变频调速技术在我司水泥生产中的应用

近年来 ,随着电力电子技术与自动控制技术的发展 ,大功率半导体器件变流技术的成熟 ,不少新颖的电动机调速装置进入工矿企业 ,采用变频调速技术对异步电动机进行交流调速控制已被广泛地应用在各个拖动和节能领域中 ,这对节约能源、提高经济效益具有重要意义。在水泥生产中 ,立窑罗茨鼓风机是中小型水泥厂的主要耗电设备之一 ,过去采用异步电动机拖动 ,基本上恒速运转 ,当需要调节风量时 ,实际采用的方法是通过蝶阀放风对风量进行调节 ,这种调节方式当然简便 ,但从节省能源的观点来看 ,不是一种好的控制方法。通常风机是根据生产中可能出现的…     

交流变频调速异步电动机节能计算方法探析

异步电机的电流大小和电机消耗的功率随负载的轻重而改变,利用电磁调速、恒转矩负载等节能方法,对变频异步电动机节能进行了估算,分析采用变频器对交流异步电动机进行调速控制,可以节省可观的电能.     

交流电机应用变频调速节能显著

交流异步电动机变频调速技术是近年来出现的高新技术。山东药用玻璃总厂将这一技术应用于水煤气制造和加压过程,通过微机控制系统的辅助,实现鼓风机按照制气工     

交流变频技术在电力测功机中的应用

介绍了交流变频技术的工作原理、性能特点.同时介绍了变频器及交流异步电动机共同组成的新型高性能交流电力测功机在汽油、柴油发动机台架试验中的使用.     

全数字化高精度交流伺服控制技术(1)

编者按:自1885年交流异步电动机问世以来,它在任何一个国家的生产活动中都占据了重要地位.据统计,世界发电总量的60%被各类电动机所消耗,其中交流异步电动机就占总动力负载中的85%.三相交流异步电动机具有结构简单、牢固耐用、经济可靠、易于组织工业生产等优点,但如何提高其调速性能,尤其是高精度伺服控制方面,长期以来技术上一直未取得根本突破,使得交流异步电动机的应用受到较大的限制.随着微电子、计算机与电力电子功率半导体技术的飞跃发展,对交流异步电动机实现伺服控制成为可能.使传统的交流异步电动机在发挥其固有优势的基础上,大大扩展了自身的应用领域.本刊连载<全数字化高精度交流伺服控制技术>一文.……     

异步电动机变频调速技术

异步电动机在我国工农业生产、交通运输、国防工业及人民日常生活中的应用十分广泛 ,异步电动机与其它各种电机相比具有结构简单、制造方便、运行稳定、价格低廉等特点。但由于异步电动机的调速一直是困扰广大用户的问题 ,在 2 0世纪的大部分时间里 ,电动机只能应用在不变速的拖动系统中 ,而可调速拖动系统则采用直流电动机 ,在很长一段时间这是一个公认的格局。交流调速系统的方案虽然已有多种发明并得到实际应用 ,但其性能却始终无法与直流调速系统相比。但随着近二十年来异步电动机变频调速技术的快速发展与成熟 ,异步电动机的变频调速技…     

交流电动机变频调速器在我厂的应用

<正> 变频调速器,运用80年代最新电控技术,独特的微机程控和大功率晶体管(GTR),在节能、工艺、技术改造等方面取得了很大的成功。变频器与鼠笼型异步电动机相配合,使交流传动系统具备了宽的调速范围,高的稳速精快度。的动态响应以及高的运行可靠性与良好的技术性能。这项技术在国外,特别是在日本、西德、美国等国家,得到了广泛应用。     

为什么要讨论矢量控制和直接转矩控制

矢量控制和直接转矩控制是当前在交流异步电动机高性能变频调速装置中得到广泛应用的两种控制方案.近些年来,这两种方案都在被不断完善,制造出的产品的性能日益优化.从实验到理论探讨这两种方案的特点、优点和弱点,确定它们各自最佳的应用场合,最大限度地发掘交流变频调速技术在不同领域应用中的潜力,有着十分重要的现实意义.……     

游梁式抽油机异步电动机矢量空间节能研究

提出游梁式抽油机异步电动机矢量控制最小励磁电流控制规律，对取得定子电流最小值的方法进行了证明。该节能控制方案不增加系统硬件成本，根据电动机的负载状态对励磁电流进行调节，使定子电流达到最小值，从而达到电动机自身节能的目的。基于MATLAB／SIMULINK仿真软件进行仿真研究，结果表明本文控制方案不仅能使游梁式抽油机异步电动机轻载运行时节能，还使其电磁转矩振荡减小。该控制方法可以推广到一般中小容量异步电动机变频调速系统。     

高效稀土永磁交流同步电动机的应用分析

针对高效稀土永磁交流同步电动机的当前技术发展现状、前景,将其与交流异步电动机在生产实际中的能效及能耗进行改造前后的对比,并进行实际应用效果的分析研究。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.