t18a96 turbo jet

[sub22b]

Hi guys thought i would share my project with you. Its a airesearch t18a96 turbo with a 3.68a/r exhaust housing unfortunately i am not sure on the comp housing a/r as the tag has been removed. It has a 4.5 inch inducer with a 5 inch exducer. The engine idles at 3psi and so far it has been run up to 20psi. How ever i am having cold start issues were the lpg will ignite but the turbo wont spool up enough to maintain rpm. If i leave it for 5 minutes and try again it spools up straight away and can then be run on jet a1. Will post a couple photos when i figure out how to and will try and get a video of exactly whats happening.

[enginewhisperer]

could it be due to cold oil causing too much drag in the bearings?

[smithy1]

That's a fairly hefty sized turbo you have there, the 4.5" (~111mm) inducer is larger than the GT6041, the 5"(~127mm) exducer is a bit smaller though..cool nonetheless.

Please do put up a pic for us...

Cheers,
Smithy

[sub22b]

It may be the oil but i am only running 20psi cold. I got told by a turbo specialist here in NZ that i needed 350ml of oil every 15seconds to drain out of the turbo is that correct?

[sub22b]

The combustion chamber is 11inch and the flame tube is 8inch. At the moment i dont have any exhaust gas temp gauges on it but after playing with the flame tube several times and adding more holes the exhaust wheel has no glow to is what so ever even at 20psi of booot.

[smithy1]

On a turbo that size I'd suggest 1400ml/min is close to the mark. 20psi is a bit low though....I'm running ~70psi cold on my GT6041, when warm it's still well above 55psi.

I suspect the bearing/shaft condition is usually the limiting factor in regards oil flow.

Can you tell us what type/grade of oil you are using?

Cheers,
Smithy.

[sub22b]

Im using a penrite 15w-60 full zinc oil and my oil tank holds 5 litres. At the moment my oil pump is a subaru power steering pump powerd by a electric motor. I removed the pressure release valve to drop the psi as the power steering pump is capable of well over 100psi.

[sub22b]

s31.postimg.org/4doa5u8zv/20160720_192036.jpg
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s31.postimg.org/wqal4tfyj/20160720_192017.jpg

hopefully the photos worked let me know if they didnt thanks. Nick

[racket]

You're using a pretty heavy oil , and your ambient temps won't be too high at this time of year so that "thick" oil won't want to flow through the bearings all that quickly , and the drag will affect the spoolup .

Try using a LPG torch on the bearing housing prior to spoolup to warm it a bit , this should make it easier to spoolup , you should be able to get several rotations of the rotor by flicking the comp wheel with a finger , if you can't , you'll have spoolup difficulties unless using a powerful starter that can get rpm up to self sustain levels .

I ran a similar "heavy" oil in my TV84 bike engine , and in winter I sometimes had to warm the entire engine and oil tank to get a spoolup with the leafblower , I'd cover the entire engine and oil tank with a sheet and using a small electric room blower heater to blow hot air under the sheet to warm things up .

Once your engine is running and the oil warms up , you'll be needing several litres per minute going through the bearings and require at least 40 - 50 psi of pressure

Cheers
John

[sub22b]

Hi guys i just tried a thinner oil and it made a huge difference i also cranked the oil psi up to 50psi. The engine spools alot quicker now and can get it running from cold first time cheers for the help on that one guys. But i do have another issue i have just noticed my outer tank/combustion chamber and end cap gets very very hot is that a normal thing or is there a issue with my flame tube? It also coughs and splutters when i try push the boost past 20psi have i reached the turbos limits or could that be part of the issue were my combustion chamber is not working properly?

Cheers Nick

[racket]

Hi Nick

Excellent news .

Yep , the end cap can get very hot depending on your combustor design , it can be cured?? by adding some holes in the very top of the flametube so that air can flow across the inside of the end cap .

Could you elaborate on your combustor design as well as your spray nozzle size/type etc .

20 psi P2 isn't a max pressure on a turbo that size , you've got some way to go ;-)

The spluttering is probably a fueling issue .......more info please

Cheers
John

[sub22b]

Im using a evap tube system with 5 tubes and one injector feeding them that has roughly a 1mm hole but it doesnt have a very wide spray pattern. You will laugh when i tell you that the injector is designed to spray chocolate not kero. Im starting to think at 20psi of combustor pressure my fuel is no longer evaporating properly as im having to push alot more into only 5 tubes. My centre tube is 25mm with 5 12mm tubes coming off it. Im also ducting some air from my combustion chamber inlet to my evap tubes centre 25mm pipe to help push the evaporated kero out the tubes. The air feeding into the evap tube comes in just above my injector. There is some carbon build up on the inside of my combustion chamber and a very small amount on my flame tube so i think i may be burning some kero on the outside of my flametube for some reason.

[racket]

Hi Nick

When you say it coughs and splutters and theres the possibility of fuel being burnt outside the flametube the hairs on my butt say "surge" .

Could you do a rough drawing of your flametube/combustor as it could be some design problem .

With regards your turbine scroll housing , is it a split inlet or a single opening??

What sort of "funnel" do you have between the circular flametube and the rectangular scroll inlet port/s ??

What size is the afterburner nozzle ??

Cheers
John

[sub22b]

The turbo itself is a single inlet.this is the bottom of the combustion chamber were the flame tube locates its a 6inch not so round hole that tappers down to the 4 bolt turbo flange.

flame tube 8 inch down to 6inch


evap tubes with air feed from combustion inlet which meets up with a hole drilled in flame tube probably not the best way of doing it.


upload gif

[racket]

Hi Nick

Thanks for the pics , it makes it much easier to understand whats going on .

The flametube funnel should be OK , tick that one off :-)

The evaporator is one of your problems .

Having the air going into the side of the "trunk" is going to force the fuel to the opposite side of the trunk and down into the "branches" on that side , probably starving the evap on the other side , I don't like trunk and branch evaporators , virtually impossible to get an even outflow of fuel from the branches , resulting in poor combustion across the flametube .

There might also be an issue with the placement of the evaps , from the pic it looks like they may be a tad close to the flametube wall , leaving a core with no fuel.

With your flametube wall holes , what are their sizes and numbers ??

The evaporator outlets are also too far from the end plate , they only need to be >1.5 diameters away , so if 12 mm dia branches then only 18 - 20 mm clearance required.

Now for the wall holes..............

In the Primary zone we need air to mix with the fuel exiting the evap , so the holes need to be positioned near them , maybe have a look at what I did with GT6041 flametube jetandturbineowners.proboards.com/thread/78/garrett-gt6041-powered-kart?page=3

Cheers
John