Johanssons Jet-Cart

[Johansson]

Yup, finally my turbine-gocart seems to come together.

I never really believed that I would get this far after having searched the web for months after a suitable oil pump, but the only thing left is to get some hoses made and to hook up the gauges and switches.

[Johansson]

...

[mk]

Nice kart. Congratulations!

Wouldn't want to ride it with long hair, would you...

Hey ho, let's go!

Is it a challenge?

People having long hair (like me; but not too long) do have their tricks...

[Johansson]

Scarfs and pony tails strictly forbidden...

Today I got all hoses made and bought a new propane tank, tomorrow I will start to hook up the gauges and instrumentation. The biggest problem right now is to find a suitable rubber hose to connect the compressor housing to the combustor, the housing is slightly larger in diameter than the combustor so it can be tricky.

The riding have to wait until the tarmac returns, right now it is quite slippery outside...

//Johansson

[Tom]

Mk is right, we have all sorts of ways to keep hair out of intakes, etc. Like....hats.

Tom

[Johansson]

A main power switch away from success! (or perhaps a big bang...)

[Johansson]

Today I ran it for the first time, and it ran perfect! The throttleability (?) is outstanding, the engine selfsustain well below 0.5 kg compressor outlet pressure and responds immediately on the throttle.

Tomorrow I will mount the EGT and tachometer and repair the hose between the compressor and combustor, I had to glue one together from a rubber sheet and the weld couldn´t take more than 1 kg pressure before it opened up a little and began to leak.

I have a mpeg on the first run, but since I surf at 52kbit/s there is no way that I can upload it... :-(

A crude afterburner will hopefully be built tomorrow and some kick-ass pictures taken when I burn down my friends metal shop...

//Anders

[mk]

Cool.

Let the forum users see these pictures...

[Johansson]

The afterburner kind of works, on low rpm it self ignites the diesel fuel and spits out a 3 dm long flame but when I spool the engine up to 50-60k rpm the flame is put out and an enormous cloud of smoke covers the area... :-)

My guess is that I have to install a second flame stabilizer in the afterburner, it manages to hold the flame when the exaust velocity is low but as soon as the velocity increases the flame is blown out the exaust. The flame holder is made with a small cone after the injector and after that an outer ring made from L-profile steel. Perhaps another ring 5-10 cm further down the tube will do the trick?

A friend belive that the injector should have several smaller holes instead of the existing single hole to improve the vapourisation of the diesel/gasoline mixture.

The injector is a tube welded shut with a 2-3 mm (don´t remember) hole facing the turbine, and the pump is a fuel pump from a racing car that puts out 0.3kg fuel pressure.

I have a 174 MB video of the last run, but no possibility to upload it... :-(

//Anders

[Johansson]

A few hours ago I fitted another flame holding ring inside the AB, and the flame sustains much better now. A strange thing is that the 40-50 cm flame from the AB pulsates very fast and cannot stay still, it wiggles around a little which brings me to the conclusion that I feed it with too much fuel. Tomorrow I will drill a smaller hole in the injector and see what happens...

//Anders

[Johansson]

But the EGT is just above 600 degrees C. I forgot to mention that a little jazzing on the throttle is needed to get the 50/50 diesel and gasoline mixture to ignite...

//Anders

[Johansson]

The EGT rises only a few degrees from idle to full throttle, I made the AB exaust nozzle slightly larger than optimal for test purpose. It is measured directly after the turbine, but when I looked through the AB when running at 45k rpm (without the AB lit of course) the turbine wheel did not glow visible which must be a good sign.

When the EGT has lit a few times the flame stabilisers glow brightly and ignites the fuel easily without any jazzing. It is strange that the diesel mixture doesen´t ignite instantly, the "flame point" for diesel is if I remember it right ~300 degrees Celsius so the twice as hot stream of exaust gasses should ignite it immediately.

By the way, the compressor outlet pressure at 75000 rpm is only 1.2 bar. This means that the turbine housings A/R ratio is acceptable, right?

//Anders

[Johansson]

I decreased the injector diameter to 2 mm and got a nice sustaining afterburning up to 55000 rpm, above that the flame is blown out because of my thrown-together flame holder. Next weekend I will try to narrow down the exaust cone to an optimal diameter and observe how the AB reacts to that.

I believe that the increased pressure in the AB will help to sustain combustion at higher revs than before, at the last run with AB the EGT peaked at 590 degrees C. I will try to build a cone that keeps the EGT at a steady 650 degrees at max revs. My first exaust cone had a bit to small diameter, and the EGT went hotter and hotter the higher the rev. I had to stop when the EGT reached 720 degrees.

In interesting observation I made yesterday is that the EGT decreases 15-20 degrees when the AB is lit. (without any fuel flowing over the temperature probe)

//Anders

[Johansson]

Hmm, interesting info. I will have to figure out a way to measure the TIT without melting my probe, it is a cheap one with a plastic handle that is partly melted already thanks to the afterburner. Perhaps by drilling a small hole in the turbine casing and threading it so I can put a bolt in it when not in use.

I have planned to get the turbo fixed up as soon as I finished experimenting with it, the bearing is ok but the Scania V8 engine it came from has dropped soot and other particles that has impacted on the turbine wing tips. The balance is fine however so I don´t worry, I just try not to spool the turbine so high in revs.

What is the recomended highest TIT, and does it change when the exaust nozzle area is changed or is it just TOT that changes?

//Anders

[mk]

Johansson, what bearings do you use? The original ones or others, improved ones?

I have an Garrett turbo charger laying around. Turbine max. diameter is about 40mm to 45mm. Nothing is damaged. Only the compressor wheel has some slight impacts through dirt or s.th. on the front edge of the six main blades.
I think, only the original bronze glide bearings might cause problems at higher RPM numbers or a too low oil pressure or oil supply.

I don't have any experiences with turbo jet engines, so it might be worth starting a new thread here.