Numerical Simulation for Structural Optimization and Cuttings Transport Analysis of a Multistage Vortex Cuttings Cleaner

Summary Traditional cuttings cleaning methods exhibit limited effectiveness in extended-reach sections. The self-rotating vortex cuttings cleaner (VCC) employs turbo-mechanical principles to efficiently convert the hydraulic energy of drilling fluid into mechanical power for driving its rotating components, demonstrating significant advantages under restricted drillstring rotation. To further enhance the performance of the VCC, we designed and optimized a novel multistage VCC, establishing a comprehensive analytical model integrating structural parameters, output performance, and cuttings transport efficiency based on a six-degree-of-freedom (6-DOF) hydrodynamic model and a computational fluid dynamics-discrete element method (CFD-DEM) two-way coupled approach. The results indicate that an eight-stage turbo configuration was determined as the optimal design for the VCC, achieving substantial performance improvements over single-stage counterparts under identical operating conditions, with balanced consideration of output performance, hydraulic pressure drop, and efficiency. A drilling fluid flow rate of 30 L/s is recommended as the optimal operating point, balancing hydraulic efficiency (66.09%) and borehole cleaning effectiveness. The cleaning efficiency demonstrates a significant nonmonotonic dependence on particle size, while also being significantly influenced by cuttings morphology. Through systematic parametric analysis and mechanistic investigation, this study provides critical theoretical foundations and operational guidelines for the optimized design and field application of advanced VCC systems.