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In turbojet engines, does the fan play a key role in the air intake to the inlet?

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    $\begingroup$ Welcome to the site! I don't understand your question, what do mean by key role? $\endgroup$ – GdD Feb 17 '19 at 12:45
  • $\begingroup$ In all three types of engines, compression turbines increase the air density in preparation for combustion. Turbofan engines are the only ones in which the turbine portion has an additional blade extension in the front beyond the combustion chamber to increase thrust. $\endgroup$ – Ryan Mortensen Feb 17 '19 at 20:24
  • $\begingroup$ My question to you is, do you have a basic understanding of the different of the three engines and their construction and operation? This question seems to be too obvious. Actually, turboprop engines only have compressor blades, not fans. $\endgroup$ – Ryan Mortensen Feb 17 '19 at 20:25
  • $\begingroup$ Hi GdD. What i meant by key role was does it actually play a part in the intake of air to the engine. Because for a turbojet engine without a fan how can air be absorbed to the inlet. My understanding is that for an inlet to exist there has to be a fan to absorb air towards it. Am i right in thinking this way? $\endgroup$ – Harinda Feb 18 '19 at 9:32
  • $\begingroup$ Hi Ryan. I do have a basic understanding about the three types of engines. But there is a loop hole in my understanding. I have a misunderstanding about the inlet. Does it consist with a fan? If not how does the inlet absorb air toward it? $\endgroup$ – Harinda Feb 18 '19 at 9:35
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In turbojet there is no fan. Very simply, turbofan means turbojet + fan in front connected to the LP shaft.

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Further, nothing about a turbofan or turboprop requires the fan/prop on the front. It absolutely can be set up in pusher mode, with the prop or fan behind the engine, and turbine exhaust being diffused into the fan input. If anything, this is easier, because it means the prop/fan is on the same end of the engine as the second stage (low pressure) compressor, so there's no need for that shaft to run all the way through the engine. Thus reducing the need for concentric shafts.

So in that case, the engine core will input air the same way a turbojet does. There may be a second input for bypass air.

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