Diy turboshaft engine

[racket]

Hi Aaron

Once the gases start to spiral in they'll keep going, the radial gap isn't a problem, the NGV may have been designed to be used with different configuration/sizes of wheels to suit different engine requirements.

Whats the inside of the scroll look like , does it "fit" the wheel closely around the exducer portion ??

Cheers
John

[turboron]

John, he appears to be missing the shroud around the radial inflow turbine if you review the previous pictures. It must be a separate piece which he did not get.

Thanks, Ron

[racket]

Hi Ron

Yes , now you mention it , Aarons first pic of the turbo has the wheel floating around in a pretty bit empty space at the turbo outlet , some sort of shroud insert missing as you said , maybe that scroll is used for a lot of different configurations of hot section .

Cheers
John

[azwood]

Yeah as you guys said I think there's something missing from the turbo a shroud of sorts that's something I'll need to make go the area of the ngv it says 5583.31cm2 I need 32cm2 I'll double check.as John said I can blank every 2nd or 3rd passage. the mount blocks are welded on the back so I guess I can tig it ok I'd hate to see one of the blanking plates go through the wheel at speed.anyhow I have a good idear of what I need to do now thanks guys.

[racket]

Hi Aaron

Initially I'd make the throat area a bit bigger than "theoretical" just in case theres a bit more restriction than your jet nozzle , your temperatures should then be a tad lower than at present, which is a good safety measure for initial tests of the freepower , it'll be easy enough to then blank off extra passageways until you restore your temps.

Large turbo NGVs can be made of just ordinary stainless castings as the running temps are fairly modest.

Cheers
John

[turboron]

azwood, perhaps when you machine the new shroud insert you can restrict the flow out of the IGV to form a new throat of a smaller area. You would need a radial tapered section that starts at the full axial opening of the IGV ends approximately a .5" before you get to the radial inflow impeller exducer. In other words, the last .5" would be a vaneless flow velocity increaser (due to the area reduction with decreasing radius) and flow straightener. What is the axial length of the IGV opening and what is the axial length of the exducer blade at the outside diameter? How will the shroud insert be attached? Is it trapped by the scroll?

Thanks, Ron

[azwood]

Dec 22, 2018 21:35:15 GMT -5 turboron said:

azwood, perhaps when you machine the new shroud insert you can restrict the flow out of the IGV to form a new throat of a smaller area. You would need a radial tapered section that starts at the full axial opening of the IGV ends approximately a .5" before you get to the radial inflow impeller exducer. In other words, the last .5" would be a vaneless flow velocity increaser (due to the area reduction with decreasing radius) and flow straightener. What is the axial length of the IGV opening and what is the axial length of the exducer blade at the outside diameter? How will the shroud insert be attached? Is it trapped by the scroll?

Thanks, Ron

For the new exducer its pretty much straight . theres no wheel taper which is strange I suppose I could machine the wheel a little but not sure it would make any difference to performance. But as for making it all fit together I was thinking mount the ngv to the backing plate I have its 20mm thick I will turn some meat off it but then the scroll will be two pieces one part will be fixed with the ngv the the backing the other will be fixed to the exducer section and the two will bolt together in place this way I can access everything easy the exducer could just be a thick wall pipe section machined out to size nothing fancy Maybe a few dowels to locate to two part's.

[racket]

Hi Aaron

Is the "back wall" of the turbine wheel smaller in diameter than the exducer ??

It sorta looks like the back wall is the smallest , then an angled increase out to the exducer , its certainly a strange beast of a wheel

Cheers
John

[azwood]

Dec 22, 2018 23:22:40 GMT -5 racket said:

Hi Aaron

Is the "back wall" of the turbine wheel smaller in diameter than the exducer ??

It sorta looks like the back wall is the smallest , then an angled increase out to the exducer , its certainly a strange beast of a wheel

Cheers
John

Yeah the back walls smaller not bigger like normal strange indeed.at this point I'll just make the shaft tunnel and scroll then work out the exducer and everything

[turboron]

azwood/John, the pictures on December 13 (page 55) frame the dimensions. The IGV axial length is approximately 40 mm and the exducer blade height is approximately 10 mm. The exducer outside diameter is approximately 155 mm. The inside diameter of the IGV can be estimated from the post yesterday on page 56 as 1.2 times the exducer diameter or 190 mm. The area ratio now can be calculated as .785(190)(190)/(.785(155)(155)) or 190(190)/155(155) = 1.5 reduction of area. The cylindrical area at the exducer exit is 3.14(155)(10) = 4867 sq. mm. If we use John's required 3421 sq. mm required throat area to calculate a new throat at 1.10(155) diameter we get an axial cylindrical passage of 3421/((3.14)(1.2)(155)) = 6.38 mm. I don't know what happens to the velocity triangles. Perhaps John can comment. azwood, you should measure all these dimensions so we can refine our calculations.

Thanks, Ron

[azwood]

Dec 23, 2018 8:33:18 GMT -5 turboron said:

azwood/John, the pictures on December 13 (page 55) frame the dimensions. The IGV axial length is approximately 40 mm and the exducer blade height is approximately 10 mm. The exducer outside diameter is approximately 155 mm. The inside diameter of the IGV can be estimated from the post yesterday on page 56 as 1.2 times the exducer diameter or 190 mm. The area ratio now can be calculated as .785(190)(190)/(.785(155)(155)) or 190(190)/155(155) = 1.5 reduction of area. The cylindrical area at the exducer exit is 3.14(155)(10) = 4867 sq. mm. If we use John's required 3421 sq. mm required throat area to calculate a new throat at 1.10(155) diameter we get an axial cylindrical passage of 3421/((3.14)(1.2)(155)) = 6.38 mm. I don't know what happens to the velocity triangles. Perhaps John can comment. azwood, you should measure all these dimensions so we can refine our calculations.

Thanks, Ron

Wow ok let me just take a second to understand all that very in depth answer. Thanks

[azwood]

Had to put down the welder and finish my bar so I have somewhere to relax after a long day.

[azwood]

After looking at the size of the stock ngv and how big it would all end up with the scroll added I decided to just make a new one it has the same angle but less vains the area adds up to 40sm2 just up from the 34cm2 of my nozzle next job is to get it in the lath and bore the shaft tunnel and true everything up.

[azwood]

Did a rough calculation on the wheel got 468sm2 tryed to work out the rpms it would turn and got 18.7k.not sure I have this correct but lol it looks right

[azwood]

Got some lath time today a friend has a nice old rigid machine been working on the power turbine parts and enjoying the process