Primary to Secondary Ratios! Paint Can Wood Gas Stove Optimization! Wood Gas Stove Science| Part 7!
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- เผยแพร่เมื่อ 17 ก.ค. 2021
- What is the right primary air to secondary air ratio? Join we while we try to figure it out! This portion of the Wood Gas Stove Science Series will be devoted to optimizing the beloved Quart Paint Can Wood Gas Stove. I want to make a good stove GREAT!! This is Part 7.
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The Wood Gas Stove SCIENCE series is an attempt to learn the science behind and how to optimize wood gas stoves. There are many videos of people drilling random holes in random cans and they are great! I have watched most of them and that is where I got my inspiration for this series. I will not show you how to build one until I have an optimized stove design. I am trying to find the correct ratio of can size, fresh air intake, primary and secondary air ports.
Thanks for watching and please stay tuned for more videos in this series.
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So much of the info I was looking for all in one fantastic video! Thanks!
Happy to help! Thanks for watching!
The primary to secondary air ratio should theoretically be 1:4. If the stove has a quarter of the holes in the primary inlet with respect to the secondary air inlet, not enough air will enter through the primary inlet towards the combustion zone to maintain the 1:4 ratio, but much less, due to that the fuel (pellets) is very dense and makes it difficult for oxygen to move through it. In your experiments, you found that the number of primary air intake holes must be much larger than the number of secondary air intake holes for clean combustion. This means that due to the density of the fuel, many holes are required in the primary inlet to achieve the 1:4 ratio. If twigs were used as fuel, much fewer holes would be needed in the primary air inlet, because the twigs allow air to rise to the combustion zone.
I do not believe you can assign an exact ratio due to the differences in can sizes. The wall thickness has a lot to do with the final ratio. You notice I do not talk about exact ratios, but about how to optimize your particular can stove. At one point I was sure a 1:5 ratio was correct but I realized there are many thing that contribute to the final design of each stove. Thanks for your comment, I appreciate everyone’s input!
What will happen, if we give ss wire mesh or grill at the bottom to allow primary air to pass more than 6 times of secondary air. Pls help me by valuable reply. Want to get shoots and tare free flame.
@@majharulislam5950 he didn't try that.
@@majharulislam5950it would work fine but things on the ground would catch on fire. Even on dirt, roots under the earth would smoke up through the earth. You'd have to put it on a brick or something to use it.
O.k
Helped Tremendously !!
Thank You !!
💯👍
Happy to help!
thank you. very helpful.
Thanks for watching!
Great video bud! Thank you for all your work and reporting.
Thanks for watching!
Awesome video Health! I love the way you your burner in a second can so you don't scorch the ground. :)
Safety first! :)
Leave no trace policies of hiking 🤝
I concur with that ratio finding. This has become more of an idle pastime for me rather than the one time make that it started out as. An industrial use sized church key has been a big time saver.
I enjoy making these and really like the community that revolves around them. One thing I have noticed... The precision spacing of the secondary holes really does make a difference. It is important that the flame creates a complete cap over the fuel to create a sealed pyrolysis zone. Thanks for the comment!
@@heathputnam9524 I've only used sticks never pellets and typically burn it on the patio for an hour or so just for enjoyment. The build up of ash and coals soon restrict bottom holes so I increased their size and number and added half inch holes 1/4 way up the sides with each new rendition. Choice of wood type and size keep my mastery of the flame humble. 🔥 My ultimate goal is to fine tune a stick feed burner able to boil just enough water for coffee inside a two man tent. I will stay tuned.
Well I think we should be able to come up with one that can boil a cup of water in just a few minutes. The idea with sticks is to break them up small enough that there is very little air space between them. Keep watching for future videos!
@@heathputnam9524 Can you make a graphical example? Thanks in advance.
@@fduran6993 watch his previous video. On twigs in the stove. He cuts up finger width sticks to pellet's length. Restricts airflow and probably helps not burn too fast (which is a real problem - burning a swedish torch inside lasts way longer than burning the same log batoned into smaller sticks)
Kind of seems you just want as much primary input as you can get without your fuel actually falling out. The ratio seems to just apply as a minimum for the secondary after you've maxed the primary...
At some point the primary is maxed out for the initial burn but the ratio really seems to make a difference in the conversion phase to burning the char… if it is not correct the fire will go out and smoke. If correct it will convert and burn the char with a beautiful blue flame! Thanks for watching!
Heath, is the gap thickness an important aspect? I know there has to be a gap for the heated air to flow up and out of the secondary holes. I have cans that have a small gap. Is there a "best" gap size?
Is there a point of diminishing returns have you gone to six to one eight to one 10 for one for more data points
I also think that you should use the stack effect and have a section in between your primary and secondary with zero holes in it to create more draft
I understand this would make it more difficult to cook on but then it would be useful as a smokeless heater
I did go to six to one several years ago and didn't see any gain over five to one. Although with the paint can stove the point of diminishing returns seemed to be around 4:1. I think the air space between the inner and outer can makes a difference in the ratio. I just haven't been able to take the time to scientifically prove any relationship. I think your idea of stacking cans to convert to a heater has validity due to the results I saw when I created a wood gas lantern. As soon as I added the "chimney" the heat began to emanate outward from it. We may be able to change the use of the stove depending on the pot stand/chimney we use... So many questions, so little available time! I wish I could retire and do this for a living! Haha! Thanks for the comment!
Have you tried cutting out the bottom of the primary can and replacing those primary air holes with mesh?
Nope, haven’t tried that. The ratio of primary to secondary and other design characteristics are important to the overall efficiency. Thanks for the comment.
Maybe try preheating the secondary air. That design makes a huge difference in a conventional wood stove with secondary air tubes. Too much secondary air and the secondary burn tubes cool down and aren't as effective. It's more than the ratio, the temperature of the secondary air makes a huge difference. The hotter the better.
In this design the spacing between the inner and outer can serve as the preheat. I have tried to decertify the air between the cans to lengthen the time to get more heat but that seems to hinder flow and caused weaker secondary air jets. I may hit the shop and do a little more experimenting! Thanks for the comment!
If I were trying to have a less roaring fire, can I make all the holes smaller? And add more of them? Or is that only resulting in alot of smoke
Check out todays video! It may answer this question for you! Thanks for watching!
Very interesting, typically online I think I’ve seen the opposite where people typically do a 3 or 4:1 ration secondary to primary, meaning the secondary has 3-4 times more ports than the primary. Have you tried it this way before? Part of me is almost thinking the reason it cleans up the burn when you increased the amount of primary holes is that you will have a lot of excess air going up through the primary essentially being used a secondary air by the times it reaches the top of the chamber. Much like running a wood stove with wide open primary air, it will burn clean but very very hot, even without secondary air added.
If you haven’t tried building one with reversed ratios I’d love to see you try it just to see!
I have tried this and the results were not good. The burn has no power and it smokes or lets off fumes. I will make another internal can and try the experiment again starting with a reverse ratio. We will see what we will see :) Thanks for the comment!
I will try to do this next weekend and post the video on Sunday. Thanks for watching! Please watch my other content on Wood Gas Stoves!
Thanks for the reply heath. Curious it made for a smokier burn. I may be wrong what I’ve read online, I always interpreted it that people had 3-4 times more secondary surface area than primary but I may very well be confused. But it will be interesting to see if it works with internal heated secondary air for sure.
I do find these wood gas stoves interesting as wood gas, at least in an internal combustion engine, burns at 1 to 1 ratio gas to air, one would think the 1 to 1 would have worked quite well if that were the case. I’d love to build a downdraft version of one of these for a heater. I actually just posted my first attempt at it if you check out my page and let me know what you think.
It seems to me because in all ratio,s there is good visible secondary burn the ratio isn,t that relevant. Any fire needs enough air for optimal burn ( with least smoke and soot ) So adding more holes in the bottom of the burn chamber is just correcting that basic shortage of air.
Isn,t there a third variable in the air flow ? Namely the air intake holes at the bottom of the outer pot. What happens if you let more, maybe to much cold air in ? Or less ?
I have explained this in several videos, but possibly haven’t made it clear enough. You want to start smaller with the air intake and keep increasing if the flame pulses while burning. This size seems to change with altitude also. Too large and the flow is less predictable due to temperature and wind. Hope this helps, thanks for watching and asking a great question!
@@heathputnam9524 Thank you. I was looking for the formula of ideal ratio. I am going to make a bigger fire pit kind of wood gas burner. Trial and error it will be. B.t.w. not much altitude problems here. Greatings from the Netherlands !
More is better on a fire pit as long as wind isn’t too much of a problem. Wind will push fresh air into the pyrolysis zone and may cause a puff of smoke.
I thought I seen one of your videos with a 5 to 1 ratio but can't find it now. Maybe I am mistaken. If you did do one could you point me to it? How did the two compare?
The 5:1 ratio is what I ended up at on the Vortex 5.4. I stated that ratio was the best, but as it turns out may other things affect the best ratio. I am still learning after al these years! Haha! The distance between the two cans, the length of the cans and the distance from the bottom the burn chamber sits along with many other parameters will have an effect on the perfect ratio for the particular stove. Sorry I do not have a better answer for you! Thanks for watching!
@@heathputnam9524 That makes sense. I guess a 4 to 1 may be a good starting point if the other measurements are the same.
I'm thinking about making a larger one about the size of a gallon paint can. May use some stainless steel canisters.
Not sure if the spacing between the outer and inner cans would have to be larger or not. Probably will be a while before I start on it. Too many chores right now.
Keep me updated! Thanks for watching!
Did you want to add a flame concentrator with a smaller hole? That may force the flame up so much that it may be sootless and getting more air as it hits the top.
I may try that! Thanks for the ideas and comments!
You might consider getting a small squirt bottle from the dollar store. so you don't spill the HEET.
Thanks!
Vortex A.V.E.C.
(In french)
Thanks for watching!
dear, i dont understand really well the ratio concept. Where is applying the ration?
Sorry for the confusion. My video called TLUD explained might help! Thanks for watching!
@@heathputnam9524 Can I make a stove with a radius of 70 cm with your proportions?
So 4:1 primary to secondary for wood pellets. Most likely need to reduce the primary depending on the type of fuel and air gaps it allows.
I would love to see this compared side to side to some commercial wood gas stoves! And a way to add an alcohol stove inside as well. Cheers
I’ll have to look for my Tangia alcohol stove to see if it fits inside. You are correct that depending on fuel the ratios all change. Thanks for the comment!
I’m not excited about commercial stoves but would test this stove and the Vortex 5.4 against a commercial stove but wouldn’t buy one just to do the test😂
I think reducing the height of the pot stand might improve the timings
You may be right or not ! 😂😂Thank for the comment!
It should be more secondary air than primary air. but you didn't do such a test
Actually I have done that experiment years ago. At the time that was what was available on the internet. If you want a can stove that will burn without smoke and convert from burning wood gas to consuming charcoal without going out and smoking then you cannot use a larger flow through the secondary than the secondary! I am however very open to listening to anyones suggestion and knowledge! Thanks for the comment!
4.75 too 4.75 .9.3 here again chiming in thank you.