Numerical Simulation and Wind Tunnel Test of a Variable Geometry Auxiliary Inlet for a Wide-Body Aircraft Environmental Control System  
[PERSON]  
1 Key Laboratory of Aircraft Environmental Control and Life Support, MIIT, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; [EMAIL_ADDRESS] (Z.L. ); [PERSON]S] (Y.J.) [PERSON]  
2 China Shipbuilding Power Engineering Institute Co., Ltd., Shanghai 201208, China; [EMAIL_ADDRESS] 2  
[PERSON]  
1 Key Laboratory of Aircraft Environmental Control and Life Support, MIIT, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; [EMAIL_ADDRESS] (Z.L. ); [PERSON]S] (Y.J.) [PERSON]  
3 Environment Control and Oxygen System Department, Shanghai Aircraft Design and Research Institute, Shanghai 201210, China 3  
Correspondence: [PERSON]MAIL_ADDRESS]; Tel: +86-181173961323  
fluid dynamics (CFD) has developed rapidly and been applied in various domains [18; 19; 20; 21; 22]. Some scholars have studied the flow field characteristics of a submerged inlet and the influence of geometric parameters on their performance by CFD methods [23]. Furthermore, combined with an intelligent optimization algorithm, geometric parameters of the submerged inlet are optimized to improve its performance [24; 25; 26]. For a civil aircraft environmental control system, it must be guaranteed to work normally throughout the whole flight envelope. The submerged inlet mainly relies on the ram effect of the high-speed air flow for inspiration. As a result, the mass flow rate is greatly affected by flight conditions and environmental parameters. In this case, the fixed inlet configuration cannot adjust the flow according to the flight state and environmental parameters, thus affecting the stability and economy of civil aircraft environmental control systems. With the increasing demand for flow of the wide-body aircraft, this contradiction becomes more pronounced. A variable geometry auxiliary inlet may be an efficient way to solve this problem. At present, the research on variable geometry inlets mainly focuses on hypersonic aircraft, which are used to meet the high efficiency at wide Mach number. [PERSON] et al. [27] numerically studied a variable geometry inlet control for hypersonic aircraft. The moveable lip cover of the variable geometry inlet for hypersonic aircraft is a lip cover which can move forward and backward in the direction of the incoming flow and achieve the maximum airflow capture of the aircraft and improve the performance of the propulsion system. [PERSON] et al. [28] designed three types of two-dimensional variable supersonic inlets and analyzed the performance by 2D numerical simulation. In order to meet the operating requirement of ramjets in a wide speed range, [PERSON] [29] designed a variable geometry inlet with integrated internal/external compression regulation, and the feasibility of a three-dimensional bleed control method with a vent hole on the side plate is verified by 3D numerical simulation. Although a series of research achievements have been made in the design and performance research of submerged inlets, they are mainly carried out for inlets with fixed geometric configuration. The study of variable geometry inlets is mainly focused on hypersonic vehicles and meets the performance requirements at both high and low Mach numbers. The speed of civil aircraft is low, and the emphasis is on flow control, so the above research results cannot be directly copied. Based on previous research, a variable geometry auxiliary inlet is proposed to enhance the stability of the environmental control system of civil aircraft. Furthermore, to verify the feasibility of the inlet, detailed numerical simulations and wind tunnel tests are conducted. By analyzing the flow field characteristics, regulation laws, and performance changes at different conditions, valuable conclusions are obtained, which provide useful references for the design of environmental control systems for large aircraft.