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Post by Vortex on Dec 10, 2023 11:12:28 GMT -8
I also removed the grid at the primary air (felt like the holes were too little) and replaced them with some vermiculite. Bit of a sloppy job but just testing.. I found it hard to find the expanded metal with the right size holes, tried to buy some online but they were all too big or too small. Not long after I was replacing the air filter on my digger and noticed the outside of the filter was covered with the perfect size mesh, so dismantled the old filter and got enough for my stove and a spare. With the optimum top chamber setup you should be able to have both. It's possible that gap already has a high surface area to volume. might explain why you had to remove some vermiculite board from the top chamber. The ceiling of my top chamber is a hotplate which radiates off heat very fast, but I've never tried insulating it to see how that would effect combustion. Cooler gases are denser and so would probably move slower causing more resistance. As I see it there are 4 main areas that effect the combustion: * Rate of off-gassing of the fuel (which largely depends on; temperature of the fuel, the type and moisture level of the fuel, and the amount of exposed surface area of the fuel). * Amount of air/o2 supply, * Resistance of the system * Draw of the chimney For example, if you put a load of smaller pieces of dry building timber into a hot firebox on top of a bed of red hot coals, with the air supply full open, on a stove with no mass or contraflow - so very little resistance - and so no restraint on all the hot gasses rising in the chimney - What do you think will happen? |
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jonasp
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Post by jonasp on Dec 12, 2023 0:56:41 GMT -8
Haha i love the recycling of the grid material, I got my first grid out of an old computer case hehe. I am searching for that optimum seems to be a hard one for me and or my system.. Crazy overfuel for sure. So I opened a bit more of the wool so if it was a restriction it can go 2 ways now and shouldn't make any major resistance. It's not an obvious difference but I do feel it changes will know more when i burn a couple more fires. Yesterday the fire was Ok, no overfuel but slow startup and vortex could've spinned a bit faster. Today I moved the fold over resistance (still 100 CSA) to one side to have less of a SA/V. Overfuel at the peak, good spinning vortex, i also need to increase air to keep my vortex from going orange after the peak. First signs of overfuel: drive.google.com/file/d/1KRUth2drjlzINIawkLMY49hQG7Qo5u0V/view?usp=sharingFurther overfueling and me opening the door slightly and closing to see the influence. drive.google.com/file/d/1KQglkbZitEEPJtBQQR4HhFavqsTyO2LF/view?usp=sharingWhen I open the door a crack bit, it controls the overfuel, makes the vortex spin faster which will push the hot gasses faster through the system (maybe less heat buildup) but will also in the long run make the fire burn faster so more fuel.. I hope I'm not boring anyone with all my updates |
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Post by Vortex on Dec 12, 2023 7:18:47 GMT -8
If anyone's bored they know how to stop reading  Your 2 videos look to me like it needs a bit more resistance in the top chamber, and a maybe a little more air. My latest experiment results were excellent with the increased SA:V in the enlarged top chamber: donkey32.proboards.com/post/39402/threadTrev |
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jonasp
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Post by jonasp on Dec 14, 2023 3:38:51 GMT -8
I've tried 2 more configurations, yesterday i extended the restriction to the back. (SA/V = 1.52)  really great vortex and an slight overfuel which was instantly fixed by opening the door a crack bit. Today I moved all the pieces to the middle for more SA/V ratio. (would be 1.56) A bit slower vortex but still spinning nicely, I only saw a tiny tiny overfuel which got back to stable when I added a bit more air. I already ran the first configuration (but all the pieces were on the left instead of the right) before eliminating the above oven restriction so the restriction above the oven did have an impact on the overall back pressure, now it's easier to fine tune it. Seems like 1csa is the best restriction and fine tuning that restriction is way easier when playing with SA/V. I do get the orange vortex after peaking and when there's a lot of wood getting burnt, mostly get this fixed by adding a bit more primary air. Do I open the bottom air only when I'm at the coaling fase or also to prolong the fully formed vortex? (I've read in your testo results that adding bottom air equals more co output but not sure how applicable it is because of other changes). Also another question, if i would prod the fire when vortex is getting slower and slower to get it burning faster again, would that be bad for a clean burn? also the same question for the coaling fase. Overall I'm really happy with these results so far, going to make some small tweaks to see the influence and probably experiment more with how the primary air gets blown in. Thanks again Trev for all the information and all the experiments you've done! |
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Post by Vortex on Dec 14, 2023 6:29:48 GMT -8
Oh great, sounds like you're getting it dialed in nicely. I have to go out now so will answer you properly later this evening. Trev
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Post by Vortex on Dec 14, 2023 12:12:52 GMT -8
My experiment today was with an SA:V of 1.57, perfect burn but weather was dead still outside so no wind draw on the chimney. I posted the details on my thread.
I like your way of equaling out the draw on the vortex with the deeper afterburner on one side, so it doesn't pull on the dominant side more than the other, I might have to try that.
The glowing vermiculite around the peak of the burn can make the vortex look a bit more orange, so long as the vortex is fully formed and there's no overfueling then the O2 should be OK.
The bottom air is fine anytime after the burn has peaked, but it should only be a small amount, like 2% to 3% csa. Bottom air during the flame phase will increase the rate of combustion in the firebox, so as soon as the fire has obviously peaked reduce the primary a little and open the bottom air. This increases the combustion rate in the firebox and maintains the vortex fully formed in the afterburner longer. During the coaling phase close the primary air almost completely, CO burns like a gas flame just hovering above the coals, so the O2 needs to peculate up though them and not be blown out by primary over the top.
Don't poke the fire until the flame phase is over as that causes big spikes in CO. Poking it to break up the chunks and cover any holes that have burned through is good, as holes allow the bottom air to pass the coals without aiding the combustion of the CO.
Trev
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jonasp
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Post by jonasp on Dec 15, 2023 5:42:38 GMT -8
My experiment today was with an SA:V of 1.57, perfect burn but weather was dead still outside so no wind draw on the chimney. I posted the details on my thread. I like your way of equaling out the draw on the vortex with the deeper afterburner on one side, so it doesn't pull on the dominant side more than the other, I might have to try that. The glowing vermiculite around the peak of the burn can make the vortex look a bit more orange, so long as the vortex is fully formed and there's no overfueling then the O2 should be OK. The bottom air is fine anytime after the burn has peaked, but it should only be a small amount, like 2% to 3% csa. Bottom air during the flame phase will increase the rate of combustion in the firebox, so as soon as the fire has obviously peaked reduce the primary a little and open the bottom air. This increases the combustion rate in the firebox and maintains the vortex fully formed in the afterburner longer. During the coaling phase close the primary air almost completely, CO burns like a gas flame just hovering above the coals, so the O2 needs to peculate up though them and not be blown out by primary over the top. Don't poke the fire until the flame phase is over as that causes big spikes in CO. Poking it to break up the chunks and cover any holes that have burned through is good, as holes allow the bottom air to pass the coals without aiding the combustion of the CO. Trev It does work to equalize the vortex a bit. I'm making further small adjustments and update here in a couple more burns but so far every burn is going well with minor hiccups. Oh thanks for that explanation it helps me to understand it better, learning everyday. Today i centered the burning coals over both bottom slits (mostly the back slit is fully covered but the front only partially) and it was amazing to see the coals react. There were steady long and thin flames going from the coals, it was kinda mesmerizing to watch this combustion hehe |
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Post by Vortex on Dec 31, 2023 2:52:42 GMT -8
What's your effect on the vortex when you have strong winds? What I observe is way to strong pull which tends to make a full vortex hard (keep in mind I don't have any cowl that can limit the wind pull). The uninsulated part is also another 4-5meters high I meant to ask about this but forgot. Are you saying you have 4 to 5 meters (13' to 16') of uninsulated chimney pipe outside above the top of the old clay chimney, and if so why? masonryrocketstove post today in the thread about chimney sizing reminded me of the point I was going to make: The chimney will be 16 to 18 feet tall, outside the building envelope. With a mass heater that harvests the lion’s share of heat before exhausting to the chimney stack, I think your chimney outside the building envelope is going to be every bit as much of an obstacle to sufficient draft as necking down the pipe diameter. Box stoves that dump enormous amounts of heat into the chimney can oftentimes cope with a chimney stack that’s outside the building envelope… but the cooler exhaust temps from a storage stove will more often choke and stall with an external chimney stack, because the cold outside air cools the flue gasses much more rapidly than a chimney within the building envelope. |
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jonasp
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Post by jonasp on Dec 31, 2023 4:14:46 GMT -8
What's your effect on the vortex when you have strong winds? What I observe is way to strong pull which tends to make a full vortex hard (keep in mind I don't have any cowl that can limit the wind pull). The uninsulated part is also another 4-5meters high I meant to ask about this but forgot. Are you saying you have 4 to 5 meters (13' to 16') of uninsulated chimney pipe outside above the top of the old clay chimney, and if so why? masonryrocketstove post today in the thread about chimney sizing reminded me of the point I was going to make: With a mass heater that harvests the lion’s share of heat before exhausting to the chimney stack, I think your chimney outside the building envelope is going to be every bit as much of an obstacle to sufficient draft as necking down the pipe diameter. Box stoves that dump enormous amounts of heat into the chimney can oftentimes cope with a chimney stack that’s outside the building envelope… but the cooler exhaust temps from a storage stove will more often choke and stall with an external chimney stack, because the cold outside air cools the flue gasses much more rapidly than a chimney within the building envelope. Oh no, I must've explained it poorly, the chimney is as followes. 1meter in the bell (insulated with ceramic wool) 1 meter insulated chimney to the ceiling of the room I have a clay rectangle old chimney 200mm running 4-5meters and I've put a 180mm uninsulated chimney pipe inside the clay chimney. In the empty space between clay chimney and new chimney I filled it up with vermiculite for insulation. The cowl is just a beefy slab of concrete to prevent rain from going in. |
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Post by Vortex on Dec 31, 2023 5:51:12 GMT -8
Ah, OK yeah that make more sense, your chimney is actually insulated just not the ready made variety. What size is the opening at the top of the chimney around the concrete slab? I found 2 csa worked well on the cowl I made. The other thing that can be useful in really strong wind is an old fashioned chimney damper: vftshop.com/images/others/Stove/stovedamper.jpg |
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Post by martyn on Jan 1, 2024 3:56:17 GMT -8
I was looking back at some videos and I found this one which also shows a slightly larger top box formula and even a larger vortex chamber but it seemed to resist over fueling quite well!
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jonasp
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Post by jonasp on Jan 4, 2024 0:17:31 GMT -8
Interesting video martyn does seem to be more the effect of DSR3 core. maybe less overfuel but also a bit less warmth? I'm still slowly tweaking. After making 2 exits on the top chamber I also made the insulated exitpipe in the bell 4cm shorter since i felt the draw was not enough when it's not cold and no wind at all outside. Today I've had a quite good of a burn, small flares of overfueling but not that much. (and need to slide the resistance more to the left to equalize the vortex) drive.google.com/file/d/1FVILmw6400HQcfmoFu5zUkOuYdYJgSB8/view?usp=drive_linkI do still get smoke/damp from my chimney not sure how concerned i have to be about this... It has been very wet these past days so a bit of damp should be normal i think also my humidity in the house i quite high.. The smoke/damp comes from the pipe and not around it. Here are 2 video's of the smoke the close up i tried to give another background but it was hard to film on a ladder. It does seem to disappear so I think it's mostly damp but sometimes the smoke is a bit more grey-ish, seen in the first video. drive.google.com/file/d/1y7bCjFBTJuWOcqxS-nSy0UFvBpyZ_a0I/view?usp=drive_linkdrive.google.com/file/d/140Hmc_Uh32SwVmYtIOh_--VtrT8hdnWT/view?usp=drive_linkNot sure if anyone can tell me more clearly what this looks like? |
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Post by martyn on Jan 4, 2024 5:50:29 GMT -8
That looks like steam not smoke, the fuel you are burning will contain a certain amount of moisture, I see this quite a lot in the winter.
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Post by Vortex on Jan 4, 2024 11:35:15 GMT -8
The high volume secondary air setup would only work on mine if I left the bypass open, the resistance of the mass slowed the gas stream down too much. All that extra air would just dumps most of the heat out the chimney anyway, good for a smokeless outdoor cooking setup though.
Your first video above looks like the stack is burning from the bottom, and only a small load in that huge 7" firebox, both things that I would normally expect to lead to a less than perfect burn, but the vortex looks great, so you must be doing something right. The last video is steam, which is more visible in very high humidity as the air is already saturated
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Post by masonryrocketstove on Jan 6, 2024 0:32:06 GMT -8
That looks like steam not smoke, the fuel you are burning will contain a certain amount of moisture, I see this quite a lot in the winter. Yep, real-world woodfuel always contains some moisture, but burning hydrocarbons also creates even more water vapor that didn’t exist in the wood as water.. like, even if your woodfuel had 0% moisture content. Combustion “cracks” the organic hydrocarbons, while heat and oxygen (O2) keep the chain reaction going. The liberated carbons (C) oxidize to carbon monoxide (CO) and carbon dioxide (CO2,) while the liberated hydrogens (H) oxidize to newly-created water (H2O). The last video is steam, which is more visible in very high humidity as the air is already saturated I think it’s kinda cool how you both observed that from 2 different angles and you’re both totally right. As air temperature drops, it can hold less and less water vapor (the % saturation level rises as temperature decreases) and more water vapor will condense as visible steam droplets, because of that increase in relative humidity at colder air temps. I do still get smoke/damp from my chimney not sure how concerned i have to be about this... Even the cleanest flue condensate is more acidic than pure water, (pH 7, neutral) and can corrode steel, brick, and stone, especially limestone. ( As the water vapor condenses inside the chimney, it turns to liquid droplets in that column of CO2-rich flue gas, pulling carbon dioxide into solution, which forms carbonic acid (H2CO3) ..it’s pretty much the acidity in setzler water and fizzy “carbonated” soft drinks that can remove limescale and rust in toilets. It has a pH of 4.68, about as acidic as tomato juice and acid rain, but not as acidic as lemon juice.) It’s not an emergency type situation, but it’s not something you want to ignore and let keep happening over the long term. (Once the water evaporates off, the acid is gone, until the chimney pipe condenses again. So it’s not like the acidity builds up over time, but the corrosion can slowly progress and worsen each time the chimney condenses.) To keep water vapor from condensing inside the pipe, you may need to do something to raise the overall chimney temperature (a warmer pipe can more easily stay above the condensation temp AKA “dew point.” ..Especially toward the end when the fire is dying down, putting out less heat, and flue gasses are moving up the pipe a little slower.) Not real sure what the best method for your particular stove would be.. Sometimes it means the “train” of the flue pathways inside a stove need to be shortened a bit so the mass harvests slightly less heat. That can keep the chimney hotter. If the condensation isn’t frequent (like only happens on the highest-humidity days,) it might work to run a stove with the bypass open for the full burn so it harvests less heat, staying above condensing temp. ..but sometimes that means relocating a bypass further downstream so the stove still maintains some efficiency, (so it still stores some heat even if it’s run on an open bypass the whole burn.) Could you maybe try running the stove with open bypass for a longer time at the start of the burn? I’m thinking maybe just long enough to get the chimney pipe hot enough so it stays above dew point even after that bypass is closed a little later in the burn? ..or does leaving the bypass open longer at the start lead to overfueling? Just brainstorming here: Maybe a second bypass could be installed at a midpoint between the bypass nearest the firebox and the chimney? I’m thinking you’d only need to use that secondary bypass on infrequent high humidity days to keep the chimney pipe hotter. |
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