Forum: Technology

I've heard this from class but I'm not sure if it would be true or not so I want to ask people who would know best. I've heard that the cones on the end of the engine shaft are shaped in a such a way that as to be more efficient. They are grooved or vained (I'm not sure of the proper term) that pushes the air out of the way of the shaft more and into the compressor more efficiently. I've also heard they this causes the engines to make a horrible screeching sound which is why it's not used on commercial aircraft. I'm just curious if any of this is accurate if I'm once again being led on by my profs.

I'm speaking from INexperience here so please bear with me through stupid questions.

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The nose cone in the forward section of the IGV's or 1st stage fan have a three fold purpose. The first is to direct shock waves from entering the compressor. The second is to simply direct airflow onto the IGV's or 1st stage fan uniformly and to prevent turbulent flow, because that is what would happen if a sharp or curved nose cone were not there. Third, it is a convienent place for ice to build-up instead of onto the IGV's or fan-blades. Some nose cones are equipped with rubber tips, that lead to a small amount of ice building up rather than a large one. It will bend and break ice build-up off of the tip as the rotation of the ice builds inertia. The Aerospace ingenuity of this company does not stop at this level, for they have implemented many other incredible ideas for jet engines be it a turbojet/turbofan. Turbo-jets are rare today.

Aft covers on the turbine section simply serve as a cover or fairing to prevent extreme turbulent flow. Some turbulent flow does exist but is considered to be a virtually non-existent as far as aerodynamics in the exhaust and afterburner sections if so equipped.

Engine inlets are the culprits that make noise, not the cones, and by the way, they are not vaned, this would cause a tremendous airflow disturbance.

I am curious, what is your major and what text are you using for your class?

I'm a junior (now for fall semester) at Purdue University in Aeronautical and Astronautical Engineering. I heard it in my basic aerospace design class (sophomore year). It was very basic and it seemed to make sense at the time but that's why I asked the question. The text we used for the class (I lost it, that hurts with college textbooks) was "Introduction to Aerospace: A Design Perspective". It's by Brandt, Stiles, Bertin, and Whitford. I think my prof mentioned it in class but I certainly was sure about it. His research has nothing to do with engines, but I digress. I haven't had a propulsion class yet, just a basic design class. I've always wanted to stick my head in a fighters engine but this isn't exactly allowed at airshows Very Happy

. Is there anything that can be done before the fan to help it? Make the inlet some sort of diffuser or nozzle to help? I'm just curious.

Thank you for the response.

Of course, the converging/diverging inlet and/or ramp/intake lip is designed to keep supersonic flow subsonic along with the cone. In the case of a transport inlet, even they have a slightly diffusing inlet whose purpose is to prevent supersonic flow from entering the first stage fan again along with the inlet cone. They're are threads with inlets posted, try to do a search for the "F-105 inlet plug", the F-105, a century series fighter, a complex, kickin' fighter will give you an idea for the converging/diverging inlets of supersonic inlets.

Stay in touch and keep posting.

Forum: Technology

Vained Cones on Turbojet/fan engines