Iron Loss Analysis of Permanent Magnet Motors Fed by PWM Inverter

Carrier harmonic losses that consist of iron loss, eddy current loss, and ac copper loss are produced in a permanent magnet machine driven by a PWM inverter. It is already known that a higher motor inductance can lead to lower carrier harmonic losses. This paper investigates the carrier harmonic loss composition of two motors with identical dimensions but different inductances. The results of finite element analysis (FEA) showed that the eddy current loss in the iron core accounts for most of the carrier harmonic loss. It is also shown that the carrier harmonic loss of the iron core is quantifiable using theoretical calculations.     

镀锌机组清洗槽刷辊枢轴劣化倾向分析与对策

针对镀锌清洗槽工艺特点,结合生产实际,重点分析了刷辊枢轴装置产生劣化倾向的原因,提出了相应措施并加以实施,提升了清洗槽设备整体工作性能,对提高产品质量产生积极影响。     

Mass loss and flammability of insulation materials used in sandwich panels during the pre‐flashover phase of fire

Nowadays, buildings contain more and more synthetic insulation materials in order to meet the increasing energy‐performance demands. These synthetic insulation materials have a different response to fire. In this study, the mass loss and flammability limits of different sandwich panels and their cores (polyurethane (PUR), polyisocyanurate (PIR) and stone wool) are studied separately by using a specially designed furnace. Expanded polystyrene and extruded polystyrene are tested on their cores only. The research has shown that the actual mass loss of synthetic and stone wool‐based cores is comparable up to 300 °C. From 300 °C onwards, the mass loss of PUR panels is significant higher. The mass losses up to 350 °C are 7%, 29% and 83% for stone wool, PIR and PUR respectively, for the influenced area. Furthermore, delamination can be observed at exposure to temperatures above 250 °C for the synthetic and 350 °C for the mineral wool panels. Delamination occurs due to the degradation of the resin between core and metal panels and the gasification of the (PUR) core. The lower flammability limits have been established experimentally at 9.2% m/m (PUR) and 3.1% m/m (PS). For PUR, an upper limit of 74% was found. For PIR and mineral wool, no flammability limits could be established. Copyright © 2017 John Wiley & Sons, Ltd.     

Performance of supercritical carbon dioxide sprays as coolants and lubricants in representative metalworking operations

This paper investigates the cooling and lubrication properties of supercritical carbon dioxide (scCO₂) sprays as potential substitutes for aqueous emulsions and straight oils used in the metalworking industry today. Sprays of rapidly expanding scCO₂ act to cool and lubricate machining and forming processes by delivering a mixture of dry ice and lubricant deep into the cutting/forming zone. In this work, experiments with turning, milling, drilling, thread cutting, and thread forming were performed with scCO₂ and other metalworking fluids (MWFs) to evaluate their relative performance with respect to tool wear and machining torque. Observations reveal that scCO₂–MWFs are more effective in removing heat from the tool-workpiece interface than conventionally delivered (flood) aqueous MWFs as well as other gas-based MWF sprays. In addition, scCO₂–MWFs delivered in lubricant-expanded phase, where scCO₂ is used to increase volume of lubricant in the spray field, are shown to provide better lubricity than straight oils and oil-in-air minimum quantity lubrication (MQL) sprays. As a result, scCO₂–MWFs can reduce tool wear and improve machining productivity in a wide range of manufacturing operations leading to appreciable improvements in the economics of manufacturing. Also given that CO₂ is a recovered waste gas that is non-toxic, scCO₂–MWFs can improve the environmental and worker health performance of manufacturing operations.     

Supercritical CO2 fractionation of omega-3 lipids from fish by-products: Plant and process design,modeling, economic feasibility

Biopharmaceutical, nutraceutical and food sectors are experiencing an increasing market interest in omega-3 concentrates. Fish and fish processing by-products represent the major source of lipids rich in omega-3. The present work focuses on the supercritical CO₂ fractionation of fish oil derivatives for obtaining omega-3 concentrates, which seems a promising process given that it allows utilizing low temperatures (well below 100 °C) and it can be performed also at industrial scale. The process was conceived, modeled, and evaluated in terms of the main parameters affecting its performances: solvent to feed ratio, reflux ratio, temperature, and pressure of both the fractionation column and the column head separator.The process was further optimized minimizing its operating costs. The optimum foresaw operating the column at high temperature (80 °C) and pressure (19.5 MPa), which allowed for a reduced reflux ratio (=0.92) and solvent to feed ratio (=63). At these conditions, the process cost per unit product (omega-3 concentrate) turned out to be of about 2.3 €/kg.Finally, the plant was designed for three different throughputs: 10, 100, and 300 kg/h. This allowed estimating the investment costs, in order to outline a preliminary process feasibility evaluation.     

Effect of claw disorders on milk production,fertility, and longevity,and their economic impact in Spanish Holstein cows

The aims of this study were (1) to estimate the phenotypic association between different degrees of severity of claw disorders and production, fertility performance, and longevity in Spanish dairy cattle, and (2) to quantify its economic impact at the animal and herd level. In this study, claw data comprised 108,468 trimmings collected between 2012 and 2014 by 25 trimmers from 804 Holstein dairy herds. The claw disorders considered were the 3 most frequent disorders in Spanish dairy herds: dermatitis (DE), sole ulcer (SU), and white line disease (WL). The presence of SU or WL was associated with a significant decrease in milk production and was more important in cows in second or later lactations. A severe lesion of SU or WL lead to twice the milk losses associated with a mild lesion, ranging from 1.47 to 2.66 kg/d of energy-corrected milk. The presence of SU or WL during the early lactation period was associated with more days open, fewer inseminations to get pregnant, and longer calving to first service interval (4.83 and 8.0 d longer due to mild and severe lesions of SU, respectively, and 4.94 and 17.43 d longer due to mild and severe lesions of WL, respectively). The occurrence of a case of SU or WL in first lactation had a significant effect on longevity, with severe lesions reducing up to 71 d of productive life. The cost of a mild lesion ranged from $53 to $232 per affected cow and year, whereas the cost of a severe lesion ranged from $402 to $622 per affected cow and year. The annual costs per cow for DE, SU, and WL were $10.80, $50.9, and $43.2, respectively. An average herd with 64 cows had an extra expenditure of $691/yr due to DE, $3,256/yr due to SU, and $2,765/year due to WL. Milk losses, longer calving intervals, and premature culling contributed to more than half of the costs. Therefore, providing this information to farmers could help decide on strategies to reduce the incidence of claw disorders on the farm.     

Electrochemical corrosion performance of Cr and Al alloy steels using a J55 carbon steel as base alloy

Cr- and Al-modified alloy steels using J55 carbon steel as base alloy were produced by remelting in a vacuum. Their corrosion resistance was estimated by open circuit potential, electrochemical polarisation measurements and immersion tests in a 3.5 wt.% NaCl solution. The modified alloy steels exhibit higher corrosion resistance with a more positive open circuit potential, lower corrosion current density and higher impedance than J55 steel. The immersion tests showed that the new alloy steels have lower corrosion rates and smaller pitting depth than J55 steel and a low-Cr steel.     

Fundamental investigation on nano-precision surface finishing of electroless Ni–P-plated STAVAX steel using magnetic compound fluid slurry

Electroless nickel–phosphorus (Ni–P) plating used in a range of hot embossing metal molds/dies and injection metal molds/dies must be manufactured to nano-precision roughness for proper operation of the molds/dies. We therefore developed a novel polishing technique for mirror surface finishing of this kind of magnetic material using a magnetic compound fluid (MCF) slurry. The effects of the magnetic and gravitational forces acting on the carbonyl iron particles (CIPs) and abrasive particles (APs) within the MCF slurry were studied first, and the behaviors of the CIPs and APs in the presence of an external magnetic field were predicted. Then, experiments were performed to confirm the predictions by investigating the distribution of the CIPs and APs on the working surface of the MCF slurry. Finally, four MCF slurries containing CIPs and APs with different diameters were employed to finish the Ni–P-plated STAVAX steel specimen at different working gaps. The results revealed that for the magnetic workpiece, the resultant vertical force attracted CIPs towards the work surface, whereas APs were pushed away from the work surface. However, the CIPs and APs showed opposite behaviors with the non-magnetic workpiece. The percentage of APs distributed on the working surface increased and the distribution became more even as either the diameter of the CIPs or the working gap increased, whereas that of CIPs had the opposite tendency. The MCF slurry containing bigger CIPs and smaller APs should be employed and the working gap should be set at a smaller value in order to perform mirror surface finishing of a magnetic Ni–P-plated surface. Under the experimental conditions in this work, the Ni–P-plated surface quality improved significantly, and a mirror surface roughness (Ra) of 4 nm was successfully achieved without leaving scratches or particle adhesion when using an MCF slurry containing CIPs 7 μm in diameter and APs 1 μm in diameter, showing that MCF slurries containing commercial CIPs are applicable to the nano-precision finishing of magnetic materials.     

纵向共振法测量粘弹性材料力学参数

(利用虚拟仪器测试系统，对粘弹性材料力学参数进行纵向共振法测量。用激振器产生多周期正弦信号，激励棒状试样纵向振Ivibration and wave ; motorcycle ; transfer characteristic ; analysis ; test动，测量激振器输出端和材料自由端的加速度比值。通过共振频率及共振频率处加速度比的幅值，可以计算样本的杨氏模量和损耗因子。采集信号经过多次时域平均，可在最大程度上提高测试的信噪比。系统的测量结果与商用粘弹性仪结果是一致的。     

Modeling of the mixed potential in hydrogen peroxide-based fuel cells

A one-dimensional mathematical model is developed for the study of the mixed potential associated with the hydrogen peroxide oxidation reaction (HPOR) at the cathode of hydrogen peroxide-based fuel cells. The complicated physicochemical processes, including mass transport, charge transport, and three simultaneous electrochemical reactions (the hydrogen peroxide reduction, hydrogen peroxide oxidation, and oxygen reduction reactions) are considered. The model is experimentally validated and shows good agreement with the literature experimental data. The model is then applied to the study of the mixed potential by varying the current density. It is found that the largest potential loss due to the HPOR occurs under the open-circuit condition (OCC), and the potential loss decreases with the superficial current density. In addition, the numerical results suggest that under the OCC, an increase in the concentrations of hydrogen peroxide and H⁺ ions leads to a decrease in the potential loss, but an increase in the hydrogen peroxide decomposition rate and the oxygen evolution rate.