Wei Peng

Unlike molten or semi-molten ash particles in conventional gas turbines, unmelted solid particles may rebound from the wall, adhere temporarily, or be resuspended after impact. The rotation of turbine rotor blades further affects these processes and adds complexity to particle deposition–resuspension. In this study, a numerical framework in a rotating reference frame was developed to describe film-cooling flow, particle transport, and particle–wall interaction in a representative rotating blade passage. Particle trajectories were calculated using a Lagrangian approach, and the effects of rotating-frame intensity, particle size, and blowing ratio on collision, rebound, and deposition were investigated. The results show that rotation modifies the film-cooling distribution through centrifugal and Coriolis forces, shifting both the cooling flow and the particle-collision region toward the side farther from the rotation axis. Rotation also changes the force balance of adhered particles: aerodynamic and centrifugal effects promote resuspension and suppress stable deposition. For the 3000 rpm-rated helium turbine investigated here, centrifugal-dominated particle resuspension occurs only at speeds substantially above the rated condition. For some higher-speed helium turbines, however, centrifugal force may become the dominant resuspension mechanism. Larger particles collide with the wall more readily but are less likely to remain deposited after impact, so stable deposition may approach zero under centrifugal-dominated high-speed conditions. The effect of blowing ratio is pronounced at low rotation but weakens when rotation-induced resuspension dominates.

Clean hydrogen offers a viable pathway for the substantial decarbonization of hard-to-abate industries. However, current production methods such as renewable-powered electrolysis are challenged by intermittency and high-water consumption, creating a strategic problem at the energy-water nexus. This study introduces a novel nuclear-integrated tri-generation system for the co-production of hydrogen, electricity, and freshwater, thereby enhancing resource synergy and sustainability. The proposed system is based on a 200 MW _th small modular supercritical CO ₂ -cooled fast reactor (SM-SCFR) coupled with high-temperature steam electrolysis and multi-effect distillation (MED) desalination plant. The core innovation is a cascading exergy strategy, where high-temperature heat from reactor drives HTSE, while recovered low-grade waste heat powers MED plant, thereby converting a thermodynamic loss into a productive input. A unified techno-economic framework, based on the power loss factor (PLF) and gain output ratio, evaluates two operational modes: a fully integrated self-sufficient configuration for complete water autonomy and a semi-integrated market-led (SML) configuration that provides desalinated water to meet market demand. Process simulations validate stable integration, yielding a cogeneration efficiency of ∼53% and a favorable PLF. Techno-economic analysis indicates that the SML mode achieves a competitive levelized cost of hydrogen of 2.93 $/kg at a daily production capacity of approximately 550 metric tons. The MED plant, while accounting for only 0.6% of the total capital cost, enables this capability. This work provides a quantitative basis for resilient nuclear-based hydrogen systems that eliminate dependencies on carbon, freshwater, and grid intermittency.

This study utilizes the volume of fluid method and dynamic contact angle model to numerically investigate the wetted area dynamics during droplet impact on square, cylindrical, and triangular pillar arrays. User-defined functions are implemented to real-time monitor wetted areas on the array substrate, pillar side surfaces, and pillar top surfaces with dimensionless parameters like the wetted area ratio (maximum to steady-state wetted area ratio) defined for analysis. The influences of Weber number (We) and static wall contact angle (θ) on wetted area are systematically examined. The results show that in triangular pillar arrays, the pinning effect restricts droplet spreading and retraction, yielding the smallest wetted area ratio. However, the side surface wetted area and steady-state total wetted area are the largest among the arrays studied. In square pillar arrays, the groove-driven effect dominates to produce the largest wetted area. Cylindrical pillar arrays, with smooth surface curvature facilitating flow division, exhibit the optimal bottom surface wetting and relatively rapid droplet retraction. Although the top surface wetted area is minimal, a pinning–depinning–repinning cycle occurs at low θ. The side surface wetted area constitutes the primary component of the total wetted area, accounting for the highest proportion. Micropillar geometry predominantly dictates the fractional distribution of wetted areas, with We and θ exerting weak influence. These findings furnish both quantitative foundations and engineering insights for designing hydrophilic microstructure surfaces.

This paper employs the Volume of Fluid (VOF) method and the Blake dynamic contact angle model to conduct three-dimensional simulations of droplet impact on microstructured arrays with square, cylindrical, and triangular pillars. It investigates the surface flow characteristics following impact, analyzing variations in spreading patterns, spreading factors, and height factors under different Weber numbers (We) and contact angles (θ). Additionally, the study extends the existing model for predicting the maximum spreading factor. The results show that the geometrical configuration of the pillars and We significantly influences the droplet spreading pattern and plays a key role in the formation mechanism and number of secondary droplets. The groove-driven effect exhibits strong geometrical dependence, markedly affecting the jet length, the secondary droplet formation, and the power-law exponent of the maximum spreading factor. In the triangle top angle direction, the pinning effect is pronounced while the groove-driven effect is weaker, resulting in restricted spreading. At low We, the bubble retention influences the evolution of the droplet central height. Variations in the θ primarily affect the retraction process and the formation of secondary droplets, while having a limited impact on the maximum spreading factor. The fitting analysis indicates that the existing power–law correlation between the maximum spreading factor and We remains valid for droplets impacting micropillar arrays, and the extended prediction model shows good agreement with the numerical results.

A kettle reboiler uses the latent heat from the condensation of high-temperature and high-pressure steam in the tube to produce low-pressure saturated steam in the outer shell. The deposition of particles on the tube may change the boiling heat transfer mode from nucleate boiling to natural convection, thereby deteriorating the heat transfer performance of the kettle reboiler. Therefore, it is very important to explore the deposition characteristics of particles in the kettle reboiler. In this study, the RPI boiling model based on the Euler–Euler method is used to analyze the water boiling process on the surface of the tube bundle. The DRW model and critical adhesion velocity model based on the Euler–Lagrangian method are used to calculate the motion of particles during the boiling process and the deposition (rebound) behavior. The results show that the boiling of liquid water enhances the local flow velocity of the fluid, so that the maximum flow velocity appears around the near-wall region. The local high-speed flow disperses the particles in the wake flow of the tube bundle, which inhibits the impact of particles on the wall. As the particle size increases, the wall adhesion and fluid drag on the particles are weakened, and the gravity effect gradually becomes dominant, increasing the residence time of the particles in the tube bundle and the frequency of particle impact on the wall. The particle deposition ratio first decreases and then increases. Ultimately, most particles will be deposited in the low-speed area at the end of the tube bundle.

Nuclear hydrogen production has the advantages of large-scale and low carbon emissions, and is expected to play an active role in the energy transition process. However, the storage and transportation of hydrogen pose potential risks of leakage and diffusion when connected to high-pressure hydrogen storage tanks and pipelines. To address this concern, this study focused on designing three distinct safety improvement schemes tailored for potential hydrogen leakage accidents. These schemes encompassed a passively distributed arrangement of obstacles (Scheme 1), a passively centralized arrangement of obstacles (Scheme 2), and an active fan array blowing (Scheme 3). Numerical simulation methods were applied on extensive spatial scales for relevant calculations. The results revealed that all three schemes effectively reduced the diffusion distance of combustible hydrogen. Specifically, at lower ambient wind speeds, Scheme 1, Scheme 2, and Scheme 3 achieved the shortest diffusion distances of 123 m, 56 m, and 46 m, respectively. Meanwhile, at higher ambient wind speeds, the corresponding distances were 282 m, 100 m, and 79 m. These results collectively offer valuable insights to mitigate the risk of leakage accidents in nuclear hydrogen production systems.