A bypass loop

I remember, on one of our radars used on Stavanger airport (where I used to work), the transformer oil in the high-voltage section of the transmitter was circulated via a cooler. The pump had no regulator. To limit the oilflow, a by-pass loop with an adjustable valve in it had been fitted. This easily let us reduce the pump’s net output.

I think this technique could be the way to regulate the net output of this peristaltic pump, as well, without putting strain on it. The alternative is to just have this bypass loop set at a constant rate and then use a valve close to the burner do the regulator work, as described by David. Probably better, that.

This setup could even have worked on the temperamental Taylor diesel heater (76D?) I had in Malena. That heater had an automatic shut-off in case the flame went out. The pump would keep on working, but thanks to the pressure-limiting bypass, no damage would be done.

Arne

PS: With that bypass loop fitted, one would need a pump valve to keep the fuel from draining back to the tank when shutting the pump off.

I think a peristaltic pump like David found is a good way to go.  I've used them in the lab a little bit and they can be made to deliver fluids at a reliable rate.  However, I never took one of those apart to see what they were using to drive the motor.  

The nice part of the peristaltic pump is that it is leak proof and maintenance free.  It just uses cams that squeeze the hose shut and push the fluid along.  Here is a link to another version on e-bay that shows this more clearly.  On some versions you can change the size of the tubing you are using to change the rate they pump at.

My first thought was to use an inexpensive DC-DC buck converter to drive the motor.  This would compensate for changes in the DC voltage of the boat and keep the motor speed constant.  However, I think there might be  a simpler route.

Here is a link to a unit that might be plug and play.   If I've read the fine print on the AC-wall wort correctly, this is actually a 12V unit.  If I were attempting the conversion I think I would start with something like this.  It would be worth checking its flow with the ships engine running and with the engine off.  If the extra voltage from the alternator made it change rate, then it might be necessary to add an inexpensive DC-DC converter.

Having said all that, we've had good luck with the regulator that came with our Dickinson Pacific stove and it doesn't require any electricity.

I wonder how that pump is regulated; just by adjusting the DC between 0 and 12V? Or should it be regulated with a pulse-length regulator?

The pump's capacity appears to be on the high side for this job. Only about 2% of its capacity is needed for working in a stove, it seems. I am unsure how it will react to a needle valve on the output to limit the flow.

It appears to me that the main challenge with both heaters and cookers is to get a reliable, steady and adjustable flow of fuel. Drip-drip-drip, just like that, steady.

The drip regulator on my first Taylor Diesel heater was a disaster, almost literally: Only luck and the fact that I had copper-covered all walls around the heater prevented it from burning down Malena and the rest of Haugesund (jazz festival) when the ‘regulator’ ran away.

The next, a Taylor kerosene heater (in Johanna) with an Optimus/Primus burner, was a bit better, but here the opposite happened: As it got hot, is gradually turned itself off. It kind of choked itself although the pressure was fine.

Then there is the Reflex heater.
This has a delicate regulator that works magnificently until some tiny imperfection in the diesel fuel makes it cock up. And then, just a look in the instruction manual  and the ‘exploded view’ of its internals makes one back away: It is about as complicated as a WWII Norden bombsight.

The improved alcohol burners which David Tyler has told us about, sound interesting, but even these are not really easy for anyone to fit and make work.

What if:
A few years back I spent a few days nose-up in a hospital bed. The driprate of the drip (salt water?) I got in my arm was adjusted about as on my Taylor heater. Its rate also depended on my position. Even if I lifted the arm only a little, the driprate dropped noticeably. Then there was  another toy connected, called a ‘pain pump’, adding to the fun. This thing was electric with an internal battery, and it provided a calibrated driprate, completely independent of how I moved.

Now, that is what we could use: A tiny, calibrated, battery-driven pump. With such a device, replacing all sorts of mechanical fuel regulators, we could even put the tank below the stove, which in my view is safer. Such a pump would transform care-needy and downright unsafe heaters and stoves into our best friends.

Where do we find such pumps  -  without raiding the nearest hospital?

Arne

Graham Cox wrote:I was only joking about designing the perfect stove, though I seem to remember you have been working on a stove project.