Why oh why wont it run???

[nickyracer390]

Hey all,
after quite a long time i am back on my gt project.

Not having much sucess with my first try i have totally re-made my cc and ft exactly to the jet-specs program, also adding adjustable op, P2 and TOT measurement i thought this time i would be susessfull.

Not being too egar to just bolt it together i have done quite a few bench tests of the cc setup ending up with a good burn with the blower and gas fully cranked the burn sat well within the primary zone and very stable i thought.

Today i assembled it all up and attempted a run, started ok and started spinning up, P2 gets to about 10-11 psi and i cant do anything, i give it more gas and it flames out, i give it less and it slows.

Question, is it possible to have a turbo that is not setup properly to support a gt, eg if the comp is larger than the tubine would it make it hard to build/make run properly?

Thanks in advance to any1 who can take the time to help, i just wanna get it to run, self sustain and not destroy my turbo!

[racket]

Hi

Does the P2 gauge bounce around at 10-11psi ??

What TOT do you have when it flames out ??

What fuel are you using ??

What sort of fuel injector , its design , positioning etc etc ??

What sizes are the compressor wheels inducer and turbine wheel exducer ( holes in and out of the engine) ??

Do you have a jet nozzle installed ??

If so what diameter nozzle opening ??

We'll get it sorted :-)

Cheers
John

[nickyracer390]

ok,
P2 seems pretty stable, and smooth as it spools up, unless i give it too much fuel or try to remove the blower it flutters around a bit and drops.

TOT sits around 650-700c, when it flames out it obiously rises quickly.

using propane

Its a home made injector, sorta looks like a bullet approx 25mm in dia with 2mm holes drilled around the side fanning out towards the primary holes....

i forget the sizes of the inducer/exducer ill get back to ya on that.

i have removed the nozzle altogether, although it was quite a bit larger than the exducer amyway.

i will get those sizes and a pic of the injector and report back.

with the flame tube, during testing i used a screwdriver to bend the primary holes to give that cheese greater effect but it made the flame spin way too much... then i bent them back ultimately now the holes are bigger, could this be the problem?

thnx
Nick

[racket]

Hi Nick

Generally with propane its either the fuel injector or the turbo configuration that is the problem , occasionally the propane tank if its got some sort of "safety" device inside it .

If the propane injector only has "radial" holes , NO axial hole/s, then it should do the job .

If the turbo has an "undersized" turbine stage then there can be surge problems that will cause a flameout , I'll need those inducer/exducer sizes .

A 650 - 700 C TOT is very high for an engine without a jet nozzle fitted , especially at 10 psi P2 , it should be <500 C .

Could you verify whether or not your propane cylinder has a safety device , .........................you could test to see if it does by doing a discharge test in a safe place , simply open the cylinder valve as far as possible to see if theres any automatic cutoff valve installed , our engines use a lot of fuel , much more than the family BBQ .

Cheers
John

[nickyracer390]

hi john,

I did a test on the propane tank, it seemed fine, i opend it fully for about 5 seconds with no sighn of restriction or cutoff.

i did some research on my turbo, it seems to be off a r33 skyline, RB25dett, a T28 wich from what i read is a hybrid turbo, it also said its a bb turbo with a ceramic turbine wheel.
markings on the comp housing i 45V3 and on the turbine housing 16V. some one also said it is a very close match to a T3 .60 if that means anything to u....lol im a bit of a turbo noob!

I measured the turbo today.... Inducer ~48mm exducer ~43mm

i included a pic of the fuel nozzle, am i correct in reading there should only be radial holes in it, i have 6 radial holes and 6 axial holes (sorta) fanning out on a 45deg angle, should i weld the angled holes up?

Cheers
Nick

[racket]

Hi Nick

Those inducer/exducer sizes aren't encouraging :-(

May I suggest you do a surge test with a piece of string SECURELY fixed so that the end of it just can't quite touch the comps inducer , with the engine running the string should indicate a steady inflow of air , but if the string shows any sign of "in and out" indicating a flow reversal of intake air , you've got surge and is probably why she is flaming out .

As for the fuel injector , radial holes only .....................weld up the angled ones , they'll be shooting the propane down the flametube and could be the reason for the excessively high temperatures , you need to have temps as low as possible to minimise the effects of the inducer/exducer size inbalance .

Give those two things a try and let us know the results :-)

Cheers
John

[nickyracer390]

hey,

with the surge test i did that with my GT 1.0 and yes it was having some major surge problems, hence y i remade the whole CC. it seems now its a lot better and only gives a slight fluttering when i give it too much fuel.

In saying that it seems very very touchy with the fuel, last week i actually got it to self sustain for about 5 seconds but then it started to flutter and flamed out by itself... (could be coz of the angled axial holes in the injector)

when i first tested the CC i had a dramatic swirling effect going on with the flame only burning about 2" wide in the center on the FT, i noticed that it was keeping everything very cool, but had a lower range of throttle- ability, maby i shoud go back to that desighn......

i will try a couple of things and let u know....
also i said earlier that after bending the primary holes back and forth they r now lager oval shape, should i weld them up and redrill?

Thnx
Nick

[racket]

Hi Nick

Because of the undersized turbine stage the mass flow will be lower than "design" , but as long as you still maintain the Jetspecs ratio of hole areas between primary , secondary and tertiary the flametube should operate , propane is very forgiving as a fuel , its generally something else that causes the larger problems, you don't need swirl in the flametube if using a Jetspecs sized flametube and a propane injector with radial holes,

........................how is your delivery tube orientated with respect to the combustor can , is it at 90 degrees or a swirl inducing tangent .

Also , what diameter is your flametube as well as the primary zone hole sizes and number ??

Cheers
John

[wolfdragon]

Also, where does the delivery tube from the compressor come into the flame tube plenum, is it nearer the primary or tertiary zone?

My original had the wrong type of fuel delivery nozzle AND a tangential delivery at the primary end (actually a bit ahead of the primary zone).

Only ever ran propane, regardless of my tweaks, that design still only made one hell of a flamethrower when I started getting close to anything resembling the mass air flowrate of a 2" compressor inducer, which is about what you have.

I kept it around since it is a handy heater... The new design is still being played with in CAD...

[turbochris]

I went though this my turbine had a smallish flame tube and I had to make the total hole area a little on the small side. My experience is an open flame tube runs like what you're seeing, a closed tube will be stable but run hotter. Start out again w smaller/less holes or try putting a hose clamp around some holes in the pri zone to partially cover them. Propane injector? I just have a hole in the top where the propane comes in w a small plate over it to make the propane stay in the top of the CC. No zozzle, ran a TO3 sized turbine on liquid propane from a small camping cyl at full rpm.

[nickyracer390]

ok john,

my delivery into the CC is at a angle with the intent of makeing the air swirl around the flame tube, although i found it spun too much and easily flamed out on my CC bench test, i put in a small difuser in at the entry point of the CC wich seemed to slow the air down and gave a flame contained in the FT even at !00% throttle.

FT setup is 150mm dia, ~300mm long with 19 holes @ 6mm,
and i think 5 @ 10mm and 5 @ ~ 16mm, all made as close as i could get to the jetspecs!

And Wolf,

the entering air is right on top of the primary zone at the far end.
so r you saying i should move it to another location?

P.S any tips on uploading pics, it wont seem to work 4 me...

[wolfdragon]

Well with the air coming into the top, the typical flow is somewhat axial in that aside from going thru the FT holes, the air will just rush around the outside wall of the FT and out the back. Not a whole lot of the mass goes into the core of the FT and in a sever case like mine, it just dragged the hot zone down the FT with any appreciable amount of air going through the setup.

If the air source is on the tertiary zone side, or after it, then you get something called a reverse flow combustor, which for our purposes, has several pros in the design that help keep things in check.

Don't get me wrong, I have seen several top end air sources work just fine, but there is something to be said about the bottom end source and many of the very crude GTs on YouTube working the first time...

[nickyracer390]

OK, I did a few mods and tried agan to little progress, ifact it was worse....

I welded up the angled (axial) holes in the injector and now only have radial holes in it.

welded up all the holes in the primary FT and started again, put a total of 27 5mm holes in three rows of 9, only put 18 to start with and added the last 9 3 x 3 till i got a nice looking, even burn, (took me about 7 or 8 goes b4 i was happy).

Bolted it all up and had another crack!
Bloody thing was worse, it could only boost up to 4-5 PSI, any more and TOT would rise quickly, Had the turbine red hot 4 a few breif seconds just to see if it would start flowing enough to overcome it but no.

Im thinking my injector is still not right, the holes are 1/8th in size and staggerd around the perimiter with roughly 3-4mm from hole to hole......? too many maby, or too big?

I guess wolf, the next thing is move the inlet towards the other end, do you recon inbetween the tertiary and dilution zones is best?

Thanks for your help guys, although im just about ready to bin the whole thing and stick to PJ's, atleast i got them to run well! ;D

[racket]

Hi Nick

5mm holes in a 150mm flametube is only going to cool the wall , you need to open up some of those 5mm holes to at least 8mm to get some air into the centre of the flametube , I'd suggest 3 of the 9 holes in each of the bottom 2 rows of 5mm holes , so 6 X 8mm holes , leave the top row as 9 X 5mm to provide wall cooling .

How many1/8" injector holes do you have ??

Too many and too large the holes might produce a core of propane in the flametube with those 5mm wall holes unable to penetrate into the propane , combustion might not commence until the larger secondary or tertiary holes finally penetrate that propane core .

1/16" holes and a dozen of them should be adequate

Cheers
John

[nickyracer390]

Hey all,

Well I opened up some of the holes like u said, it did seem to liven it up, got a nice blue flame nearly all the way through, but still seemed to be getting very hot on the backing plate, I decided to remove the small deflector I put in to slow the spinning of the incoming air which seemed to push the flame in off the FT wall and greatly reduced the outgoing temp.

Again put it all together with bugger all results....
could only get the P2 up to about 2psi, then TOT would blow out in a hurry, I kept it spooling up hoping to overcome the hot temp but no, didn’t even really get close to self-sustaining.....

Think I’m gonna start shopping around 4 a new turbo as this one is nearly bugged from all the hot starts I guess....
any suggestions about what would be the ideal turbo to get, wanna keep similar inlet size so I can use the setup I have now, I’m not worried about power or thrust potential, just want something that will be quite 4giving to get it to run.

Might have one more go with the FT as it is now just with my alternate injector, at least with that one I got close to SS!

Thanks
Nick