Flametube Design

[nbatten]

Hello, I am new to turbocharger jet engine building. My first project is going to be a basic engine. I have a GT3076 Turbocharger as my base. The Inducer diameter is 2.24", my question is I used jetspec to give me the info for the flame tube design. It gives me a flame tube of 5" diameter with a length of 13.44" long. it tells me the holes are to be 24x1/4" for primary, 7x3/8" for secondary and 6x5/8" for tertiary. My question is what is the dimension for each row of holes from the end of the tube? (Formula?)  Should i split the 24 primary holes into three rows of 8 each like in the illustration? I will be using propane for the fuel source. Any help will be greatly appreciated.

Thanks in advance for any help offered.

[racket]

Hi

Have a look here first jetandturbineowners.proboards.com/thread/680/diy-turbines just click on the icons in each segment to get the info .

Yep , just follow Jetspecs for the flametube , have all air go through the holes , fit a smooth transition piece between flametube cross section and turb scroll inlet and make your propane injector so that it squirts the fuel radially towards the primary holes, NO axial injection down the flametube.

Cheers
John

[nbatten]

Awesome, thanks
One question, jetspecs gives 5" dia. X 12.88" length. Is says make the combuster tube and flame tube the same length. Does that mean the flametube goes to the transition point where the 6" dia. Combuster tube starts to go down into the flange at the 12.88" or the turbine inlet flange? In other words does the 12.88" include the transition or is that 12.88" of full diameter then the transition starts?

Thanks once again.

[racket]

Hi

If using "fast burning" propane then the 12.88" can be overall length including the transition piece , so say 10" of flame"tubing" with 3" of transition cone inside a 13" outer can , have the large Tertiary dilution holes just a bit above the start of the transition

Cheers
John

[nbatten]

The combustor layout as shown ? The propane injector would be a 3/8" tube with plug welded in end, 12 x .0625" axial holes aimed at the lower set of primary holes. Maintain the 1/2-3/4" gap between flametube and combustor wall.

Does all this sound right ?

Thanks again, Nik

[nbatten]

Also, The compressor air in, at A,B or C ? Ignition plug at A or B ?






Then finally the air in tangentially as in A, or perpendicular as in B ?






I appreciate all your knowledge and experience with the turbie builds, Thanks for sharing, Nik

[racket]

Hi Nik

Yep , flametube looks OK , ignitor in the side wall, delivery tube perpendicular and positioned as far down the outer can as possible, if you use a "full diameter" flange at the turbo inlet and a tubular outer can then the delivery tube can be fitted so that the air is blown into the plenum surrounding the flametube "funnel"...... jetandturbineowners.proboards.com/attachment/download/216

Cheers
John

[nbatten]

Would a hemispherical plenum work? I found some 14 Ga. stainless parts. One is a 6" to 3" hemispherical reducer with a v-band clamp on the " end. I would weld a T03 tp 3" pipe adaptor flange to the 3" end. I also found a 6" x 12" spool piece with v-bands on the ends. One would clamp to the 6" hemi-reducer and the other would be cut to length and a 1/4" stainless disc welded to it to hold 3/8" tube fuel supply fitting. 5" flame tube fit as before. I attached a sketch of proposed combustor assembly. Thanks again, Nik

[racket]

Looks doable

[nbatten]

What thrust / shaft hp could be had with a gt3037?
Comp. Ind=57mm
Exd=76.2mm
Trim=56
A/R=0.6
Turb. Ind=84mm
Exd=60mm
Trim=51
A/R=0.82
Jet thrust?

Shaft hp?
What free power setup?

[racket]

Mass flow ~0.75 lbs/sec , you might squeeze 30+ lbs of thrust and possibly 30 HP using a freepower wheel with a exducer of ~85-90 mm and a high speed gearbox so max freepower rpm can be achieved, but lots of unknown variables so thrust and HP might not achieve those numbers .

[finiteparts]

In your drawing, your injector looks like it is as long as the primary zone. You do not want it to protrude into the combustor very far. Things that get immersed into the combustor tend to burn off unless they are internally cooled with fuel or very high velocity air. Gaseous fuels do not have sufficient heat capacity to "carry" away the heat being convected into the tube from the flame impinging on the outer wall of the tube.

Additionally, the radially outward momentum produced by the fuel jets would act to counter the radially inward momentum of the primary jets, reducing the recirculation of flow in the primary zone.

Just make the fuel injector tube come in 0.5 to 0.75 inches from the dome plate...that should be sufficient to get the fuel into the recirculating flow, without it just washing over and hanging around in the dead zone near the dome plate.

Good luck!

Chris

[nbatten]

Chris, I placed it there based on information from racketman to have the Propane inject at the primary zone holes. Maybe I'm misunderstanding what he meant.

Thanks, Nik

[nbatten]

Chris, your saying inject radially just pass the top row of dome cooling holes?

Thanks, Nik

[racket]

Hi Nik

On Feb 17 I said ...."make your propane injector so that it squirts the fuel radially towards the primary holes, NO axial injection down the flametube" .

Your latest drawing was about the outer can, as was my reply also ..................thanks to Chris for noticeing your fuel injector length which looks like you're going to inject towards the Secondary holes, yep , shorten it up so that it squirts towards the Primary holes like your Feb 20 drawing , your latest drawing has left out the "lower" Primary holes only including the "upper" head cooling holes

Cheers
John