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Post by peterberg on Sept 12, 2018 1:40:32 GMT -8
From top to bottom: the red line represents the efficiency in percentages of Lower Heating Value.
The green line represents the oxygen (O²) left in the exhaust gases in percentages. Normal level anywhere on earth is 21%.
The blue line represents the temperature of the exhaust gases, in degrees Celsius.
The purple line shows the level of carbon monoxide (CO) in the exhaust gases in parts per million.
Does this answer your question?
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Reba
New Member
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Post by Reba on Sept 12, 2018 9:52:39 GMT -8
Yes thanks a lot
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Post by Jura on Sept 12, 2018 12:30:51 GMT -8
The Russian engineer Kolevatov proposed a riser with a variable diameter. The main idea was the flow turbulence. He described it in the book " The Stoves of the New Generation" I tried to register and download the file but the domain of my email is restricted. A smogli by vy zagruzit etu knigu na kakoy to drugoi filoobmennik, pozhauysta? |
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serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
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Post by serg247 on Sept 12, 2018 19:33:59 GMT -8
From top to bottom: the red line represents the efficiency in percentages of Lower Heating Value. The green line represents the oxygen (O²) left in the exhaust gases in percentages. Normal level anywhere on earth is 21%. The blue line represents the temperature of the exhaust gases, in degrees Celsius. The purple line shows the level of carbon monoxide (CO) in the exhaust gases in parts per million. Does this answer your question? Peter. Reba asked in what place is worth the sensor temperature Testo. |
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furno
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Post by furno on Sept 12, 2018 23:02:42 GMT -8
The Russian engineer Kolevatov proposed a riser with a variable diameter. The main idea was the flow turbulence. He described it in the book " The Stoves of the New Generation" I tried to register and download the file but the domain of my email is restricted. A smogli by vy zagruzit etu knigu na kakoy to drugoi filoobmennik, pozhauysta? Try this link www.furno.ru/files/kolevatov.rar |
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Post by peterberg on Sept 12, 2018 23:42:49 GMT -8
Peter. Reba asked in what place is worth the sensor temperature Testo. Sorry, I got it wrong then. The sensor probe is inserted in the start of the chimney stack, about 30 cm (1') from the floor. All figures are measured from there. |
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Ralf
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Post by Ralf on Sept 14, 2018 1:36:57 GMT -8
Peter,
I´m trying to wrap my head around the flue gas diagrams you provided. It seems that the initial short peaking of the CO that I saw in most "standard" Batchbox analyses is gone, however the overall CO during the full burn seems quite a bit higher than in the "standard" design.
Apart from the hard physical numbers you also got the impression that the heat output is bigger compared to a standard BB system of the same size right ?
I also wonder if the taper riser system will perform even better if scaled up (150 /180 /200 mm), a tendency that I also see in the diagrams of the standard design.
However if the capped-funnel-riser gets larger its use might be limited to wider bell shapes because of potential downflow restrictions...
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Post by peterberg on Sept 15, 2018 1:01:36 GMT -8
Peter, I´m trying to wrap my head around the flue gas diagrams you provided. It seems that the initial short peaking of the CO that I saw in most "standard" Batchbox analyses is gone, however the overall CO during the full burn seems quite a bit higher than in the "standard" design. It's a bit different. In about half of the test runs the start CO peak is absent, the other half it's there. There seems to be a sort of trade-off, no peak at the start means higher during the burn and in some cases also a higher end peak. No two runs are the same, configuration-wise, I tried to find the best one. The runs with the peak seems to be more stable overall. I did some 12 test runs since the last time I posted a diagram. None of those touched the CO bottom line although it's common in a wel-operated core. And since my Testo 330 is 6 months overdue for calibration I posted it as a package to the Dutch reprensatives of the Testo firm. Starting afresh in two weeks time. Apart from the hard physical numbers you also got the impression that the heat output is bigger compared to a standard BB system of the same size right? I intend to build a straight riser on top of the same core and in the same barrel bell enclosure so I can have an idea whether it's actually different from the tapered one or not. And yes, I'd get the impression that the thing is more powerful although this should be tested first before something definite can be said about it. I also wonder if the taper riser system will perform even better if scaled up (150 /180 /200 mm), a tendency that I also see in the diagrams of the standard design. However if the capped-funnel-riser gets larger its use might be limited to wider bell shapes because of potential downflow restrictions... You are right, the scaled-up versions are easier to get right. Those versions need a larger bell anyway, the heat extraction surface scales up the same rate as the core. So I don't think it would be problem unless one would house a large core in a cramped bell enclosure. Keep in mind the tapered riser as in the pictures is't any wider than the firebox itself. |
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Ralf
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Post by Ralf on Sept 15, 2018 1:55:39 GMT -8
Thanks very much for your answer, I get a much better picture now!
At the moment I consider a slightly tapered riser for my next build, since the bell won´t be that high and I can put the BBox a little higher that way for loading comfort. For my 18 cm system I arrive at the needed riser volume when I put a 50 cm piece tapering from 18 cm to 30 cm (calculated with a truncated cone shape) on top of a 30 cm high straight port/rams horn section.
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Post by peterberg on Sept 15, 2018 2:05:22 GMT -8
Of course you are free to build anything you like. But I can't guarantee it would be doing what you might expect of it. At this time, it looks like it's an alternative. The experiences from guys like you could give us some much needed information.
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Post by travis on Sept 16, 2018 23:54:15 GMT -8
Great tests Peter. Doing the side of things i just dont have the equipment for!
In terms of cutting I did very minimal cutting on my whole building, most of it was actually for the bell rather than the riser. Once you have a good brick base you can do a basic sun wheel technique with bricks slowly stepping out with each course. Cob or mortar is your friend, I use lots!
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Post by ronyon on Sept 23, 2018 13:40:48 GMT -8
Pardon me if I missed it, but do we know what is happening at the constriction?
Are we thinking that the gasses are reburning at this point?
The csa only returns to normal, right, it's not constricted down to a port, correct?
Is the idea that the capped funnel slows the gasses, giving more time for mixing?
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Post by peterberg on Sept 24, 2018 1:25:55 GMT -8
Pardon me if I missed it, but do we know what is happening at the constriction? No, we don't as yet. Are we thinking that the gasses are reburning at this point? Ninety-nine percent of the time when flames come out of the riser the burn is getting dirtier. I'd think it isn't any different this time. I would like to keep the flames inside the riser, since it's acting as a wood gas combustion chamber. The csa only returns to normal, right, it's not constricted down to a port, correct? Yes, for the moment. The square opening at the top is exactly the same as the bottom of the riser, csa-wise. I'd run the thing a number of times with a restriction, bringing it down to the same csa as it would be like a round riser of the same size. Because of changing other values at the same time I don't know whether this helps or not. Is the idea that the capped funnel slows the gasses, giving more time for mixing? That's the idea, it's extending the dwell time as in a much longer but straight riser. And as Satamax suggested, maybe it also poses some back pressure. Not for sure, this is all guesswork. Doing development the empirical way and try to understand what happened afterwards. The disadvantage of not having done a physics study, aerodynamics to name one. |
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Ralf
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Post by Ralf on Sept 25, 2018 12:25:20 GMT -8
I see a little difference between this setup and travis' one that might be of interest.
He shaped the opening at the top of the tapered riser more like a slit/port and not as a square hole
and has only 140 mms top gap above that with a system size of 150 mm.
Could it be that this confined space above the heat riser acts a little like the shoe box,
providing futher mixing and combusting the rest of the 500 ppm CO ;-) ?
Would be an easy thing to make a U-shape out of ceramic fibre board and put it upside down on top of a second "port" at the top of a tapered geat riser.
Unfortunately I don´t have a ready batch box with tapered riser at hand (will come), I´d try it immediately.
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Post by peterberg on Sept 25, 2018 23:03:39 GMT -8
You'll do what you need to do. But in my experience every time the flames rise above the riser the CO is going through the roof. So better combustion out of the confinement of the riser doesn't look viable to me. And secondly, I've run the experiment also with a slit of 120x90 mm instead of a 120x120 mm opening. No decernable difference but at the same time I changed other aspects of the configuration, to be honest.
My Testo analizer is up for calibration at the moment. My intention is to make a list as I often do and work my way down as soon as the thing has been returned. I've got whole winter to work this out properly. Don't expect miracles of it, I know how wide-ranged and inconsequently results can be.
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