200MW汽轮机低压转子-轴承系统的非线性动力学分析

采用数值计算方法对实际大型转子-轴承系统的非线性动力学特性进行了研究，计算结果能与现场的运行经验很好地吻合。用有限元法建立了200Mw汽轮机低压转子-轴承系统的非线性振动微分方程。采用Newmark逐步积分法对转子在升、降速过程中的振动响应进行了数值仿真，得到了转子发生油膜失稳的转速和油膜振荡的“惯性迟滞”现象。对转子的重力和不平衡量对系统的油膜涡动和油膜振荡的影响进行了计算和分析。计算得到了转子的振动随转子的偏心距、轴承的长径比、间隙比、润滑油粘度的变化规律，分析结果为定量和定性分析该类机组转子-轴承系统的稳定性提供了参考依据。图15表1参7     

国产200MW汽轮发电机组油膜振荡的现场测试与分析

本文给出3台国产200MW汽轮发电机组发生油膜振荡的实例,分析了发生油膜振荡时所呈现的振动特征.讨论了轴承非线性油膜力对振动的影响,低频振动分量与轴瓦稳定性的关系,以以转子平衡状况与油膜振荡的关系.图4参4     

不同油膜力模型下转子椭圆轴承系统的动力学分析

1引言滑动轴承的非线性油膜力模型是转子-轴承系统非线性动力学分析和研究的关键问题。滑动轴承的油膜力具有强烈的非线性特性,研究转子-椭圆轴承系统的非线性动力学问题关键在于获得椭圆轴承的油膜力模型。其中椭圆轴承的非线性油膜力的计算精度和计算速度将直接影响到转子-轴     

轴承标高对多跨转子-轴承系统非线性稳定性的影响研究

建立了考虑转子-轴承标高与非线性油膜力的多跨转子-轴承系统高维非线性动力学模型。利用固定界面模态综合法对该模型进行降维,采用Newmark逐步积分法对降维后的动力学模型进行数值计算,可得到转子在各种标高情况下发生油膜失稳的转速门槛值和轴承标高变化对系统动力稳定性的影响规律。对200MW汽轮发电机组转子-轴承系统计算分析表明：由于低压转子后轴承的标高抬起,将导致发电机转子前轴承轴颈的失稳转速显著提前,系统的稳定性降低。分析结果从理论上解释了电站200MW汽轮发电机组发电机前轴承处转子易发生油膜失稳的原因,并且证明了本文所提出方法的有效性。     

滑动轴承非线性油膜力模型的对比分析

在转子-轴承系统的非线性动力学分析和设计中,滑动轴承的非线性油膜力模型的选取,将直接影响到非线性动力学分析结果的准确程度.为了搞清选取的非线性油膜力模型的计算结果与直接采有有限差分数值法解Reynolds方程的计算结果究竟有多大差别,对无限短轴承模型、无限长轴承模型、非稳态短轴承模型、基于Poincare变换的滑动轴承非线性油膜力数据库模型与直接采用有限差分数值法解Reynolds方程的计算结果进行了对比分析.通过对比分析表明:这些模型与有限差分数值法解Reynolds方程的计算结果在不同长径比下均存在不同程度的误差.这为进行转子-轴承系统的非线性动力学分析时选取恰当的油膜力模型提供了理论指导.     

轴承-转子系统稳定性实验研究

研究了圆轴承非线性油膜力支承下转子系统动力学特性及稳定性,以及不平衡量及轴承参数对稳定性影响规律.结果显示,适当增大转子不平衡量、减小轴承长径比、降低润滑油黏度、减小轴承间隙会提高转子-轴承系统稳定性.对圆轴承支承下转子-轴承系统动力学特性进行了实验研究,给出了系统油膜失稳规律,验证了理论分析结果,同时验证了提出的模型正确.研究结果为油膜失稳故障预测及防范提供参考.     

横向流体激振力作用下叶轮转子的分岔特性

将离心叶轮转子系统简化为Jeffcott转子,建立了带有支座松动与碰摩耦合故障的不平衡离心叶轮转子在非线性横向流体激振力和非线性轴承油膜力作用下的振动分析模型,并推导了系统的无量纲运动方程.运用数值积分法研究了系统的分岔特性,最后分析了横向流体激振力对含有松动与碰摩的离心叶轮转子系统动力学性能的影响.结果表明:在转速较高时,横向流体激振力对该类转子的分岔特性有较大影响.     

大型水泵滑动轴承油膜刚度对转子动力特性影响

滑动轴承作为大型水泵转子系统的重要支撑,其油膜动力特性对转子系统动力特性有着重要影响.本文从滑动轴承工作原理出发,通过对Reynolds方程进行差分求解,建立了油膜刚度系数的无量纲求解方程.通过数值模拟方法对某水泵转子系统进行研究,分析了其轴承动力特性和转子动力特性.结果表明,交叉刚度kxy和kyx对水泵转子系统稳定性影响较大;滑动轴承刚度系数增大,转子系统临界转速升高,刚性支撑条件下较弹性支撑时临界转速增大34.7％.在大型水泵转子轴承系统设计、制造和运行过程中,应充分考虑轴承刚度对结构稳定性的影响,保证结构的安全稳定运行.     

连续转子轴承系统的非线性动力学行为研究

对一转子轴承系统,采用有限元方法建立了非线性连续转子轴承系统模型,分别采用直接积分法和模态综合法对偏心情况下转子的非线性动力学行为进行了分析,并对两种方法的结果进行比较发现,直接积分法对于求解非线性振动问题更有效。运用简单离散方法对该转子轴承系统进行了分析,其结果与有限元法偏差较大。有限元的分析结果表明,该转子轴承系统的动力学响应为一典型的油膜震荡过程,其非线性动力学运动形式为HOpf分叉。     

大型核电汽轮机推力轴承油膜失稳振动研究

针对某些机型核电汽轮机出现轴向振动与径向振动耦合的现象,采用大型核电汽轮发电机组推力轴承可倾瓦块模型,对运行中油膜失稳引起的自激振动进行了机理分析。通过建立转子轴向运动方程,对某650 MW核电机组启机过程中推力轴承载荷进行了测量,计算得出不同轴向载荷和推力轴承间隙比条件下的油膜刚度和阻尼,并分析了推力轴承油膜失稳引起的转子轴向自激振动的频率特点。结果表明:轴向载荷、转速和油膜阻尼是引起推力轴承可倾瓦块轴向自激振动的主要因素;减小推力轴承间隙和增大润滑油压可以抑制转子轴向自激振动。     

美国战略石油储备补仓和释放策略分析

美国是最早建立战略石油储备的国家之一,自20世纪70年代开始已逐步形成了一套比较完善的战略石油储备决策管理体系。历史数据表明,美国战略石油储备的几次释放和补仓时机都把握得很好,充分发挥了战略石油储备保障国家石油供应安全、平抑国际原油价格的作用。本文系统地介绍和分析了美国战略石油储备几次主要的释放和补仓策略,以期为探讨我国战略石油储备的补仓和释放时机与策略,提供决策信息参考。     

我国经济和社会发展中必须重视石油峰值问题

石油峰值(Peak Oil)是指某一区域(全球、地区、国家、油区等)石油产量的最大值及其来临的时间。世界石油产量到达峰值并不意味着全世界已将石油消耗怠尽,也不意味着人类不可能在地球上再发现新的油田,只是新发现的油田的石油产量越来越无法弥补已开发油田产量的下降,世界石油供应量不可能再增加,不能满足人类日益增长的需求。许多研究表明世界石油产量正在进入峰值平台期,随时都可能出现资源长期短缺的石油危机。我国的石油消费一直以较快的速度增长,石油也许很快成为我国经济发展的瓶颈。本文提出了石油峰值——我国经济和社会发展中必须重视的一个重大问题,希望大家尤其是主管部门和高层决策者充分认识石油峰值的内涵和挑战,高度重视我国面临的潜在的石油危机,认真落实科学发展观、未雨绸缪,提早采取应对策略以实现我国经济社会的可持续发展。     

开发难动用储量保障国家石油安全

保障我国石油安全有多种措施：建立石油储备、发展替代能源、降低能耗、从国外获取稳定的石油供应、加大国内石油资源的勘探开发力度等。其中，加强国内石油资源的勘探开发是最重要的途径。本文针对我国陆上近４０亿ｔ已探明难动用石油地质储量的现实，从国家石油政策、技术进步、开发方式和机制、评价方法和参数等方面论述了促进难动用储量开发，保障国家石油安全的途径。     

我国急需发展石油期货市场

本文从我国石油需求逐年上升、对进口依赖性不断提高以及国际石油市场起伏不定的现实出发,分析论述了我国发展石油期货市场的必要性和可行性,并提出了发展石油期货市场方面的建议。     

Mitigation of maximum world oil production: Shortage scenarios

A framework is developed for planning the mitigation of the oil shortages that will be caused by world oil production reaching a maximum and going into decline. To estimate potential economic impacts, a reasonable relationship between percent decline in world oil supply and percent decline in world GDP was determined to be roughly 1:1. As a limiting case for decline rates, giant fields were examined. Actual oil production from Europe and North America indicated significant periods of relatively flat oil production (plateaus). However, before entering its plateau period, North American oil production went through a sharp peak and steep decline. Examination of a number of future world oil production forecasts showed multi-year rollover/roll-down periods, which represent pseudoplateaus. Consideration of resource nationalism posits an Oil Exporter Withholding Scenario, which could potentially overwhelm all other considerations. Three scenarios for mitigation planning resulted from this analysis: (1) A Best Case, where maximum world oil production is followed by a multi-year plateau before the onset of a monatomic decline rate of 2–5% per year; (2) A Middling Case, where world oil production reaches a maximum, after which it drops into a long-term, 2–5% monotonic annual decline; and finally (3) A Worst Case, where the sharp peak of the Middling Case is degraded by oil exporter withholding, leading to world oil shortages growing potentially more rapidly than 2–5% per year, creating the most dire world economic impacts.     

Feasibility of edible oil vs. non-edible oil vs. waste edible oil as biodiesel feedstock

Biodiesel has high potential as a new and renewable energy source in the future, as a substitution fuel for petroleum-derived diesel and can be used in existing diesel engine without modification. Currently, more than 95% of the world biodiesel is produced from edible oil which is easily available on large scale from the agricultural industry. However, continuous and large-scale production of biodiesel from edible oil without proper planning may cause negative impact to the world, such as depletion of food supply leading to economic imbalance. A possible solution to overcome this problem is to use non-edible oil or waste edible oil (WEO). In this context, the next question that comes in mind would be if the use of non-edible oil overcomes the short-comings of using edible oil. Apart from that, if WEO were to be used, is it sufficient to meet the demand of biodiesel. All these issues will be addressed in this paper by discussing the advantages and disadvantages of using edible oil vs. non-edible vs. WEO as feedstock for biodiesel production. The discussion will cover various aspects ranging from oil composition, oil yield, economics, cultivation requirements, land availability and also the resources availability. Finally, a proposed solution will be presented.     

Factors Affecting the Oil Agglomeration of Sivas-Divriği Uluçayır Lignite

Abstract

In the coal industry, the coal particles need to be decreased to a very fine size because of the need of removing inorganic materials from coal. Oil agglomeration is a kind of coal cleaning technique that is used for separation of organic and inorganic parts of fine sized coal. In this study, the oil agglomeration of Sivas-Divri?i (S-D) Uluçay?r lignite was carried out by using kerosene, diesel oil, fuel oil, poppy oil, and sunflower oil. The amount of bridging oil was varied from 5% to 25% of the amount of lignite. The effect of oil amount, oil type, solid content, agitation rate and time, pH on agglomeration performance was investigated. Maximum recovery value of 98.18% was observed by using poppy oil. In order to investigate the effect of pH on agglomeration NaOH and HCl is added to the slurry in various amounts. It is decided that the best agglomeration condition is obtained at low pH values. The effect of nonionic surface active agent (Igepal-CA 630) on agglomeration is investigated by adding to the slurry and it is observed that the grade is increased with the amount of surface active agent.     

近期石油市场供需形势分析

5月份受SARS疫情影响,国内石油消费需求下降;另一方面,5月以来石油资源增势有所回落,原油及成品油的增幅较之1季度均有不同程度减缓,又加之受国际行情下挫等诸多因素的共同作用,使得国内持续走高的油价大幅下跌。在多方面力量推动下,进入6月以来上述情况有所缓解。通过对近期国内外经济走势的综合分析,认为随着SARS疫情得到有效控制,国内各油品市场油品销售将会有不同程度的提高,市场后期形势趋于回升。     

Performance and emission characteristics of a DI compression ignition engine operated on Honge, Jatropha and sesame oil methyl esters

The high viscosity of vegetable oils leads to problem in pumping and spray characteristics. The inefficient mixing of vegetable oils with air contributes to incomplete combustion. The best way to use vegetable oils as fuel in compression ignition (CI) engines is to convert it into biodiesel. Biodiesel is a methyl or ethyl ester of fatty acids made from vegetable oils (both edible and non-edible) and animal fat. The main resources for biodiesel production can be non-edible oils obtained from plant species such as Pongamia pinnata (Honge oil), Jatropha curcas (Ratanjyot), Hevea brasiliensis (Rubber) and Calophyllum inophyllum (Nagchampa). Biodiesel can be used in its pure form or can be blended with diesel to form different blends. It can be used in CI engines with very little or no engine modifications. This is because it has properties similar to mineral diesel. This paper presents the results of investigations carried out on a single-cylinder, four-stroke, direct-injection, CI engine operated with methyl esters of Honge oil, Jatropha oil and sesame oil. Comparative measures of brake thermal efficiency, smoke opacity, HC, CO, NO_X, ignition delay, combustion duration and heat release rates have been presented and discussed. Engine performance in terms of higher brake thermal efficiency and lower emissions (HC, CO, NO_X) with sesame oil methyl ester operation was observed compared to methyl esters of Honge and Jatropha oil operation.     

对燃油锅炉渣油供油系统的工艺改进

针对渣油特性及其应用过程中易发生的问题,介绍了供油系统的几项有效改进措施。