Flames thermodynamics

LeChatelier Henry-Louis (1850-1936) Fr. metallurg., worked on chemistry of silicates and cements, physics of flames, thermodynamics, used first the dependence sample vs. environmental temperature, devised optical pyrometer LeChatelier Luis (1815-1926) Brit, mine eng., tested products with aluminum content, patented steel production, thermometry - use of thermocouples Legendre Adrien Marie (1752-1833) Fr. math., gave important works on elliptic integrals, laws of quadratic reciprocity, created spherical harmonics, known for Legendre transformations used in thermodynamics... 

Because the gaseous products ate ia thermodynamic equiUbtium at the flame temperature, quite accurate calculatioas of gas compositioa, maximum... 

Flame Temperature. The adiabatic flame temperature, or theoretical flame temperature, is the maximum temperature attained by the products when the reaction goes to completion and the heat fiberated during the reaction is used to raise the temperature of the products. Flame temperatures, as a function of the equivalence ratio, are usually calculated from thermodynamic data when a fuel is burned adiabaticaHy with air. To calculate the adiabatic flame temperature (AFT) without dissociation, for lean to stoichiometric mixtures, complete combustion is assumed. This implies that the products of combustion contain only carbon dioxide, water, nitrogen, oxygen, and sulfur dioxide. 

Adiabatic flame temperatures agree with values measured by optical techniques, when the combustion is essentially complete and when losses are known to be relatively small. Calculated temperatures and gas compositions are thus extremely useful and essential for assessing the combustion process and predicting the effects of variations in process parameters (4). Advances in computational techniques have made flame temperature and equifibrium gas composition calculations, and the prediction of thermodynamic properties, routine for any fuel-oxidizer system for which the enthalpies and heats of formation are available or can be estimated. 

Several techniques are available in the literature for evaluation of the flame temperature, exit temperature, equilibrium composition of combustion products, and performance parameters of energetic composites [11-13]. The optimum combination of the composite ingredients is determined by thermodynamic means, so as to arrive at a composition having maximum performance... 

Fundamental research in pyrotechnics is published in the US in Combustion and Flame by the Combustion Institute, and in the UK in Combustion Science and Technology and in Fuel . Germany has the new, journal, Propellants and Explosives (German Chemical Society), which is the successor to the discontinued Explosivstoffe . A necessary caveat is that these journals are strongly oriented toward combustion or propulsion so that only rarely do they yield pyrotechnic information. Likewise, the various publications of the learned societies contain much data on thermodynamics, spectroscopy, and instrumental analysis which are useful in the study of pyrotechnics. In the USSR the situation is somewhat better as Physics of Combustion and Explosion (Fizika Gorenia i Vzryva) of the Siberian Branch Academy of Sciences USSR is exclusively oriented toward subjects of interest, as several scientific institutes are primarily devoted to research in pyrotechnics. The same authors do publish also, however, in the journals of the Academy of Science USSR (of which there are several) as well as in the corresponding journals of the academies of the various republics, so that the impression is created of a high level of activity... 

In the nineteenth century, Humphry Davy (1778-1829) speculated that the luminosity of flames is caused by fhe production and ignition of solid particles of carbon as a resulf of the decomposition of a part of the gas. Jons Jakob Berzelius (1779-1848) is said to be the first to describe an ordinary candle flame as consisting of four disfincf zones. Davy s protege, Michael Faraday [9] (1791-1867) gave his Christmas lectures and accom-pan3ung demonstrations to a juvenile audience on "The Chemical History of a Candle" in 1848 and 1860. Around the turn of the century, modem combustion science was established based on the increased understanding of chemistry, physics, and thermodynamics. 

The reason for the formation of anatase phase at such a high temperature might be explained as following. The as-prqiared ultrafine titania particles are liquefied at sufficimtly high temperature because melting point of nanoparticlra are lower than that of bulk titania (1850 C). The liquid titania particles are supercooled and became metastable states. The residence time in the flame is only in the order of miU-second so that the metastable phase has no time to become thermodynamically stable phase, rutile. 

Assume steady burning with the sample originally at 25 °C with a perfectly insulated bottom. At extinction you can ignore the flame radiation. Assume that all of the flakes hit the surface and ignore the gas phase effects of the extinguishment agents. Use thermodynamic properties of the C02 and H20, and the property data of PMMA from Table 9.2. 

This part includes a discussion of the main experimental methods that have been used to study the energetics of chemical reactions and the thermodynamic stability of compounds in the condensed phase (solid, liquid, and solution). The only exception is the reference to flame combustion calorimetry in section 7.3. Although this method was designed to measure the enthalpies of combustion of substances in the gaseous phase, it has very strong affinities with the other combustion calorimetric methods presented in the same chapter. 

G. Pilcher. Oxygen Flame Calorimetry. In Experimental Chemical Thermodynamics, vol. 1 Combustion Calorimetry, S. Sunner, M. Mansson, Eds. IUPAC-Pergamon Press Oxford, 1979 chapter 14. 

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