Chemical-kinetics modeling for the ignition of idealized sprays
The problem of spray ignition is used to examine three global reaction mechanisms for the oxidation of hydrocarbon fuels. The reaction schemes are (i) the often-employed one-reaction scheme with linear dependence on fuel and oxygen concentrations, (ii) the one-reaction scheme with nonunity exponents of fuel and oxygen concentrations, and (iii) the two-reaction scheme with the second reaction occurring in both directions. For the ignition results, the ignition of an initially quiescent mixture of air and fuel droplets is considered. The mixture is contained in a constant-volume one-dimensional enclosure with its left end acting as an isothermal ignition source. The ignition delay times and the ignition energies as predicted by the three reaction schemes are compared for a range of fuel-air ratios, pressures, and droplet sizes. The comparison clearly exposes the inadequacies of the reaction scheme with unity exponents which predicts an optimum equivalence ratio of about 10 for the homogeneous as well as the heterogeneous ignition cases. The other two schemes yield an optimum equivalence ratio which is within the range of experimental data. Also the differences between these two schemes are minimal with proper choice of reaction parameters, which can, of course, result in significant simplifications in the modeling of complex combustion problems. A limited comparison with existing experimental data is also given. It is recommended that in the absence of more detailed multistep kinetics, the one-step scheme with nonunity exponents be used in spray combustion modeling.
- Research Organization:
- Dept. of Mechanical Engineering, Univ. of Illinois at Chicago, Chicago, IL 60680
- OSTI ID:
- 6164743
- Journal Information:
- Combust. Flame; (United States), Journal Name: Combust. Flame; (United States) Vol. 69:3; ISSN CBFMA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
025000* -- Petroleum-- Combustion
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DISPERSIONS
DROPLETS
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUEL-AIR RATIO
FUELS
HYDROCARBONS
IGNITION
IGNITION QUALITY
ISOTHERMAL PROCESSES
KINETICS
MIXTURES
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXYGEN
PARTICLES
PETROLEUM
PRESSURE DEPENDENCE
QUANTITY RATIO
REACTION KINETICS
SIZE
SPRAYS
TIME DEPENDENCE