Effect of pressure recovery vanes on the performance of a swirl tube, with emphasis on the flow pattern and separation efficiency

The effect of pressure recovery or rectifying vanes on the performance of reverse- flow swirl tubes has been investigated both by calculation based on velocity measurements and by direct pressure measurements. The calculations show that about 50% of the pressure drop should be recoverable. This result is compared with the literature and is discussed in some detail. The experimental results show that rectifying vanes can recover some of the dynamic pressure in the swirling motion. The deeper the vanes extend into the separation space, the more is recovered. Importantly, however, the separation efficiency is reduced, and a Stk- Eu plot shows that installation of the vanes, at least in the positions tested here, does not improve the overall performance. Visualization also shows that the presence of the rectifying vanes destabilized the vortex, causing the vortex end to occur in the tube separation section, an issue not yet addressed in the literature. It is shown that flow visualizations and CFD simulations indicate a type " 0" vortex breakdown in the gas outlet and that this may explain some of the observed phenomena related to rectifying vanes.