ceramic burners

[michael howarth 1Participant @michaelhowarth1]

I have been using ceramic burners fired by butane for a while, with no real problems. Recently, reading around the subject I have discovered that there are at least two schools of thought as to what sort of flame should be produced. Some seem to like a red/orange incandescent glow on the surface of the ceramic. Others go for a blue cone effect, saying that the red glow is likely to damage the ceramic/cause blowback/is less efficient. Both effects can be achieved by varying the primary air ie moving the jet. I prefer the glowing effect for what its worth. I have no knowledge of which is most efficient. Any thoughts?

Mick

[bernard towersParticipant @bernardtowers37738]

Going by yhe way most gas burners behave I would have to go for the blue cone effect!. I always thought (rightly or wrongly ) that the orange flame was too much fuel or shortage of air.

[Mark RandParticipant @markrand96270]

Speaking from profound ignorance, but would the compromise of a blue flame with an attached brick/ceramic arch be the ideal situation?

[JAParticipant @ja]

The combustion is too rich if there is a yellow flame. It is less efficiencient with partially burnt products being produced which, in large quantities, will do you harm. In practise, the radiation from the yellow, carbon rich, flame could overheat the burner.

The ideal is a translucient blue flame.

I note that Mike mentions an orange glow on the ceramic. I guess that this is with a blue flame. If so, does it only occur at low gas settings? I don’t see it as a direct combustion event but the overheating could damage the burner.

In the best engineering tradition the question has not been answered.

JA

[michael howarth 1Participant @michaelhowarth1]

Thanks gents. As it happens, in the true spirit of compromise, the burner that I have just made burns with a blue cone in the middle with orange/red glowing ceramic round the edges. Increasing primary air by moving the jet backwards in its holder, so that the tip is only just showing in the air hole, gives a fiercely orange/red glow all over. The burner is only 1″x 2.5″ and i wonder whether the No5 jet (orifice 0.2mm ; 55gms/hr), is theoretically a  little too much. The burner is for a Gauge 1 tank engine (Bond’s Tank) and I am anticipating some flame characteristics changing under the effect of draught once it is installed. At a guess I would say that draught would increase the flow of primary air.

Mick

[Robert Atkinson 2Participant @robertatkinson2]

It depends on what thermal transfer the boiler is designed for. Most will be for conduction from hot gases. A glowing red element is primarily a radiative heat source. Most of the radiation will be absorbed by the fire box and some of that conducted outside and lost.
So a plain flame is probably best.
You want hot gas going through the boiler tubes, not radiation in the firebox.

Robert.

[Clock polisherParticipant @clockpolisher]

Good evening,

Methane gas flames should burn blue with small yellow tips at the very end of the flame.

Imagine an artists brush, shaped like a bullet with a sharp point. Dip it fully in blue paint and then dip the very ends of the bristles in yellow.

It’s the method used, since time began, to set up gas burners in the absence of any measuring equipment.

No yellow means too much air/not enough gas, too much yellow means too much gas/not enough air.

regards,

David

 

[ChrisLHParticipant @chrislh]

Taking Robert’s point, it rather depends on the design of firebox. If it is water jacketed as in steam locomotives, a radiant flame is considered very desirable as the heat transfer per unit area is much higher than for convection. Can’t put any numbers to it I’m afraid.

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