# help with spontaneous ignition in fluent

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 January 14, 2011, 05:33 help with spontaneous ignition in fluent #1 New Member   kd Join Date: Jan 2011 Posts: 9 Rep Power: 6 hi, i am trying to model simple problem of hydrogen dispersion. something like the model of methane and air model that exist in the tutorial guide of fluent. one inlet of air with slow velocity and small inlet of hydrogen with laminer velocity. the model is cyliner that open in the other side with outflow. i use traniset and laminer finite rate. in fluent user guide that is a sentence that say: "If you introduce fuel to an oxidant, spontaneous ignition does not occur unless the temperature of the mixture exceeds the activation energy threshold required to maintain combustion" when i choose the temp of the inlet gas 300k there is ignition but it's not suppose to happen. spontaneous ignition suppose to happen in at least 500 k of hydrogen! i hope someone can help thank very much!!!

 January 15, 2011, 11:26 #2 New Member   kd Join Date: Jan 2011 Posts: 9 Rep Power: 6 it's very important to me! i hope someone can give me a answer plz

 January 16, 2011, 11:49 #3 New Member   Join Date: Dec 2010 Posts: 2 Rep Power: 0 Hi Friend Try to initialize with 500k or 600k of inlet gas.

 January 20, 2011, 13:10 thank u for reply #4 New Member   kd Join Date: Jan 2011 Posts: 9 Rep Power: 6 thank u! but this exactly the problem! when I initializeD the problem with 500 or 600 kelvin there is ignition! autoignition of hydrogen suppose to be at ~830k at 1 bar ! until that temperture we need ignition sourch! someone know what the problem???

 January 22, 2011, 12:14 #5 Member   Nikolopoulos Aristeidis Join Date: Jan 2011 Location: Athens, Greece Posts: 62 Rep Power: 6 Your problem is that your reaction rate is not zero for 300K. Where do you find the constants for activation energy and pre-exponential factor? Moreover which is the order of the reaction with respect to oxygen?

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