When analyzing the dynamics of wind turbines under the action of wind and ground motion, mass-point models cannot accurately predict the dynamic response of the structure. Additionally, the coupling effect between the pile foundation and the soil affects the vibration characteristics of the wind turbine. In this paper, the dynamic response of a DTU 10 MW wind turbine under the coupling effect of wind and an earthquake is numerically studied through the combined simulation of finite-element software ABAQUS 6.14-4 and OpenFAST v3.0.0. A multi-pile foundation is used as the foundation of the wind turbine structure, and the interaction between the soil and the structure is simulated by using p-y curves in the numerical model. Considering the coupling effect between the blade and the tower as well as the soil-structure coupling effect, this paper systematically investigates the vibration response of the blade-tower coupled structure under dynamic loads. The study shows that: (1) the blade vibration has a significant impact on the tower's vibration characteristics; (2) the ground motion has varying effects on blades in different positions and will increase the out-of-plane vibration of the blades; (3) the SSI effect has a substantial impact on the out-of-plane vibration of the blade, which may cause the blade to collide with the tower, thus resulting in the failure and damage of the wind turbine structure.
To address the significant cutting resistance and fracture susceptibility of rotary blades, an innovative blade design was conceived to minimize resistance and enhance fracture resistance. By analyzing the interaction between the blade, soil, and root systems, an optimized design for the blade structure's breakage resistance was developed. The theory of eccentric circular side cutting edges was applied to redesign the curve of the side cutting edge, and kinematic analysis was conducted to determine the optimal edge angle (26.57 degrees). A flexible body model of corn residues was established, and cutting resistance measurements indicated a 15.1% reduction in cutting resistance. The breakage resistance of the rotary blade was validated using a discrete element method-finite element method (DEM-FEM) coupling approach. The results demonstrated the following: neck stress (-16.85%), specific strength efficiency (+9.72%), specific stiffness efficiency (+9.78%), fatigue life (+39.08%), and ultimate fracture stress (+20.16%), thereby meeting the design objectives. The comparison between field trial results and simulation data showed an error rate (<5%), confirming the simulation test's feasibility. These findings provide theoretical references for reducing cutting resistance and enhancing breakage resistance in rotary blades.
In order to solve the problems of traditional orchard-specific green manure crushing and returning machines, such as the single operation effect, root system damage, unsustainable green manure growth, and low utilization rate, an offset crushing-furrowing-burying-straw-returning machine was designed for green manures in orchards. Based on quadratic regression combination experiments, the Discrete Element Method (EDEM) was used to construct a discrete element model simulating the deep furrowing and burying processes of the furrowing and soil-covering device, where the advance speed, plow-shaped furrowing blade rotation speed, and furrowing depth were considered as experimental factors and the coverage rate was taken as an evaluation index, and then simulation analyses were carried out to obtain experimental data; Design-Expert was used to perform ANOVA and RSM analyses, thus finding that its optimal working parameter portfolio consists of the advance speed of 42 m/min, the furrowing blade rotation speed of 300 r/min, and the furrowing depth of 190 mm, and that the coverage rate is 95.82% when this parameter portfolio is applied. Field experiments were conducted to validate the optimal parameter portfolio. The experimental results show that with an average coverage rate of 90.87% (4.95% away from the optimal value based on the simulation experiments on average), an average crushing length qualification rate of 91.24%, and an average root system damage rate of 5.6%, this device is applicable for its operation conditions. The development of this machine and the construction of its parameter model can provide a certain reference value for developing and optimizing related machines including green manure-returning machines.
This paper investigated the seismic vulnerability and performance-based assessment of offshore monopile wind turbine (OWT) considering turbine blades. A three-dimensional finite-element model of NREL 5-MW OWT was established with detailed consideration of the nonlinear-behavior of turbine, monopile, blades, pile-soil interactions and pile-water interaction etc. Subsequently, incremental dynamic analysis and fragility evaluation were conducted via a great number of nonlinear time history analysis involving far-field and near-fault records with and without pulse characteristics. It is found that the ignorance of turbine blades in conventional lumped mass (LM) model would significantly underestimate the vulnerability of OWT's acceleration responses, and more importantly, underestimates the stress level at turbine top, misleading the failure pattern of OWT which may be probably damaged at both top and middle part of OWT rather than solely the middle part as estimated by the LM model ignoring the effect of turbine blades. Finally, it can be concluded that the modeling of turbine blades should be consider in the numerical studies.
Conventional straw-returning machines were incompatible with ridge cultivation terrain and unevenly distributed materials, resulting in substandard operations such as insufficient leaf fragmentation, damage to ratoon stumps, and high cutting energy consumption. In this regard, this paper proposes a novel profiling configuration of chopping and returning machine to adapt to the coverage characteristics of cane leaves in furrow-ridge terrain. The leaves piled at furrow sole are intensively collected and fed into the whirling space by the flexible hook teeth assembly, and are cooperatively broken by the unequal-length swing blades densely arranged along the double helix. Based on the measured topographic trends and dynamic analysis of the leaf-shredding process, experimental factors affecting profiling cutting and picking capabilities of the main components were determined. Further, using chopping qualification rate (CQR) and fragmentation degree (CFD) as indicators, field trails were conducted through a response surface method to test the comprehensive crushing performance of the machine. After multi-objective optimization, the optimal structural and operating parameters were determined as: blade length gradient of 1.57 cm, teeth spacing of 6.84 cm and feed speed of 3.2 km/h. With such adaptive configurations, CQR and CFD reached 81.14% and 0.101, respectively, which were significantly improved by 60.50% and 47.99% compared to those of conventional machines. Crushed leaves appeared to be more thoroughly mixed with the soil and more evenly spread in the field. Meanwhile, the traction resistance tended to be stable, with an effective RSM 45.85% lower than the value of higher-level blade gradient, indicating a better overall fit with the irregular terrain. This study can provide a reference for the development of leaf-chopping and returning machines suitable for ridge-type crops.
Weeds compete with rice for sunlight and nutrients and are prone to harboring pathogens, leading to reduced rice yields. Addressing the issues of low weeding efficiency and weed mortality rates in existing inter-row weeding devices, the study proposes the design of a combination paddy field inter-row weeding wheel. The device's operation process is theoretically analyzed based on the weed control requirements in the northeastern region of China, leading to the determination of specific structural parameters. This research conducted experiments on the mechanical properties of weed cutting to obtain geometric parameters for paddy field weeds. It was found that the range for the cutting gap of the dynamic-fixed blade is between 0.6 mm to 1.4 mm and the cutting angle is between 5 degrees to 15 degrees, resulting in the lowest peak cutting force for weeds. Using LS-DYNA R12.0.0 dynamic simulation software, a fluid-structure interaction (FSI) model of the weeding wheel-water-soil system was established. By employing the central composite experimental design principle and considering the soil stir rate and coupling stress as indicators, the optimal structural parameter combination for the device is obtained: a dynamic-fixed blade cutting gap of 1.4 mm, a cutting angle of 10.95 degrees, and a dynamic blade install angle of -3.44 degrees. Field experiments demonstrated that the device achieved an average weeding rate of 89.7% and an average seedling damage rate of 1.9%, indicating excellent performance. This study contributes to improving weed mortality rates and provides valuable guidance for inter-row mechanical weeding technology.