This application relates to providing cooling air from a low pressure compressor to downstream locations in need of cooling.
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as propulsion air and further providing air into a core housing. Air in the core housing passes into a compressor where it is compressed and then 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 is known, turbine components are exposed to very high temperatures and thus cooling air has been typically provided to those components. Historically, the fan and a low pressure compressor have rotated as a single unit along with a low pressure, or fan drive, turbine. However, more recently, a gear reduction has been placed between the fan rotor and the fan drive turbine. This allows the fan rotor to rotate at slower speeds and the fan drive turbine to rotate at faster speeds. This raises challenges on the turbine components and requires more efficient provision of the cooling air.
At the same time, the overall pressure ratio provided by the compressor has increased. Historically, the air to cool the turbine components has been tapped from a location downstream of a highest pressure location on the compressor. However, with the increase in overall pressure ratio, this air has become hotter. In addition, utilizing this fully compressed air is costly to the efficiency of the engine.