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Re: Minimum Ignition Energy (mJ) of gases
Posted by: dcarpenter (IP Logged)
Date: January 02, 2018 03:35PM
I can only assume by your questions that you missed the point of my previous posting. However, I will engage your inquiry in the context of promoting education and the reliable application of fundamental knowledge.
The minimum ignition energy for Methane is from the classic reference:
Zebetakis, M.G. (1965), "Flammability Characteristics of Combustible Gases and Vapours," U.S. Bureau of Mines, Bulletin 627.
You will find a reproduction of the ignitability curve and limits of flammability for methane/air mixtures at atmospheric pressure and 26 degrees Celsius. This can be found on Page 87 of Dougal Drysdale's "An Introduction to Fire Dynamics," third edition.
I sense you are looking for the most accurate value for the MIE. As you may know, the concentration plays a role in this value and the MIE is found at the rich side of the Stoichiometric fuel/air ratio. The flammability limits widen with increasing temperature, so the most accurate value will be in the context of the associated temperature and pressure.
The values reported by Zebetakis were done with a specific apparatus developed by the U.S. Bureau of Mines. I have not assessed any differences in this work and the current ASTM standard. Again, in this application context, why is this significant beyond trying exploit inaccuracies in expert testimony that may not have any significance to the outcome of the analysis of the ignition of flammable vapors?
J L Mazerat Wrote:
-------------------------------------------------------
> Doug:
>
> I am not doubting you on your information. I
> assume the value you cite is from a ASTM E-582
> test. You cite the minimum ignition energy for
> methane as being .29 mJ. I have some questions
> based on the information contained in the
> standard. What was the test that produced that
> value? How many times were the test run? Were the
> results exactly the same each time. What was the
> concentration used in the test? Was there any
> variance in the concentration? If I were to have
> altered the concentration by .01% how much would
> that have changed the value, if any?
Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com
The minimum ignition energy for Methane is from the classic reference:
Zebetakis, M.G. (1965), "Flammability Characteristics of Combustible Gases and Vapours," U.S. Bureau of Mines, Bulletin 627.
You will find a reproduction of the ignitability curve and limits of flammability for methane/air mixtures at atmospheric pressure and 26 degrees Celsius. This can be found on Page 87 of Dougal Drysdale's "An Introduction to Fire Dynamics," third edition.
I sense you are looking for the most accurate value for the MIE. As you may know, the concentration plays a role in this value and the MIE is found at the rich side of the Stoichiometric fuel/air ratio. The flammability limits widen with increasing temperature, so the most accurate value will be in the context of the associated temperature and pressure.
The values reported by Zebetakis were done with a specific apparatus developed by the U.S. Bureau of Mines. I have not assessed any differences in this work and the current ASTM standard. Again, in this application context, why is this significant beyond trying exploit inaccuracies in expert testimony that may not have any significance to the outcome of the analysis of the ignition of flammable vapors?
J L Mazerat Wrote:
-------------------------------------------------------
> Doug:
>
> I am not doubting you on your information. I
> assume the value you cite is from a ASTM E-582
> test. You cite the minimum ignition energy for
> methane as being .29 mJ. I have some questions
> based on the information contained in the
> standard. What was the test that produced that
> value? How many times were the test run? Were the
> results exactly the same each time. What was the
> concentration used in the test? Was there any
> variance in the concentration? If I were to have
> altered the concentration by .01% how much would
> that have changed the value, if any?
Douglas J. Carpenter, MScFPE, CFEI, PE, FSFPE
Vice President & Principal Engineer
Combustion Science & Engineering, Inc.
8940 Old Annapolis Road, Suite L
Columbia, MD 21045
(410) 884-3266
(410) 884-3267 (fax)
www.csefire.com
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