| 摘要 |
Within a turbine engine a heat exchanger may be provided to cool compressor air flows to be utilized for cabin ventilation or other functions. A fluid flow acting as a coolant for the heat exchanger is generally drawn from the by-pass duct of the engine and a dedicated outlet duct is provided such that the exhausted fluid flow from the heat exchanger is delivered along the conduit duct to a low pressure region. In such circumstances, an appropriate pressure differential across the heat exchanger is maintained for operational efficiency when required, whilst the exhausted fluid flow is isolated and does not compromise the usual engine ventilation vent exit area sizing. Over-sized ventilation vents would create an aerodynamic step and therefore drag upon the thrust of the engine. Typically, the outlet end of the outlet duct has a variable geometry to enable adjustment in the pressure differential across the heat exchanger such that an air fan valve used to control flow rate through the heat exchanger may not be required.
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