HTS磁浮系统中永磁轨接头处的运行阻力简化分析方法北大核心CSCD

为了研究高温超导磁浮系统中永磁轨接头处磁场分布与运行阻力的变化特性,本文以真空管道HTS磁浮系统为实验平台,以基本的振动理论和电磁学理论为基础,用一种简化方法分析接头气隙长度及运行速度与阻力的关系,然后在真空管道实验系统上实验验证.实验时保持管内一定真空度,驱动磁浮车运行后让其自由运行,测量其速度变化以确定运行一周所耗的能量,然后再计算平均阻力.实验结果与推导表达式所得结果相符,表明了分析过程的合理性与有效性.     

HT-7U装置极向场电源变流系统的研制

介绍了HT-7U极向场电源中所使用的变流系统,提出了一种新的四象限运行控制方法,解决了极向场电源设计和制造的难点。实现了15kA的有环流运行。     

非连续运行工况下结霜动力因素实验分析

冷风机表面在非连续运行工况下结霜是实际运行中经常遇到的问题,其影响因素较为复杂。通过建立结霜实验台,系统分析了影响非连续运行工况下冷风机表面结霜的因素,包括运行比、相对湿度及冷风机表面温度,并且对实验结果总结了关联式。结果表明,在非连续工况中,结霜量是一个与运行比有极大关系的值,而拟合的关联式则体现了这种关系,并与实验结果有较小的误差。     

百米级冷绝缘高温超导电缆系统设计及运行

以富通集团建成的百米级35 kV/1 kA三相交流冷绝缘高温超导电缆为例,详细介绍了超导电缆系统的整体设计,包括各功能组成、并网状态、绝缘测试以及整体运行等情况,通过总结实际运行数据及运行经验,给出了借鉴和参考。该高温超导电缆系统目前已连续运行超过1 450天,运行期间未出现任何异常故障,充分说明了系统设计的合理性。     

从无功功率补偿分析降低电能损耗的措施

电力系统中变压器实现功率转换，需要磁场支持；占用户用电负荷70％以上电动机负荷要正常运行，需无功功率建立磁场．无功功率是电力系统正常运行必需的重要运行参数．     

制冷装置增加夜间运行时间的性能分析

介绍了福建省目前的分时电价政策.基于冷库实例,模拟计算了制冷装置增加夜间运行时间,采用不同蓄冷运行方案的运行费用.结果显示,理想条件下冷库的运行电费可节省47.3%以上,现场调研的某冷库运行电费可减少约31%.根据气象台的逐时气象数据统计,厦门市夜间湿球温度下降1.2～1.8℃.计算表明,制冷装置夜间运行的COP因此比...     

地源热泵的运行特性模拟研究

依据圆柱源理论,建立起了耦合地面热泵机组和地下埋管换热器特性的模拟模型,该模型可用于长期运行的地源热泵系统的短时间步长运行特性模拟。探讨了模拟过程中有关参数的确定方法,并运用所建模型对地源热泵的冬季和夏季运行特性进行了模拟。运行特性模拟与实验数据的验证结果表明,所建模型可以对地源热泵的运行特性做出符合实际的预测。     

连续回热型吸附式空调实际运行与吸附床性能分析

近年来,我们研制了一台连续回热型吸附式空调／热泵,该空调／热泵在１００℃热源驱动下,单位质量制冷功率 ＳＣＰ可达到 １５０ Ｗ／ｋｇ,与此同时 ＣＯＰ达到 ０．４。在系统的实际运行中,吸附床起到了重要的作用。本文介绍了该机组在实际运行中为稳定工况所采取的一系列措施,以及机组运行的实际Ｃｌａｐｅｙｒｏｎ图,着重讨论了系统运行参数对吸附床性能的影响。     

35kV/2kA高温超导电缆系统现场安装、调试和运行缺陷分析

35kV/2kA超导电缆系统的研制,已经完成,并于2004年4月并入云南昆明220kV普吉变电站输电网络正式运行。该文介绍了普吉超导电缆系统现场安装和调试,总结了其运行情况,分析了电缆系统在一个大修周期内的故障和缺陷情况。普吉超导电缆系统现场的安装、调试和运行管理,能够适应电力系统相关规范的要求,在电网的统一调度下,实现安全送电1.6亿度。     

长寿命斯特林制冷机膨胀机无摩擦运行技术

论述了长寿命斯特林制冷机膨胀机的结构,重点对排出器活塞与冷指气缸无接触运行控制方法进行论述.制冷机正在进行加速寿命跑和,运行很好.     

Time-reversed lasing based on one-dimensional gratings

We show that a one-dimensional grating can generally exhibit time-reversed lasing better than a uniform slab. As the effective refractive index of a grating can be controlled by adjusting the geometric parameters, the time-reversed lasing can be realized for any incident wavelength in it. Moreover, the operating frequency range of coherently perfect absorption for a grating structure is remarkably broad compared with a uniform structure. All these behaviors are demonstrated with GaAs/Air gratings illuminated around 794.8 nm$794.8\text{nm}$. The properties of the proposed grating imply the potential applications such as detectors, transducers, and broad band absorber.     

Superconducting Magnet of the Gyrotron for HL-2A ECRH System

In order to carry on ECRH experiments and research on HL-2A tokamak, two sets of 4 mm gyrotrons were imported from GYCOM. Each of them has a superconducting magnet system to offer a required magnetic field configuration. In gyrotron, a strong magnetic field is necessary for electron beam to satisfy the electron cyclotron resonance condition and to excite one the eigemodes in the cavity. Its functions are： （I） to make electrons gyrate, （ 2 ） to offer enough adiabatic compression value to make electrons acquire strong transverse energy. During the period of adjustment, magnetic field distribution was measured. Meanwhile, operating current of superconducting magnet and operating frequency of gyrotron were determined.     

Optimization of Operating Parameters of Plasma Antenna

In this work, the operating parameters of the plasma antenna are optimized using a kinetic model based on Particle in Cell‐Monte Carlo Collisions (PIC‐MCC) method. This optimization study is performed via the investigation of variations in the operating parameters of the plasma antenna, i. e., its dimensions, background gas pressure, and the applied voltage frequency and their consequent effects on the plasma frequency, kinetic energy of electrons and plasma current density of plasma antenna. While the antenna performance is improved at higher tube lengths and applied frequencies, it is optimized at a particular tube radius. Moreover, higher background pressures have increasing effects on the plasma antenna operation. Based on this parametric study, the optimum operating parameters of the plasma antenna are established. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sonodegradation of 17α-ethynylestradiol in environmentally relevant matrices: laboratory-scale kinetic studies

The sonochemical degradation of 17α-ethynylestradiol (EE2) in secondary treated effluents was investigated. Ultrasound irradiation was provided by a horn-type sonicator operating at 80 kHz. The effect of various operating conditions such as estrogen concentration (25-160 μg/L), power density (18-46 W/L), liquid bulk temperature (15-60 °C), gas sparging (air, oxygen, and helium), solution pH (3 and 7.8), as well as the addition of radical promoters (hydrogen peroxide) or catalysts (TiO₂ and Fe²⁺) on degradation kinetics was evaluated. Changes in estrogen concentration were followed by high performance liquid chromatography and the yeast estrogen screening (YES) assay. EE2 degradation in the range 25-110 μg/L follows first order kinetics in regard to its concentration, while lower order kinetics occur at higher concentrations. The reaction rate increases linearly with applied power and decreases exponentially with temperature at the conditions in question. Continuous sparging of air or oxygen has little effect on the kinetics relative to air-equilibrated conditions, while helium has a marginally positive effect. The inorganic and organic contents of the wastewater matrix appear to promote degradation at inherent conditions in comparison to experiments in ultrapure water. Nevertheless, the addition of H₂O₂ (8.6 and 86 mg/L), Fe²⁺ (2.5-25 mg/L) or TiO₂ (50-2000 mg/L) has no or, in some cases, adverse effect on kinetics.     

Ultrasound assisted intensification of biodiesel production using enzymatic interesterification

Ultrasound assisted intensification of synthesis of biodiesel from waste cooking oil using methyl acetate and immobilized lipase obtained from Thermomyces lanuginosus (Lipozyme TLIM) as a catalyst has been investigated in the present work. The reaction has also been investigated using the conventional approach based on stirring so as to establish the beneficial effects obtained due to the use of ultrasound. Effect of operating conditions such as reactant molar ratio (oil and methyl acetate), temperature and enzyme loading on the yield of biodiesel has been investigated. Optimum conditions for the conventional approach (without ultrasound) were established as reactant molar ratio of 1:12 (oil:methyl acetate), enzyme loading of 6% (w/v), temperature of 40 °C and reaction time of 24 h and under these conditions, 90.1% biodiesel yield was obtained. The optimum conditions for the ultrasound assisted approach were oil to methyl acetate molar ratio of 1:9, enzyme loading of 3% (w/v), and reaction time of 3 h and the biodiesel yield obtained under these conditions was 96.1%. Use of ultrasound resulted in significant reduction in the reaction time with higher yields and lower requirement of the enzyme loading. The obtained results have clearly established that ultrasound assisted interesterification was a fast and efficient approach for biodiesel production giving significant benefits, which can help in reducing the costs of production. Reusability studies for the enzyme were also performed but it was observed that reuse of the catalyst under the optimum experimental condition resulted in reduced enzyme activity and biodiesel yield.     

水源制冷机房单位冷量能耗的影响参数分析

为了降低空调能耗,文中以水源制冷机房为模型,分析了影响制冷机房总能耗的主要运行参数,然后采用正交试验法对制冷机房在不同参数条件下的能耗进行了模拟,找到了各运行参数影响制冷机房总能耗和单位冷量能耗的主次顺序及基本规律。     

Improvements in heat transfer in thermal desalination operation based on removal of salts using ultrasound pretreatment

Scaling is a major problem in the thermal desalination operation which is mainly attributed to the deposition of salts on the tube, thereby increasing the resistance to heat transfer. To reduce or prevent the formation of scale on heat transfer surfaces, treating desalination concentrates and precipitating sparingly soluble salts can be a promising method. In the present work, the effect of ultrasound pretreatment to the synthetically prepared sea water as desalination feed has been investigated with an objective of intensifying salt removal process and avoiding scale formation leading to better heat transfer rates. A lab scale double pipe heat exchanger setup was designed and operated under simulated conditions of the thermal desalination operation. Total operational volume of 2000 ml was used for all experiments with a fixed flow rate of 5 ml/s. To understand the process of scaling, synthetic seawater was prepared as per the ASTM D 1141-98 and was used for scale deposition experiments. The experiments conducted using untreated synthetic seawater confirmed substantial scaling and drop in the heat transfer coefficient from an initial value of 776 W/m² K to 603 W/m² K (about 22%) after 24 h operation as compared to deionized water. SEM-EDX analysis was performed to investigate the morphology and main components of the scale. Subsequently, synthetic seawater was treated with ultrasound under continuous flow condition for removal of salts responsible for scaling. It was demonstrated that pretreatment resulted into salt crystallization, after which, the crystals were separated and the filtered solution was passed through the heat exchanger to check the effects on heat transfer rate. It was confirmed that the heat transfer rate was found to be higher with a value of 797 W/m² K. Overall an effective approach based on ultrasound to remove the scale forming components has been demonstrated with established best conditions as 70% amplitude for 30 min of irradiation at fixed frequency of 20 kHz and 50% duty cycle.     

Intensification of heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction using ultrasound: Understanding effect of operating parameters

Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction is a significant reaction for obtaining industrially important products. The current research work deals with intensification of reaction of 4-bromoanisole and phenylboronic acid catalyzed with 5 wt% Pd/C (5% by weight Pd supported on C available as commercial catalyst) using ultrasound and more importantly, without use of any additional phase transfer catalyst. Heterogeneous catalyst has been selected in the present work so as to harness the benefits of easy separation and the possible limitations of heterogeneous operation are minimized by introducing ultrasonic irradiations. The effect of operating parameters such as ultrasound power, temperature, catalyst loading and molar ratio on the progress of reaction has been investigated. It has been observed that an optimum power, temperature and catalyst loading exist for maximum benefits whereas higher molar ratio was found to be favourable for the progress of the reaction. Also, the use of ultrasound reduced the reaction time from 70 min required in conventional approach to only 35 min under conditions of frequency of 22 kHz, power dissipation of 40 W and catalyst loading as 1.5 mol% (refers to total quantum of catalyst used in the work) in ethanol-water system under ambient conditions. The work also demonstrated successful results at ten times higher volume as compared to the normally used volumes in the case of simple ultrasonic horn. Overall, the work has successfully demonstrated process intensification benefits obtained due to the use of ultrasound for heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction.     

Operating Parameters Optimization of Miniature Optically Pumped Cavity NH3 Submillimeter Wave Laser

By means of the iteration method, the output power density of the miniature optically pumped NH₃ submillimeter wave (SMMW) laser was calculated based on the density matrix equations of a quantum system. Optimization of operating parameters including operating gas pressure, reflection coefficients of input and output meshes of the laser were studied systematically. In the paper, the concepts of the average activated length and the synthetical optimum value were defined, and some rules of the optimization were explained successfully. Experimentally, a cavity NH₃ SMMW laser that was composed of a pair of inductive metallic meshes and pumped by TEA-CO₂ 10R(8) line was used. The experimental results were in good agreement with our theoretical calculations.     

Calculation of infrared system operating distance by spectral bisection method

During the transmission of infrared radiation, the atmospheric transmittance could be a complex parameter due to the absorbing and scattering of atmosphere, as well as the influences from the environment and transmission distance. With the help of a spectral bisection method, a new assessing formula and solution is raised by calculating the operating distance of infrared system. In the small segments, MODTRAN can be used to figure out the percentage of penetration, which is called by advanced program, so as to get the infrared radiation in those segments. The calculated data of the segments were summed up and used to calculate the operating distance of the infrared system. Compared with the conventional calculation methods that the transmittance was used as a constant or a average, The calculation precise of the operating distance is highly increased by this method the results of all small segments by comparing with the traditional methods. The whole computing process becomes more clear and effective by taking the influences from visibility of atmosphere, altitude, targets zenith angle and spatial frequency into consideration, and by building an instant monitoring system of the operating distance. The final computing result and real effecting distance are based on the general simulation for penetration rate and the tendency of operating distance in all conditions.