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Post by Donkey on Jan 5, 2015 19:10:36 GMT -8
Or a wedge shaped tube with the long point aimed directly away from (upstream of) the port and the short face parallel to it. Slots would be at the corners, on the parallel (short) face.
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Post by ericvw on Jan 5, 2015 20:01:09 GMT -8
Sketch! Sketch! I say!
I can sort of picture it, but hey, Donkey- SKETCH! Happy new year, SKETCH!
Eric VW
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Post by peterberg on Jan 6, 2015 2:09:47 GMT -8
I think the square tube with one corner pointing to the port as Jliebler said is probably the best layout. It will allow the tube to be closer to the port so the air slot is in the area where the underpressure starts. Whether the single slot or the double one close to each other is better remains to be seen.
Main point of the versions so far isn't the quality of the burn, which is excellent, but the high O2 numbers which I feel could be a lot lower. When we take the idea of the square duct turned 45 degrees with a wider port and the tube shoved even more to the riser this could place the air slot in the area with the lowest pressure. In terms of adding air this is the best spot obviously, right before the expansion starts and the vortexes in the riser will take care of mixing the combustibles with the preheated air. Both sides of the port should be about 1.1 times the base dimension, with the sides of the port at 45 degrees as well. Maybe this is a bit of an air castle, I try to work it out in a sketch today for you people to comment on.
Matt, the discrepancy between your brand new Testo and my veteran specimen is probably due to a fault somewhere in the O2 part of it. In December I've sent the equipment to Testo Netherlands in order to have it calibrated. Just before Christmas they mailed the thing was sent to Germany headquarters because even with a new cell the readings were too low.
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Post by matthewwalker on Jan 6, 2015 8:28:25 GMT -8
Great stuff all. Peter, I'm glad to hear there is some reason for the discrepancies. It has been bothering me to no end, I keep thinking I'm doing something wrong here.
I love all these ideas! I'll do what I can to implement them and see what comes of it in the coming month.
I'm currently working on fabricating a proper door for the thing. Metal work is not my forte, but I'm getting there. I've been struggling with both controlling primary air precisely and measuring my opening due to lots of leaks and warping door parts and such, as Peter picked up on earlier. I should have this done and installed by the weekend, and then I can get back to trying some new configurations and attempting to improve things even more. Peter, the leaks have for sure had me running the thing with a bit more primary than I would like, leading to more off gassing, leading to a need for more downstream air. Once I get the incoming air completely under control I'll be better able to tune it. So, stand by, more to come!
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Post by jliebler on Jan 7, 2015 15:24:27 GMT -8
I'm learning to use sketchup, here is a crude version of what I hope to incorporate in my new house. It's an 8" side feed to use a commercial door. The combustion air comes up from a duct in the basement which is also the ash pit, primary air enters the firebox down low and secondary air is over the top of the firebox then down through a square tube with the slot on the corner (the steel tubes are outlined only in the sketch). SIDE DRAFT BATCH w S ch.skp (253.89 KB) I think this is a double bell with the first, much smaller bell housing the oven and the second bell includes the raised heated hearth. A plunger tube with a bypass just below the first bell feeds the chimney. What is shown in the sketch is the "core" of bricks laid as shiners and there will be another layer of conventionally laid bricks around the "core" to comply with the double wall requirements in the US. I've left out bunches of bricks to illustrate inner details. |
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Post by jliebler on Jan 7, 2015 21:01:18 GMT -8
I'm re-thinking this, the horizontal tube at the top is a challenge to hold in position & I haven't figured out any way I'd find acceptable (I'll probably switch to a bottom location because it's so simple to use gravity). For the tubes my thoughts are: Use 12 guage mild steel (1/8" thick) welded from sheet stock bent into angles. The vertical tube is 3" outside square cross section or 2 3/4" x 2 3/4 inside (7.56 sq in). The slot is 3/8" x12.5" (4.7 sq in). The horizontal tube is 4 1/4" x 2 1/4" outside (8 sq in inside). System CSA is 50.25 sq in. With the bottom horizontal tube the primary air inlet is directly above the tube as it goes through the side wall of my firebox.
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Post by matthewwalker on Jan 11, 2015 9:25:02 GMT -8
I built a door, what a pain! Still tuning the primary sizing and closure mechanism. Two primary inlets, one is low through the fuel, one is air wash flowing up across the window. Currently using a couple different closures to adjust the low primary/air wash ratios...Nothing definitive to report, as I'm playing with it a lot right now.   |
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Jan 11, 2015 13:56:43 GMT -8
I know how you feel Matt - they are a pain to make! Makes you realise why they are so expensive to buy. I read somewhere that stove doors were family heirlooms in Scandinavia and taken out when a family moved house - I can see why!
Looks good though.
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Post by jliebler on Jan 11, 2015 20:28:33 GMT -8
Since I don't have the tools and talents to fabricate a "proper" door, I'm forced to pay, though the nose, for a door in the commercial market and the paucity of choices constrains my design. The best I can do, even with an 8" system, is make the firebox bit too tall. I've posted newer versions, with the "Walker" channel supply tube in the firebox floor, in the "heating" forum. In the newer versions I sloped the "back" wall of the firebox, one can do things like that easily in sketchup, none the less I don't think the molds will be too difficult to make.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Feb 21, 2015 3:28:02 GMT -8
My experiment isn't as elaborate as yours Matt but seems to work nonetheless. I put a 2" stainless steel tube along the bottom of the firebox with one end just sitting between the 'letterbox' at the riser end. At the door end it sits approx. an inch short of the door.
   
 
Having not lit a fire for a week the bell was cold. I started a fire and then once an ash bed was established filled up the firebox and closed the slider for the P-channel. To get the tube up to temperature I put a lump of firelighter in the tube and lit it. The primary air was open wide. When I came back 20 minutes later it was blazing away so fetched my analyser to take some readings.
At 66ppm to 70ppm the CO levels aren't as low as yours. They stayed stable for 25 mins with the P-channel closed. I was playing with net and gross efficiency readings so the efficiency in the screenshot in net. Subtract approx. 5% or 6% to get the gross figure.
After a refill the readings settled back down. The analyser has a max 10,000ppm for CO so I remove the probe temporarily when it spikes to save damaging the sensor. Stack temperature was 60°C after a two hour burn. It always leaves a bleached white firebox :-)
I'll connect the laptop up next time to record and chart the readings. |
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Post by peterberg on Feb 21, 2015 5:10:47 GMT -8
Morti, you mean just a straight round pipe on the floor of the firebox? When that's correct you fed the secundary air at the bottom of the port instead of at the top. Very simple and also very interesting! How does compare these readings with earlier testruns with the p-channel as air supply?
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morticcio
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"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Feb 21, 2015 7:03:27 GMT -8
Hi Peter,
Yes, a straight tube on the floor of the firebox. No other modifications.
I haven't recorded a full run yet but it appears to give slightly lower CO readings. Efficiency is similar at approx. 91% gross.
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Post by matthewwalker on Feb 21, 2015 7:39:59 GMT -8
Yes, that's how I started figuring this out as well. Just a straight tube along the floor to the port entrance. Nice to see you are playing with it Andy, did you try closing the primary a bit? I'm still hanging in there at around 2"sq. primary. There are times I can reduce it a bit, but that's what works almost always.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Feb 21, 2015 10:47:55 GMT -8
I'll have a play with the primary when I light the stove later. It appears to run better when the end is in letterbox. I'll try a longer tube and poke it through to the riser. I have to confess I have Lo-CO envy after after seeing your results Matt  |
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Post by DCish on Feb 21, 2015 11:25:04 GMT -8
Morti, what sort of analyzer are you using? Happy with it?
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