Atmospheric pressure combustion

There are some topics that are not covered and some that are not treated extensively. Since the majority of industrial applications use gaseous fuels, there is more treatment of that type of fuel, with less discussion of liquid and solid fuels. This book concerns atmospheric pressure combustion, which is the predominant type used in most industrial applications. There are some burner designs, combustors, and applications that are not considered. 

An improved procedure has been described for atmospheric-pressure combustion of samples from high-purity metals [74]. High-pressure digestion with nitric and hydrofluoric acids 75], [76] and combustion techniques have both been shown to be suitable for the decomposition of samples of silicate-containing materials and fuels. Combustion in this case is carried out either in a stream of oxygen [77] or, to provide a closed system, in an oxygen bomb [78]. Mercury can be satisfactorily determined after prior Wickbold ashing [79]. 

Rybitskaya, L Shmakov, A. Korobeinichev, O. (2007). Propagation Velocity of Hydrocarbon-Air Flames Containing Organophosphorus Compeunds at Atmospheric Pressure, Combustion, Explosion, and Shock Waves, Vol. 43, No. 3, pp. 253-257, ISSN 0010-5082... 

Carrying out a combustion. The apparatus (Fig. 85, p. 469) will have been left with the bottle W connected to the beak of the combustion tube via the guard tube V and with all the taps shut, the combustion tube, which is dways allowed to cool down while connected to the oxygen source, will therefore be full of oxygen at slightly above atmospheric pressure, thus preventing any leaking in of carbon dioxide or water vapour from the air. 

Combustion. The primary reaction carried out in the gas turbine combustion chamber is oxidation of a fuel to release its heat content at constant pressure. Atomized fuel mixed with enough air to form a close-to-stoichiometric mixture is continuously fed into a primary zone. There its heat of formation is released at flame temperatures deterruined by the pressure. The heat content of the fuel is therefore a primary measure of the attainable efficiency of the overall system in terms of fuel consumed per unit of work output. Table 6 fists the net heat content of a number of typical gas turbine fuels. Net rather than gross heat content is a more significant measure because heat of vaporization of the water formed in combustion cannot be recovered in aircraft exhaust. The most desirable gas turbine fuels for use in aircraft, after hydrogen, are hydrocarbons. Fuels that are liquid at normal atmospheric pressure and temperature are the most practical and widely used aircraft fuels kerosene, with a distillation range from 150 to 300 °C, is the best compromise to combine maximum mass —heat content with other desirable properties. For ground turbines, a wide variety of gaseous and heavy fuels are acceptable. 

W ste Hea.t Boilers. In a conventional FCCU flue gas system, the regenerator combustion gases pass through two stages of cyclonic separators, a sHde valve, orifice chamber, waste heat boiler, and electrostatic precipitator. The sHde valve and orifice chamber act in combination to reduce the flue gas to essentially atmospheric pressure. 

Figure 4-3. Ammonia combustion at atmospheric pressure, absorption at gas compressor discharge pressure of 3-12 bar (Process 1, low-pressure combusion).

OSHA 1910.106 (based on die 1969 edidon of NFPA 30) and NFPA 30 (2000) designate where conservation vents and flame arresters may be needed on storage tanks or process vessels containing flammable or combustible liquids at atmospheric pressure. Sections (b)(2)(iv)(f) and (g) of OSHA 1910.106 state as follows ... 

Pq = atmospheric pressure Cq = atmospheric sound speed E = amount of combustion energy Rq = charge radius... 

In France in 1862, Beau de Rochas outlined the principles of the four-stroke engine so common today. ITowever, he never transformed those principles into hardware. Among the improvements proposed by de Rochas was compression of the charge prior to combustion. In contrast, the charge in the Lenoir engine was essentially at atmospheric pressure when combustion was initiated. 

The horizontal line at the bottom of the pressure-volume diagram of Figure 4 traces the other tv o strokes of the four-stroke cycle. On the exhaust stroke, from 5 to 6, the rising piston expels most of the remaining combustion products from the cylinder. On the intake stroke, from 6 to 7 (= 1), the descending piston inducts a fresh charge for repetition of the cycle. The net thermodynamic work developed in this cycle is proportional to the area enclosed by the pressure-volume diagram. In the ideal case, both the exhaust and intake strokes occur at atmospheric pressure, so they have no effect on the net output work. That justifies their exclusion from the thermodynamic representation of the ideal Otto... 

Figure 7-48. Effect of initial temperature on limits of flammability of a combustible vapor-inert-air system at atmospheric pressure. By permission, U.S. Bureau of Mines, Bulletin 627 [43].

Fans direct air movement within the furnace or combustion area. The two primary fan designs are forced draft and induced draft. Draft is the difference between atmospheric pressure and the static-pressure of combustion gases. 

Forced draft fans (FD fans) provide a positive air and combustion gas static pressure above that of atmospheric pressure. Almost all boilers have FD fans that force air from boiler inlets through the furnace and convection-pass sections. 

Dreyer, C.B., Spuler, S.M., and Linne, M., Calibration of laser induced fluorescence of the OH radical by cavity ringdown spectroscopy in premixed atmospheric pressure flames. Combust. Sci. Tech., 171,163, 2001. 

Diagram and photograph of a model gas turbine combustor operating on CH4/air at atmospheric pressure. Fuel is injected from an annulus separating two swirhng air streams. (From Meier, W., Duan, X.R., and Weigand, R, Combust. Flame, 144,225,2006. With permission.)... 

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