Darren, thanks for an interesting input.

Today I had a final go with the Origo ‘upgrade’. I had some (3/16”?) copper pipe laying around, so I bent it to fit into the central fire tube of the burner. Two rows of 1mm holes were drilled, see photo below, left. The idea was much the same as yours, to inject air into that central flame.

Boil tests showed about 4:30min to boil (dry kettle), about the same as without the booster, yesterday. Frankly, the aquarium pump was not strong enough to make much difference. On the photo below, right, one can see the flame with the booster off. As can be seen, the central flame is yellow while it turns blue when spreading out. Today was very calm, and this helps to get this nice flame  -  the Origo doesn’t like too much draft.

The kettle, made to fit electric stoves, actually appears to make good use of the alcohol burner. The handle does not get very hot. As for smell, I always cook with the main hatch open. The galleys of all my boats have been in this position.

I now have the option to keep on using the Origo, or to reinstall my (kerosene) Optimus stove from Johanna. For my simple use, I guess I will stick with the Origo. It is good enough and safer and simpler in use than any other stove I have had or used.

Until I find a stronger, but still cheap air pump, I’ll drop this project. What I have gained, apart from some experience, is a weird collection of funny-looking bent pipes and twisted copper and tin plates. Maybe I should frame them and hang them up one the wall. A temporary title could be

“Twisted products of a twisted mind”

Any better suggestions?

Cheers,
Arne

.. yes, the kettle is also important..

David,

I agree with you with respect to soot and CO. As can be seen below, my kettle has been blackened quite much. However, it doesn’t seem to build up much soot on it. I wonder if it has to do with my use of it. After other cooking, I generally fill the kettle up for heating dish-washing water. This I do with the burner on the lowest setting with all-blue flame. Maybe this helps to burn the kettle clean.

I can think of two more tests of the booster before I drop it: One is to use the shown ring of copper, and then raise the kettle about 10mm to improve airflow. The other is to use a thin copper pipe and bend it to a J-shape and fit it down the primary flame tube of the stove. With a number of 1mm holes in that pipe, hopefully that will add enough oxygen. That solution would not hinder normal airflow under the kettle.

Quite another thing is the shape of the kettle. Heating any normal kettle or casserole over an open flame is very inefficient.

The specific energy capacity of water is 4.183kJ/(kg K). In plain English that means that that it takes 4.183 seconds to heat a litre (= 1 kg) of water one degree (Celsius or Kelvin) if one Kilowatt heat power is added.

To heat 0.5 litre of water from 15°C to 100°C, one should therefore need an energy of...

0.5kg x 85°K x 4.183kWs/kgK =177.8kWs =177.8kilo-Joule.

If we add 2000 Watt (2kW) heat power right into the water with no loss, it will take just..

t= 177.8kJ/2kW=88.9seconds to bring it to boil.

Now, the makers of Origo 3000 claim that each burner produces 2kW.

Since I needed 4:30min. =270secons to heat that water,...

then the efficiency can only have been 88.9s / 270s = 0.33, or 33%. In other words; two thirds of the energy is lost!

Increasing the temperature on the flame will improve the efficiency, but my hunch is that that there is a lot more to gain from improving the kettle than from modifying the stove. Thinking of how the boilers of steam locomotives are built, should give a hint...

Arne

PS: Just to compare, now I tested my domestic 2kW electric water kettle. From cold, it took 118 seconds, and on the next test, with the now warm kettle, it took 93seconds to boil that 0.5 litre. That gives about 75 and 96 % efficiency...

Mark Thomasson wrote:

Good work Arne,  have you tried it with the pan in place?  It may help... or not. 

That is a very good point, Mark!

I may well have over-focused on the yellow torch flame with no pot or pan on the burner.  Today I made several boil-tests on ½-litres of water. I have to say that whatever version of the booster and set-up I used, my best time with the booster on was 20-30seconds worse than with no booster on (and copper tube removed).

The time to boil 0.5 litre was 4:30 minutes at the first test with only the original burner. On later tests without booster, the time to boil went up to 5:20 min. The difference between the tests was that I had to fill water from a new can, which had been sitting under the cabin sole, so may have been a bit colder. The other was that the kettle now was wet on the outside, after cooling it down before next test. I noticed it took quite some time for the wet kettle to dry up on the outside.

Still, the best I could get with the booster on and wet kettle was about 5:45 minutes  -  25seconds slower than without the booster on.

Sooo, I am now listing several degrees to this conclusion:
Those cunning Swedes who designed the Origo 3000 alcohol stove has done a quite good job. Look at the photo to the right, below. The primary flame is coming up that central tube. With no pot on, the flame rushes right up without getting mixed in more air. However, there is a gap outside that tube where air can rise easily. With a kettle or pan on, this air will partly mix with the central flame, and the result is a better combustion than with no kettle on. It isn’t perfect, but not bad either. There is some blue, red and white in the flame at full power. As the burner is turned down, there is more and more blue in the flame, and it is fully blue on minimum setting.

It seems that my booster was a failure, but at least it was interesting  -  and

 ..a negative result is also a result...

Arne.

PS: How is time to boil of 0.5 litre of water on your stoves? I guess the 4:30min I achieved, was with 15°C water and, as said, with a dry kettle.

PPS: I have a couple of ideas left to try, but...

Good work Arne,  have you tried it with the pan in place?  It may help... or not. 

Secretly I'm hoping that only the bike pump works and there will be a youtube video of Arne pumping up his supper  :-)  Or, perhaps a black-smith's bellows instead.... nice and low tech, just like the Junk Rig.   Seriously though, I wonder if the combustion might also be effected by the heat sink of the larger ring of copper?  Thanks for sharing the results.