Numerical Analysis and Experimental Investigation of the Effect of Inlet Angle on Hydrocyclone Classification Performance

Hydrocyclones, which are efficient solid-liquid separation devices widely used in coal separation, petroleum purification, and other industries, have classification performance directly governing industrial separation efficiency. As a multiphase flow transport channel, the inlet critically influences internal flow field characteristics and particle motion, yet the mechanism by which the inlet angle regulates classification performance remains unclear. To address this gap, this study combined numerical simulation and experimental verification to systematically investigate the effects of different inlet angles. Numerical simulations acquired pressure, velocity, turbulence fields, and air core characteristics, while a closed-loop test rig with quartz sand validated numerical reliability. Quartz sand with density 2650 kg/m³, particle size distribution 0~60μm, and slurry concentration 5%-10% were used in experiments. Key findings show positive inlet angles effectively enhanced tangential velocity, reduced turbulence intensity and proportions of short-circuit/circulating flow, optimized air core stability, and minimized its classification space occupation. In terms of classification performance, positive angles decreased cut size by ≥6.36µm, increased the sharpness index by up to 0.36, and significantly improved accuracy. Compared with the -15° inlet structure, the 15° inlet reduced underflow fine particle content by 13.19 percentage points, lowered pressure drop by 4.7KPa, and boosted quality/quantity efficiency by 8.5 and 6.52 percentage points, respectively. This work clarifies the inlet angle's regulatory mechanism, providing theoretical and data support for high-efficiency hydrocyclone design. Positive inlet angles reduce underflow fine particle entrainment and operational energy consumption, improving the economy and stability of industrial separation