10/98 engine

[ernie wrenn]

That is a nice burn! I like the patterns.

Fast rebuild.. Put it together... Video required!!

Ernie

[racket]

Hi Mark, Ernie

Things are looking a little brighter ........ a real nice change to finally pull an engine apart that doesn't have nasty surprises inside:-)

Not quite sure why the colour pattern is the way it is , possibly from the start/preheat gas which only goes to a few of the evaporators , but nothing to worry about with those colours , still got a nice shiny surface on the metal so no overheating .

Hopefully have her back together in the next week , want to explore a couple of mods first .

Mark , you should be seeing her in the flesh sometime mid November .

Cheers
John

[racket]

Hi Guys

Bit more of an update on engine development .................

...............conducted an extended high power test run yesterday to bring the entire engine up to full temperature .

Ran her at 42,000 rpm - 64% until the lube tank temperature reached just under 50 deg C , this took several minutes , compressor was putting out a PR of ~1.68:1 from a tip speed of ~1,000 ft/sec with TOTs of ~550 deg C

Once lube temps were satisfactory, the engine was accelerated to 66,000 rpm -100% - 1600 ft/sec tip speed and left there for a few minutes to get all internal temperatures to stabalise , comp was putting out a 3.42:1 PR with a T2 of 180 deg C ( 15 deg C ambiant) so a temp rise of 165 deg C for a comp efficiency of ~74% and with ~6 psit - 1.45 PR ( I'm at 2,800 ft altitude with an ambiant pressure of only 13.2 psi ) in the jetpipe .

A couple of short burst were made to 70,000 rpm -106% - 1,700 ft/sec tip speed (last line on the comp map ) with the comp putting out a 3.88 :1 PR and 8.5 psit in the jetpipe producing a PR across the jetnozzle of 1.64:1 and gas velocities of ~1650 ft/sec at ~700 deg C for a theoretical thrust of ~115 lbs ( ~128 lbs if at sea level with "heavier" air ) from its ~2.25 lbs/sec mass flow (2.5 lbs/sec
if at sea level) .

With 70,000 rpm on the tach the thrust was sufficient to start lifting the rear of the test stand despite it being tethered to the fence posts , to verify the theoretical thrust figures a static pull test was conducted after the engine cooled down , this entailed fitted a "harness" around the engine and using a 200lbs capacity spring balance pulling on the harness at the shaft/jet nozzle axial position, it required ~100 -110 lbs to get the stand to start lifting , well within the "ballpark" of the theoretical thrust .

There was a large increase in thrust between 66,000 and 70,000 rpm from the extra 2.5 psi of total pressure in the jetpipe , the jetnozzle is still slightly oversized as I designed for a TIT of ~900 deg C and am currently running closer to 800 deg C .

Lube temperatures at the end of the test were at ~90 deg C with lube pressure dropping to ~45 psi from the ~60psi at start of test using ~8 litres of 5W-40 synthetic oil .

Today I pulled the engine from the test stand and removed the jetnozzle/exducer shroud to check the turbine wheel which looked just fine , so progressed to removing the engines outer can to make sure the flametube was still in one piece, this was confirmed , so the engine was reassembled .

She's finally operating to a high enough standard for the bike :-)

Cheers
John

[pitciblackscotland]

Hi John,

that's good news on the 10/98. Now you can move on to your other projects, it's been a bit slow work on the T 30 engine at the moment works getting in the way and still haven't got to see Andrew yet.

Cheers,
Mark

[ernie wrenn]

Way to go...!

I was looking at the first temps and it did not hit me that the rpms's were low... I was figuring "damn how so much info with those low temps, must be so crazy efficiant machine".

I use a "strain gauge" on some test runs with the vehicles, tie they down, rev up, read gauge. It reads and locks on peak up to 10,000 lbs, have a second one that reads 100,00 lbs if someone needs to use it:).

Maybe Connie Kallettia flying service on his top fuel dragster.

Where are the videos?? Must have pics.... Cookies good!!

Ernie

[racket]

Hi Mark

Pics of the bellmouthing and D'ing tool.

First off , cut all 18 evaporator tubing sections accurately to length , within plus or minus 0.5mm so that subsequent operations require less fiddling around , deburr and cleanup ends, I use my plumbers pipe cutter for cutting the tube even though its made for copper pipe it works on the much harder evap tubing .

With the jig mounted in the vice slide evap tube over long "stake" on jig , this stake has a threaded end for length adjustment so that bellmouths are consistent.

If the adjustment is just right, when the short "punch" is inserted in the open end of evap tube and given a hit with the hammer , the ends of the "stake" and punch meet when the amount of bellmouthing is whats required .




Bellmouth all 18 evaps .

The jig is then repositioned in the vice and D'ing started .

Slide bellmouthed tube fully into neat fitting hole in jig (12 mm thick axially) with the recess in the top to a depth that exposes ~25% of the tube's diameter ( a tad under 2.5mm radially )



Using a short length of 25 X 5mm stainless flat with a squared off bottom edge as a punch , I position this punch in the 1/4" wide milled recess slot and give it a hit with the hammer , the evap tube is then extracted with a gentle blow to the outlet end of the tube with a soft hammer ( lump of wood), rotated 180 degrees and re inserted in the jig with a push fit as far as it can go , and the process repeated until the evap is D'ed along its length



Cheers
John

[racket]

A few more pics of jig







The "Jackson D Tube " does produce a better mix of air and fuel vapour exiting the evaporator, the extra turbulance compared to a straight through tube undoubtedly helps, most of the commercially produced RC micro turbines only use straight through types, and we probably could as well , but every bit of extra help with combustion won't go astray :-)

Hope the pics help

Cheers
John

[pitciblackscotland]

Hi John,
Ah yes now i remember, Thanks for the pics i have some steel blocks that i can machine up. I made up a jig for bellmouthing the vap tubes some pics here.

Cheers,
Mark..

[ernie wrenn]

WHY NOT USE A FLARING TOOL?

[racket]

Hi Ernie

It would be possible to use a flaring tool but a lot more work , also trying to grab that slippery thin walled high nickel content tube firmly enough to flare it is a bit difficult without causing distortions and/or minor damage to the tubing which we don't want.

With the jig its just a simply........... slide on tube , insert flare tool and hit with hammer , remove both and repeat the process with the next evaporator , with 18 to do , its a boring job that I like to complete as quickly as possible :-)

Cheers
John

[ripp]

Hi guys,

the latest version of sticks that I know
which function fantasisch they are with counterflow injection

www.rc-network.de/forum/showthread.php/47424-unerkl%C3%A4rliche-Hotspots.../page4



www.frankturbine.com/category/triebwerke/






ut160.de.tl/Galerie/pic-1000609.htm

Cheers
Ralph

[eira]

Aug 12, 2010 0:24:24 GMT -5 racket said:

A few more pics of assembly progress

Hi John,
what did you make the fuel injector (like a wire inside the vaporiser tube) from?
thanks

[racket]

Hi Eira

the injectors are made from a short section of 0.65 mm OD syringe needle silver soldered ( high content silver , low melting point) into the fuel manifold

Cheers
John

[eira]

How did you solder them so that you did not plug the injectors during soldering?

thanks,
Eira

[racket]

Hi Eira

The "prepared" syringe needle is fitted into the fuel manifold so that its "sharp" end is in contact with the ID of the tubing on the opposite side to the hole in the manifold , the "sharp" end has had its angled edge trimmed back to ~half its length and the angle is on the downstream side of the fuel flow.

Before fitting the syringe needle into the manifold its prepared by having the point ground back a bit and an~45 degree angle bend put into the syringe at ~15mm from the sharp end , the bend is required so that the fuel is ejected onto the inner wall of the evaporator and not straight down the evaporator bore where it won't be evaporated...............I leave the plastic bit on the syringe needle until after its soldered in place as it facilitates positioning , the plastic and some of the stainless tube is cut off using a Dremel and cut off disc after soldering , this leaves the required length of stainless after the bend to deliver the fuel onto the evap wall .

Soldering the tube , .........at least 50% silver content in the silver solder , and use as small a diameter rod as possible , 1/16" - 1.5mm diameter is as small as I could source.

Once the injector is positioned withing the manifold , some silver solder flux ( wet , white stuff, like tooth paste) is applied around the injector , its important to have a good sized "blob" ( at least a head of a match sized) as it protects and "cools" the very thin walled tubing once heat from an LPG gas torch is applied .

I first heat the end of the silver solder until a molten blob is hanging there , then the molten blob is positioned against the syringe/manifold and the torch is applied to the manifold with only a small amount of heat to the syringe.

If all goes well the molten blob of silver solder will run into the joint and produce a nice fillet once the flux is up to temperature , go slowly and don't apply too much heat as you'll "burn" the syringe needle , once it goes black , the solder won't stick , thats why its important to have a good sized blob of flux , it stops the important joint area from going black , the rest of the syringe will , thats OK ................the silver solder should only be on the "outside" of the manifold , it shouldn't run inside and block the syringe or the manifold , if it does go inside then you've used too large a hole in the manifold for the syringe to fit through and/or you've used too much heat .

For a 0.65mm OD syringe needle a 0.7mm hole is all you need , I find that its easier to produce a small hole if I first "centre pop" the positions in the manifold using a small shallow tapered centre punch in my drill press chuck , lay the manifold on the drill press table and bring the punch down and give it a "repeatable" pressure on the handle , just enough to break through on the ID , this then leaves very little metal to drill out with the fine drill in the Dremel , the centre punching also leaves a nice "rounded" entry to the hole without any "lip" like you'd get by drilling alone , the lack of lip aids in the soldering process .

It will probably pay you to do a few trial runs on a bit of scrap manifold material ( auto steel brake line , bundy tubing) and a few syringe needles to get the feel of things before attempting the actual manifold .

Syringe needles of the size I use can be sourced from Veterinarian Clinics , quite inexpensive .

I don't seal the end of my manifold until after everything is finished so that I can blow out any bits of material resulting from the trimming of the syringe needles after soldering them into the manifold .

If for any reason an injector is blocked , just heat and remove , insert a replacement and solder in place ..................check afterwards with some gas to make sure all injectors are flowing equally by the flame heights they produce .

Cheers
John