DESIGN, DEVELOPMENT, SIMULATION AND REALIZATION OFudEXPANSION JOINTS IN ECS ENGINE BLEED SYSTEM FORudA TYPICAL LIGHT TRANSPORT AIRCRAFT

摘要

In a commercial aircraft, ventilation to the cabin is normally through environmental control system normal bleedudair system, ECS emergency back-up pressurization system and ram air. Bleed air is primarily used to provideudpressurization by supplying air to the environmental control system. Additionally, bleed air is used for de-icing ofudaircraft leading edges. The bleed air needs to be tapped from engine and conveyed to the ECS pack through pipe routings.udThe bleed air pipes that tap the air from engine would experience a varying pressure load (as high as 140psi) and varyingudtemperature (as high as 340°C) at different segments. This would obviously produce the expansion/ contraction of pipesudwhich will result in axial moment and swaying of pipelines from their nominal configuration. These movements should beudcompensated by means of providing suitable expansion joints/thermal compensators to avoid undesirable loads at theudsupport points which may affect the overall functioning of the system. The real challenge lies in designing such a complexudsystem where suitable expansion joints need to be provided within stipulated airframe configuration satisfying theudinstallation requirements, yet cost and weight effective. In the present work, a methodology has been developed for designudof ECS pipe routings, using flexible hose- metallic bellows as a thermal compensator, with the aid of finite elementudanalysis. This paper also talks about the qualification of the bellows through acceptance tests and implementation on audtypical light transport aircraft.