[Stoves] Fwd: Fwd: Re: Heat / cook stove - proposed design

Tom Miles Easystreet tmiles at trmiles.com
Fri Nov 25 09:34:09 CST 2011 

Darren

Just send me the photo and I'll post it. 

Tom Miles
Stovess List Owner


T R Miles Technical Consultants Inc. 
tmiles at trmiles.com
Sent from mobile. 

On Nov 25, 2011, at 5:26 AM, Darren <mail at vegburner.co.uk> wrote:

> Resent a third time with the photograph attachments stripped (suspecting that the combined size of attachments may be stopping it getting through - apologies if you get this three times!!)
> 
> -------- Original Message --------
> Subject:	Fwd: Re: [Stoves] Heat / cook stove - proposed design
> Date:	Fri, 25 Nov 2011 13:18:38 +0000
> From:	Darren <mail at vegburner.co.uk>
> To:	stoves at lists.bioenergylists.org
> 
> Resent as it didn't appear to get to the list (apologies if this comes through twice)
> 
> -------- Original Message --------
> Subject:	Re: [Stoves] Heat / cook stove - proposed design
> Date:	Fri, 25 Nov 2011 02:52:47 +0000
> From:	Darren <mail at vegburner.co.uk>
> To:	Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
> 
> Getting close to completing this stove now.
> 
> Some photos are attached.
> 
> I've also attached a drawing of how things stand now (not to scale)
> 
> The door and hatch are made and have fire rope seals.  These will be fitted once everything else is together.
> 
> I've used a cast iron grate from an old coal stove that was the perfect size.
> 
> A couple of things I'm wondering
> 
> *At the moment all the secondary air is going in through some square section pipe with an internal diameter of 20x20mm that enters at the rear of the combustion chamber above the ceramic blocks.  (shown as blue square in stove2-7.jpg).  Is this going to supply enough air or should I put a similar sized secondary air inlet on the front of the stove also?
> 
> *Crispins GIZ design has an area where the combustion chamber tapers     wider (an expansion chamber?).  I've drawn this in green in stove2-7.jpg . How important is this?  I could make these sloping walls from sheet steel or I guess buy some refractory material sheets (my x partner who is making this with me had some jewellers heat mats that would appear suitable although she appeared reluctant to give them up)   Is this a crucial detail?  What effect does it have on combustion? what would happen if I leave them out?
> 
> Thanks in advance for any pointers.  Hopefully I should finish and test fire it in the coming week.
> 
> Best
> 
> Darren
> 
> 
> 
> 
> 
> On 06/11/2011 22:33, Darren Hill wrote:
>> 
>> Hello Everyone, 
>> 
>> After this project going well onto the back burner as it warmed up here, the temperature we are seeing at night now is focusing my attention again. 
>> 
>> If anyone is interested discussion about this started 29th December and went on until 23rd February.  The stove is about half built- I'm going to be working on it again on Tuesday. 
>> 
>> I've attached a diagram of how I'm now planning to build the grate and throat area.  (I took the liberty of modifying the GIZ diagram Crispin kindly sent to explain an appropriate layout) 
>> 
>> As I'm only going to be burning wood and in my experience of wood stoves all the wood burns to a light ash which would easily fall through the grate I am planning to have a stationary grate.   Am I making the wrong decision here? 
>> 
>> I'd welcome anybodies thoughts on things as they stand. 
>> 
>> Hoping to get it finished soon.  Considering the number of people I've been describing it to all year it would be good to also let them know how it works!!!  I've never seen anything like this in action - I'm thoroughly intrigued. 
>> 
>> Best regards 
>> 
>> Darren 
>> 
>> ------------------------------------------------ 
>> 
>> 
>> [Stoves] Building my Heat / cook stove. 
>> Crispin Pemberton-Pigott crispinpigott at gmail.com 
>> Wed Feb 23 21:46:01 PST 2011 
>> 
>> 
>> Dear Darren 
>> 
>> 
>> 
>> I think you are going to have a couple of problems with the layout as drawn 
>> and they are solvable. 
>> 
>> 
>> 
>> Let's look at them all: 
>> 
>> 
>> 
>> 1.       The restricted height at the entrance of the combustion area is 
>> probably the right height, but that is for limiting the amount of fuel that 
>> can fall onto the grate further in. 
>> 
>> 2.       The grate needs to extend into the whole area under the combustion 
>> zone or else it will fill up with ash and you don't have a way to get it 
>> out. The grate is correctly placed, perhaps a little steep but that can be 
>> altered. Char and ash will fall forward (as it should) but end up in the 
>> bottom of the combustion area. 
>> 
>> 3.       The constriction you describe well on the side is going to catch 
>> some of the char and ash and might (or not) create a bridging problem. You 
>> can address that if it happens. 
>> 
>> 4.       The purpose of getting the grate under all the horizontal area 
>> solves two things: it allows a lot of controllable air to reach the far end 
>> of the grate where there will always be less fuel. That means air gets 
>> through and effectively becomes secondary air. If you make the grate 
>> shakeable, you can clear the ash but you will need to have it stop at a 
>> vertical or inclined surface or the bottom will get blocked. 
>> 
>> 5.       We are having pretty much the same layout but the restriction is 
>> above the grate about 100mm. This allows the grate to carry enough fuel and 
>> still have all the gases and smoke and flames come together above the fuel. 
>> 
>> 6.       We start the fire by placing some fuel on the grate, extending into 
>> the part below the combustion area then top-light in the combustion area. 
>> The fire works its way back to the fuel hopper it the top is left open. Then 
>> when it is well established, close the hopper and vary the air with the 
>> controller you indicated. 
>> 
>> 7.       The key change is the extension of the grate, perhaps at a lower 
>> angle. We are using 15-20 degrees but there is nothing magic in that. 
>> 
>> 8.       I have attached a drawing of the GIZ 7.1 combustion chamber that 
>> worked very well using all the principles mentioned. Note the angled piece 
>> on the right. This protects the grate from becoming blocked from movement by 
>> trapping something between it and the wall, when shaken. 
>> 
>> 9.       Note the constriction above the left side of the grate. It is 100 x 
>> 80mm. As you look at the side view drawing, the grate is 155 deep. That 
>> means the moving part is about 260 x 155. 
>> 
>> 
>> 
>> Regards 
>> 
>> Crispin 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> From: stoves-bounces at lists.bioenergylists.org 
>> [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Darren Hill 
>> Sent: 21 February 2011 20:40 
>> To: Discussion of biomass cooking stoves 
>> Subject: Re: [Stoves] Building my Heat / cook stove. 
>> 
>> 
>> 
>> Hello Crispin, 
>> 
>> The bleed is at top bypassing the need for gases to go down past the heat 
>> exchanger. 
>> 
>> Secondary air is flowing in through some 20mm x 20mm internal diameter 
>> square section tubing.  Is this enough or do I need more? Another 20mm x 
>> 20mm square section tube? More? 
>> 
>> I've attached another diagram which shows things as they are currently 
>> planned/progressing. 
>> 
>> Looking at this diagram.  Are you saying to have some of the grate to the 
>> left of the red line I've drawn on the diagram? 
>> 
>> Currently this is the thinnest point (or bottle neck, or throat) and has a 
>> vertical ceramic slab either side so that this 'throat' is not the full 
>> width of the hopper.  Extending the grate further to the left will, in 
>> effect, increase the area of the thinnest point.  I currently plan to have 
>> the lowest part of the grate level with the bottom of the ceramic block 
>> (that is the floor of the combustion chamber) so it is away from the 
>> thinnest/hottest area. 
>> 
>> Is it best to shift the grate to the left? 
>> If so what % of the grate left of the red line? 
>> Should I also raise the grate so that the its level with the top of the 
>> ceramic block that is the floor of the combustion chamber? 
>> 
>> I'm working on the stove today and tomorrow.  Going to build the air tight 
>> doors today. 
>> 
>> Best 
>> 
>> Darren 
>> 
>> 
>> 
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> <stove2-7.jpg>
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