在运行中去除凝汽器铜管结垢的新思维

针对火电厂中闭式循环冷却水系统凝汽器铜管结垢的原因,提出采用空心胶球携带水处理剂在运行中改善凝汽器铜管结垢的设想。论述了空心胶球携带水文处理剂运行的阻垢机理以及与此有关的问题。     

提高凝汽器运行可靠性的有效途径——黄岛电厂2号机更换钛管

凝汽器是汽轮发电机组的主要辅机,如何保证凝汽器运行的可靠性,是直接关系汽轮发电机组安全、经济运行的重要因素,而用海水作为冷却介质的海滨电厂,解决凝汽器铜管的泄漏更是广大科技人员普遍关注的热点难题。山东黄岛发电厂位于胶州湾西海岸,一期工程装有两台国产125MW 机组,1、2号机组分别于1980年9月和1981年7月投产。冷却水为海水,开放式循环。凝汽器系上海锅炉厂生产的 N—7000—1型对分双流程表面式凝汽器,采用上海铜管厂制造的 B10铜管,规格为Φ25×1×7565mm。     

凝汽器铜管的联合保护研究

凝汽器铜管的腐蚀与防护一直是令人关心但又未解决好的问题,由于凝汽器运行条件复杂,材质众多及冷却水质的不断恶化,导致其腐蚀形式多种多样,为此,这里探讨了一种凝汽器铜管的联合保护方式,即铜管管端与管板采用涂刷XZ-A增韧防腐胶与阴极保护的方式联合保护,铜管其它部位采用FeSO4镀膜（包括定期补膜）与胶球清洗的方式联合保护。实践证明了这种联合保护能够有效防止凝汽器铜管的腐蚀。     

凝汽器铜管的保护

从电厂凝汽器铜管腐蚀与结垢的现象,分析了循环冷却水水质趋势及钢管腐蚀结垢机理,并针对性地提出了仪化热电厂3号机组凝汽器腐蚀结垢问题的解决办法及今后对电厂凝汽器保护的途径和建设。     

考虑潮汐影响的凝汽器变工况特性及最佳真空

为解决海水直流冷却水系统中因忽略潮汐而带来凝汽器变工况特性与最佳真空求解的不准确性问题,以某电厂2×800 MW机组的海水直流冷却水系统为例,研究了考虑潮汐引起的海水水位变化对冷却水体积流量、机组微增功率和循环水泵耗电功率的影响,完善了凝汽器变工况和最佳真空的数学模型,得到凝汽器变工况特性的计算结果,并对考虑和不考虑潮汐影响2种情况下求解得到的凝汽器最佳真空进行了对比分析.结果表明:潮汐对凝汽器压力影响显著,且随着凝汽器进口水温的升高,这种影响增大;当2种情况下的循环水泵最优运行方式不同时,凝汽器最佳真空也不同,但考虑潮汐影响下的循环水泵最优运行方式总能保证机组在更好的经济效益下运行.     

330MW机组凝汽器改造的数值模拟及性能分析

潍坊电厂330MW机组的凝汽器改造前存在着真空低和水质变差导致铜管泄漏趋势加重的现象,严重地影响了机组的经济性、安全性和带负荷能力。采用TEPEE两山峰形管束布置方式对凝汽器进行改造,利用数值模拟的方法计算了改造后凝汽器壳侧的汽相流动与传热特性,并用改造前后的性能试验结果进行了验证。模拟结果表明:改造后的TEPEE两山峰形管束布置方式有利于凝汽器壳侧蒸汽的流动与传热。性能试验结果表明:在设计冷却水进口温度、流量、凝汽器热负荷相同的条件下,改造后的凝汽器真空比改造前提高1.743kPa,端差下降4.63℃;凝汽器改造后,试验端差和修正后端差、修正后的凝汽器压力、循环水温升都达到设计指标。     

溶解性气体对开式循环凝汽器运行特性的影响

针对开式循环凝汽器冷却水系统，理论上研究引起内冷却水溶解性气体分离的机理，通过建立数学模型描述凝汽器的安装高度、环境温度、循环水量等对凝汽器水侧压力和溶解性气体分离的影响，提出国产中、大型机组凝汽器应装设出口水室抽气器，消除溶解性气体对凝汽器性能的不利影响。     

电厂循环冷却水系统冷却性能的影响因素研究

基于焓差法建立了电厂逆流自然通风循环冷却水系统热力模型,通过与15 MW机组运行数据相比较,验证了模型能够较好地模拟电厂循环冷却水系统热力过程。同时分析了影响逆流自然通风冷却系统冷却性能的因素,可为电厂循环冷却水系统的设计和实际运行提供指导。气象条件除大气压力外对冷却塔出水温度和凝汽器压力影响显著,以65 MW高温超高压机组为例,其中干球温度增加2℃,冷却塔出塔水温增加近1.4℃,凝汽器压力增加0.6~0.7 k Pa。凝汽器热负荷一定时,循环水量增加,冷却塔进水温度和凝汽器的压力下降,有利于提高全厂热效率,但出塔水温增加。     

330 MW机组凝汽器节能优化简析

通过对凝汽器真空度分析,采取降低凝汽器热负荷、提高真空系统严密性、加强循环水质的管理、利用停机机会对凝汽器铜管进行清洗、确保胶球清洗装置正常工作、加强对循环水泵的经济调度、降低循环水温等措施,提高了汽轮机凝汽器真空度,增加了机组功率,降低了发电煤耗和厂用电率。     

火力发电厂循环冷却水处理技术与运行监督

为了防止循环水质超标,引起凝汽器铜管腐蚀结垢等问题,通过对循环冷却水系统主要设备运行参数的掌握,了解循环冷却水处理技术对防腐、防垢、防菌藻的重点要求,提高专业运行水平和增强技术监督的有效性。通过技术运用分析,找到循环水质处理更有效的调整方法,控制水中的极限碳酸盐硬度做好防垢处理;分析腐蚀的物理、化学、生物因素,做好防腐处理;化学分析水质指标来监测水中微生物的动向,做好防菌藻处理;解决循环水浓缩倍率超标、凝汽器水室管板积垢等问题。避免因腐蚀结垢产生的管道泄漏、爆管导致的停机事件,保障机组的安全稳定运行,提高经济效益。     

Development of new and modified numerical methods for hyperbolic conservation laws

Abstract

The aim of the present work is to propose and modify several numerical methods including the classes of temporal discretization methods for hyperbolic conservation laws. The first order in space standard Lax approximation is updated to modified first-order and newly proposed third-order accurate approximation. Presently proposed methods can be coupled with the modified and newly proposed Lax approximations and this coupling make the methods conservative. Some additional new classes of explicit and implicit methods for PDEs in time are proposed. Additionally, some new methods are given to reduce oscillations in the solutions. These new methods of reducing oscillations provide the conditions for coupling of first and higher-order methods.     

A framework for allocating greenhouse gas emissions from electricity generation to plug-in electric vehicle charging

This paper describes a number of different allocation methods for assigning greenhouse gas emissions from electricity generation to charging plug-in electric vehicles. These methods for calculating the carbon intensity of electricity are discussed in terms of merits and drawbacks and are placed into a framework to aid in understanding the relation with other allocation methods. Three independent decisions are used to define these methods (average vs. marginal, aggregate vs. temporally-explicit, and retrospective vs. prospective). This framework is important because the use of different methods can lead to very different carbon intensities and studies or analyses that do not properly identify the methods used can confuse policymakers and stakeholders, especially when compared to other studies using different methods.     

Computational methods for passive solar simulation

The use of network models and a range of computational methods for the simulation of passive solar buildings are described, compared, and assessed. The following methods are considered: (i) Steadystate methods; (ii) Finite difference methods, explicit and implicit; (iii) Modal or analytic spectral methods; (iv) Fourier series methods. Methods (ii) to (iv) are compared by applying them to a series of numerical examples using the same data. In particular, the effect of network nodes with small thermal mass and the effect of increasing network size are considered. With explicit methods it is shown that it is important to approximate building components with small thermal mass by zero-mass nodes. Generally, the modal and implicit finite difference methods are the most efficient.     

气冷涡轮效率定义方法探讨

针对气冷涡轮效率定义方法进行了研究,首先介绍了几种常用的气冷涡轮效率定义,即气动热力学效率和涡轮级效率,并对这几种气冷涡轮效率定义进行了比较分析,最后以某一双级高压涡轮为例,分析了不同气冷涡轮效率定义方法对计算结果的影响。     

水利工程岩体质量分类方法综述

为加深对岩体质量分类体系的研究,从模糊分类法、可拓物元法、神经网络法、分形描述法、灰色聚类法、专家系统法等方面介绍了各种岩体质量智能化分类方法的原理与应用,分析了各种分类方法的研究现状及优缺点。最后,分析并总结了岩体质量研究的趋势和发展方向。     

径流式涡轮性能研究的进展

涡轮特性对涡轮增压器性能具有重要的影响,本文对涡轮特性的研究方法进行了简要的回顾。根据国内外学者对涡轮效率和涡轮流量特性的研究现状,总结了涡轮效率和流量特性的各种试验测量和数值计算方法,并简要分析了这些方法获得的涡轮性能参数的准确性,同时对这些方法各自的优缺点进行了对比。为涡轮增压器生产厂家获得涡轮特性提供参考。最后论文总结了涡轮性能研究方法的特点。     

A numerical comparison of different methods for optimizing heating-restart time in intermittently occupied buildings

The article starts with a brief recap of the restart time optimization methods: the classical methods, the methods based on fuzzy logic and the methods based on the use of a building model. In order to compare these different approaches, an intermittent heating controller, which makes it possible to define different methods for optimizing heating-restart time, has been developed as part of the TRNSYS software. Two of the six methods under study are new. These are the method based on fuzzy logic and the method using a two time constant building model. The numerical simulations carried out concern a building of which three rooms are studied. The changes in the various variables are presented in the case of the method based on fuzzy logic. Next, the different methods are compared according to restart precision, comfort obtained at the beginning of the occupancy period and energy consumption over the entire period of simulation.     

FINITE ELEMENT SIMULATION OF PHASE CHANGE USING CAPACITANCE METHODS

Two capacitance methods for finite element simulation of phase change problems are introduced. One is the “accelerated effective capacity method,” which is derived from Poirier and Salcudean's effective capacity method, and the other is the “exact apparent capacity method,” which is derived from the traditional apparent capacity method. Both of these new methods are developed by allowing the width of the “musky range” in the original methods to approach zero in a limiting process. The new methods are easier to implement in existing heat conduction codes than are most other fixed-grid methods. The methods are tested on one- and two-dimensional Stefan problems that have analytical solutions. It is found that the new methods are superior to the apparent capacity method, and their performance is comparable to that of the original effective capacity method and the enthalpy method for the test cases considered.     

坝后背管承载性能研究进展

以理论分析法、模型试验与原型观测法、有限单元法为线索总结了近年来坝后背管承载性能的研究成果。重点评析了管道外包混凝土开裂前后应力状态的计算方法、外包混凝土裂缝宽度的计算方法、提高管道耐久性的措施、有限单元法在坝后背管中的应用。提出了需要进一步深入研究的问题,包括合理的钢材配置计算方法、钢衬外包混凝土裂缝控制研究、非线性承载性能和破坏机理研究、动力承载性能研究、温度控制和温度应力分析、新型材料和新型结构型式研究等。