Topic
Cool flame
About: Cool flame is a research topic. Over the lifetime, 545 publications have been published within this topic receiving 11586 citations.
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Book•
1 Jan 1957
TL;DR: In this paper, the authors studied the spectrum of the Bunsen flame and its relationship with other spectra, such as the spectra of the carbon monoxide flame bands and the carbon dioxide flame bands.
Abstract: I. Flame Spectra.- The purpose of studying flame spectra.- Types of spectra.- The structure of flames.- The spectrum of the Bunsen flame.- Equilibria, radiation and collision processes.- II. Experimental Methods.- The recording of spectra.- Spectrographic equipment.- Optical systems.- The study of absorption spectra.- Wavelength determination.- Intensity measurements.- Effects of flame shape.- III. Special Techniques.- Flat flames.- Low-pressure flames.- Temperature effects on flames.- Atomic flames.- Flash photolysis.- Shock tube studies.- Fluorescence and laser-Raman scattering.- Use of isotope shifts.- IV. Introduction to the Theory of Spectra.- Line or atomic spectra.- Bohr theory.- The spectra of diatomic molecules: vibrational structure.- Rotational structure of the spectra of diatomic molecules.- Electronic states of diatomic molecules.- Vibrational intensity distribution: the Franck.- Condon principle.- Predissociation.- Infra-red spectra.- Raman spectra.- Electronic spectra of polyatomic molecules.- Continuous spectra.- Ionization continua.- Dissociation continua.- Association continua.- The width and shape of spectrum lines.- V. Hydrogen Flames.- The OH bands.- Hydrogen/air flames.- Hydrogen/ oxygen flames.- Pressure effects.- Absorption spectra.- Excitation of metal spectra in H2/O2/N2 flames.- Candoluminescence.- Applications to combustion mechanism.- The hydrogen/nitrous oxide flame.- Flames with NO and NO2.- VI. The Carbon Monoxide Flame.- The spectrum.- The carbon monoxide flame bands.- The excitation of the flame bands.- The continuous spectrum: pressure and temperature effects.- Combustion processes for carbon monoxide.- Flames of carbon and carbon suboxide.- VII. The Spectra of Organic Flames.- The CH bands.- Bands of C2.- Vaidya's hydrocarbon flame bands (HCO).- The 4050 A "comet head" group (C3).- Emeleus's cool flame bands (CH2O).- Band systems of CO.- Other band systems in flames.- The carbon line, ?2478.- Premixed flames.- Diffusion flames.- Cool flames and preignition glows.- Absorption spectra.- VIII. Measurements of Effective Temperature and Studies with Special Sources.- Electronic excitation temperatures.- Translational temperatures from Doppler broadening.- Measurement of rotational temperatures: OH.- Rotational temperatures for CH, C2, NH etc.- Effective vibrational temperatures.- Predissociation.- Flash photolysis.- Atomic flames.- Spectra excited by shock waves.- Occurrence of C2 and CH in some special flames.- Isotope tracer experiments.- IX. The Infra-Red Region.- The amount of radiation from flames.- Infra-red spectra of organic flames.- Relative band intensities and temperature measurements.- Radiation from explosion flames.- Cool flames.- Flames with nitrous oxide.- Flames with halogens.- X. Flame Structure and Reaction Processes.- Reactions in cool flames.- The formaldehyde excitation process.- Reactions in diffusion flames.- Reactions in premixed flames.- Carbon formation in premixed flames.- Concentrations of free radicals.- Reactions forming excited species.- Ionization and electron temperatures.- The high electronic excitation in the flame front.- Effects on flame structure of lags in equipartition of energy.- XI. Explosions, Engines and Industrial Flames.- Explosions in closed vessels.- Detonations.- The internal combustion engine: flame fronts and afterburning.- Knock.- Compression-ignition (diesel) engines.- Engines with continuous combustion.- Exhaust flames.- Furnace flames.- Solid propellants.- XII. Flames Containing Nitrogen, Halogens, Sulphur and Inorganic Substances.- Flames of ammonia, hydrazine etc.- Flames of organic nitrogen compounds.- Flames supported by oxides of nitrogen.- Formation of oxides of nitrogen.- Ozone.- Halogens in oxidizing flames.- Flames supported by halogens.- Flames of sulphur, hydrogen sulphide and carbon disulphide.- Flames with added SO2, SO3 or H2S.- Phosphorus in flames.- Flames containing boron.- Metals in flames.- XIII. Flame Spectrophotometry.- The choice of flame type.- The burner and spray system.- Recording methods.- The relation between line intensity and concentration.- Interference by one element with the estimation of another.- Atomic absorption.- Atomic fluorescence.- Effects of flame disequilibria.- I Band spectra emitted by flames.- II Absorption spectra.- III Some atomic and molecular energy levels and constants.- References.- Author Index.- Subject Index (Including symbols used and values of physical constants).
883 citations
TL;DR: In this paper, the authors investigated the self-ignition of several spark-ignitions (SI) engine fuels (iso-octane, methanol, methyl tert-butyl ether and three different mixtures of iso-Octane and n-heptane), mixed with air, under relevant engine conditions by the shock tube technique.
573 citations
TL;DR: In this paper, the authors examined the effects of a wide range of parameters (injection pressure, orifice diameter, and ambient gas temperature, density and oxygen concentration) on lift-off length under quiescent diesel conditions.
Abstract: The reaction zone of a diesel fuel jet stabilizes at a location downstream of the fuel injector once the initial autoignition phase is over. This distance is referred to as flame lift-off length. Recent investigations have examined the effects of a wide range of parameters (injection pressure, orifice diameter, and ambient gas temperature, density and oxygen concentration) on lift-off length under quiescent diesel conditions. Many of the experimental trends in lift-off length were in agreement with scaling laws developed for turbulent, premixed flame propagation in gas-jet lifted flames at atmospheric conditions. However, several effects did not correlate with the gas-jet scaling laws, suggesting that other mechanisms could be important to lift-off stabilization at diesel conditions. This paper shows experimental evidence that ignition processes affect diesel lift-off stabilization. Experiments were performed in the same optically-accessible combustion vessel as the previous lift-off research. The experimental results show that the ignition quality of a fuel affects lift-off. Fuels with shorter ignition delays generally produce shorter lift-off lengths. In addition, a cool flame is found upstream of, or near the same axial location as, the quasi-steady lift-off length, indicating that first-stage ignition processes affect lift-off. High-speed chemiluminescence imaging also shows that high-temperature self-ignition occasionallymore » occurs in kernels that are upstream of, and detached from, the high-temperature reaction zone downstream, suggesting that the lift-off stabilization is not by flame propagation into upstream reactants in this instance. Finally, analysis of the previous lift-off length database shows that the time-scale for jet mixing from injector-tip orifice to lift-off length collapses to an Arrhenius-type expression, a common method for describing ignition delay in diesel sprays. This Arrhenius-based lift-off length correlation shows comparable accuracy as a previous power-law fit of the No.2 diesel lift-off length database.« less
412 citations
1 Jan 1996
TL;DR: In this article, the authors investigated the self-ignition behavior of diesel-relevant fuels as homogeneous mixtures with air using three high-pressure shock tubes and found that α-methylnaphthalene starts deflagrative at 13 bar for the complete investigated temperature range of 840-1300 K. Because of the low vapor pressure of some diesel-fuel representative hydrocarbons at ambient temperature, a new shock tube equipped with heating facilities was constructed to prevent condensation.
Abstract: The self-ignition behavior of diesel-relevant fuels as homogeneous mixtures with air has been investigated using three high-pressure shock tubes. Because of the low vapor pressure of some diesel-fuel representative hydrocarbons at ambient temperature, a new shock tube equipped with heating facilities was constructed to prevent condensation. The investigated fuels are the aromatic α-methylnaphthalene, the alkane n-decane, and dimethylether. The self-ignition process of α-methylnaphthalene starts deflagrative at 13 bar for the complete investigated temperature range of 840–1300 K. For temperatures above 960 K, a transition to a detonationlike process (DDT, secondary explosion) with strong pressure peaks can be observed. The duration of the transition from deflagration to the initiation of the DDT process decreases with increasing temperature. The self-ignition behavior of n-decane and dimethylether in the temperature range of 650–1300 K is very similar to that of n-heptane [8], with a two-step self-ignition (first step: cool flame process) at lower temperatures. A very short deflagrative phase is followed by a secondary explosion. The time difference between the first pressure rise caused by the cool flame process and the DDT decreases with decreasing temperature, whereas the intensity of the cool flame process increases. The ignition delay times of both n-decane and dimethylether show a negative temperature coefficient (NTC) in the Arrhenius plot. Within the temperature range of this investigation, the shortest ignition-delay times are observed for dimethylether.
386 citations
TL;DR: In this article, the products of oxidation are identified and time profiles are measured during a two-stage ignition process, showing that the high selectivity observed in the formation of lower 1-alkenes is explained by the scission of the β CC bond of the α-hydroperoxyheptyl radicals weakened by the presence of oxygen atoms.
266 citations
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Performance Metrics
| Year | Papers |
|---|---|
| 2022 | 1 |
| 2021 | 32 |
| 2020 | 25 |
| 2019 | 33 |
| 2018 | 14 |
| 2017 | 23 |