Discharge evaluation from pressure measurements by a genetic algorithm based method

This paper presents an alternative to the Gibson method, for discharge estimation of a turbine inside a hydropower plant. The method proposes a genetic algorithm which includes an integration procedure for the water hammer equations using the method of characteristics. The decision variables are represented by the steady-state regime discharge before the valve closure and the pipe friction factor. The recordings of pressure/differential pressure in measuring sections are used.The method was verified by a numerical experiment and then validated with the measured data in a laboratory experiment at NTNU, Norway.     

Preparation and characterization of a redox-stable Pr0.4Sr0.6Fe0.875Mo0.125O3-δ material as a novel symmetrical electrode for solid oxide cell application

In this work, to simultaneously meet the requirements of good electrochemical performance and redox stability, perovskite oxide Pr_0.4Sr_0.6Fe_0.875Mo_0.125O_3-δ (PSFM) material has been developed as a novel redox-stable electrode for symmetrical cell application. The experimental results obtained by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy show that metallic Fe nanoparticles will exsolve from the parent oxide PSFM through in-situ exsolution method when treating in 97% H₂–3% H₂O atmosphere, and then completely re-incorporate into the parent oxide in air, demonstrating excellent redox stability for PSFM material. In addition, the redox stability in electrochemical performance is also studied by recording the electrochemical impedance spectra and distribution of relaxation times (DRT) analysis. It is demonstrated that a constant electrode polarization resistance (R_p) of ~0.60 Ωcm² is achieved for the symmetrical cell with PSFM electrode in air at 800 °C after activation, and R_p value is significantly increased to 1.59 Ωcm² when exposing the symmetrical cell to 97% H₂–3% H₂O, which is possibly ascribed to the significantly decreased electrical conductivity form 71.0 Scm⁻¹in air to 3.8 Scm⁻¹ in 97% H₂–3% H₂O. Moreover, it is shown that R_p value recorded in air is effectively decreased to ~0.33 Ωcm², and keeps constant during the following 200-h redox stability testing, while R_p value measured in 97% H₂–3% H₂O atmosphere is gradually decreased to 0.82 Ωcm², which can be explained by the enhanced electro-catalytic properties of PSFM electrode induced by the gradually exsolved Fe nanocatalysts from parent PSFM electrode. At the same time, DRT analysis demonstrates that the sub-electrode process including oxygen/hydrogen adsorption, dissociation ionization and surface diffusion to triple phase boundaries occurred at the electrode/electrolyte interfacial is the predominant rate-limiting step, which can be effectively accelerated by surface modification and exsolved Fe nanoparticles. These results indicate that PSFM is a promising symmetrical electrode material for symmetrical cell application because of its good electrochemical performance and excellent long-term redox stability.     

PrBaCo2-xTaxO5+δ based composite materials as cathodes for proton-conducting solid oxide fuel cells with high CO2 resistance

PrBaCo₂O_5+δ (PBC) with high catalytic activity is identified as a prospective cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). However, its poor chemical stability hinders its application. To address this problem, a Ta-doping strategy was presented in this study. The cathode with Ta-doping PBC was applied in proton conducting SOFCs. And the influence of Ta-doping on the crystal structure, electrochemical performance, structure stability and electrical conductivity of PBC was investigated. The resistance to CO₂ of PBC at elevated temperature is significantly improved with Ta-doping. The electrochemical performance measurements indicated that a low Ta-doping concentration did not change the performance of the cells obviously, while large Ta-doping concentration could lower the fuel cell performance.     

Concept design of a novel reformer producing hydrogen for internal combustion engines using fuel decomposition method: Performance evaluation of coated monolith suitable for on-board applications

Hydrogen addition effectively reduces the fuel consumption of spark ignition engines. We propose a new on-board reformer that produces hydrogen at high concentrations and enables multi-mode operations. For the proposed reformer, we employ a catalytic fuel decomposition reaction via a commercial NiO–CaAl₂O₄ catalyst. We explore the physical and chemical aspects of the reforming process using a fixed bed micro-reactor operating at temperatures of 550–700 °C. During reduction, methane is decomposed to form hydrogen and carbon. Carbon formation is critical to hydrogen production, and free space for carbon growth is essential at low temperatures (≤600 °C). We define a new accumulated conversion ratio that quantitatively measures highly transient catalytic decomposition. The free space of the coated monolith clearly aided low-temperature decomposition with negligible pressure drop. The coated substrate is therefore suitable for on-board applications considering that our reformer concept also utilizes the catalytic fuel decomposition reaction.     

Study on the hydrogen storage properties of the dual active metals Ni and Al doped graphene composites

The graphene nanosheets are synthesized by modified Hummer's method, based on which the dual active metals Ni and Al doped graphene composites are prepared through in-suit reaction and self-assembly with high-temperature reduction process. The molecular structure, morphology and specific surface area of graphene nanosheets are characterized systematically. The phase composition, surface morphology and hydrogen storage properties of dual active metals Ni and Al doped graphene composites are further investigated by X-ray diffraction, scanning electron microscopy and gas reaction controller. Results show that the graphene nanosheets have typical graphene feature, whose transparent graphene edges can be observed clearly, and the specific surface area is as high as 604.2 m² g⁻¹. The Ni and Al doped graphene composites are composed with Ni, Al and C phases, which have high hydrogen storage capacity and excellent hydriding/dehydriding stabilities. The maximum hydrogen storage uptake of such composites is up to 5.7 wt% at 473 K, and the dehydriding efficiency is high as 96%∼97% at the dehydriding temperature of 380 K. The hydrogen adsorption and desorption rate control step of the Ni and Al doped graphene composites is complied to the nucleation and two-dimensional growth mechanism.     

高温服役后TP347HFG钢的组织与性能

利用金相显微镜、SEM、EDS和万能试验机分析了过热器管TP347HFG钢高温运行1.2×10⁴ h和7.5×10⁴ h后的组织与性能。结果表明,高温服役1.2×10⁴ h和7.5×10⁴ h后,TP347HFG钢仍保持明显的孪晶特征,析出的NbC有利于保持材料的组织稳定性。TP347HFG钢高温服役后力学性能能够保持稳定,随服役时间增加,强度增加而塑性变化不大。     

Structure,spectroscopic properties and laser performance of Nd:YNbO4 at 1066 nm

We have demonstrated continuous wave (CW) laser operation of Nd:YNbO₄ crystal at 1066 nm for the first time. A maximum output power of 1.12 W with the incident power of 5.0 W is successfully achieved corresponding to an optical-to-optical conversion efficiency of 22.4% and a slope efficiency of 24.0%. The large absorption cross section (8.7 × 10⁻²⁰ cm²) and wide absorption band (6 nm) at around 808 nm indicates the good pumping efficiency by laser diodes (LD). The small emission cross section (29 × 10⁻²⁰ cm²) and relative long lifetime of the ⁴F_3/2 → ⁴I_11/2 transition indicates good energy storage capacity of Nd:YNbO₄. Moreover, the raw materials of Nd:YNbO₄ are stable, thus, it can grow high-quality and large-size by Czochralski (CZ) method. Therefore the Nd:YNbO₄ crystal is a potentially new laser material suitable for LD pumping.     

Anisotropic nanocrystallization of a Zr-based metallic glass induced by Xe ion irradiation

Structural modification in a Zr-based metallic glass caused by irradiation with 7 MeV Xe²⁶⁺ ions was investigated. Needle-like nanocrystalline structures, formed under ion irradiation, consist of Cu₁₀Zr₇ phase (primary) and/or minor (Ni_xCu_1−x)₁₀Zr₇ phase. The formation of needle-like nanocrystals suggested an anisotropic atomic diffusion caused by ion irradiation.     

基于模拟脉动风场的铁路接触网风振响应分析

研究了铁路接触网系统在风载下的动态响应特性.首先,采用ANSYS软件建立了腕臂结构的有限元模型,根据找形理论确定了悬挂系统初始形态.其次,采用谐波合成法模拟了运行现场的脉动风场,并对系统在风载荷作用下的动态响应进行了分析.通过与现场实测数据的对比,分析了接触网系统的风致振动响应特点.     

Data driven approach for fault detection and diagnosis of turbine in thermal power plant using Independent Component Analysis (ICA)

In this paper, a statistical signal processing technique, known as Independent Component Analysis (ICA) for fault detection and diagnosis in the real Turbine system (V94.2 model) is suggested. The information of one of MAPNA’s power plants turbine system is utilized at first. In order to reduce the dimensionality of the data set, to identify the essential variables and to choose the most useful variables, PCA approach is applied. Then, the fault sources are diagnosed by ICA technique. The results indicate that suggested approach can distinguish main factors of abnormality, among many diverse parts of a typical turbine system. The presented results will show that suggested approach can avoid false alarms and fault misdiagnosis due to changes in operation conditions and model uncertainty. The presented results show the validity and effectiveness of ICA approach for faults detection and diagnosis in noisy states.