In this paper an exercise to introduce intercooling in a high bypass civil turbofan is outlined. The engine selected as the basic propulsion system is a three spool high bypass turbofan with a bypass ratio 6.4. The air leaving the IP compressor is cooled in the bypass duct prior to entering the HP compressor.

This preliminary investigation appears to indicate that the main benefit to be gained is an increase in the net thrust from the engine without increasing the turbine inlet temperature. To keep engine diameter constant, the bypass ratio has not been changed. This results in a requirement to significantly increase the pressure ratio to reduce the SFC levels to an acceptable value.

A sizing exercise has been carried out to understand the weight and volume penalties imposed by heat pipe intercooling hardware. The preliminary sizing exercise indicates that the weight penalty is very large. The performance of the aircraft using the intercooled engines is also investigated and some improvements in performance are predicted.

Overall this investigation is considered to be positive so that further investigations should be considered. It appears that an intercooled engine can produce a somewhat higher thrust at a given turbine entry temperature at similar SFC levels of current engines, or, if a small increase in SFC is acceptable, the increase in thrust is quite important.

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