Patent Description:
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as propulsion air. The fan also delivers air into a compressor where it is compressed to high pressures. This high pressure air is then 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.

One system that is typically included in gas turbine engines is a bleed valve to assist the compressor in maintaining stability at certain conditions. As an example, at low power conditions, such as idle, to maintain stability, it is known to bleed a relatively high percentage of the compressed air to a "dump.

Given that there may be high volumes of bleed air, this dump might be at a location which can accommodate relatively high volumes. As an example, the air might be dumped directly into the bypass duct. Other locations might be a turbine exhaust case or a core engine compartment.

Recently, gas turbine engines are operating at higher pressures and intense temperatures in the compressor sections. Thus, the dumped air is moving toward being higher pressure and temperature. Withstanding these pressures and temperatures is a challenge in an element such as a bypass duct, which is not designed to see high temperature.

Documents <CIT>, <CIT> and <CIT> disclose prior art gas turbine engines.

According to the present invention, there is provided a gas turbine engine as set forth in claim <NUM>. Embodiments are provided as set forth in claims <NUM> to <NUM>.

The fan section <NUM> drives air along a bypass flow path B in a bypass duct <NUM> defined within a nacelle <NUM>, and also drives air along a core flow path C for compression and communication into the combustor section <NUM> then expansion through the turbine section <NUM>.

The flight condition of <NUM> Mach and <NUM>,<NUM> ft (<NUM>,<NUM> meters), with the engine at its best fuel consumption - also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')" - is the industry standard parameter of lbm per hour of fuel being burned divided by lbf of thrust the engine produces at that minimum point. "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 °R = K x <NUM>/<NUM>).

<FIG> shows a compressor bleed valve system <NUM>. A bypass duct <NUM> is shown which may be similar to that in the engine of <FIG>. An upstream end <NUM> of an air oil cooler <NUM> takes in air from the bypass duct <NUM>.

A main compressor section <NUM> is illustrated upstream of a combustor <NUM> and a turbine section <NUM>.

A bleed valve <NUM> is shown with a control <NUM> for controlling a tap <NUM> from the main compressor section <NUM> and for tapping air to a line <NUM> leading to a dump. The main compressor section <NUM> includes a low pressure compressor and a high pressure compressor such as in the engine <NUM> of <FIG>. Tap <NUM> communicates with the high pressure compressor in one embodiment. The control <NUM> is programmed to open the valve <NUM> to dump air under certain conditions to maintain stability of the compressor section <NUM>. As an example, when the gas turbine associated with the bleed air valve system <NUM> is at an idle condition, or near an idle condition, the valve <NUM> will be open. As another example, when the gas turbine is commanded to accelerate at low power, or decelerate at high power, the valve <NUM> will be open. At other conditions, the valve <NUM> may be moved to be closed. Broadly, it could be said the valve <NUM> is opened at certain conditions but closed at others.

The control <NUM> may be a standalone control programmed to control the valve <NUM> utilizing techniques known to a worker of skill in this art, or alternatively, could be incorporated into a full authority digital electronic controller (FADEC) for the entire engine. In one embodiment it is the FADEC and is programmed to control the valve based upon any number of operational conditions such as ambient temperature, altitude, engine speeds, the status of other bleeds, etc. In general such controls are known.

The air leaves the line <NUM> at an outlet <NUM> into a flow <NUM>. Flow <NUM> communicates with the inlet <NUM>, and communicates through to an outlet <NUM>, wherein the combined flow from the inlet <NUM> and the dump outlet <NUM> reenter the bypass <NUM>.

As shown, a duct <NUM> for the air oil cooler receives both flows from the inlet <NUM> and the dump outlet <NUM>. A downstream end <NUM> of the duct <NUM> is illustrated and the air downstream of the dump outlet <NUM> will be at this end, which is downstream of the heat exchanger <NUM>. Discharge air from dump outlet <NUM> will mix with cooler flow <NUM> while following trajectory <NUM>.

Heat exchanger <NUM> may be an air oil cooler and is shown receiving oil from a component on the gas turbine engine such as a gearbox <NUM>. The oil to be cooled may also come from a generator <NUM>. Air from the bypass duct <NUM> passes into the inlet <NUM> to cool the oil in the heat exchanger <NUM>. The gearbox <NUM> communicates oil with heat exchanger <NUM> through a supply line <NUM> and a return line <NUM>.

It is known that the duct <NUM> and, in particular, its downstream locations <NUM> are designed to withstand very high temperatures. Thus, dumping the bleed air from the dump outlet <NUM> into the duct <NUM> at the location <NUM>, where it has been designed to withstand high temperatures, ensures that the bleed air is better accommodated than in the prior art which dumped the bleed air directly into the bypass duct. By careful design, outlet <NUM> can be oriented to keep the mixing flow trajectory <NUM> away from temperature sensitive region <NUM> of bypass duct <NUM>. While an air oil cooler is illustrated, other heat exchangers may benefit from this disclosure. In addition, other locations, which are designed to withstand temperatures higher than that typically seen in a bypass duct, may benefit from this disclosure and which could then communicate the bleed air into the bypass duct.

<FIG> shows a detail, wherein the line <NUM> communicates with the dump outlet <NUM>. As can be seen, the dump outlet <NUM> has a portion extending across the duct <NUM> at the downstream section <NUM>, downstream of the heat exchanger <NUM>. As can be seen, there are a plurality of outlet orifices <NUM> in the dump outlet <NUM>.

As shown in <FIG> shows an alternative dump outlet <NUM>' wherein a slot <NUM> replaces the several orifices <NUM>. As can be seen, line <NUM> now leads to a manifold <NUM> which sits radially outward of a radially outer wall <NUM> of the downstream section <NUM> of the duct. The actual dump outlet <NUM>' sits just inward of the outer wall <NUM> and has a slot <NUM>. It should be understood that the slot <NUM> could be utilized in the location of <FIG>, and the plurality of orifices from <FIG> could be in the location of <FIG>.

By spreading the air across the several orifices <NUM> or the slot <NUM>, the hot air from the outlet <NUM> will mix with the air downstream of the heat exchanger <NUM>, which may be hot, but will not be as hot as the air exiting the orifices <NUM> or slot <NUM>. The several orifices <NUM> or slot <NUM> spread the dumped air across a flow area of the duct. Downstream of the duct <NUM> the hottest portion of the dumped air is directed away from temperature sensitive region <NUM> of the bypass duct <NUM>.

As can be appreciated, the dump outlet <NUM> (or <NUM>') directs the dumped air in a direction with a component that is radially outward of an inner wall of the duct such that the hottest air avoids the temperature sensitive region <NUM> by being directed radially outwardly of an inner wall <NUM> of the bypass duct <NUM>.

A gas turbine engine according to this disclosure has a compressor section, a combustor, and a turbine section. A bleed tap taps air from the compressor section through a bleed valve. The bleed valve is selectively opened by a control to dump air from the compressor section to a dump outlet. A heat exchanger includes an air inlet to pass air through the heat exchanger to cool a fluid in the heat exchanger. A heat exchanger outlet in a heat exchanger duct connects the heat exchanger inlet and the heat exchanger outlet, and receives the heat exchanger. The dump outlet is within the heat exchanger duct. The heat exchanger duct is provided with structure to withstand relatively high temperatures. As an example, the heat exchanger duct may have a temperature limit of > <NUM>° F (<NUM>), wherein the bypass duct might have a limit of < <NUM>° F (<NUM>).

A gas turbine engine according to this disclosure could be said to have a compressor section, a combustor, and a turbine section. There is a bleed means for selectively tapping air from the compressor section to a dump outlet. A heat exchanger duct includes a duct air inlet to pass air through a heat exchanger to cool a fluid in the heat exchanger and a duct air outlet. The dump outlet is within the heat exchanger duct.

In one example, as much as <NUM>% of the air flow entering the compressor <NUM> may pass through the bleed valve <NUM>. The air can be on the level of about <NUM>°F (<NUM>) and <NUM> PSIA (<NUM> MPa).

Claim 1:
A gas turbine engine (<NUM>) comprising:
a compressor section (<NUM>), a combustor (<NUM>), and a turbine section (<NUM>);
a bleed tap (<NUM>) for tapping air from said compressor section (<NUM>) through a bleed valve (<NUM>), the bleed valve (<NUM>) selectively opened by a control (<NUM>) to dump air from the compressor section (<NUM>) to a dump outlet (<NUM>), wherein said control (<NUM>) is programmed to open said bleed air valve (<NUM>) when the gas turbine engine (<NUM>) is operating at at least one of an idle condition, or when said gas turbine engine is accelerating at lower power or decelerating at high power;
a heat exchanger duct (<NUM>) including a duct air inlet (<NUM>) to cool a fluid in a heat exchanger (<NUM>) and a duct air outlet (<NUM>), and said dump outlet (<NUM>) being within said heat exchanger duct (<NUM>); and
a fan positioned to selectively deliver air to said compressor (<NUM>), and also to deliver air into a bypass duct (<NUM>), wherein said duct air inlet (<NUM>) takes air from said bypass duct (<NUM>), and said duct air outlet (<NUM>) delivers air mixed from said duct air inlet (<NUM>) and from said dump outlet (<NUM>) back into said bypass duct (<NUM>);
wherein said dump outlet (<NUM>) is downstream of a downstream end of said heat exchanger (<NUM>), said dump outlet (<NUM>) is at a radially outer position within said heat exchanger duct (<NUM>), said dump outlet (<NUM>) includes a plurality of orifices or an elongated slot and sits inward of the radially outer wall (<NUM>) of the downstream section (<NUM>) of said heat exchanger duct (<NUM>) said heat exchanger duct (<NUM>) has a downstream end (<NUM>) provided with structure to withstand relatively high temperatures, and said dump outlet (<NUM>) directs air in a direction with a component which is radially outward relative to a rotational axis of the engine (<NUM>) such that the air is directed radially outwardly of an inner wall of the bypass duct (<NUM>).