US Patent 9027353 Gas turbine engine buffer system

A gas turbine engine includes a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor, a fan section configured to be driven by the turbine section via a geared architecture, and a buffer system that communicates buffer air to a portion of the gas turbine engine. The buffer system includes a first circuit configured to selectively mix a first bleed air supply having a first pressure and a second bleed air supply having a second pressure that is greater than the first pressure to provide a first buffer supply air having an intermediate pressure compared to the first pressure and the second pressure.