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Bellmouth Compressor Inlets

Bellmouth Compressor Inlets

  • A bellmouth inlet is usually installed on an engine undergoing testing in a test cell. It is generally
  • equipped with probes that, with the use of instruments, can measure intake temperature and pressure (total and static).
  •  During testing, it is important that the outside static air is allowed to flow into the engine with as little resistance as possible.
  • The bellmouth is attached to the movable part of the test stand and moves with the engine. The thrust stand is made up of two components, one nonmoving and one moving.
  • This is so the moving component can push against a load cell and measure thrust during the testing
  • of the engine. The bellmouth is designed with the single objective of obtaining very high aerodynamic efficiency.
  •  Essentially, the inlet is a bell-shaped funnel having carefully rounded shoulders which offer practically no air resistance.
  • Duct loss is so slight that it is considered zero.
  • The engine can, therefore, be operated without the complications resulting from losses common to an installed aircraft inlet duct. Engine performance data, such as rated thrust and thrust specific fuel consumption, are obtained while using a bellmouth inlet. Usually, the inlets are fitted with protective screening.
  •  In this case, the efficiency lost as the air passes through the screen must be taken into account
  • when very accurate engine data are necessary.


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