Particle image velocimetry (PIV) experimental investigation of flow structures and dynamics produced by a centripetal turbine

Turbines are capable of producing powerful radial discharge flow, which is why they are widely applied in such fields as chemical, petroleum, pharmaceutical, and so on. The centripetal turbine (CT) represents a new type of optimized turbine structure based on the Rushton turbine (RT). In order to reveal the characteristics of turbulence, centripetal and Rushton turbines were designed. The flow fields of impellers were measured by two-dimensional particle image velocimetry (PIV), in combination with the time-averaged method, phase-resolved method, and proper orthogonal decomposition (POD) method for comparative analysis. Within the measured area, the time-averaged velocity and phase-resolved velocity of the CT is smaller compared to the RT. The numeric range of fluctuation velocity for the two types of impeller is basically the same, but the high-value area of CT is more widely distributed. The swirling strength of the CT is significantly smaller than that of the RT. Besides, the wake structure is significantly weakened, which is conducive to reducing power consumption. The POD triple decomposition method proves effective in decoupling the instantaneous flow field into mean part, coherent part, and turbulence part. In each phase of blade passage, the turbulence part energy of the CT is considerably higher. For different blade passages, the cyclic variation of the CT is more significant. The flow field generated by the CT exhibits stronger eddy diffusion, which is conducive to mixing or reaction. It provides a basis for understanding the turbulent flow characteristics of CTs and impeller optimization.