Particle migration and slurry hydraulic resistance in multi-stage reducer pipes

This study investigates a multi-stage reducer pipe, a pipeline component with a periodically varying crosssection, which facilitates the transport of slurries containing coarse particles. Using a combination of computational fluid dynamics and the discrete element method (CFD-DEM), various reducer models are simulated. A dedicated pipeline test system is employed to evaluate these models under a range of operational conditions. The research assesses the impact of differing contraction ratios, nozzle expansions, and flow velocities on multi-stage reducer pipes. The results indicate that flow dynamics and resistance initially fluctuate across the first three stages but stabilize in subsequent stages. The analysis demonstrates that both section shrinkages and flow rates profoundly affect particle distribution, correlating exponentially with hydraulic resistance. Moderate contraction rates coupled with higher inlet velocities effectively create "energy traps." These configurations result in denser, finer particle streams and diminish wear on the later stages of the reducer nozzle walls. However, the frequent particle impacts on the first stage nozzle's entrance wall highlight the need for improved designs to mitigate impact-induced wear and prevent particle accumulation.