Combustion prediction

Lockwood, F.C. and Shah, N.G. A new radiation solution method for incorporation in general combustion prediction procedures. In Proceedings of the 18th Symposium (International) on Combustion. Pittsburgh, PA The Combustion Institute, 1981, pp. 1405-1416. 

Although the prediction of N0X emissions under lean and stoichiometric combustion with the extended Zeldovich mechanism is adequate for certain applications, predictive methods for fuels containing bound nitrogen and for rich combustion conditions require substantial improvement. However, the early studies of Fenimore (13, 14) demonstrated the potential importance of HCN and NH type species in fuel-nitrogen interactions. To illustrate the critical importance of the coupling of nitrogenous species reactions in rich combustion, predictions of NO emissions from rich iso-octane combustion in a jet-stirred combustor are shown in Table III. C2 hydrocarbon fragmentation and oxidation creates... 

F. C. Lockwood and N. G. Shah, A New Radiation Solution Method for Incorporation in General Combustion Prediction Procedures, Eighteenth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, pp. 1405-1414,1981. 

Study on goaf spontaneous combustion prediction simulation of gas-drainage in spontaneously flammable and thick coal seam... 

Jun Deng, Zhcn Xing, Li Ma. Application of multiple regression analysis for the coal spontaneous combustion prediction. Journal of Xi an University of Science and Technology 2011 31(6) 645-648. 

Li X.Z. 2006. Research of Coal Spontaneous Combustion Prediction of the Gob of a High Inclination-angle Coal Seam Named 1409 Working Face in HuaFeng Mine. Xi An Xi An University of Science and Technology. 

Data for validating pulverized coal combustion predictions requires accurate information for the reactor parameters shown in Table VI. Data measured in the combustion chamber typically include (1) locally measured values of the gaseous flow field velocity, temperature, and species composition, (2) coal particle burnout, number density, velocity, temperature, and composition, and (3) wall temperatures and heat fluxes. Evaluation should include comparisons with measurements from a wide variety of combustors and furnaces that range in scale from very small laboratory combustors (0.01-0.5 MW) and industrial furnaces (1-10 MW) to large utility boilers (up to 1000 MW). 

Baxter, L. L., and DeSollar, R. W. (1993). A mechanistie deseription of ash deposition during pulverized coal combustion Predictions compared to observations, Fitel 72(10), 1411-1418. 

The length and time scales of chemical reactions are generally much smaller than the ones of the underlying flow. In fact, with today s computers, CFD computations cannot resolve all the scales in technically relevant combustion problems. Consequently, modeling is required to make meaningful combustion predictions. Since for fuel sprays the gas flow is usually turbulent, the fuel-air mixing process depends on the turbulence parameters from which the chemical reaction rates are determined. 

This section discusses two particular examples of one-dimensional combustion-predictive heat transfer models recently developed, those of Stoliarov and Lyon, [55], and McCarthy et al. [56], which aim to capture the point of ignition with associated mass loss, thermal profile, and release rates of volatiles and heat accompanying the decomposition and combustion of structural composites. 

Improving the cetane number by additives results in better engine behavior, as would be predicted by the combustion mechanisms in the diesel engine (noise reduction, better operating characteristics, particularly when cold). Nevertheless, concerning certain items such as pollution emissions, it may be better to obtain a higher cetane number rather by modification of the... 

Sirtori, S., P. Garibaldi and F.A. Vicenzetto (1974), Prediction of the combustion properties of gasolines from the analysis of their composition . SAE paper No. 74-1058, International Automobile Engineering and Manufacturing Meeting, Toronto, Ontario. 

Flammability. The results of small-scale laboratory tests of plastic foams have been recognized as not predictive of their tme behavior in other fire situations (205). Work aimed at developing tests to evaluate the performance of plastic foams in actual fire situations continues. All plastic foams are combustible, some burning more readily than others when exposed to fire. Some additives (131,135), when added in small quantities to the polymer, markedly improve the behavior of the foam in the presence of small fire sources. Plastic foams must be used properly following the manufacturers recommendations and any appHcable regulations. 

K. A. Bueters, J. G. CogoH, and W. W. Habelt, "Performance Prediction of Tangentially Eired UtiUty Eumaces by Computer Model," paper presented at the Fifteenth Symposium on Combustion, Tokyo, Japan, Aug. 25—31,1974, The Combustion Institute, Pittsburgh, Pa., 1975. 

The third characteristic of interest grows directly from the first, ie, the high thermal conductance of the heat pipe can make possible the physical separation of the heat source and the heat consumer (heat sink). Heat pipes >100 m in length have been constmcted and shown to behave predictably (3). Separation of source and sink is especially important in those appHcations in which chemical incompatibilities exist. For example, it may be necessary to inject heat into a reaction vessel. The lowest cost source of heat may be combustion of hydrocarbon fuels. However, contact with an open flame or with the combustion products might jeopardize the desired reaction process. In such a case it might be feasible to carry heat from the flame through the wall of the reaction vessel by use of a heat pipe. 

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. 

A unified statistical model for premixed turbulent combustion and its subsequent application to predict the speed of propagation and the stmcture of plane turbulent combustion waves is available (29—32). 

The study of the combustion of sprays of Hquid fuels can be divided into two primary areas for research purposes single-droplet combustion mechanisms and the interaction between different droplets in the spray during combustion with regard to droplet size and distribution in space (91—94). The wide variety of atomization methods used and the interaction of various physical parameters have made it difficult to give general expressions for the prediction of droplet size and distribution in sprays. The main fuel parameters affecting the quaHty of a spray are surface tension, viscosity, and density, with fuel viscosity being by far the most influential parameter (95). 

The modeling of fluidized beds remains a difficult problem since the usual assumptions made for the heat and mass transfer processes in coal combustion in stagnant air are no longer vaUd. Furthermore, the prediction of bubble behavior, generation, growth, coalescence, stabiUty, and interaction with heat exchange tubes, as well as attrition and elutriation of particles, are not well understood and much more research needs to be done. Good reviews on various aspects of fluidized-bed combustion appear in References 121 and 122 (Table 2). 

The emissions from combustion processes may be predicted to some extent if the variables of the processes are completely defined. Figure 6-7 indicates how the emissions from a combustion source would be expected to vary with the temperature of the reaction. No absolute values are shown, as these will vary greatly with fuel type, independent variables of the combustion process, etc. 

The model assumes that liquid evaporation is always the rate controlling step. At some point the model must fail, since as droplet size approaches zero the predicted MIE approaches zero rather than the MIE of the vapor in air. In practice, droplets having diameters less than 10-40 /rm completely evaporate ahead of the flame and burn as vapor (5-1.3). The model also predicts that the MIE continuously decreases as equivalence ratio is increased, although as discussed above, combustion around droplets is not restrained by the overall stoichiometry and naturally predominates at the stoichiometric concentration. It is recommended that the model be applied only to droplet diameters above about 20/rm and equivalence ratios less than about one. 

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