Particle slip velocities in air jets under atmospheric pressure and soft vacuum conditions

Abstract

AbstractLaser Doppler anemometry (LDA) is used for the measurement of gas and particle velocities in an air jet under atmospheric pressure and soft vacuum conditions. The slip velocity between the particles and the carrier gas at the exit of a particle injection probe is shown to depend on the geometry of the probe tip. With a standard probe tip, the particle velocity lagged behind the gas velocity at the exit of the probe. The addition of a section with a sudden expansion at the downstream end of the probe, results in the rapid drop of the gas velocity at the exit of the probe without a corresponding drop of the particle velocity. The results show that the proposed probe tip configuration can be effectively used to achieve a positive particle slip condition at the exit of the probe, with the particle velocity equal to or higher than that of the carrier gas.