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 a method for reducing contrails during operation of aircraft having heat engines, and to an aircraft having a heat engine.

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

<CIT> relates to a mechanical device to suppress contrail formation.

<CIT> relates to an aircraft propulsion system for reducing or eliminating aircraft vapour trail formation.

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

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

Some embodiments of the invention are as claimed in the dependent claims.

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

<FIG> schematically illustrates an aircraft propulsion system in the form of an example hydrogen steam injected inter-cooled 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 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 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 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. Water may also be used as a cooling flow <NUM> to cool cooling air flow <NUM> communicated from the compressor section <NUM> to the turbine section <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>.

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.

Referring to <FIG>, with continued reference to <FIG>, the example condenser/water separator <NUM> is schematically shown. The condenser <NUM> includes a plurality of rotating passages <NUM> that rotate to induce a centrifugal force on water from the gas flow <NUM>. A coolant flow <NUM> from a coolant reservoir <NUM> is placed in thermal communication with the gas flow <NUM> to transform a portion of steam into liquid water. The liquid water, schematically indicated at <NUM> is directed by a collector <NUM> through an opening <NUM> to the water storage <NUM>. The coolant flow <NUM> is directed to an outer periphery <NUM> of the condenser <NUM> and into thermal communication with the gas flow <NUM>.

The rotating passages <NUM> are disposed about a condenser axis <NUM> and supported on a shaft <NUM>. The shaft <NUM> is supported by bearing systems <NUM> in one disclosed embodiment. The condenser <NUM> includes a first axial portion <NUM> that initially received the gas flow <NUM>. A transition region <NUM> is disposed between the axil portion <NUM> and the rotating passages <NUM>. The transition region <NUM> induces an initial swirl on the incoming gas flow <NUM>. From the transition region, the gas flow <NUM> enters the rotating passages <NUM>. The gas flow <NUM> in the rotating passages <NUM> includes an axial component <NUM> and a transverse component <NUM>. The transverse component <NUM> provides for the heavier liquid water to be driven radially outward into the collector <NUM>. The collector <NUM> surrounds the rotating passages and includes at least one opening <NUM> for liquid water condensate water flow. It should be appreciated that the collector <NUM> may include a plurality of openings <NUM> arranged to capture water flow <NUM> at various axial and radial locations.

In the disclosed example, a motor <NUM> is coupled to the shaft <NUM> to rotate the rotating passages <NUM>. The motor <NUM> is configured to rotate the passages <NUM> at a predefined speed determined to generate sufficient centrifugal forces in the direction indicated at <NUM> to drive liquid water flow <NUM> outward into the collector <NUM>.

In this example embodiment, the collector <NUM> is a formed sheet material that substantially surrounds the passages through the axis portion <NUM>, the transition region <NUM> and the rotating passages <NUM>. The passages through the condenser <NUM> maybe formed from sheet metal material, as a cast part or by additive manufacturing processes. Moreover, it should be appreciated that it is within the contemplation and scope of this disclosure that the example condenser <NUM> may be formed using other manufacturing and assembly processes.

Referring to <FIG>, with continued reference to <FIG>, the rotating passages <NUM> and the transition region are schematically shown with gas flows <NUM> and the coolant flow <NUM>. In one disclosed embodiment, the gas flow <NUM> and the coolant flow <NUM> are maintained separately although in thermal communication. In another disclosed embodiment, the coolant flow <NUM> is comprised of a coolant that is allowed to mix with exhausted gas flows <NUM> that are exhausted from the condenser <NUM>.

Referring to <FIG>, another example condenser embodiment is schematically shown and indicated at <NUM>. The example condenser <NUM> includes the same features as the previously described condenser <NUM> but does not include the motor <NUM>. Instead, the condenser <NUM> uses the axial momentum of the high energy exhaust gas flow <NUM> to drive rotation of the plurality of rotating passages <NUM>. The rotating passages <NUM> are spiral shaped such that as the axial gas flow <NUM> impacts sides of the passages <NUM>, an auto rotation is induced that provides the desired centrifugal forces to separate the liquids as a water flow. The passages <NUM> are supported on the shaft <NUM> and bearings <NUM> and uses the inherent momentum of the gas flow <NUM> to drive rotation.

It should be understood that it is within the contemplation of this disclosure that the rotating passages <NUM> may be configured to auto rotate in some engine operating conditions according to the example described in <FIG> and also may include a motor <NUM> to drive rotation in other operating conditions. Accordingly, the motor <NUM> may be provided and used only during specific operating conditions where the momentum of the gas flow <NUM> may not provide the desired magnitude of centrifugal force.

Referring to <FIG>, surfaces <NUM> of the passages <NUM> may be provided with a coating <NUM> that aids in the condensation of water from the gas flow <NUM>. In one disclosed example embodiment, the coating <NUM> comprise a hydrophilic material. In another disclosed example embodiment, the coating <NUM> comprises a hydrophobic material. Still in another disclosed example embodiment, the coating <NUM> may be a pattern of alternating sections made from a hydrophobic material and other sections including hydrophilic material to drive and gather condensate from the gas flow <NUM>.

Referring to <FIG>, surfaces <NUM> within the example condensers <NUM>, <NUM> maybe textured to enhance thermal transfer into the gas flow <NUM>. In one disclosed example, the surfaces <NUM> include a texture <NUM> formed from a plurality of raised bumps. The texture <NUM> may be configured to induce a turbulent flow near the surfaces <NUM> to enhance thermal transfer and thereby accelerate cooling and liquid extraction.

Accordingly, the example condensers <NUM>, <NUM> provide for the transformation of water in gas form within the gas flow into liquid water that is then separated and stored for injection back into the engine to improve overall propulsive system efficiency.

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 including a core flow path (C) where air is compressed in a compressor section (<NUM>), communicated to a combustor section, mixed with a hydrogen fuel and ignited to generate a high energy 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;
a condenser (<NUM>) arranged along the core flow path (C) and configured to extract water from the high energy gas flow (<NUM>), the condenser (<NUM>) including a plurality of rotating passages (<NUM>) disposed in a collector (<NUM>), wherein the passages (<NUM>) are configured to rotate about a condenser axis (<NUM>) to generate a transverse pressure gradient to direct water out of the high energy gas flow (<NUM>) toward the collector (<NUM>); and
an evaporator (<NUM>) arranged along the core flow path (C) and configured to receive a portion of the water extracted by the condenser (<NUM>) to generate a steam flow, wherein the steam flow is injected into the core flow path (C) upstream of the turbine section (<NUM>).