Coupled mechanical stress and multi-dimensional CFD analysis for high temperature proton exchange membrane fuel cells (HT-PEMFCs)

We use a combined finite element method (FEM)/computational fluid dynamics (CFD) methodology to numerically investigate the effects of gas diffusion layer (GDL) compression/intrusion on the performance of a phosphoric acid-doped polybenzimidazole (PBI) membrane-based high temperature proton exchange membrane fuel cell (HT-PEMFC). Three-dimensional (3-D) FEM simulations are conducted under various displacement clamping conditions to analyze cell deformation characteristics. Then, a multi-dimensional HT-PEMFC CFD model is applied to the deformed cell geometries to study transport and electrochemical processes during HT-PEMFC operations. Our numerical simulation results reveal that the maximum stresses in the deformed GDLs always occur near the edge of the ribs. The combined effects of GDL compression/intrusion considerably increase spatial non-uniformity in the species and current density distributions, and reduce cell performance.     

Continuous photo-fermentative hydrogen production from lactate and lactate-rich acidified food waste

In the present work, a continuous photo-fermentative hydrogen (H₂) production from lactate was attempted at various hydraulic retention times (HRTs) (48–120 h). Electron balance was made at each operating conditions to elucidate different performances. At 120 h HRT, H₂ production was negligible, while 42% and 52% of substrate electrons diverted towards cell growth and soluble microbial products (SMPs), respectively. After changing HRT to 96 h, H₂ yield jumped to 2.3 mol-H₂/mol-lactate_added with less SMPs production and minimal cell growth. The highest H₂ production rate of 260 mL-H₂/L-fermenter/d was also achieved at 96 h HRT. When HRT was further shortened to 72 and 48 h, H₂ yield dropped to 1.4 and 0.2 mol-H₂/mol-lactate_added, respectively. While almost all of the lactate was degraded at <72 h HRT, only 65% of the lactate was consumed at 48 h HRT. From 200th day, the feedstock was changed to lactate-rich acidified food waste, which was obtained via one-day fermentation of food waste and subsequent centrifugation. At 2 g chemical oxygen demand/L, substrate conversion efficiency reached 35%, which was slightly lower than that of feeding pure lactate. SMPs were found to be mainly consisted of low molecular weight compounds (<500 Da), and the majority of organic matters were aromatic proteins at 120 h HRT and it was shifted to humic-like region in 96 h HRT.     

Directed electrochemical synthesis of ZnO/PDMcT core/shell nanorod arrays with enhanced photoelectrochemical properties

In this paper, we demonstrate a simple two-step electrochemical deposition strategy for synthesizing ZnO/Poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT) core/shell nanorod arrays. The as-synthesized ZnO/PDMcT samples are characterized by Fourier-transform infrared (FTIR), Raman spectroscopy, power X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The ZnO/PDMcT nanorod arrays are found to exhibit significantly enhanced photocurrent density in photoelectrochemical cell applications as compared to the prinstine ZnO nanorod arrays.     

Polynomial Neural Network Approach for Prediction of Liquid Holdup in Horizontal Two-Phase Flow

A new polynomial neural network (PNN) model for estimating liquid holdup in horizontal two-phase flow is proposed in this article. The PNN evolutionally synthesize network size, connectivity, processing element types, and coefficients for globally optimized structure through training. The framework is established using 330 data sets from different experimental conditions. This self-organizing approach automatically presents internal relationships among data in the polynomial forms, and enhances data approximation and explanation capabilities of resulting data-based learning models. The comparative studies with experimental correlations and artificial neural network applications reveal that the model exhibits significant improvement in the processing structure, and outperforms previous models in overall accuracy across liquid holdup ranges.     

THE VALIDATION OF THE ROBUST INPUT ESTIMATION APPROACH TO TWO-DIMENSIONAL INVERSE HEAT CONDUCTION PROBLEMS

A novel adaptive and robust input estimation inverse methodology of estimating the time-varying unknown heat flux, named as the input, on the two active boundaries of a 2-D inverse heat conduction problem is presented. The algorithm includes using the Kalman filter to propose a regression model between the residual innovation and the two thermal unknown boundaries flux through given 2-D heat conduction state-space models and noisy measurement sequence. Based on this regression equation, a recursive least-square estimator (RLSE) weighted by the forgetting factor is proposed to on-line estimate these unknowns. The adaptive and robust weighting technique is essential since unknowns input are time-varied and have unpredictable changing status. In this article, we provide the bandwidth analysis together with bias and variance tests to construct an efficient and robust forgetting factor as the ratio between the standard deviation of measurement and observable bias innovation at each time step. Herein, the unknowns are robustly and adaptively estimated under the system involving measurement noise, process error, and unpredictable change status of time-varying unknowns. The capabilities of the proposed algorithm are demonstrated through the comparison with the conventional input estimation algorithm and validated by two benchmark performance tests in 2-D cases. Results show that the proposed algorithm not only exhibits superior robust capability but also enhances the estimation performance and highly facilitates practical implementation.     

周公宅水库工程引水发电系统取消引水调压室的设计

按规范要求,当水道水力惯性时间常数大于2~4 s时应设置调压室,周公宅水库工程在初设阶段设置了引水调压室,招标、技施阶段通过对发电引水系统布置及调保参数优化,在过渡过程计算和运行条件分析的基础上,取消了引水调压室,取得了一定的效益。介绍了周公宅电站取消引水调压室的论证过程。     

Review of water reuse practices and development in China.

The paper reviews existing urban water reuse schemes in north China including existing policies, institutional, technical and financial practices, summarises the data of nine water reclamation plants in six case study cities, highlights key issues and constraints, and presents development trend in water reuse sector. It is based on an intensive study programme financed by the World Bank in 2004/2005.     

安康水电厂3号发电机推力瓦磨损原因分析及处理

本文介绍了安康水电站３号水轮发电机推力瓦的磨损情况，对推力瓦磨损原因进行了分析，认为磨损是由于瓦中部凸变形引起的，而引起瓦变形的主要因素是热变形。推力瓦的热变形主要是由三个分量组成：瓦体与瓦面线胀系数不同引起的热变形，瓦厚度方向温差引起的热变形和瓦面热变形。叙述了推力瓦磨损处理的步骤和采取的主要措施。经过处理后推力轴承运行情况良好。     

浅谈水电站的生产管理

水电站生产管理事关企业的经济效益和安全生产等重大问题,本文结合实际工作就生产中的运行管理、设备管理、检修维护管理和安全管理四方面进行了一些探讨。     

半悬臂大块模板在乐滩水电站工程的应用

乐滩水电站工程的墩墙混凝土全部使用半悬臂大块模板，模板设计为半刚性。具有自重轻、成本低、提升方便、容易与老混凝土密合可避免漏浆、错台、块与块之间扣接方便等优点，浇筑的混凝土垂直平整、外观质量良好。该文详细地说明了该模板的结构设计、安装提升的要领。