一种新型电磁作动器的仿真分析及试验验证

针对目前电磁作动器电磁力小、漏磁严重等问题,设计出一种对称式双线圈多永磁体反向串接结构的作动器。研究了该作动器的共振频率、幅值与作动器刚度、阻尼之间的关系;采用有限元电磁场仿真分析了该作动器的磁场分布和线圈所受的电磁力,并通过试验加以验证。     

基于代理模型与参数敏感性分析的扇形气膜孔优化

为获得更高的冷却效率,采用两步法完成扇形气膜孔的几何优化.以扇形孔出口前缘长度L1、尾缘长度L2、出口宽度H和圆柱段长度Lm作为优化变量,构造第1轮拉丁起立方样本空间,通过敏感性分析得到目标函数对各优化变量的敏感度.选择高敏感度参数,生成第2轮参数的样本空间,构建Kriging代理模型,采用多岛遗传算法寻优.结果 表明...     

基于集中参数模型的HOFFELL低温地热田热储模拟与评价

低温地热田热储研究有利于地热资源的开发与利用。通过介绍以供暖为主要目的的冰岛Hoffell低温地热田地质概况、地热地质特征、地热系统概念模型和资源潜力,论述了集中参数模型的实现原理和数学基础。基于201d的开采试验和集中参数模型,模拟了热储水位在开采过程中的响应。模拟结果表明,集中参数模型中的双容器封闭模型和双容器开放模型模拟的水位拟合度较高,分别为98.7%和99.3%,并进一步采用以上两种模式,预测了热储水位在四种开采流量(28.6、21.4、14.3、7.15L/s)下稳定开采10年的变化趋势。研究成果对我国中低温地热资源的开发利用有一定的借鉴意义。     

新安江模型参数敏感性分析的实证研究

为验证新安江模型参数敏感性,以梁辉水库为例,采用2002～2006年连续5年的逐日水文资料进行日模和次洪模拟,并通过计算及对比分析率定较敏感的参数.结果表明,选择模型的敏感性参数有助于新安江模型率定及资料缺失地区推广使用,为流域水文模拟提供参考.     

基于Morris法的HBV模型参数敏感性分析

随着社会的发展和科技的进步,基于计算机运算的水文模型越来越多地应用于各个流域。为了提高水文模型的预测精度,选择误差平均值、均方根误差、相关系数、转换后的均方根误差和流量历时曲线斜率为目标函数,以绥芬河流域2009～2012年的降水径流资料为基础,通过Morris方法运行HBV模型,分析不同目标函数下参数敏感度指数的值及置信区间收敛情况,发现不同目标函数下参数的敏感性有差异,参数越敏感,达到收敛需要的样本数越多。     

基于WASP模型的水质模拟及参数敏感性分析

基于丹金溧漕河(溧阳段)2015年的水文、水质数据,选用WASP模型的EUTRO模块对氨氮(NH3-N)、化学需氧量(COD)和总磷(TP)进行模拟计算,并以2016年1~5月的水质数据对其进行验证,发现模拟值与实测值吻合度较高,在此基础上对模型主要参数进行敏感性分析。结果表明,θ83对NH_3-N和COD均为最不灵敏参数,θ71对总磷为最不灵敏参数,G_(P1)、K_2对NH_3-N、COD、总磷均为灵敏参数。     

基于成本模型法的1MW变速风电机组的参数优化设计分析

主要针对大型变速变距风力发电机组样机在产业化过程中如何以降低机组发电成本、提高经济性为目标对机组参数的优化设计进行探讨。首先阐述了发电成本的计算过程和成本模型法的基本计算规则,然后以国家863"兆瓦级变速恒频风电机组"研制成果SUT-1000的成本构成为例,分别对机组的主要设计参数即风轮直径和额定风速进行了优化设计和对比,并对依据经验确定的变化因子进行了敏感性分析,最后进行了同等容量约束条件下机组的参数综合优化设计,可适用于不同安装场址。     

堆石料的邓肯E-B模型参数敏感性分析

针对在反演分析中模型参数的敏感性分析是确定待反演参数的重要方法,结合水布垭混凝土面板坝应力变形计算,利用正交试验法对邓肯E-B模型参数进行敏感性分析,获得了邓肯E-B模型各参数对坝体垂直及水平位移的影响状况,研究结果可为确定待反演参数提供参考依据.     

水文模型参数优选方法比较与参数敏感性分析

针对参数率定与敏感性分析为水文模型应用中的难点问题,以白莲河流域为例,基于三水源新安江模型,分别采用单纯形法、罗森布洛克法、遗传算法和单纯多边形进化算法对模型参数优选和敏感性分析进行了比较。结果表明,以遗传算法优选结果为初值,采用其他算法进一步优选全局可获得最佳参数值。该方法定性描述了模型的参数与效率系数间的关系,可为手动调试参数提供理论依据。     

车用内燃机冷却系统动态传热模型

提出了一个基于集总参数法的车用内燃机冷却系统动态传热模型。考虑了内燃机燃烧室、散热器和水泵的传热和冷却系统的工作,建立了机体、散热器、水泵与冷却介质之间的热耦合计算公式。对一台单缸柴油机冷却系的稳态及动态温度进行了计算,结果证实该模型可用于内燃机冷却系统的动态传热特性研究。     

The phase change thermoelastic analysis of biological tissue with variable thermal properties during cryosurgery

Abstract

In this work, the coupling phase change heat transfer process and thermal stress behavior of biological tissue during cryosurgery are studied in the context of a generalized thermoelastic theory. The nonlinear governing equations are constructed while considering the variable thermal properties and solved by a time-domain finite element method based on the effective heat capacity formulation. A 2-D tumor and normal tissue model is adopted for simulating the freezing process in cryosurgery. The effects of temperature-dependent thermal properties and relaxation time on the responses of biological tissue are discussed and illustrated graphically.     

车用内燃机整机热平衡动态传热模型

提出了一个基于集总参数法的发动机动态热平衡模型,考虑了发动机燃烧室的传热、发动机主要部件的传热、冷却系统和润滑系统的工作。建立了燃烧气体与发动机部件、各部件之间、部件与冷却液、部件与润滑油、部件与周围空气之间的热耦合计算公式,对一台单缸柴油机的热平衡及主要部件的温度进行了计算．结果证实该模型可用于发动机热平衡的研究。     

新型燃气轮机热参数故障诊断数学模型的研究和应用

介绍了一种新型燃气轮机热参数故障模型。与以往的热参数故障模型有所不同的是该模型对由故障导致的特性线移动所引起的性能变化及由部件匹配引起的性能变化进行了分离，提高了模型的准确性和精度。此外，本文推导出的故障矩阵可以用来解决由于测量参数的不足而导致的无法求解性能参数的问题。     

Appraisal and calibration of the actuator line model for the prediction of turbulent separated wakes

The aim of this study is to further investigate the accuracy and the reliability of the actuator line model (ALM) predictions for turbulent separated wakes. Large eddy simulations (LES) of the flow around a NACA0009 airfoil are performed mimicking the geometry with the immersed boundary method. Results are validated against experiments and used to assess the accuracy of the ALM predictions for the same airfoil, with different values of the spreading parameter and of the reference velocity and for two values of the angle of attack. It is found that the ALM setup recently derived from linearized inviscid analysis leads to accurate results for the lower angle of attack, while at the higher one for which a significant separation of the boundary layer occurs, the ALM requires a different set of model parameters. This calls for a systematic investigation of the sensitivity to the ALM parameters for separated flows, which is carried out herein through a stochastic approach allowing continuous response surfaces to be obtained in the parameter space. The ALM parameters are calibrated against the results obtained with the immersed boundaries. With the calibrated model parameters, the ALM gives good predictions of the velocity and turbulent kinetic energy in the far wake. Finally, the proposed model parameters are used to predict the flow past a different geometry, a flat plate, at high angle of attack. The accuracy of the prediction of the far wake is again good, showing the robustness of the identified setup.     

Spectral relaxation method analysis of Casson nanofluid flow over stretching cylinder with variable thermal conductivity and Cattaneo–Christov heat flux model

This article deals with non‐Newtonian Casson nanofluid flow and heat transfer over stretching cylinder in a porous medium. The mode of heat transfer is presented considering temperature‐dependent thermal conductivity by integrating the Cattaneo–Christov heat flux and mass flux models. Boundary layer theory is applied to develop the governing partial differential equations from the physical problem. Employing proper similarity transformation, the governing boundary layer equations are transformed into dimensionless system of nonlinear ordinary differential equations. Then, the resulting problem is numerically solved by means of spectral relaxation method. The convergence analysis of the proposed numerical scheme is presented via a table, which confirms almost the 10th order of approximation is enough for the convergence of the skin friction coefficient, local heat transfer, and mass transfer rates. The effects of various embedded parameters on velocity, temperature, and concentration profiles as well as skin friction coefficient, surface heat and mass transfer rates are examined through graphs and tables. The findings reveal that the growth of permeability and velocity slip parameters appears to decelerate the velocity distributions of fluid. Thermal boundary layer thickness tends to develop with greater values of permeability and Brownian motion parameters. Also, the local heat transfer rate is less with Fourier's law of heat conduction than Cattaneo–Christov heat flux model. Furthermore, the validity and accuracy of the present result is checked with the available literature, and very sound agreement has been obtained.     

Rotation,electromagnetic field,and variable thermal conductivity effects on free convection flow past an eternity vertical porous plate

The present research may facilitate the reduction of the number of conversion steps required to include the low output voltages in an electrokinetic biomass process. Variable thermal conductivity and electroosmosis flow have already established great potential in the thermo-elastic models of various manufacturing industries and have been widely used in energy technologies. As a result, the current framework investigates the characteristics of natural convection flow with the influence of variable thermal conductivity and electroosmosis over an eternity vertical porous plate. Coriolis forces and Hall current effects are considered in the momentum equations, and also thermal radiation and variable thermal conductivity are taken as energy equations. A linear chemical reaction parameter is used in the concentration equation. The equation of Poisson–Boltzmann is exploited to depict the electric potential characteristics within the accelerated plate medium. The pdepe command in Matlab software is used to figure out the numerical solutions to equations about momentum, energy, and concentration. The expressions of fluid transverse velocity, fluid axial velocity, fluid temperature, and concentration profiles are presented as numerical results and also derived vital relevant stream parameters diagrammatically, whereas the numerical values of primary skin friction, secondary skin friction, and Nusselt number are presented in tabular form for various values of pertinent flow parameters. The temperature rises as the strength of the thermal conductivity variable parameter increases. Also, as the values of the Taylor number and the thermal conductivity variable parameter go up, the primary velocity goes down. Similarly, secondary velocity increases in the opposite direction as the Taylor number and thermal conductivity variable parameter increase.     

民用飞机短舱内冷却系统试验验证技术研究

结合民用支线飞机短舱冷却系统的试验,建议了一套合理的冷却系统试验方法和测试改装工作思路。提出了冷却试验的可接受判据,列出了试验中可能出现的紧急情况及相应处理措施,给出了冷却试验测试参数的数据处理方法。     

Analytical approaches for thermal analysis of radiative fin with a step change in thickness and variable thermal conductivity

In this paper, heat transfer in a straight fin with a step change in thickness and variable thermal conductivity which is losing heat by radiation to its surroundings is analyzed. The calculations are carried out by using the differential transformation method (DTM) and variational iteration method (VIM) that can be applied to various types of differential equations. The results obtained employing the DTM and VIM are compared with a finite difference technique with Richardson extrapolation which is an accurate numerical solution to verify the accuracy of the proposed methods. As an important result, it is depicted that the DTM results are more accurate in comparison with those obtained by VIM. After these verifications the effects of parameters such as thickness parameter α, dimensionless fin semi‐thickness δ, length ratio λ, thermal conductivity parameter β, and radiation–conduction parameter N_r, on the temperature distribution and fin efficiency are illustrated and explained. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj) . DOI 10.1002/htj.21000     

Influence of thermophoretic deposition and viscous dissipation on magnetohydrodynamic flow with variable viscosity and thermal conductivity

In this study, we numerically explore the impact of varying viscosity and thermal conductivity on a magnetohydrodynamic flow problem over a moving nonisothermal vertical plate with thermophoretic effect and viscous dissipation. The boundary conditions and flow-regulating equations are converted into ordinary differential equations with the aid of similarity substitution. The MATLAB bvp4c solver is used to evaluate the numerical solution of the problem and it is validated by executing the numerical solution with previously published studies. The impacts of several factors, including the magnetic parameter, Eckert number, heat source parameter, thermal conductivity parameter, stratification parameter, Soret, Dufour, Prandtl number, and Schmidt number are calculated and shown graphically. Also, the skin friction coefficient, Nusselt number, and Sherwood number are calculated. Fluid velocity, temperature, and concentration significantly drop as the thermophoretic parameter and thermal stratification parameter increases. As thermal conductivity rises, it is seen that the velocity of the fluid and temperature inside the boundary layer rise as well. Also, the Soret effect drops temperature and concentration profile. The applications of this type of problem are found in the processes of nuclear reactors, corrosion of heat exchangers, lubrication theory, and so forth.