Patent Description:
A gas turbine engine may employ secondary flow system inlets that are positioned about the low pressure compressor in the inner fixed structure section of the inner cowl in general fluid communication with a fan duct of the gas turbine engine. More specifically, the inner surface of the outer nacelle and the outer surface of the inner cowl at the low pressure compressor section define a fan duct through which fan airflow is received. This fan duct is the source of airflow for IFS-mounted secondary flow systems.

<CIT> discloses a turbofan engine having a fan portion in fluid communication with a core stream and a bypass stream of air separated by splitters disposed both upstream and downstream of the fan portion. A fluid passage is defined between the splitters. The turbofan engine has a plurality of vortex generators, each of the vortex generators positioned on the leading edge of a respective fan blade proximate the upstream splitter and the core stream.

<CIT> discloses a heat sink for location in a fluid flow, including a heat sink base and a plurality of heat dissipating elements, such as elongate fins, extending from the base of the heat sink.

<CIT> discloses reducing the pressure drag on the skin of an aircraft by rigidly securing boundary layer influencing members to the skin of the aircraft.

From a first aspect of the invention, an inner cowl for a gas turbine engine as claimed in claim <NUM> is provided.

In various embodiments, the vane body is oriented at a non-zero angle with respect to a centerline axis of the inlet.

In various embodiments, a first height of the vane body is less than a second height of the inlet.

In various embodiments, the inner cowl comprises an inner fixed structure (IFS).

In various embodiments, the vane body is disposed relative to the inlet such that a wake vortex generated by the vane body during operation of the gas turbine engine is completely or nearly completely ingested by the inlet.

In various embodiments, the vane body is configured to convert kinetic energy associated with a circumferential flow direction into a vortex to introduce a higher momentum flow of the vortex into the inlet of the secondary flow system to minimize propagation of a flow separation off a sidewall of the inlet.

In various embodiments, the vane body is configured to straighten the airflow diverted by a bifurcation of the gas turbine engine.

In various embodiments, the first height is a maximum height of the vane body and the second height is a maximum height of the inlet.

From a further aspect of the invention, a gas turbine engine as claimed in claim <NUM> is disclosed.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein. The scope of the disclosure is defined by the appended claims.

An external turning vane of the present disclosure is provided forward from a secondary flow system inlet. A wake vortex generated by the external turning body may be completely or nearly completely ingested by the inlet for improving secondary flow system inlet total pressure recovery. An external turning vane of the present disclosure minimizes air flow separation inside of the inlet.

<FIG> illustrates a schematic view of a gas turbine engine, in accordance with various embodiments. An xyz-axis is provided for ease of illustration. Gas turbine engine <NUM> may include core engine <NUM>. Core air flow C flows through core engine <NUM> and is expelled through exhaust outlet <NUM> surrounding tail cone <NUM>.

Core engine <NUM> drives a fan <NUM> arranged in a bypass flow path B. Air in bypass flow path B flows in the aft direction (z-direction) along bypass flow path B. At least a portion of bypass flow path B may be defined by outer nacelle <NUM> and inner cowl <NUM> (also referred to herein as an inner fixed structure (IFS)). Fan case <NUM> may surround fan <NUM>. Fan case <NUM> may be housed within outer nacelle <NUM>.

Outer nacelle <NUM> typically comprises two halves which are typically mounted to a pylon. According to various embodiments, multiple guide vanes <NUM> may extend radially between core engine <NUM> and fan case <NUM>. Upper bifurcation <NUM> and lower bifurcation <NUM> may extend radially between the outer nacelle <NUM> and inner cowl <NUM> in locations opposite one another to accommodate engine components such as wires and fluids, for example.

Inner cowl <NUM> may surround core engine <NUM> and provide core compartment <NUM>. Various components may be provided in core compartment <NUM> such as fluid conduits, compressed air ducts, and/or air-oil coolers, for example.

With respect to <FIG>, elements with like element numbering, as depicted in <FIG>, are intended to be the same and will not necessarily be repeated for the sake of clarity.

Referring to <FIG>, the front section of a gas turbine engine <NUM> having an example secondary flow system <NUM> constructed in accordance with the present disclosure is provided. Among other things, the front section of the gas turbine engine <NUM> may generally include outer nacelle <NUM>, inner cowl <NUM>, a splitter <NUM>, fan blades <NUM>, exit guide vanes <NUM> and a fan duct <NUM> associated therewith. Moreover, airflow entering into the gas turbine engine <NUM> may be split by the splitter <NUM> into bypass flow path B flowing through the fan duct <NUM> and core air flow C flowing into the low pressure compressor.

The secondary flow system <NUM> of the gas turbine engine <NUM> of <FIG> may be disposed on an outer surface of the inner fixed structure, and generally composed of at least one secondary flow system <NUM> and an external turning vane <NUM> adjacent thereto. In various embodiments, the external turning vane is disposed downstream, or aft, of exit guide vanes <NUM>.

With reference to <FIG>, secondary flow system <NUM> receives bypass air through an inlet <NUM>. In this regard, inlet <NUM> is in fluid communication with bypass flow path B. The upper bifurcation <NUM> may divert airflow through bypass flow path B around the upper bifurcation <NUM>. The upper bifurcation <NUM> may tend to turn the bypass air, illustrated by arrow <NUM> in <FIG>, in the circumferential direction, causing the bypass air to enter inlet <NUM> at an angle with respect to a centerline axis <NUM> of inlet <NUM>. This circumferential flow migration of the bypass air may tend to cause flow separation at a sidewall located circumferentially adjacent upper bifurcation <NUM>, such as the upper side <NUM>, of inlet <NUM>, which may result in a total pressure deficit and decreased system mass air flow. In this regard, an external turning vane is provided, which may improve total pressure distribution across the inlet <NUM> and maximize system mass air flow.

In various embodiments, external turning vane <NUM> is disposed in front of inlet <NUM>. That is, external turning vane <NUM> is disposed upstream from inlet <NUM>. In various embodiments, external turning vane <NUM> is formed as a plate. In this regard, external turning vane <NUM> comprises a vane body <NUM> extending radially from the IFS <NUM>. In various embodiments, external turning vane <NUM> is made of a metal such as a steel alloy, stainless steel, titanium, aluminum, or any other metal or alloy thereof. In various embodiments, external turning vane <NUM> comprises one or more machined metal parts. In various embodiments, external turning vane <NUM> comprises a fiber-reinforced composite material. External turning vane <NUM> may be configured to turn bypass air in an axial direction (e.g., parallel to a centerline axis A-A' of the gas turbine engine <NUM> (see <FIG>)), illustrated by arrow <NUM>, entering inlet <NUM>, for example, such that the bypass air enters inlet <NUM> substantially parallel to centerline axis <NUM>.

With reference to <FIG>, due to the aerodynamic effects of external turning vane <NUM>, wake vortices <NUM> may be generated by external turning vane <NUM> and ingested by inlet <NUM>. In this regard, external turning vane <NUM> may be placed in front of inlet <NUM> such that the wake vortices <NUM> generated thereby are completely ingested by inlet <NUM>. In various embodiments, external turning vane <NUM> is placed in front of inlet <NUM> such that the wake vortices <NUM> generated thereby are completely or nearly completely ingested by inlet <NUM> at or near upper side <NUM>, which tends to minimize flow separation from upper side <NUM>, improve total pressure distribution across the inlet <NUM>, and maximize system mass air flow through secondary flow system <NUM>. External turning vane <NUM> may be configured to turn the airflow (e.g., see bypass air <NUM> of <FIG>) in the bypass flow path such that the wake vortices <NUM> of the external turning vane <NUM> are directed at the portion of the inlet <NUM> challenged by flow separation. External turning vane <NUM> may be configured to convert kinetic energy associated with a circumferential flow direction (e.g., see bypass air <NUM> of <FIG>) into a vortex (e.g., wake vortices <NUM>) to introduce a higher momentum flow of the vortex into the inlet <NUM> of the secondary flow system <NUM> to minimize propagation of a flow separation off a sidewall (e.g., upper side <NUM>) of the inlet <NUM>. As used herein, the term "higher momentum flow" means that the momentum of the wake vortices <NUM> is greater than the local momentum of the circumferential flow of bypass air <NUM>.

In various embodiments, the aerodynamic effects of external turning vane <NUM> are further enhanced by optimizing the angle of the external turning vane <NUM> relative to centerline axis <NUM> to provide optimal vortex size and sidewall (e.g., upper side <NUM>) interaction. In various embodiments, external turning vane <NUM> is oriented at a non-zero angle with respect to centerline axis <NUM>. In various embodiments, external turning vane <NUM> is angled towards centerline axis <NUM>. External turning vane <NUM> may be angled towards centerline axis <NUM> with the forward edge <NUM> pointed towards centerline axis <NUM>. In various embodiments, a height <NUM> (also referred to herein as a first height), as measured in the radial direction, of external turning vane <NUM> may be less than or equal to a height <NUM> (also referred to herein as a second height) of the inlet <NUM>. In this manner, the aerodynamic effects of external turning vane <NUM> are minimized or eliminated at locations radially outward from inlet <NUM>. In various embodiments, height <NUM> is the maximum height of external turning vane <NUM>. In various embodiments, height <NUM> is the maximum height of inlet <NUM>. In various embodiments, the length <NUM> of external turning vane <NUM> is greater than the height <NUM> of external turning vane <NUM>.

External turning vane <NUM> may be attached to IFS <NUM> via any known method suitable for attaching vanes to a cowl structure. For example, external turning vane <NUM> may be attached to IFS <NUM> via one or more fasteners, such as a rivet, a threaded fastener, a bolt, or a screw, among other types of fasteners. Furthermore, external turning vane <NUM> may be bonded to IFS <NUM> via an adhesive.

Claim 1:
An inner cowl (<NUM>) of a gas turbine engine (<NUM>), characterised by the inner cowl (<NUM>)comprising:
an inlet (<NUM>) for a secondary flow system (<NUM>) disposed on the inner cowl, the inlet (<NUM>) in fluid communication with a bypass flow path (B); and
an external turning vane (<NUM>) disposed upstream from the inlet (<NUM>), the external turning vane (<NUM>) comprising a vane body (<NUM>) extending radially from the inner cowl and disposed upstream from the inlet (<NUM>) of the secondary flow system (<NUM>), the vane body (<NUM>) configured to turn an airflow in the bypass flow path (B) towards an axial direction and to introduce higher momentum flow of a vortex into the inlet (<NUM>) to minimize flow separation on a sidewall of the inlet (<NUM>).