基于Lyapunov稳定性的风机速度渐近跟踪控制

在风机系统速度控制器设计和闭环系统稳定性分析时,应用李雅普诺夫(Lyapunov)稳定性理论可以有效地提高风机速度控制系统的控制性能。文章基于李雅普诺夫稳定性理论研究了一类转动负载为不确定非线性函数的风机速度控制系统,通过引入辅助变量估计未知参数并应用反步法设计速度控制器,探索了风机速度对于给定参考速度的全局渐近跟踪控制问题。结果表明:基于李雅普诺夫稳定性理论证明了所设计的速度控制器能够实现对任意给定速度的渐近跟踪控制并达到稳定状态;Matlab仿真结果验证了控制算法的有效性,控制方案对风机速度控制系统中存在的未知参数具有良好的稳定性。

转炉干法除尘系统关键控制技术的研究

本文主要介绍了转炉干法除尘蒸发冷却器、静电除尘器、轴流风机、煤气切换站、煤气冷却器等各子系统现有的控制技术和控制难点以及干法除尘各子系统影响转炉吹炼的条件;详细叙述了在干法除尘系统运行过程中蒸发冷却器出口温度控制、转炉煤气泄爆、轴流风机炉口微差压精确控制、煤气回收安全控制等问题以及应对措施;全面详细分析了转炉干法除尘各子系统的控制思路。

纺织空调系统中变频器调速的应用

介绍用变频器调整风机速度 ,改变送风量 ,以达到控制湿度的目的。通过脉宽调制型调速 ,车间设有相对湿度检测传感元件 ,将测得的相对湿度信号传给变送器 ,发出的电信号与代表给定的相对湿度对比 ,把差值传给逆变器的PWM的控制部分 ,通过基极驱动 ,控制逆变器的通断 ,完成变频作用。风机转速随电动机转速变化 ,从而改变送风量 ,使车间相对湿度得到调整。

Numerical simulation investigation on pressure loss of diffusion tank of axial main fan

Based on the engineering application, the angle range of rectifying airflow unit attaching diffusion tank is from 2.5° to 7.5°. In the range of average inlet velocity of 25.0 m/s to 55.0 m/s of diffusion tank, numerical simulations of diffusion tank were done. The results of numerical simulations of diffusion tank are shown as follows： ③ In cases of the inlet velocity range from 25.0 m/s to 55.0 m/s, and the angle range of rectifying airflow unit from 2.5° to 7.5°, the average value of pressure losses decreases to the minimum when the angle is 4.5°.② In cases of the inlet velocity of 35.0 m/s, the pressure loss of diffusion tank decreases to the minimum when the angle of rectifying airflow unit is 5.5°. ③ As far as there are different angles of rectifying airflow unit, pressure loss increases gradually along with the addition of inlet velocity.

Low-Level Jets over Southeast China: The Warm Season Climatology of the Summer of 2003

The southwesterly low-level jet （LLJ） over southeast China in the summer of 2003 is analyzed in this study. The analysis is based on the National Centers for Environmental Prediction （NCEP） Final （FNL） operational global analysis data on 1.0-1.0-degree grids at 6-h intervals. The major criteria for choosing the LLJ ineluded the following： a maximum wind speed equal to or greater than 12.0 m s-1, a wind direction of between 180° and 270°, and the height of wind maximum at 900-700 hPa, not confined to single pressure level. The results show that the LLJs over southeast China dominate at 850 and 800 hPa. These LLJs are closely associated with the topography of this area and tend to locate regions with large terrain gradients, including the northeastern and eastem Yunnan-Guizhou Plateau. Under the influence of mid-latitude westerly winds, the LLJs above 750 hPa move northward to the Yangtze-Huai River Basin. Com- pared to the ten-year （2000-2009） mean climate condi- tions, the LLJs in the warm season of summer 2003 were exceptionally active and strong, as reflected by the posi- tive anomalies of LLJ occurrence numbers and wind speed. In addition, the 2003 LLJs showed strong diurnal variation, especially at pressure levels below 800 hPa. The majority of the LLJs appeared between midnight and the early moming hours （before 8 a.m.）. Finally, the summary of LLJ grid numbers indicates that more than 80% of LLJs in June and July 2003 occurred within the 33-d rainy period. Thus, these LLJs are directly related to the anomalously heavy rainfall in the Yangtze-Huai River Basin.

Dynamic Characteristics Analysis of the Offshore Wind Turbine Blades

The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens.The blades are the key components of offshore wind turbines,and their dynamic characteristics directly determine the effectiveness of offshore wind turbines.With different rotating speeds and blade length,the rotating blades generate various centrifugal stiffening effects.To directly analyze the centrifugal stiffening effect of blades,the Rayleigh energy method (REM) was used to derive the natural frequency equation of the blade,including the centrifugal stiffening effect and the axial force calculation formula.The axial force planes and the first to third order natural frequency planes which vary with the rotating speed and length were calculated in three-dimensional coordinates.The centrifugal stiffening coefficient was introduced to quantitatively study the relationship between the centrifugal stiffening degree and the rotating speed,and then the fundamental frequency correction formula was built based on the rotating speed and the blade length.The analysis results show that the calculation results of the fundamental frequency correction formula agree with the theoretical calculation results.The error of calculation results between them is less than 0.5%.

Wave Power Converter Pendulor with Hybrid H.S.T.

This Pendulor, wave power converter, was invented to be robust towards storms. The key is Hybrid H.S.T. for generator driving by a higher the speed and a smaller the torque of the piston pump which can do over 360 degrees rotation free of the pendulum motion. This idea will bring the non-shock operation to the moving body type wave power conversion and when the Pendulor applies with the antenna principle, it will have a possibility to convert safe and cheap electricity from the ocean by this technology.

Direct Power Control of Variable Wind Speed Based on the Doubly Fed Asynchronous Machine

In this work, the authors propose the study of a wind speed variable based on the DFAM （double fed asynchronous machine）. The model of the turbine is drawn from the classical equations describing the operation of a variable wind speed. The torque generated by the turbine is applied to the DFAM directly connected on the network side and the stator via a bidirectional converter side rotor. This configuration allows velocity variations of ±30% around the synchronous speed and the converter is then sized to one third of the rated power of the machine. The DFAM is controlled by a control vector ensuring operation of the wind turbine power coefficient maximum.

Study of a Particular Stack Performance in a Building in Italy

This paper describes a particular stack performance realized in a building （school） at real scale by computation of the wind induced ventilation and a comparison of the stack performance （airflow rate extracted and wind speed） respect to other systems （wind catcher, wind jetter and wind turbine） are also showed. The realization of the system, actually working, shows the synergy between a plant design and installation using traditional energy sources with innovative engineering techniques providing for the use of integrative energy. In this case, the wind action plays an important role for the conditioning of the school, integrating and giving a significant energetic contribution to the air cooling system. The school building （a nursery） has been built in Modena and is actually working.

A Mathematical Model for the Velocity Profile Internally to a Conical Diffuser

The use of diffusers around the horizontal-axis wind turbines has been widely studied since the diffuser improves the power coefficient of the turbine and it is often called DAWTs （diffuser augmented wind turbines）.Turbines using diffuser are called DWATs （Diffuser Augmented Turbines）,and have efficiency bigger than the Betz limit （maximum energy flow extracted = 59.26%）. Thus, this study presents a mathematical model describing the behavior of the velocity profile internally to a diffuser according to the characteristics of flow and geometry of a conical diffuser. The results are compared with experimental data and show good agreement.

The Unsteady Fluctuating Pressure and Velocity in a Cross Flow Fan

This paper investigates the relations between the fluctuating pressure and velocity of the source by means of nu- merical method and sound pressure in the far field obtained with an noise experiment for a novel cross flow fan. The frequency characteristics of the fluctuating pressure and velocity in a cross flow fan are analyzed by means of spectral analysis and wavelet transform. The fluctuating pressures obtained by large eddy simulation on the casing wall are compared with that of experiments and show good agreement. From the spectral analysis of sound source, it is found that the pressure fluctuating peak is correspond with the sound pressure in the far field.

Unsteady Operation of New Type Turbofan Engine with Aerodynamic Torque Converter Reducing Front Fan Speed

It is desired to increase the rotational speed of the core engine of the turbofan so as to get the best efficiency for the next leap of engine technology. The conventional mechanism in which the front fan is directly connected to the output shaft of a core engine, have a limit of increasing the spool speed, because the fan diameter is very large. The authors have proposed a new driving system in which the front fan is driven through the aerodynamic torque converter. The front fan can work at the best performance at slower speed while the core engine runs more efficiently at higher speed. Continuously, this paper discusses the response of the front fan in the unsteady operation of the core engine, accompanying with the internal flow. The system has the acceptable responsibility in the unsteady operation which is very important for the aircrafts.

Study on Blade Surface Flow around Wind Turbine by Using LDV Measurements

This paper has attempted to study a mechanism of three-dimensional flow around a horizontal axis wind turbine(HAWT) rotor blade. An experimental study of the flow phenomenon in the vicinity of the wind turbine blade is a challenging endeavor. In this research, the HAWT model with 2.4 m diameter was tested in the large wind tunnel. The flow around the rotating blade surface was measured simultaneously for three velocity components, and two probes were used for the synchronized measurement of three-dimensional flow components. The local velocity was detected for the single seeding particle measured in the point where three pairs of laser beams intersected. Blade sections of interest in this study are composed of radial positions r/R = 0.3, 0.5 and 0.7. Optimum and low tip speed ratio flow characteristics were also compared. The velocity flow vector, skin friction coefficient and bound circulation were calculated from LDV measurements, and the experimental research showed reasonably and clearly the experimental results.

Interaction between the atmospheric boundary layer and a standalone wind turbine in Gansu—Part I： Field measurement

Experiments and numerical simulations of the wake field behind a horizontal-axis wind turbine are carried out to investigate the interaction between the atmospheric boundary layer and a stand-alone wind turbine. The tested wind turbine（33 k W） has a rotor diameter of 14.8 m and hub height of 15.4 m. An anti-icing digital Sonic wind meter, an atmospheric pressure sensor, and a temperature and humidity sensor are installed in the upstream wind measurement mast. Wake velocity is measured by three US CSAT3 ultrasonic anemometers. To reflect the characteristics of the whole flow field, numerical simulations are performed through large eddy simulation（LES） and with the actuator line model. The experimental results show that the axial velocity deficit rate ranges from 32.18% to 63.22% at the three measuring points. Meanwhile, the time-frequency characteristics of the axial velocities at the left and right measuring points are different. Moreover, the average axial and lateral velocity deficit of the right measuring point is greater than that of the left measuring point. The turbulent kinetic energy（TKE） at the middle and right measuring points exhibit a periodic variation, and the vortex sheet-pass frequency is mostly similar to the rotational frequency of the rotor. However, this feature is not obvious for the left measuring point. Meanwhile, the power spectra of the vertical velocity fluctuation show the slope of-1, and those of lateral and axial velocity fluctuations show slopes of-1 and-5/3, respectively.However, the inertial subranges of axial velocity fluctuation at the left, middle, and right measuring points occur at 4, 7, and7 Hz, respectively. The above conclusion fully illustrates the asymmetry of the left and right measuring points. The experimental data and numerical simulation results collectively indicate that the wake is deflected to the right under the influence of lateral force. Therefore, wake asymmetry can be mainly attributed to the lateral force exerted by the wind turbine on the fluid.

Optimal Operation of Turbo Blowers Serially Connected Using Inlet Vanes

Optimal operation of the turbo blowers having an inlet vane has been studied to understand the blowers' operating performance.To analyze three-dimensional flow field in the turbo blowers serially connected,general analysis code,CFX,is introduced in the present work.SST turbulence model is employed to estimate the eddy viscosity.Throughout the numerical analysis,it is found that the flow rates of the turbo blowers can be controlled at the vane angle between 90 (full open condition) degrees and 60 degrees effectively,because pressure loss rapidly increases below 60 degree of a vane angle.Efficiency also has almost the same values from 90 degrees to 60 degrees of a vane angle.It is noted that the distorted inlet velocity generated in the small vane angle makes performance deterioration of the turbo blowers due to the local leading edge separation and the following non-uniform blade loading.