Patent Description:
Reduction and/or elimination of carbon emissions generated by aircraft operation is a stated goal of aircraft manufacturers and airline operators. Gas turbine engines compress incoming core airflow, mix the compressed airflow with fuel that is ignited in a combustor to generate a high energy exhaust gas flow. Some energy in the high energy exhaust flow is recovered as it is expanded through a turbine section. Even with the use of alternate fuels, a large amount of energy in the form of heat is simply exhausted from the turbine section to atmosphere. The lost heat reduces the overall efficiency of the engine.

Turbine engine manufacturers continue to seek further improvements to engine performance including improvements to reduce environmental impact while improving propulsive efficiencies.

<CIT> relates to an exhaust gas treatment device that utilizes an exhaust gas energy and reduces contrails produced by a condensation following an expansion, an aircraft propulsion system having such an exhaust gas treatment device, and to a method for treating an exhaust gas stream.

A propulsion system for an aircraft according to an aspect of the invention is as claimed in claim <NUM>.

In another embodiment of the foregoing propulsion system, the cooled cooling air system includes a mixer configured to mix a cooling airflow with water to generate a mixed cooling air flow.

In another embodiment of any of the foregoing propulsion systems, the mixer includes at least one nozzle configured to inject a water flow into the cooling airflow.

In another embodiment of any of the foregoing propulsion systems, a boost pump for increasing a pressure of water provided to the mixer.

In another embodiment of any of the foregoing propulsion systems, water is transformed into a steam flow within the cooling evaporator.

In another embodiment of any of the foregoing propulsion systems, the steam flow from the cooling evaporator is communicated to a steam turbine.

In another embodiment of any of the foregoing propulsion systems, an intercooling system is configured to inject water into the compressor section.

In another embodiment of any of the foregoing propulsion systems, an intercooler evaporator is configured to transform water to steam prior to injection into the compressor section.

In another embodiment of any of the foregoing propulsion systems, the condenser communicates water to the water storage tank and a first pump is configured to move water from the storage tank to the cooled cooling air system.

In another embodiment of any of the foregoing propulsion systems, the turbine section includes a low pressure turbine configured to drive a fan through a low shaft.

In another embodiment of any of the foregoing propulsion systems, the turbine section includes a low pressure turbine, a high pressure turbine and an intermediate pressure turbine and the compressor section includes a high pressure compressor coupled to the high pressure turbine through a high shaft and a low pressure compressor coupled to the intermediate pressure turbine through an intermediate shaft.

In another embodiment of any of the foregoing propulsion systems, a steam turbine is driven by the steam flow from the evaporator, the steam turbine coupled to at least one of a low shaft, the high shaft and the intermediate shaft.

In another embodiment of any of the foregoing propulsion systems, a gearbox is coupled to the low shaft for driving a fan at a speed lower than the low pressure turbine.

Although the different aspects of the invention have the specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations.

<FIG> schematically illustrates an example hydrogen steam injected intercooled turbine engine that is generally indicated at <NUM>. The engine <NUM> includes a core engine with a core airflow path C through a fan <NUM>, a compressor section <NUM>, a combustor <NUM> and a turbine section <NUM>. The fan <NUM> drives inlet air as a core flow <NUM> into the compressor section <NUM>. In the compressor section <NUM>, the core flow <NUM> is compressed and communicated to a combustor <NUM>. In the combustor <NUM>, the core flow <NUM> is mixed with a hydrogen (H<NUM>) fuel flow <NUM> and ignited to generate a high energy gas flow <NUM> that expands through the turbine section <NUM> where energy is extracted and utilized to drive the fan <NUM> and the compressor section <NUM>. A bypass flow <NUM> may flow through the fan <NUM>, bypass the remaining components of the engine <NUM>, and exit through a fan nozzle <NUM>. The high energy gas flow <NUM> is exhausted from the turbine section <NUM> and communicated to a steam generation system <NUM> and a water recovery system <NUM> before being exhausted through a core nozzle <NUM>.

The example compressor section <NUM> includes a low pressure compressor (LPC) <NUM> and a high pressure compressor (HPC) <NUM>. The turbine section <NUM> includes a high pressure turbine (HPT) <NUM>, an intermediate pressure turbine (IPT) <NUM>, and a low pressure turbine (LPT) <NUM>. The turbines <NUM>, <NUM> and <NUM> are coupled to a corresponding compressor section. In this disclosed example, the high pressure turbine is coupled by a high shaft <NUM> to drive the high pressure compressor <NUM>. An intermediate shaft <NUM> couples the intermediate turbine <NUM> to the low pressure compressor <NUM>.

A low shaft <NUM> is coupled to the low pressure turbine <NUM> and a gearbox <NUM> to drive the fan <NUM>. The low shaft <NUM> may further be coupled to an electric machine <NUM> that is configured to impart and/or extract power into the low shaft <NUM>. The example gearbox <NUM> is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about <NUM>.

The engine <NUM> is configured to burn hydrogen provide by a fuel system <NUM>. The fuel system <NUM> includes a liquid hydrogen (LH<NUM>) tank <NUM> in communication with at least one pump <NUM>. The pump <NUM> drives a fuel flow <NUM> to the combustor <NUM>. LH<NUM> provides a thermal heat sink that can be utilized to cool various heat loads within the aircraft indicated at <NUM> and in the engine as indicated at <NUM>. The heat loads may include, for example and without limitation, super conducting electrics, a working fluid of an environmental control system of the aircraft, an air conditioning heat exchanger, and engine working fluid heat exchangers. Heat accepted into the hydrogen fuel flow increase the overall fuel temperature prior to injection into the combustor <NUM>.

A hydrogen expansion turbine <NUM> may be provided to reduce the pressure of the LH<NUM> fuel flow through expansion prior to communication to the combustor <NUM>. Expansion in the expansion turbine <NUM> provides for the temperatures and pressures of the fuel flow to enter the combustor <NUM> as a gas and not a liquid.

The steam injection system <NUM> uses the exhaust heat to generate a steam flow <NUM> by evaporating high pressure water through an evaporator <NUM>. The generated steam may then be injected into compressed core airflow at a location <NUM> for communication into the combustor <NUM> to improve performance by increasing turbine mass flow and power output without additional work required by the compressor section. In one example embodiment the location <NUM> is upstream of the combustor <NUM>. Steam flow from the evaporator <NUM> may drive a steam turbine <NUM> to provide an additional work output prior to injection into the combustor <NUM>.

The water recovery system <NUM> draws water, schematically indicated at <NUM>, from the high energy gas flow <NUM> and communicates the recovered water to water storage tank <NUM>. The water storage tank <NUM> operates as an accumulator to provide sufficient water for operation during various engine operating conditions. A condenser/water separator <NUM> is provided downstream of the turbine section <NUM> and the evaporator <NUM>. The condenser/separator <NUM> is in communication with a cold sink, schematically indicated at <NUM> for the condenser/separator <NUM> may be, for example, ram or fan air depending on the application and/or engine configuration.

The engine <NUM> has an increased power output from the injected steam <NUM> due to an increasing mass flow through the turbine section <NUM> without a corresponding increase in work from the compressor section <NUM>. An example engine operation cycle may include up to (or more than) <NUM>% steam-air-ratios (SAR) and may be assisted by a multiple fold (e.g., 2x, 3x, etc.) increase in moisture from burning H<NUM> as the fuel.

The water recovery system <NUM> includes the water storage tank <NUM> that receives water from the condenser/water separator <NUM> and provides for the accumulation of a volume of water required for production of sufficient amounts of steam. Water recovered from the exhaust gas flow is driven by a low pressure pump <NUM> and a high pressure pump <NUM> to the evaporator <NUM>.

A water intercooling flow <NUM> may be communicated to the compressor section <NUM> to reduce a temperature of the core airflow <NUM> and increase mass flow. Reduced temperatures and increased mass flow provided by injection of water increases compressor efficiency. The intercooling flow <NUM> mixes water to cool and increase the mass of the core airflow <NUM> through the compressor section <NUM>. Heating and boiling of water injected into the core airflow <NUM> lowers the temperature of the core airflow <NUM> and increases the mass flow through subsequent portions of the compressor section <NUM>.

A cooled cooling air system <NUM> is schematically shown that provides a cooling airflow to an inlet <NUM> in the turbine section <NUM>. In this disclosed example, the inlet <NUM> is disposed in the HPT <NUM>. Air flow <NUM> from a tap <NUM> in the compressor section <NUM> is communicated to the HPT <NUM> to cool components exposed to increased temperatures of the exhaust gas flow <NUM>. Although the example tap <NUM> is disposed in the HPC <NUM>, the tap <NUM> may be located anywhere within the compressor section <NUM> with pressures corresponding to pressure encountered in the turbine section <NUM>.

The cooling air <NUM> from the tap <NUM> is cooled in a mixer <NUM> that mixes an airflow <NUM> communicated from a tap <NUM> in the compressor section <NUM> with a water flow from the water tank <NUM>. A booster pump <NUM> is provided to drive the water into the mixer <NUM>. The example mixer <NUM> includes a plurality of nozzles <NUM> to inject water into the cooling airflow <NUM> to generate a mixed airflow <NUM> that is communicated to the inlet <NUM>. Heat from the cooling air <NUM> will vaporize the water flow and cool the mixed flow <NUM> to a temperature lower than exhausted from the compressor section <NUM>. The lower temperature provided by the mixed airflow <NUM> can provide for a reduced amount of cooling airflow that needs to be tapped from the compressor section <NUM>. Reducing the amount of flow tapped from the compressor section <NUM> provides for more of the work performed by the compressor section <NUM> to be utilized for generation of the exhaust gas flow.

Referring to <FIG>, another example cooled cooling air system <NUM> is schematically shown and includes a cooling evaporator <NUM>. The cooling evaporator <NUM> places the cooling airflow <NUM> tapped from the compressor section <NUM> into thermal communication with a water flow <NUM>. The heat from the tapped cooling air flow <NUM> vaporizes the water flow <NUM> in the evaporator <NUM> to create a steam flow <NUM>. The steam flow <NUM> is communicated to the steam generation system. A cooled cooling air flow <NUM> that is exhausted from the cooling evaporator <NUM> is communicated to the inlet <NUM> to cool the turbine <NUM>. Steam generated cooling evaporator <NUM> may be communicated to a steam turbine <NUM> to produce additional shaft power. Accordingly, the generation of steam in the cooling evaporator <NUM> both cools the cooling air flow <NUM> and recaptures energy in the form of heat that is utilized to drive the steam turbine <NUM>. Accordingly, the work produced by increasing the pressure of the cooling airflow <NUM> is recaptured and provides for increases in overall engine operating efficiencies.

Although the example engine <NUM> is described and shown by way of example as a three spool engine, other engine configurations, such as two-spool may also benefit from this disclosure and are within the contemplation and scope of this disclosure.

Although an example engine configuration is described by way of example, it will be appreciated that other engine configurations may include additional structures and features and are within the contemplation and scope of this disclosure.

Accordingly, the disclosed assemblies provide for the advantageous use of hydrogen fuel to improve engine efficiency and reduce carbon emission. The disclosed systems use the advantageous thermal capacity of hydrogen to maximize the recapture of heat and cool other working flows of the engine.

Claim 1:
A propulsion system for an aircraft comprising:
a core engine (<NUM>) including a core flow path (<NUM>) where air is compressed in a compressor section (<NUM>), communicated to a combustor (<NUM>), mixed with a hydrogen fuel and ignited to generate an exhaust gas flow (<NUM>) that is expanded through a turbine section (<NUM>);
a hydrogen fuel system (<NUM>) configured to supply hydrogen fuel to the combustor (<NUM>) through a fuel flow path (<NUM>);
a condenser (<NUM>) arranged along the core flow path (<NUM>) and configured to extract water (<NUM>) from the exhaust gas flow (<NUM>);
an evaporator (<NUM>) arranged along the core flow path (<NUM>) and configured to receive a portion of the water (<NUM>) extracted by the condenser (<NUM>) to generate a steam flow, wherein the steam flow is injected into the core flow path (<NUM>) upstream of the turbine section (<NUM>); and
a cooled cooling air system (<NUM>) configured to use water (<NUM>) extracted from the exhaust gas flow (<NUM>) for cooling a cooling airflow (<NUM>) communicated to the turbine section (<NUM>), wherein the cooled cooling air system (<NUM>) includes a cooling evaporator (<NUM>) in thermal communication with the cooling airflow (<NUM>) for cooling the cooling airflow (<NUM>).