Ignition energy of hydrogen

Hydrogen is also one of the easiest explosives to ignite when suitably mixed with air or oxygen. For example, the ignition energy of hydrogen (H2), methane (CH4), and propane (CsHg) are 0.02,... 

Ono, R., Nifuku, M., Fujiwara, S., Horiguchi, S., Oda, T., 2(X)7. Minimum ignition energy of hydrogen-air mixture effects of humidity and spark duration. Journal of Electrostatics 65 (2), 87-93. 

Hydrogen is produced or used in gas or liquid form in a number of processes. Hydrogen is a colorless, odorless gas that is easily ignited over a wide flammable range. Hydrogen burns very rapidly and cleanly in air with a nearly invisible clear blue flame. It has flammable limits of 4-74% in air and minimum ignition energy of 0.02 mj, compared to 0.25 mj for typical hydrocarbons. 

Since the bond dissociation energy of hydrogen iodide is less than that of hydrogen bromide [DH-i, 70.5 kcal. DH-Br, 86.5 kcal. (3)], Reactions 6, 7, and 8 should occur more readily with hydrogen iodide. This would account for the fact that the promoting effect of iodine compounds on ignition is less than that of bromine compounds. 

To maximize power output a stoichiometric mixture is demanded for engine combustion. The main limitation for stoichiometric operation in combination with external mixture formation is backfire into the intake manifold and uncontrolled preignition caused by the wide ignition limits of hydrogen-air mixtures and the low ignition energy demands. 

Hydrogen has a wider range of flammability limits and a lower ignition energy than other fuels. 

Several of the combustion-related properties of hydrogen in air, such as its wide flammability limits (4-75 vol%), wide detonation range (20-65 vol%), very low spark ignition energy (0.02 mJ), high heat of combustion (121 kJ/g) and high flame temperature (2050°C) combine to emphasise the high fire-related hazards of the... 

The product of sorbing hydrogen on to hot zirconium powder bums with incandescence when heated in air [1,2], Ignition and combustion properties of pyrophoric zirconium and zirconium hydride powder (< 10 p), and safety measures are discussed [3], Ignition energies for zirconium hydrides, ZrUx x = 0 — 2, in air have been studied in Japan [4],... 

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