TR-PIV and CNN-based analysis of liquid–liquid two-phase flow in a centrifugal pump impeller
Resumo
Centrifugal pumps are widely used in engineering applications, consuming a considerable amount of energy across the globe. However, in many cases they operate under off-design conditions, such as multiphase flows, implying in an even higher energy consumption. A prominent example is the mixture of water and viscous oil, where the phases may exhibit a dispersed flow pattern depending on superficial velocities. Understanding the flow dynamics within the impeller during two-phase liquid–liquid operation is crucial for grasping the mechanisms underlying energy dissipation and pump performance. In this work, we investigate experimentally oil–water flows in dispersed regime within a centrifugal pump impeller, and propose a framework for automatically identifying the dispersed phase and measuring the velocity field of the continuous phase. For that, we carried out time-resolved particle image velocimetry (TR-PIV) in a transparent pump operating under two-phase flow conditions. An image processing technique based on deep learning was developed to dynamically mask oil droplets (dispersed phase) and distinguish them from water-seeded particles (continuous phase) in the raw TR-PIV data. Additionally, a method to evaluate the phase-ensemble average velocity was designed and implemented. The results revealed that neglecting dynamic masking in the TR-PIV images caused an inversion of velocity values between the pressure and suction blades, driven by the accumulation of oil droplets in recirculation zones near the suction blade. This result highlights the importance of accurately tracking the dispersed phase. Our findings indicate higher turbulent kinetic energy (TKE) values at lower flow rates when the dispersed phase consists of larger oil droplets. These findings expand our understanding of multiphase flows in centrifugal pumps, which can be proven useful for validating numerical simulations, proposing new mathematical models, and contributing to the design of improved and energy-saving impellers.
Autores
William D.P. Fonseca, Rafael F.L. Cerqueira, Rodolfo M. Perissinotto, William Monte Verde, Marcelo S. Castro, Erick M. Franklin.
