The 8R that I have recently resurrected was burning with a considerable amount of yellow in the flame tips. Now I knew that the jet was brand new and I had also fitted a new tank wick (C/W gauze filter)so it was unlikely that the problem was caused by an excess of fuel. I was a bit puzzled by this but then I remembered reading somewhere that the height of the burner top plate can influence the efficiency of the burn. Problem was that the author had not described exactly how the height adjustment should be made (i.e. up or down) but, to me, it seemed logical that raising the burner plate would allow the vapour stream to reach a slightly higher velocity before being 'braked' by the interference to the airflow by the plate(?). I decided to experiment by raising the plate in increments to see what happened and began by gently bending the plate's four 'arms' downward so that the ends were about 1mm lower thus raising the the plate (when in situ). Firing up the stove produced a nice blue flame with only the slightest hint of red tinge at the tips. I was amazed to see that such a small difference in the height of the burner plate could make such a big difference to the efficiency of the burn - I didn't realise it was such a critical parameter. Dave.
Hi Dave, I hit the exact same problem on my 8R clone. Following advice from Ron, I raised the flame spreader (like you just did), and it worked like magic. See this topic: https://classiccampstoves.com/posts/138029 Yonadav BTW, the stove shown in my topic above was stolen from me a couple of months ago (together with my car). The car was insured, but not the stove. :-(
Davwal, interesting observation, thank you for posting it. I looked up flame color in my copy of the Combustion Technology Handbook and this is what it said: "(If the flame is supplied with) 100% primary air, it would have a sharp pale blue flame since all of the air for combustion is mixed with the gas and is ready to ignite as soon as it reaches the nozzle. A flame burning with 75% primary air would be characterized by a double blue cone and be a little bit longer since 25% of the gas molecules need time to find oxygen before they can burn. At 50% primary aeration, the flame becomes still longer and softer with some orange tints. At 25% , only a slight amount of blue remains in the flame and the flame becomes much longer with yellow being the predominating color." Even though this description is for methane combustion, it appears that the color of the flame is related to how much air is being mixed with the fuel. Pushing the flame spreader up may be allowing a bit more air to mix with the fuel before it burns, giving it more blue color. Anyway, that's my story and I'm sticking to it!
Yonadav, I did a search but the topic you gave the link to did not come up - would have saved me some angst. You have raised your plate a lot more than I have, mine still sits below the level of the burner cup yet the improvement is amazing. Sorry to hear about your car and the lack of insurance on the stove - you must get your priorities right in future .................
Yup, Sparky hit the nail on the head. Higher plate = more oxygen and better mix. To a point. go too high and the burner bell won't absorb enough heat to vaporize, and you get a weird flame pattern. Davwal the velocity of the fuel vapor is, as with all gases force through any orifice, at its highest at the orifice opening. It'll only slow down from there. Mike
Mke, I was aware of that but it will slow down dramatically at the point where the top plate starts to disrupt the the flow. Raising the top plate a fraction delays that point a little so allowing the vapour stream to flow a little faster (or at least not be degraded so quickly) than it would have otherwise. The faster the vapour stream the more air (oxygen) it will pull in to the mix. Well that that was the way I reasoned it anyway !! Dave.
Thanks Davwall and all the experts on this forum for this tip. Some time ago I guess I accidentally pushed the spreader plate on my SVEA and suddenly got the yellow tipped flames. I didn´t realize it at the time and couldn´t figure out what went wrong. Following your advice I lifted the plate a little and got bluer flames.....then I overdid it and got horizontal flames....Finally I got it right. As you observed it is really sensitive to variations in height, even a fraction of a milimenter makes a difference in the color of the flame. As an added bonus and since white gas is not available here in Argentina i tuned it for "diluyente" or "solvente". (Previously I used low octane unleaded gasoline) The following pictures show the SVEA at full throttle, and at minimum power. The last picture (yellow can on the left) is what you should ask for if you need white gas for your stoves in Argentina. By the way this stuff works very well in my Primus Gravity MFII. Thanks again and regards
