# The Airgulper concept

1. Mar 10, 2008

### charioteer

Please give some feedback on my latest drawing concept of 'injecting air into a tank instead of compressing it'. Thanks. http://darinselby.1hwy.com/airgulper.html [Broken]

Last edited by a moderator: May 3, 2017
2. Mar 10, 2008

### Danger

Welcome to PF, Charioteer.
We've already dealt with that concept here. Unless there's something seriously missing from the design, it would be considered an over-unity device (perpetual motion), and is thus not functional.
While I can't remember what thread or even what sub-forum it was in, I know that I've seen that diagram before.

3. Mar 10, 2008

### charioteer

Use injection instead of compression to get air into a tank more efficiently.

'Danger', you obviously have not looked at the drawing, because it is not about trying to create overunity. http://darinselby.1hwy.com/airgulper.html [Broken]

Last edited by a moderator: May 3, 2017
4. Mar 10, 2008

### Q_Goest

Hey Darin. That Skedaddlethingy cracks me up. At least that’ll work!

But as for the air gulper, … well.

Let me guess. You don’t know what the Bernoulli equation is do you? Nor how to calculate any of this. But that’s ok, I don’t know how to drive a Skedaddlehopper.

Here’s the scoop. You have “tank pressure in”. That air expands, increasing velocity in order to reduce the static pressure. That lower static pressure is intended to draw air in from outside, where it is accelerated in the flow stream and discharged back into the tank.

I’ve left off your valves for a reason.

The above device is called an eductor. It won’t work the way it’s described and the way it’s shown in your diagram because the (stagnation) driving pressure must be above the (stagnation) discharge pressure due to the transfer of some of the kinetic energy and momentum from the high pressure jet which is used to accelerate the low pressure air source. That energy can’t be recovered, so assuming you have a perfect diffuser (which, by the way, isn’t shaped like a Nautilus seashell, it’s shapped like a gradually expanding cone with a roughly 7 degree included angle) the STAGNATION pressure MUST be lower. The stagnation pressure can never get back up to the same pressure as the high pressure tank. Even if both the driving nozzle and the diffuser were perfecty isentropic, which it can’t be, the final stagnation pressure is lower. It just won’t work…

Of course, I haven’t mentioned your valves yet.

~

Ok, now the valves...

Problem with the valves is they can’t increase the energy of anything without energy input. In fact, they only decrease the efficiency of the perfect eductor because there’s an irreversible pressure drop across the valve. Flow across a valve is called an “isenthalpic” process. It is not isentropic. I realize that doesn’t mean anything to you. What it means however, is the valves reduce the available energy. By adding valves, you can only reduce the effectiveness of your device which won’t work to begin with.

By the way, the web site you point to that uses a very similar device and is run by Scott Robertson and/or Donald Robertson is seriously missleading, and might possibly (still) be considered fraudulent. Looks like he cleaned it up just a little bit since the last I saw it a few years ago, removing some of the most flagrent lies.

Must have been those internet police from the BBB.

I wonder who sicked them on that hapless site?

Still, I’d suggest you not give any of those Robertson folks a ride in your Skeddadlehopper. Give them a wide berth and keep your unpressurized tires rolling on solid ground. Enjoy.

Last edited: Mar 10, 2008
5. Mar 16, 2008

### Danger

Jeez, Q, I think that you discouraged him. You big bully...

6. Mar 16, 2008

### Q_Goest

Who, me? A bully?

never thought of myself as a bully before...

Maybe I should take an anger management class.

7. Mar 16, 2008