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19th Nov 2006
Finally found a suitable container for the oil reservoir, an old CO2 cylinder from a public house that was closing ( Free ), the cylinder will hold 10 litres of oil, giving a maximium burn time of about 6 hours without filling. All the pipework will be metal, with the cylinder fastened to the wall so it can't fall over but sitting on a small stone plinth, it should present minimal fire hazard. Because the cylinder neck is quite narrow, finding the level of oil will be problematic so I have come up with the idea of a pressure gauge and a small pic micro to monitor the oil level and give early warning to prevent running out of oil. May even incorporate the pump controls and a photo sensor to shut down the furnace if the oil runs out or flame failure, may be able to automate the lighting sequence. ( Have found a supplier of oil burner ignighter 'EBI' transformers and ceramic insulated electrodes - will see if Santa can bring me some ).
27th Nov 2006
Now thinking about autoating the whole burner system, with automatic single button start, have managed to get an EBI transformer off eBay, with a single pic and some opto isolators / relays I should be able to automate the burner with auto start and safety cut out.
- Single button start.
- Auto shutdown if no oil.
- Auto shutdown if flame extinguished.
- Oil level / burn time left.
For more information and constructional details follow the links below:
Update 26th Oct 2006
Hooked
up the burner to the furnace for a test-run. Still a pain to light,
may need to investigate a spark ignighter as used in oil fired central
heating units. I had to light the burner and then mate it up to the
furnace, to start with there was quite a lot of carbon deposited into
the furnace coating the whole of the inside. By adjusting the pressure
of the oil supplied to the oil nozzle the pressure ( oil flow ) can be
backed off just enough to stop the carbon build up, the photo is near
the end of a 45 minute run. The
furnace burned clean of carbon on the inside, the crucible attained a
dull orange in colour, more than enough for aluminium but still not
enough for cast iron. ( Perhaps a higher air flow with more oil - but
will need a larger combustor ).
Update 22nd Oct 2006 
It Works!
I had to shorten the flame tube to just beyond where the blower enters the combustor, igniting the unit is difficult ( maybe a spark igniter? ), the air blast has to be reduced to get the oil to light but once burning the full air blast can be applied.
There is no appreciable smoke but carbon is deposited by the flame, I'm assuming that the carbon will burn once the furnace temp goes over 1000oC.
Next there needs to be a stand for the burner to bring it to the correct height for the furnace, an oil tank to hold the fuel oil and a short coupling tube to link the burner exhaust to the furnace.
A piece of steel pipe placed just in the end of the burner blistered quite quickly, oil consumption is about 0.215L in 6-8 minutes, sorry I wasn't watching the clock.
This means that on the low setting the burner is running somewhere between 14.5kW and 21kW output. At the current cost of £0.58 / litre for fuel oil, running cost should be about £1.00 per hour, this should work out about half the cost of running the furnace on propane. ( And yes the burner is much quiter than the propane burner ).
Oil Burner - Preliminary
I have finally decided to have a go at building an oil burner for my furnace, it will be designed to burn domestic fuel oil. The primary aim of the project is to raise the top furnace temperature from 11500C to that required for cast iron, secondary goals are to lower the cost of running the furnace and make its operation a lot quiter, the propane burner system sounds very much like an airliner ( up close ).
Currently I have the following components:
Danfos oil pump BFP 52E L5 - Dual pressure range 7-15Bar and 10-25Bar
80W electric motor with flange for oil pump
a range of 4 atomising oil nozzels 0.4 - 2.5 USGal/Hr
3 x 97 cubic feet per minute blowers
Still Needed:
Control board - will design & build myself.
Source of ignition
Flame sensor?
Time to put it all together.
Preliminary design concept.
The oil combustor is based upon the principle of a jet engine combustor, finely atomised oil will be injected at the left hand end of a perforated tube where it will be burnt, air will enter the combustion zone via a wind-belt around the perforated tube.
Here's a concept picture of the combustor flame tube, I'm aiming for something not unlike the combustors used in jet engines.
14Th Oct2006 Flametube and Windbelt completed
Assembled Combustor
Oil Nozel
Oil Pump
Pump Motor
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PROJECTS 
