基于双闭环的电涡流测功机励磁控制系统

介绍了电涡流测功机的组成及工作原理，设计了电流、转矩双闭环控制系统，给出了系统原理框图、励磁电流控制电路和系统软件流程图．用工控机实现转矩的闭环控制，用模拟电路实现励磁电流的闭环控制，并采用脉宽调制技术设计了移相电压隔离电路，实现了弱电与强电的隔离，提高了系统运行的可靠性．实际运行表明，该系统运行稳定，工作可靠，能满足汽车测试的要求．

电涡流分选模型的构建与仿真研究

以固体废弃物资源化中广泛应用的电选设备电涡流分选机为研究对象,并针对以铜、铝等金属为试验对象,对影响分离轨迹的主要因素进行了试验分析和验证。首先建立了电涡流分选的物理和数学模型,接着推导出洛伦兹力的力学方程。最后挑选了形状较为规则的球形和圆柱体等重物料,对分选离轨迹进行了试验验证。通过同理论模拟分离轨迹的对比找出了误差的原因。

汽车底盘测功机关键技术参数的试验研究

通过室内台架模拟汽车性能检测试验研究，提出了汽车底盘测功机的检测能力、滚筒机构、功率吸收能力、功率补偿关键技术参数的要求与测试方法。研究结果表明，滚筒直径应控制在200—530mm范围，并按不同承栽质量给出了推荐值。滚筒中心距设计以承载质量、轮胎直径、安置角为基本依据，主、从动滚筒间的高度差不应大于2mm，第3滚筒高度差允许误差±5％。试验得到了风冷式电涡流机扭矩与转速、电涡流机热衰退的特性曲线，在恒速800r／min的12min满负荷测试条件下，热衰退率不应超过55％。采用滑行法和反拖法对底盘测功机内部损失功率进行了功率补偿比对验证，两种方法的试验结果基本是一致的。

多功能汽车底盘测功机

多功能汽车底盘测功机实现了不同工况不同负载下动力性能的连续测量并且增加了排放的连续测量功能 ,对控制系统和控制方法进行了改进 ,采用经验控制和自适应控制相结合的控制方案。本文在介绍多功能汽车底盘测功机检测控制系统的基础上 ,阐述了该测功机的测量原理及各种工况下汽车动力性能和排放数据的连续测量、电涡流机控制方法等关键技术 ,并给出了测量结果分析。

Formation Mechanism and Characteristics Research of Ball Lightning Based on Vortex Model

The strange characteristics of ball lightning are considered as a question hard to explain. In order to solve the problem, in this paper a complete model of plasma vortex is presented for the ball lightning. By ideal MHD equations, through imposing disturbance to plasma column, the possibility of sausage and kink instability of the lightning channel is analyzed from the perspective the minimum potential energy. The conclusion is that the kink instability （m = 1） is most prone to occur. And when instability occurs, because of the difference of the magnetic field in the twisted area, the magnetic pressure makes the trend further and therefore forming the plasma vortex that may eventually turn into ball lightning if the energy of the vortex is large enough. The existence of the vortex makes ball lightning have a short period of time stability. By the proposed model, the ball lightning features that are hard to understand in the past are explained. In this paper, the reason for bead lightning is also explained from the perspective of the sausage instability.

Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions

This paper proposes an analysis and a direct power control (DPC) design of a wind turbine driven doubly-fed induction generator (DFIG) under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions.

Vibrations measurements for shrouded blades of steam turbines based oneddy current sensors with high frequency response

With the development of power plants towards high power and intelligent operation direction,the vibrations or failures of blades,especially the last stage blades in steam turbines,happen more frequently due to the unstable operating conditions brought by flexible operation.A vibration measuring method for the shrouded blades of a steam turbine based on eddy current sensors with high frequency response is proposed,meeting the requirements of non-contact heath monitoring.The eddy current sensors produce the signals which are related to the area changing of every blade’s shroud resulting from the rotation of stator.Then an improved blade tip timing(BTT)technique is proposed to detect the vibrations of shrouded blades by measuring the arrival time of each area changing signal.A structure of eddy current sensors is developed in steam turbines and an amplitude modulation/demodulation circuit is designed to improve the response bandwidth up to 250 kHz.Vibration tests for the last stage blades of a steam turbine were carried out and the results validate the efficiency of the improved BTT technique and the high frequency response of the eddy current sensors presented.

Alternating Current Response of Two—Dimensional Vortex Lattice with Random Pinning

Using a model of long-range interactions between vortices, we investigate numerically the alternating current (ac) response of two-dimensional vortex lattice with randomly distributed point-like pinning centers. Mode-locking steps are observed in the simulated current-voltages characteristics, and the number of steps increases with the superimposed ac amplitude and frequency. Our results are in good agreement with recent experiments.

Test on Muddy Soil Reinforcement by Negative Pressure and Electro-Osmosis Inside Cover-Bearing-Type Bucket Foundation for Offshore Wind Turbines

Cover-bearing-type bucket foundation for offshore wind turbines has been paid more and more attention due to its low cost and great bearing capacity. In order to ensure the cover-bearing mode, the muddy soil inside the bucket foundation should be reinforced by some soil consolidation methods, such as negative pressure and electro-osmosis. Firstly, tests were conducted to obtain the reasonable current density. Meanwhile, to improve the electro-osmotic speed and effectiveness, other factors such as intermittent power and layout of electrode, were also studied in the tests. Then, the soil reinforcing tests by negative pressure combined with electro-osmosis were performed for the muddy soil consolidation inside the bucket foundation. The results showed that soil reinforcement by negative pressure was quicker and more obvious during the early phase, and electro-osmotic method can affect more range of soil by rational arrangement of electrodes. Compared with negative pressure, the electro-osmotic method was a continuous and relatively slow process of reinforcement, which was complementary to the negative pressure method. The voltage value of electro-osmosis had little effect on the muddy soil reinforcement inside the bucket foundation, and 1.5 A was chosen as the most reasonable current value for scale model testing in the electro-osmotic method.

Building Effects on a Horizontal-Axis Micro Wind Turbine： Experimental and Fluid-Dynamic Analysis

In this work, the efficiency ofa 1 kWp horizontal-axis wind turbine which is installed on the roof of the engineering building at the University of Salento has been evaluated, by means of CFD （computational fluid dynamic） and experimental data. Particularly, the influence of the building on the micro wind turbine performance has been studied and the numerical results （wind velocity fields and turbulence intensity above the building） have been compared with the experimental data collected over a period of three years. The results have shown that horizontal-axis wind turbines suffer from wake effect due to buildings, therefore, best sites in urban area have to be identified by a careful fluid dynamic analysis aimed at evaluating all causes that can reduce significantly the performance of the generator： in fact, building should allow to exploit increased wind intensity, but often this advantage is voided by turbulence phenomena, as in the case under investigation where the measured aerogenerator efficiency is lower than the nominal performance curve. Then, the best site can be found by crossing the contours of wind velocity with the turbulence intensity fields： in this way it is possible to localize an area （best location） where the aerogenerator can give maximum performance.

Connecting Wind Turbine Generator to Distribution Power Grid--A Preload Flow Calculation Stage

A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.

浅谈汽车废气检测加载力的验证方法

现有的稳态工况法检测汽油车和柴油车的废气排放时,其检测结果受底盘测功机的加载负荷影响较大。当加载力减小时,检测废气排放值将减小。如果计算机记录的检测过程原始加载力符合标准规定的加载力,而电涡流机的实际加载力比标准规定的加载力或记录的原始加载力偏小很多,则可判定为虚假检测。为了保证检测的准确性、真实性和客观性,在这里和大家探讨一种快速、准确验证加载力真实性的方法。

2004年度汽车维修与检测设备产品检验公报(第五号)

2004年通过本中心产品检验的汽车维修、检测、诊断设备产品共12类24种,符合相关的产品标准和计量检定规程(具体产品名称、型号等见表1),现予以公布,并接受行业管理部门和社会对公布产品的监督,监督电话:010-62079186,010-62079180。

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.

Effects of Chemical Reaction Caused by Cooling Stream on Film Cooling Effectiveness

With the increase of inlet temperature of gas turbines, the benefits by using the conventional methods are likely to approach their limits. Therefore, it is essential to study novel film cooling methods for surpassing these current limits. Based on the theory of heat transfer enhancement, a film cooling method with chemical reaction by cool- ing stream is proposed. In order to test the feasibility of the proposed method, numerical simulations have been conducted. The classic flat plate structure with a 30 degree hole is used for the simulation. In the present study, the effects of the parameters in relation to the chemical reaction on film cooling effectiveness, such as chemical heat sink, volume changes, and reaction rate, are investigated numerically. The conventional film cooling is also calculated for the comparison. The results show that film cooling effectiveness is improved obviously due to the chemical reaction, and the reaction heat and reaction rate of cooling stream have an important effect on film ef- fectiveness. However, the effect of volume changes can be ignored.

Numerical Study of Combining Steady Vortex Generator Jets and Deflected Trailing Edge to Reduce the Blade Numbers of Low Pressure Turbine Stage

A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge(VGJs-DT) to decrease the low pressure turbine(LPT) blade numbers was presented.The effects of VGJs-DT on energy loss and flow of low solidity low pressure turbine(LSLPT) cascades were studied.VGJs-DT was found to decrease the energy loss of LSLPT cascade and increase the flow turning angle.VGJs-DT decreased the solidity by 12.5%without a significant increase in energy loss.VGJs-DT was more effective than steady VGJs.VGJs-DT decreased the energy loss and increased the flow angle of the LSLPT cascade with steady VGJs.VGJs-DT can use 50%less mass flow than steady VGJs to inhibit the flow separation in the LSLPT cascade.The deflected trailing edge enhanced the ability of steady VGJs to resist flow separation.Overall,VGJs-DT can be used to control flow separation in LPT cascade and reduce the blade numbers of low pressure turbine stage.