Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143 m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry) was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure, penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume flux distribution also increased.

No abstract

No abstract

Recycling of aggregates separated from industrial wastes becomes more important than ever because of increasing demand of urban redevelopment. The purpose of this study is to investigate the operating principle of a newly developed paste separator equipped with a rotor. We constructed one-dimensional model for the air flow and the particle motion is assumed to be governed by the air drag, centrifugal and gravitational forces. We demonstrate that there are several sections on the air flow route, where particle motions are stationary along the stream-wise direction while rotating in the azimuthal direction, called quasi-stagnant state. It was shown that it plays a key role in separation of particles. We report the critical curve in the parametric space where we can predict separation or non-separation of a given particle size, flow rate and rotor speed.