Improved Engineering Model Research Articles

Improved engineering model for water absorption in softwoods

Modeling of moisture transfer in porous materials is typically partitioned into liquid transport and vapor diffusion. Coefficients for liquid transport are often derived from laboratory measurements of water absorption by partial immersion. Although the assumption that capillary liquid transport is dominant while vapor diffusion is negligible is a reasonable assumption for mineral-based materials, recent work indicates that it is not representative of water absorption in wood across the grain. This article builds on earlier work and develops an improved engineering model for liquid water transport in softwoods. The approach uses a constant liquid diffusivity value, relies primarily on ordinary hygrothermal property measurements, and partitions vapor and liquid transport in a practical way that is informed by current understanding of wood–water interactions. The model is optimized using one-dimensional simulations calibrated against measured water uptake across a range of softwood species. Laboratory measurements were conducted to investigate key properties of eastern white cedar, which had the highest relative error in a previous version of the model, and to examine the practicality and relevance of vacuum saturation and free saturation for southern yellow pine. The model accuracy is improved by paying closer attention to the moisture storage function and capillary saturation value.

Structural nonlinearity of the tensioner model affects parametric instability prediction of deep-water top tensioned risers

TTRs (Top Tensioned Risers) may experience parametric instability ascribed to the time-varying tension exerted by the top floating platform. As ocean exploration steps into deep-waters, ocean environment becomes severe and the flexibility of risers is enhanced due to the increased aspect ratio. Therefore, it requires to figure out the new influential factors for the dynamic prediction with accuracy of TTRs. In parametric stability analysis, it typically adopts a linear model and an engineering model for the tensioner. The structural nonlinearity of the tensioner is commonly neglected or simplified. In this study, a nonlinear model of a direct-acting tensioner system is derived in a rigorous way. The parametric stability of a deep-water TTR is predicted based on Floquet theory employing three tensioner models (i.e., a linear model, an engineering model, and the nonlinear model). It has demonstrated that the structural nonlinearity of the tensioner has a significant effect on the calculations of the top tension and natural frequencies of the riser, and thus affects parametric stability predictions. The instability region adopting the nonlinear model is the largest, and the structural nonlinearity effect becomes more profound with the increase of high-pressure gas volume and low-pressure nitrogen pressure. Moreover, an improved linear model and an improved engineering model have been proposed.

An engineering model for wind turbines under yawed conditions derived from high fidelity models

AbstractThis work presents a significantly improved engineering model for the prediction of the loads in yawed flow. The newly developed model focuses on the so‐called skewed wake effect. This effect leads to an azimuthal variation of the axial induction velocity which depends on the yaw angle, tip speed ratio, wind speed, and radial position. The azimuthal variation of the induced velocities leads to a variation in blade loads, which is important for the prediction of fatigue loads and determines the yawing moment which can be stabilizing or destabilizing and is among others important for passively yawed turbines. The paper puts particular emphasis on the contribution of the root vorticity to the azimuthal variation of induced velocity. Current widely used models typically only take into account the skewed wake effect without the contribution of root vorticity, i.e., leading to a significant different radial dependency of the skewed wake effects. The new model is derived from computational fluid dynamics of 3 multimegawatt‐class wind turbines, namely the NREL 5MW and two 10‐MW turbines designed in the EU projects AVATAR and INNWIND.EU. Simulations were performed by means of an actuator line model. The proposed model is validated with results from a fully resolved computational fluid dynamics model, a free vortex wake code and actuator line model simulations for different wind turbines and yaw angles. The obtained results indicate that in many cases, the new model considerably improves the prediction of the azimuthal variation of axial induction factor and the resulting variation in blade loads and consequent yawing moment.

FLUE GAS DEDUSTING IN VENTURI SCRUBBERS AT THERMAL POWER PLANTS

In this paper, an improved engineering model and analysis techniques are presented of the fly ash particles coagulation with droplets in Venturi tubes of industrial scale, based on spatial variation of the collection efficiency of particles on individual droplets, accounting for spray water flow polydispersity and particle size distribution, which allows to define optimal droplets size and spray water flow rate at different modes of thermal power units operation. The model is validated with the published experimental data on the wet Venturi scrubbers operations at the thermal power plants (TPP) in Ukraine, Russia and Kazakhstan. The results of calculations demonstrate good coincidence with experimental data. The influence of the boiler load and spray water consumption on an efficiency of the TPP Venturi wet scrubbers was studied. The simulation results have shown that moderate increment of spray water consumption up to 0.24 L/m3 allows increasing of the Venturi wet scrubber s efficiency without threat of reaching the dew point in flue gas flow, thus preventing potential corrosion of the power plant equipment downstream. The calculations confirmed that without retrofit of wet scrubbers installed at Ukrainian power plants it will not be possible by these stations to meet European requirements on the allowable levels of emissions from the coal firing power plants.

Dynamic Reluctance Mesh Modeling and Losses Evaluation of Permanent Magnet Traction Motor

In this paper, dynamic reluctance mesh model (DRM) combined with an improved iron losses prediction model are presented to provide fast and accurate way to evaluate the iron losses for permanent magnet (PM) motors with pulsewidth-modulated power supply. A DRM model for high-speed train PM traction motor is first built. The magnetic field distribution for one cycle is then obtained using the DRM method. An improved engineering model of iron losses prediction is applied. Finally, the simulation and testing results are presented to confirm that the proposed combined method is accurate and effective as the finite element method (FEM) model with much less time consumed.

Rheological behavior and process prediction of low viscosity epoxy resin for RTM

The rheological behavior of a low epoxy resin system-SR8100/SD8734 for RTM in aviation industry was studied with viscosity experiments. The dual-Arrhenius rheological model and the improved engineering viscosity model were introduced and compared with the experimental data. The results indicated that the viscosity in the earlier stage calculated by dual-Arrhenius model matched the experimental data. As rising to 400 m·Pas, the viscosity calculated by the improved engineering model was closer to the experimental data. The processing windows of the resin system for RTM were determined by combining the two models, which could predict the rheological behavior of the resin system in a more credible way. 30–45 °C was the optimum processing temperature.

Towards Improved Engineering Model for Sediment Transport Prediction Under Combined Wave-Current Sheet Flows

Sediment transport under combined wave-current sheet flow condition is predicted by a wave-period-averaged (WPA) profile model based on a diffusion concept. The total transport rate is split into current induced and wave induced components with associated model parameters. The current induced transport rate is evaluated through vertical profiles of wave-period-averaged flow velocity and sediment concentration. A new wave-induced transport profile is also proposed utilising the wave-induced current residual velocity and period-averaged sediment concentrations. Important sheet flow processes, including turbulence dumpling in the suspension layer, sediment particle’s hindered settling and phase-lag effects are taken into account through a number of model parameters that have been validated by available laboratory measurements. Sediment size gradient is also considered by a conventional multi-fraction approach with special treatment for the sediment mixing parameters for fine and coarse sediment fractions. Model results for both laboratory and field measurements show its encouraging accuracy for the sediment transport prediction under sheet flow condition.

An Improved Engineering Model of Silicon Solar Cell

An improved engineering model of silicon solar cell is proposed, which uses only four electrical parameters under standard test conditions provided by manufactures. Simulation and experimental results show that the model error was 6 percent below for various combinations of solar radiation and temperature and its accuracy is sufficient for most practical engineering cases.

An Improved Engineering Model of Vector Magnetic Properties of Grain-Oriented Electrical Steels

This paper presents an improved magnetic reluctivity model for vector magnetic properties of anisotropic electrical steel sheet based on Chua-type model using Fourier series expansion of measured <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> waveforms in the viewpoint of engineering application. In the modeling, B-spline surface interpolation is adopted to obtain smooth approximation of measured data. The accuracy of the proposed magnetic reluctivity model is verified by comparing its modeling results with experimentally measured <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B-</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -waveforms with 30 PG110 grain-oriented silicon steel sheet. The nonlinear finite element (FE) formulation is also derived to incorporate the proposed reluctivity model, and applied to magnetic field analysis of a single phase transformer core model. By comparing the numerical results with experimental ones, the effectiveness of the reluctivity model and FE formulation is investigated.