ashdricky
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Joined: January 2014
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Post by ashdricky on Jan 20, 2014 13:17:38 GMT -5
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Post by racket on Jan 20, 2014 15:44:52 GMT -5
Hi
I remember this engine getting built , it was a long time ago :-(
You'll probably need to scale off the pics , turbine wheel is ~4.7 inch inducer with a 3.5 inch exducer diameter
Do you intend making something similar ??
Cheers
John
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ashdricky
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Joined: January 2014
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Post by ashdricky on Jan 20, 2014 15:58:48 GMT -5
Hi I remember this engine getting built , it was a long time ago :-( You'll probably need to scale off the pics , turbine wheel is ~4.7 inch inducer with a 3.5 inch exducer diameter Do you intend making something similar ?? Cheers John yes Sir, I would like to plan it out and calculate cost before I do so. How crucial is it that the flametube and combustion chamber are the exact size? what are the tolerances that we work within when creating something like this? |
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Post by racket on Jan 20, 2014 20:35:43 GMT -5
The main thing with flametubes is crossectional area to provide slowish air speeds for combustion , try and have it at least 3 times the comp inducer area , so for a 3.2" dia comp inducer ( ~8 sq ins) we'd need a flametube with ~24 sq inches of area , length will need to be long enough for combustion to have finished by the time the gases get to the NGV , combustion speed will depend on fuel atomisation and/or evaporation speeds etc etc , but ~3 times the radial width of the flametube should be sufficient
Cheers
John
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ashdricky
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Post by ashdricky on Jan 20, 2014 21:58:06 GMT -5
The main thing with flametubes is crossectional area to provide slowish air speeds for combustion , try and have it at least 3 times the comp inducer area , so for a 3.2" dia comp inducer ( ~8 sq ins) we'd need a flametube with ~24 sq inches of area , length will need to be long enough for combustion to have finished by the time the gases get to the NGV , combustion speed will depend on fuel atomisation and/or evaporation speeds etc etc , but ~3 times the radial width of the flametube should be sufficient Cheers John Thanks John, Just to clarify, when you speak of the flame tube area we are talking about surface area correct? and when calculating the radial width is the calculation the same as a conventional DIY turbojet, as I have noticed that the flame tube in this build differs in shape from others I have seen as the thrust nozzle passes through the centre of the combustion chamber.  |
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Post by racket on Jan 21, 2014 1:56:13 GMT -5
Yep , the crossectional area within the flametube , the annular flametube in your example will have an "inner wall" of ~5 inch diameter or ~20 sq ins , add on the 25 sq in of 3 times inducer and we have 45 sq ins for the outside wall or ~7.5 inch diameter , I'd probably go to 8 inches to give a bit more crossection , this will produce a "radial " with of the annular flametube of ~1.5 inches , multiply by the 3 times for length and anything over 4.5 inches should be OK , I'd go for 6 inches to allow a bit of a buffer in case combustion isn't as quick as desired .
It can be made bigger without any combustion worries , but don't go too small as combustion problems can occur :-)
Cheers
John
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ashdricky
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Post by ashdricky on Jan 22, 2014 19:20:31 GMT -5
We would start this project by selecting the turbine, and fabricate the rest using the measurements from that? Also the Large "box" under the the turbine which can be seen in photos 1-3 what is this?
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Post by racket on Jan 22, 2014 19:37:28 GMT -5
The large box is an oil tank for lubricating the "brass bush" bearings , theres an oilpump and filter there as well .
Do you intend using a similar turbocharger , or something different ?
Cheers
John
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ashdricky
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Post by ashdricky on Jan 25, 2014 14:23:30 GMT -5
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Post by racket on Jan 25, 2014 16:23:12 GMT -5
I wouldn't be using that turbo , its wastegated and probably has an "undersized" turbine wheel ....................you need a "free floating" non wastegated turbo with a "full sized" turbine stage.
If the seller can provide wheel dimensions it might be possible to use it if the turb wheel is big enough .
Cheers
John
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ashdricky
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Post by ashdricky on Jan 26, 2014 0:58:49 GMT -5
I wouldn't be using that turbo , its wastegated and probably has an "undersized" turbine wheel ....................you need a "free floating" non wastegated turbo with a "full sized" turbine stage. If the seller can provide wheel dimensions it might be possible to use it if the turb wheel is big enough . Cheers John Thanks John, What sized turbine wheel are we looking for? and as far as the wastegate, isn't that located on the hot side of the turbo which we will not be using anyway? I believe that the designer of the engine which I posted used a garret ST50 which in stock form has a wastegate, since we will be redesigning the hotside won't the wastegate be deleted in the process? Also what dose "Exducer" and "inducer" refer to? is this turbo acceptable for the project? Cxracing ceramic bearing turboor this one which has an 82mm compressor and a 67.8mm turbine ebay turboI'm trying to stay with no name turbos to keep this cost effective |
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wolfdragon
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Joined: April 2011
Posts: 287
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Post by wolfdragon on Jan 26, 2014 14:02:34 GMT -5
none of my ST-50, VT-50, or T46's have wastegates (all nearly identical in design and numbers, just different degrees of "open-ness" of the turbines when you look at them axially
no name turbos tend to be made of crap materials for the turbines - they like to melt in cars/trucks let alone as a GT
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Post by racket on Jan 26, 2014 17:49:03 GMT -5
Neither of those turbos are suitable :-(
The smaller automotive turbos "generally" have undersized turbine stage , hence the small A/R number for the turbine stage , this generally means its fitted to a too small turbine wheel , we need turbine A/R size around 50% bigger than the compressor A/R .
Take "wolfdragon's" advice about no name turbos , ............."we gets what we pays for" ............they can be used but they need to be treated "softly" , no extreme temperatures or high "boost" pressures (P2) from high tip speeds ..............their potential for power production is limited
Relatively cheap ST/VT 50 turbos are a better proposition as they'll have "adequately" sized turbine stages as they were "free floating" turbos .
Most older large truck turbos were free float'ers , so can generally be made into gas turbines without problems .
Cheers
John
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ashdricky
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Posts: 8
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Post by ashdricky on Jan 26, 2014 22:12:34 GMT -5
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Post by racket on Jan 27, 2014 2:17:08 GMT -5
Cores could need a full rebuild , this gets expensive if a new turbine wheel is required .
The others might be a possibility if you ask the seller for wheel and A/R specs to determine suitable sizing
Cheers
John
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