[Stoves] Riser Height and a 'Counter-Current' Woodgas Burner - YouTube Vid
Paul Anderson
psanders at ilstu.edu
Tue Jan 26 21:23:54 CST 2016
Julien,
It is great to see your systematic approach to these issues.
Paul
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 1/26/2016 10:01 AM, Marquitusus wrote:
> Very interesting Julian.
>
> Have you registered (or noticed) any mixing improvement with this
> prototype over the non counter-current ones? I suppose better mixing
> shoud be noticed as higher temperatures registered. Have you measured
> anything like this?
>
> Marc
>
> ------------------------------------------------------------------------
> From: jock at jockgill.com
> Date: Mon, 25 Jan 2016 20:04:58 -0500
> To: stoves at lists.bioenergylists.org
> Subject: Re: [Stoves] Riser Height and a 'Counter-Current' Woodgas
> Burner - YouTube Vid
>
> Julian,
>
> Interesting video.
>
> 1. I would try this with a flame retention disc rather than a central
> hole. I view central holes above fuel bed as a fundamental error. I
> know central holes are the given wisdom, but I view them as the source
> of problems that can not be overcome. They are a barrier to better
> achievements.
>
> 2. I would strive for the maximum amount of blue flame. I did not see
> any in your video. People want to cook with blue flames. Aspirational.
>
> 3. Perhaps an hour glass type device might work? Could be asymmetrical?
>
> Cheers,
>
> Jock
>
> Jock Gill
> P. O. Box 3
> Peacham, VT 05862
>
> google.com/+JockGill
> <https://plus.google.com/_/notifications/emlink?emr=02164940119180120523&emid=CIn6jOiavboCFcgLTAodARYAAA&path=/102260924343967128597/op/u&dt=1383089746165&ub=50>
>
> Extract CO2 from the atmosphere!
>
> On Jan 25, 2016, at 7:10 PM, Julien Winter <winter.julien at gmail.com
> <mailto:winter.julien at gmail.com>> wrote:
>
> Hi all;
>
>
> I have posted a video on YouTube on Riser Height and a
> 'Counter-Current' burner that continues on the theme of
> discussions earlier this month about premixed flames.
>
> https://youtu.be/KzYUzJPM3eQ
>
> The purpose of this video is to demonstrate the importance of
> riser height on the function of a natural draft, top-lit updraft
> gasifier using the “Counter-Current Woodgas Burner” (CCWB).Riser
> height affects the flow rate of both primary and secondary air,
> and the degree of turbulent mixing of woodgas with secondary
> air.Increasing riser height creates greater buoyancy forces that
> can improve the efficiency of stove combustion, and stove
> responsiveness for the operator, but it can lead to excessive
> secondary air, and excessive turbulence under some conditions.
>
> With a true counter-current burner, the fuel gas and oxidizer gas
> collide head-on.This is more-or-less what happens with the CCWB,
> because a downward laminar flow of secondary air is sent against
> the upward flow of woodgas.However, it is not a perfect
> counter-current burner, because a lot of the secondary air is
> pulled sideways by the buoyancy force created in the gas flame.
>
> The main objective of the CCWB is to get a much turbulent mixing
> of secondary air and woodgas at the base of the gas flame as
> possible.We are trying to approach an ideal of a pre-mixed flame
> at somewhat above (to be determined) the stoichiometric
> requirement for oxygen.
>
> The second objective of the CCWB is to locate the base of the
> flame over the fuel bed char.Some secondary air supports glowing
> char, and sustains a higher temperature in the fuel bed, from the
> ignition front up to the top of the char, than would be obtained
> if the secondary air and the gas flame were located at some
> distance above the fuel bed.Glowing char can help with cracking of
> tars, and provide heat to assist in the piloting of gas
> ignition.This helps maintain woodgas flame stability at low
> gasification rates.
>
> Some modifications of the CCWB have been tried, but did not show
> much benefit.(1) A ring of small air holes (of various numbers and
> diameters) in the sidewall of the reactor were positioned just
> below the inner riser.It was thought that these holes would
> provide small flamelets that would keep the gas flame from
> extinguishing at very low gasification rates.It was found that
> these holes didn’t help, and functioned more to diminish the role
> of the counter-current air flow. (2)Various fins were made at the
> bottom of the internal riser to see if they would increase
> turbulence.Fins were found to be unnecessary.
>
> The stoves in this video are prototypes.They are working
> hypotheses that need scientific stove testing to optimize their
> geometry, and validate the counter-current approach. To become
> working stoves, they need a regulator for primary air, an
> insulated external riser, and mechanism to transfer the heat to
> the pot or other object of work.
>
>
> If the CCWB can be shown to improve combustion efficiency on
> diverse biomass fuels, and over a wide range of gasification
> rates, that would be good, because it is a very easy burner to build.
>
>
> Cheers,
>
> Julien.
>
>
>
> --
> Julien Winter
> Cobourg, ON, CANADA
>
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