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Nonlinear bending analysis was performed of magnetoelectroelastic (MEE) composite plates under a mechanical and magnetoelectric (ME) load by using von Karman's nonlinear geometric equation and the higher order shear deformation theory (HSDT). Nonlinear higher order partial differential equations for MEE plates were derived by using Hamiltonian equilibrium equation. The MEE plate is considered to have clamped boundary condition. The nonlinear high-order equations can turn into algebraic equations through Galerkin method. Then the effects of scale effect of MEE plate (for instance, the aspect ratio) and external load (for instance, mechanical) on the displacement of the considered MEE plate were investigated. [ABSTRACT FROM AUTHOR]

A gearbox is part of the transmission chain of wind turbine, which can increase rotational speed and reduce torque. Dynamic characteristics of the gearbox directly influence the vibration and the service life of the wind turbine system. In this paper, dynamic behaviors of a megawatt level wind turbine gearbox are studied theoretically and experimentally by dividing the gearbox into a transmission sub-system and a body sub-system. The transmission sub-system, i.e., the gear-shaft-bearing sub-system, is coupled with the gearbox body using bearings which are simulated as mass-less springs. The theoretical study applies a finite element model for the gearbox, where the internal excitations are caused by time-varying stiffness, transmission errors and mesh impacts. The time-varying wind load is considered as the external excitation, collected by a remote real-time online test and transformed into load spectrums through the rain-flow counting method. With boundary conditions and working conditions being defined in the finite element model, the natural characteristic analysis and the dynamic response analysis are conducted. Results show that the operating frequencies of the gearbox are far away from the main natural frequencies of the system, thus avoiding resonances. The main vibration components of the gearbox are with meshing frequencies of the second and third gear stage and their multiplication counterparts. Moreover, the greatest vibration occurs at the bearing housing of the high-speed shaft with the root-mean-square value of its vibration speed less than 3.5 mm/s. A test rig is developed and the experimental vibration conditions are monitored by acceleration sensors. The experimental results are in accordance well with the theoretical results. In this way, the theoretical model is validated. The methodology reported in this paper can provide valuable guidance for practical industrial engineers. [ABSTRACT FROM AUTHOR]

A new type of valveless piezoelectric micropump is presented. Synthetic jet and Coanda effect are utilized to achieve larger and bidirectional flow rate. The numerical simulation applying the velocity and pressure boundary conditions as well as the SST turbulence model were utilized to research the performance and internal flow state of the micropump. The simulation method was tested by the previous experimental data and the results matched well. The results suggest that the flow rate of the micropump is related to the Reynolds number and frequency. The entrainment flow rate of synthetic jet accounts for over 80% of the total outflow rate. The outflow rate is much larger than the volume change of the micropump chambers. There is an optimal frequency to obtain the maximum flow rate regarding the volume change of the chambers as a constant. The fluctuation of the flow rate decreases with the increase of frequency. When the frequency is higher than 25 Hz, the outflow can be continuous. Working at the Reynolds number of 1000 and optimal frequency of 50 Hz, the flow rate is 6.8 ml/min. [ABSTRACT FROM AUTHOR]

There exit model errors in the constructed Horizontally reversible plough (HRP) structure through Interference check technique (ICT). This is basically due to missing parts and geometric interference and, hence, has significantly adverse effects in improving HRP. In this paper an improved design to refine the three dimensional (3D) model of HRP is implemented by using Virtual assembly technology (VAT). To achieve this, the authors propose a combined virtual assembly semantics and constraint for assembly planning and simulation of HRP in the commercial software, e.g., SolidWorks. First, the assembly planning of HRP was captured with a semantics-based model, including spatial position, assembly orientation, type and parameters of the semantic entities; secondly, the assembly simulation of HRP was performed by using constraint-based VAT, e.g. component grasping, moving and releasing; finally, the obtained HRP model was verified through ICT again. The results demonstrate that not any model error exists in the refined 3D HRP model any longer and that semantics and constrain based VAT can support the interactive operation more effectively and accurately than those with geometric constraints. This technique was previously used for HRP model. Based on the refined 3D HRP model, the design improvement of Remote cylinder base (RCB), an important component of HRP, will be forthcoming in a future paper. [ABSTRACT FROM AUTHOR]

This work presents a numerical and experimental investigation on the heat transfer and turbulent flow of cooling steam in a rectangular duct with 90° ribs and studies the effect of cooling conditions on the heat transfer augmentation of steam. In the calculation, the variation range of Reynolds is from 10,000 to 190,000, the inlet temperature varies from 300°C to 500°C and the outlet pressure is from 0.5MPa to 6MPa. The aforementioned wide ranges of flow parameters cover the actual operating condition of coolant used in the gas turbine blades. The computations are carried with four turbulence models (the standard k-ɛ, the renormalized group (RNG) k-ɛ, the Launder-Reece-Rodi (LRR) and the Speziale-Sarkar-Gatski (SSG) turbulence models). The comparison of numerical and experimental results reveals that the SSG turbulence model is suitable for steam flow in the ribbed duct. Therefore, adopting the conjugate calculation technique, further study on the steam heat transfer and flow characteristics is performed with SSG turbulence model. The results show that the variation of cooling condition strongly impacts the forced convection heat transfer of steam in the ribbed duct. The cooling supply condition of a relative low temperature and medium pressure could bring a considerable advantage on steam thermal enhancement. In addition, comparing the heat transfer level between steam flow and air flow, the performance advantage of using steam is also influenced by the cooling supply condition. Changing Reynolds number has little effect on the performance superiority of steam cooling. Increasing pressure would strengthen the advantage, but increasing temperature gives an opposite result. [ABSTRACT FROM AUTHOR]