; and
the gas turbine engine (<NUM>) further comprises:
a gaseous hydrogen accumulator (<NUM>) downstream of the heat exchanger (<NUM>) relative to hydrogen flow, wherein the gaseous hydrogen accumulator (<NUM>) is between the heat exchanger (<NUM>) and the combustor (<NUM>); and
a gaseous hydrogen meter (<NUM>) downstream of the gaseous hydrogen accumulator (<NUM>) relative to hydrogen flow for controlling flow of hydrogen to the combustor (<NUM>), wherein the gaseous hydrogen meter (<NUM>) is between the accumulator (<NUM>) and the combustor (<NUM>), wherein the expansion turbine (<NUM>) is a hydrogen expansion turbine (<NUM>) downstream of the heat exchanger (<NUM>) and upstream of the combustor (<NUM>) relative to hydrogen flow, and a turbine shaft (<NUM>) of the hydrogen expansion turbine (<NUM>) is operatively connected to a gearbox (<NUM>).