The vast majority of cheap turbos in the 2-2.5" inducer size are for autos where the use of a wastegate is desirable to bring on boost low in the engine rpm range , this entails the use of a smaller turbine stage with a lower moment of inertia to increase rotor acceleration rates , this is OK on an IC engine but not good for a jet engine , the pistons in an auto engine can force the hot gases through a small turbine stage at much higher pressures than what is coming out of the compressor , we can't do that , our turbine stages need to "voluntarily" swallow those gases .
You've been given the requirements for a turbo that can be turned into a jet engine , they are "non negotable"
Welp, thanks for your guys help, after doing a bunch of research and looking up turbos, i realized that the diesel/ big truck turbos are it however due to my budget at moment, i gotta go with this cheap t3 t4 turbo i found on ebay, i couldnt afford the proper one at the moment but i will make a really good removable combustion chamber that i can use when i can get a better turbo, but for now i went ahead and bought the t3 t4 gt3582 one on ebay becauswle i guess i got a little confidence boost from seeing some t3 t4 turbojet engines running fine on youtube so ill just use that for now, not sure if i shoukd tweak the flame tube setttings a little different for this like maybe make the lentgh of the flame tube the whole 6x the inducer and than ad an extra maybe 3in of lentgh on top of that for the cone down to bolt to turbine shroud, not sure if thats better, any thoughts about that being im gonnna use a t3 t4? Has anyone put extra cooling holes that equall greater than 50% of the inducer area? I seen a few diff flame tube desines whwre people put the big holes and than put a bunch of tiny holes righr after like they put a bunch of primary holes after the big cooling holes, not sure if they had the whole sum of all those holes at 50% the area or if maybe they wemt to 60% or something, it sure looked like allot of holes. This is the turbo im working with in the pics and i found a flare that bolts onto the turbin inlet shroud that i can weld the flame tube onto
After uploading the pics i think i bought the wrong size turbine inlet flange, it says its for a t4 :/ oooops i was gonna weld my chamber to that and bolt it on. And i got a little 4 bolt pad for tge exhaust that ill weld a pipe to the end of that.
For this t3 t4 setup maybe if i can bleed of some pressure from the nipple that comes off the side of the compressor outlet tube, maybe since the compressor is allot bigger than the turbine, maybe bleeding off some air can aid in better operation to make up for the size differences? Maybe" but just a guess, i dont know anything
Post by dieselguy86 on Aug 17, 2022 14:44:43 GMT -5
In this case could a bushing/sleeve be fitted in the comp cover inlet to effectively cut down the inducer area? It's not a good fix, but would atleast help move things in the right direction for a first start.
DO NOT bleed air , your temperatures will go too high , small turbos , and this is considered a small turbo , have poor turbine stage efficiencies which limit "experimentation" , comps are efficient but turbs not so , stick to basics , use Jetspecs, DON"T experiment with holes , Jetspecs was made because guys made bad combustors using unsuitable flametube diameters/lengths/holes , if you want to experiment , you're on your own :-(
Yep , it needs the larger housing to have any hope "performing "
With the 0.63 housing, using the Garrett turb map , the corrected flow is only ~22 lbs/min which equates to a tad more actual flow if using a 788 C - 1450 F for the turb inlet temp , ~23.5 lbs/min .
But on the comp map at 2:1 PR , 23.5 lbs/min is at a pretty poor 65 or so percentage efficiency , and with the turb stage topping out at 70% effic , the turb will need all its power to spin the comp .
With a 788C- 1450 F and 5% drop through the combustor , our 2:1 PR becomes 1.9 going in , the comp temp rise at 65% is ~97 C degs needing ~85 degC drop through the turb , which at 70% effic will need a ~1.62 PR , leaving only ~1.17 coming out , thats about what the unrestricted exhaust velocity represents .
The engine will run , BUT , not a great performer, BUT with the larger 1.06 housing that 22 lbs/min rises to 32 lbs/min Corrected , a much healthier flow , still not ideal but at least the comp is getting into the 70's% efficiency range which would allow some "backpressure" in the form of a jetnozzle to be added .
So in a nutshell basically find a turbo the same size as the one i got 2.4" inducer but just make sure the turbine says that it has a bigger a/r than it currently is, like mayne one that says 90+ a/r? Ill do that when i get more money ill buy a good diesel one but for now i guess im just going to concentrate on making a really good flame tube and chamber so when i do get a better turbo ill just swap it over to that one, allready got a good oil system set up and cooling radiator i have chillin in a bucket of water, going to see how this turbo for now performs, the one i seen on youtube seemed to be running good, not sure how reliable it was and if it was producimg lots of thrust but did sound like it was running fine. So i got my 5" fire extinguisher the other day, stripped all the paint off, cut the holes with 29 1/4 drill bit holes, 8 3/8 holes, and 8 5/8 holes like jet specs says on there prefilled out sheet i found online for 2.5" inducer, cleaned up and the sharp edges the drill bit left on the inside so it wont break off and fod out the turbine, now im trying to figure out what bigger container to use, i cant findna 7" fire extiguisher and i think a 6.5" diameter would be better around the 5" one but maybe harder to find in that size, anyone know a good place to get a tube that size without having to roll one, if it come down to that i could do it but will be kinda hard because im using a fluxcore welder, i know i need to get a tig for this kinda work, i have succefully rolled a tube and used the flux core and filed it off smooth but just would rather find a premade one, was wondering about an oxygen tank but those are really expensive.