A laser-based machine vision measurement system for laser forming

Laser forming continues to be a promising technology in manufacturing due to its fast speed, flexibility, and low-cost. Measurement of deformation after laser forming is widely needed to verify its convergence to the intended shape in academic research. With the development of laser forming, high requirements on the measurement of the deformed work-piece have been sought such as a 3D profile of the deformed surface, a large measuring range, and measuring convenience. In this paper, a laser-based machine vision measurement system was developed to measure the 3D profile of deformed surface by a one-off scanning process. Based on the 3D profile data, the vertical displacement of the deformed plate was calculated for bending analysis. In addition, as one of the important feature parameters, transverse shrinkage was automatically determined through a novel image-based method during the scanning process. A measuring accuracy of 0.03 mm for vertical displacement measurement and 0.0125 mm for transverse shrinkage were achieved in the developed measurement system. This measurement performance is acceptable in most of the laser forming processes currently studied.     

基于ARM的风电齿轮箱振动监测系统设计

提出一种基于ARM的风电机组齿轮箱振动监测系统,采用ARM微控制器为核心器件,通过对外围设备的控制,完成模拟信号的AD采样、数据传输、数据显示以及数据存储管理等功能,能够实现对风电机组齿轮箱系统进行状态预测,提前预知齿轮箱设备故障,减少故障停机所造成的经济损失。     

Reduction of dust deposition in air-cooled condensers in thermal power plants by Ni–P-based coatings

Clean Technologies and Environmental Policy - One of the largest problems with most current thermal power plants is the cooling efficiency. This paper aims to massively reduce fuel consumption and...     

翅片式换热器管束磨损问题的数值模拟

针对火力发电厂中燃煤锅炉的换热器由于烟气的长期冲刷发生磨损,讨论了颗粒子直径吐、翅片相对高度h／d,以及翅片数目N对翅片管的防磨效果的影响,采用FLUENT软件,对翅片管气相流场和气固两相流进行模拟分析并对颗粒轨迹进行对比。结果表明：翅片数目、N和翅片相对高度、h／d对翅片管附近流场及后面的尾迹区影响很大。颗粒直径越大对翅片管的磨损越严重。     

A new trajectory sensitivity approach for computations of critical parameters

An approach is proposed to assess critical parameters in power system through an evaluation of trajectory sensitivity factors, such as fault critical clearing time (CCT), stability limit generation of generator. Firstly, new formulations for analysis of trajectory sensitivity with respect to fault clearing time are developed. And then, an approach to map the trajectory sensitivity to a sensitivity factor of minimum corrected kinetic energy to fault clearing time is introduced. Directed by the sensitivity factor, CCTs of contingencies are evaluated through an iterative process. It is the advantage that the CCT approach can be used for power systems represented by complex models. Combined with α sensitivity, similar technique can be used to compute generation limit of generators. Case studies for both CCT and generation limit assessments are performed on the 10-generator New England test system to verify the effectiveness and accuracy of the approach.     

Vibration failure in admission pipe of a steam turbine due to flow instability

High vibrations in admission piping of a steam turbine were analyzed. Vibration failure was detected after piping modification as part of upgrading a 300 MW power turbine plant searching for 10% power increment. However, after 1 year operation a vibration malfunction was detected in control valve and fittings of income piping with risk of cracking for maximum output. A study of computational fluid dynamics (CFD) revealed large steam flow instabilities produced by recirculation and high velocity exceeding a critical point. Measurements of natural frequency piping system with the turbine stall and subsequent measurements of frequency and vibration analysis during turbine operation indicated that recirculating flow plays a main role in the vibration problem by resonance. The paper discusses CFD results obtained with a proposed pipe configuration that reduces turbulence effects. Combined pressure slide and diameter increment in piping lead to reduced vibration turbine operation.     

Pyrolysis of asphalt in the presence and absence of water

The bitumen used for the embedding of nuclear wastes has been pyrolysed in confined and hydrous systems, in order to evaluate while an elevation of the temperature in the deep geological repository could induce chemical transformations of the bitumen matrix, which could influence its confining properties. The pyrolysates have been extracted in chloroform and the extract has been separated in aliphatic and aromatic hydrocarbons, resins and asphaltenes. These different fractions have been analyzed by GC-MS and μ-IRTF. Few modifications of the bitumen structure are observed up to 300 °C. Above this temperature, the pyrolysis of the bitumen generates light hydrocarbons and an aromatic and condensed insoluble residue. The use of the time–temperature index allows to estimate the temperatures which have to be reached in the repository in order to observe the first transformations of the bitumen.     

Numerical study on the spontaneous condensation flow in an air cryogenic turbo-expander using equilibrium and non-equilibrium models

The difficulty of data measurement in cryogenic environments and the complicated mechanism of nucleation process have restricted the design of wet type turbo-expander for cryogenic liquid plants. In this paper, equilibrium and non-equilibrium models are used to model the spontaneous condensation flow in a cryogenic turbo-expander along the main stream passage including nozzle, impeller and diffuser. The comparison shows a distinct difference of the predicted wetness fraction distribution along the streamline between the equilibrium model and the non-equilibrium model. In non-equilibrium model, the distributions of supercooling and nucleation rate along the length of turbo-expander are given for the analysis of flow characteristics. The comparison of outlet wetness fraction with the experimental data is also provided for verification and discussion. Both the effects of the rotation on nucleation and the effects of the nucleation on flow along suction side of the impeller are investigated.     

CFB-FGD脱硫塔密相区固体颗粒径向运动特性研究

针对循环流化床烟气脱硫(circulating fluid bed-flue gas desulfurization,CFB-FGD)过程中遇到的塔内黏壁问题,搭建烟气循环流化床冷态实验台,根据相似理论进行模化试验研究.采用粒子图像测速技术(particle image velocimetry,PIV)对导流板前给料、单侧给料和双侧给料3种不同布置方式下脱硫塔内反应密相区脱硫剂颗粒的径向速度和加速度进行研究,以分析不同给料方式下固体颗粒对脱硫塔壁的冲击和黏附状况.实验结果表明,在双侧给料工况下,固体颗粒的冲壁程度最小,有利于改善塔内黏壁的问题,减少壁面上脱硫灰结垢和给料口积灰,保持脱硫系统稳定运行.