Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes at
the base and a further 8 x 60mm holes further up. As an airflow specialist
in the design of car engine cylinder heads I know how fast enormous volumes
of air gets through very small holes with just the 15 psi of our planet's
atmospheric pressure pushing it.

It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it still
stumps me. Any comments?
--
Dave Baker

"Dave Baker" wrote in message ...

Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes at
the base and a further 8 x 60mm holes further up. As an airflow specialist
in the design of car engine cylinder heads I know how fast enormous volumes
of air gets through very small holes with just the 15 psi of our planet's
atmospheric pressure pushing it.

It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it still
stumps me. Any comments?
--


Well, given your ideas why not try it and see if your design works as
well/better/worse than the original

In message , Nthkentman
writes
"Dave Baker" wrote in message ...

Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes at
the base and a further 8 x 60mm holes further up. As an airflow specialist
in the design of car engine cylinder heads I know how fast enormous volumes
of air gets through very small holes with just the 15 psi of our planet's
atmospheric pressure pushing it.

It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it still
stumps me. Any comments?

I think that design was developed by students at Silsoe Agricultural
College. The original purpose was the disposal of plastic chemical
containers. This use is now banned:-)

Avoiding black smoke was probably part of the specification. Of course
you won't get 15psi pressure differential anyway. I can confirm that
they work but siting under or near overhanging trees is a huge
mistake:-)

--
Tim Lamb

On Friday, August 16, 2013 3:59:39 PM UTC+1, Dave Baker wrote:
Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes at
the base and a further 8 x 60mm holes further up. As an airflow specialist
in the design of car engine cylinder heads I know how fast enormous volumes
of air gets through very small holes with just the 15 psi of our planet's
atmospheric pressure pushing it.

It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it still
stumps me. Any comments?


I don't think you're allowing for just how small the pressure differential is likely to be - if we assume that the air inside the drum has expanded so much it has negligible mass the differential will be about that between the top and the bottom of the drum - somewhere around .03 psi (using a lot of handwaving, so I'd quite accept there may be a factor of 10 either way, but still pretty small).

On Fri, 16 Aug 2013 15:59:39 +0100, Dave Baker wrote:

What puzzles me is why it needs such large air holes. 11 x 50mm air
holes at the base and a further 8 x 60mm holes further up. As an airflow
specialist in the design of car engine cylinder heads I know how fast
enormous volumes of air gets through very small holes with just the 15
psi of our planet's atmospheric pressure pushing it.

Well the big difference is that the engine has a sealed piston
"pulling" the air in, thus in effect as the full 15 psi across the
opening. The incinerator is just using the convection from the fire,
it has pretty much 15 psi both sides of the opening.

--
Cheers
Dave.

On Fri, 16 Aug 2013 15:59:39 +0100, "Dave Baker" wrote:

Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes at
the base and a further 8 x 60mm holes further up. As an airflow specialist
in the design of car engine cylinder heads I know how fast enormous volumes
of air gets through very small holes with just the 15 psi of our planet's
atmospheric pressure pushing it.

It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it still
stumps me. Any comments?

Yes, you know nothing about airflow due to combustion

It's as near as dammit 15psi all round the combustion chanber. The only way to
get the air to move is to heat some of it and then replace that air and heat it
instantly and repeatedly. The differential pressure is very low. You *need*
big holes or some means of achieving a forced draught like a fan or a
compressor.


--

On Fri, 16 Aug 2013 18:01:57 +0100, The Other Mike
wrote:

You *need*
big holes or some means of achieving a forced draught like a fan or a
compressor.

Bingo. And I've found the best way to achieve quick, simple and easy
smokeless combustion of some very horrible stuff is a forced air
blower (like an old furnace fan or HVLP turbine - even a car blower)
feeding tangentially into the drum.
Using that, I can burn my waste and no bugger knows about it.

"The Other Mike" wrote in message
...
On Fri, 16 Aug 2013 15:59:39 +0100, "Dave Baker" wrote:

Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes
at
the base and a further 8 x 60mm holes further up. As an airflow specialist
in the design of car engine cylinder heads I know how fast enormous
volumes
of air gets through very small holes with just the 15 psi of our planet's
atmospheric pressure pushing it.

It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it
still
stumps me. Any comments?

Yes, you know nothing about airflow due to combustion

It's as near as dammit 15psi all round the combustion chanber. The only
way to
get the air to move is to heat some of it and then replace that air and
heat it
instantly and repeatedly. The differential pressure is very low. You
*need*
big holes or some means of achieving a forced draught like a fan or a
compressor.

Yes obviously the pressure differential is very low compared to an internal
combustion engine but I think I've figured out why the design I referred to
has such large air holes. It's to generate very high temperatures with
massive oxygen supply and burn the contents as quickly and thoroughly as
possible. In other words a pure incinerator rather than a heat source.

I've realised this is not what I'm after. I want a steady heat and for the
fuel to last as long as possible so I clearly need much less air induction.
I think I'll have to just suck it and see but I'll start off with a few 1/2"
holes and I can always enlarge them later. I may even need to make flaps to
control the air intake to regulate the burn speed.
--
Dave Baker

"Dave Baker" wrote in message
...
Wanting to make one of these for myself to burn garden waste and household
rubbish and maybe in time to make something to heat the garage in winter.
Came across this web site with design details for a 900 degree C
incinerator.

http://adlib.everysite.co.uk/resourc...cineration.pdf

What puzzles me is why it needs such large air holes. 11 x 50mm air holes
at the base and a further 8 x 60mm holes further up. As an airflow
specialist in the design of car engine cylinder heads I know how fast
enormous volumes of air gets through very small holes with just the 15 psi
of our planet's atmospheric pressure pushing it.

You don't have 15psi of air pushing it.
At light up you have zero pressure difference.
When it's up, running and warm you will only have natural convection,
ie maybe 1/100psi.

Your information is I think long outof date, I don't think you are allowed
to burn plastic in a device like this.
These sort of incinerators are very ineffective and polluting, you may find
there are local byelaws against their use for any purpose.
If you have neighbours you will definitely **** them off with the stinking
thing.



It seems to me that a few half inch holes would feed any size of fire that
could possibly burn in an oil drum. I imagine these people have done
research and experiments before settling on the optimum design but it
still stumps me. Any comments?
--
Dave Baker

Dave Baker
Wanting to make one of these for myself to burn garden
waste and household rubbish and maybe in time to make
something to heat the garage in winter.
I'd be interested to know how you would heat the garage in
winter?

How to use the heat without using the carbon monoxide and
other noxious fumes?

Came across
this web site with design details for a 900 degree C
incinerator.

John

--
John Mulrooney
NOTE Email address IS correct but might not be checked for a while.

The world is full of willing people; some willing to work, the rest willing to let them.

"Huge" wrote in message
...
On 2013-08-17, JTM wrote:
Dave Baker
Wanting to make one of these for myself to burn garden
waste and household rubbish and maybe in time to make
something to heat the garage in winter.
I'd be interested to know how you would heat the garage in
winter?

How to use the heat without using the carbon monoxide and
other noxious fumes?

I assume he's talking about making a room sealed stove. A rather larger
one than the ones customarily made from butane cylinders.

Yep. Ain't no one within a couple of hundred yards to pay no nevermind to
any smoke out here in the country and it sure would be nice to have a wood
stove with a little chimbley out through the wall or the roof to sit around
and jaw with friends when the snow and rain is lashing down outside.

Or I could just stay in the nice warm centrally heated house and leave doing
stuff in the garage till summer.
--
Dave Baker

In message , Dave Baker
writes

"Huge" wrote in message
...
On 2013-08-17, JTM wrote:
Dave Baker
Wanting to make one of these for myself to burn garden
waste and household rubbish and maybe in time to make
something to heat the garage in winter.
I'd be interested to know how you would heat the garage in
winter?

How to use the heat without using the carbon monoxide and
other noxious fumes?

I assume he's talking about making a room sealed stove. A rather larger
one than the ones customarily made from butane cylinders.

Yep. Ain't no one within a couple of hundred yards to pay no nevermind
to any smoke out here in the country and it sure would be nice to have
a wood stove with a little chimbley out through the wall or the roof to
sit around and jaw with friends when the snow and rain is lashing down
outside.

There are modestly priced workshop stoves available. Apart from
discomfort, the downside to unheated workshops is the restriction of
10deg. C for most commonly used wood glues. My carpenter gets round this
by only heating a small, insulated office area and then carrying stuff
in there.

Or I could just stay in the nice warm centrally heated house and leave
doing stuff in the garage till summer.

Yes:-)

You would probably need to keep a stove ticking over to be able to reach
*comfort level* for an hour or so pottering.

--
Tim Lamb

On Sat, 17 Aug 2013 11:16:38 +0100, Tim Lamb wrote:

You would probably need to keep a stove ticking over to be able to reach
*comfort level* for an hour or so pottering.

Why tick it over? Good burn and even a tiny stove will whack out the
heat. I suspect that Mr Bakers "shed" is bit bigger than 6x8 or even
single garage size. So a tiny stove might not be a good idea.

If Mr Baker would like a centrally heated "shed" there is an
Coalbrookdale Much Wenlock stove with boiler not a million miles from
me not doing a lot... Nominal 5 kW. Buyer collects, it's frigging
heavy!

--
Cheers
Dave.