GEK Wiki / Nichrome-Burner-Ignition-Test
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Nichrome-Burner-Ignition-Test

Page history last edited by Banned User 10 years, 3 months ago

Nichrome Burner Ignition Test

Date: 2/10/09-2/11/09

 

Purpose:

The test was conducted to test the effectiveness of nichrome wire to ignite a propane/air mix within the GEK swirl burner.

Needs to be tested with wood gas

 

Design:

The current best design uses a thin piece of nichrome wire tightly coiled a few times within the burner and then run through an insulating ceramic sheath (from a large diameter non-stainless sheated TC probe's insulation).

 

Results:

The nichrome element (wire salvaged from an old hair drier) worked.

See this video:

http://www.youtube.com/watch?v=-nwW8AxvwKw

Note that propane/air ratio was being changed during the video.

 

Potential Improvements:

  • Thicker conductors should be run through the sheath, since currently, the wire inside the sheath is not exposed to cooling gas flow and gets hotter than the intended igniting coil within the burner.
  • Ideally, a circuit could be developed to maintain a constant temperature of the coil so that proper ignition temps are maintained and the element does not burn out (increased flow rate cools the element, combustion (over) heats the element).
  • Use a thicker gauge of wire (at the expense of increased wattage)
  • (DanielC: locate the heater element in the motive air stream, before it goes through the nozzle.  Apply power to it if air pressure is present, and if wall temperature of cyclone burner is less than a temperature that indicates combustion.  The idea here is to heat the motive air stream hot enough to autoignite the pumped gas (pilot propane, and/or induced woodgas), cut off power once ignition is established, and reapply power if flameout is detected.  Placing the heating element inside the motive air stream ought to ensure that it is not at risk of burnout due to overtemp, since that's a location that always will have a good flow of air past it, once we see a certain threshold pressure there)
  • (DanielC:  Let's spend our limited and valuable engineering time on innovative gasification problems, and buy as many things as we can as purchased-off-the-shelf-obtanium.  Look at p.32 of this Harman P68 Pellet stove manual (.pdf); we can use the "Igniter Element 3-20-06783".  Other interesting parts there too...)
  • (DanielC: if at all possible, heater wattage ought to be low enough so that a single 120V/1500W source of power can run the entire GEK.)
  • (DanielC: this is a worthwhile area to spend a little engineering time on, IMO.  I think that sooner or later, the GEK itself ought to get an automatic ignition system.  A successful implementation here, can be directly cloned and placed in one of the gasifier's air inlet tubes; this will allow the gasifier to be lit by an electrically-heated air stream)
  • (DanielC: OK, this is pimpage.  Make it an auto-light, auto-propane-piloted flare burner.  We can add automated control to the propane flow; a simple on/off electrically controlled valve ought to be sufficient.  For safety, propane would be turned on only when ignition would be assured (make sure air temp is > 600C?).  An automotive O2 sensor mounted in the cyclone will tell us when enough woodgas is flowing (we'll see it indicate richness), at which point the propane can be shut off.  If the burner flames out,  the wall temperature will fall and the air heater will come on.  If the O2 sensor indicates an overly lean condition, the propane flow could be restarted) 

 

Additional Information:

Ignition Temperature in Air 920-1020°F (493-549°C) (source: http://www.propane101.com/aboutpropane.htm)

Comments (1)

seachanged said

at 12:59 pm on Apr 24, 2009

For about 90 bucks you can buy a module for your gas stove that integrates a plasma flame sensor
and high voltage igniter spark, with associated logic. You provide a spark gap in the flame. When the
module is energized (usually with an on/off switch integrated into the gas control valve for a burner on
your stove), a spark is pulsed at about a 3 hertz rate until a flame is sensed at the sparking electrode.
If the flame is blown out, the sequence will restart.

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