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Airflow characterization of flexible ducts used by environmental control systems (ECS) of commercial airplanes (GLOBAL project with Shanghai Jaio Tong University)

Company: Boeing

Major(s):
Primary: ME
Secondary: ESC

Non-Disclosure Agreement: NO

Intellectual Property: NO

Flexible ducts/hoses are used throughout the commercial aircraft air distribution systems. ECS systems sizing needs accurate flow characterization of the flexible hoses to minimize the associated weight/cost/space and maximize the system performance. Many studies have proven that the pressure loss in bent flexible ducts is much higher than that in non-flexible ducts. Therefore, it is worthwhile to reduce the pressure loss in the ducting systems to provide better engineering solutions. This study is to systematically characterize the flow through flex hoses and enhance the predictive tools used for ECS system flow balance. There are associated risks involved such as oversized ECS fans/blowers/ducting causing overestimated power/weight/space requirements during design stages and result in unnecessary redesigns and subsequent system performance problems and, consequently, aircraft manufacturer’s added liability, less competitiveness, and increase operation cost for the customer airlines, just to name a few. In this study, experimental measurements to characterize the pressure drop in flexible ventilation ducts with different compression ratios and bending angles will be conducted. This investigation will first measure the pressure drop in straight flexible ducts with varied compression ratios under various airflow rates. The calculated friction factor for the straight flexible ducts was reported to be negatively associated with the compression ratio. Next, the pressure drops in single-bend flexible ducts with various bending angles from 30o to 150o will be measured under various airflow rates. The calculated loss coefficient of the bend should increase with the bending angle for single-bend flexible ducts. The database and empirical equations established from the experiments can be used in the assessment of the total pressure loss in the flexible ducting system in the ECS. In this study, the corresponding CFD simulations should be conducted and validated by their experimental counterparts. Finally, the deliverables should include: (1) A database of flow characteristics of flex hoses including most of the configurations installed in commercial airplanes; (2) A design guide on how to properly select and configure flex hoses used by ECS.