Surface Roughness Influence on the Hydraulic Performance of an Api 610 Bb3 Multistage Centrifugal Pump: An Experimental–cfd Study

Surface roughness affects the hydraulic performance and energy efficiency of API 610 BB3 (between-bearings, axially split, multistage) pumps used in oil, gas, and petrochemical service. We quantify its impact using experiments and computational fluid dynamics (CFD). A four-stage pump was tested at 2900 rpm on a closed-loop rig, and head–flow-rate (Q–Hm) and efficiency–flow-rate (Q–η) characteristics were measured over 30–90 m³/h. Surface roughness of the main hydraulic components was measured using a profilometer and represented in the numerical model by equivalent sand-grain roughness values ks = 0, 25, 50, and 73 µm applied to all wetted walls. Three-dimensional Reynolds-averaged Navier–Stokes (RANS) simulations were performed using the SST k–ω turbulence model with rough-wall functions on a domain including leakage and return channels. The ks = 73 µm case agrees with the measured curves, with the efficiency deviation limited to ~4.1% within 45–90 m³/h, whereas larger deviations occur at 30 m³/h due to part-load operation. Near the best-efficiency region, increasing ks from 0 to 73 µm reduces head by 5.94% and efficiency by 6.62 percentage points. Neglecting roughness overestimates performance; realistic roughness is required for CFD-based prediction of API 610 BB3 pumps.