Analyses of spray and droplet ignition for pure and multicomponent fuels

Thesis/Dissertation · Sat Dec 31 23:00:00 EST 1988

OSTI ID:6453083

Mawid, M A

Droplet and spray ignition phenomena are examined for pure and multicomponent fuels. Many of the important physical and chemical aspects of the ignition process are studied. First the ignition behavior of an isolated droplet is analyzed. The influence of the chemical kinetics is examined using large activation energy asymptotics. Critical and system Damkohler numbers criteria for ignition, are derived and employed to predict the ignition behavior of pure and multicomponent fuel drops. Comparisons between predictions and measurements of the ignition delay times show good quantitative agreements for pure fuel droplets. Detailed transient analysis is performed for multicomponent fuel droplets. Comparisons between the predictions of the ignition Damkohler numbers criteria and the detailed transient analyses exhibit reasonable qualitative agreements. The transient analyses also reveal an extinction phenomenon characterized by the suppression of the mass vaporization rate after ignition occurs. The Damkohler number criterion obtained above is then utilized to determine the ignitability of individual droplets in a spray. A full numerical investigation in a one-dimensional combustion chamber is conducted to obtain the ignition conditions for droplets as well as for external sprays for both pure and multicomponent fuels. The mathematical formulation is based on Eulerian conservation equations for the gas-phase and Lagrangian equations for the dispersed phase. A hybrid Eulerian-Lagrangian numerical scheme has been employed to solve the two-phase systems of equations. The spray ignition behavior has been further investigated through the consideration of axisymmetric spray computations. The detailed numerical study shows good qualitative agreements of the one-dimensional and two-dimensional predictions for

• Research Organization: Illinois Univ., Chicago, IL (USA)
• OSTI ID: 6453083
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
ACTIVATION ENERGY
CHEMICAL REACTION KINETICS
COMBUSTION CHAMBERS
COMBUSTION KINETICS
CONSERVATION LAWS
DROPLETS
ENERGY
FUELS
IGNITION
KINETICS
MATHEMATICAL MODELS
PARTICLES
REACTION KINETICS
SPRAYS