another DDT question.

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SpudFarm
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Thu May 08, 2008 8:58 am

i am going to make a camera and a ignition coil setup, but if i talk to Larda he may digg up a flyback or something for me.

or i run like 10camera caps in one ignition coil
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psycix
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Thu May 08, 2008 4:45 pm

MrCrowley wrote:And I can't remember, but does DDT have a higher chance of occurring at a lower mix then higher?
IIRC, in the rule you can divide the DDT runup distance on atmospheric pressure by the amount X mix.
If a certain fuel has a runup distance of 100" at atmospheric pressure, then a 2x mix would only need 50", a 3x mix 33, 4x mix 25" and so on.

Im not sure about what I stated above.
Its just a vague memory.
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DYI
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Thu May 08, 2008 4:59 pm

Im not sure about what I stated above.
Its just a vague memory.
A vague memory indeed, from way back when people actually thought that 4x was approaching DDT.

In reality, the Nx has very little effect on the DDT runup distance of propane/air mixes. The increased pressure decreases burn rate, and the increased temperature of higher mixes just barely overcomes that effect. A 20x mix might burn a few m/s faster, but not enough to be really worrisome.
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