Patent Description:
Although current engine systems have improved propulsive efficiency, aircraft engine manufacturers continue to seek further improvements to engine performance including improvements to thermal, transfer and propulsive efficiencies.

<CIT> discloses a heat exchanger system according to the preamble of claim <NUM>.

<CIT> discloses high efficiency ducted heat exchanger systems, <CIT> discloses an aircraft ram air inlet with a multi-member closure flap, <CIT> discloses a heat exchanger arrangement, and <CIT> discloses a reconfigurable heat transfer system for a gas turbine inlet.

According to a first aspect, there is provided a heat exchanger system for a propulsion system inlet duct as set forth in claim <NUM>.

According to a further aspect, there is provided a method as set forth in claim <NUM>.

<FIG> is a schematic view of an example aircraft propulsion system <NUM> disposed within an aircraft structure <NUM>. The aircraft structure <NUM> may be the aircraft fuselage and/or a portion of a wing or other lift generating aircraft structure. A propulsor assembly <NUM> is disposed within the aircraft structure <NUM> and draws an upper boundary layer flow <NUM> along an upper surface <NUM> and a lower boundary layer flow <NUM> from along a lower surface <NUM> into an inlet duct assembly <NUM>. The propulsor assembly <NUM> generates thrust and exhausts the ingested flows <NUM>, <NUM> through an exhaust duct <NUM>.

The inlet duct assembly <NUM> includes an upper inlet duct <NUM> and a lower inlet duct <NUM> that merge into a common inlet duct <NUM> forward of the propulsor assembly <NUM>. The air flows from the upper inlet duct <NUM> and the lower inlet duct <NUM> are merged within the common inlet duct <NUM> and communicated to the propulsor assembly <NUM>. The propulsor assembly <NUM> imparts energy to the inlet flows to generate a propulsive flow that is exhausted through the exhaust duct <NUM>.

The ducting of airflow into the propulsor assembly <NUM> is of a limited size due to being disposed within the aircraft structure <NUM> rather than disposed within a nacelle. The limited size of the inlet duct <NUM> constrains the amount of airflow available for cooling engine aircraft systems <NUM>. A disclosed propulsion system embodiment <NUM> includes heat exchanger assemblies <NUM>, <NUM> with an increased thermal transfer area without increasing duct size. The disclosed heat exchanger assemblies <NUM>, <NUM> further provide desired airflow communicated to the propulsor assembly <NUM>.

The example inlet duct assembly <NUM> includes an upper inlet duct <NUM> that draws boundary layer airflow <NUM> from the top surface <NUM> and a lower inlet duct <NUM> that draws boundary layer airflow <NUM> from the bottom surface <NUM>. Each of the upper inlet duct <NUM> and the lower inlet duct <NUM> feed a common duct <NUM> just forward of the propulsor assembly <NUM>. The propulsor assembly <NUM> includes a fan <NUM> that generates propulsive thrust. The inlet duct assembly <NUM> provides for converging and diverging airflow to facilitate low airflow velocity and low pressure drops that provide improved propulsive efficiencies.

Each of the upper inlet duct <NUM> and the lower inlet duct <NUM> provide a diverging configuration that provides desired airflow pressures and velocities. The limited size of the ducting can reduce the area available to provide for thermal transfer. The disclosed example heat exchanger assemblies <NUM>, <NUM> disposed in respective inlet ducts <NUM>, <NUM> include features to increase thermal transfer capabilities within the constraints of the existing airflow.

Referring to <FIG> and <FIG> with continued reference to <FIG>, the inlet duct assembly <NUM> is shown with the upper inlet duct <NUM> and the lower inlet duct <NUM> separated by a splitter <NUM> and merging into the common duct <NUM>. The common duct <NUM> communicates air to the propulsor assembly <NUM> that is disposed within a propulsor space <NUM>. Airflow is then exhausted through an aft heat exchanger <NUM> disposed in the aft duct <NUM>. In the disclosed duct assembly embodiment, the upper inlet duct <NUM> is larger than the lower inlet duct <NUM>. The disclosed upper inlet duct <NUM> and lower inlet duct <NUM> are rectangularly shaped with each having a height and width that define a cross-sectional flow area transverse to an axis extending through each duct <NUM>, <NUM>.

The upper duct <NUM> is disposed along an upper longitudinal axis <NUM> that is angled relative to an engine axis A (<FIG>). The lower duct <NUM> is disposed along a lower longitudinal axis <NUM> that is also angled relative to the engine axis A.

The upper inlet duct <NUM> has a maximum height <NUM> (<FIG>) and a width <NUM> (<FIG>). The width <NUM> is uniform for the entire duct <NUM>. The height diverges from the inlet toward the maximum height <NUM> that is disposed just prior to merging with the common duct <NUM>. The maximum cross-sectional area of the upper inlet duct <NUM>, in this example embodiment, is disposed at the location of the maximum height <NUM>.

The lower inlet duct <NUM> includes a height <NUM> (<FIG>) and a maximum width <NUM> (<FIG>) that is disposed just forward of the merge into the common duct <NUM>. The width <NUM> is constant and uniform along the lower duct <NUM> and the height diverges from the inlet toward the maximum height <NUM>.

The maximum heights <NUM>, <NUM> of the upper duct <NUM> and the lower duct <NUM> provide the maximum flow area. The heat exchanger assemblies <NUM> and <NUM> are disposed at or substantially adjacent the maximum height locations of each duct.

It should be understood, that the disclosed example ducts <NUM> and <NUM> diverge and converge along the height and are uniform along the width. However, it is within the contemplation and scope of this disclosure that the width of each of the ducts <NUM>, <NUM> may diverge and converge with the height remaining constant. Moreover, both the height and width of each of the ducts <NUM>, <NUM> may diverge and converge and such a configuration is within the contemplation and scope of this disclosure. Furthermore, with any diverging converging duct configuration, the disclosed example heat exchanger assemblies <NUM>, <NUM> provide a corresponding shape and may be offset both in height and width. Accordingly, the disclosed heat exchanger assembly <NUM>, <NUM> provides an increase in thermal transfer area relative to a maximum duct area for increased thermal transfer efficiencies.

Referring to <FIG> with continued reference to <FIG> and <FIG>, the upper heat exchanger assembly <NUM> includes a forward portion <NUM> that is spaced apart axially forward of a first aft portion <NUM> and a second aft portion <NUM>. The aft portions <NUM>, <NUM> are disposed against side walls of the upper inlet duct <NUM> such that an open space <NUM> is disposed therebetween. An inner duct wall <NUM> is provided between the forward portion <NUM> and each of the aft portions <NUM>, <NUM>. The inner duct wall <NUM> prevents airflow within the axial space between the forward portion <NUM> and the aft portions <NUM>, <NUM> to assure that air flows through the heat exchanger assembly <NUM>.

The forward portion <NUM> is larger than the width of the open space between the aft portions <NUM>, <NUM> such that the forward portion <NUM> overlaps the aft portions <NUM>, <NUM>. The overlapping configuration is provided by a width <NUM> of the forward portion <NUM>. The width <NUM> is greater than that of the space between the aft portions <NUM>, <NUM>. Each of the aft portions <NUM>, <NUM> have a width <NUM>. In this disclosed embodiment, the width <NUM> of each of the aft portions <NUM>, <NUM> are the same.

A maximum cross-sectional area <NUM> of the upper duct <NUM> is shown in <FIG> and is based on the width of the upper duct <NUM> and the maximum height <NUM>. The maximum cross-sectional area <NUM> is defined within a plan transverse to the longitudinal axis <NUM> at the location of the maximum height <NUM>. The upper heat exchanger includes a total cross-sectional area that is a combination of area <NUM> of the forward portion <NUM> and cross-sectional areas <NUM> of each aft portion <NUM>, <NUM>. Note that the forward portion <NUM> and the aft portions <NUM>, <NUM> are shown skewed apart for illustration purposes. The combination of the cross-sectional areas <NUM> and <NUM> is larger than the cross-sectional area <NUM> within the upper duct <NUM>.

In one disclosed embodiment, the combined forward facing cross-sectional areas <NUM>, <NUM> of the upper heat exchanger assembly <NUM> is between <NUM>% and <NUM>% larger than the cross-sectional area <NUM>.

In another disclosed example embodiment, the combined forward facing cross-sectional areas <NUM>, <NUM> of the upper heat exchanger assembly <NUM> is between <NUM>% and <NUM>% larger than the cross-sectional area <NUM>.

In another disclosed example embodiment, the combined forward facing cross-sectional areas of the upper heat exchanger assembly <NUM> is between <NUM>% and <NUM>% larger than the cross-sectional area <NUM>.

In another disclosed example embodiment, the combined forward facing cross-sectional area of the upper heat exchanger assembly <NUM> is between <NUM>% and <NUM>% larger than the cross-sectional area <NUM>.

In another disclosed example embodiment, the combined forward facing cross-sectional area of the upper heat exchanger assembly <NUM> is around <NUM>% larger than the cross-sectional area <NUM>.

In another example embodiment, the combined forward facing cross-sectional area of the upper heat exchanger assembly <NUM> is around <NUM>% larger than the cross-sectional area <NUM> of the upper duct <NUM> at the location corresponding with the maximum height <NUM>.

The larger forward facing area provided by the heat exchanger assembly <NUM> provides increased thermal transfer capacity without increasing duct size.

Referring to <FIG> with continued reference to <FIG> and <FIG>, the lower inlet duct <NUM> includes the lower heat exchanger assembly <NUM>. The lower heat exchanger assembly <NUM> is scaled to fit into the smaller lower inlet duct <NUM> but maintains the proportionally larger front facing cross-sectional area as compared to the maximum front facing cross-sectional area located at the maximum height <NUM>. The lower inlet duct <NUM> includes a width <NUM> that is uniform along the entire duct. A height of the lower inlet duct <NUM> increases in a direction away from an inlet opening to the maximum height <NUM>. The maximum height <NUM> in this example is disposed at the axial location where the common inlet duct <NUM> begins.

A maximum cross-sectional area <NUM> (<FIG>) of the lower inlet duct <NUM> is smaller than a combined forward facing area of the lower heat exchanger <NUM>. The term forward facing refers to a plane defined transverse to the longitudinal axis <NUM> extending through the lower inlet duct <NUM>. The lower heat exchanger assembly <NUM> is configured in a similar manner to the upper heat exchanger assembly <NUM>. A forward portion <NUM> is spaced forward of a first aft portion <NUM> and a second aft portion <NUM>. A spacing <NUM> is disposed between the aft portions <NUM>, <NUM>. A duct <NUM> is provided in the axial space between the forward portion <NUM> and each of the aft portions <NUM>, <NUM>. The forward portion <NUM> includes a height <NUM> that is greater than the spacing <NUM> such that the forward portion <NUM> overlaps the aft portions <NUM>, <NUM> when viewed along the axis <NUM>.

The combined forward portion front facing cross-sectional area <NUM> and front facing cross-sectional area <NUM> of each of the aft portions <NUM>, <NUM> is larger than the cross-sectional area <NUM> (<FIG>) of the lower inlet duct <NUM>. The front facing cross-sectional area <NUM> is based on a height of <NUM> and a width <NUM> of each of the aft portions <NUM>, <NUM>. The front facing area <NUM> is based on the height <NUM> and width <NUM> of the forward portion <NUM>. In one disclosed embodiment, the front facing cross-sectional area provided by the lower heat exchanger assembly <NUM> is between <NUM>% and <NUM>% larger than the cross-sectional area <NUM>. In another disclosed example embodiment, the combined forward facing cross-sectional area of the lower heat exchanger assembly <NUM> is between <NUM>% and <NUM>% larger than the cross-sectional area <NUM> of the lower duct <NUM>. In another disclosed embodiment, the heat exchange cross-sectional area is around <NUM>% larger than the area <NUM> of the lower duct <NUM> at the location corresponding with the maximum height <NUM>.

It should be appreciated, that the combined cross-sectional area of both the upper and lower heat exchanger assemblies <NUM>, <NUM> provide a larger cross-sectional area than the combined duct cross-sectional areas by the same percentages as for each individual heat exchanger assembly <NUM>, <NUM>. The increased front facing cross-sectional areas provide desired thermal transfer efficiencies while maintaining duct sizing that provide desired aerodynamic properties that improve propulsive efficiencies.

Referring to <FIG>, another propulsion system embodiment is schematically shown and indicated at <NUM>. The example propulsion system <NUM> includes an upper heat exchanger assembly <NUM> disposed in the upper inlet duct <NUM>. A lower heat exchanger assembly <NUM> is disposed in the lower inlet duct <NUM>. The upper and lower heat exchanger assemblies <NUM>, <NUM> are configured in a similar offset manner to the heat exchanger assemblies <NUM>, <NUM>. The upper and lower heat exchanger assemblies <NUM>, <NUM> include an additional duct feature to provide desired airflow properties to the forward heat exchanger portions <NUM>, <NUM>.

The upper heat exchanger assembly <NUM> includes the duct <NUM> that directs airflow to the forward portion <NUM>. The example duct <NUM> is converging diverging duct that increases in cross-sectional area in a direction toward the forward face of the forward portion <NUM>.

The lower heat exchanger assembly <NUM> includes duct <NUM> that directs airflow to the forward portion <NUM>. The duct <NUM> is also a converging diverging duct with a cross-sectional area that increases in a direction toward the forward face of the forward portion <NUM>.

The converging/diverging ducts <NUM>, <NUM> provide for modification of airflows that can improve thermal transfer without significantly changing airflows to the propulsor assembly <NUM>. Moreover, the different duct geometries for the propulsor assembly <NUM> and the heat exchanger assemblies provide for individual tailoring of airflows to improve overall efficiencies.

Accordingly, the disclosed example heat exchanger assembles provide for increased thermal efficiencies with the constraints of inlet ducts of limited size. Moreover, the disclosed heat exchanger assemblies provide for increased overall engine efficiency by providing for ingestion of boundary layer flow and also provides a tailorable propulsor configuration that is adaptable to different aircraft structures.

Claim 1:
A heat exchanger system for a propulsion system inlet duct, the heat exchanger system comprising:
an inlet duct assembly (<NUM>) comprising an inlet duct (<NUM>, <NUM>), wherein the inlet duct (<NUM>, <NUM>) includes a cross-sectional area (<NUM>) defined in a plane taken transverse to a longitudinal length of the inlet duct (<NUM>, <NUM>); and
a heat exchanger assembly disposed in the inlet duct assembly (<NUM>), the heat exchanger assembly having a front facing cross-sectional area (<NUM>, <NUM>) that is greater than the cross-sectional area (<NUM>) of the inlet duct (<NUM>),
characterised in that:
the inlet duct is an upper inlet duct (<NUM>) and the inlet duct assembly (<NUM>) further includes a lower inlet duct (<NUM>), wherein the lower inlet duct (<NUM>) includes a cross-sectional area (<NUM>) defined in a plane taken transverse to a longitudinal length of the lower inlet duct (<NUM>);
the heat exchanger assembly includes an upper heat exchanger assembly (<NUM>) in the upper inlet duct (<NUM>) and a lower heat exchanger assembly (<NUM>) in the lower inlet duct (<NUM>); and
a combined front facing cross-sectional area (<NUM>, <NUM>) of the upper heat exchanger assembly (<NUM>) and the lower heat exchanger assembly (<NUM>) is greater than the combined cross-sectional areas (<NUM>, <NUM>) of the upper inlet duct (<NUM>) and the lower inlet duct (<NUM>).