The humble beginnings of something BIG; JU-03!

[Johansson]

You are flattering me John.

I think it will be difficult to form a tube to the exact shape needed, making a flat pattern and shaping it to a hollow blade feels like a more controllable method.

Welding is a minor problem, fitting the blades to the hub is a much more exciting project. But I am getting ahead of myself, first I will see how well these blades will work.

/Anders

[racket]

Hi Anders

You deserve it :-)

Cheers
John

[Johansson]

Dangit, I better run to the workshop and earn the praise then!



After a day of work around the yard to clean up before the snow falls I decided to start making the fuel manifold.



A 10mm stainless pipe will feed 8 Danfoss spray nozzle holders.



I made all 8 of them and a T-piece where the feed line will connect to the fuel ring, then I called it a night.



The nozzle holders will be silver soldered to the pipe after bending it so the holders line up with the holes in the combustor lid. But that is tomorrows job.

Cheers!
/Anders

[Johansson]

A sunny day with a few centimeters of snow, glad that I stored away the boat yesterday.



The pipe bender is not rated for thick walled stainless, but it did its job without breaking.



A set of brackets for the fuel manifold were made, I will use lock wire to fasten the manifold to it since I will have to be able to remove it easily for nozzle changes.



The combustor lid warped a little during welding but since there is an airgap around the spray nozzles a couple of mm in or out won´t matter. I silver soldered the nozzle holders once they were in place.



Good enough, once I have checked that the manifold is leak free I might cerakoat it.



A jolly although somewhat hasty fellow, or as the kids say; a Lazy Azz Niggah, didn´t take the compressor to back plate clearance into account when he made the comp housing. I corrected this today by cutting, annealing, bending and welding.



Now the air will meet its fiery doom with no restricting edges along the way.



I reassembled the engine and checked the manifold clearance , nemas problemas.



Finally a picture of the engine on its stand, I´ll probably run straight into it next time I visit the garage and bump a knee...



Cheers!
/Anders

[Johansson]

Guten abend meine freunden.

A parcel was waiting for me when I got home from work today, it was the 4-stroke starter and the centrifugal clutch pulley.



It fits perfectly in the test rig beneath the turbine, I will make the starter mount adjustable for tensioning the belts.



If 9hp won´t get this thing turning nothing will...

Cheers!
/Anders

[richardm]

You will be surprised to see how much it takes 
A 14 inches centrifugal fan i built years ago for a leaf vacuum  that is driven by my lawn tractor engine at 14 hp . Got to go easy on th clutch  not to stall the engine even at full throttle. Once running I can see the engine governor is full open . Clutch gone get hot.

[Johansson]

Good evening guys!

I got a call that a big ass box was waiting for me at the postal office, it was apparently too heavy for delivery.

-"Hmm, that is strange. I just ordered a small 230V motor and some hydraulic fittings"



A Bosch 044 pump is used as reference, I must have skipped school the day the teacher told us how large a 2.2kW single phase motor is...

But I specified that I needed a 230v motor that could make the pump produce 8L/min @ 200 bar fuel pressure, so I got exactly what I asked for.



I also recieved the fuel arrangement, it is a needle valve on the fuel return line along with an adjustable max pressure valve.

This should work just fine for controlling the spray nozzle pressure, I just need some hydraulic hoses made and a ball valve on the pressure line for quick shutdowns.

Hopefully I will get the sheet metal cutouts later this week, I want to finish the engine before I start hooking up the auxilliary equipment.

Cheers!
/Anders

[racket]

Hi Anders

Thats one very nice fuel pump, heavy duty :-)

Yep , you'll need to have it setup so that you don't blow hoses in the heat of the moment , easy to turn off the wrong valve ............. I found the cleanup is time consuming :-( ....... the pressure relief valve setting can also sets you max fuel flow into the engine to prevent over fuelling, good safety feature.

A nice big truck sized fuel filter on the inlet and you'll be ready to start spraying

Heh heh , first time the fuel pump weighs more than the engine ;-)

Cheers
John

[Johansson]

I think I have invested roughly 2500 USD in the auxilliary stuff (starter, ignition, fuel pump) and that is money damn well spent if it means that I can focus entirely on getting the engine running.

Instead of like in the bike, spending years fault searching only to find that a voltage drop caused my almost too weak oil pump to lose pressure.

The pressure relief is a nice safety, yes. Hopefully I can motor the turbine up to idle revs and slowly increase fuel pressure until it starts to pull away from the starter.

I have no idea if the centrifugal clutch will disengage at that point, I might have to redesign it with a one way clutch on the rotor shaft pulley later.

[racket]

Thats some serious money , but well worth it to have reliability , those " silly" little problems can be frustrating, we can spend more time on them than building the engine .

An overun disengagement would be a good thing on the starter as I've often found the engine acceleration is held back by it having to spin the starter , as soon as its disengaged the engine spools up faster

[Johansson]

I have been pondering how to design the compressor cover.

A snug fitting lid over the compressor is not going to happen because of the slight wobble in the outer wall.

The only practical solution is to make a flat cover with a generous (2-ish cm) air gap to the compressor, and make a rim that fits snugly into the inducer.

This rim will act as the seal and my assumption is that the centrifugal forces combined with the very low P2 will keep the air leaking out at a minimum.

Will I see performance losses in the compressor because of this air gap? The air exiting the exducer should still go straight into the diffusor since the air filling the air gap is more or less trapped with nowhere to go.

Keep in mind that I am not aiming for perfect with this engine, or even anywhere near. Manufacturing parts large as these by hand forces me to cut all the corners I can without sacrificing too much part efficiency.

/Anders

[richardm]

"I have no idea if the centrifugal clutch will disengage at that point, I might have to redesign it with a one way clutch on the rotor shaft pulley later."
This is point I was about to write about
If that clutch is what I think, its friction pads are driven by the ICE engine against a drum. The only way to disengage it is to return the ICE engine to idle It cannot be overrun by the tubine.
So the turbine will not accelerate any faster than what the starter can bring it up to, because it would have to "overspeed" the ICE engine.

It will work only if the starter system can bring the turbine at or above self sustaining speed, at wich time the ICE would be throttled down to idle.

Thats just my opinion I could be wrong. A solution could be an intermediate shaft fitted with a one way bearing or some sprocket clutch ..

[Johansson]

Richard: Yup that is very likely to happen, one easy fix is to buy a longer belt and make a rolling belt tensioner that can be released by hand.

With a slacked belt the clutch pulley should disengage and then I can reapply belt tension so the belt isn´t wearing a waist on the spinning turbine pulley.

Later on I will come up with a more sexy way of starting it, but for now this will do.

[jetric]

All you will need is an effective seal at the inducer, it doesn't matter about the cover clearance to the rotor as this is one of the advantages of a shrouded compressor, this is how the schreckling FD3 compressors are.
With regards to your centrifugal clutch you would have to use a one way bearing as well to disengage the drive because as the turbine engine speeds up with the centrifugal clutch engaged the centrifugal forces holding the clutch shoes onto the clutch bell increase, in order to disengage the clutch you need to be able to slow down the starter engine revs but you won't be able too because the turbine engine is now driving the starter engine and increasing it's revs and increasing the centrifugal force holding the clutch shoes onto the clutch drum, this is why you need the one way bearing so that you can reduce the revs of the starter engine regardless of what rpm the turbine engine is doing so that you can reduce the centrifugal force on the clutch shoes untill the return spring can pull them back off the clutch drum and disengage the clutch.

Nov 12, 2024 14:08:57 GMT -5 Johansson said:

I have been pondering how to design the compressor cover.

A snug fitting lid over the compressor is not going to happen because of the slight wobble in the outer wall.

The only practical solution is to make a flat cover with a generous (2-ish cm) air gap to the compressor, and make a rim that fits snugly into the inducer.

This rim will act as the seal and my assumption is that the centrifugal forces combined with the very low P2 will keep the air leaking out at a minimum.

Will I see performance losses in the compressor because of this air gap? The air exiting the exducer should still go straight into the diffusor since the air filling the air gap is more or less trapped with nowhere to go.

Keep in mind that I am not aiming for perfect with this engine, or even anywhere near. Manufacturing parts large as these by hand forces me to cut all the corners I can without sacrificing too much part efficiency.

/Anders

[Johansson]

Exactly what I wanted to hear Jetric!

I will roll a 40x5mm strip of aluminum and weld it around the diffusor entry edge. Then make a matching compressor lid that fits inside that ring and bolt them together with a ring of radially fitted screws. This ring will also act as a good place to bolt down a future air mesh screen.

The compressor cover will get some sort of bellmouth around the sealing rim.



/Anders