Augmentor thrust increasements

[Bruno Ogorelec]

Sorry, a lapse of an old and tired brain. Not California.

Foa Engineering
11319 Commonwealth Drive, #101
North Bethesda, MD 20852
Joseph V. Foa 301-468-3926

[leo]

Mike, I am no scientist. I'm a college dropout turned political analyst

I was thinking you replied to my/Leo’s post

Sorry, a lapse of an old and tired brain.

I get that to sometimes, already 46 years old times flies by.

[alex]

Thanks guys, and a special thanks to Larry!

I don't want to criticize your theory, but. As I've understood it the outmoving air has to change direction, and this "decision" is made my the air moving backwards which directs it into its own direction.

But, doesn't this mean that the air moving out toward the pipe wall slow down the air moving backwards?

[Mike Everman]

Hi Bruno,
I too know little solid, other than it works, and it's pretty easy to get some results. A good experiment to do is to do a straight pipe with no flare. What surface would push forward? I'd say that would tell us the contribution of mass flow effect only. Put the lip on, and you get a surface to take advantage of the low pressure component of drawing air across the lip.

I'm scouring for the reference, but there was a good one that related the mouth diameter to the diameter of the vortices coming out, and the divergence to the divergence of the vortex, or maybe that's what I wrote in the margin.. ;D)

It's interesting to think that a divergent augmenter would take best advantaage of the emergent vortex, as the outside of the "donut" is going much slower, as it rotates to the rear. One can even imagine the outside of the vortex being faaaaaascinatingly close to stagnation, while the inside is going exhaust velocity. So, the divergent wall gets a higher pressure against it's walls.

By the same logic, there may be some advantage to a centerbody with the point toward our exhaust as well! That would take advantage of the inside of the vortex, and "draw" the centerbody forward. The disadvantage I see there is the increased surface area drag on the exhaust.

[leo]

I think the basic of augmentation is as follows.

Presume we have two gas masses.

One standing still (the air), with a mass of 1.

And one moving(the exhaust gasses) also with a mass of 1.

The still standing air has no motion energy.

The moving exhaust gasses has motion energy, lets say speed 100.

The energy of moving things = Velocity*velocity*mass = in this case 10000.

When the two masses merge in the augmentor the get halve the speed (the centre of gravity always stays the same if masses interact (a nature law))

Then the speed is 50 and the mass is 2 then the energy = 50*50*2 = 5000.

This is only halve the energy before the mixing (augmention).

Where stays the other halve?, this is changed to heat, heat gives pressure, pressure gives trust.

So the heating in the augmentor comes from the largest part trough mixing of 2 gases with different speeds and not from the hot exhaust gas.(a small part of the heating has to do with the difference in K value).

This of course is only the basics, in reality especially with pulsating, flows its much more complicated.

As a note, I only learned for car mechanic, but work in machine building and testing for a long time now. So I never learned this thing in school, so I could be completely wrong.

Edit; all the results has to be divided by 2, but this will not change my point.