Search Results (223)

In cold and humid environments in high-latitude, high-altitude, and offshore regions, ice accretion sometimes occurs on airfoil blade surfaces, such as those of wind turbines. Therefore, a potential hazard exists for the equipment. For this reason, the aerodynamic characteristics of the airfoil blade degrade and power generation decreases. In the present study, the icing characteristics of airfoils in cold and foggy environments were investigated. A novel icing wind tunnel with a low LWC of 0.3 g/m³ and a small MVD of 10 μm was designed and built. An airfoil sample with the aerodynamic profile of NACA 0018 was selected, and the effects of the airfoil material and the temperature on the icing area, the thickness of ice, and the coverage scope of ice were tested and analyzed. The experimental results showed that the temperature had a more significant effect on the icing characteristics in comparison with the airfoil material. At the medium temperature, −7 °C in the present study, the icing area, the thickness of ice, and coverage scope all reached their maximum value. Specifically, the maximum cross-sectional icing areas (CIAs) on the aluminum airfoil at −4 °C, −7 °C, and −10 °C for 60 min were 35.088 mm², 66.357 mm^2, and 51.538 mm², respectively, and those on the FRP airfoil were 36.204 mm², 70.352 mm², and 47.814 mm², respectively. The FRP airfoil had a larger icing area and thickness of ice. In contrast, the aluminum airfoil had a larger coverage scope of ice, which was −0.10~0.15. In addition, the aerodynamic performance of the iced airfoil, including C_d and C_m, was also obtained through CFD. The research findings provided a foundation for further exploring the atmospheric icing of wind turbines and other structures with airfoil profiles. Full article

The reciprocating cutterbar is evolving from a conventional harvesting mechanism into an intelligent end-effector for crop harvesting, mechanical weeding, and selective cutting. However, plant anisotropy, moisture-dependent fracture, root-soil constraints, vibration, and wear still hinder low-energy cutting, long service life, and robust control. This review integrates harvesting and mechanical weeding within a unified analysis of reciprocating cutterbar technologies. It first links plant tissue structure and dynamic fracture to blade penetration, fiber stretching, crack propagation, and energy dissipation. It then examines how cutting speed, sliding-cut angle, blade clearance, and root-soil anchorage jointly affect performance. Advanced testing, response surface methodology, discrete element method, finite element method, and multiphysics simulations are compared for failure analysis, parameter optimization, and contact modeling. The review further assesses bionic blade design, surface strengthening, composite coatings, novel transmissions, multisource perception, and adaptive control. Key barriers include inconsistent plant-mechanics datasets, computationally intensive models, limited field robustness, and conflicts among performance objectives. We therefore identify digital twins, modular electric cutterbars, and closed-loop control as priorities for translating mechanistic insight into reliable field performance. Full article

For unshrouded turbine blades, the high-speed tip clearance leakage flow induced by the pressure gradient on the pressure and suction surface sides significantly increases the thermal load in the turbine blade tip regions. Film cooling technology is an effective measure for reducing the external heat transfer temperature at the blade tips. Novel cooling strategies for the turbine blade tip are introduced to reduce adiabatic wall temperature. Here, the spatial distribution of film cooling effectiveness and the associated flow physics of the rib-slot and trapezoidal-slot tip configurations are investigated numerically and experimentally under transonic conditions. Film cooling effectiveness on the tip is quantified using the pressure-sensitive paint technique. Density ratios of 1.5 and 2.0 are considered, with tip clearances set at 0.7% and 1.5% of the blade height and the cascade exit Mach number set at 1.05. Both the trapezoidal-slot and rib-slot tip cooling approaches are capable of establishing complete film coverage over the tip surface. The rib-slot configuration delivers markedly higher effectiveness values over the mid-chord and trailing-edge regions relative to the trapezoidal-slot design. Conversely, the trapezoidal-slot scheme improves tip aerodynamic performance compared with the rib-slot arrangement, with the benefit being most pronounced in the larger clearance setting. Full article

With the rapid development of offshore engineering, marine cranes are widely deployed in critical maritime operations, such as the precision installation of wind turbine blades. However, their highly coupled three-dimensional spatial dynamics, uncertain payload mass, and susceptibility to severe external sea wave disturbances pose significant challenges in achieving fast, accurate payload transportation and rapid anti-swing performance. To address these issues, this paper proposes a novel energy-based intelligent coupling control strategy utilizing fuzzy logic and adaptive gravity compensation for 5-DOF (5-Degrees of Freedom) marine cranes. Firstly, to handle the severe underactuation and facilitate natural energy dissipation, a novel set of error coupling variables is constructed, organically linking the actuated crane structure with the unactuated payload swing dynamics. Then, an adaptive gravity compensation mechanism is designed to dynamically estimate the uncertain payload mass in real time, eliminating the need for precise prior mathematical models. Subsequently, to counteract complex external environmental disturbances and unmodeled internal dynamics, a targeted fuzzy observer is developed based on the universal approximation theorem, providing robust, real-time perturbation compensation. The sufficient conditions for the asymptotic stability of the closed-loop system are rigorously proven based on the Lyapunov method and LaSalle’s invariance principle. Finally, extensive comparative simulations are conducted, demonstrating that the proposed method significantly improves the operational accuracy, anti-swing capability, and safety of marine cranes under varying load conditions and persistent wave disturbances. Full article

This paper presents a comprehensive three-dimensional numerical investigation of a novel vertical-axis wind turbine (VAWT) characterised by a unique aerodynamic profile and a passive blade-pitch control mechanism. Unlike conventional fixed-geometry designs, the proposed turbine utilizes rectangular blades mounted on horizontal axes via articulated bearings, allowing them to rotate freely up to 90 degrees, constrained by a vertical pin-and-belt system. This configuration ensures that blades on the power-stroke side hit the vertical stopper to capture maximum wind energy, while blades on the return-stroke side open up to 90 degrees to significantly reduce aerodynamic drag. This dynamic adjustment enables the turbine to operate efficiently in low-wind conditions (3–5 m/s) while maintaining enhanced torque stability. To ensure numerical reliability, a rigorous grid independence study was performed, and the computational domain was configured to eliminate wall interference effects. The aerodynamic performance was analyzed using COMSOL Multiphysics v6.2 by solving the Reynolds-averaged Navier–Stokes (RANS) equations. Four turbulence models—SST, k–ε, k–ω, and RNG—were evaluated, with the SST model demonstrating the highest fidelity in capturing flow separation and wake structures under adverse pressure gradients. This study establishes the turbine’s performance benchmarks, including the power coefficient (C_p) versus tip speed ratio (TSR) curves. The numerical results were validated against laboratory experimental data, with excellent agreement (relative error < 5%). The findings identify the optimal geometric parameters and tangential velocity distributions that distinguish this configuration (Patent FAP 20240465) from traditional VAWTs. Finally, the successful implementation of a 2 kW prototype confirms the model’s accuracy and highlights the turbine’s potential as a stable and efficient solution for sustainable urban energy harvesting. Full article

Canned motor pumps are widely utilized due to their distinct advantage of a completely leakage-free structure. Among them, an integrated impeller–rotor configuration is employed in the axial-flux canned motor pump, resulting in a shorter axial length and higher power density. This novel configuration allows for easy integration into space-constrained systems, such as electric vehicles, aerospace applications, and liquid-cooled servers. However, research on the internal flow characteristics of these pumps remains scarce. To address this gap, the present study investigates the internal flow across various flow rates. Numerical simulations are validated against experimental data. The average error remains below 2%. The pump achieves a peak efficiency of 68.6% at the design condition, but experiences efficiency drops of 15.0 and 25.2 percentage points under 0.5Q_d and 1.5Q_d, respectively. Results demonstrate that flow rates significantly govern internal characteristics. These include pressure, velocity, and entropy distributions, along with vortex structures and pressure fluctuations. Notably, operating at off-design conditions can intensify the internal pressure fluctuations by up to a factor of 29.4. Entropy analysis identifies major losses on blade suction sides and diffusers. These findings provide crucial hydrodynamic guidelines for low-noise thermal management systems in electric vehicles and ensuring high-reliability cooling loops in aerospace and liquid-cooled servers. Full article

A fundamental aspect in the design of modern utility-scale wind turbines is predicting the vibrational response of their blades when excited by gust pulses of various amplitudes and frequencies in atmospheric flow. Improved designs based on accurate blade-response predictions can prevent extreme oscillations, reduce fatigue stress, and extend turbine’s operational life. In previously published works, the authors introduced and applied a novel technique that provided an energy-based Reduced-Order Characterization (ROC) for the oscillatory response of wind turbine rotors, when excited by wind gust pulses with different combinations of timespan and amplitude under various operational conditions. Those studies established the universal nature of the ROC by expressing the turbine aeroelastic response as a vibrational Stability Map, plotted in terms of non-dimensional quantities, which could be applied to turbines of any size that share a similar blade construction. In the present paper, the authors will expand the ROC technique beyond the scope of their previously published studies, to analyze the Multi-Modal Response observed in regions located at the external boundaries of the stable zones of the Stability Map. This will provide valuable information about rotor stability behavior in extreme turbine operational conditions which were previously unexplored. Full article

Volume phase holographic gratings (VPHGs) are high-performance dispersive elements characterized by high diffraction efficiency and low noise. When used as dispersive components in imaging spectrometers for CO₂ detection, they can significantly enhance instrument performance, detection capability, and measurement accuracy. However, for short-wave infrared (SWIR) applications requiring high dispersion and operational efficiency, traditional design approaches struggle to effectively balance the trade-offs among multidimensional diffraction performance metrics, resulting in low optimization efficiency. Furthermore, as spectrometers require dispersive elements, established fabrication methods lack robust methodologies for producing large-area VPHGs. To address these gaps, we developed both a design approach and a fabrication process for VPH gratings tailored to CO₂ detection. On the design front, we propose a novel method that integrates a multi-objective simulated annealing optimization algorithm with Kogelnik’s coupled-wave theory. The optimized gratings achieve diffraction efficiencies of 95.35% (TE polarization) and 82.21% (TM polarization) across the target spectral range, with polarization sensitivity maintained below 6.57%. For fabrication, we developed holographic plate fabrication via a blade-coating technique coupled with an optimized aging protocol. A medium-to-large aperture holographic recording and exposure system with a wavefront error better than λ/25 RMS was developed. Post-processing conditions were systematically optimized based on experimental diffraction efficiency measurements, enabling the successful fabrication of VPHGs. It is explicitly noted that the experimental validation of the fabricated VPHGs is limited to the 1.620–1.630 μm wavelength range, while the full target design range of 1.620–1.650 μm has not been experimentally verified in this work. This work provides a valuable reference for the selection of dispersive elements for next-generation CO₂ detection satellites. The designed gratings fully meet application requirements, while the established fabrication process lays a solid foundation for the production of high-performance VPHGs. Full article

Blade tip clearance (BTC) is a critical parameter for the thrust, fuel consumption, and operational safety of aero-engines, and its accurate monitorinfg is of significant engineering importance. Traditional eddy current sensors (ECS) in BTC measurement often employ wound coil structures, which suffer from issues such as poor consistency and limited geometric shapes, restricting further optimization of electromagnetic performance. This paper proposes a novel ECS based on ceramic-integrated printed coils. The ECS uses screen printing technology to directly print metal coils onto ceramic substrates and integrate them into a single unit, allowing the coils to be designed with high precision into any topology structure, with high consistency, structural stability, and high temperature tolerance. Performance studies indicate that the sensor can be manufactured with an accuracy of 0.2 mm or better, and the sensor with a line width and spacing of 0.2 mm performed the best in the test. Not only does it exhibit the best electromagnetic performance at room temperature, but it also shows an electromagnetic performance variation of less than 1% after a 24 h aging test at 800 °C. Additionally, it provides stable peak-to-peak and periodic responses to changes in BTC within the range of 0 to 600 rpm for the fan motor. This study provides a promising method for accurate and stable BTC measurement at high temperatures. Full article

The Archimedes Spiral Wind Turbine (ASWT) is a novel horizontal axis wind turbine for urban low-wind-speed applications. To improve the wind energy capture efficiency of the ASWT, this study adopted a multivariable global optimization strategy. A differential evolution–Kriging surrogate model method was employed for blade structural optimization. The blade geometry was parametrically modeled, and three design variables were selected: spiral pitch, opening angle, and spiral rotation number (SRN). Latin hypercube sampling was used to generate sample points in the design space. The power coefficients (C_p) of all design samples were calculated by Computational Fluid Dynamics (CFD) simulations. A Kriging surrogate model was constructed to map the nonlinear relationship between the design variables and C_p. The optimal blade geometry was obtained by solving the surrogate model with differential evolution (DE) and validated by CFD. The results showed that at the design condition of a wind speed of 8 m/s and a tip speed ratio (TSR) of 1.875, the relative error between Kriging model predictions and CFD simulations was only 0.27%. The optimized blade achieved a C_p of 0.3085, representing a 4.78% improvement over the best sample blade, with both achieving their peak power coefficients at TSR = 1.875. Full article

Geometric discontinuities in aero-engine turbine blades generate multiple stress concentrations along the airfoil, rendering life prediction exceptionally challenging. While conventional skeletal point method (SPM) offers reasonable accuracy in predicting creep-fatigue-interaction (CFI) life for simple structural specimens, they prove inadequate for geometries with poor symmetry. This study introduces a novel two-dimensional skeletal point method (2D SPM) to analyze stress evolution characteristics, identify representative stresses, and predict CFI life in complex structures. Leveraging the film-cooling hole (FCH) features of a representative turbine blade, three perforated plate specimens were designed, manufactured, and subjected to CFI testing. Failure analysis confirmed crack initiation at hole-edge stress concentration zones, followed by inward propagation. Specimen fracture surfaces exhibited predominantly ductile dimpling features, with multi-origin fatigue characteristics observed only near hole-edges, collectively indicating creep-damage-dominated failure mechanisms. Five life prediction methodologies were comparatively evaluated. The results demonstrate that the 2D-SPM achieved the highest accuracy (all predictions within twofold scatter bands), followed by the conventional SPM (also within twofold scatter bands). The nominal stress method showed moderate accuracy (within fivefold scatter bands), while both hot point method and TCD methods proved unsuitable for creep-fatigue scenarios with significant stress evolution. Full article

The electrification of the automotive industry and the lightweighting of aerospace equipment demand high-efficiency centrifugal pumps for compact spaces. A novel centrifugal pump incorporates an integrated impeller-motor rotor design, achieving a more compact footprint and higher power density. However, research is scarce on the radial clearance between the rotor and casing. This study presents a comprehensive investigation of the internal flow dynamics, combining numerical simulations with experimental validation. A significant reduction in fluctuation amplitude for pump efficiency, head coefficient, and frictional loss rate occurs when the clearance ranges from 1.0 to 1.5 mm. Within clearances of 0.75 to 1.5 mm, complex vortex systems emerge in the radial clearance, inducing diverse circumferential high-speed zones. Pressure fluctuations within the radial clearance are predominantly governed by the blade passing frequency. At a clearance of 1.5 mm, the rotational harmonic amplitude at monitoring points exceeds the blade passing frequency amplitude by a factor of 1.9, while the average pressure fluctuation intensity at other points increases significantly by 36.9%. An optimal clearance of 1.25 mm achieves a balance between flow characteristics and energy consumption. This research provides practical insights for optimizing pump energy performance and operational stability. Full article

Since the inception of utility-scale wind turbines, there has been a continual increase in the size of the devices used. One drawback of turbine size increase is that the weight of the rotor blades has grown dramatically. Technological advancements have allowed for the creation of light blades to overcome this issue. These lighter rotors are also less stiff than their predecessors and prone to experiencing aeroelastic vibrations that can lead to fatigue damage. Aerodynamic damping occurring during blade vibration has the potential to mitigate those oscillations; thus, understanding its underlying physics provides an extremely useful tool for future blade design. In a series of previous publications, the authors presented a novel reduced-order characterization technique for the oscillatory response of wind turbines, which allows for the analysis of rotor vibrations when excited by wind gust pulses. In this paper, the authors will apply the same gust pulse technique to analyze the physics of blade’s aerodynamic damping, identifying two physical mechanisms. The first acts either as a damper, or as an energy feeder, depending on operational conditions. The second operates in a purely dissipative manner. Results of numerical experiments on several operational scenarios illustrating these behavioral responses will be presented and discussed. Full article

A review of morphing actuation systems in relation to rotary-wing aerial platforms is presented. The research highlights an inadequate maturation of rotary actuation systems, characterised by a scarcity of (1) comprehensive full-scale experimental research relative to non-rotary (fixed-wing) systems, (2) techniques used for rotary actuation systems and (3) implementation of full-chord morphing systems, with existing research only utilising partial-chord actuation techniques. Additionally, another notable shortcoming is presented to be the lack of comprehensive proportional investigation in the proposed five-step development process for rotary actuation designs. A comprehensive critical review is offered, covering the following challenges of progressing through this development process for rotary actuation systems from conceptual design to production: (1) numerical and computational studies, (2) small-scale wind-tunnel testing, (3) full-scale wind-tunnel testing, (4) demonstrator, and ultimately (5) fabrication for industrial implementation. The review examines several existing rotary actuation systems, including (but not limited to) leading-edge, trailing-edge and Gurney flaps; active twist; chord extension; variable span and camber systems. Comparisons are made between rotary morphing actuation systems and their non-morphing counterparts, highlighting the distinct difficulties encountered by rotary-wing systems due to the more complex and challenging operational conditions found in rotorcraft. The review reveals that a significant portion of existing research on rotary-wing systems has focused only on early-stage development, including computational modelling and sub-scale wind-tunnel experiments, underscoring the necessity for more comprehensive full-scale testing and prototype evaluation given that only a small number of studies have progressed to full-scale wind-tunnel testing or actual prototype evaluation, with only one example identified as having been tested on a production helicopter. In addition, a comparative Technology Readiness Level (TRL) assessment is presented for both rotary-wing and fixed-wing morphing actuation systems, enabling a structured evaluation of relative technology maturity, experimental validation depth, and proximity to operational implementation. Building upon this assessment, a morphing Actuation Concept-Transfer Feasibility (ACTF) study is also provided, examining the potential for adapting mature fixed-wing morphing actuation technologies for application in rotary-wing environments, while identifying the key structural, aerodynamic, and operational constraints that currently limit direct technology transfer. This study addresses and proposes opportunities for a novel rotary actuation system design and concludes by suggesting the potential for future research on more effectual systems to include full-chord configuration over larger spanwise blade footprints with innovative actuation mechanisms that could be utilised and progressed through all development stages from numerical studies to full-scale fabrication. Full article

Conventional borescopes are limited by inadequate mechanical flexibility, poor environmental adaptability and reachability, and heavy reliance on operator expertise during aero-engine inspections, making it difficult to meet the demands for efficient and dependable in situ nondestructive evaluation (NDE). This paper presents a novel telescopic continuum robot mechanism with an ultra-high aspect ratio (63.75:1) and three constant-curvature segments, achieving a synergistic design between the robot’s body structure and the long-stroke linear actuator of its central backbone to realize ultra-high-aspect-ratio configurations. This design improves the robot’s ability to access complex and confined internal spaces within aero-engines, thereby reducing inspection blind spots. Furthermore, a configuration-space control strategy integrating kinematic decoupling and driving tendon tension compensation is proposed. This strategy addresses the issues of multi-segment actuation coupling and tendon slack, ensuring the motion control performance for in situ aero-engine blade inspection. The feasibility of the mechanism design was validated through an experimental simulation platform incorporating both turbine blade and compressor blade scenarios. This work offers a new solution for in situ NDE in aero-engines by synergistically integrating an innovative ultra-high-aspect-ratio telescopic mechanism with a dedicated configuration-space controller that addresses multi-segment coupling and tendon slack. Full article