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民用飞机复合材料尾翼舵面作动器选型时,除需考察作动器系统及自身性能外,还需考察作动器对结构产生的载荷和重量影响。以结构减载和减重为出发点,对复合材料尾翼舵面的作动器开展选型研究。分析了在铰链轴布置位置不同的情况下,两种液压作动器,即点对点作动器和返力连杆作动器对尾翼结构的作动反力及结构重量的影响。研究发现:铰链轴居中布置时,舵面连接点处集中力比采用点对点作动器减少约40.2%~55.18%,安定面连接点处集中力减少约87.23%~88.7%;铰链轴非居中布置时,安定面连接点处集中力比采用点对点作动器减小约75.98~97.81%。重量对比分析发现,采用返力连杆作动器对尾翼结构的减重非常有利,返力连杆作动器在民用飞机复合材料尾翼结构上具有明显的应用优势。 相似文献
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(Ca,Mg)—Sialon陶瓷在空气及水润滑条件下的磨损机理研究 总被引:7,自引:7,他引:7
利用SRV球-盘磨损试验机考察了一种(Ca,Mg)-Sialon陶瓷在空气及水中的摩擦学性能,并采用EPMA,SEM,EDAX以及XPS等分析手段对其磨损机理做了进一步研究。结果表明:(Ca,Mg)-Sialon陶瓷在水中比在空气中具有更低的摩擦因数,但具有较高的磨损体积损失。 相似文献
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在形状记忆合金(SMA)复合材料研究中,相变特性的研究是一个主要的工作.基于Eshelby的等效夹杂模型和Mori和Tanaka的场平均法,考虑到SMA材料的强物理非线性,发展了增量型的等效夹杂模型(IncrementalEquivalentInclusionModel).考虑在某一温度循环条件下讨论形状记忆合金短纤维增强的铝基复合材料在热载下的相变行为.特别研究了SMA短纤维复合材料在变温过程中纤维几何尺寸、体积分数等参数对SMA复合材料的相变行为和SMA内残余应力等的影响.这些工作对于指导材料设计和了解SMA复合材料热机械特性是颇有意义的. 相似文献
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李洪波 《应用数学和力学(英文版)》1996,17(10):939-944
ONUNILATERALLYCONSTRAINEDMOTIONSOFRIGIDBODIESSYSTEMSLiHongbo(李洪波)(MMRC,InstituteofSystemsScience,AcademiaSinica,Beijing100080... 相似文献
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要使边界元法象有限元法那样得到广泛应用,必须开发与有限元法相媲美的大型边界元法程序包。国外虽出现少数几个边界元法程序包,但由于结构、功能等方面的原因,还不能成为边界元法广泛应用的工具。针对这种情况,本文借鉴现有的先进的有限元法程序包,研制了大型固体力学边界元法程序包BESMAP,BESMAP在总体设计、计算能力、使用方便和功能齐全等方面作了研究和改进。 相似文献
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KANE’SEQUATIONSFORPERCUSSIONMOTIONOFVARIABLEMASSNONHOLONOMICMECHANICALSYSTEMSZhangYueliang(张耀良)(HarbinEngineeringUniversity,H... 相似文献
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N. F. Vel'tishchev 《Fluid Dynamics》2004,39(2):189-197
On the basis of a numerical simulation of convection in a horizontal fluid layer with a uniform heat source it is concluded that the convective heat flux is constant over the entire convection layer not only in the case of steady-state external conditions but also in the case of heating (cooling) of the fluid layer at a constant rate. The convective heat flux is mainly determined by the Rayleigh number and depends only slightly on the layer heating (cooling) rate. 相似文献
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o. Prof. Dr.-Ing. H. Brauer Prof. dr hab. Inż. M. Dylag Dr. inż. J. Kasz 《Heat and Mass Transfer》1988,23(2):61-68
The influence of free convection on forced convection heat transfer becomes important in laminar flows. Numerical methods have been applied for a study of mixed convection in vertical tubes for the following conditions: temperature-dependent fluid density, constant wall temperature and parabolic profile of axial velocity at the tube entrance. Both cases: heating and cooling have been considered. 相似文献
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The present study considers flow and heat exchange in the neighborhood of a subterranean pipeline on irrigated sector of a route. The flow is caused by thermal convection of the liquid in the field of gravitational forces, this convection being connected with the cooling or heating of the liquid near the surface of the pipeline.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 51–56, November–December, 1987. 相似文献
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Y.M.AL-BADAWI H.M.DUWAIRI 《应用数学和力学(英文版)》2010,31(9):1105-1112
In this study, the magnetohydrodynamics (MHD) natural convection heat transfer with Joule and viscous heating effects inside an iso-flux porous medium-filled inclined rectangular enclosure is studied numerically. An iso-heat flux is applied for heating and cooling the two opposing walls of the enclosure while the other walls are adiabatic. The Forchheimer extension of Darcy-Oberbeck-Boussinesq and energy equations is transformed into a dimensionless form using a set of suitable variables instead of a finite difference scheme. The governing parameters are the magnetic influence number, the modified Rayleigh number, the inclination angle, and the aspect ratio of the enclosure. The results show that viscous and Joule heating effects decrease heat transfer rates. 相似文献
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Start-up and steady thermal oscillation of a pulsating heat pipe 总被引:4,自引:0,他引:4
As a novel electronic cooling device, pulsating heat pipes (PHPs) have been received attention in recent years. However, literature survey shows that no studies were carried out on the start-up and steady thermal oscillation of the PHPs. In the present paper, the copper capillary tube was being bended to form the snake-shaped PHP. Heating power was applied on the heating section, and transferred to the condensation section and dissipated to the environment by the pure natural convection. The inside diameter of the capillary tube is 2.0 mm and the working fluid is selected as FC-72. A high speed data acquisition system was used to detect the start-up and steady thermal oscillation of the PHP. Two types of the start-up process were observed: a sensible heat receiving start-up process accompanying an apparent temperature overshoot followed by the steady thermal oscillation at low heating power, and a smooth sensible heat receiving start-up process incorporating a smooth oscillation period at high heating power. For the steady thermal oscillation, also two types were found: the random thermal oscillation with a wide frequency range, indicating the random distribution of the vapor plug and liquid slug inside the capillary tube at low heating power, and the quasi periodic thermal oscillation with the same characteristic frequency for both heating section and condensation section, indicating the uniform distribution of the vapor plug and liquid slug inside the capillary tube at high heating power. The power spectral density (PSD) was used to analyze the thermal oscillation waves. The frequency corresponds to the time that a couple of adjacent vapor plug and liquid slug passing through a specific wall surface. 相似文献
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Experimental and numerical studies of natural convection in a single phase, closed thermosyphon were carried out using a
vertical, rectangular enclosure model. Only one vertical plate plays the role of heat transfer surface having 100 mm height
and 100 mm width, and others act as the adiabatic wall made of transparent plexi-glass. The heat transfer surface is separated
into three horizontal zones with an equal height; top 1/3 and bottom 1/3 of the surface are cooling and heating zones, respectively
and intermediate section is an adiabatic zone. Water is used as the working fluid. Variable parameters are distance D between the heat transfer surface and an adiabatic plate opposite to the heat transfer plate, and temperature difference
ΔT between heating and cooling zones. By changing both D and ΔT, three regimes of the natural convection flow; quasi-two-dimensional steady, three-dimensional steady and unsteady flows
are observed by means of thermo-sensitive liquid crystal powder and numerically simulated very well by solving a set of governing
equations.
Received on 17 January 2000 相似文献
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The aim of the work is to present a detailed numerical study of the transient forced laminar convection flow over a flat
plate, when thermal conditions are due to arbitrary wall heat flux variations in space. The energy governing equation is modelled
using the Karman–Pohlhausen integral approach in the wide range of Prandtl numbers. The influence of both the thermal problem
nature (transient heating and/or cooling processes) and the wall flux function on the resulting mathematical expressions is
evidenced and the thermal boundary layer thickness behaviour is discussed. In addition, a particular attention has been focused
on both the change in sign of the flux and the duration of the transient heating and cooling. Detailed thermal responses and
convective heat coefficient evolutions due to the change of wall conditions are presented.
Received on 14 April 2000 / Published online: 29 November 2001 相似文献
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E. R. G. Eckert 《Heat and Mass Transfer》1992,27(4):217-223
This report investigates our present ability to predict the thermal performance of film cooling arrangements used to protect the hot components of gas turbines. The required information is usually obtained by model experiments carried out at near room temperature as opposed to the high temperature encountered in the gas turbines. Dimensional or similarity analysis is used to develope the functional relationships for film effectiveness and convective heat transfer and the use of mass transfer experiments with foreign gas injection and naphthalene sublimation based on the heat-mass transfer analogy is discussed. The law of superposition is used to describe the combined effects of film cooling, surface convection or radiation and frictional heating. An order of magnitude estimate indicates to what extent local temperature gradients are alleviated in the cooled walls by internal heat conduction. 相似文献
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Numerical simulations have been carried out to investigate the unsteady natural convection flow in a cavity subjected to a sidewall heat flux varying sinusoidally with time. With all walls non-slip and the upper and lower boundaries and the other sidewall adiabatic, the heating and cooling produces an alternating direction natural convection boundary layer that discharges hot fluid to the top and cold fluid to the bottom of the cavity, generating a time-varying thermal stratification in the cavity interior. Scaling analysis has been conducted for different flow regimes based on the forcing frequency, with the characteristic time scales being the forcing period and the boundary layer development time. The scaling relations are then verified using the simulations, with the results showing overall good agreement with the derived scaling relations. 相似文献
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The present work reports a numerical simulation of mixed convection in an inclined square cavity. The vertical sidewalls are assumed to have a nonuniform temperature distribution. The finite volume method is used to solve dimensionless governing equations. Simulations are performed for different Richardson numbers, amplitude ratios, phase deviations, and cavity inclination angles. The results are presented graphically. The mean heat transfer significantly increases in the buoyancy-dominated mode on increasing cavity inclination angle if both walls have identical heating and cooling zones. 相似文献