OPTIMAL OPERATION OF MULTI-QUALITY WATER SUPPLY SYSTEMS-II: THE Q-H MODEL

This paper describes the second in a series of three models for optimal operation of multi-quality water supply systems. This second model, which is termed the Q-H (flow-head) model, seeks to determine the optimal operation of pumps and valves, and does not consider water quality aspects. However, the model belongs to the group of three models Tor multi-quality systems because it is one of the two building blocks (the other is the flow-quality Q-C) of a full-llow-quality-head (Q-C-H) model. This Q-H model is based on continuous representations of the head-flow and power-flow functions of the pumping stations, which in turn results in a continuous non-convex optimization model. For a given flow distribution in the network, Q₀, the Q₀-H model is solved for the optimal operation of pumps and valves. The flow distribution is then modified by changing the circular flows, using a projected gradient method combined with the Complex Method which employs the results of the Q₀-H solution, such that the locally optimal solution at the next point has a better value of the objective function. The process is continued until one of the termination criteria is satisfied. The circular flows thus serve as decision variables in an external problem, while in the internal problem the decisions are the operation of pumps and valves. The method is demonstrated by application to a sample problem.     

OPTIMAL OPERATION OF MULTI-QUALITY WATER SUPPLY SYSTEMS-I: INTRODUCTION AND THE Q-C MODEL

One of three complementary models for optimal operation of multi-quality water supply systems is presented. The other two models are the subject of companion papers. The model, which is known as the Q-C (flow-quality) model, includes mass continuity of water and constituents. However, the hydraulic constraints do not appear explicitly. To prevent infeasibilities or unreasonable hydraulic conditions arising from the lack of hydraulic constraints, limits and a cost are associated with the flow in each pipe. The constraints in the model include dilution conditions which depend on flow direction. These dilution conditions are introduced into the model by an exponential function, resulting in a smooth continuous nonlinear programming problem, which is transformed into an equivalent problem and solved by a modified projected gradient method. The method is insensitive to scaling of variables, and the computational complexity depends only slightly on the number of water quality parameters. The method is demonstrated by application to two examples: the solution for a small network is presented in detail, and main results are shown for a larger one. The results of these two applications indicate the method's applicability to real networks.     

Optimal supervisory control of a central chilled water plant with heuristic search sequential quadratic programming

A new methodology for adapting rigorous simulation programs to optimal supervisory control of a central chilled water plant is proposed in this article, which solves plant operation mode optimization and set points optimization by combining heuristic search with sequential quadratic programming. The mathematical basis of this algorithm is developed. A new derivative calculation strategy is introduced in set points optimization. This approach is applied to a central chilled water plant which consists of three chillers, two 3-cell cooling towers, three chilled water pumps and three condenser water pumps. Model verification study is performed. The optimal sequence of operation, set points of the decision variables at given load demand and weather condition are calculated. The plant performance and optimal control results are discussed.     

用遗传算法求解供水泵站的效率优化问题

供水企业向来是城市的用电大户，其用电量主要体现在泵站水泵机组的电耗上。供水泵站的高效运行对节约电能、安全供水具有极为重要的意义。文章对供水泵站的效率优化问题进行了探讨，在提出用指数曲线准确地拟合水泵性能曲线的基础上，建立了供水泵站效率优化问题的数学模型，并设计了相应的遗传算法进行求解，仿真实验结果表明了该算法合理、有效。     

中空纤维超滤系统的水锤分析及防护

超滤系统的物理清洗是通过阀门频密开启和关闭、水泵的交替起动和停机来实现的,这使液体流速产生急剧变化;并引起很高的水锤压力,造成管道及膜元件损坏.分析了超滤系统出现关阀水锤及停泵水锤的成因,提出相应的防护措施.     

Optimal operation of multiquality water distribution systems: unsteady conditions

This paper describes the methodology and application of a genetic algorithm scheme tailor-made to EPANET, for optimizing the operation of a water distribution system under unsteady water quality conditions. The water distribution system consists of sources of different qualities, treatment facilities, tanks, pipes, control valves, and pumping stations. The objective is to minimize the total cost of pumping and treating the water for a selected operational time horizon, while delivering the consumers the required quantities at acceptable qualities and pressures. The decision variables for each of the time steps that encompass the total operational time horizon include: the scheduling of the pumping units, settings of the control valves, and treatment removal ratios at the treatment facilities. The constraints are: head and concentrations at the consumer nodes, maximum removal ratios at the treatment facilities, maximum allowable amounts of water withdrawals at the sources, and returning at the end of the operational time horizon to a prescribed total volume in the tanks. The model is explored through two example applications.     

An evaluation model of water-saving reconstruction projects based on resource value flows

Due to uncertainties in water supply, there is growing demand for water resource management in enterprises. In this study, we evaluated the effects of companies’ water-saving reconstruction projects. We used Hina Advanced Materials Company as a case to construct an investment decision model to (1) calculate the internal and external costs of water resources based on circular economic value analysis theory, and (2) locate the level of water resources circulation. We adopted gray situation decision analysis to identify the typical problems that occur in water resource utilization. Moreover, we demonstrated optimization plans for different potential improvements, thereby providing guidance and references for water resource cost management and the comprehensive optimization of environmental benefits. We concluded that the circulation economic value analysis model can effectively display the flow and amount of value derived from water resource flows, thereby providing guidance and suggestions for optimizing water resource flows.     

Optimal inventory control with sequential online auction in agriculture supply chain: an agent-based simulation optimisation approach

With the development of e-commerce, in agriculture supply chain, online auction is adopted as an inventory clearing tool. Comparing to mathematical models studying inventory control over online sequential auctions, our agent-based simulation model could systematically describe the complexities of bidders’ information interactions and behaviour preferences caused from financial and production perspectives, and by other supply chain members. In addition, we take into account the complex and dynamic market environment, which will impact the operation effect of auction policies. With identical auction items, the profit-maximising firm must decide auction lot-size, which is the number of units in each auction, minimum initial bid, and the time interval between auctions. To obtain the optimal solution, nested partitions framework and optimal expected opportunity cost algorithm are integrated to improve computation accuracy and efficiency. A case study based on real data is conducted to implement and validate the proposed approach. Furthermore, based on the model, the paper studies the sensitivities of the decision variables under different supply and demand scenarios.     

变频驱动并联水泵变压变流量运行优化调度

分析了变频驱动并联水联水泵变压变流量运行优化调度问题的常用建模方法,并比较了各种方法的优劣。常用的方法是以水泵轴功率作为目标函数,以供水指标和高效区为约束条件。另一种方法是以满足扬程指标时的实际流量与所需流量之差的二次方作为目标函数,以水泵的高效区作为约束条件。提出了一种新的建模方法,模型物理意义与实际工况严格相符,具有较高的精度,满足了工程中对水泵切换频率尽量小的要求。仿真结果表明该方法是有效的。     

Flexible work-in-process production system in supply chain management under quality improvement

For a complex product production, any flexible manufacturing system with a work-in-process inventory is recommended for a supply chain management (SCM) system. Building a flexible manufacturing system increases the total cost of the supply chain; for this reason, a discrete investment is important. For flexible production systems, production rate within a finite specific interval of production rate as work-in-process inventory is calculated. The aim of the supply chain is to reduce the total cost when demand during the lead time is a random variable with a normal distribution. A crashing cost is utilised to reduce the duration of lead time within the supply chain system. A model is proposed to obtain the optimal flexible production rate with the reduced total cost of the supply chain. A classical optimisation technique is employed to obtain the closed-form and quasi-closed-form solutions of the decision variables. An improved algorithm is designed to obtain the global minimum cost of SCM under the framework of a flexible production system. An illustrative numerical example and sensitivity analysis are given to test the model. A numerical study proves that this model obtains the minimum cost with the optimal decision variables.     

1 000 MW深度调峰机组热力系统优化研究

为提升超超临界火电机组深度调峰能力，解决大容量机组在低负荷时效率下降问题，提出并建设了1 000 MW高效宽负荷率机组示范工程。该工程对锅炉燃烧器、水冷壁及汽机蒸汽参数等进行了针对性的优化设计，通过协同增设补汽阀、外置式冷却器、零号高压加热器、低温省煤器等设备，实现了机组在较宽负荷范围内依然保持较高效率的目标。热力计算结果表明，示范机组在50%负荷下较现有机组效率提高3%以上，运行灵活性显著增强，取得了明显的经济和社会效益，相关经验对后续同类机组提升灵活性具有示范和参考价值。     

高压加热器最佳运行水位的确定方法研究

分析了加热器水位变化对上下端差的影响,并采用等效焓降法建立了加热器上下端差对机组相对内效率影响的计算模型,提出了加热器最佳运行水位的确定方法。以某电厂600MW机组高压加热器为例,定量分析了正常低水位运行对机组热经济性的影响,并利用本文提出的方法对三台高压加热器水位进行了调整,调整后机组相对内效率提高0.070%,热耗率降低了5.20kJ/（kW·h）,该方法能推广到其他类似机组上应用,对电厂经济运行具有很大实用价值。     

A Case Study of GAMM (Graphical Analysis for Maintenance Management) Applied to Water Pumps in a Sewage Treatment Plant,Chile

This article presents a case for practical application of the GAMM method, which has been developed and published by the authors. The GAMM method supports decision making in the overall maintenance management, through the visualization and graphical analysis of data. In addition, it allows for the identification of anomalous behavior in the equipment analyzed, whether derived from its own operations, maintenance activities, improper use of equipment or even as a result of design errors in the equipment itself. As a basis for analysis, the GAMM method uses a nonparametric estimator of the reliability function using all historical data or, alternatively, part of the history, allowing it to perform an analysis even with limited available data. In the case study presented, the GAMM method has been used to analyze two existing equipment parts in a sewage treatment plant located in Chile. The equipment analyzed were two progressive cavity pumps (BCP) which are part of the industrial process in the treatment plant. Both pumps are the same make and model and subjected to the same maintenance program, but one had a higher failure rate compared to its counterpart. The application of the GAMM method has identified deficiencies in each of the pumps being studied, thus improving decision‐making and problem‐solving process related to the maintenance of the pumps. RCM methodology was used to draft a new maintenance plan. Copyright © 2013 John Wiley & Sons, Ltd.     

大型钢筋混凝土长柱吊装的最优方案研究

为了解决电厂或工业厂房大型钢筋混凝土长柱吊装的施工难题,研究了其最优吊装方案的确定方法,并编制相应的计算机程序。针对拟定的双机双绳系统,建立了长柱内力分析的数学模型,选择吊点位置作为设计变量,以长柱吊装过程中弯矩最小作为目标函数,采用惩罚策略处理约束条件,以“网格法”和“遗传算法”对绳索系统的吊点位置进行了优化求解。通过对长柱在各种拟定绳系最优吊点下的内力比较,确定了最优的绳系方案。最后给出了一个算例说明方法的正确性和有效性。算例结果表明,通过优选绳系形式、吊点位置、绳长等参数,能使最大弯矩峰值下降30%左右。     

中小型空调水系统备用泵的优化设计探讨

分析目前空调水系统设计中常用的多台相同型号的水泵并联运行的弊端,从备用泵的选配设计入手,提出更节能、实用性更强的大小泵匹配的方案,并将其与常规水泵选配方案进行对比分析。     

Optimisation of multi-stage JIT production-pricing decision: centralised and decentralised models and algorithms

This research studies the optimal decision for product pricing, production lot sizing in a multi-stage serial just-in-time production system with kanban-controlled policy. A decentralised decision model and a centralised decision model of this problem are formulated as a mixed-integer nonlinear programming problem. In order to solve the models, three algorithms are developed. The first one is an approximate procedure which solves the decentralised decision model; the second one is a proximate optimal procedure using two-phase search technique that solves the centralised decision model, and the third one is an approximate method using meta-heuristic technique which is used for both decentralised and centralised models. Numerical example shows that centralised decision can obtain higher economic benefit with lower cost and higher revenue and profit. Meanwhile, when demand is more price sensitive, centralised decision can achieve significant profit enhancement. Computational results attribute to different characteristics of the problem and solution superiority.     

基于周期性激励的采煤机机电液截割传动系统特性分析

根据采煤机机电液截割传动系统的结构特点,考虑柱塞泵的流量脉动和齿轮传动系统的时变刚度,建立了包括泵和齿轮在内的传动系统机电液耦合模型。以流量脉动作为齿轮传动系统外部激励,以时变啮合刚度作为齿轮传动系统内部激励,基于内外部激励对采煤机机电液截割传动系统进行特性分析。结果表明:泵流量脉动对齿轮系统振动与动力学特性都有影响,且流量脉动作为外部激励是影响齿轮系统动力学特性的主要因素;考虑泵流量脉动后,马达输出呈现转矩脉动,截割传动系统总效率下降。     

PLC在饮用水深度净化控制系统中的应用

根据系统工艺,分析饮用水处理过程的特点和对控制系统的要求,采用西门子S7-200 PLC对控制系统的软硬件进行合理配置,利用PLC强大的逻辑控制功能和较多的内部时钟,实现控制系统的净水过滤和正反冲洗定时时间,各加压泵、反冲洗电机及众多阀门间复杂的联锁控制,保证了控制系统的安全可靠运行,并在运行中取得良好效果。     

Mixed integer programming for strategic decision support in the slaughter by-product chain

A mixed integer linear programming model to support strategic decision making is presented, in order to find the optimal processing structure for a slaughter byproduct business. In an integrated approach environmental objectives (such as odour emission, water pollution and energy consumption), market outlets, quality requirements (both for product and process), costs of processing, transportation, environmental measures and governmental restrictions are modelled to find the optimal investment strategy for future ways of processing slaughter by-products. Emphasis has not been put on development of new models or techniques. The value of this contribution is how to find new cost-effective logistical solutions within a framework of environmental restrictions, quality and technological opportunities.     

自控阀在给水管网中布置方法的研究

提出了一个通过管网水力计算在管网中实现自控阀合理布置的方法。将自控阀的局部水头损失引入管网水力计算当中，计算自控阀在每个管段不同开启度条件下对管网压力变化的影响程度，提出管网影响度的概念。并以实例管网进行验证，得出了自控阀在管网中合理布置的一般原则。研究证明，该方法具有实用、简便、易于操作等特点，非常有利于在供水企业中的应用。