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1.
武浩浩 《荆门职业技术学院学报》2011,(5):18-21
针对NACA4412翼型风力发电机扰流流动特点,建立了二维和三维不可压缩湍流模型,并对基于流体连续性方程和N-S方程及k-ε湍流模型的二维流场进行数值模拟计算。采用多参考系计算（MRF）模型,用FLUENT模拟了流场内翼型截面的受力情况和速度分布情况,得到了NACA4412翼型风机的气动特性。 相似文献
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This paper discusses the unsteady aerodynamic behavior of long-span vaulted roofs. First, a forced vibration test in a turbulent boundary layer is conducted in a wind tunnel. The models are force vibrated in the first anti-symmetric mode to investigate the effects of wind speed, rise/span ratio, and the amplitude and frequency of forced vibration on the distributions of wind pressures and unsteady aerodynamic forces. Then, a large eddy simulation (LES) is carried out to clarify the physical mechanism of wind-roof interaction as well as to investigate the influences of a roof’s vibration on the flow field around the roof. From the results of the wind tunnel experiment and the LES, we discuss the characteristics of unsteady aerodynamic forces on a long-span vaulted roof over a wide range of the reduced frequency of vibration. The effect of unsteady aerodynamic forces on the dynamic response of the roof is also discussed. A comparison between the wind tunnel experiment and the LES indicates that the LES can be used effectively to evaluate the unsteady aerodynamic behavior. 相似文献
3.
The influence of sandstorms on train aerodynamic performance and safe running was studied in response to the frequent occurrence
of sandstorm weather in north China. An Eulerian two-phase model in the computational fluid dynamic (CFD) software FLUENT,
validated with published data, was used to solve the gas-solid multiphase flow of a sandstorm around a train. The train aerodynamic
performance under different sandstorm levels and no sand conditions was then simulated. Results showed that in sandstorm weather,
the drag, lift, side forces and overturning moment increase by variable degrees. Based on a numerical analysis of aerodynamic
characteristics, an equation of train stability was also derived using the theory of moment balance from the view of dynamics.
A recommended speed limit of a train under different sandstorm levels was calculated based on the stability analysis. 相似文献
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《天津大学学报(英文版)》2017,(6)
The development of offshore wind farms in deep water favors floating wind turbine designs, but floating horizontal axis wind turbines are facing the challenge of high cost of energy(CoE). The development of innovative designs to reduce the CoE is thus desirable, such as floating vertical axis wind turbines(VAWTs). This study demonstrates the characteristics of aerodynamic loads and load effects of a two-bladed floating VAWT supported by a semi-submersible platform. Fully coupled simulations are performed using the time-domain aero-hydro-servo-elastic code SIMO-RIFLEX-AC. It is found that thrust, lateral force, and aerodynamic torque vary considerably and periodically with the rotor azimuth angle. However, the variation in the generator torque can be alleviated to some extent by the control strategy applied. Moreover, the variations of platform motions and tensions in the mooring lines are strongly influenced by turbulent winds, whereas those of tower-base bending moments are not. The towerbase bending moments exhibit notable two-per-revolution(2P) response characteristics. 相似文献
6.
In this paper, the effects of second-order difference-frequency wave forces on the global motion of an offshore wind turbine system with a large displacement under the survival condition are studied. In this case, the hydrodynamic force is the main force because the blades are feathered to reduce the lifting force. The first-order hydrodynamic forces are calculated by WADAM, while the second-order wave forces are calculated by a customized MATLAB module. Then the hydrodynamic coefficients are transferred to the wind turbine analytical code FAST. Through the comparisons of dynamic responses between the first- and second-order numerical models, it is found that the second-order wave forces significantly influence the motion of floating wind turbine under the survival condition. Moreover, neglecting the second-order force significantly underestimates the tension forces in the mooring lines. 相似文献
7.
运用模式匹配法，分析了圆-圆形槽波导结的散射特性．在圆-圆形槽波导结上匹配电场和磁场的边界条件，然后在边界方程两边同乘以圆波导和圆形槽波导的模式方程，得到了散射矩阵方程，结的散射系数可由此方程得出．然后分析了圆形槽波导中放置圆形膜片的散射特性．最后讨论了数值计算结果的收敛性；当选择恰当的模式组时，得到了收敛的数值结果，同时给出了膜片散射系数的频率响应结果． 相似文献
8.
设计并实现了一个小型风力发电机的外特性测试平台,平台包括低速开放式风洞、数据采集系统两部分.风洞设计成口径3.5 m的直流式风洞,实验段采用圆形截面,动力段采用多风机提供动力,在风流通过蜂窝器后,大大改善了风流效果并提高了可靠性.数据采集系统通过工业控制数据采集卡对风速、风力发电机转速、输出电压、电流等进行数据采集和处理.通过对某小型风力发电机进行测试的结果表明,平台可满足测试小型风机外特性的实验要求. 相似文献
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基于小干扰稳定的概念和分析方法,通过3种不同类型的风电机组,采用PSAT软件中的特征值分析方法,研究风电机组在类型不同、风电场接入距离不同以及风电渗透率不同情况下接入WSCC 3机9节点系统时对小干扰稳定性的影响。研究结果表明:风电机组类型、接入距离以及风电渗透率均会对系统产生不同程度的影响。DFIG的影响优于另外两个机组,在风电机组确定的情况下,距离越近、风电渗透率越低对系统的小干扰稳定性越有利。 相似文献
10.
分析了风力机的基本特性,阐述了风力发电机组控制系统在低于额定风速时风力机的最大风能捕获及高于额定风速情况下的变桨距控制。在此基础上,利用SVM(support vector machines)优化风力机的风能利用系数以及变桨距控制系统的控制参数。仿真分析表明,风能转换系数的支持向量机模型具有很好的精度和泛化性能,而优化后的变桨距控制系统可对输出功率的调节获得较好的效果,保证风电系统的恒功率输出。 相似文献
11.
The rheological characteristics of the oil film on the rod-seal interface in the sealing zone have a major influence on the behavior of reciprocating seals. Because of the addition of polymers, the viscosity and temperature properties of hydraulic oil have improved and the fluid presents non-Newtonian characteristics. To investigate the influence of these characteristics on seal behavior, a soft elastohydrodynamic lubrication (EHL) numerical model is introduced to simulate a step seal under a mixed lubrication condition. A modified Reynolds equation is derived for calculating the fluid film pressure distribution more accurately. The equation is based on the power law fluid model and Jakobsson-Floberg-Olsson (JFO) cavitation theory. Results are presented to gain insight into the effect of non-Newtonian fluid characteristics on seal behavior, and the simulated results are compared to those of a Newtonian fluid to reveal the seal mechanism. The influence of operating parameters and the seal surface root mean square (RMS) roughness on sealing performance under different power law indexes is also investigated and discussed. 相似文献
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To analyze wind-induced response characteristics of a wind turbine tower more accurately, the blade-tower coupling effect was investigated. The mean wind velocity of the rotating blades and tower was simulated according to wind shear effects, and the fluctuating wind velocity time series of the wind turbine were simulated by a harmony superposition method. A dynamic finite element method （FEM） was used to calculate the wind-induced response of the blades and tower. Wind-induced responses of the tower were calculated in two cases （one included the blade-tower coupling effect, and the other only added the mass of blades and the hub at the top of the tower）, and then the maximal displacements at the top of the tower of the tow cases were compared with each other. As a result of the influence of the blade-tower coupling effect and the total base shear of the blades, the maximal displacement of the first case increased nearly by 300% compared to the second case. To obtain more precise analysis, the blade-tower coupling effect and the total base shear of the blades should be considered simultaneously in the design of wind turbine towers. 相似文献
13.
谐振子量子制冷循环性能的优化分析 总被引：1，自引：0，他引：1
林比宏 《泉州师范学院学报》2005,23(6):27-33
基于量子主方程和半群逼近研究以谐振子系统为工质，由两个等温和两个等谐振子数过程组成的不可逆谐振子量子制冷循环的一般性能特性，导出了制冷循环的制冷系数、制冷率、输入功和熵产率等重要参数的一般表达式．并详细讨论了高温极限下谐振子量子制冷循环的优化性能，导出了最大制冷率和相应的制冷系数．所得结论可为非常规工质低温制冷循环的优化设计提供理论基础． 相似文献
14.
On maximum power point tracking control strategy for variable speed constant frequency wind power generation 总被引：1，自引：0，他引：1
WU Guo-qing NI Hong-jun WU Guo-xiang ZHOU Jing-ling Zhu Wei-nan MAO Jing-feng CAO Yang 《重庆大学学报(英文版)》2010,9(1):21-28
Based on the characteristic of AC-excited variable speed constant frequency （VSCF） wind power generation, the vector control technique was applied in a doubly fed induction generator （DFIG）. Maximum wind energy or maximum output power point can be tracked by decoupling control of active power and reactive power. The research result shows that the net power of generation system delivered to grid in maximum wind energy tracking mode is not the most. We presented a novel maximum power point tracking （MPPT） control strategy by analyzing the DFIG mathematic model and power relations which delivered the maximum power to the grid. The maximum power point could be tracked automatically without measuring wind speed in the control strategy and the control was independent of optimal turbine power curve, which had excellent dynamic and static performances and robustness. Simulation and experimental results testify the accuracy and validity of the control strategy. 相似文献
15.
INTRODUCTION Long-span cable-stayed bridges under service andparticular construction conditions are very susceptibleto wind action due to their great flexibility, so thewind stability (aerodynamic stability or flutter stabil-ity) is becoming a major concern in the design andconstruction phrases. As compared with the servicecondition, although the period of erection is not toolong, the structural stiffness of cable-stayed bridgesunder erection is greatly reduced, and consequentlythey be… 相似文献
16.
杨晓静凌静秀银光球 《福建工程学院学报》2017,(1):30-34
基于虚拟样机技术及有限元法,提出了破碎站钢结构的力学模型等效及落料冲击系数的数值模拟方法,采用理论公式对单块物料冲击钢结构的动载系数进行计算,并将其与数值模拟分析结果对比。分析表明,1m3大小的正方体煤岩物料从5m高度下落直接冲击钢结构,其冲击系数的理论计算及刚体动力学分析结果均为123,而柔体动力学分析结果为125,三者误差约1.6%,表明提出的数值模拟方法及钢结构等效模型有效,分析方法可为破碎站的性能评估及结构优化提供基础。 相似文献
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To reduce the wind-induced drag and improve the wind-resistance performance of a high-rise building, steady suction control is introduced into the building structure. Based on validation of the numerical methods by experiment with suction control over the flow separation ofa 3D backward-facing step, the Reynolds stress equation model is used to investigate the drag reduction （DR） properties of a high-rise building whose side faces are controlled by all-height suction. Effects of the orifice geometrical parameters and suction flux parameters on the DR and the separation control are analyzed, and the detailed flow fields are shown to clarify the mechanism of suction control. The results indicate that suction control is very effective in reducing the wind loads on the high-rise building model, and only the dimensionless suction flux dominates. Lastly, the power consumed and the counterforce induced by suction are discussed, the suction models become the ＂zero-drag＂ model under certain suction angles. 相似文献
19.
Dynamic characteristics analysis of a misaligned rotor-bearing system with squeeze film dampers 总被引：1，自引：0，他引：1
In this paper, a dynamic model is established for a two-stage rotor system connected by a gear coupling and supported on ball bearings with squeeze film dampers (SFDs). The nonlinear dynamic behavior of the rotor system is studied under misalignment fault condition. The meshing force of the gear coupling is calculated considering the deformation of the tooth caused by torque transmission and dynamic vibration. The contact force between the ball and race is computed based on the Hertzian elastic contact deformation theory and the elastohydrodynamic lubrication theory. The supported force of SFD is simulated by integrating the pressure distribution derived from Reynolds’s equation. The equations of motion are rewritten in non-dimensional differential form, and the fourth-order Runge-Kutta method is employed to solve the nonlinear dynamic equilibrium equations iteratively. To verify the validity of the dynamic model and the correctness of the numerical solution method, the experimental power spectra of the rotor system under various misalignment degrees are compared with the analytical results. The effects of several important parameters, such as the lubrication of the ball bearing, the centralizing spring stiffness, the radial clearance of SFD, and the misalignment of gear coupling, on the dynamic characteristics of the rotor system are investigated and discussed mainly focusing on the system stability. The response spectra, bifurcation diagrams, and Pointcaré maps are analyzed accordingly. These parametric analyses are very helpful in the development of a high-speed rotor system and provide a theoretical reference for the vibration control and optimal design of rotating machinery. 相似文献