Cant Get My Turbine Engine Started

[Jetman]

Hello, I will try it in a few hours and let you know…. Thanks for your help!

[slittlewing]

I can’t work out where your fitting is with the 1mm hole but your 100psi max hose should be connected to an injector with either an open 6mm hole or preferably many smaller holes like you have on your tube in the primary zone, without any prior restriction.

Here in the UK you can buy 0-4bar adjustable regulators for larger propane bottles, with one of these I was able to run a 2.5” inducer turbo and throttle it to 2 bar boost.

Also I would advise against any brass inside the combustion chamber, it will melt.

Cheers

Scott

[Jetman]

Hello, I drilled the hole to 5 mm, flow is way better, but still won’t start. The exhaust turbine was getting red hot for some reason? I think it is getting close… please help me to troubleshoot. Thanks!

[racket]

From your pics it looks like your leafblower is an "axial" blower, not the best for starting an engine as they can't produce the "pressure" required to "force" air through the engine , the new axial blowers are great leafblowers but like axial jet engine compressors they are fussy about having the right flow to rpm conditions , when you put the blower to the turbo inlet the air speed through the blower is reduced and the axial fan experiences "off design" conditions that probably send it into surge .

We need centrifugal blowers , not blower vac units which have larger clearances on the wheel which prevents pressure buildup.

A "dull" redhot wheel isn't a problem , just don't let it get bright red/orange , if you can't get the engine spooled up within 20 seconds , abbort ..............let it cool and start again .

You could try "adjusting" the blower to comp inlet distance/gap to maintain more favourable blower operation , ..........the blower should be producing some "thrust" when just blowing into the air , like a RC ducted fan engine , you need to maintain that level of "thrust" when applied to the engine , it'll require a bit of juggling clearance distances to keep your axial comp wheel working at its optimum , as the engine spools up you could close up the gap until its sealed against the comp housing .

If that still doesn't work , you'll need a stronger leafblower with a centrifugal comp wheel inside .

Cheers
John

[Jetman]

Hello, I use the leaf blower and air compressor, but I will try to find a centrifugal blower. Is there any way I can call you or video chat sometime racket? Will the needle valve work on the propane canister to regulate flow? Thanks!

[racket]

Hi

The cylinder valve can be used as a "throttle" , the ball valve for a quick shutoff if required .

LOL, video chat , I wouldn't know how , I don't own a mobile phone , no need for one

Better to get you sorted on the Forum , that way others can gain from it :-)

Cheers
John

[Jetman]

Hello, I have an update, I used a vacuum and it got going way better!! It did not fully sustain, slowly dropping rpm’s, but it may just be the fuel output. What do you think?

[racket]

Yep , keep the starter going and add more fuel to "get over the hump" , vacs are OK because they produce "pressure" but might be a tad small on your turbo size to supply enough air for idle , but great on smallish ones.

Keep an eye on your turbine temperatures though , a fast start can get away with some flames out of the turbine wheel for several seconds , but a longer spoolup needs to be "cooler" to prevent overheating the wheel .

We all run into first spoolup "problems" with a new engine build , but once we learn what the engine requires it'll get easier :-)

Cheers
John

[Jetman]

Hello, had a good run, not 100 percent there, but almost! Is it normal for the exhaust turbine for the tips to fall off, or wear?

[madpatty]

Hi Jetman.

That turbine is gone. Tips have melted off.
Over temperature has caused this.

[Jetman]

Hello, how do you stop it from overheating? Whatever I do with the fuel, there is always a flame out the end?? Thanks!

[racket]

When you say ..........."not 100% there, but almost " ..........do you mean getting to self sustain , or 100% max RPM ??

If you've destroyed a turbine wheel just getting to idle , then you haven't been keeping an eye on exhaust temps and haven't followed my "20 seconds and abbort" suggestion :-(

In my last email I mentioned "flames out of the turbine wheel for several seconds " , it takes a lot longer than several seconds to do that damage .

If you have flames from the exhaust it means either too much fuel , or poorly presented fuel as can happen if theres axial delivery of propane into the flametube , or insufficient starter power , our engines require considerable starter power especially with cold oil , heating the oil and turbo prior to spoolup can help .

Propane is such a very forgiving fuel and such are fast burning fuel that flames from the turbine are "rare" compared to liquid fuels , something ain't right .

During your spoolup you may need to slowly increase your fuel delivery as RPM rise to prevent flames .

That wheel will need replacing before anything else , keep it as your first "trophy" :-)

Cheers
John

[Jetman]

Hello, yes I will have to replace it! I must’ve gave fuel too fast, but I guess I learnt the hard way. When I sAy 90 percent there, I mean when I take the vacuum off, it slowly drops rpm. I thought I followed the 20 second rule, the rpm was still climbing so I kept giving it fuel. :-)

[racket]

You need to keep the starter engaged until the engine is well past self sustain , turbine engines are "slow starters" compared to an IC engine , they take time to wind up , your idle speed is going to be 40,000 rpm minimum .

It sounds like you had a hung start where you didn't reach self sustain for whatever reason , but kept supplying more fuel in the hope that RPM would rise , unfortunately all that achieves is a dead engine , once RPM start to fall ..........ABORT

With propane, because it mixes and burns so fast , the only time there should be flames from the engine is at the very beginning of spoolup , the flames should quickly retreat inside as the RPM rise , if the fuel delivery is kept constant the RPM will rise to a point where they stabilise , more fuel is then required to increase RPM ...........too much fuel too quickly can cause spoolup to "bog down" , but generally that would mean flames from the engine.

It still sounds like theres a starter problem , is the starter sealed against the comp housing inlet ??

Are there any leaks from the various flanges , any leakage of air will mean the turbine will be at a disadvantage , its compressing air that then doesn't expand through the turbine to help power the comp wheel .

A video of your start technique would be helpful once you replace the turbine wheel .

One other thing that needs clarifying , your lube system , what pressure , what oil etc etc ??

Cheers
John

[Jetman]

Hello, I am using a 60psi diaphragm pump, with a by pass set to 40psi with 15w-30 oil, which is what the semi supplies the turbo with. I could probably seal the vacuum a bit better, but I will have to find a new turbine… Thanks!