Back again..!... The GT6041 powered "Green Beast"..!

[enginewhisperer]

might be about time to replace those brake pads

[smithy1]

Sept 8, 2014 19:57:09 GMT -5 enginewhisperer said:

might be about time to replace those brake pads

Not such a silly idea Andrew....I have some motorcycle pads at home which look close-ish, I'm sure I could "doctor" them to fit. The rear brakes pads are fine and have plenty of "meat" on them....the front's are a bit ordinary though..!

I actually have two car shows to go to this weekend, one at Liverpool on Saturday, although I might be quite limited with available room at this one as it's in a small-ish car park...and on Sunday I have one quite close to home at Leumeah...this one should hopefully allow me to have a bit of extra room to throw some flames around... You're welcome to pop out to either or both if you wish Andrew.

Cheers,
Smithy.

[enginewhisperer]

hmmm I may have a couple of reasons to head out Campbelltown way, so I'll keep you posted.

[smithy1]

Hi Guys,
Finished fitting up the two Bosch 044 A/B pumps in parallel yesterday evening, I fitted an inline check valve in the feed line to eliminate the possibility of tailpipe pressure pushing the fuel back to the tank when the A/B is not in use. Due to lack of daylight I have yet to finish the wiring and need to test them to make sure they actually work together, will do that this afternoon after work....the Hot-Streak pump will then be fitted and plumbed/wired in, most of the plumbing is there for it, just had to swap pumps over and fabricate a new feed line for it. I'll try to remember to take some picks when it's all done.

Cheers,
Smithy.

[racket]

Hi Smithy

LOL......I can see you're itchin' to start spraying fuel from those two 044 pumps :-)

Yes , pics please

Cheers
John

[smithy1]

You're not wrong John....I've got a nervous "twitch" in my eye as we speak..! I can't see too many dramas with the setup...I just need to check thoroughly for leaks etc...and to make sure I've got enough fuse in the fuse holder for the twin pumps which are wired together, a couple of short pump test runs will answer that for me I suspect.


Cheers,
Smithy.

[smithy1]

Hi All,
A photo or two of the "Twin" afterburner pumps and the single Hot-Streak pump and it's solenoid. All plumbed in and wired up, I did a quick test of both systems and they work as intended....just a matter of doing the "real thing" on Saturday..

Just need to get a few more suitably sized hose clamps and it'll be finished... I forgot to buy some . I'll fit some of that black wiring conduit also when I get "roundtuit"..  That should clean things up nicely.


The "Blue" pump is obviously the Hot-Streak pump with it's associated solenoid shown at left.

[racket]

Hi Smithy

Sweet

Thanks for the pics .

Cheers
John

[smithy1]

Hi All,
A small update....The 6041 powered "Green Beast" is all back together and ready to go....and will be packed into the van this afternoon ready for the charity car show at Liverpool tomorrow.
The cheap rpm sensor I ordered has arrived this morning, I probably wont have time to get it "Doctored" & fitted as per Anders' method before tomorrows car show but I will take it with me and take some rpm readings just for interest. When I get the engine up to idle @~4.5-5psi P2, I might take the rpm readings and see what she actually idles at rpm wise vs P2 and then compare that to the comp map for reference. If possible I will also take some readings at various P2 settings such as 10, 15, 20, 25, 30 and most notably at 35psi P2, this is where I have the engine max throttle set at the moment....this will allow me to then make a P2 vs rpm plot and adjust maximum fuel flows to suit....I suspect it will closely follow the comp map as supplied by Garrett.

I'm also interested in the self-sustain rpm, once up to a stable idle I might slowly lower the rpm via the "idle tap" and take readings etc, obviously the engine will start to struggle and temps will rise if this is too low so I'll keep my good eye on the EGT while doing this ...none of this really means anything of course, it's just for interest. I'm guessing the 6041 will happily spin away at under 20,000rpm, this will be testament to the fine combustor and fuel injection John has built...there's very little in the way of drag on the 6041 which will help greatly..... time will tell.

I will also do my best to try and remember to take some photos & Go-Pro video this time .

Cheers,
Smithy.

[smithy1]

Hi John,
I've been having a look at the GT6041 compressor map and I'd like your clarification if I may...

Currently I have the maximum P2 set to 35psig, I'm thinking this will be approximately 66-67,000rpm-ish with a pressure ratio of ~3.38....flowing ~2.66lbs/sec...does this sound reasonably correct.?? I just want to make sure I'm reading it correctly.



Cheers,
Smithy.

[ashpowers]

Hi Smithy, yes, that would be a correct interpretation of the map. There may be some variations in how the compressor in your engine works compared to that of the map though since that map is based on a specific compressor housing which you aren't using.

[racket]

Hi Smithy

Yep ,that flow at ~66,000 rpm sounds OK

The 1.47 A/R turbine housing is a tad "tight" if we want to run very high T I T s , I designed for a max T I T of 900 C , and even at that relatively "low??" temp the turbine stage will keep mass flow probably a bit to the lower, surge side, of ideal flow .

When I did the calcs for 70,000 rpm and a 3.65 PR the extra pressure ratio helped with getting a bit more mass flow through the turbine stage because the PR across the turbine stage needed to be higher at ~2.4:1, the "Corrected Flow" on the turb map went up to ~93 lbs/min which worked out at an actual flow of 165 lbs/min - 2.75 lbs/sec ( 75% of an Allison C20 engine's mass flow ) , there should be ~11psit for the P4t in the jetpipe ............anything over 10psit is a bonus for a DIY engine

Generally theres a rpm change when the A/B ignites, but I'm not sure just how much of a difference there will be with the 6041 due to the choking of the turb stage as well as the comp inlet at elevated rpm , you might need to do a bit of step by step increases with the fuel volumes to the combustor , my gut feeling is that you have a good chance of running the engine with the afterburner alight at 70,000 rpm and not exceeding the maps ~78,000 rpm if the A/B is suddenly blown out.

................heh heh , just keep adding fuel until you hit 78,000 rpm, then light the A/B and see what sort of rpm drop there is

Being a boreless wheel and "new" , it'd most likely survive a momentary 85,000 rpm ( tip speed ~ 2060 ft/sec)

Have fun .............and don't forget the camera .

Cheers
John

[smithy1]

Hi John & Ash,
Thanks for the info....Pretty sure the A/R of 1.05 is cast into the comp housing I have...so it should be pretty close I hope..! When I play with the P&W J-60 powered jet dragsters... and even the Westinghouse J-34's there is a considerable "droop" of rpm upon the hit of the A/B, I had to "doctor" the FCU's to recover and maintain >100% during afterburn otherwise the poor old things wouldn't get moving properly till after half track....by then it's a bit too late....your opponent is already gone..!

And john....I have no intention of running her to 85,000rpm... LOL..!

Cheers and thanks again guys,
Smithy.

[racket]

Hi Smithy

LOL.......that thick comp housing will hold the bits inside if theres an unfortunate incident ;-)

Have fun today .

Cheers
John

[smithy1]

Hi All,
Had a reasonable day today at the car show.....plenty of fuel for the A/B happening and plenty of Hot-Streak.....the only issue is that she won't really hold a flame in the pipe at the lower rpms...I'll give it another go tomorrow when Andrew is on hand to help out. On a positive note the "Beast" lights off nice and easy and I'm only seeing temps of ~650c during start....I must be giving it plenty of blower..! Once settled to a nice stable idle I'm seeing ~460c...which is on the money.

John, I took a couple of rpm readings at idle and she's showing ~25-26,000 which is just a tad lower than I expected at ~4.5psi P2 but not too far from the mark, all in all a good result for the day...and I didn't break anything..!

I have another car show tomorrow so I'll get Andrew to take some readings if he's up to it...

Here's an ordinary video:

youtu.be/DBoUJJ4mEgY

Cheers,
Smithy.