Jin-Yuan Qian

Nature provides efficient strategies for fluid transport and thermal regulation through evolved structural features. This review summarizes recent progress in biomimetic thermal–fluid structures for enhancing fluid flow and heat transfer, with emphasis on the links among biological inspiration, engineering geometry, transport mechanisms, and application performance. Representative designs are classified into tree-like branching and fractal networks, compact hexagonal layouts, and bio-inspired curved morphologies, including riblets, grooves, fins, fluctuating channels, and TPMS structures. Their enhancement mechanisms involve flow redistribution, boundary-layer disturbance, secondary-flow and vortex generation, local acceleration, enlarged heat-transfer area, drag reduction, and compact flow organization. Applications using biomimetic structures are assessed in detail, such as in battery thermal management, electronic cooling, etc. The reviewed studies indicate that biomimetic structures can improve temperature uniformity, suppress hotspots, and enhance thermohydraulic performance, but the gains may be accompanied by pressure-drop or pumping-power penalties. Therefore, coupled thermal–hydraulic evaluation is essential for objective comparison. Key challenges of practical usage are identified in mechanism-based design, manufacturability, reliability, etc. This work establishes the guidance for translating biological forms into practical thermal–fluid structures with balanced efficacy.

Dry gas seals (DGSs) are currently the preferred sealing method for high-speed rotating machinery, widely used in the fields of petrochemicals and energy and power. This study analyzes the effect of groove structure and operating parameters (rotary ring speed and inlet pressure) on the performance of the sealing system. The results show that a swallowtail-like groove demonstrates a dual effect of improving film stability and reducing leakage under specific working conditions. Specifically, under the inlet pressure of 4.5852 MPa and rotational speed of 10,380 rpm, the swallowtail-like groove achieves a 1.84% reduction in leakage and a 0.32% increase in opening force compared with a conventional spiral groove. Rotational speed has the greatest impact on the gas film stability of the cluster spiral groove. Increasing inlet pressure enhances the dynamic stabilization of gas film. Dynamic analysis indicates that the opening force demonstrates a linear proportionality with inlet pressure, whereas leakage follows an exponential growth. This work can provide guidance for optimizing the groove structure in dry gas sealing systems.

The hydraulic spool valve is a critical control component in aerospace hydraulic systems. However, complex working environments can cause the valve core to

Valves constitute the largest population of active components in the ‘Defense in Depth’ philosophy of nuclear power plants (NPPs), and their reliability is crucial for nuclear safety. Operational experience and numerous studies indicate that valves remain a critical weak link, yet existing academic reviews are often limited to a single failure mechanism or the operation & maintenance (O&M) phase. To address the lack of a systematic perspective centered on this critical component, this paper constructs a full life-cycle reliability framework, systematically reviewing the current status and progress of NPP valve reliability research from four interrelated pillars: (1) reliability-oriented design and optimization; (2) key failure modes and mechanism analysis; (3) reliability assessment and life prediction; (4) condition monitoring and intelligent O&M. Complementing prior reviews limited to specific phases, this paper utilizes the proposed full life-cycle framework to analyze the profound paradigm shift in NPP valve reliability research—transitioning from static, isolated, physics-dominated analysis toward dynamic, systematic, deep physics-data fusion. We identify four core contradictions hindering this evolution: the conflict between small samples and data-greedy methods, complex physics and simplified models, mechatronic systems and single components, and the black-box nature of models versus the need for explainability. To address these challenges, we provide a forward-looking perspective focused on deepening physics-data fusion, coupling component-level remaining useful life with system-level probabilistic risk assessment, and exploring solutions for model trustworthiness and uncertainty quantification.

With the rapid development of industries, hard sealing ball valves are increasingly adopted in extreme working conditions, especially for the advantage of high sealing performance. However, current research works on ball valves are lack of leakage rate prediction, which is an important issue. In this paper, a typical hard sealing ball valve is selected as the research object. Mathematical equations for sealing pressure are derived on both fixed and floating ball valves. The sealing pressure on the hard sealing side of the ball valve is analyzed, and the accuracy of the theoretical equation is verified. Meanwhile, the relationship between sealing performance factor and sealing pressure is fitted, and a prediction method of hard sealing ball valve is proposed, and also is validated experimentally. Results indicate that the sealing pressure obtained from the theoretical equation is conservative, as the actual pressure on the sealing surface exhibits a U-shaped distribution. The sealing performance factor varies with sealing pressure according to a piecewise function. It increases in the form of a power function when the pressure is less than 110 MPa and decreases in the form of a quadratic function when the pressure is higher than 110 MPa. The R² of the fitting equation is greater than 0.98%. Furthermore, the theoretical predictions are consistent with the experimental results in magnitude, confirming the reliability of the proposed prediction method. When the roughness is below 0.2, further reduction in the roughness has little effect on the sealing performance. Both roughness and sealing pressure should be considered comprehensively to enhance sealing performance. This work can benefit the leakage rate prediction and further study for the sealing performance improvement of hard sealing ball valves.

Directional liquid transport (DLT) is essential for water harvesting, thermal management, and biomedical systems. Temperature-responsive structures offer a promising route for adaptive DLT control. However, fully passive and reversible shape transformation with effective directionality remains challenging. Here, we present a temperature-responsive valve (TRV) that converts thermal stimuli into uni-directional liquid transport via automatic mechanical deformation. The proposed unit is a shape memory alloy (SMA) slice embedded within an elastic tube lined with internal fin arrays. Upon heating, the curvature of SMA slice increases. Thus, the fin array beneath is compressed into an asymmetric configuration that generates driving force for stable uni-directional liquid transport. It operates across a wide wettability range of liquid, and supports modular configurations for multifunctional integration. We introduce key applications including reconfigurable direction switching, multimode mixing, and thermal patterning. The system achieves to transport ~ 3000 µL liquid volume over ~ 66 mm, which outperforms the existing DLT systems of thermal stimuli. These performances originate from augmented Laplace pressure difference, reverse pinning, and asymmetric wetting structure. This work establishes a scalable framework of reconfigurable DLT control, offering new opportunities for intelligent microfluidic systems.

O-type ball valves are common flow devices that are widely used in different industrial applications. A vibration often occurs when fluid flows through O-type ball valves, and it affects the efficiency and reliability of industrial systems. In this paper, the flow-induced vibration of O-type ball valves is investigated through experimental methods. A vibration experimental platform with the function of isolating the external vibration sources is designed. By analyzing the experimental phenomena and vibration signals, the variation law at various valve openings can be distinguished into two typical conditions, non-cavitation and cavitation conditions. The intensity of vibration exhibits a linear correlation with the square root of the pressure differential across the valve under non-cavitation conditions. The intensity of vibration suddenly rises at specific flow velocities under cavitation conditions. The rise in vibration intensity is concentrated in the higher frequency band of 315–8000 Hz. The relationship between the critical flow velocity at which valve vibration suddenly rises and the valve opening is also proposed based on the nonlinear least squares fitting method. The critical fluid velocities at different valve openings can be predicted through this fitted function. These works are good for the design of vibration suppression of O-type ball valves and further research on the mechanism of the coupling effect between cavitation and vibration.