Turboprop PJ experiment update

[larry cottrill]

Congratulations, sir!

Now come on, let's see it!

L Cottrill

[racketmotorman]

Hi Guys
I'll install a better fuel control valve today and hopefully tomorrow some video for your viewing pleasure . :shock: :D
Is there somewhere on the site for videos to be put or will I need to find a home for it off site .
Just a quick question concerning valve flow areas , there seems to be a lot of different interpretations of out there of what the "area" needs to be in relation to the "exhaust pipe" .
My question is , what is to be expected if the flow area is on the small side?
I only installed 2 reed block sets which may be enough according to some info, but could be a bit under valved according to others , I have made provision for another block or even two if need be , I just didn't want it "over valved" to start with , much easy to add that remove :D
Cheers
John

[Jonny69]

Wehey nice one!!!

Can't wait for the videos *cough cough*

Jon

Edit: any chance of a couple of piccies of your valve blocks and how they mount up?

[racketmotorman]

Hi Jon
I sent a CD of some test runs off to Nick Haddock (where I have my bike and kart videos) who'll kindly put some up on his website ,
http://www.nickhaddock.co.uk/jetgallery.htm
possibly in about 10-14 days time , it takes the post that long to get from Oz to the UK , so you'll need to wait a little while longer to see her in operation . :D

The 2 Yamaha reed blocks are set in the ends of 2 tapered and curved manifolds ( to limit radiant heat damage ) about 7 inches long which "sprout" from the front plate and curve downwards and outwards on each side so that on shutdown the hot air inside the engine can't get to them , they're sorta at the "bottom of a well" where the cooler air is .
Theres 2 rectangular ports , 2"X1" each , spaced radially 120 degrees apart at the 4 o'clock and 8 o'clock positions cut into the front plate that the reedblock manifolds are fitted into .

I'll try and get some still pics of just the valve end up here on site in the next coupla days

The engine apears quite throttleable, something I found out by accident when the liquid propane ran out and she started to run on the gas left in the bottle , the prop started to slow down to about 50 rpm and the PJ noise reduced along with the prop rpm .

After refilling the tank , I experienced a fair bit of "overfueling" and "flameouts" until I rethought my fuel settings , but once that had been sorted I had one decent run (unfortunately not caught on film as both cameras had full cards by then ) until the turbine tips contacted the shround/burst shield and brought things to a halt , my expansion calculations were just a little too optimistic ( I left 1.5 mm diametric clearance) , so I'll need to grind another 0.5mm off the turbine blade tips just to be on the safe side , the stainless blades are expanding a lot quicker than the mild steel shroud which appears to not be getting all that hot , possibly a "cold air blanket" on the inside of the ducting of the IGVs and shroud , sorta like a "normal" PJ augmentor .

I've got the freepower and prop removed so I can start development work on the bare PJ to optimise its performance and verify its "pure" thrust rating before reinstalling the freepower and prop.
It'll be nice to just fireup the PJ without worrying about the prop whirling around on one side of me and a homemade turbine on the other .
The prop will have its pitch reset back from 45 degrees to 30 degrees to allow the freepower turbine to "rev out" , she's just a little "overproped" at the moment , at least that stopped any chance of the turbine "running away".
Cheers
John

[El-Kablooey]

You can post videos here! just ue the "add attachment" button! Some formats won't be accepted, so you may have to zip your vid before upload.

[racketmotorman]

here's a few pics

[Mike Everman]

Man, that is sweet. I always wondered if valves would work at the end of tubes. Just makes sense to keep them away from the heat. Very cool, and nice construction.

[Bruno Ogorelec]

It does reduce performance, though. There's a Japanese company that does similar stuff for central heating purposes.

The drawing shows the in-line arrangement but the photo shows the valve 'funnel' mounted at right angles to the engine axis. Both arrangements work

[Jonny69]

Cool I've never actually seen a reed block before, I didn't realise they are a complete unit like that. Google image search is king!

[larry cottrill]

John -

Incredibly beautiful work. Congratulations!

Stainless expands with temperature a lot more than one might think. It is mostly due to very poor conductivity. This is one of the difficulties in welding - the metal expands locally, which can throw carefully positioned edges out of alignment as you try to weld them together.

Wonderful work on that engine!

L Cottrill

[racketmotorman]

Hi Guys
Thanks for the kind words :D

Bruno, I'll see how much of a loss there is when I do the "pure thrust" testing of the bare PJ , and let you know the results , I'm not too worried about it not turning out its full 50 lbs of thrust potential , its more the shaft power extraction as a proportion of the actual engines thrust output that I'm interested in . If it only turns out 30-40 lbs of thrust but with reasonable throttlability and fuel burn rates it'll do for testing the turbine , I'll simply recalibrate my expected shp output accordingly .

Jon
Those Yamaha reed blocks are ready made units , they come with "rubber" coated surfacing where the valves seat for long reed life and theres a range of various thickness reeds as well , I'm currently using 0.007" on one set and 0.010" on the other set for comparison .
I've also got a reed block with "plastic" reeds that I might try at a latter date , the newer reed blocks all use composite reed material :D
The best part is that reeds are readily available "off the shelf" parts , and the complete secondhand reedblock units I'm using only cost between $AU25-40 each , they come from a mixture of different sized engines , but all have the same basic dimensions , those good old Yamaha engineers decided to save a bit of work and use a common part for a large number of different models , which makes finding secondhand parts very easy .

Larry

I think I got caught out by the lower temperature rise of the outer shroud/containment bust shield , I did the calculations using the correct coefficients of expansion for the various metals , exactly the same as when I made the bikes freepower turbines shroud/contaiment ring , it worked out OK on the bike , but it didn't have the luxury of "cold" ambient air pulsing thru it , so it undoubtedly expanded a little more and maintained a running clearance over the labyranth seal on the bikes freepower .
Ah .. the joys of R&D , it won't take long to grind a bit more off the turbine tips in the lathe , and it only takes a few minutes to refit the turbine , its designed for easy assembly and disassembly .

LOL....I approached the engine design as just another reed valved two stoke engine with a tuned Kadenacy exhaust pipe, minus the alloy bit that goes up and down in its cylinder , prefering to have a purely rotary power extraction

I'll keep you all updated on developments as they progress

Cheers for now
John

[Bruno Ogorelec]

John, do keep us posted. It's a fascinating project and you have certainly thrown in some very original details. This is going to be quite entertaining -- and possibly educational, too.

[racketmotorman]

Hi Bruno
It should be good for a bit of entertainment , I'm not all that worried if the whole experiment comes to a dead end , afterall , its life's journies that are fascinating, not its destination :D
I purchased a secondhand Bosch EFI pump yesterday and will start on the petrol fuel system this week before taking her out for some thrust testing .
There'll also be a "mean exhaust temperature ??" gauge installed to get some idea of the temperatures going into the turbine stage from the PJ , I'll have to wait until I get the freepower reinstalled before measuring the actual mean temps that it experiences , theres undoubtedly going to be some ambient air going into/thru the turbine between pulses , so by measuring the exhaustpipe outlet/inlet temps vs turbine outlet temps (TOT's) I'll get an idea of whats possibly happening .
Cheers
John

[Fricke]

John -

I just downloaded the vid...

WOW! I must agree with Chris K on the DIY-list: You are my hero!

Awesome work!

Keep the flow of Your good work flowing!

And the reed-valve gizmos... I must try that on my PJ soon too... ;)

Cheers
Fredrik

[Mike Everman]

OH that's classic!