Patent Description:
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as bypass air and into a compressor in a core engine. The air in the compressor is compressed and delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.

As can be appreciated, many of the components in a gas turbine engine see very high temperatures. As an example, the turbine section and, in particular, its early stages see hot products of combustion. In addition, the compressor and, in particular, its downstream most stages also see very high temperatures. This is particularly true as the pressures developed in the compressor sections are increasing.

Thus, it is known to supply cooling air to various rotating components such as in the turbine section and/or compressor section.

A prior art gas turbine having the features of the preamble to claim <NUM> is disclosed in <CIT>. Document <CIT> discloses a further known gas turbine engine.

The present invention provides a gas turbine engine in accordance with claim <NUM>.

The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>.

"Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]<NUM> (where <MAT>).

<FIG> shows an intercooled cooling air system <NUM>. A high pressure compressor <NUM> is provided with a tap <NUM> for tapping air to be utilized as cooling air. Note the tap <NUM> is from an intermediate location in the high pressure compressor. In alternative embodiments, the tap could be from a low pressure compressor.

Stated broadly, the tap in the <FIG> embodiment is from a location upstream of a downstream most location <NUM> in the high pressure compressor <NUM>. The tapped air at line <NUM> passes through a first leg <NUM> of a heat exchanger and back into a second leg <NUM> where it is returned through an inner housing <NUM>. The heat exchanger <NUM>/<NUM> sits in a chamber <NUM> in this embodiment, which is radially inward of the bypass duct B.

As shown, a valve <NUM> selectively allows the air from bypass duct B to pass over the heat exchanger <NUM>/<NUM>. A control <NUM> is shown controlling the position of the valve <NUM>. Air at line <NUM> inward of the housing <NUM> passes through a shutoff valve <NUM> into a cooling compressor <NUM>. The cooling compressor <NUM> is provided with a drive <NUM>.

A system to stop the cooling compressor <NUM> from compressing is provided. In the illustrated example, the system is a clutch <NUM> which can disconnect the cooling compressor <NUM> from its drive <NUM>. Alternatively, the drive <NUM> could be an electric motor and simply stopped. The control <NUM> controls the shutoff valve <NUM> and the clutch <NUM>. It is desirable that the control be programmed such that the compression of air by the cooling compressor <NUM> is effectively stopped before the valve <NUM> is shut down to block the flow of air from line <NUM> reaching the cooling compressor <NUM>.

Downstream of the cooling compressor <NUM>, the air passes into a line <NUM> and through struts <NUM> in a diffuser <NUM> radially into a mixing chamber <NUM>. In this embodiment, high pressure air may be tapped at <NUM> into the mixing chamber <NUM>. The high pressure air tapped <NUM> may be air downstream of the downstream most location <NUM> in the high pressure compressor <NUM>. The air from the mixing chamber <NUM> is shown passing to cool a disk and rim <NUM> of a downstream most location in the high pressure compressor <NUM>. The air is also shown passing between a fixed housing <NUM> and a rotating shaft portion <NUM>, which is part of the high pressure spool as described with regard to <FIG>. A chamber <NUM> between the housing <NUM> and outer periphery of the shaft portion <NUM> receives the cooling airflow. That air passes through a tangential on-board injector <NUM> ("TOBI") and then passes to cool the first stage blade <NUM> and vane <NUM> of a high pressure turbine.

As shown, the wall <NUM> is radially inward of a combustor <NUM> and a chamber <NUM> is intermediate to the two.

As known, the chamber <NUM> receives air downstream of the downstream most location in the high pressure compressor and, thus, is at high temperature. As the air passes to the TOBI <NUM> and through the chamber <NUM>, it may be heated by those high temperatures, which reduces the efficiency of the overall system.

In embodiments, an insulation feature is placed both on at least a majority of the surface area of the housing <NUM> between the diffuser <NUM> and the TOBI <NUM>. An insulation material is also placed along the majority of the outer surface of the shaft portion <NUM> between the downstream most location of the high pressure compressor and the rotation of the first turbine blade <NUM>.

For purposes of this application, each of the housing <NUM> and shaft <NUM> are formed of an underlying base metal and an outer insulation material. The outer insulation material has better resistance to heat passage than does the underlying metal. Insulation in a gas turbine, and as may be defined in this application is a non-structural addition to a structure in that there is little or no structural contribution to the additional aspect involved. Further, the insulation in a gas turbine, may prevent fluid from passing on one side of the lower conductivity material which is sometimes referred to as "infiltration. " Such fluid passage would dramatically lower the value of the measures taken to apply the insulation. And, finally, the insulation may be introduced to the assembly by additional manufacturing steps and processes.

In an alternative embodiment shown schematically in <FIG>, the cooling system <NUM> taps air from a location at or downstream of the downstream most location <NUM> in the high pressure compressor <NUM>. Here, the air is shown tapped at <NUM> from a chamber radially outward of the combustor <NUM>. That air passes through a heat exchanger <NUM>, which is shown schematically being cooled, and then returned back inwardly through chamber <NUM> to the high pressure turbine <NUM>. Such passage of air may also include the wall <NUM> and shaft <NUM> as in the <FIG> embodiment. Thus, the same temperature challenges are raised.

<FIG> shows details of one embodiment of insulation material. The outer surface of the shaft <NUM>, which faces the wall <NUM>, is preferably provided with an insulation coating. Coating is preferred for the rotating structure as the attachment of sheets or other structure which might require mechanical attachment raises challenges with the centrifugal forces that the rotating structure will see. The underlying base metal <NUM> is provided with a metallic bond coat <NUM>. A thermally-grown oxide coating <NUM> is placed outwardly of the bond coat <NUM>. A ceramic topcoat <NUM> then surrounds the thermally-grown oxide.

In one embodiment, the ceramic topcoat <NUM> is composed of Yttria-stabilized zirconia.

An outer surface of the housing <NUM> includes the metallic base layer <NUM> and a double wall structure, such as provided by an attached outer wall <NUM>, which faces the rotating shaft surface <NUM>. An intermediate insulation material such as a ceramic fiber blanket <NUM> is placed between the walls <NUM> and <NUM>. Such ceramic fiber blankets are known for various applications and may be formed of bulk fibers produced by spinning processes. The blanket <NUM> may be formed from pure alumina-silica. Further, the blanket <NUM> may be a continuous blanket and may be mechanically sewn with double needles to provide better integrity to the surface on both sides of the blanket.

In embodiments, the pipes and, particularly, those downstream of the heat exchanger <NUM>/<NUM> (or <NUM>) may also be provided with insulation. This would include connections <NUM> and, in particular, connection <NUM>.

In addition, monitors are provided to ensure proper operation of valve <NUM>, valve <NUM>, clutch <NUM>, and predetermine any undesirable pressures or temperatures in the conduit <NUM>.

Stated another way, in an embodiment, a gas turbine engine includes rotatable components including components within a compressor section and a turbine section housed within an outer housing. A tap is connected to tap air that has passed at least partially through the compressor section The tap is connected to pass through a heat exchanger and connected to pass into a flow path between a rotating surface and a non-rotating surface. The flow path is connected to cool at least one of said rotatable components. At least a portion of each of the non-rotating surface and the rotating surface are provided with a base metal, and an insulation material on a surface facing the other of the rotatable and non-rotatable surfaces.

Claim 1:
A gas turbine engine (<NUM>) comprising:
a plurality of rotating components housed within a compressor section (<NUM>) and a turbine section (<NUM>);
a first tap (<NUM>;<NUM>) connected to said compressor section (<NUM>) and configured to deliver air at a first pressure;
a heat exchanger (<NUM>;<NUM>) connected downstream of said first tap (<NUM>;<NUM>); and
a flowpath defined between a rotating surface and a non-rotating surface, wherein the flowpath is connected downstream of said heat exchanger (<NUM>;<NUM>) and is configured to deliver air to at least one of said plurality of rotating components, wherein at least a portion of said non-rotating surface and said rotating surface comprising a base metal (<NUM>,<NUM>); and characterised by
an insulation material (<NUM>,<NUM>,<NUM>,<NUM>,<NUM>) disposed on the rotating surface and the non-rotating surface along the flowpath;
wherein there is a combustor (<NUM>;<NUM>) radially outward of said non-rotating surface, and a chamber (<NUM>) intermediate said combustor (<NUM>;<NUM>) and said non-rotating surface is connected to receive compressed air downstream of a downstream most location (<NUM>) in said compressor section (<NUM>); and
wherein said insulation material (<NUM>,<NUM>,<NUM>,<NUM>,<NUM>) on said rotating surface is a coating (<NUM>,<NUM>,<NUM>), said coating (<NUM>,<NUM>,<NUM>) includes an outer ceramic topcoat (<NUM>) facing the insulation material (<NUM>,<NUM>) on said non-rotating surface, a metallic bond coat (<NUM>) intermediate said ceramic topcoat (<NUM>) and the underlying base metal (<NUM>) in said rotating surface, and a thermally-grown oxide coating (<NUM>) intermediate said metallic bond coat (<NUM>) and said ceramic topcoat (<NUM>).