Study on the Impact of Relative Position Arrangements of the Integrated Duct of APU on the Aerodynamic Performance of Inlet System

Auxiliary power unit (APU) of civil aircraft is mainly used to provide generator shaft power for the power supply system and bleed air for the air supply system. APU inhales air from the outside of the fuselage through the inlet duct and ventilation cooling duct, supplying the APU with the required airflow under various operating conditions and ensuring proper ventilation and cooling of the compartment, and meets the pressure loss and the inlet distortion requirements as small as possible at the APU's entrance. APU inlet duct and ventilation cooling duct can be integrated together (sharing one air intake port) or arranged separately. This paper uses the numerical simulation method to study the impact of the relative position of integrated duct on the aerodynamic performance of inlet system. The results show that within the study range, under the flight condition, the relative position arrangements of the duct have great influence on the aerodynamic performance of inlet system; Under ground condition, the relative position arrangements of the duct have little influence on the aerodynamic performance of inlet system.