• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1700-1716
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• 1996

The two-dimensional, unsteady, laminar conservation equations for mass, momentum, energy and species transport in the gas phase and mass, momentum and energy in the liquid phase are solved simultaneously in spherical coordinates in order to study heating and vaporization of a droplet entrained in the oscillating flow. The numerical solution gives the velocity and temperature distribution in both gas and liquid phase as a function of time. When the gas flow oscillates around an vaporizing droplet, the liquid flow circulates in the clockwise or counterclockwise direction and the temperature distribution in the liquid phase changes its shapes, depending on the gas fow direction. When the gas flow changes its direction of circulating liquid flow is opposite to the gas flow, forming two vortex circulating in the opposite direction. During the heating period, the difference in the maximum and minimum temperature is large, followed by the almost uniform temperature slightly below the boiling temperature. The mass and heat transfer from the droplet depend on the droplet temperature, droplet diameter and the magnitude of relative velocity, giving the droplet lifetime different from the d$^{2}$-law.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.534-540
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• 1988

A study on the mixing process of fuel with ambient gas is necessary to verify combustion process of a diesel engine, especially the mechanism of its ignition delay. In this study, a single shot of diesel spray was injected through either a constant pressure injection system and bypass type injection system. Measurements were made on the flow characteristics of ambient gas and its time history using a hot wire anemometer and a high speed camera. The gas flow direction was determined by a smoke tracer method. (1) The ambient gas of spray flows away at the stagnation part where static pressure value is positive and flows in at the penetration part of a negative value with the steady entrainment length of 0.7. (2) The steady entertainment velocity around the spray in creases from the nozzle tip to the downstream, has the maximum value at the mixing boundary part, and represents zero at the stagnation boundary part after which the stream flows reversely at the stagnation part.