DIY syphon nozzle

[Julian]

That's pretty much what I said.

I think it all depends on the flow at which the regulator is designed to work and the capacity of the compressor.

[Tony]

My compressor dates back to 1977, it's a year younger than me   It's a vertical 35l cylinder with 370W (1/2HP) Brook-Compton motor on top.  The hotter it is, the better it seems to pump.

I vaguely remember reading that the rule of thumb for compressors was roughly 4 cfm per HP which would suggest 2 cfm from it.

I've measured its actual flow rate at between 50-70 lpm depending on whether it's cold or not. That's 1.8 - 2.5 cfm in old money.  Not a lot!

The regulator with it is knackered, I actually have two replacement regs here both 1/8" ported.  Thank you Julian but I will just buy a few 1/4 to 1/8 nipples for the ones I've got.  I don't think 1/8" ports will be much of a restriction on this compressor.

So yes I've been driving the nozzle directly from the compressor, which gets up to about 40 psi and sits there with the compressor running continuously.  This is way too much air pressure for the nozzle (it starts syphoning at just a few PSI), so I've been unplugging it to get the flow down as the air diminishes.  Not a great way to maintain a consistent syphon.

Raising the fuel above the nozzle also increases the flow, this makes it much richer and I have managed to light that at lower PSI before the compressor ran out of air.

It sounds like I need to get a reg on it feeding a constant pressure to a needle valve, get a decent flame going, and measure the rate of liquid usage.  Then move on to burning glyc rather than bio.

Knighty your compressor I suspect is somewhat more powerful than mine

[knighty]

my compressor is ok, it's a 4kw hydro vane... which isn't bad but can't keep up using something like a air sander etc...


but... I got drunk on ebay once night, so I've got a 1500litre tank for it... once that's full it takes forever to empty... it's a real pain when you need to empty it on purpose :-o

[Tony]

Ahha - sustained burn with regulator and flow valve!

http://youtu.be/tNkCL20w3R0



The traditional beans can



Needed the fuel raised quite high to get the flow right for correct fuelling, so nothing like as good as a proper nozzle.  Perhaps not too surprising.  This was on bio, it would be good to try glyc too.

[Tony]

The tube in the video sounding like a pulsejet makes me just want to "tune it".  It wasn't popular with the neighbours

[knighty]

I think pulsjet noise means it's not getting enough air ?

maybe you should shape the start of the tube like an educator, and get it to suck in extra fresh air ?

[Tony]

Maybe use a bigger tube?

I've got a little DC gear pump and a voltage regulator now, should be able to meter the fuel flow better.  Perhaps more fuel and more air and a bigger flame

Here's the pump, not bad for £1.69

http://www.ebay.co.uk/itm/251526596739

6mm OD nylon tubing seems to fit over the ports snugly, so I need a 6mm - 4mm reducer (£1.39 - this project is getting expensive).  In testing it runs quite happily with a lot of flow at just 3V so I'm hoping this means it'll run continuous duty (since it's rated for 12v).

[Tony]

To keep the info all in one place, here is it burning with jamesrl's amazing burner tube attached:

http://youtu.be/2S7T6ChiS3s
http://youtu.be/-j2Cmst88aM
http://youtu.be/xF-giW4eotc





Our weekend of experimentation at the BBB has taught us that a cheap gear pump slips the motor shaft when asked to push veg or engine oil hard (though probably would have been OK if it was heated first to thin it), and that getting the air flow and fuel flow mix right makes a major difference as can be seen in the pics above.

My linear voltage regulator and small 12V PSU wasn't up to running the pump for any period of time, we had to resort to car light bulbs wired in series/parallel to control the pump speed, driven from a 12V car battery.

It was also a pain to run back to the compressor to change the air pressure, a regulator local to the nozzle might be a better idea.

So I think another air regulator is in order, as is a better gear pump and appropriate drive circuit.

[Tony]

I'm going to experiment a bit more.

At the moment with the air nozzle and blunt syringe it has 1.1mm2 fuel delivery and 1.5mm2 air delivery.

So I am thinking of upping the air outlet size to 2.4mm from 2.1mm using a rivet nozzle:

http://www.ebay.co.uk/itm/191576261067 (£3.44)

...and putting a 2mm OD tube down the middle which gives 1.4mm2 air - so for the same air flow the pressure will need to be higher but the air flow will also be greater velocity.

This also means it's a bit easier to get the tubing in decent lengths:

http://www.ebay.co.uk/itm/Hobby-Design-Stainless-Steel-Tube-Diameter-2-0mm-Length-200mm-/271909498165 (5 off for £5.07 delivered)

No clue on ID though and there must be suppliers in the UK, not that I've found any!

[Tony]

Right!  And this is the making of a meatier viscous fuels pump

https://www.youtube.com/watch?v=dYQQ3hFtYWk

Can't imaging that'll struggle with engine oil or veg.

[Jamesrl]

Right!  And this is the making of a meatier viscous fuels pump

https://www.youtube.com/watch?v=dYQQ3hFtYWk

Can't imaging that'll struggle with engine oil or veg.

Geezus, are you trying to compete with the heat output of an oil fired Power station?

[julianf]

I think you might need more air flow with that pump?

I'm wondering if you couldn't use the compressor for the jet, and then a fan to pump in the volume for combustion? 

Rather like krill (etc) burners.

Me?  I'm just waiting for you design to stabalise, then I'll copy what you've done! : )

[Tony]

Right!  And this is the making of a meatier viscous fuels pump

https://www.youtube.com/watch?v=dYQQ3hFtYWk

Can't imaging that'll struggle with engine oil or veg.

Geezus, are you trying to compete with the heat output of an oil fired Power station?

It's way more flow than it needs to be, but if it is set up to run against a valve which lets the majority of flow return to the tank that will allow some pressure control?  The advantage of that is that this return flow could potentially be routed via a HE to warm the fuel tank from the output flame.

[Tony]

I'm wondering if you couldn't use the compressor for the jet, and then a fan to pump in the volume for combustion? 

An interesting thought, ideally the compressed air should only be used to break up the liquid for the jet and the rest of the air can be fairly low pressure but higher volume.

But, I do want it to be simple so others can re-create without too much build/scrounging.

If I can regulate the output of my gear pump to make it suitable for running the jet, then the same should be possible for say, a 12V power steering pump or gear pump driven from a wiper motor.

Also, I think I've found some decent lengths of capillary tube in stainless, but it's hard to tell from the listing what it is (from China - Aliexpress) so I've ordered some and crossed fingers.
 

[Tony]

Bit of a setback with the gear pump.  I'd figured out where all the ports and one way valves went, run it one way and it would suck through the hydraulic filter, the other blow bypassing the filter.  Could change direction if the one way valves were reversed.

Anyway, decided to run some water through it to see how it did, and it stalled almost immediately.  Couldn't get it to run backwards or forwards on the VFD.  Then the VFD cut out.  Can't get it to drive the motor at all.  I've checked the windings and they are OK, dismantled the pump so I can turn it by hand but the VFD is having none of it.  No current fault codes, just won't drive it.  I've reset it to factory defaults and reconfigured it but no joy.

It may (not 100% clear on this) have flashed fault code 08 at me at one point, which means "component failure".  But I can't see that now.