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Penetration and breakup characteristics of a discrete liquid jet injected into a high-velocity cross flowing airstream were investigated as a basis of plain-jet airblast atomizer design. The main variables covered in this phase were, airstream velocity (from about 35 to 150 m/s), liquid jet velocity (from about 5 to 25 m/s) and injection orifice diameter (from about 0.5 to 2.5 mm). The tests were conducted under conditions of normal atmospheric pressure and temperature using still photography for penetration profile and a laser light scattering technique for mean dropsize determination. The experimental penetration data is shown to agree, reasonably accurately, with a relatively simple model developed in the paper. The analysis of the experimental breakup data reveals the airstream velocity as exercising the strongest influence upon Sauter Mean Diameter.

Penetration and break-up characteristics of a discrete liquid jet injected into a high velocity cross flowing airstream were examined as a basis of plain-jet airblast atomizer design. The first results of this program, detailed in ( 4 ), covered the effects of liquid between two high velocity airstreams (see ( 1 )). Much interest has grown, in recent times, however, in the plain-jet airblast atomizer, as it offers a system of comparable performance and yet is much simpler and cheaper relative to the pre-filming type (see ( 2 )and (3)). In the plain-jet arrangement the fuel is not prefilmed, but instead discharged in the form of several

An experimental and theoretical study is reported of the ignition of a cold, ducted supersonic flow of premixed ethylene and air by means of a coaxial pilot flame. The boundary between conditions leading to ignition and conditions leading to quenching of the flame has been investigated experimentally, and compared with predictions from a computer model of the turbulent combustion process. Comparison has also been made with a simple ignition analysis based on a ratio of characteristic chemical and mixing length scales. Satisfactory agreement has been found between the experimental data and results of both theoretical studies. Nomenclature C p -specific heat D = pilot diameter D crit = minimum D to obtain ignition E = activation energy F = pre-exponential factor [Eq.(2)] / -distance to initiate reaction l m = minimum value of / L = potential core length m ox = oxidizer mass fraction w fu = fuel mass fraction P = static pressure R = gas constant T = static temperature T 0 = total temperature U = velocity X = axial distance from nozzle exit (/) -stoichiometric ratio, fuel-to-air p = mole fraction of combustible T. = ignition delay time i h -heat release time T = characteristic reaction time Subscripts m -minimum value 1 = conditions in cold combustible flow 2 = conditions in hot jet

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