Got my Turbo

[resosys]

Finally got a turbo. It's from a large diesel forklift and seems to be in pretty good shape.

More to come as the build progresses.

[Mike Everman]

Niiiiiice.
Nothing to add, but,
Niiiiice.

[resosys]

Fun. how are the bearings?

Don't forget the twenty seven million rule.

The bearings seem fine. No detectable play in either direction, and smooth when spun.

Word from the mechanic that gave me the unit is that the exhaust side bearing seal has a tiny leak, but other than that, it's in tip top shape.

Twenty seven million rule? Again? I keep forgetting that one... Must be all the beers.

[resosys]

Twenty seven million rule: Divide 27000000 by the circumference of the compressor wheel in mm. That gives you the max RPM. If you prefer english units, you can use the handy 1450 rule: keep your tip speed below 1450 feet per second and your TIT below 1450F.

Ahhh, yes. I've seen this in english units before. I'm starting to design the flame tube and housing. Good fun. Finally, a new project in the shop!

On the pulse combustor side of things, any thoughts on ways to achieve this? I've been pondering some shapes for the flame tube that may promote pulsing, but haven't hit on anything that seems feasible yet.


Chris

[Bruno Ogorelec]

To put it (much too) simply, what you need is to have the fresh air at high pressure imitate ambient air. You DON'T want to have the compressor simply blow into the pulsejet and the pulsejet to blow into the turbine.

So, what you want is two separate air boxes, each containing a pulsejet. The pulsejets have to be configured so that they blow in one direction only – meaning either U-shaped or with a flow rectifier up front. Each airbox has an intake orifice and the output orifice. The thing will look somewhat like an oldfashioned turbojet with can-type combustors, but having just two 'cans'.

It should not be a particularly loose ‘box’, either. In fact, I envisage something like a double-walled pulsejet, with air circulating freely through the space between the two walls. The relative volumes of the pulsejet and the surrounding chamber should be calculated so that the chamber section allows roughly the amount of air flow sufficient for both pulsejet combustion and the lowering of exhaust gas temperature to a tolerable level.

The compressor sucks ambient air and blows into the two airbox intake orifices through ducts. At the other side, ducts lead the hot-gas-and-fresh-air mixture from the airbox exhaust orifices into the turbine.

Compressor and turbine housings should each have two tangential ports instead of the usual one, and they should be diametrically opposed. (I presume you will be using a radial compressor and a radial turbine.) The two pulsating combustors must work out of phase and their inputs and outputs should provide something closely approaching a constant momentum at the compressor and turbine wheels.

[Bruno Ogorelec]

Ben, I beg to differ. You are right in describing the situation, but it has apparently led you to consider the turbocharger as a good turbine. It is good only for what it is designed to do -- squeeze some more work out of waste heat. As such, its efficiency is of relatively minor importance.

As a prime mover, it is not so good. If it can be improved with a new scroll, it is a fairly cheap and simple way of doing it. People have been casting parts of that complexity at home. I know one former member of this forum who did things like that for fun.

But, the scroll is not that important. One can combine the inputs of the two combustors before the untry into the turbine.

In basic terms, what is important is the construction of the combustor.

One of the reasons for the lack of success of the previous efforts to build a gas turbine with a pulsating combustor has been the effort to go too far, resulting in huge heat loading, distortion of parts, breakages etc.

We have to recognize the limits imposed by turbine technology. If you limit yourself to the fact that gas at the turbine inlet should not exceed 800 degrees C or so, it becomes obvious that the pulsating combustor will have to be of the bypass type. That is what I am saying with the ‘airbox’ layout.

It allows you to try to insulate the pulse combustor from the rest of the system acoustically. You can attempt to make your combustor resonant while keeping the rest of the turbine non-resonant.

[hinote]

On the pulse combustor side of things, any thoughts on ways to achieve this? I've been pondering some shapes for the flame tube that may promote pulsing, but haven't hit on anything that seems feasible yet.

Why re-invent the wheel, even here??

See the attached--it's the SNECMA pulsed combustor, recently revealed on the Valveless PJ Forum. It satisfies Bruno's parameter of having some bypass, too.

Bill H.
Acoustic Propulsion Concepts


".......some day soon we'll be flying airplanes powered by pulsejets."

[resosys]

Why re-invent the wheel, even here??

See the attached--it's the SNECMA pulsed combustor, recently revealed on the Valveless PJ Forum. It satisfies Bruno's parameter of having some bypass, too.

Nice. I certainly don't want to reinvent the wheel. This drawing has all the elements I was trying to put together, and coul be made adjustable as well, making tuning less of a pain.

Thanks.

Chris

[Bruno Ogorelec]

I seem to be the only one not understanding this device.

[larry cottrill]

Chris -

There was some discussion on this very design [the basic engine with all the outer stuff stripped away] recently on the Valveless Forum:
http://www.pulse-jets.com/phpbb2/viewto ... highlight=

It's a very interesting engine in a couple of ways: annular breathing tube around the tailpipe, tailpipe 'broken' for augmentation, etc.

L Cottrill

[Bruno Ogorelec]

Chris -

There was some discussion on this very design [the basic engine with all the outer stuff stripped away] recently on the Valveless Forum:
http://www.pulse-jets.com/phpbb2/viewto ... highlight=

It's a very interesting engine in a couple of ways: annular breathing tube around the tailpipe, tailpipe 'broken' for augmentation, etc.

L Cottrill

I understand how the core is supposed to work but don't quite get the two concentric mantles.

[hinote]

I understand how the core is supposed to work but don't quite get the two concentric mantles.

The way I see it, the outer one is the "can", closed at one end.

The inner one is sort of a secondary augmentor, allowing excess air to flow around the primary PJ combustor/augmentor assembly.

Anybody have another idea?

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[hinote]

On the pulse combustor side of things, any thoughts on ways to achieve this? I've been pondering some shapes for the flame tube that may promote pulsing, but haven't hit on anything that seems feasible yet.

Also, did you see this? (The red arrow points at the PJ combustor).

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[Bruno Ogorelec]

Also, did you see this?

Nope, I only saw this one.

[Bruno Ogorelec]

Interesting. Bill, do you see how your SNECMA picture shows a layout that's closer to what I am proposing than the earlier one on my SNECMA picture? This encourages me. My 'airbox' idea isn't totally stupid then. This thing employs just that. Fresh air is compressed into a box. It flows all around the pulse combustor, with a fair amount of bypass. The combustor is not in the direct line of the flow. It is like a stationary pulsejet, only the air pressure is much higher.