[Stoves] The upside of Down feed

[Alex English]

   Did the pellets fall into the pipe with no form of grate of any kind?

I tried both with and without a grate,  and both worked. I don't have a 
good view of the bed dynamics. Perhaps I'll install a window.


  Just fell into the pipe and the air blasts them along as they burn?

Pretty much.

What is the chimney height?

Between 5-6 meters.

  What is the temperature at the top and bottom (I want to work out the 
draft in Pascals).

Out side ambient -10C
Just above the stove 150C.
Exit of  Insulated Chimney Unknown.

I see a strange bucket thing on the left. What is it?

If that pipe was open some hot char could fall back through it when I 
removed it.  And if I needed to douse it with water it would run in to it.

The other shows it operating  with a burner that has a small unsealed

> hopper for pellets.
>
> I presume they fed unassisted.
Yes.
>> I use a loose lid/follower to ride down on the pellets.
> Was that to limit the air flow or more to make it feed well?
If there was any chance of gasses convecting up the space the lid 
follower would create bit of a choke point  around the edge where the 
air would be uniformly moving down.
The hopper gets hot and could otherwise generate some convecting fumes . 
My current thinking is that the straight portion of the hopper should be 
double walled. The inner cylinder would not be thermally connected to 
the  outer. The inner should have a lid. The air should flow down around 
the out side of the inner cylinder and then through a fairly constant 
depth of pellets so as the maintain a constant pressure drop and hopper 
temperature regime.
>
>> So far there has been no fumes coming up and out, and the fire has not
> chased the air and fuel back into the hopper.
>
> Critical point. The reasons is I believe, what Dr Tom said to many times:
> superficial velocity, perhaps in this case just straight velocity. If the
> air passing through the fuel is going fast enough there is not chance the
> heat can start pyrolysing the pellets in the hopper.
>
> So my statement about fire following air (i.e. the flames progress toward
> the air supply) has to be qualified with a condition that 'below a certain
> air velocity'. That may or may not have to do with the superficial velocity
> or that plus a figure for the way the fuel pyrolyses. Coal, charcoal and
> wood will have different values.
Yes
>
>> The bottom throat on the hopper is about 5 cm diameter. It operates
> continuously at one speed with an input of 1.6 kg of wood pellet per hour.
>
> That burn rate is perfect for some small homes. It really bears looking at
> closely to see if a bolt-on burner can be fitted into some stoves - I am
> thinking of a goat dung burner (natural biomass pellets).
>
> The difference between this and a downdraft burner is that the fire is not
> at the bottom of the hopper, it is in the tube so technically it is a
> hopper-fed cross-draft fire.
It can be that or a combination with some air from every where.  Nothing 
about the burning bed part of this is settled.
>   Seems to me it would work well with corn as a
> fuel if you don't get a glass build up.
>
> Do those corn stoves have a wiggling wire worm because of ash issues? Or
> just or move the fuel?
I think its the ash issue.

What temperatures do you see in the coal hoppers?
>
> Regards
> Crispin
>
>
>
>
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