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Post by peterberg on Feb 21, 2015 12:26:12 GMT -8
The point of lowest pressure in the port is just at the corner, before getting wider into the riser. Theoretically that would be the best spot to insert the (pre-heated) air. But the experiments of Matt show it can be done in a number of ways, even at a distance upstream from the port. Although, closer to the point of lowest pressure a smaller duct would be sufficient. That last one is an educated guess, again.
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Post by matthewwalker on Feb 21, 2015 12:49:08 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 Well, it's a fun challenge to be sure. You've got leftover CO and plenty of O2, I would think it's just a mixing issue at this stage. That's what I believe the vertical delivery tube helps with, by spreading out the air on the injection it has a better chance of mixing completely before it's out of the combustion zone. Pure speculation, but that's what my experiments seem to point to. I could get real close with simple tubes like you have there, but the small refinements is what took it from 100ppm +/- to below 10ppm in regular use.
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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 22, 2015 14:31:48 GMT -8
@ DC Analyser is a TPI 716. It does what it says on the tin. It isn't loaded with features that a top end Testo has. The software is basic and I have to create the charts manually to resemble the ones Peter & Matt have but I like a challenge with Excel :-)
As you mentioned Matt, getting the right mix is the key. Reminds me of the manual 'analogue' chokes on cars before everything went electronic - you got to know how far to pull the lever when starting from cold & running rich and when it was okay to push it back in.
Had a play around last night with the tube inserted into the riser. The CO was high (between 2,000 & 6,000ppm) & efficiency at 93% (gr) until the fire warmed up. I kept the primary wide open otherwise the thing would stall. Once the embers had established and I refilled the firebox I shut the primary down to half closed. After a spike the CO dropped to between 60ppm and 50ppm with efficiency at 92% (gr).
Maybe I should be content with a 'smoky' start as the performance once it is up to temperature never ceases to amaze me.
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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 28, 2015 18:36:40 GMT -8
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Post by peterberg on Mar 1, 2015 0:42:17 GMT -8
I also noticed a slight drop in efficiency - is this a trade off for the lower CO readings?. No, I don't think so. The efficiency is calculated from the excess air and temperature. CO isn't involved in the formula. A slight rise of O2 will immediatly show in the efficiency figure. Maybe I mentioned this before: in terms of efficiency, you'll do much better when the O2 is going down as opposed to end temp. One percent less O2 has a far greater impact then just 10 degrees lower temperature. I'd say your excess air is quite high, is your door leaking or is the secondary pipe too wide? When this process is really running well the O2 could easily be as low as 8% without adverse effects.
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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 Mar 1, 2015 12:11:57 GMT -8
Thanks for this explanation Peter. I'll know what to look for now.
The tube feeding the secondary air isn't attached to the door so it isn't sealed to the outside like Matt's.
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Post by talltuk on Mar 3, 2015 14:40:24 GMT -8
Hey Andy, how are you finding the 716? Can you keep it running for an entire burn?
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stoker
Junior Member
Posts: 61
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Post by stoker on Mar 7, 2015 18:16:24 GMT -8
Another suggestion for the shape of the vertical pipe with the slot:
Make it a minimum-drag aerofoil shape with the slot in the trailing edge, pointing away from the door. (Try it with the top of the tube closed or open.)
For that you would want metal that's reasonably easy to bend. Copper plumbing-pipe?
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TomS
New Member
Posts: 8
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Post by TomS on Mar 7, 2015 19:48:13 GMT -8
This is a very intriguing thread! What are the thoughts of attaching a trip wire just forward of, and, along the vertical slot. One could use a coat hanger and just spot-weld in place so that if it doesn't work it can easily be ground off. That is a similar idea to the square tube that Peter suggested.
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Post by johndepew on Mar 21, 2015 16:42:20 GMT -8
So, after reading though this thread, I got to thinking, what if instead of brick or cast slope to the floor, maybe a guy could use some, say, 4" strap steel with 3x1/2"channel iron welded on the underside to make a tube with wings protruding on either side, cross-sectionally. One of these on either side of the batch box to create your sloping floor. Then figure out a way to introduce the air maybe 2 inches or so ahead of the back wall of the firebox, either with a converging "bridge" tube, and single central channel, like what you've been using, or simply 2 separate pipes at the center of the hypotenuse of the right triangle of side wall-rear wall...Does that make sense? I'm planning to try it as soon as I have time, can anyone tell me why it obviously wouldn't work? This is excellent work, Matt. Thanks for sharing so freely.
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Post by ericvw on Mar 21, 2015 16:54:59 GMT -8
johndepew, Are you aware of the famous Satamax response?.... "Metal is doomed!" Could always try it tho-Mite just warp a bit, that's all. Eric VW
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Post by ericvw on Mar 21, 2015 16:57:23 GMT -8
morticcio, You been messin around with Walker port? Have you had a chance to get started on the Italian job(for daughter)? Eric VW
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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 Mar 21, 2015 17:16:58 GMT -8
Only by sticking a 2" tube on the bottom of the firebox!
Going out next week so hope to start something. Need to check with local supplier if the firebricks are rated to 1260C. Most refractory products are easy to come by over there - especially the single wall flue. Will need to source some insulated firebricks and/or high temp insulation. Got some interest in the batch bell stoves locally as most houses have an open fire in the corner. These tend to use a lot of wood with most the heat going up the chimney.
However, I've got a point to point radio link for broadband to install, olive trees to prune and the plot to tidy up first though!
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Post by ericvw on Mar 21, 2015 17:20:58 GMT -8
I've got a point to point radio link for broadband to install Not trying to hijack this thread, but what do you mean? Eric VW
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Post by Daryl on Mar 21, 2015 17:40:25 GMT -8
So, after reading though this thread, I got to thinking, what if instead of brick or cast slope to the floor, maybe a guy could use some, say, 4" strap steel with 3x1/2"channel iron welded on the underside to make a tube with wings protruding on either side, cross-sectionally. One of these on either side of the batch box to create your sloping floor. Then figure out a way to introduce the air maybe 2 inches or so ahead of the back wall of the firebox, either with a converging "bridge" tube, and single central channel, like what you've been using, or simply 2 separate pipes at the center of the hypotenuse of the right triangle of side wall-rear wall...Does that make sense? I'm planning to try it as soon as I have time, can anyone tell me why it obviously wouldn't work? This is excellent work, Matt. Thanks for sharing so freely. One guy on here did something similar. Two separate tubes coming in on opposite sides of the port. It is on one of the threads around here. He doesn't post here any longer but the thread is still here.
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