Experimental And Numerical Study On The Mechanism Of The Reducing Pressure Drop Stick In Cyclones

Experiments have shown that a stick called a Repds (Reducing Pressure Drop Stick) can largely reduce a cyclone's energy loss. The new drag-reduction technique has promoted the study on the reduction of the pressure drop in industry cyclones. Experimental and numerical studies on the mechanism of the Repds in cyclones were carried out so that the drag-reduction method can be optimized in the engineering applications. It's a three-dimensional (3D) strong swirl turbulent multiphase flow in cyclones, which makes much trouble for the experimental, theoretical and numerical studies. Until now, experiments are still the main research methods while the theories are semiempirical and based on the substantial experiments. The numerical study with computational fluid dynamics (CFD) has been developed just in recent 20 years. In this paper, an advanced measurement technique—particle image velocimetry (PIV) was performed to obtain the instantaneous two-dimensional velocity distributions at some sections in the cyclone. And a numerical result was simulated by FLUENT with the Reynolds stress model (RSM).From the instantaneous velocities measured in the experiment with PIV, some turbulent characteristics were computed. The effect of the Repds on the mean velocity distributions presented the same manners of the previous study results. The effect of the Repds on the turbulent characteristics was also analyzed.The three-dimensional velocity fields in cyclones with and without Repds were simulated using FLUENT with the RSM. The simulation results were compared with two sets of experimental results. The RSM was proved available to simulate strong swirl turbulent flows. Some turbulent characteristics were studied in the cyclone flows with and without the Repds to find the further mechanism of the drag reduction by the Repds.Combining the experimental and numerical results, we conclude that there exist two factors of the drag reduction by the Repds. One is the behavior of decreasing swirl by the Repds, which changes the swirl kinetic energy into pressure energy and axial energy. The other is the action of weakening turbulent intensity by the Repds, which reduces the energy dissipation of the cyclone flows. The performance of the two factors on the cyclone flows together results in the changes of the turbulent flow structures and consequently induces the large reduction of the energy loss.