Flow Field Characteristics and Separation Performance of a Novel Hydrocyclone for Natural Gas Hydrate under Pulsating Flow

Solid fluidization mining is a promising method for natural gas hydrate. However, this technique involves complex downhole conditions, including pulsating flow resulting from drilling pump operations, which significantly impairs the separation efficiency of hydrocyclones. This study investigates the flow field characteristics and separation performance of both a conventional hydrocyclone separator and a novel hydrocyclone separator specifically designed for pulsating flow conditions. Using computational fluid dynamics with the Reynolds stress model and the Mixture model, simulations are conducted to analyze the velocity field, pressure distribution, phase volume fraction, and separation efficiency under both steady and pulsating flow. Results demonstrate that pulsating flow considerably disrupts the internal flow field of a conventional hydrocyclone separator, leading to a reduced separation efficiency and increased operational instability. In contrast, a novel hydrocyclone separator equipped with a spiral section and a flow-stabilizing cone effectively mitigates these disturbances. It maintains stable distributions of tangential, radial, and axial velocities, minimizes pressure fluctuations, and ensures consistent concentration profiles of hydrate and sand under pulsating conditions. As a result, the novel hydrocyclone separator achieves higher average separation efficiencies for both sand (90.74%) and hydrate (89.98%), with significantly reduced efficiency fluctuations compared with the conventional hydrocyclone separator. This study confirms that the novel hydrocyclone separator robustly handles flow instabilities, delivering an enhanced separation performance and operational reliability. The findings provide valuable insights for the optimization of downhole separation equipment in natural gas hydrate mining.