Small scale wind tunnel for high pressure and high energy discharge

A kind of small scale wind tunnel with low velocity is proposed according to the characteristics of strong ionization discharge chamber and the demands of discharge for flux, velocity and flow fields. On the precondition that the airflow field and velocity is satisfied, aerodynamic design and structural design are carried out. Key techniques are studied including overall structure, aerodynamic and structural design of airflow vent and collection vent, aerodynamic and structural design of power section, flow rate adjustment and control, and cooling system of motor. Based on the design scheme, a small scale wind tunnel with strong ionization discharge for an enterprise is developed. Application indicates that the small scale wind tunnel is a practical and effective airflow loop device for high pressure and strong ionization discharge with the features of stability and reliability.     

Dynamic optimization design of gear transmission system for wind turbine

The differential equation which governs the behavior of the gear transmission system of 1.5 MW wind turbine is established. The external excitation caused by wind speed fluctuation is discussed and the internal excitation due to time varying mesh stiffness and comprehensive error is also analyzed. The calculating formulations of the harmonic balance method of nonlinear dynamic equations are presented. Then, the multi objective dynamic optimization model is developed to minimize the value of vibration acceleration and the overall volume. The optimization of a practical example using mixed discrete combined programming is performed. The result shows that the proposed method of modeling and optimization design can effectively reduce the wind turbines gearbox vibration levels and weight.     

Analysis of reasonable wind farm energy storage capacity range

The wind farm output power fluctuations caused by changing wind speed can be improved by configuring the appropriate storage energy capacity .For the problem that how to select the storage capacity more economical, two indicators for the judgment of the optimization wind power output are mentioned, which is based on a method calculating storage energy capacity. By detailed analysis of the all kinds of factors that can influence the reasonable value of storage capacity, and by using the cost of storage capacity and the smoothing effect of wind farm output as assistant criterion, a reasonable storage capacity range is discussed.     

An improved rotor side control strategy of double fedwind turbine generation system

Based on a on site wind turbine’s output active power vs. generator speed curve, the shortage of conventional power control strategies of doubly fed wind turbine generation system are analyzed. Considering the generator speed restriction and active power fast track control requirement, the power decoupling control strategy in the rotor side converter and variable pitch control strategy are improved, that is, an output mechanical torque of wind turbine and the generator speed of DFIG are used in the rotor side active power control loop in order to achieve an accurate optimal speed control, as well as a direct active power control method is also adopted in the variable pitch control strategy. Finally, the overall operational performances of DFIG wind turbine generation system using the proposed control strategies are simulated, and also compared with the conventional control strategies. The results show that the improved control strategy is more valid and correct.     

Dynamic analysis and optimization of gear trains in a megawatt level wind turbine

Through coupling vibration analysis of the transmission system of a 1.5 MW wind turbine gearbox, a torsional vibration model of a gear drive system in wind turbines is established. The fourth order Runge Kutta integration method is applied to calculate the dynamic response of a gear system caused by wind loads, time varying meshing stiffness, and system damping. The harmonic balance method is used to find the analytic solution. Based on the solution, a mathematical model for optimum gear system design is established. The model aims at minimizing the vibration acceleration of the planet gear and the total mass of the gear transmission system. The optimization toolbox in MATLAB program is adopted to obtain the optimal solution. A calculated example shows that the primary natural frequency of the gear system has been raised, the dynamic properties of the gear train have been improved remarkably, and the total mass of the gear train has been decreased.     

Simulation study of stochastic fluctuating wind field for wind turbine blades

The differences of the wind field model between wind turbines and common architectures are investigated. It is indicated that substantial frequency contents are transferred to rotor rotation frequency and its harmonics due to the periodic motions of blade. According to standard von Karman power spectral density (PSD) model and rotationally sampled PSD model, the PSD matrix for turbulence on blades of wind turbine is setup. The longitudinal turbulence’s time serials is simulated based on the superimposition of harmonic waves.     

Analysis of accelerated fatigue test technology for wind turbines gearbox

In order to satisfy the high reliability requirements of wind turbines gearbox, a method of accelerated fatigue test is proposed to verify the fatigue reliability of the gearbox. According to the design load spectrum, the equivalent load and the number of stress cycles of parts in gearbox are deduced. Based on Miner linear cumulative damage theory, the fatigue degree of the gears and bearings are calculated. A linear accelerated load spectrum with the equivalent fatigue ratio of design load spectrum is provided to check the reliability of the gearbox. The results show that this method can verify the reliability of wind turbine gearbox within about 800 h.     

Analysis of the distorted scaling factor in wind tunnel modeling of power transmission line system

Because of the limitation of the model making and the existing wind tunnel’s size, it is difficult to keep the line and tower in the same scaling factor in developing the aeroelastic model of the power transmission lines system, and a distorted scaling factor is needed in span length of the lines. With the instance of a 1 000 kV two circuit power transmission lines, the finite element analysis under the along wind load in time history is conducted with keeping the tower in the same and the line scaling factor being 1, 0.5 and 0.25 respectively. The results show that the response of the power transmission lines systems keep in the same, and then the wind induced vibration of the distorted model in the wind tunnel test can actually reflect the response of the power transmission lines system under the wind load.     

海南东寨港海桑＋无瓣海桑红树林生态系统防风效应研究

[目的]研究海南东寨港海桑＋无瓣海桑红树林生态系统防风效应。[方法]采用自动气象站对海南东寨港海桑＋无瓣海桑典型人工红树林生态系统的防风效应进行定位观测。[结果]在5min尺度上,平均风速依次为：林后IH（H为平均树高）〈林后4H〈林前1H〈林前4H,林后风速大幅度削减,防风效果明显。旱季和雨季频率最高的风向分别是NNE、NE,林后1H对NNE、NE风的减弱程度较大,分别为34．70％、62．99％。林后1H处不同风速的减弱系数G雨季均远远大于旱季。旱季和雨季半小时平均风速进程均呈“单峰”变化,白昼半小时平均风速远远大于夜晚,白昼半小时平均风速变化急剧,夜晚变化缓慢。5rain风速尺度上,林前1H风速与林前4H风速相关性最好。林前1H处与林后1H处风速正常情况下消减幅度为65．35％～77．21％,而热带风暴期间消减幅度为33．29％～53．21％。[结论】为最合理的红树林造林结构和造林位置提供了理论支持和技术指导。     

抚顺“090621”冰雹多普勒雷达回波特征分析

利用常规气象资料和沈阳多普勒雷达资料,从天气背景、物理量和雷达回波演变特征分析了2009年6月21日抚顺东部地区出现冰雹天气过程的成因。结果表明：此次冰雹天气发生在地面低压带、500hPa冷涡底部东南象限中,500hPa冷涡移动触发低层切变线形成。冰雹发生前大气有不稳定能量和水汽输送条件。850hPa低空冷空气的侵入加剧了大气层结不稳定,促进不稳定能量的释放。产生冰雹天气,高低空急流配合为强对流发展提供了动力条件。多普勒雷达资料表明,强对流天气有多个对流单体组成,发展强盛时有弓形、钩状和V形缺口等特征,强回波区为50～60dBz,最大达67dBz。径向速度有辐合区和逆风区。逆风区出现于冰雹前1h,是冰雹出现的强信号。液态水含量为20～40km／m^2,最大垂直液态水含量为50km／m^2。出现冰雹的对流单体回波顶高9．11km。垂直风廓线。中风向、风速出现较大垂直切变。