Mechanism of radial fluid force suppression in side groove control valve spools

Control valves are key components of intelligent water distributors and are widely deployed in water-injection wells to implement enhanced oil recovery. Owing to the confined downhole space, these valves typically adopt a side-outlet configuration, which subjects the spool to a pronounced radial flow force (RFF) during the initial opening stage. This force is widely regarded as a primary cause of jamming and frictional failure. To address this issue, a three-dimensional computational fluid dynamics (CFD) model is developed to quantitatively elucidate the formation mechanism of the RFF. Under the prescribed intrinsic flow characteristics, a novel side-grooved spool is proposed, and the mechanism by which this structure suppresses the RFF is elucidated. During the design process, an adaptive radial basis function iterative method is employed to substantially reduce the number of CFD simulations required. A sensitivity analysis of the key end-orifice parameters of the novel spool is carried out. The results show that the pressure on the inner surface of the novel spool effectively counterbalances the pressure on the outer surface, leading to a 92.75% reduction in RFF at 10% valve opening. Across the full stroke, the proposed design reduces the RFF by 61.74% and the axial force by 1.19%. These findings establish an effective spool-design strategy for control valves, enabling suppression of RFF and improved mechanical reliability.