T50! turbojet build

[mb300sd]

Edit: Turbo I received from the seller was actually a Cummis T50, not the T46, pictures below were taken from the listing and are not the one I received.

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Had the turbo sitting around for a while, but I'm finally ready to start building. Ordered a bunch of 20ga 304 stainless sheet and some 3/8 and 3/16 plate. I have an OMAX ProtoMax waterjet, and just bought the Harbor freight 3-in-1 slip roll/shear/press brake so fabrication should be fairly straight forward. Eventually I want to mount it on a custom fabbed kart, but I'm going to focus on the engine first.

[racket]

Hi

Welcome to JATO :-)

Looking forward to the build

Cheers
John

[mb300sd]

Flame tube design. Going to make it out of 4 pieces, since my waterjet only does 12x12" and it'll be faster to weld the pieces together than drill 80 holes in the thin stainless.

[racket]

Hi

Replace some of those 5mm holes in the Primary Zone with a few 10 mm holes to get air deeper into the flametube , those 5 mm holes only produce a cold air blanket against the wall , they don't penetrate very far

Cheers
John

[mb300sd]

Better? I'm using jetspecs to calculate the hole area, and sizing them to get an even number. It suggested 6mm as default on the primarys, so I went with 5.xx at first.

[racket]

What sort of fueling are you going to use ??

This will also have a big influence on design of the flamtube , especially the Primary Zone holes.

[mb300sd]

Diesel or Jet-A, with propane for startup.

[racket]

Will you be using a spray nozzle of vapourising tubes for thefuel ??

[mb300sd]

Spray nozzle, I ordered this one already, www.mcmaster.com/3178k47

[racket]

OK

Its an 80 degree spray angle , so you'll need to position the spray nozzle so that the actual fuel spray would theoretically contact the flametube wall where the row of Primary holes are situated .

If you intend having an end cap on the outer can that is also the end of the flametube then it would be adviseable to have some of the Primary air flow through holes located at the very end of the flametube to cool the "lid" underside, aim for around a third of the Primary air to go across the lid underside , the remaining two thirds through a single row of 10 holes positioned at the spray contact position.

Cheers
John

[mb300sd]

Hopefully final design. Thanks for the tips. Looks like the original 100mm guess at the primary holes was spot on Spent a good while trying to remember how to do the math before I found this. www.spray.com/sprayware/spray_coverage_calculator.aspx For an 80deg spray into a 6in pipe, it calcs 3.6in, adding the nozzle height, 100mm.

Also modeled up the top plate for the combustor with holes for fuel and propane injectors, and spark plug. I ordered a M14x1.25 nut and 2 SS 1/8 NPT couplers to weld in.

[racket]

Yep , that'll do the job :-)

Cheers
John

[lukenz]

Jan 26, 2019 18:19:45 GMT -5 racket said:

Hi

Replace some of those 5mm holes in the Primary Zone with a few 10 mm holes to get air deeper into the flametube , those 5 mm holes only produce a cold air blanket against the wall , they don't penetrate very far

Cheers
John

Hi John, as you quoted to replace “some” of the primary zone holes with a few 10mm holes I see mb300sd has replaced all of his primary zone holes with 10mm holes, is this the correct approach? My calcs from jetspec equated basically the same hole sizes as his so will use the same design for hole size and position. The only difference is his flame tube is ~100mm longer than mine.

Cheers,

Luke

[racket]

Hi Luke

Copy shamelessly if you find a design that works :-)

Cheers
John

[lukenz]

Thanks John, I guess I can use this design providing the turbo is the same specs etc.

mb300sd, what type of turbo is that your using?