Turboshaft?

[elventu]

I'm trying to put on paper an idea for the flame tube and combustion chamber.
I'm wondering if it is a functional idea to do a single piece flame tube closed at the top with a welded semi-round "cup" I found as standard pipe end, to allow primary air coming even from the top of the flame tube instead of having the top flange sealed.
Maybe this allows me to have a better fuel/air mixing?

In my mind I have to do the flame tube with the semi-round top on one side, and with the conical reduction to the turbine flange at the opposite side.
With this design I can have half of the conical part in the combustion chamber and half on the outside, this allows me to have the right space to bolt the combustion chamber​ to the turbine casing and to connect the air inlet to the lower part, where the conical part give more room to the incoming air to reach the combustion chamber.
The external part of the combustion chamber will be bolted to the flange welded at half the conical part.

On the top I want to weld a flange for the fuel inlet and spark plug.

It is a good idea?

I'm also wondering if for me it is better to use liquid LPG, since I want to use a small cylinder, that haven't enough surface area to evaporate the liquid gas in it.
If it is a viable option, what design I have to do for the injector nozzle, or maybe I need a small evaporator in the combustion chamber...?

[racket]

Yes you'll need a "heat exchanger" within the flametube for the liquid propane to change into gaseous propane and be distributed evenly across the flametube .

A largish tube , maybe 20 mm dia , with its end sealed , into which the liquid propane is squirted at the "bottom", there being a ring of distribution holes in the 20 mm tube at the "top" that the gaseous fuel exits

[elventu]

Thank you John!
Thinking about the material I have in my garage, I started designing it from a piece of diameter 33.7mm long about 50mm that I already have.

And about the shape I wondering to give to the top of the combustion chamber?

[elventu]

I hope the link works!
photos.app.goo.gl/B38F8oeXmbC7fTvw5

[racket]

Hi Davide

It will need to be longer and extend "deeper" into the flametube I feel , a smaller diameter tube needs to deliver the liquid propane to the "bottom" of the evaporator , the gap between the inner tube and outer evaporator tube needs to be relatively small so that the liquid propane is forced into contact with the outer wall , a short fat evaporator might allow liquid propane to be injected in an uneven manner into the flametube resulting in uneven combustion

Cheers
John

[elventu]

Thank you!
Maybe I have some 16mm and 20mm tube, I can use the 16mm on the inside and the 20mm on the outside, leaving a ~1mm space between them, to ensure the total evaporation, I'm right?
However, as I said, I want to do this first build with a small turbine, it is a KKK K26, to do some "practice".
The fuel flow are not too high.

I'm also thinking about liquid fuel.
Unfortunately I find that in my actual region seems to be difficult and costly to find kerosine, when I was in the alpine region it is more simple.
However kerosine is so costly, for 20liters I paid over 50€, maybe LPG is a more viable option (~30€/20liters for the gas sold in cylinders).
I think diesel fuel is too thick for a small engine, I'm right?

Maybe I can imagine because this hobby isn't so popular in Italy 😂

Nov 13, 2018 16:05:23 GMT -5 racket said:

Hi Davide

It will need to be longer and extend "deeper" into the flametube I feel , a smaller diameter tube needs to deliver the liquid propane to the "bottom" of the evaporator , the gap between the inner tube and outer evaporator tube needs to be relatively small so that the liquid propane is forced into contact with the outer wall , a short fat evaporator might allow liquid propane to be injected in an uneven manner into the flametube resulting in uneven combustion

Cheers
John

[racket]

Hi Davide

You can mix diesel with petrol to thin it down , I'm currently running 2 parts petrol to one part kero in my 12/118 engine, it certainly keeps my costs down as well as making it easier to fuel up my engine .

Cheers
John

[elventu]

John, did you mean 2part petrol with 1part diesel?

66% petrol 33%diesel?

It isn't too flamable?

[racket]

Hi Davide

Yes 66% petrol with 33% diesel , it makes a "brew" similar to JP3 jet fuel .

I've had no problems in my 12/118 , the only concerns are that there are more volatiles from the petrol which need to be considered when decanting fuel into the fuel tank etc , we need to consider safety a bit more than when using kero/diesel..............so no sparks or naked flames within 6 metres .

Cheers
John

[elventu]

I'm watching for 12v blowers for starting.
I found an E-bay auction that sells blowers similar to this one (new old stock, the vendor said me the data are about equal to this actual product).

I know it is small, but due to the small price I can maybe couple two...?
Flow seems to be consistent, pressure maybe is too low.

docs-emea.rs-online.com/webdocs/1487/0900766b81487347.pdf

They ask for 23€ each.
Suggestions?

I came across this because at now I can't find 12V blowers, I can try for 18v leaf blowers, but I need to make a 24V system only for starting.

[racket]

Hi Davide

Those blowers will be too small

Cheers
John

[elventu]

John, did you have suggestions on how can I try?
Maybe I'm not using the right keywords for searching..?

[racket]

Hi Davide

Those 18 volt blowers probably would work on 12 volts just with less power output

Cheers
John

[elventu]

What about this?
www.ebay.it/itm/Car-Auto-Electric-Turbine-Power-Turbo-Charger-Tan-Boost-Air-Intake-Fan-Universal/183504432786?hash=item2ab9b76e92:g:-TQAAOSwwvtb0DAA

For sure it can't do anything good on a car intake, but maybe it can do the job as a turbojet starter, for my small turbine...?

[racket]

might be worth a try at that price