Spontaneous ignition and oscillatory cool-flames in closed vessels

2 Spontaneous ignition and oscillatory cool-flames in closed vessels 

Such oscillations can be observed by a faint blue luminescence which originates from an electronically excited state of formaldehyde formed in reactions (2) and (3), [118,119], 

The light output which accompanies the final stage of two-stage ignition is considerably more intense. It is characteristic of the emission from premixed flames of hydrocarbons and arises predominantly from chemiluminescent reactions, mainly giving electronically excited CH, C, col and OH [123]. 

Although Fig. 6.10 is presented in a general form, very many specific examples are published in the literature because, often, it is important to characterize the conditions in which different reaction modes are observed before any other detailed investigations are made [125-127]. The reactant pressures and vessel temperatures at which the different features occur are dependent not only on the particular fuel and its proportions with oxygen or air but also on the size and shape of the vessel [121]. Surface reactions may play some part also, especially in the initiation processes, so the quantitative details are usually specific to the particular system employed 

For the most reactive substances (such as acetaldehyde or diethyl ether in equimolar proportions with oxygen) the minimum ignition temperature is at about 480-500 K as the pressure approaches 100 kPa in normal laboratory experiments (typically vessels of up to 0.5 dm ). The apex of the 

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