Experimental study on radial evolution of droplets in vertical gas-liquid two-phase annular flow

Abstract

In vertical gas-liquid two-phase annular flow, the radial evolution of droplets in the gas core plays a key role in affecting the characteristic of gas carrying liquids. In this paper, the droplets size and velocity at 11 radial positions were measured with the phase Doppler anemometry and then analyzed based on the recognition method of droplet role to figure out the radial evolution characteristics of droplets flow rate, size, velocity, and momentum. The results show that the droplet quantity flow rate decreases with the entrained droplets moving from the liquid film-gas core interface to the centerline, due to the fact that the droplet coalescence has a greater effect than the droplet breakup. The proportion of small droplets decreases while the proportion of relatively large droplets increases. The overall distribution characteristics of droplet diameter remain unchanged. The overall distribution characteristics of droplet axial velocity, radial velocity, and velocity size remain unchanged, although the droplets undergo the process of axial acceleration and radial deceleration during the radial migration. The distribution of droplet momentum varies greatly in the process of droplet radial migration. The contribution of small droplets to the total droplet momentum gradually decreases, while the contribution of large droplets to the total droplet momentum gradually increases. Although the number of large droplets is small, their contribution to the total droplet momentum cannot be neglected.