Air inlet system for auxiliary power units

An auxiliary power unit (APU) comprising:

• a load compressor providing compressed air to an aircraft;
• a core compressor in fluid flow communication with a combustor;
• an intake duct having a wall defining an inlet plenum providing a common air inlet for the load compressor and the core compressor;
• a splitter mounted in the intake duct, the splitter bifurcating the common air inlet between a load compressor inlet communicating with the load compressor and a core compressor inlet communicating with the core compressor;
• a deflector mounted in the intake duct and extending in the inlet plenum, the deflector configured to deflect at least a first airflow stream away from the core compressor inlet toward the load compressor inlet, the deflector extending at most to the splitter without extending in the load compressor inlet when viewed along a direction of a second airflow stream flowing through the intake duct from the common air inlet to the load compressor inlet;
• and
• an inlet screen mounted in the inlet plenum about a center axis of the APU, the deflector mounted radially outward of the inlet screen relative to the center axis of the APU.

A method for supplying air to an auxiliary power unit (APU), the comprising an air inlet system having:

• an intake duct having a wall defining an inlet plenum and forming an inlet opening configured to direct air into the inlet plenum;
• a load compressor passage having a load compressor inlet in fluid communication with the inlet plenum and leading to a load compressor of the APU;
• a core compressor passage having a core compressor inlet in fluid communication with the inlet plenum and leading to a core compressor of the APU;
• a deflector extending in the inlet plenum between the inlet opening and the core compressor inlet, wherein the deflector extends circumferentially between a first end and an opposed second end along an arc around a center axis of the APU, the method comprising:
• ingesting air through the inlet opening;
• directing a first airflow of the air toward the load compressor inlet;
• directing a second airflow of the air toward the core compressor inlet;
• and deflecting a portion of the second airflow away from the core compressor inlet toward the load compressor inlet.