This study focused on investigating various existing types of offshore jacket substructures along with a proposed twisted-tripod jacket type (modified jacket (MJ)-structures). The architectures of the three-leg structure, as well as the patented twisted jacket structure motivated the design of the proposed MJ-structures. The dimensions of the structures were designed iteratively using static stress analysis to ensure that all structures had a similar level of load-carrying capability. The numerical global buckling analyses were performed for all structures after the validation by the scaled-down experiments. The local buckling strength of all compressive members was analyzed using the NORSOK standard. The results showed that the proposed MJ-structures possess excellent structural behavior and few structural nodes and components competitive with the patented twisted jacket structures, while still maintaining the advantages of low material usage similar to the three-leg jacket structures. This study provides alternatives for the initial selection and design of offshore wind turbine substructures for green energy applications.

The operational security of power systems for wind farm integration becomes more important as the penetration of wind generation increases. A wind farm may contain hundreds of wind turbines (WT) and thus the power system simulations based on the complex model of a WT consumes much time. This paper proposes an equivalent wind farm model with the frequency-regulation function. The main research works include the establishment of the generic model of a WT, the development of single- and multi-machine equivalent models for a large wind farm, the clustering of WTs based on the developed nonlinear wake model and the Fuzzy C-means (FCM) clustering algorithm, the integration of the frequency-regulation function into the equivalent wind farm (WF) model, and the validation of the developed equivalent WF model by various operating scenarios. The results demonstrate that the proposed multi-machine equivalent method based on the FCM clustering provides a more accurate model than a single-WT equivalent model. Consequently, the research results provides a solution for simulating a large-scale wind power integration, providing efficient, accurate, and fast steady-state and dynamic analyses.

Cooling analysis of fully 3D simulation including multi-cycle time span and heat resource was completed. To test the numerical accuracy, different numerical models and algorithms were applied to simulate the mold temperature profile. Simulation accuracy of different numerical methods was compared and verified by experimental measurements. Mold temperature distribution was measured by an infrared radiation thermal imaging (IRTI) system from which the temperature variations at special interested locations can be obtained. As for heated mold with electric heater resource, fully 3D simulations of mold temperature variation based on both standard finite element method (FEM) in single CPU and finite volume method (FVM) implemented in parallel computation scheme were executed. All simulations show reasonable predictions in accordance with experimental results. However, predicted results of the fully 3D model for FEM and FVM exhibit are more accurate than that of the 2.5D model for BEM. The fully 3D simulated results show the minimum difference of 0.2°C, and the 2.5D model results show a minimum value of 2.4°C. Moreover, the fully 3D model not only can simulate the cyclic, transient mold temperature field but also can obtain polymer temperature simultaneously.

This study presents a numerical model of the hybrid-stabilized argon–steam thermal DC plasma torch of a new design for generating an argon–steam plasma suitable for efficient abatement of persistent perfluorinated compounds. The model includes the discharge region and the plasma jet flowing to the surrounding steam atmosphere contained in a plasma-chemical chamber. Compared to previous studies, the torch had a smaller nozzle diameter (5.3 mm) and a reduced input power (20–40 kW) and arc current (120–220 A). The outlet region for the plasma jet extends to 20 cm downstream of the exit nozzle. Fluid dynamic and thermal characteristics together with diffusion of argon, hydrogen and oxygen species, and distribution of plasma species in the discharge and the plasma jet are obtained for currents from 120 to 220 A. The results of the calculations show that the plasma jet exhibits high spatiotemporal fluctuations in the shear layer between the plasma jet and colder steam atmosphere. The most abundant species in the plasma jet are hydrogen and oxygen atoms near the jet center, and molecules of H₂, O₂ and OH in colder surrounding regions. Satisfactory agreement is obtained with measurements of the radial temperature and electron number density profiles near the jet center close to the nozzle exit.