FD3/64-2:1!

[Axel Borg]

If you are a technical geek like me , you might want to listen to the film clip with head phones since you then clearly can hear when the engine is lit.
There is a beautiful low pitch sound from the burning gas to be heard .
Listening on the clip via the speaker in my lap top makes it impossible to distinguish such details.

[Axel Borg]

During my first test run, which i have not shown, the turbine wheel glowed bright yellow and would only self sustain for a minute or so before the wheel turned white and I had to turn the motor off.
To my surprise that problem was completely cured with the second wheel, slightly longer blades3.5mm, and a 9-10mm shorter centre hub. According to Shreckling the distance between the NGV and the turbine is non critical so i let the accidentally rather long distance of 12-15mm be. Now the turbine blades are only a few mm. away from the NGV.
The 3.5mm extra blade length is obviously taken from the turbine centre, so the outer diameter is still the same. The decision to make the blades longer was due to the fact that I could see that the inner part of the turbine blade, that correspond to the inner part of the NGV, could not do any use full work since the blade angel at that point was zero or close to zero.

the improved turbine wheel to the right, have 3.5mm longer blades.

The improved turbine wheel has a 10mm shorter centre hub, this means that the turbine comes closer to the NGV, which proved important.

The 2:1 factor is not hard to understand, but I was still surprised when doing a side by side comparison. The small wheel is the original, 64mm diameter.

[Johansson]

Congratulations!

How are the bearings holding up so far?

[Viv]

Congratulations Axel, its been a very interesting build process and thanks for sharing it with us all in such good detail

Viv

[Axel Borg]

Thank you!

The bearings, Biltemas 8mm ceramic hybrid lager, is holding upp well so far.
Testing has only just started. I do have a good feeling about it though, since they did survive the test runs
when the turbine wheel were yellow-white....and the low rpm runs when they do not get any lubrication.

Glowing faulty turbine run....

http://www.youtube.com/watch?v=7QWhSGopoTo

[Johansson]

Damn that was hot!

The new turbine wheel seems to run very cool, have you measured TOT yet?

Have you any thrust expectations for the engine? The original FD3 had a intake diameter of 33mm and produced around 2.3kg of thrust, so each 377mm2 gives one kilo of thrust. Your 2:1 engine has a 66mm compressor inlet, 3419mm2, and "should" produce somewhere in the region of 9kg.

[Axel Borg]

9kg thrust would be nice.

I think it will be possible if a make a new turbine wheel of thicker SS sheet.
I would also have to beef upp the axel diameter to like 30- 40mm diameter to avoid
wreking it at full rpm.
Sorry, no TOT measurments yet.

[Johansson]

How is the liquid fuel conversion coming along?

[Axel Borg]

Right now I’m waiting for some thicker SS material for a new more rigid turbine to arrive.

I did a shorter test run on pure diesel anyway, and it seems promising. I had a serious hot spot that I think is related to a leak in the fuel line that I have to fix before next attempt. One thing that was directly obvious is that a motor this size is THIRSTY. 0.3liters diesel seamd to disappeared in a matter of seconds!
The original motor is said to use 0.2liters/ full throttle. Double the size results in 4 times the fuel consumption.... = 0.8liters a minute at full throttle!
More than one decilitre every 10 sec….

[Zippiot]

Isnt double the diameter considerably larger than double the area

[Axel Borg]

Still waiting for the thicker SS material to arrive.
In mean time I made a turbine of even thinner 0.5mm stainless steel...which works fine as a test turbine. I have put a thicker plain steel washer in the centre to stabilize the flimsy turbine disc though...
I fixed the fuel leak and run it successfully on pure diesel. I used a multipurpose windscreen washer fluid pump as fuel pump. I control the speed with a simple homemade pulse width modulation circuit based on the 555-IC. The pump/injection needles are over dimensioned so the throttle is VERY sensitive.
Its amazing to se how quick the thin turbine blades heat up during acceleration in the low rpm region and how fast they cool down once higher speed is reached!
I think the combustion is fluctuating slightly but it does not seem to present any problem

As always, make sure to wear head phones while watching the video clip, it is realy enlightening! Lots of information hidden in the sound of a engine.

Youtube video testrunning the motor on diesel: http://www.youtube.com/watch?v=_sORDfes9Sc

Picture shows both the propane and the diesel fuel system. They both inject into the vaporizing sticks. Click on the picture and have a closer look!

Experimental turbine with holow blades for cooling air. It functions as a turbine but not very well.

Fuelpump and pulse width controller, diesel in the 33cc aluminium-can...

Perfectly uggly welding!

New thin turbine spot welded onto thicker steel disc.

[Johansson]

Absolutely fantastic work Axel, you have built one hell of a combustor to work on diesel the first time you try it.

That the 0.5mm turbine blades can take the stress is also worth noting.

[Axel Borg]

The Schreckling design is not bad, and with a total of about 2 meter stainless steel vapour sticks the diesel turns into flammable white smoke!
I’m practicing the starting procedure and can now easily start the motor with a small disposable butan/propan bottle as preheat source.
This makes every thing much more user friendly, not having to bring a bulky 6 kg LGP canister to what ever location in which I might want to start the motor.
I think I will change the diesel injection needle size though to get better control over the throttle.

[Axel Borg]

I changed the needle size from 0.33mm to 0.25mm. The throttle control is better now as a result of the change.There is a little throttle lag compared to running on LGP.
I ran the motor up to 22.500rpm which is about 60% of full speed, in this 2:1 build. I’m still using the 0.5mm thin turbine wheel.

10x0.25mm needles.

[Axel Borg]

So I finally bought a 1000C max K-type sensor needed to measure the EGT.
I have only conducted a few measurements at rather low throttle settings so far.
At around 14k rpm the hottest spot directly behind the turbine (20mm away from the turbine blades) is 590C.
I have to make further tests with a larger fuel tank, the 33cl tank runs empty before I have had the chance to fully investigate where the hottest parts of the streaming exhaust gas is located.
And also, I need to do this out in the open air, which is quite cold right now, so I will wait until the temperature goes up a bit. Its too hard to work with stiff fingers…..