Search Results (111)

To address the complex pile–soil interaction mechanisms in predicting the compressive bearing capacity of HSCM piles (Helix Stiffened Cement Mixing piles) in marine soft soil regions, this study proposes an intelligent prediction method based on a GA-BPNN (Genetic Algorithm-Optimized Back Propagation Neural Network). A high-quality database comprising 1243 data points was established through finite element numerical simulations. By integrating data preprocessing techniques and the GA-BPNN model, the study systematically investigated the influence of helical blade spacing H₁ and H₂, strength ratio C_ref/S_u, and diameter ratio D_sc/D_H on bearing capacity. The results demonstrate that the GA-BPNN model achieves a prediction accuracy of 99.07%, with a mean squared error (MSE) of 7.20 × 10⁻³ and a coefficient of determination R² of 0.990. SHAP value analysis reveals that the strength ratio and diameter ratio are the dominant factors, exhibiting nonlinear relationships with bearing capacity characterized by saturation effects and threshold-dependent behavior. Laboratory tests further confirm strong correlations between cement–soil strength C_ref, formed pile diameter D_sc, and bearing capacity. The findings indicate that the GA-BPNN model provides an efficient and accurate approach for predicting the bearing capacity of HSCM piles, offering a reliable basis for engineering parameter optimization. Full article

To analyze the wear performance induced by rotor–stator rubbing in an aero-engine sealing structure under authentic operating conditions, a transonic rotor system with double bearing is constructed. This system incorporates the disk, shaft, blades, joint bolts, and auxiliary support structure. The system was evaluated in terms of its critical speed, vibration characteristics, component strength under operational conditions, and response characteristics in abnormal extreme scenarios. A ball screw-type feeding system is employed to achieve precise rotor–stator rubbing during rotation by controlling the coating feed. Additionally, a quartz lamp heating system is used to apply thermal loads to coating specimens, and the appropriate heat insulation and cooling measures are implemented. Furthermore, a high-frequency rubbing force test platform is developed to capture the key characteristics caused by rubbing. The test rig can conduct response tests of the system with rotor–stator rubbing and abrasion tests with tip speeds reaching 425 m/s, feed rates ranging from 2 to 2000 μm/s, and heating temperatures up to 1200 °C. Test debugging has confirmed these specifications and successfully executed rubbing tests, which demonstrate stability throughout the process and provide reliable rubbing force test results. This designed test rig and analysis methodology offers valuable insights for developing high-speed rotating machinery. Full article

This paper details the development of a full turbine model and ensuing aero-servo-elastic analysis of the International Energy Agency’s 15MW Reference Wind Turbine. This model provides the means to obtain realistic turbine performance data, of which normal and tangential blade loads are extracted and applied to a simplified drivetrain model developed expressly to quantify the shaft eccentricities caused by aerodynamic loading, thus determining the impact of aerodynamic loading on the generator structure. During this process, a method to determine main bearing stiffness values is presented, and values for the IEA-15MW-RWT obtained. It was found that wind speeds in the region of turbine cut-out induce shaft eccentricities as high as 56%, and that tangential loading has a significant contribution to shaft eccentricities, increasing deflection at the generator area by as much as 106% at high windspeeds, necessitating its inclusion. During a subsequent generator structure optimisation, the shaft eccentricities caused by the loading scenarios examined in this paper were found to increase the necessary mass of the rotor structure by 40%, to meet the reduced airgap clearance. Full article

The Deep Cement Mixing Integrated Drilling, Mixing, and Jetting (DMJ) technique was innovatively developed by incorporating high-pressure jetting apertures into the mixing blades to enhance the bearing capacity of deep cement-mixed piles. In this study, the bearing characteristics of DMJ pile composite foundations under embankment loading are investigated using numerical simulation. Through comparative simulations involving various pile configurations, the results demonstrate that DMJ pile composite foundations exhibit significantly enhanced settlement control compared to conventional deep mixing piles. Notably, under identical area replacement ratios, the use of DMJ piles reduces total foundation settlement by approximately 30%. Furthermore, the findings indicate that larger pile diameters and smaller spacing are particularly effective in minimizing settlement. In terms of load transfer efficiency, DMJ piles are capable of transmitting embankment loads to depths of up to 15 m, surpassing the 10 m transfer depth observed in conventional pile systems. An analysis of excess pore water pressure further reveals that DMJ piles promote more effective dissipation, highlighting their superior performance in maintaining foundation stability under embankment loading. Full article

The accuracy of the blade pitch angle (BPA) motion in controllable pitch propellers (CPPs) is considered crucial for the efficacy and reliability of marine propulsion systems. The pitch adjustment process of CPPs is highly complex and influenced by various uncertain factors. A parametric kinematic model for the pitch adjustment process for CPPs was established, incorporating the geometric dimensions and material surface friction coefficients caused during workpiece production as uncertainty parameters. The aim was to establish the correspondence between these uncertainty parameters and the BPA of CPPs. A large dataset was generated by batch calling on Adams. Based on the collected dataset, five surrogate models (e.g., deep neural network (DNN), Kriging, support vector regression (SVR), random forest (RF), and polynomial chaos expansion Kriging (PCK)) were constructed to predict the BPA. Among these, the DNN approach demonstrated the highest prediction accuracy. Accordingly, the influence of uncertainties on the BPA was investigated using the DNN model, focusing on variations in the slider width, crank pin diameter, crank disc diameter, piston rod–slider friction coefficient, crank pin–slider friction coefficient, and hub bearing–crank disc friction coefficient. The high-fidelity model established in this study can replace the kinematic model of the CPP pitch adjustment process, significantly improving computational efficiency. The research findings also provide important references for the design optimization of CPPs. Full article

The attenuation of bolt preload is a critical factor leading to bolt fatigue failure, whereas the study of the nonlinear attenuation behavior of preload and its mechanism during installation is an inevitable challenge in engineering practice. The attenuation of the preload of a bolt is mainly related to the stiffness of the bolt body as well as the stiffness of the connected parts. This study aimed to develop an experimental system to analyze the nonlinear attenuation behavior of preload during bolt tightening. First, a simulation system replicating the bolt installation process was constructed in a laboratory setting, incorporating blade and pitch bearing specimens identical to those used in a 10 MW wind turbine, restoring the stiffness coupling characteristics of the “composite-metal bearing” heterogeneous interface at the blade root through a 1:1 full-scale simulation system for the first time. Second, ultrasonic preload measurement equipment was employed to monitor preload variations during the bolt tightening process. Finally, the instantaneous preload decay rate of the wind turbine blade-root bolts and the over-draw coefficient were quantified. Experiments have shown that the preload decay rate of commonly used M36 leaf root bolts is 11–16%. If a more precise value is required, each bolt needs to be calibrated. These findings provide valuable insights for optimizing bolt installation procedures, enabling precise preload control to mitigate fatigue failures caused by abnormal preload attenuation. Full article

To ensure the vibration safety of rotor support systems in modern aeroengines, this study develops a dynamic model of the aeroengine gas generator rotor system and analyzes its complex unbalance response characteristics. Subsequently, it investigates vibration reduction strategies based on these response patterns. This study begins by developing individual dynamic models for the disk–blade system, the circular arc end-teeth connection structure and the squeeze film damper (SFD) support system. These models are then integrated using the differential quadrature finite element method (DQFEM) to create a comprehensive dynamic model of the gas generator rotor system. The unbalance response characteristics of the rotor system are calculated and analyzed, revealing the impact of the unbalance mass distribution and the combined support system characteristics on the unbalance response of the rotor system. Drawing on the obtained unbalance response patterns, the vibration reduction procedures for the rotor support system are explored and experimentally verified. The results demonstrate that the vibration response of the modern aeroengine rotor support system can be reduced by adjusting the unbalance mass distribution, decreasing the bearing stiffness and increasing the bearing damping, thereby enhancing the vibration safety of the rotor system. This study introduces a novel integration of DQFEM with detailed component-level modeling of circular arc end-teeth connections, disk–blade interactions and SFD dynamics. This approach uniquely captures the coupled effects of unbalance distribution and support system characteristics, offering a robust framework for enhancing vibration safety in aeroengine rotor systems. The methodology provides both theoretical insights and practical guidelines for optimizing rotor dynamic performance under unbalance-induced excitations. Full article

The structural integrity of next-generation offshore wind turbines is highly sensitive to inflow variability, yet current standards often simplify wind conditions without capturing their combined effects on dynamic loads. To address this, we analyzed the NREL IEA 15 MW offshore wind turbine using 27 simulation cases strategically selected through Latin Hypercube Sampling (LHS) from a design space of over 14 million combinations. Four key environmental variables—Extreme Wind Speed (30–40 m/s), turbulence intensity (12–16%), Shear Exponent (0.1–0.3), and Flow Inclination Angle (−8° to +8°)—were varied to assess their influence on structural response using BLADED simulations. Results showed that the combined structural moment (Mxyz) ranged from 159,502.5 kNm (minimum) to 189,829.2 kNm (maximum), indicating a 19% increase due to inflow conditions. Maximum-moment case exhibited a 2.6× higher drag coefficient, a 13% rise in pitch bearing moment, and dominant frequency content near 0.175 Hz, closely matching the first tower side-side natural mode (0.17593 Hz), confirming potential resonance. These findings highlight the importance of multidimensional inflow modeling for identifying worst-case load scenarios and establishing a foundation for future load prediction models and support structure optimization. Full article

To address the issues of low shear strength, susceptibility to eccentricity, and alignment difficulties in post-inserted core piles, a new type of steel tube concrete integrated mixing composite pile has been independently developed. This pile type replaces the conventional mixing pile shaft with a larger diameter steel tube equipped with mixing blades. After forming the external annular cement mixing pile, the steel tube is retained, and the hollow core is filled with concrete. To thoroughly explore the vertical compressive bearing characteristics of the steel tube concrete mixing composite pile and clarify its vertical compressive behavior, static load field tests and PLAXIS 3D finite element numerical simulations were conducted on four test piles of different sizes to analyze the vertical bearing performance of the steel tube concrete mixing composite pile. The research results indicate that for a composite pile with a length of 40 m, an outer diameter of 1000 mm, and a steel tube diameter of 273 mm, the ultimate bearing capacity of a single pile is 7200 kN, with the steel tube concrete core contributing approximately 81% of the vertical bearing capacity, while the cement mixing pile contributes around 19%. Based on the characteristic that the maximum axial force is concentrated in the upper half of the pile length, an innovative variable-diameter design with a reduced wall thickness of the steel pipe in the lower part of the pile was proposed. Practical verification has shown that, despite the reduced material usage, the load-bearing capacity remains largely unchanged. This effectively validates the feasibility of the “strong upper part and weak lower part” design concept and provides an effective way to reduce construction costs. Full article

In industrial manufacturing, product quality is of paramount importance, as surface defects not only compromise product appearance but may also lead to functional failures, resulting in substantial economic losses. Detecting defects on complex surfaces remains a significant challenge due to the variability of defect characteristics, interference from specular reflections, and imaging non-uniformity. Traditional computer vision algorithms often fall short in addressing these challenges, particularly for defects on highly reflective curved surfaces such as aircraft engine blades, bearing surfaces, or vacuum flasks. Although various optical imaging techniques and advanced detection algorithms have been explored, existing approaches still face limitations, including high system complexity, elevated costs, and insufficient capability to detect defects with diverse morphologies. To address these limitations, this study proposes an innovative approach that analyzes the propagation of light on complex surfaces and constructs a polarization imaging system to eliminate glare interference. This imaging technique not only effectively suppresses glare but also enhances image uniformity and reduces noise levels. Moreover, to tackle the challenges posed by the diverse morphology of defects and the limited generalization ability of conventional algorithms, this study introduces a novel multi-scale edge information selection module and a Focal Modulation module based on the YOLOv11 architecture. These enhancements significantly improve the model’s generalization capability across different defect types. Experimental results show that, compared to state-of-the-art object detection models, the proposed model achieves a 3.9% increase in precision over the best-performing baseline, along with notable improvements in recall, mAP50, and other key performance indicators. Full article

Offshore wind turbines (OWTs) exhibit inherent directional variations in inertia, stiffness, and damping properties. This study examines the directionality effect of a 10 MW monopile-supported OWT using an integrated rotor-nacelle assembly (RNA) and support structure model. Through combined theoretical analysis and numerical simulations, this paper systematically investigates the following: (1) the anisotropic characteristics of RNA rotational inertia and blade stiffness, (2) the natural frequency and aerodynamic damping properties of the system, and (3) the directional mechanisms governing seismic responses of MOWTs during parked and running states. The key findings reveal substantial structural anisotropies. The second-order natural frequencies display a 15% disparity between fore–aft (1.43 Hz) and side–side (1.24 Hz) tower modes. The blade frequencies show over 50% differences between flap-wise (0.60 Hz/1.69 Hz) and edge-wise (0.91 Hz/2.71 Hz) modes in first-/second-order vibrations. Moreover, the aerodynamic damping ratios show marked directional contrast, with first-mode fore–aft damping (8%) exceeding side–side values (1.11%) by a factor of 7.2. Consequently, the seismic input directionality induces peak yaw-bearing bending moment variations of 38% (running condition) and 73% (parked condition). The directional effects in parked OWTs are attributed to RNA inertia anisotropy and blade stiffness disparities, while the running condition demonstrates combined influences from inherent system parameters (inertia, stiffness, aerodynamic damping) and wind–wave environmental loading. Full article

Since the 1990s, Polish energy companies have been using new technologies to build wind farms, consisting of large devices. Over the years, the power and the size of installations have increased, and it continues to do so. In Poland, as well as in other countries, a problem with the post-use management of wind turbine blades has appeared. The recycling of wind turbine blades has remained challenging hitherto. The utilization of many different materials and changes in the dimensions cause multi-material waste. Since there are no economically viable recycling technologies available for such large-scale composite products, other treatment strategies for disposed WTBs have to be considered. This study explores the repurposing of WTBs as a pro-environmental alternative approach from a technological and architectural point of view. For this purpose, the study is guided by an analysis of wind turbine locations in reference to the impending need for waste management of wind blades in Poland. Well-profiled blades help transfer a large portion of wind energy to turbine rotors, which is why their construction is a challenge when it comes to designing new objects or elements thereof from decommissioned blades. They have a continuous curvature, where both the cross-section and thickness change, which is why, in the design of architectural or engineering objects, they are cut into smaller parts. This solution makes it possible to optimize the load-bearing properties of individual segments, ensuring a more stable system. Smaller elements also provide greater freedom in shaping architectural forms, which is associated with better control of the final effect from the aesthetic side. The potential of repurposing WTBs is shown, for example, in the design concept for the Archery Centre in Poznan (Poland). Full article

The startup dynamics of wind turbines have a direct impact on their cut-in speed and thus their capacity factor, considering highly transient winds in urban environments. Due to the complex nature of the startup dynamics, the published research on it is severely lacking. Unless the startup dynamics and cut-in speed of a wind turbine are known, it is difficult to evaluate its capacity factor and levelized cost of energy (LCoE) for commercial viability. In this study, a Savonius vertical-axis wind turbine (VAWT) has been considered and its startup dynamics evaluated using numerical techniques. Moreover, the effects of turbine inertia, arising from bearing frictional losses, generator load, etc., on the startup dynamics have been studied. Advanced computational fluid dynamics (CFD)-based solvers have been utilized for this purpose. The flow-induced rotation of the turbine blades has been modeled using a six degree of freedom (6DoF) approach. Turbine inertia has been modeled using the mass moment of inertia of the turbine rotor and systematically increased to mimic the additional inertia and losses due to bearings and the generator. The results indicate that inertia has a significant impact on the startup dynamics of the VAWT. It was observed that as the turbine inertia increased, it took longer for the turbine to reach its steady or peak operational speed. Increasing the inertia by 10%, 20% and 30% increased the time taken by the turbine to reach its peak rotational speed by 13.3%, 16.7% and 23.2%, respectively. An interesting observation from the results obtained is that an increase in turbine inertia does not change the peak rotational speed. For the Savonius rotor considered, the peak rotational speed remained 122 rpm, and its tip speed ratio (TSR) remained 0.6 while increasing the turbine inertia. Full article

Environmental and social governance targets, as well as the global transition to cleaner renewable energy sources, push for advancements in hydrogen-based solutions for energy generators due to their high energy per unit mass (energy density) and lightweight nature. Hydrogen’s energy density and lightweight nature allow it to provide an extended range of uses without adding significant weight, potentially revolutionizing many applications. Moreover, a variety of sources, including renewable energy, can produce hydrogen, making it a potentially more sustainable option for energy storage despite its main limitations in production and transportation costs. In this framework we are proposing an innovative energy generator that might merge the benefits of batteries and hydrogen. The energy generator is based on a worldwide patented solution introduced by MIEEG s.r.l. regarding the shape of the chambers. This innovative solution can be used to design a 100% H2-fed microturbine with a high power/weight/volume ratio that works as a range extender of battery packs for a comprehensive, high-efficiency hybrid powertrain. In fact, it runs at 100,000 rpm and is designed to deliver about 100 kW in about 15 L of volume and 15 kg of weight (alternator excluded). The system is highly complex due to high firing temperatures, long life requirements, corrosion protection, mechanical and vibrational stresses, sealing, couplings, bearings, and the realization of tiny blades. This paper analyzes the main design challenges to face in the development of such complex generators, focusing on the hot gas path components, which are the most critical part of gas turbines. The contribution of additive manufacturing techniques, the adoption of special materials, and coatings have been evaluated for system improvement. Full article

Reducing friction-induced squeal noise is a common issue in daily life and industrial production, particularly for elastomers. However, adjusting structure and wettability in wet environments to solve the friction-induced squeal noise remains a challenge. Here, inspired by rabbit corneas, a microchannel nanofiber array composite structure superhydrophilic elastomer material was prepared to achieve rapid liquid spreading and optimize liquid distribution. Researchers have found that when the depth of the groove microchannel is 400 μm and the length of the nanofiber is 5000 nm, water rapidly spreads on the surface in only 430 ms. This reduces self-excited vibration caused by friction, thereby reducing squealing noise by 20 decibels (dB). This article proposes a novel and direct biomimetic squealing noise reduction strategy, which has great potential in solving friction vibration noise problems in industry and daily life, such as automotive wiper blades, engines, oil lubricated bearings, etc. Full article