Use larger feed chamber (for logs), but small riser?

[joseph]

I have read that the cross sectional area should be constant thru the system.  I am using a 6 inch round (area of 29.5 sq inch) insulated riser, and the feed chamber is rectangular of 4.5 x 6.25 inch (area of
28.1 sq inch). 


I am testing up to the riser only - no barrel.
 
If I put kindling type of material into the chamber, the stove works like a rocket. However, if I put a larger chunk of wood, like a 3 inch limb (dry), it slows down considerably.  Obviously, if I was to split it into kindling size sticks, it would work.

But I'd rather not split pieces that small. 
 
I can't add more than one large chunk, because the feed chamber is small. I think that if I used a larger feed chamber, with perhaps 2 more large pieces, it would work similar to the original chamber with the kindling-size wood. 


If I was to fill the larger feed chamber with kindling-size wood, then of course it would overload the 6 inch back end. But I think that, since the larger wood does not burn as readilly as the kindling-size wood, a large chamber with large chunks would not overload it.

Thoughts?

[satamax]

Huh, you know that you are in horizontal batch rocket land, don't you?

[joseph]

Nov 9, 2013 21:23:58 GMT -8 satamax said:

Huh, you know that you are in horizontal batch rocket land, don't you?

No, I am not trying to do that type of system.  The horizontal batch system burns a lot of wood all at once.  I am trying to burn a little bit continuously, just burning the bottoms of the vertical sticks.  I just want to use bigger sticks.

Also, they are "tree wood", not "house builder's lumber" as I see in some demonstrations.

The problem is that a big (3 inch diameter) piece of wood won't burn by itself, because the body of the wood absorbs the heat and doesn't allow pyrolysis to occur.  Now, if there were a few logs together, they will generate enough heat to sustain a burn. 


Since I only want the bottom ends of the vertical logs to burn, that means I need a larger feed chamber.  For example, twice the cross sectional area. Since there will only be a few flames, compared to if I was burning small sticks (kindling), I should be able to use the same size riser with the larger feed chamber. 


Does this help clarify what I want to do?

[satamax]

Joseph, you're asking too much

Well, you can burn big wood, if you have enough mass around the end of the feed tube, and the begining of the burn tunnel. If it's realy well insulated, and realy hot by the time you put big wood in there. Making the feed tube larger will most certainly prove to have flame creep and smokeback. You might manage to make it 20% larger, i don't think you could manage more. One thing which is possible, is to have a door at the end of a bigger feed tube, with an air slot and a P channel slot. But why go the extra hassle, when a batch rocket is soo simple to make.

[grizbach]

Joseph, As you know tree wood is much less likely to smoke back. Even so, doubling the feed chamber will probably smoke back. If you want more heat from a J rocket, go to a larger system size.

I ran a J rocket for a few years, you have to babysit it.
As Max has stated above, these batchboxes are still easy to make. They are more reliable and put out a lot more heat.
I feel it has made the J rocket obsolete.

[satamax]

Nov 10, 2013 9:07:54 GMT -8 grizbach said:

Joseph, As you know tree wood is much less likely to smoke back. Even so, doubling the feed chamber will probably smoke back. If you want more heat from a J rocket, go to a larger system size.

I ran a J rocket for a few years, you have to babysit it.
As Max has stated above, these batchboxes are still easy to make. They are more reliable and put out a lot more heat.

I feel it has made the J rocket obsolete.

Exept smokewise. They smoke more than J tubes imho.

[joseph]

Nov 10, 2013 9:07:54 GMT -8 grizbach said:

...

I ran a J rocket for a few years, you have to babysit it.
As Max has stated above, these batchboxes are still easy to make. They are more reliable and put out a lot more heat.
I feel it has made the J rocket obsolete.

What I want is a slow, steady source of heat with a continuous small fire.  Something like the Clarry pellet camp stove ( www.clarrypelletstove.com ) is an example, except:

• I don't want to burn pellets
• I don't need it to be portable
  

Note how the Clarry works: You fill up the hopper with pellets, light the stove, and it self feeds for 8 hours without electricity.  It burns the pellets at a steady rate, and puts out a steady source of heat.

A "J" rocket stove with small sticks inserted vertically will self feed. But not for 8 hours.

The batchboxes put out more heat, but:

• I do not want a thermal mass
• I want a steady flame, without babysitting

Suggestions?

[satamax]

Yep, rockets aren't for you, turn to gasifiers.

You may be could get away with a long vertical feed closed at the top, and a L shape rocket. But i'm yet to see that work.

[Rinchen]

You are putting out some interesting design criteria :-)

I think it will be very hard to build something that can burn cordwood for a period of 8 hours without attending to it.
Perhaps something like a TLUD can work, but you will have to do your own experimentations in order to make a TLUD for cordwood.

www.drtlud.com/resources/

[joseph]

Nov 10, 2013 23:20:16 GMT -8 satamax said:

Yep, rockets aren't for you, turn to gasifiers.

You may be could get away with a long vertical feed closed at the top, and a L shape rocket. But i'm yet to see that work.

Well, the rocket is a gasifier; just not the conventional design.  Do you know of any gasifiers that do what I am looking for?

As for the long closed vertical feed, that was my first thought, but not any more.

[joseph]

Nov 11, 2013 5:18:11 GMT -8 Rinchen said:

You are putting out some interesting design criteria :-)

I think it will be very hard to build something that can burn cordwood for a period of 8 hours without attending to it....

If you allow for a forced draft (electric fan), I am pretty sure it could be done in such a way that only the ends of the logs are kept burning, and it will burn logs for over 8 hours. I am not talking about smoldering, I mean efficient, controlled burning.

It may even be possible without the fan; that would be even better, but would of course be more difficult to design and probably more difficult to make.
 

[satamax]

Joseph, a rocket stove is not a gasifier. Like all wood fire, there's a bit of gasification hapening, but a gasifier has two separate stages, baking the wood, so there's gasification, and then burning the wood gas. Some if not most have a burning fire as well, onto which the wood gas is fed and burned, but they arent rockets and rockets are not gasifiers.

As Rinchen was saying look into TLUD.

As for what you want to do, we've all been through the quest of long burning, clean, with no mass, as little space used, as little wood too. But no one has found the solution. The best answer i can give you now, cos i've been through it. Is batch rocket with a bell, and a little mass.

[joseph]

Nov 11, 2013 15:42:08 GMT -8 satamax said:

....As Rinchen was saying look into TLUD.

The TLUD is for cooking. The fire only lasts for 15 minutes. Although it can use a variety of fuels, the fuel needs to be in small pieces, like wood chips.

As for what you want to do, we've all been through the quest of long
burning, clean, with no mass, as little space used, as little wood too.
But no one has found the solution. ...

Have you tried using a fan to enhance the draft?

[Donkey]

Bigger feeds with J-tube rocket stoves haven't been found (as of yet) to do well, batch-box heaters overcome this short-coming.. BOTH need to burn hot and fast for clean combustion.. In fact, rocket stove design ITSELF is about hot, fast fires for clean combustion.
The solution to the "too much heat too fast" problem (so far) has been MASS.

For some reason, you don't want the mass... So, maybe a smaller stove with a continuous feed, like the rocket pellet stove on this thread.
But you want to feed it large cord-wood...

Tall order, each stove you might choose has it's own parameters for proper use. The way I see it, you now have a choice:
(1 live within the KNOWN parameters of (one of) each of these designs
(2 Choose a different kind of stove (not a rocket) and live within it's parameters
(3 Build something entirely new, perhaps based on rocket stove design and set NEW parameters (that will then have to be lived with)

[satamax]

Nov 11, 2013 17:40:15 GMT -8 joseph said:

Nov 11, 2013 15:42:08 GMT -8 satamax said:

....As Rinchen was saying look into TLUD.

The TLUD is for cooking. The fire only lasts for 15 minutes.
Although it can use a variety of fuels, the fuel needs to be in small pieces, like wood chips.

As for what you want to do, we've all been through the quest of long
burning, clean, with no mass, as little space used, as little wood too.
But no one has found the solution. ...

Have you tried using a fan to enhance the draft?

Joseph, you'd better do some further research on the net.

en.wikipedia.org/wiki/Top-lit_updraft_gasifier

I have used fans, not to make the fire last, but to prime it, and to help with smokeback. And so far it hasn't helped with the fire lasting.

May be a batch with the logs falling down like a gun magazine could do something good.

Have you built yourself any complete rocket? Insulated it properly?