"Fat Boy" 12/118 thrust engine

[gidge348]

Nov 23, 2015 18:32:20 GMT -5 racket said:

By using a shallow angled centre punch in the drill chuck , and a suitable "edge" to force the tube against , if the depth stop is set on the drill its easy to force the centre punch to a depth that leave an exit hole of ~0.5mm dia , leaving only a very small amount to be drilled out , repeatability is good , so only seconds per punching, and about the same time to cleanout the hole with the 0.7mm drill in the Dremil .


Cheers
John

That's a clever trick John, I will have to store that in the old grey matter for when I need to do some accurate small drilling.

Cheers
Ian

[racket]

Hi Ian

LOL, it was a lack of good hand/eye coordination, from my degrading grey matter ,that forced me to find a way to get accurate centre pop marks for drilling the injector holes , it was a happy consequence of using the drill press and its extra force that resulting in me noticing how the centre punch could actual make the required hole virtually without drilling , I like to open out the hole to exact size as it helps to align and hold the needle during the silver soldering process.

Fuel manifold was finished off this morning , tested with LPG to check for leaks and consistent flows from the injectors, all OK,............... I want to do a full power flow check of the complete manifold using kero, spraying into a bucket to check theres no problems before finally accepting the part is fit for use .

Cheers
John

[racket]

Hi Guys

Testing of the finished fuel manifold produced a flow of ~2.1 - 2.2 liters per minute at a delivery pressure of 35 psi , entire pump flow , bypass/dump closed, pump is max'ing out , might need to fit a bigger EFI pump as the one on the test stand only flows ~2.5 lpm with nil pressure .

Fuel manifold looks pretty impressive when flowing those amounts , kero squirting out everywhere in a fine mist after hitting the walls of the bucket.

Sorry , battery flat in camera so no pics.

Cheers
John

[smithy1]

John,
I have a spare 044 "clone" pump you can try, I can shoot it up to you in the next day or two if you like, you'll need to get the fittings for it though...I've tested it to 100psi and still pumping strong. Pulls ~14-15amps...-ish..!

Cheers,
Smithy.

[racket]

Hi Smithy

100 psi , how did you get it so high , I thought the 044 only went to ~72 psi ??

Hang onto it for a while as this pump will stop me grossly over fuelling the engine , if needed I'll take up your offer :-)

Cheers
John

[smithy1]

Nov 25, 2015 16:32:40 GMT -5 racket said:

Hi Smithy

100 psi , how did you get it so high , I thought the 044 only went to ~72 psi ??

Hang onto it for a while as this pump will stop me grossly over fuelling the engine , if needed I'll take up your offer :-)

Cheers
John

I believe you've seen my RR250 FCU test rig..? I just plumbed the pump into the fuel & power supply on the rig, connected a gauge and slowly closed off the outlet, as the pressure builds I can monitor the current pull and outlet pressure.....the pump's internal by-pass appears to be set at ~100-110psi. I have three spare 044 clone pumps sitting in the shed at home, I might bring them into work and take some pics for you....

The "Beast's" original gas producer pump runs to ~90psi with the outlet closed, I was checking it out just the other day while trying to diagnose my falling RPM/P2 issue. 

Cheers,
Smithy 

[racket]

Hi Smithy

Yep , I remember your test cell with envy ;-)

Thats good news about the higher pressure capability , I'll certainly be looking at relieving you of one of those pumps once the engine fires up and I can't get enough fuel for full power.

I really need to build myself a new test stand with thrust measuring capability , I probably will if the 12/118 actually works as I'd like to spend some time getting it fully developed , an 044 pump rather than this old Volvo pump I got from the wreckers 15 years ago would be the way to go .

Pics of the 044 pump being tested would be great , especially being tested to your exacting conditions rather than what we read on the Ebay ads with their dodgy data .

Cheers
John

[smithy1]

I'll certainly have a go at it...the 044 pumps I have are just cheap clones but they seem to work ok so far.

Cheers,
Smithy.

[racket]

LOL...if those clones can flow 2.6 lpm at 90psi , I'll be laughing .

The theory give me a T2 of ~175 deg C at my "design" 3.5:1 PR , so a 725 C rise in the combustor to get my 900 C for the TIT , this should require a theoretical 50 : 1 A/F ratio.

With a calculated air flow of 3.6 lbs/sec , or 216 lbs/min , we need 4.32 lbs/min of fuel ( ~260 lbs/hour) , about the same as the Allison 250 .

4.32 lbs of kero is ~2.45 litres , so if 95% burn effic , thats my 2.6 lpm , thirsty bugger , I don't wanna even go to the A/B figures .

I'll look forward to hearing about your testing .

Cheers
John

[smithy1]

260lbs/hr..!! Farrk ....You're right the RR250 C20B max fuel flow stop is set at 285lbs/hr but it rarely gets near that...normal flow rates during N1 governing are in the 230lbs/hr zone-ish. The C20B GP is good for ~900hp just to get 420shp out of the free power turbine....but it does have a pretty decent comp ratio with it's 6 axial stages plus impeller.

Thirsty indeed....At those fuel flows I'm thinking your 12/118 gas producer would be needing a big bunch of hp just to run itself at full noise...? Let alone make any usable thrust..! I'd like to see some numbers for that...! This is going to be a "substantially powerful" engine....really looking forward to seeing it run.

Cheers,
Smithy

[racket]

Hi Smithy

The comp will have a temp rise of 160 C degrees at the relatively modest pressure ratio , requiring ~98 HP per pound of air/sec , so the poor old turbine wheel will need to produce ~350 HP to turn the comp around, or ~30 ft lbs of torque at 60,000 rpm going through the 7/16" dia quill .

Heh heh , your GT6041 comp is consuming ~112 HP/lb/sec at full throttle , so ~305 HP from its turb wheel .

Yep , they're starting to get into some serious horsepowers in a very small space .

Cheers
John

[racket]

Hi Guys

Fuel manifold finished and securely mounted along with the preheat LPG manifold feeding gas to 4 of the lower evaporators only, to every second evap, to prevent "explosive" ignitions if gas is fed to all evaps .



Plumbing comes out through fitting for air sealing purposes , other threaded holes for P2 and T2 probes.



Cheers
John

[racket]

Hi Guys

This weeks job has been aligning the starter motor onto the bellmouth , so a jig was made up to locate into the comp recess in the diffuser wall


Secured by 3 X 5mm screws from the back of the diffuser wall , I use the same holes as when the diffuser wall is mounted on a jig for turning the shaft tunnel mount face



Its "heavy duty" , weighs in at ~4.5 kgs- 10 lbs , no flex in this tool .



With the starter motor mount I used on the 10/98 engine slid "firmly" over the jig



The feet of the starter mount were sitting reasonably on the bellmouth lip , 2 feet firmly down with the third having a 0.010"- 0.25mm clearance , not too bad considering the number of components involved



I'll try the alignment tool in the other two positions just to make sure theres no "compounding" going on that affects the alignment , but so far its looking acceptable as the starter motor has some "rattly"clearance in the mount so it can easily slide back and forth into engagement , whereas I made the jig a firm sliding fit.

Cheers
John

[pitciblackscotland]

Good one John, good to see you using some HEAVY DUTY steel material for your jigs Thanks for the photos

Cheers,
Mark.

[racket]

Hi Mark

LOL............I was thinking of you as I welded those heavy sections together , heh heh , I thought , just like Mark does it :-)

Cheers
John