Engine bleed air system with waste gate valve for compressor surge management

A bleed air system for a gas turbine engine, the bleed air system comprising:

• a booster compressor for changing a pressure of airflow received from a main engine compressor section that is downstream of an engine fan to a pressure desired for a pneumatic system, wherein the booster compressor may operate at airflow conditions greater than a demand of the pneumatic system;
• a turbine coupled to drive the booster compressor, the turbine driven by airflow from the main engine compressor section;
• and
• an exhaust valve controlling airflow between an exhaust outlet of the booster compressor and an outlet passage to the pneumatic system, the exhaust valve disposed upstream of a junction combining airflow from the booster compressor and the turbine and is operable to exhaust airflow from the booster compressor in excess of the demand of the pneumatic system.

A method of controlling engine bleed airflow comprising:

• configuring a booster compressor to receive engine bleed air from a main compressor section of a gas turbine engine;
• compressing the engine bleed air from the main compressor section with the booster compressor and supplying compressed engine bleed air to a pneumatic system according to a demand of the pneumatic system;
• mixing airflow from a turbine driving the booster compressor with airflow from the booster compressor and exhausting excess airflow upstream of a junction combining airflow from the booster compressor and the turbine;
• and
• exhausting airflow in excess of the demand upstream of a junction combining airflow from the booster compressor and turbine through an exhaust valve such that the booster compressor operates at airflows exceeding the demand of the pneumatic system for at least one engine operating condition.