Tesla Ramjet?

[Irvine.J]

A mate and I were discussing the Valve conduit and its applications recently, and we both wondered if anyones ever tried something like this, (Very crude drawing but we are SURE you will get the idea). Basically, it might eliminate the need all together for any sort of valve plate, or centre conical flameholder, but might require another conduit section in the centre to contain flame creeping foward? If it eliminated the need for any centreline obstruction that has to be a bonus.
Anyway, just wondering if its been "Tried", thought about, or discussed before? Yes its a crude drawning! :P Note the drawing of conduit is in reverse to the airflow of the ramjet. I've noticed some have tried on Pj's, but not yet on ramjets.

[Rufus]

Short answer number 1:
You don't seem to have a good undestanding of how ramjets work.

Short answer number 2:
Things similar to this have been attempted in valveless pulse jets.

[larry cottrill]

Number47 -

This used to be discussed at length on the old forums, and definitely does belong in the 'Valveless' category. Its ability to transition to ramjet operation (without MAJOR experimental revision) is doubtful.

Below is my own version (which I naturally consider vastly superior ;-)

L Cottrill

[Irvine.J]

Short reply 1:
Rufus, I wasn't asking "how is my understanding of ramjets" it was a broad question of "Has it been considered or discussed"... and like all people levels of understanding come with time... Perhaps you could tell my why (specifically) it wouldn't work using the return flow of gas to basically become its own flame holder?...
Short reply 2:
I said that in whats written above, hence asking has anyone tried to apply it to ramjets.

Larry, Brilliant, thanks again for an excellent and thoughtful reply. Vastly superior... wouldn't doubt it for a second ;-)

[larry cottrill]

Number47 -

A couple more comments:

The Tesla Valve idea is good only for very short pulses. If a pulse lasts too long, the side channels become stagnant, and the outward flow proceeds via the wobbly path down the center, as if the fancy channels didn't exist. The volume of the channels needs to be "tuned" to the expected blast flow duration to make it work as a "flow rectifier". And, like all such attempts, it will never work 100 percent, no matter what you do.

One real problem with us amateur designers is not really appreciating the nature and importance of the diffuser. This makes us too willing to mess with it. In general, anything that "complicates" the diffuser section will produce degraded performance. What we need to remember is that the diffuser is (my opinion here) BY FAR the most important element of the ramjet design!

Why would I say such a thing? Here's why:

The diffuser is the device which produces the ENTIRE OPERATING PRESSURE of your engine. Period. In the turbojet, you have hundreds of whirling blades; in the pulsejet, you have a low-level suction in a large volume that can suck in an "overcharge" of new air - but in the ramjet, all you have is what you can wring out of the incoming air by smoothly slowing it to a crawl with that simple cone. What you get is an increase in pressure, density and temperature, with the velocity magically reduced to a speed that will work in the combustion section. Nothing else will do - whatever you do, you must not screw that up!

This is basically why a pulse/ram transition engine is so blasted difficult: To make a good valveless pulsejet, you MUST modify the front end in some meaningful way; to keep a good ramjet, you MUST NOT !!! Of course, it's not totally impossible; Messerscmitt figured out one good way of going about it. But that's probably not something you or I would want to build.

As usual, if it was easy, everyone would be doing it ...

L Cottrill

[Irvine.J]

Excellent thanks for the answers Ben and Larry, I appreciate the time and effort involved, it is very informative. As I said earlier it was a discussion I had with a mate that we both thought would be worth asking, I genuinely want to learn as much as possible, i'm not here to waste your time. Thanks very much again.
47.

[thecheat]

actually, I had the same idea, but stamped it down. I remember the tests of this on a PJ were not good as all those vanes trapped exaust, which, starved the PJ of air, and... well you get the picture!

Larry, one question, shouldn't the "vanes" be tilted more towards the center axis to catch more air trying to rush back out?

PS: now if only one of us could telekeneticly ram the air through... "your powers are weak old man" (actually I'm kinda young...) Dang. ;-)