共查询到20条相似文献,搜索用时 140 毫秒
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针对充流管道单向流固耦合数值模拟过程复杂、数据在耦合传递中存在偏差的问题,采用C++语言编制了充流管道单向流固耦合数值模拟程序,实现了从模型建立、流体计算到结构分析过程的自动化,确保了从流体计算到结构计算过程中数据传递的准确性.利用参考文献中的试验数据验证了此程序计算结果的正确性,以实际发电厂的一段疏水管道为例进行单向流固耦合数值模拟,描述了程序自动建立管道模型、模拟管内流体压力分布以及将流体压力数据导入管道结构中进行管道应力计算的过程.结果表明:该充流管道单向流固耦合数值模拟程序具有结果准确、操作简便的特点,可应用于多种充流管道的设计改造和风险预测中. 相似文献
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刘峰 《小型内燃机与摩托车》2014,(5):24-29
为适应柴油机燃油经济性和排放性的要求,高压共轨燃油喷射系统以其特有的优点获得了越来越广泛的重视和研究。高压共轨系统的共轨压力分布情况是当前的研究热点之一。在数值计算过程中着重分析了共轨系统结构、尺寸等对共轨内压力场分布的影响,针对共轨管道内的压力分布问题,运用三维分析软件Fluent,对共轨管道内的高压燃油流动进行了计算分析。通过将几种结构设计方案和不同边界条件的有限元分析结果进行对比,明确了可显著减少压力分布不均的共轨结构的改进方向。 相似文献
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在长距离输水管道水力过渡计算中,空气阀进排气系数多采用常量,为探究防水锤空气阀进排气系数对管道压力变化的影响,通过Fluent软件对DN100防水锤空气阀模拟得到-9~11 kPa的质量流量,并建立不同压差的动态进排气系数曲线,以西山一级提水泵站为例,对空气阀进排气系数分别采用动态值和固定值(均值0.55)进行过渡过程计算并对比分析。数值模拟结果表明,空气阀采用改进后的动态进排气系数对管道负压影响较小,对正压影响较大,且改进后的动态进排气系数有效降低了管道内的压力波动,在泵站实际运行中需关注管路正压变化并注意加强防护,水锤防护计算时应根据空气阀进排气实测资料进行计算,研究结果可为泵站运行中空气阀的水力过渡计算提供一些参考。 相似文献
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Diesel engines, especially for trucks and buses, cause many economical and ecological problems. Diesel exhaust emissions are a major source of pollution in most urban centers around the world. Furthermore, the price of crude oil continues to increase rapidly. The use of alternative fuels (liquified petroleum gas, LPG and compressed natural gas, CNG) and the optimization of combustion present effective solutions. Improving combustion is directly related to improving the intake aerodynamic movements which is influenced by the inlet system, especially the intake manifold. In this paper we have studied the geometry effects of two intake manifolds on the in-cylinder flows by two methods, numerically and experimentally. These two manifolds are mounted on a fully instrumented, six-cylinder, 13.8 l displacement, heavy duty, IVECO engine, installed at the authors’ laboratory, which is used to power the urban bus diesel engines in Sfax. This engine was modified to bi-fuel spark ignition engine gasoline and gas fuelling. The 1st manifold presents an unspecified geometry whereas the 2nd presents an optimal filling geometry.A three-dimensional numerical modeling of the turbulent in-cylinder flow through the two manifolds was undertaken. The model is based on solving Navier-Stokes and energy equations in conjunction with the standard k-ε turbulence model, using the 3D CFD code FloWorks. This modeling made it possible to provide a fine knowledge of in-flow structures, in order to examine the adequate manifold. Experimental measurements are also carried out to validate this manifold by measuring the important engine performances. Brake power (BP), brake torque (BT) and brake thermal efficiency (BTE), are increased by 16%, 13.9%, and 12.5%, respectively, using optimal manifold. The brake specific fuel consumption (BSFC) is reduced by 28%. Simulation and experiments results confirmed the benefits of the optimized manifold geometry on the in-cylinder flow and engine performances. 相似文献
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Dynamic stall (DS) on a wind turbine is encountered when the sectional angles of attack of the blade rapidly exceeds the steady-state stall angle of attack due to in-flow turbulence, gusts and yaw-misalignment. The process is considered as a primary source of unsteady loads on wind turbine blades and negatively influences the performance and fatigue life of a turbine. In the present article, the control requirements for DS have been outlined for wind turbines based on an in-depth analysis of the process. Three passive control methodologies have been investigated for dynamic stall control: (1) streamwise vortices generated using vortex generators (VGs), (2) spanwise vortices generated using a novel concept of an elevated wire (EW), and (3) a cavity to act as a reservoir for the reverse flow accumulation. The methods were observed to delay the onset of DS by several degrees as well as reduce the increased lift and drag forces that are associated with the DSV. However, only the VG and the EW were observed to improve the post-stall characteristics of the airfoil. 相似文献
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Furling is the dominant mechanism for over speed and power control of small wind turbines. In this paper we present a consistent model of the dynamics of gravity-controlled furling systems based on a Lagrangian formalism. The aerodynamic forces acting on tail vane and rotor have been modeled using Xfoil and blade element momentum (BEM) theory, respectively. Due to the proximity of tail vane and rotor a model of the near-wake generated by the rotor was incorporated into the model, assuming a parabolic wake shape. The different design parameters, such as lever lengths and axis tilt angles, have been studied in a systematic manner and their impact on the wind speed values for entering and leaving the furling regime have been assessed. In the first part of the study the free-stream in-flow wind speed was fixed at a given value and the system was allowed to reach stable conditions. The steady-state values of the yaw and furling angle were recorded as a function of wind speed both for increasing and decreasing wind speed and the consequences for design choices have been discussed. In the second part, a slow variation of input wind speed was superimposed on the constant wind speed signal and the dynamic response of the system was analyzed. The results of the study are thought to provide an initial roadmap for the design of furling systems. 相似文献
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Ye Wang Liang-Chen Wang Zhi-Min Lin Yu-Huan Yao Liang-Bi Wang 《International Journal of Heat and Mass Transfer》2012,55(9-10):2353-2364
The overall heat transfer performance of a tube bank fin heat exchanger is very important for engineering applications. Developing a fin pattern with good heat transfer performance for tube bank fin heat exchanger needs more our intensive effort. There are two methods to obtain the heat transfer performances of a fin pattern, i.e., one is experimental method, and the other is numerical method. If numerical method is used, the thermal boundary condition on the fin surfaces is necessary. Generally, there are two ways to treat the thermal boundary, i.e., one is to treat fin surface with uniform temperature, and the other is to use a conjugate numerical method. The former is very easy to be applied in numerical method, but the latter needs more numerical effort. This paper reports the condition under which whether a conjugate numerical method or a numerical method just specifying uniform temperature thermal boundary condition should be used. It is found that such condition is the fin efficiency. When the fin efficiency is less than 0.8, a conjugate numerical method must be used. Otherwise, the numerical results obtained by applying an uniform temperature thermal boundary condition on the fin surfaces has only slightly differences with the results obtained by a conjugate numerical method. The reported results will provide a criterion for the researchers to choose a suitable numerical method in finding a fin pattern more efficiently and reliably. 相似文献
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为了从细观尺度对混凝土结构耐久性问题进行数值模拟研究,阐述了混凝土内物质传输机理,建立不同传输过程的数值方程。通过对数值方程的求解,得到混凝土内物质传输过程的扩散系数及有害物质浓度,与相关试验结果对比分析表明,理论求解与试验结果吻合度较高。采用Galerkin有限元法、中心显式差分格式、迎风差分格式、Crank-Nicolson格式对数值方程进行求解,得到数值解的稳定性不同。采用Pe数判别法,且保证Pe数小于1,验证数值方程解的稳定性,其中,Crank-Nicolson格式求解的稳定性最好,表现为无条件稳定,其余3种方法求解的稳定性相同。 相似文献
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发动机冷却水三维流动数值模拟基础研究 总被引:23,自引:1,他引:23
本文在作者已完成的不可压缩流体三维流动数值模拟研究的基础上,对发动机冷却水三维流动的数值模拟方法进行了基础性研究。文章对具有发动机冷却水腹复杂形状的箱体内的水进行了三维流动模拟计算,介绍了数值模拟的基本方法,并对计算结果进行了分析,说明了该方法的有效性。该文介绍的内容是深入研究实际发动机冷却水三维流动数值模拟的基础。 相似文献
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The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteris- tics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant con- tains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length [1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were per- formed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine char- acteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also par- tially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calcula- tion stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition. 相似文献
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