Diesel powered Aliexpress GT45 special

[4x2]

Starting the thread with the "2nd attempt" already put in, that's always a good sign...

So quick story: from the Netherlands, too much free time at work (due to being employed as a service engineer with a fairly limited workload when not on assignment) and always enjoy playing with welders/grinders/lathes and all those toys to create something just for the sake of it. Mostly spend that time on breaking cars and motorcycles.
In any case, earlier this year I was in Seoul on a business trip and during a lazy day off started browsing aliexpress, found a big turbo, mind started racing and decided to finally try and build a turbojet (based on RCdon's website, but quickly read that his calculations were a bit questionable)

Turbocharger was a GT45, 69mm inducer, 98mm exducer, AR .66 on the compressor, 88mm inducer, 77mm exducer, AR 1.05 on the turbine (all specs are just copied from the seller, didn't bother to check them besides the compressor inducer, which was correct-ish)


Ran jetspecs, googled a bit where to get the stainless tubes required (surprisingly cheap actually, only the cones and v-bands were a bit more expensive but nothing too bad) and ended up with a nice flower pot:


I know the angled entry into the turbo isn't the most efficient but it was done for intended packaging reasons (whatever that means)
The holes have been changed a bit since that picture as well, row of 1mm cooling holes near the cap, enlarged a few of the primary ones around the predicted spray impact (and closed a few others as a result), hole area per zone is still roughly within the jetspec recommended area.

Bit low on pictures after (and can't upload any new ones on my work laptop), so I'll just give a speclist for now:

Chinese GT45, divided turbine housing that has been smoothed a bit to hopefully prevent molten metal flying into the turbine wheel.
Rotoflow pumps for oil & fuel.
12V brushed 250W motor via chain drive to power the pumps (1:2.5 reduction, oil pump needs to be changed to 1:3.5 or so)
OEG.net 7GPH nozzle as main fuel delivery.
Some chinese obscure 0.1mm nozzle angled towards the spark plug for starting.
Random spark providing aliexpress thingy connected to a spark plug that protrudes slightly into the flametube.
Stainless tubes with compression fittings and needle valves etc for the pressurized part of the fuel delivery.
Some 12V electrics incl an 85Ah battery, few relays etc.
EGT/boost/oil pressure gauge, all chinese.
Analog fuel pressure and P2 gauges (to monitor fluctuations)
Homemade oil tank (about 5-6L or so, no oil cooler at the moment)
Bunch of pressure switches that aren't hooked up.
Some junk I forgot.

The eventual goal is to turn it into a gas producer for some kind of vehicle, but not before I had some thrust/afterburner based fun.
Also intend to have it controlled by an arduino, electric start, all kinds of safety switches etc, but first I wanted to have the basic version working.

Anyway, first startup attempt with a vac cleaner: some rumbling, lots of leaking diesel, slight jet noises but concluded the vac cleaner wasn't strong enough.
Ordered a 2-stroke leafblower, next attempt: prolonged start, lots of flames, but it did self sustain (bear in mind: no gauges attached at all, so not a clue what was happening)
Then a massive bang and a very sudden absence of said jet noises (but lots of thick white smoke, which was worth something)
Turned out the turbo had seized (rebuild kit is lying around, not too much damage), discovered the why a few weeks later when disassembling stuff, the set screw for the oil pump sprocket had worked itself loose, so lots of loctite was used after.

Found the same turbo for even less on amazon, assembled everything again over the next few weeks, this time taking care to hook up gauges, few failed start attempts (due to a broken sparkplug), modified the fuel delivery slightly and a few days ago managed to get a pretty much trouble free startup:


Some of the values are in the video, it only ran for about 2-3 minutes total, so not a whole lot of time to gather data, but everything seems healthy so far, only the oil pressure was dropping a bit to about 2.5 bar when warming up, so I think I'll  try reducing the pump RPM a bit more to see if it helps.

More pictures and videos will probably follow over the next 1-2 weeks, after I'll disassemble stuff again, try to make it a bit more compact and think about what to attach it to to drive it around a bit.

[htevo80]

That's a really nice looking build and you can never use to much loctite. A word of warning though I made my first jet from a eBay gt45. You have to be careful with them because the turbines don't hold up well at higher P2 pressures with normal exhaust gas temps. But if I remember right it put out like 40 pounds of trust so around 40 shp(i think). Good luck on your build.
Gavin

[4x2]

If it grenades itself I hope I have enough logging data to prevent it from happening again with the spare wheel.
High 40's is what I'm aiming (hoping..) for, if that can be converted into 40+ HP I'm more than happy.

[4x2]

Few more days passed, few more runs passed as well, came up with a nice list of things to improve (outside of appearance/packaging)

So the main issues at the moment are the main injector ball valve that isn't working (it idles at 0.3 bar with it closed, too low, but it idles nonetheless)

And a diesel leak inside the flame tube that turns a part of the end cap beyond red hot after 2-3 mins and it starts to bulge, so I simply shut it down to prevent everything flying everwhere.

The ball valve is easy enough, just replace it with a different one, the end cap is just a leak from a gasket, but I will rebuild it to reinforce everything and make it a bit easier to remove the spray nozzle.



Other than that, startup (once I figured out the procedure) is relatively easy, even in cold/humid conditions and infinitely easier when it's warmed up a bit, but it will require some changes to get it to start electrically I guess.



That just leaves with a few pics after removing the flametube from the outer can:



So that shows the inside of the outer can, the slightly weird looking double wall at the end is the seating area for the flametube and should cover the thermal expension.







The inside of the flametube shows the location of the diesel leak and glowing end cap.

As far as I can tell from the soot etc the flame isn't moving beyond the tertiary holes while running, so that seems ok, although the discolourization could be a bit more even, but that might be because of the diesel leak.





Compressor wheel shows no obvious damage, so that's good (other than some junk from transportation)





No obvious damage, but not to sure what to make of the colour pattern (EGT's never went above 550-600c TOT iirc)



And last a video of some minor abuse at night while camping, I'm pretty sure the startup was a near runaway, max P2 while running was 2.0bar (the flames halfway through the video happened after closing the leaky ball valve during idle to see what it would do)

[slittlewing]

Looks good, I’m interested on how good/strong the AliExpress turbos are considering they are ridiculously cheap in almost any size!!

As for the white colouring on the turbine wheel, I think this is a kind of “soot” as you mention. After running my turbo on both kero and propane, it had the same white coating (albeit on the whole wheel and not just the tips). Similarly TOTs were fine so I think it’s nothing to worry about

Hope you get the leak fixed to avoid the runaway starts!!

Cheers
Scott

[finiteparts]

The pattern on your turbine is quite normal. There is quite a bit of soot in your combustor and on the turbine wheel. So at some point your engine was running very rich, maybe before it ran away in the video. The outer portion of the turbine wheel runs hotter and cooks the soot off.

If you look at the equation for turbine power, there is a term that subtracts the gas swirl speed in or after the turbine from the gas swirl speed as it enters the turbine. There is a radial decrease in swirl velocity as the gas passes through the turbine due to the imposed solid body rotation of the gas in the passages (due to the presence of the turbine blades). A solid body rotation imposed on the gas means that the swirl speed of the gas is a function of the radial distance from the shaft centerline and the rotational speed. So the gas at the exducer tip experiences the smallest amount of swirl speed reduction and thus the lowest temperature drop. The gas exiting near the hub experiences the highest level of change in swirl speed and thus temperature.

Now, you might be tempted to say that since the gas at the tip experiences the smallest temperature drop, then it must also contribute the least to the overall torque output, but that is not necessarily correct. The tip has the largest through flow area and thus passes the highest amount of hot gas through the wheel. Since the mass flow that can pass through the area swept out by each radial distance changes as a function of radius also, it is not so clear which radial station of the rotor contributes the most or least to the overall torque output.

I hope that helps,

Chris

[janek]

Can you please put up some photos of your fuel injection/atomisation setup? Your ignition system too would be great! I'm desperate to switch my big boy to diesel, but haven't found a reliable method for it yet!

I can run mine on propane at full valve open in a warm bath, emptying the cylinder in 5-7mins. it still has more to go, and switching entirely to diesel would be amazing!

[4x2]

I'll try to get some photos up when I'm back in the netherlands, although I've already decided to re-design the end cap, hopefully providing easier cold starts.

[Colin Heath]

Nice build and great to see the same turbo I am about to use being run on diesel. I am planning diesel or kerosene as it will be going in a vehicle.

I too plan on running mine as a turbo shaft so watching with interest.

Cheers,

Colin

[4x2]

Still alive, but this contraption is currently at the end of a long backlog of things I need to finish (luckily it can be worked upon in any spare time if needed)
Did have some time to think about new applications in the turboshaft role, it's not getting any less ambitious unfortunately, guess I'm combining all of my previous shower toughts into 1 giant clusterfuck of a contraption..

First I'll need to figure out a way to get it from my parents garage to my own. Guess I'll make a trailer for my 25km/h scooter and transport it that way (running ofcourse)

[4x2]

Well, the trailer has been created, the entire contraption has been moved to my own house, sitting underneath a plastic sheet for the past 2 months or so.
It did attract a bit of attention, even though it was switched off (ran out of 2-stroke mix for the leafblower, couldn't be bothered to get more that instant)
I wonder why...



In any case the next step is building a starter motor, I've got a brushless motor for that (4076, 2250KV, 120A ESC) should hopefully be some 2.5KW on 12-13V and run it op to 20K+ for starting.
I was planning to use it as a generator as well, in an ideal situation to keep the battery fully charged, but if it just makes the current drain a lot less that's fine for the time being.

So, permanently attach it to the turbocharger shaft via a coupling, start the engine, wait for it to run up to idle speed and then switch the brushless motor over to generator functionality.
Additional stress on the turbo is expected and accepted, the motor will be run up to 60-70K in its generator function, so a regulator is needed and *hopefully* the motor bearings will survive this (I might change them to a looser fit)

Just wondering if somebody has toyed with this before ?

[racket]

I think you'll be doing the experimenting without any previous builds to go by.

Be careful about exceeding the starter rpm , bits going into the comp won't end happily.

What sort of permanent coupling do you intend to use ?

Cheers
John

[4x2]

For the time being I'm just using a socket 12 I welded to an axle (then put in the lathe so it's somewhat straight) that's pretty much a press fit on the motor shaft.
When I said permanently I meant something that will always turn at turbo speed but still able to remove it (and leaving some room for expansion etc)
Startup sequence I suppose I'll just run it up to 3-4000rpm, then turn on the oil pump and continue the startup to (hopefully) avoid issues with thick oil.
But that's looking several months into the future, I have too many projects...

As far as max rpm, I think this motor was rated for max a 5S LiPo, so that'd mean some 40K rpm, so that would at least put me in idle range to see if it works or not.

[racket]

Yep , a socket that fits the comp nut should work , thats what I use for my starter on the 12/118 engine and its often seen >30,000 rpm during a spoolup before disengagement