Attempting to Build my first Turbojet & have a few Questions

[thehazard]

Hi there,
I have decided to build my first turbojet and am beginning to start searching for parts. I just bought a turbo with a 60 mm inducer, but it comes with a few glaring problems. As shown in the pictures below it is a twin scroll turbo with the intakes to the turbine on the same side as the exducer. I bought it for 100 dollars Canadian, and because of how cheap it was I would prefer see if I could get some use out of it. I am aware that twin scroll turbos are not ideal for this application, but again it was cheap and the bearings seem to be in good condition. I aware of the program Jetspecs and will use its measurements in the construction of my combustion chamber. My turbo is the ITI LB7 Turbo, and I intend to use propane as my fuel. I have seen many great examples and resources on this forum of how the systems of a turbojet work (such as the diy turbines thread) but of course I have some specific questions.

My questions:
Do I need to do anything differently with the exhaust gases because it is a twin scroll turbo or would I just simply route the exhaust to both the turbine intakes?
Due to the fact the turbine intakes are on the same side as the exducer I know I would need many bends in the exhaust gas tubing from the combustion chamber to the turbine inlets. Would this put such a massive hamper on efficiency that it would not be worth building with the given turbo?
Is the openable thing I will call a "door" near the exducer important? What do I need to do about it?
I also have some questions regarding the construction of the flame tube and combustion chamber, specifically regarding how air should flow through the chamber and flame tube. Should all the air from the turbine compressor be forced through the flame tube by providing the only exit from the combustion chamber to the turbine inlet through the flame tube? Or is their supposed to be a gap around the flame tube at the exit of the combustion chamber?
I have heard of people using fire extinguishers as the combustion chambers outer shell. Can I use any fire extinguisher that is wide enough and long enough as the combustion chamber?

Thank you for the time! And if I'm an idiot for buying this turbo just tell me.

[racket]

Hi

LOL , yep , not the best turbo to have as a first build :-(

Gases to both turb inlet ports .

You should be able to have a straight in arrangement , no need for bends .

The wastegate "door" needs to be sealed shut.

All air through the flametube wall holes , the bypass type is obsolete and difficult to calibrate due to expansionary reasons .

If the fire extinguisher is big enough it'll do , with only a 60mm inducer and running propane , the flametube ID need only be ~104 mm , even some 4"dia thin walled stainless tube would work , outer can would need to be >5"ID , and as propane is such a forgiving fuel , the length need only be 12 inches, but don't try burning liquid fuel , save that for your next engine using a "proper"turbo ;-)

Cheers
John

[thehazard]

Hi there John

Thanks for the help you have cleared a lot of things up for me.

Though I do have question would be what you mean by a "straight arrangement" and not needing any "bends" since a combustion chamber could potentially obscure or at least come close to the exhaust from the exducer; if directly attached to the inlets of the turbine. I feel I would have to have at least have a bend in the tubing after the combustion chamber to avoid this, or would it be better not to worry about the exducers proximity to the combustion chamber due to a nozzle?

And one more random question, I was wondering what the standard tubing sizes are for the oil plumbing?

Again thanks for the help,
Levi

[racket]

Hi Levi

By "straight in arrangement" I meant having the combustor perpendicular to the scroll inlets .

You could always offset the ducting between the flametube centreline and the scroll inlets , you'll be needing a "creative" funnel arrangement anyway .

I'd simply have a large thick disc mounted onto the scroll that would be the bottom of the combustor , the two holes in the disc would be to one side allowing clearance for the jetpipe exhaust from the turb wheel .

With regards oil plumbing size , it needs to be large enough so that the design oil pressure is always available at the turbo oil inlet where your oil pressure gauge pickup is situated .

With cold oil and a small plumbing size its possible to have negligible oil pressure at the turbo even though the oil pump is creating pressure build , the plumbing friction uses up the pressure .

So depending on your ambient conditions and turbo size , line ID will vary , but I don't think I'd use less than 1/4" ID for your turbo , and it needs to be metal tubing at the turbo because of radiant heat from the scroll which will degrade anything else creating a potential fire hazard if the plumbing bursts .

Cheers
John

[thehazard]

Thanks again John, hopefully I'll be able to show my progress within the next few months due to your help.