"Fat Boy" 12/118 thrust engine

[racket]

Hi Jeff

Yep , she's a thirsty one , that little 10 litre test stand fuel tank isn't gunna last long .

Cheers
John

[racket]

Hi Ralph

On my 10/98 engine the NGV angle is set at an angle to get 18 X 9 mm X 20 mm throats , I'm not sure what the actual angle is , can't seem to find any drawings , but its ~20 degrees.

The 12/118 has 18 X 13.4 mm X 20 mm throats with vanes at ~33 degrees .

13.4 divided by 9 = 1.49 .

But by having the vanes at 33 degrees it limits the gas deflection component in the horsepower calcs for the turb wheel , that combined with the severely cutback exducer which also reduces gas deflection , makes for a rather "weak" turbine stage , a stage that will need every bit of help it can muster to power the comp .

Cheers
John

[racket]

Hi Alain

Yep , full bore runs will be noisy .

I'll try getting to high powers whilst still having the diffuser exhaust in place as it'll help keep temps down a tad , once I know what temps I've got to work with I can determine what sort of "nozzle" to fit .

The diffuser exhaust is still producing a pretty fast exhaust even at idle .

Cheers
John

[racket]

Hi Smithy

I'm hopeful that at a higher power setting that big wheel will be producing an efficient compression that will only require an ~137 deg C drop across the turb , so I won't get too worried unless theres an 850 C TOT ;-)

Cheers
John

[smithy1]

May 2, 2016 17:57:38 GMT -5 racket said:

Hi Smithy

I'm hopeful that at a higher power setting that big wheel will be producing an efficient compression that will only require an ~137 deg C drop across the turb , so I won't get too worried unless theres an 850 C TOT ;-)

Cheers
John

Yeah...fair enough.

Hmmm, she be getting up towards 1000c TIT @850c TOT, that's sailing pretty close to wind. That diffuser pipe should help.

Might pay to do a "pipeless" run and get some numbers, I suspect the diffuser pipe will skew the numbers a bit compared to being pipeless.

That big comp wheel should make plenty of air for the turb wheel to swallow....just hope it can use it and make enough hp to run the comp wheel at higher power settings without getting too hot....time will tell.

Keep up the great work Sir....Love your work John, I really enjoyed watching her finally come to life and breath with some fire in her belly.
There's nothing better than hearing your own turbine come to life for the first time, puts a silly grin on my head when it happens..!

Cheers,
Smithy.

[finiteparts]

John,

Congrats on another successful engine!

"The reward of a thing well done is having done it."- Ralph Waldo Emerson

I really like the sound of the engine shutdown...I wonder if it is the volume of it or the open turbine that gives it that nice sound?

Great Job!

~Chris

[racket]

Thanks Chris :-)

It is a "different" sounding engine , there seems to be a "rush of air" sound to it , probably from the "minimalistic" turb stage , the air gets into the flametube , is heated and then makes its escape without much interference .

Because the turbine wheel is "undersized" the theoretical jet nozzle diameter for the engine is only 6 mm smaller than the exducer diameter , its as though the turbine wheel is spinning in the jet nozzle .

Lotsa things I don't really understand at this stage , hopefully it will become clearer once I start collecting data at different power settings.

Cheers
John

[Chuks]

congratulation sir,
hearing the sound of that fat boy gives me hope.....

[ripcrow]

Congratulations john

[stoffe64]

Congratulations John!!,interesting sound from that engine, i love it!!

[racket]

Thanks guys .

We did 3 more starts yesterday without any problems with the batteries coping .

Took it up to ~20 psi P2 at which point it was still operating with temps in the 600s , sounding pretty good even with that diffusing pipe on her .

The starter motor seems to be doing the job without stressing itself , a bit warm to the touch after a start , but not uncomfortable to handle.

Theres a few little mods to the start process that need looking at but nothing that can't be easily sorted out.

Cheers
John

[Deleted]

Hi Guys
was good to catch up again
Here is the proof that Johns creation fired up
youtu.be/ySa7TpFFRvQ
enjoy
Chris

[racket]

Hi Chris

Mmmmm...........an interesting video ;-)

Shows all the little things that can easily go wrong , preheat gas burns all the oxygen in the FT because I was too slow hitting the starter, I blow some fresh air inside and the gas ignites and burns it all again so no ignition on the next attempt , then it "self ignites" and we're finally away ..............ah , the joys of learning how a new engine behaves .

Theres a few mods I'm going to make which should make things a little better , a micro switch in the start circuit that requires the starter to be fully engaged for activation and which will deactivate it if it even starts to disengage by even a millimeter , might even fit a warning light to indicate start circuit is powered.

I'm also looking at a decent tach that doesn't rely on a laser as a start later in the day with full sunshine found the current tach inoperable , the start was done "blind" , I simply kept the starter engaged until I felt it was up to speed , not really ideal :-(

LOL............Linda thinks I look quite mad in the vid , maybe its the Tee shirt that Anders sent me.

All the best with your new build ;-)

Cheers
John

[Deleted]

May 8, 2016 16:41:35 GMT -5 racket said:

Hi Chris

Mmmmm...........an interesting video ;-)

Shows all the little things that can easily go wrong , preheat gas burns all the oxygen in the FT because I was too slow hitting the starter, I blow some fresh air inside and the gas ignites and burns it all again so no ignition on the next attempt , then it "self ignites" and we're finally away ..............ah , the joys of learning how a new engine behaves .

Theres a few mods I'm going to make which should make things a little better , a micro switch in the start circuit that requires the starter to be fully engaged for activation and which will deactivate it if it even starts to disengage by even a millimeter , might even fit a warning light to indicate start circuit is powered.

I'm also looking at a decent tach that doesn't rely on a laser as a start later in the day with full sunshine found the current tach inoperable , the start was done "blind" , I simply kept the starter engaged until I felt it was up to speed , not really ideal :-(

LOL............Linda thinks I look quite mad in the vid , maybe its the Tee shirt that Anders sent me.

All the best with your new build ;-)

Cheers
John

GDay John

yes it is good to see whats on video afterwards ,shows just how much we miss when things get interesting....

a few 'mods' will help take away some of the guess work.

"Mad professor" is what I would call it ,at least there were more things learnt!

Thanks ,already onto Cameron to see if he has some bits...

cant wait for the full throttle run, going to need a good bit of rope (or chain)

Cheers Chris

[racket]

Hi Chris

The speed controller for the fuel pump arrived this morning www.motiondynamics.com.au/12v-48v-50a-internal-case-model.html , I'll do some experimenting on the weekend with it hooked up to the 24 volt starter batteries.

Have made contact with the local distributors for a decent tach www.jaquet.com/site/assets/files/1201flyer_turbotach_a4_en.pdf/ hopefully they'll come up with a suitable unit .

And I've ordered a limit switch for the starter engagement so no more stuffups there , its gotta be engaged otherwise no power to the starter , and as soon as it starts to move out of engagement power will be cut.

LOL...........I'm enthused

Cheers
John