[Stoves] Limiting factor for secondary burn?

[Crispin Pemberton-Pigott]

Dear Frank

You are really on the right track.  Impressive.

It will be difficult to match practise with theory if you do not have a 
meter for at least one important measurement.

The most important is O2.  You can get one cheap, and you need it.  From the 
O2 reading in undiluted exhaust, you can determine the excess air which is 
the most important factor in heat transfer efficiency.

Even if you know what the air flow should be, it is not determined by the 
hole sizes.  It is determined by what happens to flow through them and that 
is dependant on draft which is variable.  Trying to guess what is in the 
exhaust gases is hopeless.

What the CO is and the particulates are, you can leave to others, but you do 
have to know if you are putting in too much air while still in development.

If you have a meter that gives you 'Excess Air' it is fine, but they cost a 
lot more and are only really doing math for you, not testing something 
different.

O2 that is NOT present has been burned.  The better your stove, the less O2 
in the exhaust.  The more air you don't have going in the more likely you 
are to get a hot burn.

At some point, choking off more air reduces O2 still further, but creates 
masses of smoke (from not enough air).  It is now at the difficult point. 
Once you have the excess air down to about 100%, you enter the territory 
where you can increase the CO and particulates with further choking.  This 
is not a hard and fast rule, but you get the idea.  There are limits. 
Increasing the excess air a lot can often increase the CO and partculate 
production because the fire is cooled by all that unneeded air.  That is the 
condition of an open fire.

I am really impressed with your progress in understanding this.

Best regards
Crispin

----- Original Message ----- 

>I noticed that the primary burn seems to have a narrow window regarding
>the amount of air to keep the burn glowing. Too little and the burn ...