The Centerline Pressure and Cavity Shape of Horizontal Plane Choked Vapor Jets With Low Condensation Potential

Abstract

A study of plane, underexpanded, condensing vapor jets was undertaken using flash photography and a ventilated pressure probe. This study examined horizontal jets with much lower condensation driving potentials than have been previously studied. Photographic measurements of jet expansion angles, spread angles, cavity lengths, and cavity shapes were recorded and compared with numerical predictions using a parabolic, locally homogeneous flow model that had been modified to incorporate entrainment and condensation effects. When rendered dimensionless by the nozzle width rather than diameter, the plane condensation length agreed well with previously published round jet correlations for higher condensation driving potentials. At lower condensation driving potentials, the jets began to disperse, showing behavior similar to submerged air and energetic reacting vapor jets. Numerical predictions of condensation length were in good agreement over the entire range of measurement. Numerical predictions of vapor cavity shape were in reasonable agreement at higher condensation potentials but underpredicted the width of the vapor cavity at lower potentials. Pressure measurements showed the existence of periodic expansion/compression cells associated with underexpanded noncondensing gas jets. When these measurements were compared with similar measurements of air jets into quiescent water baths, the lengths of the initial steam vapor expansion/compression cells were substantially greater than those of the air jets, and the degree of pressure recovery over the cell length was substantially less.