Pulse jets and ram jets as part of my course on jet propulsion

[banerjeerupak]

i was reading about pulse jets and ram jets as part of my course on jet propulsion. all i was told was that they are aero-thermo-dynamic-ducts.

couldn't understand what they mean. checked google, but the articles i got were vague.

could someone explain what aero-thermo-dynamic-ducts are?

 

[Danger]

I've never heard that term. Going by the words involved, it should simply mean that it's a tube of some sort in which work is extracted from hot air.

 

[banerjeerupak]

then could you tell me if that is the way in which pulse jets and ram jets work?

 

[Danger]

I'm not the expert here; Fred Garvin, Russ Watters, Rainman Aero, Astronuc, and a few others know far more than I could ever learn. I'm sure that one or more of them will weigh in before long.
That having been said, the basic answer is 'yes'.
Both types of engines ingest air without the aid of a compressor system, mix it with fuel, burn the mix, and expel the exhaust to provide thrust. The difference is that a pulse jet uses a valve box at the front, or a carefully tuned tube, to prevent the exhaust from going that way, which opens for intake and closes for combustion. That cyclic open/close/boom is why it pulses. A ramjet carries out continuous combustion, but it has to be moving at something on the order of 400mph to work.
By the way, if you're taking a course on this, shouldn't they be teaching you how they work?

 

[russ_watters]

I've never heard the term either, but what it implies to me is that both aerodynamic and thermodynamic principles are at work. Sounds reasonable, but yes, vague...

 

[FredGarvin]

I am assuming, by the description, that the original term was meant to mean that in both ramjets and pulse jets, there are no rotating components. Hence the "ducts" reference because they are really just tubes doing the work.

Aerothermodynamics is the general area of study for the components and systems in turbomachinery (usually high speeds).

According to this web site, aerothermodynamic duct was coined by the Brits for a ram jet.

http://www.onera.fr/conferences-en/ramjet-scramjet-pde/