SUSTAIN'D TURBO JET

[racket]

Hi Blake

Yep , the 3 inch dia at the entrance to the compressor wheel .

Cheers
John

[areacombustor51]

Finished my combustion camber today. I have a fee things to finish up. I did a test run tonight and started it on propane. I found the sweet spot with the mechanical vanes but couldn't seem to get the turbo to self sustain. I'll post pictures later. Is there a trick to starting the jet engine

[racket]

Hi Blake

What are you using for a starter ??

The most common problem getting an engine to start is starter power , we need to achieve a lot of rpm , you'll need to adjust the variable vanes to some mid point in its range that produces the greatest rpm for the input power being provided , this will be when the comp/turb combination is running at their best efficiency .

You don't want too much fuel too soon , gradually increase fuel as the rpm begin to rise during a start all the while keeping those turbine temperatures under control .

A 3 inch turbo will be flowing a lotta air so you'll be needing a fair amount of fuel even at idle ................have you done any fuel flow calculations etc ??

Cheers
John

[areacombustor51]

No fuel calculations. I got it started off a shop vac and propane. I haven't been running a propane regulator and my propane tank has been frosting over. Figure this could be causing cold fuel. So the vanes are basically setting themselves as the rpms raise the vanes slowly open on there own. What temparure zone am I shooting for and where? The flame itself or the exhaust housing temperature.

[racket]

Hi Blake

You'll probably find that a shop vac won't be able to supply sufficient air for starting a 3" inducered engine unless its a very big vac . .

Propane cylinder freezing will reduce your vapour pressure within the cylinder , and fuel flow into the engine ...............what sized cylinder ............ , you'd be needing a 20 lb BBQ size..............try sitting the cylinder in a bucket of warm water to retard freeze up .

Try fixing your vanes at mid range , wide open and there won't be enough energy transfer to the turbine wheel to aid spoolup .

Gas temperature ~1500 F - 800 C during spoolup , measured downstream of the turbine wheel in the jetpipe , running temperatures will be lower due to temp drop across the turbine from the greater pressure drops , but during spoolup both T I T and T O T are roughly the same as theres minimal pressure drop .

Measuring exhaust housing ( scroll) temps will produce an under read of temps from too much lag time until the scroll temps stabalise ..............a thermocouple in the gas flow will produce the better reading

Cheers
John

[areacombustor51]

Ok I've tried a shop vac and a leaf blower. I can't seem to even get the turbo to spool. It's burning what's going through it but doesn't seem to be able to begin spooling, I have my vanes set around 1/4 open, full open the turbo almost stops spinning. So I have been looking on YouTube trying to figure out how people are starting theres. What would you suggest for a starter generator. Also my jet pipe is turning cherry red. Is this normal.

[areacombustor51]

I tried a Dremel tonight. No enough torque to turn the wheel. So I got a rc electric motor but it's not brushless. Il try that. Is there a way to start it off compressed air

[racket]

Hi Blake

You could be feeding too much fuel in too quickly if your jetpipe is glowing , remember max temp is 1500 F - 800 C .

Try spooling up slower , it takes anywhere up to 30 seconds to start an engine , you've got to accelerate it from nothing to 30,000 rpm or more , it takes time , so feed in the fuel slowly until you hear it starting to accelerate past the point where the vac runs out of energy and the rpm had stabalised.

Guys have used Dremels as well as RC brushless motors .

Cheers
John

[racket]

Hi Blake

One other thing .............what flametube and fuel injector are you using ??

Cheers
John

[areacombustor51]

Flame tube is 6x18 traditional design. Fuel injector is an air solenoid muffler

[areacombustor51]

Alright I have tried the dremel rotary tool and it didn't have the torque to get it spinning. I tried a pneumatic micro Looks like a dremel. Rpms are rated at 56,000, but could turn my turbine wheel. Help me spool

[areacombustor51]

?

[racket]

Hi Blake

Fuel injector could be your problem , a muffler will produce a "ball" of propane that won't mix with air , you need the "standard" short section of metal tubing positioned axially in the centre of the flametube end , with 6 to 12 small diameter holes ( 1/16") in the side of the tube ( 5/16" -3/8" tube ) to squirt jets of fuel radially out towards the flametube primary zone wall holes, ...........its critical that the end of the tube is sealed off so that there is no axial fuel squirt .

Your "ball" of propane will be "contained" in the centre of the flametube and will take considerable time to mix with the incoming air , probably not until it reaches the tertiary main dilution holes which have sufficient energy to punch into the propane , by which time it is too late :-(

Change your injector and see what happens .

Cheers
John

[areacombustor51]

Ok so like a grill. The tubes carry the fuel throughout the bottom of the grill. I understand I'am going to use 1/4 pipe seal the end off and pop around 12 holes in it. So basically it spreads the flame throughout the whole tube rather that releasing the gas in one spot. So how long does the fuel tube need to be.

[racket]

Hi Blake

A couple of inches projecting into the flametube should be plenty.

Yep , the small holes will create jets of propane that will be travelling pretty fast and which will take the fuel across the whole crossection of the flametube , your current muffler injector is designed to reduce air/gas velocity so as to quieten it, but because its travelling slower it won't mix with the air as effectively.

Cheers
John