Effects of ALR and configuration ratio on turbulent structures in swirling flows

Abstract

To assess the significant physics associated with the increase of ALR and configuration ratio of the nozzle tip in pneumatic swirling flows, comprehensive observations using a 3-D PDPA system were experimentally carried out. Profiles of mean velocities, turbulence intensities, SMD variations, and correlations between droplet size and turbulence components were quantitatively acquired. As discussed in a previous literature, axisymmetric swirl angle of 30 o is selected for this investigation because of its strong turbulence levels in the flowfield and finer droplet disintegrations. Various ALRs (Air-to-Liquid Mass Ratio) as well as the length-to-diameter ratios of nozzle tip as parameters were chosen. Due to the complex interactions in swirling flows under these variables, this experimental observation will be of fundamental importance to the understanding of turbulence structures. From the observations, it indicated that increasing the ALR causes the spray development to be positively fluctuated on the atomization in both axial and tangential RMS velocities. Also, it can be concluded that the SMD decreases continuously with increase of ALR, substantiating the fact that the fluctuations are inversely proportional to the SMD variation. Meanwhile, the spray behavior is characteristic with a reduction of length-to-diameter ratio; smaller the configuration ratio, the higher the turbulence intensities and smaller SMD variations in the flowfield.

Numerical Simulation on Enhanced Heat Transfer and Flow Characteristics in Direct-Contact Heat Exchanger: A Novel Kenics Static Mixer

“…Due to the formation of vortices and the increase of the heat dissipation rate, the magnitude of turbulent flow has a direct impact on the heat transfer performance. The enhancement of turbulence intensity can strengthen the heat transfer rate [34,35].…”

Effect of Low ALR on the Spray Characteristics of a Pressure-swirl Duplex Nozzle

“…Mansour and Chigier (1990) observed that the SMD of the spray decreased with increasing ALR. Lee (2008) studied the effect of ALR on turbulent structures in swirling flow and reported that increasing the ALR caused a decrease in the SMD and showed better atomization.…”