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Post by josephcrawley on Feb 13, 2022 14:27:39 GMT -8
Is it reasonable to assume that the published dimensions for the batch rocket core would be a good starting point for alternative core development?
By this I mean the ratios of primary/secondary air to box volume and port sizes? Also the general heat output.
thanks
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Post by peterberg on Feb 14, 2022 1:29:10 GMT -8
It would be a good starting point, yes. Although the DSR1 and DSR3 forms a category of its own. That is, the port size and primary/secondary ratios are different. And most important: the port is in the ceiling.
In general: as long as the port is in a vertical wall all ratios are applicable. This remains true even with doors at two ends of the firebox and the port centered in one of the sidewalls, as Adiel showed some time ago. General heat output is firmly related to the weight of the fuel that's being combusted. Since combustion is close to complete most of the time, heat output is quite a given.
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Post by skywalker on Feb 14, 2022 13:12:34 GMT -8
It would be a good starting point, yes. Although the DSR1 and DSR3 forms a category of its own. That is, the port size and primary/secondary ratios are different. And most important: the port is in the ceiling. In general: as long as the port is in a vertical wall all ratios are applicable. This remains true even with doors at two ends of the firebox and the port centered in one of the sidewalls, as Adiel showed some time ago. General heat output is firmly related to the weight of the fuel that's being combusted. Since combustion is close to complete most of the time, heat output is quite a given. Hi Peter you have a link to this double door sidewinder? Curious to see.
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Post by peterberg on Feb 14, 2022 13:59:56 GMT -8
The rough prototype
and the final design.
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Post by skywalker on Feb 16, 2022 8:38:14 GMT -8
The rough prototype and the final design. Thanks a lot! Very cool rocketstove.
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Post by josephcrawley on Feb 16, 2022 12:45:04 GMT -8
Peter could you explain the differences in function between the DSR iterations and earlier riser based cores?
I have followed both development thread dsr 2 and 3 but there are many twist and turns. Particularly the idea of the top box and increasing dwell time vs the the wide open heat riser. Also could you explain how the dsr3 functions without secondary air and why the port needed to change when moved to the ceiling.
Perhaps you have already written this up for batchrocket.eu and it just hasn't been translated to English yet.
Thanks
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Post by peterberg on Feb 17, 2022 7:42:16 GMT -8
Peter could you explain the differences in function between the DSR iterations and earlier riser based cores? Ooww... This is a hard question to answer, since I ain't sure about how the earlier versions work exactly. But I'll give it a shot, maybe more knowledgable people's opinion could differ. During development in 2012 the proportions of the riser based batchrocket were established. The port could be narrower, even down to 50% of round riser csa. But by using that, the thing became unstable much earlier caused by a fuel overload. So at some point I settled down on 70% plus or minus a few percent. At the time of experimenting with the DSR1 and the ceiling port I came to the conclusion a shorter and narrower port would work best overall. That came down to 50% while I was fiddling with it outside in the garden. By the time I scaled it down a bit to fit into two barrels in the workshop it turned out to be a very uncontrollable combustion core. In the sense that although it showed the tendency to burn surprisingly clean in a very early stage but jumping into overfuel mode whatever I tried. Of course I tried it with a larger port and several end port sizes but to no avail. So at some point I ditched further development as being too troublesome. The DSR2 is actually the same as the riser incarnation as far as the proportions of the firebox, port and riser goes. As you know, the riser isn't any higher than the firebox, followed by a wider horizontal tunnel. So it was a different implementation of the vertical port-in-wall principle. There's a lot of experience with this principle, but it proved to be quite difficult to coach it into good behaviour. The double vortex was still formed in the riser stub and in the horizontal tunnel a sort of "fire fountain" appeared, almost every single burn. Only when the flames were extending all the way in the end port overfuel could occur although not as standard. So this core was declared as being usable in the proportions as recommended. Both the riser and DSR2 cores work in roughly the same way. Even a riser core can be modified with a shorter and funnel shaped riser as long as the same internal volume was maintained. After a year of development off and on, the DSR3 turned out to be quite another animal at the final stage. The proportion of the port did go down to 50% again, width/length ratio 1 to 4. Running it endlessly in different guises, it developed a tendency to thermal overdrive like the DSR1 did. In the sense it raced through the fuel, at ever increasing pace until it was all gone. As soon as the horizontal tube and the space around it was full of fire it showed a dirty burn as well. Conclusion up to that point: flames coming out of the end port had to be avoided. No news here, even in 2012/2013 several people drew the same conclusion, flames out of the riser were a no-no. This little core is behaving itself admirably now, and one could wonder why, nothing special to be seen at first glance. But there is, warming-up phase is relatively long but the double vortex in the tube tend to stay at the sorrounding of the port, i.e. the rear half seen from the front. My reasoning about this effect is the following: the tube is more or less the same as system size. The hot gases are going through a 180 degrees turn while streaming to the end port and at the same time expanding quite a lot. Caused by the space around the tube being 1.5 times larger than the tube itself. All those expanding gases need to exit through the end port, which is a long and narrow opening as large as system size again. At present, it looks like the expanded gases having trouble to escape through the end port with ease. During demonstrations performed in the last 6 months or so, it seems obvious that the core is slowing down itself quite calmly while on the top of the burn. Even after doing a refill using two biggest logs it could hold side by side it stayed in the same mode. And burning sqeaky clean, I proudly have to add. I have followed both development thread dsr 2 and 3 but there are many twist and turns. Particularly the idea of the top box and increasing dwell time vs the the wide open heat riser. Also could you explain how the dsr3 functions without secondary air and why the port needed to change when moved to the ceiling. The port size is changed due to experiments, this turned out to be the best so far. This core functions without secondary air provision at all or so it looks like it. What happens in reality is this: during startup the door is kept open a crack so more air is coming in low, helping the fire to develop. As soon as the double vortex is firmly established in the tube the door is closed, in steps if required. All air is fed through the door frame, nothing in the lower half of the firebox. A lot of that air is coming in through the top beam of the door frame, while being heated by that frame. Colder air falls down from the sides along the glass and feed the fire, hottest air coming in through the top beam. All that hot air stays at the top and most of it streams to the port. While the combustion process is at its top it is clearly visable that the vortex is "clinging" at the rear wall in the tube. So there is secondary air, although fed in the firebox in an entirely different manner. Reading all this, I need to stress a space of about two inches should be free between fuel and the ceiling of the firebox. The firebox of the (hopefully) final design stage is wider and lower, to facilitate a fire that's close to the ceiling port. And to conclude: even the now-standard core will function without a door, similar to the DSR2. And this small DSR3 core is doing more or less the same, it is able to run with a spark screen only while the CO dips to values as low as 200 ppm. Viewed as such, a door tend to make the batchrocket more complicated. But people want to have doors to protect their home from flying sparks and falling embers on the carpet. The final core is ready, the body of the heater will hopefully be here coming Saturday. Next week will be quite eventful, trying to marry the core with the body, connecting it to the chimney and firing it up! I'll report back with comments and pictures in the development thread.
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Post by josephcrawley on Feb 18, 2022 15:30:04 GMT -8
Thank you for this thorough explanation!
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Post by josephcrawley on Feb 20, 2022 16:19:23 GMT -8
This is presumptuous on my part but I have a few feature requests based on customer feedback and my own observations in building your designs over the last few years.
If possible it would be nice to separate the air input from the door of the stove. I think this would make the design more accessible as it could eliminate the need for welding to construct a stove.
The port in future development be in the ceiling like the dsr3. I live in a fickle climate where stoves are frequently not fired on a daily basis through the heating season. The dead cold stoves have a slow and potentially smokey start up with the port located in the wall. In the case that the startup is botched with a poor start the amount of smoke in the house has lead to complaints.
If possible use only readily available materials in construction.
Eliminate consumable metal air delivery from inside the firebox. Hopefully all air could be delivered using channels behind the brick with cut in openings to deliver air where needed.
An ash catchment with an external way to dump the firebox into a pan. A lower door could double as the source for air channeled up to the firebox.
I hope that my requests are not seen in a negative spirit. I greatly appreciate the effort and creativity you have put into the development of these stove cores over the last ten plus years.
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Post by peterberg on Feb 21, 2022 11:53:51 GMT -8
If possible it would be nice to separate the air input from the door of the stove. I think this would make the design more accessible as it could eliminate the need for welding to construct a stove. In my view, it's already possible to separate the air inlet from the door. All the doors I used were DIY projects and it seemed sensible to have the air inlet integrated. But this isn't mandatory, the larger versions could well be served with a bought door and the air inlet below it. The port in future development be in the ceiling like the dsr3. I live in a fickle climate where stoves are frequently not fired on a daily basis through the heating season. The dead cold stoves have a slow and potentially smokey start up with the port located in the wall. In the case that the startup is botched with a poor start the amount of smoke in the house has lead to complaints. The DSR3 is particular finicky to build, the proportions are even more strict in that design. The final reference design isn't ready yet, but I'd expect test results in about a fortnight. Don't hold your breath though. If possible use only readily available materials in construction. Good point, the evolution of the design isn't pointing in that direction, regrettably. Eliminate consumable metal air delivery from inside the firebox. Hopefully all air could be delivered using channels behind the brick with cut in openings to deliver air where needed. The DSR3 works well without a separate secondary air channel, all air is delivered through the door frame. This could be a separate frame with a standard door mounted in front. It requires metal work again, sorry. An ash catchment with an external way to dump the firebox into a pan. A lower door could double as the source for air channeled up to the firebox. Can be done yes, that would mean a second door. No air should be delivered through the ash door through a grate by the way, the system will run very dirty like that. I hope that my requests are not seen in a negative spirit. I greatly appreciate the effort and creativity you have put into the development of these stove cores over the last ten plus years. Thank you, nice compliment. At the moment there aren't any other projects in the pipeline. And of course there isn't such a thing as a stove that is satifying for all and every customer. Regrettably, I might add.
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Post by josephcrawley on Feb 21, 2022 15:39:55 GMT -8
<a A version 8 sketchup of the concept drive.google.com/file/d/1Er4fIhqkbTUiEFb9dd8nA3oE3FjJi5JP/view?usp=sharingdon't look to hard, none of the dimensions are in anyway based on reality. Here's the idea for air delivery I've been kicking around inside my head. I believe the size of the side brick openings could be used to control the amount of air so the the lower door could be left ajar during operation. The door opening could be sized to fit smaller and larger doors in a brick veneer that faced the stove. I have not come up with an ash dump idea that I like yet, I'm picturing something with an off center pivot or weight so that it stays closed by its own weight with a front twist handle. This of course would involve welding! This masonry based air delivery concept may be something you've explored and rejected. It is highly likely the image will not be visible as google long ago turned their back on the "do no evil" mantra.
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Post by josephcrawley on Feb 22, 2022 12:04:07 GMT -8
I've updated the sketchup to show an ash dump/pan concept that I think could work. The pan relies on an over sized front face to block air to the ash dump in the rear of the firebox. This of course would leak a small amount of air but hopefully not a significant amount. At some point ash will make its way between the pan and the back wall causing a large air leak as the pan will no longer slide fully in. Hopefully the user would vacuum this area as needed. I put a face on the core to illustrate how a smaller or larger door could be fitted. I took a look at the DSR3 reference drawing and I'm unsure about replacing the tube with brick without a significant increase in size of the upper shoe box. drive.google.com/file/d/1yugDMzhJ7YG4s3T9JaPI-W4ahg7_oi_4/view?usp=sharingI'm posting a picture in case by some miracle it is viewable by others. Please excuse my running joints!
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Post by peterberg on Feb 23, 2022 0:58:09 GMT -8
I'm inclined to think it could work, it can be done this way. Keep in mind that the crux of the thing is the ability to employ a huge air intake, while the burn is controlled by the proportions of the top box and relative measurements. The inlet openings could be therefore much larger, those aren't necessary for controlling the burn. In the reference design the air inlet in the firebox is at the top half left and right, not just a small slot.
In the reference design the port is flush with the backwall of the firebox. The opening for the ash dump not at the back but one brick to the front instead will help to avoid ash falling behind the ash pan to some degree.
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