musing over ideas

[thecheat]

Ok, as far as I know (tell me if I'm wrong) but, a valveless PJ is currently the only motor that will run stationary, with no moving parts, right?

Now, I've got a question, would you be able to start a ramjet using purely the venturi effect? basically, applying a vacuum instead of a blower?

What's been tumbling through my head is a way to get a ramjet to work... without moving parts, or it moving. Basically a Valveless pulsejet without the pulse...

My idea would be, what if you put two Ramjets together? you put them their exhaust blows into a cylindrical enclosement, think of a piece of ducting (a/c) wrapped in a circle. occasionally you put a port to siphon off some of the gasses to keep the pressure stable.

Now, once you got the air moving in that circle, got some inertia going, would it be able to self sustain?



here are two pictures, (forgive the quality) of what the idea might look like.

PS: the blue is the "intake". Red is the exaust.
PLEASE add any ideas you have, I can try to explain something if anyone wants.

[Najm]

Well you would need a bit of outside energy to start that thing and a pulsejet extracts energy(it is something like this) from the previous cycle to start a new cycle, if you could do something like that in this engine than you could expect it to work.
Besides a ramjet is very inefficient when compared to a pulsejet in producing thrust.

[thecheat]

would it be a perpetual motion machine? you would be feeding this gas, which would ignite, and keep the machine moving, so, it's not moving by itself, but, with the help of combustion.

Also, my idea was that since ramjets become more efficient with airspeed, if you were able to get the air cycling, and pulling air through the ramjets at Mach or super sonic speeds, the engines should be more effective... in my theory... heh

Also, as a side thought, what would happen if you put a tesla valve in the tail of a Valveless PJ? it would stop the engine wouldn't it?

[tufty]

In a related note, I have a bridge that I need to sell :)

I think we've all come up with one of these at one point or another, and whilst in a ramjet application there appears to be no real reason it shouldn't at least provide a slight boost or extension to a ramjet's speed range, there is one major sticking point: Nobody appears to have ever produced any actual concrete evidence of one of these actually working.

Simon

[larry cottrill]

It's called a cyclical flow engine, and it's a perpetual motion machine. It is completely unworkable.

Ben, you know I always hate to disagree with you, but in this case I must.

The cyclical flow engine is NOT any kind of perpetual motion machine, in the usual sense of that term (a machine that keeps running without the addition of energy from an external source). The cyclical flow engine MUST produce a net momentum gain to work - exactly what a ramjet does - by means of addition and combustion of fuel.

The assimilation and compression of air costs LESS total gas momentum than the ejection of exhaust provides - therefore, you only tap off part of the exhaust stream to accomplish it, leaving some available for propulsion. There is nothing unworkable about doing that, in principle, as long as sufficient new energy is injected into the system.

Of course, getting it to actually work wouldn't be exactly easy, but it does not require anything beyond ordinary fluid mechanics principles to do so - no magic required, just good engineering.

L Cottrill

[Najm]

But what use would an engine be if it has a design like the one shown above?

For it to work, first air at high velocity will be needed to start the engine and only if air is moving through the ramjet at high speed then only the momentum of exhaust gases will be more than the momentum of intake gases, besides momentum is associated wth velocity, is it not? And we need force here to move the engine or whatever we want it to move.
Momentum=mass multiplied by velocity
And there is only a marginal increase in mass( due to addition of fuel in stoichiometric conditions) and air velocity also increases as well due to higher temperature in the exhaust phase.

There is nothing unworkable about doing that, in principle, as long as sufficient new energy is injected into the system.

That would be lot of energy. I think combustion of fuel only would not provide enough energy ........ mass addition is also necessary in the exhaust phase.

I may be wrong on some points here or maybe all points but please correct me if I'm wrong.
I just recently studied momentum( not gas momentum only momentum ), do same rules apply in gases as well?

[thecheat]

Ok, well (since nobody replied to my question of whether a VPJ would run with a tesla valve in the exaust... restricting flow back into the engine)

I decided something else that might make this viable.

What if I changed this around even more, making it even more twisted?

I added a PJ into the equation, NOW, a big problem with a PJ is it makes it much harder to put an afterburner on it because of the constant reversal of airflow in the system.

What if I put two tesla valves in the PJ tailpipe. One allows for the air to flow into the circle, one allows for air to flow into the tailpipe so the engine would run as normal.

Here's the idea behind this, if the air is only allowed to be pushed into the circle on the thrust cycle of the PJ (show as the red cylinder in the picture), it would keep the air in the circle moving at a relativly constant speed right? I'd assume that this would cause the circle to act as an inductor on a circuit, it keeps the current flowing. This would supply the venturi effect for the ramjet to be preforming optimally.

However, if it was left as such, I think the engine wouldn't work as the valve would screw the engine up on the pull cycle. but, if you had another Tesla valve stopping the air from exiting via that route (forcing it into the circle to keep the flow going) , but, it could enter through there to relieve the engine from coming to a halt, without PULLING from the circle stopping the flow. this is shown as the blue cylinder in the picture.

Afterburner for a PJ? one that runs off of completely fresh air?

[jthompso]

Here's the thing about Tesla valves--they really don't work all that well, they are an example of a theory that looks promising but just does not transfer well into reality. There have been a number of studies and experiments done on tesla valves and all have found them to be ineffective--they don't reduce reverse flow all that much. The highest reduction in flow rate that I've found for a tesla valve was 25%, and that was for water, the valves are even less efficient with a compressible medium like air. Bottom line is I wouldn't depend on a tesla valve for your design.