Study on flow pattern and separation performance of air-water swirl-vane separator

Two-phase mixture has a complicated separating process inside a swirl-vane separator which plays an important role in assuring a low wetness of the steam to turbine. To understand the flow pattern inside the swirl-vane separator and analyze the separation performance, a simplified swirl-vane steam separator made of transparent acrylic resin is studied by experiment in which the mixture of air and water is used as the working fluids. Experimental results reveal that the separation efficiency of the separator strongly depends on the flow pattern and the water velocity. The separation efficiency in the annular flow is higher than that of the mist flow and the churn flow. The pressure drop is mainly affected by the air flow rate and the water droplet diameter. Furthermore, a numerical model assuming water as sphere droplets and neglecting its deformation is developed to simulate the separator with Euler two-phase model and RSM turbulence model. It is founded that although the separation efficiency is not sensitive to the size of the big water droplets, it is affected significantly by the micro scale water droplets. By assuming that 94% water droplet equals the Sauter mean diameter and the other 6% is 0.4 times of the Sauter mean diameter, the separation efficiency predicted agrees well with the experimental results for the studied case.