Cave2k said:Blue/yellow/white flame indicates a clean burn. Orange indicates an under oxygenated (too rich/cooler) flame like an acetylene torch before the O2 is right for the mix. Wood gas should in some regard be looked at as natural or lp gas while burning. Before you can get the hottest flame in ng or lp you need the blue that turns to white/yellow at the tips. Blue then is primarily an indicator you are getting a good mix with enough oxygen. I have no storage and have been running my boiler to get the longest sustained burn times and have had my blower set way low to keep from getting smoke and burn out pockets in the primary chamber. Those problems were because my primary was too wide for the velocity of a wide open blower. I'm down to 9mm on primary. To get the blue flame though it is better to cut the blower way back so you can actually see the blue. Once adjusted you can reset the blower to a wider setting of your preference. It appears that you get a quicker transfer of heat with a wider blower opening but a shorter burn duration which is ideal to some with storage. A smaller blower opening means a slower heat transfer but a longer burn duration with less idling which is ideal for my situation and no storage.
Great observations and explanation, Cave. Do you check the flame color by opening the bottom door? I don't think there's any other way to do it.