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It looks like a second fan or something. enter image description here

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  • $\begingroup$ As a matter of phrasing, the fact that you aren't sure what something is doesn't make it strange. :) These are present on many (most) turbofan designs and have been for decades! $\endgroup$ – egid Sep 4 '15 at 18:04
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Those are Outlet Guide Vanes / Fan Exit Guide Vanes. They prevent the flow (bypass flow in this case) from rotating. The these vanes do not rotate, they are fixed to the housing. They also provide structural support.

Because there is no energy lost on the rotation of the flow the efficiency is increased.

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    $\begingroup$ Indeed they are present on the GE 787 engine also of course. bloomberg.com/news/articles/2013-11-25/… $\endgroup$ – Greg Hewgill Sep 3 '15 at 22:12
  • $\begingroup$ Sorry I reviewed the pic it did actually have outlet guide vanes. My apology. $\endgroup$ – Ethan Sep 3 '15 at 22:21
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    $\begingroup$ @Ethan: How engines are assembled by Rolls Royce, a good documentary on the Trent 1000 with many details on what is inside the casing, and for sure many (good) questions :-) $\endgroup$ – mins Sep 3 '15 at 23:27
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    $\begingroup$ The exit vanes also extract a little amount of thrust from the flow by converting some of the rotational energy into a forward force on the vanes. $\endgroup$ – Peter Kämpf Sep 4 '15 at 11:21
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    $\begingroup$ @PeterKämpf That is indeed how the recuperated energy manifests itself. $\endgroup$ – DeltaLima Sep 4 '15 at 11:26

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