My rayburn Turk Burner - running on waste veg oil

[Ivan]

Still some work to do, but here's a couple of photos of the first firing

[Billy]

Hmmmm,

second one looks like a photo from the Hadron collider!

Is that a neutrino or whatever?

Are the neighbours going to complain about the chip shop?   

Billy

 

[martin]

2nd photo, health and safety job, taken from 28 miles away!

[Ivan]

The second photo is to demonstrate the lack of fiery warmth. Most turk burners are so bright you need cutting goggles. This one, you can just about see the orange glow. I've done a quick estimation - 1 drop every 8seconds, if I assume each drop is 0.1ml (probably about right), then that's 85cc per hour, or around 450watts.

I reckon it should be at least 22 000BTU (6.3kW), so I need to have 14x higher flow rate...ie 2drips per second. I'm going to need to pressurise the fuel tank to achieve this. I guess the oil is too viscous for the diameter of pipe that I've used. Gonna need to build a pressurised fuel tank.

[Baz]

Have you considered a preheater coil around the outside of the chamber to thin the oil at the nozzle?

[Ivan]

Funny enough, I've accidentally fitted a preheater. I purchased a proper fuel oil solenoid. The idea was that I can fit various safety features which will automatically cut off the oil if necessary. The solenoid (mains) gets hot to the touch, and I noticed that the copper pipe feeding it is also too hot to touch. It must be using 20W.

My nozzle is nothing fancy - just the end of the pipe. I think the resistance is due to the fact that the 1.5m of copper pipe used between fuel tank and rayburn is 6mm thick-walled copper pipe. Probably I should have used 10mm - but the oil solenoid has tiny 1/4" connections, and it was the easiest to match up.

[Iain]

Hi Ivan
Could you use something like this? instead of a pressurised tank
http://cgi.ebay.co.uk/NEW-WEBASTO%2fEBERSPACHER-FUEL-PUMP-12-VOLT_W0QQitemZ230538345783QQcmdZViewItem?rvr_id=157138264361&rvr_id=157138264361&cguid=68d77ead1270a0aad396c596ff38554a

Iain

[guydewdney]

or any diesel car fuel pump? I have used aquarium air bubbler adjusters as oil flow controls before.

[Baz]

Gravity is free. I think a car fuel pump would struggle woth thick stuff.
The solenoid will probably hold in with a lower voltage once activated so you maybe able to have a secondry circuit with a bulb in series and a switch that bypasses the bulb to turn on initially.
How do you light this thing as I assume it has to be hot to vapourise the oil inside?

[Ivan]

Well it looks like the problem is the flow rate, and this is down to the fact that I've used 6mm pipe. I would probably have chosen to use 10mm, but 6mm was convenient, because of the tiny connections on the oil solenoid (I thought this was a good safety feature, but given the fact that it seems to be using a lot of power, and the fact that it's very restrictive, I'm very tempted to take it out).

So how do I improve the flow rate? I can raise the fuel reservoir higher, but already it is almost 2m higher than the burner, so I don't think this is practical. I could replumb with 8mm or 10mm pipe and remove the solenoid. Or the easiest thing to do is to pressurise the fuel tank. If I use one of the Navitron filling kits (basically a hand-pumped water-sprayer), I can test the theory. So that's what I did this afternoon. As you can see from the pictures, it had the desired effect. Rather than having a maximum flow rate of one drip every 8seconds, I can now have anything up to and including a continuous stream of oil - which I can control with my needle valve.

Lighting it takes a few minutes. I push some tissue paper down inside the burner and then light the uppermost piece. When it starts to burn I start the oil dripping, and go and turn on the air (currently running from an air compressor with the regulator set to about 20psi and running through about 45ft of airline). Takes about 10-15minutes to get going properly, and it smokes a little (tiny bit of grey smoke - probably due to burning the paper more than anythign), but once it's up and running, what's coming out of the flue is simply heat haze - no smoke whatsoever, so it must be burning well. I've filmed it, so I'll stick it on youtube later and post a link.

[Ivan]

Here's the flue emission when the fire is burning strongly. The rayburn heated up reasonably quickly, and I measured 150C on the hotplate. The flue inside the room just before it converts to twin-wall flue to go through the ceiling was no more than 50C - so most of the heat is being extracted, although admittedly the rayburn wasn't up to full temperature.

I've also added some details of the air feed pipe. The idea is to make the rayburn room-sealed by the time I've finished. The air feed is basically scaffold tube with a scaffold elbow. Nice and simply!

[Ivan]

How's that for clean-burning. Nothing but heat-haze from the chimney flue:

<a href="http://www.youtube.com/v/ggcpDBB1beM" target="_blank">http://www.youtube.com/v/ggcpDBB1beM</a>

[knighty]

what's your plan for level control ?

or is there some trick to it, and the more oil there is, the faster it burns, so it's self levelling ?

[Ivan]

It's a work in progress!

I've been wondering if there's an easy solution to this - and can't yet think of one.

At the moment, it works like this: You light it manually (with paper) and allow the oil to drip slowly onto the burning paperl Once the oil/paper is burning well, the air is turned on and oil can be turned up until it's around 2drips/second. As the combustion pot is cold, the oil doesn't vaporise, so it burns quite slowly at first (and probably inefficiently). It will start to heat up and the fire will become fiercer. If it's not enough, then you can open the valve to provide more oil. This cools the evaporation surface somewhat, so the rate of evaporation and therefore the intensity of flame decreases for a minute or two. Of course, it builds up a pool of oil, so when it heats up, the extra oil provides extra evaporation, and so burning is much more intense, and then eventually settles down.

It's very easy for the system to oscillate, if you are trying to control the burn with the valve - as you overcompensate.

My view is that if you know the drip rate you need, you simply set it to this and it will settle at the correct burn rate... but I need to practice a bit more before I'm confident. It seems that faster drip rate = more intense flame, so I think to a certain extent, it is self-regulating

A better and safer option would be to have an overflow. Although I don't know how well this would stand up - you don't want burning oil overflowing into a reservoir, and you'd probably end up with the overflow tube jammed-up with sticky partly-burnt oil. It would also make it very difficult to remove the burn pot for cleaning - something I feel is quite important to the design.

I'm wondering whether I could use a flame sensor (eg ORP12 light sensor at the end of a tube to take it away from the intense heat of the fire), and work out a range of acceptable light outputs. If the light falls below a certain level, then fire is deemed to have self-extinguished, or if it rises above a certain brightness, it is deemed to be out of control, and in both cases it would close the oil solenoid. Alternatively, I think it might be possible to use feedback in terms of hotplate temperature as it is directly in the firing line for the exhaust gases: If the hotplate falls outside the range 100C - 150C, then shut off solenoid either until manually reset or, if the temperature is too high, until the temperature falls back within range.

[Billy]

I have non-electric (capillary?) overheat and flame out sensors fitted to the 8mm copper.  They work very well in stopping anything too catastrophic, for that I have a fusible (50C) link on a spring close valve .  I have noticed that the optical sensors similar to the ones fitted to oil boilers are rather sensitive to smoke on the glass and have a habit of shutting off when all is well.

Have been trying to work out the consumption but failed miserably.  Brill bodgeneering.   

Billy