变频调速的控制方式的研究

本文介绍了变频调速系统的工作原理和控制要点,对常见的4种控制方式进行了比较,指出了其优缺点和不同的应用场合.为实际工程中变频器的使用及其控制方式的选择提供了借鉴.     

基于人工神经网络的机车当量模型的研究

研究了当前我国机车检修的现状,在传统的机务检修基础上建立了机车当量公里的模型,将机车运行过程中的公里量、负荷量和时间量通过人工神经网络训练进行学习,形成了一种确定机车检修周期的新方法,解决了确定我国铁路机车检修周期问题。     

基于ANSYS的连杆的三维有限元分析

用有限元软件ANSYS对某军用发动机连杆进行了三维有限元分析,确定了连杆的最大应力部位和疲劳安全系数,为此发动机连杆的可靠性设计提供了依据.     

柴油机的燃油对动力性的影响及校正

本文从试验研究出发,阐述了柴油机燃油温度、燃油种类等对柴油机动力性的影响。参照SAE的方法提出了柴油机校正方式,并校验了校正方式的准确性及分析了使用柴油校正的必要性。     

中国城市噪声污染的危害及控制技术的探讨

概述了噪声污染的主要来源,分析了其主要危害,并详细探讨了控制噪声污染的一些先进技术,希望为城市噪声污染的控制与规划提供借鉴.     

应用于南极中山站的光伏支架的研究

针对南极中山站的极端环境条件,研究了低温环境和光伏方阵间距对光伏方阵受风荷载的影响,在此基础上确定了整个光伏发电系统光伏阵列的布局方案;然后结合光伏阵列的布局设计和风荷载分析结果,建立了光伏支架的力学分析模型,研究了多种光伏支架钢结构和底座的技术方案,优化了钢结构和底座的关键技术参数。     

基于超级电容的并联混合动力轿车的开发

采用基于超级电容的方案开发了单轴并联式混合动力轿车,设计了发动机管理系统、全浮式ISG电机、电控双离合器、电控双驱动空调等多项核心技术.研究了混合动力轿车系统的控制策略,优化了发动机和电机的扭矩分配,实现了节能和降低排放.对纯发动机电控系统的标定匹配试验,排放达到了欧-Ⅲ标准;对混合动力系统的起动和怠速优化试验,实现了混合动力的起动控制参数的优化匹配,降低了起动污染物的排放,提高了燃油的经济性.     

基于VC++的旋转机械故障诊断系统的研究

针对中电投东北分公司各汽轮机组远程故障诊断的研究,设计并开发了诊断系统。先从理论上对振动信号的特征参数作了分析,阐述了模糊诊断的理论和应用方法,然后根据各特征参数的计算方法介绍了构建该系统的过程。最后利用该软件分析处理电厂实测数据,包括绘制谱图和故障诊断,取得了良好的效果。     

澳大利亚的水蓝色记忆 无与伦比的美丽

两年多前曾经到澳大利亚旅游了一个半月,虽然去了许多地方,但总觉得意犹未尽。今年,我又再度来到了这个美丽的国家,开始了这场回味无穷的自驾旅游。澳大利亚地广人稀,跟旅游团走只能到达一些交通便利的大众景点,如果想深度地了解和感受这个美丽的国家,自驾游是最理想的选择。     

城市地质灾害的类型和防范方法的研究

中国是世界上地质灾害最严重的国家之一,每年因地质灾害造成的直接经济损失占自然灾害总损失的20%以上,直接影响了人民的生活,制约了社会的可持续发展。在地质灾害的基础上,叙述了中国主要地质灾害的规模、诱发因素、发育分布等特征,评价了地质灾害的发育程度,研究了城市地质灾害的防范方法。     

Heat transfer enhancement through control of thermal dispersion effects

Heat transfer enhancements are investigated inside channels by controlling thermal dispersion effects inside the fluid. Different distributions for the dispersive elements such as nanoparticles or flexible hairy fins extending from the channel plates are considered. Energy equations for different fluid regions are dimensionalized and solved analytically and numerically. The boundary arrangement and the exponential distribution for the dispersive elements are found to produce enhancements in heat transfer compared to the case with a uniform distribution for the dispersive elements. The presence of the dispersive elements in the core region does not affect the heat transfer rate. Moreover, the maximum Nusselt number for analyzed distributions of the dispersive elements are found to be 21% higher than that with uniformly distributed dispersive elements for a uniform flow. On the other hand, the parabolic velocity profile is found to produce a maximum Nusselt number that is 12% higher than that with uniformly distributed dispersive elements for the boundary arrangement. The distribution of the dispersive elements that maximizes the heat transfer is governed by the flow and thermal conditions plus the properties of the dispersive elements. Results in this work point towards preparation of super nanofluids or super dispersive media with enhanced cooling characteristics.     

Thermodynamics of chemical references for exergy analysis

Exergy references for chemical elements have been discussed in specialized literature for a long time, but so far these data are not included in standard handbooks. One reason is that the development of the reference system took place over many years in a rather small group of scientists; their ideas are still dominant today. Some assumptions and procedures are quite unusual from a thermodynamic point of view. Examples are discussed and suggestions are given to improve the situation. Very low concentrations of elements in the atmosphere and oceans and the abundance of elements in the earth’s crust (Clarke number) are no longer used in determining reference states for chemical elements. Thermodynamic theory shows that generally liquid and gas mixtures are not useful as reference states. A generalized air-like gas is used to get reference states for the first few elements. For all other elements well defined data of pure compound from thermodynamic tables are used to develop the reference system in successive approximations. Linear optimization is used in all steps to minimize the sum of exergy values of the elements. It is shown that the allocation of reference materials to elements can be done in a logic procedure not requiring assumptions. It is also shown that this allocation procedure is unnecessary once the set of exergy values for elements is established. The values obtained are reported for 90 elements. The use of a generalized composition of air is the only aspect that reminds to the original set-up of the reference system. Otherwise the procedure is strict thermodynamics. The procedure might be used to develop a standard list of exergy values of chemical elements.     

Nodal integral method for convection-diffusion transport using linear and higher order quadrilateral elements

Abstract

Generic nodal integral method (NIM) based scheme, utilizing nine noded 2D quadratic elements along with four noded 2D linear elements, is developed to solve the fluid flow and heat transfer equations in complex geometries. Non-linear (quadratic) quadrilateral elements are used for discretization of boundary region and linear quadrilateral elements are used for interior region. Lagrange interpolation functions are used to map both type of elements to corresponding square computational elements. The scheme for Neumann and mixed type of boundary conditions are also developed for quadratic elements. C¹ type continuity condition is imposed at the interfaces of adjacent elements. Numerical results are compared with analytical solutions for diffusion and advection-diffusion equations. Results for Navier–Stokes equations in curved domain are compared with previously reported experimental as well as numerical results. The comparative study has also been done between presently developed scheme using quadratic and linear elements (referred as scheme-1) and scheme based on complete discretization with linear elements (referred as scheme-2). The comparison shows that both the schemes are of nearly second order accurate while the scheme-1 is more accurate than scheme-2. The results show that the efficient mapping of curved surface with quadratic elements improves the accuracy of NIM schemes.     

Element differential method with the simplest quadrilateral and hexahedron quadratic elements for solving heat conduction problems

In this article, two types of new quadrilateral and hexahedron quadratic isoparametric elements are proposed for the element differential method (EDM) for solving heat conduction problems. These elements, called as the Ultra elements, have the minimum numbers of nodes comparing with the existing elements and have the feature that a central node is included inside them, which is necessary for the EDM analysis. The EDM is a strong-form method, which does not require control volumes and any integration. In the previous EDM for solving heat conduction problems, the Lagrange elements were used, which had many elemental nodes. The proposed new types of elements can circumvent this deficiency, in which only a few nodes are required. The shape functions for these elements are constructed for the first time, and the first and the second order derivatives of the shape functions with respect to intrinsic and global coordinates are analytically derived. Several 2D and 3D numerical examples are given to demonstrate the effectiveness, the accuracy and the efficiency of the newly proposed elements for the EDM for solving heat conduction problems.     

回转式空气预热器蓄热元件传热特性实验研究

回转式空气预热器热力性能主要取决于蓄热元件,在蓄热元件传热特性试验台上,通过分段均匀电加热蓄热元件模拟其在锅炉烟道中的温度并控制其在不同的温度水平上,对不同蓄热元件板形在不同壁温、不同雷诺数下传热特性进行了比较试验,并对结果做出了简要分析.     

燃煤过程有害微量元素挥发与其赋存状态及燃烧温度的关系

煤在燃烧过程中，部分微量元素从燃烧炉中挥发，进入大气，污染环境，分析了有害微量元素挥发性与燃烧温度、有害微量元素赋存状态之间的关系，通过不同温度下煤的燃烧实验及其微量元素挥发性计算，得出燃烧过程中有害微量元素的挥发性受燃烧条件的制约，温度越高，则其挥发性越高；微量元素的挥发性与其在煤中的存在状态有密切的关系，以有机质存在的有害微量元素，在燃烧时，其结构分子易被破坏且易挥发，以无机态结合的微量金属元素的挥发性较弱。     

Pre-combustion removal possibility of hazardous trace elements from Indian high-ash coal by coal preparation technologies

Many of the potentially hazardous air pollutants listed in the 1990 Clean Air Act are elements commonly found in trace amounts in coal. When coal is burned, these elements release into the environment. An option for controlling the release of these elements into the atmosphere is to remove them before combustion. Conventional physical coal cleaning processes are effective in reducing the concentration of many of these trace elements in coal. In addition, advanced cleaning processes directed toward reduction of various elements may perform better than conventional processes. Therefore, current research focuses on the advanced coal cleaning technology which is directed toward reduction of mineral matter and various toxics elements as well. Results of recent studies indicate that the degree to which a specific trace element can be reduced by coal cleaning depends on its distribution in the coal. To quantify the capabilities of a gravity-based coal cleaning process for removing these hazardous air pollutants, a detail study was conducted on a coal sample collected from one mine of Talcher area. Careful analysis of the experimental data indicates that most of the trace elements of greatest environmental concern are strongly associated with the organic matter of the investigated coal, thus during beneficiation these elements are concentrated in the clean coal fraction. Therefore, it makes the situation more complex and the expected pre-combustion removal of these trace elements seems to be not possible for the high-ash non-coking coals of Talcher coal field.     

Physiochemical and leaching characteristics of fly and bottom ash

Bottom ash and fly ash are the by-products of coal in thermal power plants. They are the combustion wastes and contain many elements that may harmful to the environment. The present study investigates the physiochemical, mineral, and leaching characteristics of an Indian coal ash (bottom ash and fly ash). From the characterization of bottom ash and fly ash, it is found that the ash samples are enriched predominantly in silica, alumina, and iron oxides. A series of leaching experiments have been performed to analyze the tracing elements of metal at the different liquid to solid ratio (L/S). The L/S varies from 20:1 to 80:1. From the leaching results of the fly ash and bottom ash data, it is observed that the tracing elements of Mn, Mg, Cr, Zn, Ni, Pb, Fe, and Cu are the most abundant elements, while Hg, Mo, and Co are the least abundant elements.     

煤气化过程中微量元素挥发动力学

煤气化过程中,与矿物质有关的微量元素挥发时包含3个连续步骤:微量元素在熔化的矿物质内部质量扩散;微量元素在矿物质熔化表面挥发,以及逆反应凝聚过程;气态微量元素在灰尘中扩散.不同微量元素的挥发过程由上述3个不同步骤控制.数学模型计算结果表明,饱和蒸气压力较小的元素(如Co、Cr、Cu、Mn、Ni、V、Sr、Mg和Pb等)挥发速率常数主要由熔融矿物质表面微量元素挥发和熔融矿物质内微量元素质量扩散共同控制;饱和蒸气压力较大的元素(如As、Cd、Hg、Se、Zn等)挥发速率常数由熔融矿物质内微量元素质量扩散所控制;气化温度对微量元素挥发速率影响很大;所有微量元素挥发速率常数随着气化温度的增加而增加;元素的饱和蒸气压力越大,气化温度对其挥发速率影响也越明显.     

中外石油公司油气勘探开发生产要素投入效率分析

以中国石油、中国石化、中国海油3家国内石油公司以及BP、壳牌等国外石油公司为评价对象,收集其生产经营数据,建立各自的柯布-道格拉斯生产函数,进行资本、劳动力、资源以及科技进步对油气产量贡献水平的测算．以此作为生产要素效率评价的标准。通过对中外石油公司生产要素效率进行比较分析和评价．得出结论：国内石油公司资本产出弹性普遍低于国外公司,国内外石油公司科技进步对油气产量的贡献率比较接近。并以此为基础。提出了有关国内石油公司生产要素投入与管理体制改革的相关建议。