28. An examination of the mechanism by which “cool” flames give rise to “normal” flames. Part IV. The chemical character of the “blue” flame initiated in the “cool” flame products of ether–oxygen mixtures

1940 ◽  
Vol 0 (0) ◽  
pp. 151-156 ◽  
Author(s):  
M. Maccormac ◽  
D. T. A. Townend
Keyword(s):  
Cool Flame ◽  
Cool Flames ◽  
Ether Oxygen ◽  
Chemical Character ◽  
Blue Flame

Cool flames in the combustion of toluene and ethylbenzene

1956 ◽  
Vol 238 (1213) ◽  
pp. 143-153 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Light Intensity ◽  
Benzoic Acid ◽  
Aromatic Compounds ◽  
Flow System ◽  
Reaction Vessel ◽  
Static System ◽  
Cool Flame ◽  
Cool Flames ◽  
Blue Flame

The oxidation of toluene and ethylbenzene has been studied in a static system using a spherical reaction vessel (700 ml.) over the temperature range 300 to 500°C, and at total pressures up to 600 mm. Cool flames were observed in the oxidation of both hydrocarbons, but only the reaction of ethylbenzene gave rise to a ‘blue’ flame at higher temperatures. With neither hydrocarbon did periodicity in light intensity, or pressure pulses, occur. The ignition diagrams for 4 to 1 fuel + oxygen mixtures have been mapped out. With ethyl­benzene, the cool flame was maintained in a flow system, its spectrum was photographed and shown to be similar to that of fluorescent formaldehyde. The products of the reaction con­tained acetophenone, benzaldehyde and benzoic acid, phenol, quinol, hydrogen peroxide and methoxyhydroperoxide. The results have been compared with corresponding data for the oxidation of paraffin hydrocarbons, and it is concluded that, with both aromatic compounds, the processes allowing the possibility of cool-flame formation are themselves secondary in nature.

A mathematical model of the cool-flame oxidation of acetaldehyde

1971 ◽  
Vol 322 (1550) ◽  
pp. 377-403 ◽  
Keyword(s):  
Mathematical Model ◽  
Negative Temperature ◽  
Isothermal Oxidation ◽  
Limited Range ◽  
Detailed Model ◽  
Cool Flame ◽  
Induction Periods ◽  
Cool Flames ◽  
Satisfactory Account ◽  
Flame Oxidation

A detailed mathematical model of the non-isothermal oxidation of acetaldehyde has been found to give a realistic simulation of (i) single and multiple cool flames, their limits, amplitudes and induction periods; (ii) two-stage ignition; and (iii) the negative temperature coefficient for the maximum rate of slow combustion. A simplified form of the model, valid over a limited range of conditions, has been subjected to mathematical analysis to provide interpretations of the effects simulated by the detailed model. It is concluded that cool flames are thermokinetic effects often, but not exclusively, of an oscillatory nature, and that a satisfactory account of cool-flame phenomena must necessarily take reactant consumption into account.

scholarly journals Nitric Oxide Circumstances in Nitrogen-Oxide Seeded Low-Temperature Powling-Burner Flames

2017 ◽  
Vol 3 (3) ◽  
pp. 157
Author(s):  
M. Furutani ◽  
Y. Ohta ◽  
M. Nose
Keyword(s):  
Nitric Oxide ◽  
Low Temperature ◽  
Hydrogen Cyanide ◽  
Chemical Species ◽  
Nitrogen Monoxide ◽  
Cool Flame ◽  
Spectrum Measurement ◽  
Temperature Development ◽  
Flame Region ◽  
Blue Flame

<p>Flat low-temperature two-stage flames were established on a Powling burner using rich diethyl-ether/ air or n-heptane/air mixtures, and nitrogen monoxide NO was added into the fuel-air mixtures with a concentration of 240 ppm. The temperature development and chemical-species histories, especially of NO, nitrogen dioxide NO<sub>2</sub> and hydrogen cyanide HCN were examined associated with an emission-spectrum measurement from the low-temperature flames. Nitrogen monoxide was consumed in the cool-flame region, where NO was converted to the NO<sub>2</sub>. The NO<sub>2</sub> generated, however, fell suddenly in the cool-flame degenerate region, in which the HCN superseded. In the blue-flame region the NO came out again and developed accompanied with remained HCN in the post blue-flame region. The NO seeding into the mixture intensified the blue-flame luminescence probably due to the cyanide increase.</p>

The oxidation of hexane in the cool-flame region

1952 ◽  
Vol 212 (1110) ◽  
pp. 311-330 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Chemical Nature ◽  
Complex Mixture ◽  
Cyclic Ethers ◽  
Reaction Products ◽  
Cool Flame ◽  
Oxidation Of Methane ◽  
Cool Flames ◽  
Flame Region ◽  
Considerable Support

The chemical nature of the cool flame of hexane at 300°C, maintained stationary in a flow system at atmospheric pressure, has been investigated. The relative intensities of cool flames obtained from mixtures of differing composition have been measured, using a photomultiplier cell, and correlated with analyses made of the complex mixture of reaction products. The stationary two-stage flames which may be obtained at either higher oxygen concentrations or higher pressures than the cool flame are also described, and investigated similarly. The results are examined in the light of a theory of combustion of the higher hydrocarbons via aldehydes and hydroxyl radicals, which is an extension of a mechanism derived for the oxidation of methane. This receives considerable support, particularly from the identification of the complete homologous series of saturated aldehydes which can result from the hexane molecule. Associated with these reactions are others due to the greater stability of peroxide radicals at 300°C than at the higher temperatures of methane oxidation. Thus the building up of a partial pressure of hydroperoxide sufficient to ignite in the presence of oxygen may initiate the cool flame, and considerable amounts of cyclic ethers have been found which probably had a peroxidic precursor.

scholarly journals The combustion of aromatic and alicyclic hydrocarbons. V. The products of combustion of benzene and its monoalkyl derivatives

1940 ◽  
Vol 175 (963) ◽  
pp. 539-563 ◽  
Keyword(s):  
Analytical Methods ◽  
Aliphatic Aldehyde ◽  
Combustion Products ◽  
Side Chain ◽  
Benzene Nucleus ◽  
Rapid Degradation ◽  
Cool Flame ◽  
Cool Flames ◽  
Stage Process ◽  
Characteristic Features

The progressive formation of products in the combustion of benzene and its monoalkyl derivatives has been studied by analytical methods, and the characteristic features of the isothermal reactions at various temperatures have been established. A cool-flame reaction of n -propylbenzene has also been investigated, and by comparison with corresponding isothermal combustions, it is concluded that the propagation of cool-flames is conditioned by the accumulation of a phenylalkyl hydroperoxide. The results are interpreted in the light of the theory of the two-stage process, and a schematic mechanism for the main combustion reaction is outlined. This comprises degradation of the side-chain (if present) and rupture of the benzene nucleus, followed by rapid degradation of the higher aliphatic aldehyde thus formed, yielding finally formaldehyde and the ultimate combustion products CO 2 , CO and H 2 O.

Numerical studies of a thermokinetic model for oscillatory cool flame and complex ignition phenomena in ethanal oxidation under well-stirred flowing conditions

1989 ◽  
Vol 422 (1863) ◽  
pp. 289-310 ◽  
Keyword(s):  
Numerical Study ◽  
Thermal Characteristics ◽  
Kinetic Scheme ◽  
Ambient Conditions ◽  
Two Stage ◽  
Experimental Conditions ◽  
Cool Flame ◽  
Cool Flames ◽  
Spatial Uniformity ◽  
Acetyl Radical

A numerical study has been undertaken to predict quantitatively each of the non-isothermal reaction modes (stationary-state reaction, oscillatory cool flames and oscillatory two-stage and multiple-stage ignitions) associated with the oxidation of ethanal in a non-adiabatic well-stirred flow system (0.5 dm 3 ) at a mean residence time of 3 s. The kinetic scheme comprises 28 species involved in 60 reactions and it is coupled to the thermal characteristics through enthalpy change in each step, heat capacities of the major components and a heat transfer coefficient appropriate to heat loss through the reaction vessel wall. Spatial uniformity of temperature and concentrations is assumed, matching the experimental conditions. Very satisfactory accord is obtained between the experimentally measured and predicted location of the different reaction modes in the ( p - T a ) ignition diagram (where p is pressure and T a is temperature at ambient conditions), and the time-dependent patterns for oscillatory reaction agree with experimental measurements. The competition between degenerate branching and non-branching reaction modes is governed ultimately by the equilibrium CH 3 +O 2 ⇌CH 3 O 2 . The predicted behaviour is found also to be especially sensitive to the rate of decomposition of the acetyl radical CH 3 CO + M → CH 3 + CO + M. Corrections for its pressure dependence are essential if the predicted form of the oscillatory cool flame region in the ( p - T a ) diagram is to match the experimental results. Variations of the rate of this reaction also give new kinetic insight into the origins of complex oscillatory wave-forms for cool flames that have been observed experimentally. Relationships between the results of the detailed kinetic computations and the predictions from a three-variable, thermokinetic model are examined. This model is the simplest of all reduced schemes that makes successful predictions of two-stage ignition phenomena.

The effect of hydrogen bromide on the products of the cool-flame combustion of n -pentane

1974 ◽  
Vol 341 (1625) ◽  
pp. 195-212 ◽  
Keyword(s):  
Initial Temperature ◽  
Hydrogen Bromide ◽  
Transient Temperature ◽  
Cool Flame ◽  
Flame Combustion ◽  
Cool Flames ◽  
Main Effect ◽  
Halogen Compound ◽  
Almost All ◽  
Uncatalysed Reaction

Detailed studies have been made of the products of the cool-flame combustion of n -pentane in the absence and presence of small concentrations (2-6 vol. %) of added hydrogen bromide. In the uncatalysed reaction, acetone and acetaldehyde are the principal products formed at low temperatures during the induction period preceding the first cool flame but increasing amounts of C 5 alkenes and O-heterocycles start to be formed as the initial temperature is increased. The main effect of hydrogen bromide is to increase dramatically the yields of C 5 ketones at the expense of almost all the other products. The results indicate that in the absence of the halogen compound the principal fate of the initially formed pentylperoxy radicals is isomerisation to hydroperoxypentyl radicals. At 250 °C, the latter radicals mainly add on further oxygen and are eventually converted to pentanedihydroperoxides; at higher temperatures, the hydroperoxypentyl radicals tend increasingly to decompose directly to give principally pentenes and C 5 O-heterocycles. Hydrogen bromide alters the mechanism operating with binary mixtures primarily by providing a source of readily abstractable hydrogen and thus enhancing the formation of pentenemonohydroperoxides. Control experiments on the homogeneous breakdown of pentane-2-monohydroperoxide show that the principal decomposition product is pentan-2-one and thus confirm the probable importance of pentanemonohydroperoxides as intermediates in the HBr-promoted reaction. Studies of the chemical changes accompanying the passage of cool flames show that these vary considerably with the prevailing conditions as well as with the number of previous cool flames which have propagated through the mixture. Hydrogen bromide causes well-defined differences in the nature and distribution of the products of the combustion of n -pentane, although these changes are not as great as those brought about by the passage of cool flames which generally lead to considerable transient temperature rises in the system.

Low-temperature oxidation and cool flames of propane

1954 ◽  
Vol 221 (1145) ◽  
pp. 151-170 ◽  
Keyword(s):  
Low Temperature ◽  
Thermal Instability ◽  
Analytical Study ◽  
Simple Explanation ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
Cool Flame ◽  
Cool Flames ◽  
Oxidation Of Hydrocarbons ◽  
Flame Oxidation

A detailed analytical study of the cool-flame oxidation of propane has been carried out using a continuous-flow technique with a view to the further elucidation of the mechanism of the low-temperature oxidation of hydrocarbons. The formation of the three theoretically possible aldehydes has been demonstrated and the initially formed peroxide shown to be hydrogen peroxide. Measurements of the yields of the different products formed under varying conditions of temperature, composition and time of contact have been made and correlated with measurements of the luminous intensity and temperature of the flame. The results confirm the earlier conclusions of Norrish (1948) that aldehydes are the important branching agents in the temperature range of 300 to 400°C, and a detailed scheme based on that proposed earlier has been developed to account for the observations. The scheme has further been shown to allow of a simple explanation of the origin of the periodic character of the cool flame in terms of the thermal instability of the normal slow reaction.

Sign in / Sign up

Export Citation Format

Share Document