Characteristics of particle size and velocity of droplets of coal water slurry subjected to air-blast electrostatic atomization using a phase Doppler particle analyzer

Abstract

Coal water slurry (CWS) is a low-pollution, high-efficiency, coal-based fluid fuel that can be substituted for oil, and can be produced by using about 65% coal, 34% water, and 1% chemical additives through physical processing: it is transported via pipelines. It changes the traditional combustion mode of coal, showing superiority of environmental protection and energy conservation. To explore methods of improving the atomization quality of CWS with a high viscosity, the electrostatic atomization technology was applied for atomization of CWS: a test-bed for electrostatic atomization of CWS was established by using induction charging based on a ring electrode. By employing a phase Doppler particle analyzer (PDPA), the change of particle size distribution of CWS within the atomized core region under the effect of different intensities of electrostatic fields was acquired. Moreover, the differences in gas-liquid phases in terms of velocities and intensities of turbulent fluctuation in flow field were obtained. During the experiment, it can be seen that, when CWS droplets were in an electrostatic field with an intensity of greater than 15 kV, the secondary atomization of charged droplets was significant. The particle size of droplets decreased and they became increasingly uniform; the velocity difference in gas and liquid phases increased with growing intensity of the electrostatic field. The axial turbulence intensity was M-shaped in cross-section while radial turbulence intensity appeared as a shallow ω shape in cross-section. With increasing electrostatic field intensity, the turbulence intensity of the two phases increased while their difference gradually decreased. The experimental result showed that electrostatic atomization technology can improve the atomization performance of CWS to some extent, having potential significance in engineering application.