An analysis to minimize the amount of spring back after coiling of helical steam generator tubes

The spring back phenomena occurring in the coiling process of a steam generator tube induce dimensional inaccuracy and make the coiling procedure difficult. In this research, an analytical approach has been carried out to evaluate the amount of spring back for helical steam generator tubes. The model was developed on the basis of beam theory and elastic–perfectly plastic material properties. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that low yield strength, high elastic modulus, small helix diameter, and large tube diameter result in a small amount of spring back. The amount of spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by application of a tensile force to the tube during the coiling process.     

The influence of economic parameters on the optimal values of the design variables of a combined cycle plant

This paper presents the analysis of the influence of fuel price variation on the optimal values of the design variables of the steam part of a combined cycle plant. The investigated system was a power plant with a triple-pressure heat recovery steam generator and extraction-condensation steam turbine. Fourteen design variables for the steam part were identified. The variables that were optimised were the pressure levels of the working medium in the steam part of the system, and characteristic differences of temperatures in the heat recovery steam generator. Thanks to the development of an optimising programme, based on the genetic algorithms theory, it was possible to find an optimal solution. The indices of economic efficiency, in the form of the break-even price of electricity, were chosen as the objective function in the optimisations. The results of economic optimisations were compared with the results of the optimisation, where the electric efficiency was the objective function. This paper includes an analysis of the sensitivity of the economic objective function to failures in the adherence of the optimal values of decision variables. This analysis allowed the selection of variables such that a failure results in the highest increase of the break-even price of electricity.     

Effects of particle sizes on performances of the multi-zone steam generator using waste heat in a bio-oil steam reforming hydrogen production system

Hydrogen production by bio-oil steam reforming is an advanced production technology. It is a good method of coupling waste heat utilization with bio-oil steam reforming to produce hydrogen, which increases the cleaning ability of the bio-oil steam reforming system. A multi-zone steam generator using waste heat has been proposed, which can produce the heat source and steam source of the hydrogen system. The DEM model of the multi-zone steam generator was set up. The model has been used to investigate the effects of particle sizes (40 mm–80 mm). With increasing particle size, the flow index and the flow uniformity gradually decrease, the vertical velocity gradient increases in the area on both side with the zone steam generator, and the vertical velocity fluctuation amplitude gradually increases. So, the hydrogen production decreases from the particle size increasing.     

Central collector solar energy receivers

Central receivers for use with power-generating equipment require compact boiler and superheater designs to effectively concentrate the solar heat input and to improve system power cycle efficiency. Solar thermal collectors employ a central receiver that must be compact to effectively utilize the high concentration ratios of sunlight energy. The demonstration of lightweight, long-life receiver designs is a technology issue that must be resolved if the concept is to be attractive for power generation. The receiver must be lightweight to minimize the cost of the supporting tower structure. Current applied aerospace technology in compact steam boilers and rocket thrust chamber designs can be directly applied to the design and fabrication of solar central receivers.This technology recently has been applied to a compact steam generator that uses liquid oxygen and natural gas, propane or fuel oil. The compact steam generator permits a 300:1 size reduction in boiler and superheater size. This paper discusses the application of the compact steam generator technology to the design and fabrication of central receivers for solar-energy-powered electrical powerplants. Receiver designs are discussed for tower-mounted applications where size and weight are important. The heat flux rates necessary for central solar receivers are nearly identical to the design hear fluxes for the compact steam generator. Fabrication of the central receiver is discussed as well as design details and applicable materials.     

Modeling analysis on solar steam generator employed in multi-effect distillation (MED) system

Recently the porous bilayer wood solar collectors have drawn increasing attention because of their potential application in solar desalination. In this paper, a thermodynamic model has been developed to analyze the performance of the wood solar collector. A modeling analysis has also been conducted to assess the performance and operating conditions of the multiple effect desalination (MED) system integrated with the porous wood solar collector. Specifically, the effects of operating parameters, such as the motive steam temperature, seawater flow rate, input solar energy and number of effects on the energy consumption for each ton of distilled water produced have been investigated in the MED desalination system combined with the bilayer wood solar steam generator. It is found that, under a given operating condition, there exists an optimum steam generation temperature of around 145°C in the wood solar collector, so that the specific power consumption in the MED system reaches a minimum value of 24.88 kWh/t. The average temperature difference is significantly affected by the solar heating capacity. With the solar capacity increasing from 50 kW to 230 kW, the average temperature difference increases from 1.88°C to 6.27°C. This parametric simulation study will help the design of efficient bilayer wood solar steam generator as well as the MED desalination system.     

某核电堆型蒸汽发生器排污系统设计改进

根据全范围事故分析结果,在发生蒸汽发生器传热管破裂(SGTR)事故中,为使发生故障的蒸汽发生器水位不会上升太快,需通过蒸汽发生器排污系统排污管线来控制故障蒸发器的水位和压力。通过对蒸汽发生器排污系统进行设计改进,提高系统的设计标准,将破损蒸汽发生器内漏液排向内置换料水箱,使破损蒸汽发生器降压,同时限制破损蒸汽发生器水位,防止破损蒸汽发生器满溢,满足蒸汽发生器排污系统在设计基准事故工况下承担安全功能的要求。改进后的蒸汽发生器排污系统满足国内三代核电技术的要求,为国内三代核电的安全性提供理论依据。     

Effect of the vacancy close to heat exchange wall on the heat transfer performance of the solid particles steam generator using waste heat in a methanol steam reforming hydrogen production system

With the massive consumption of fossil fuels and it resulted in significant carbon emissions, it is urgent to find an alternative clean energy source. Hydrogen has been regarded as one of the most promising energy candidates for the next generation. It is a great approach that methane steam reforming for hydrogen production by rational utilization of industrial waste heat, which significantly minimizes carbon emissions and develops methanol steam reforming technology. A solid particle steam generator based on the primary heat exchange method has been proposed, which can provide the heat and steam in the methanol steam reforming hydrogen production system. The quasi-two-dimensional packing heat transfer model of solid particles steam generator was set up.The effect of distance change between the vacancy and the cold wall and distance change between vacancies on heat transfer performance of the steam generator and hydrogen production capacity were studied. As the distance between the vacancy and the wall increases, the heat transfer performance of the steam generator gradually deteriorates, so the steam production of the steam generator decreases, and the system's hydrogen production capacity is reduced, the maximum of the heat flux and the minimum of the apparent thermal resistance are 34.67 kW/m² and 12.02 K/W, respectively. As the distance between vacancies increases, the heat transfer performance of the steam generator is gradually optimized slightly. To maintain the hydrogen production capacity, vacancies should be avoided to appear 2 layers of particles away from the heat exchange wall in the particles steam generator. From the results of the study, the farther the distance between vacancies, the better the steam production and hydrogen production capacity.     

大型汽轮发电机组框架式基础的动力特性研究

对大型汽轮发电机组框架式基础利用子结构法进行了动力学建模分析。平台、立柱框架部分采用梁单元进行离散化,基础底板则采用弹性薄板的Ｒitz函数近似解来模拟,从而有效地解决了基础与地基的边界接触问题。根据该动力学模型编制了ＦＦＡＳ框架式基础动力特性分析软件,对国内某电厂的１台６００ＭＷ汽轮发电机组框架式基础进行了特性分析计算,并得出了结论。     

超临界机组汽轮机调速系统模型参数确定的新方法

汽轮机调速系统模型参数的确定,对各种热力发电机组的仿真,控制系统的设计及电力系统动态研究具有重大意义.通过蒸汽发电机组有效热平衡数据计算出汽轮机模型参数,得出各种不同工况下参数的变化规律,比实测法更方便简捷实用.对600MW超临界机组汽轮机调速系统的模型参数进行分析计算,并用该模型针对特殊的阶跃响应作出仿真和分析.     

大型汽轮发电机组基础的优化设计

汽轮机基础的优化是大型发电机组系统设计的主要问题之一.用空间梁单元建立汽轮机基础的动力学分析模型.结合极差分析和正交设计的分析方法,运用有限元数值模拟,对国内某大型汽轮发电机组基础进行优化设计,得到了动力特性优良的汽轮机基础方案,并揭示了汽轮机基础动力特性影响因素的敏感程度.通过与模型试验结果的比较,验证了有限元正交数值模拟的准确性.     

United states criteria for repair and replacement of BWR piping and steam generator tubing

This paper discusses the criteria currently used by the US Nuclear Regulatory Commission in dealing with repairs and replacement of BWR piping and steam generator tubing and provides the bases for these criteria. As a result of extensive cracking in BWR pipes caused by intergranular stress corrosion, a program of augmented inspection and leak testing has been instituted. Emphasis is placed on returning such piping to original design conformance either by replacement with non-susceptible material or by a combination of stress improvement and environmental control. As a result of a number of degradation mechanisms in steam generator tubes, inspection and criteria for plugging or sleeving have been instituted along with broad recommendations aimed at an integrated program for resolving steam generator tube problems.     

Hybrid feedforward and feedback controller design for nuclear steamgenerators over wide range operation using genetic algorithm

In this paper, a simplified model with a lower order is first developed for a nuclear steam generator system and verified against realistic environments. Based on this simplified model, a hybrid multi-input and multi-out (MIMO) control system, consisting of feedforward control (FFC) and feedback control (PEC), is designed for wide range conditions by using the genetic algorithm (GA) technique. The FFC control, obtained by the GA optimization method, injects an a priori command input into the system to achieve an optimal performance for the designed system, while the GA-based FBC control provides the necessary compensation for any disturbances or uncertainties in a real steam generator. The FBC control is an optimal design of a PI-based control system which would be more acceptable for industrial practices and nuclear power plant control system upgrades. The designed hybrid MIMO FFC/FBC control system is first applied to the simplified model and then to a more complicated model with a higher order which is used as a substitute of the real system to test the efficacy of the designed control system. Results from computer simulations show that the designed GA-based hybrid MIMO FFC/FBC control can achieve good responses and robust performances. Hence, it can be considered as a viable alternative to the current control system upgrades     

Hydrogenoxygen steam generator for a closed hydrogen combustion cycle

The paper deals with the problems of hydrogen combustion in an oxygen environment to produce high-temperature steam to be used in electricity generation at various power stations including nuclear power plants (NPP). For example, the use of H₂/O₂ steam generator within a hydrogen energy complex may allow increasing the NPP power and efficiency under operating conditions due to hydrogen steam superheating of the main working fluid in a steam-turbine unit. In addition, the use of the hydrogen energy complex may allow adapting NPP to variable electric load schedules with the increasing share of such power stations as well as developing environmentally friendly technologies for electricity generation. In the paper, a new solution to the problem of the effective and safe use of hydrogen energy at NPP with a hydrogen energy complex has been proposed.Technical solutions to hydrogen combustion in an oxygen environment using direct injection of cooling water or water steam into combustion products may have a significant weakness, namely the “quenching” phenomenon occurring during water/water steam injection resulting in the recombination efficiency decrease during the cooling of combustion products which is reflected in the increased proportion of non-condensable gases. In this case, the supply of such mixture to the steam-power cycle may be unsafe, as it could result in the increased concentration of unburned hydrogen in the steam turbine flow path. In the paper, a closed hydrogen cycle along with the hydrogen steam superheating system on its basis has been proposed to solve this problem. The closed-circuit system of hydrogen combustion preventing hydrogen permeation into the working fluid of a steam cycle completely as well as ensuring its full oxidation due to some excess of circulating oxygen has been investigated by the authors.Two types of H₂/O₂ combustion chambers for the system of safe hydrogen steam superheating in NPP cycle by using the closed-circuit system of hydrogen combustion in an oxygen environment have been considered in the study. The required parameters of H₂/O₂ steam generator with regard to operating temperature conditions as well as the power range of H₂/O₂ steam generators with the proposed combustion chamber construction design have been determined by mathematical modeling of the combustion and heat-mass-exchange processes.     

Thermoeconomic modeling and parametric study of hybrid SOFC–gas turbine–steam turbine power plants ranging from 1.5 to 10 MWe

Detailed thermodynamic, kinetic, geometric, and cost models are developed, implemented, and validated for the synthesis/design and operational analysis of hybrid SOFC–gas turbine–steam turbine systems ranging in size from 1.5 to 10 MWe. The fuel cell model used in this research work is based on a tubular Siemens-Westinghouse-type SOFC, which is integrated with a gas turbine and a heat recovery steam generator (HRSG) integrated in turn with a steam turbine cycle. The current work considers the possible benefits of using the exhaust gases in a HRSG in order to produce steam which drives a steam turbine for additional power output. Four different steam turbine cycles are considered in this research work: a single-pressure, a dual-pressure, a triple pressure, and a triple pressure with reheat. The models have been developed to function both at design (full load) and off-design (partial load) conditions. In addition, different solid oxide fuel cell sizes are examined to assure a proper selection of SOFC size based on efficiency or cost. The thermoeconomic analysis includes cost functions developed specifically for the different system and component sizes (capacities) analyzed. A parametric study is used to determine the most viable system/component syntheses/designs based on maximizing total system efficiency or minimizing total system life cycle cost.     

基于传热性能变化的余热锅炉故障诊断及应用

以某电厂PG9171E燃气-蒸汽联合循环机组余热锅炉系统为研究对象,根据机组的热平衡图数据以及余热锅炉受热面的传热机理建立变工况模型,定义受热面的性能退化系数,建立故障诊断模型。利用建立的计算模型与故障数据计算出的结果,对机组低压汽水系统的异常现象进行分析诊断,可以明确看出低压蒸发系统出现异常。现场停机检查结果发现问题为低压汽包内部件脱落,导致汽水分离效果差,与理论分析结果一致,验证了计算模型的正确性。     

Lessons from the past: materials-related issues in the ultrasupercritical boiler,Eddystone Unit 1

Abstract

Major research efforts in both the USA and Europe have made substantial progress toward the development of coal fired ultrasupercritical steam generators that will operate at efficiencies approaching 50% based on higher heating value (HHV). A test facility designed to evaluate operation of major steam generator components at 700°C is now operational in Germany. A focus of these efforts has been the demonstration of reliability of the materials that would be used in an ultrasupercritical steam generator. However, proof of the viability of ultrasupercritical technology can be found at the Eddystone plant in Pennsylvania. The steam generator for unit 1 at that plant has operated successfully for >45 years in steam conditions more advanced than any other central station unit in operation today. The operating history is briefly reviewed, focusing on the materials related problems that forced a modest retreat from the original, unprecedented design conditions, but emphasising the record of many years of reliable operation. Some significant materials related issues involved in operating a steam generator at 'Eddystone' like conditions are used as a basis to argue that there exists today the materials and manufacturing understanding necessary to construct a more advanced ultrasupercritical unit that will operate efficiently and reliably.     

塔式熔盐太阳能光热电站蒸汽发生器传热数值模拟设计计算

采用数值模拟的方式研究了50 MW塔式熔盐太阳能光热发电蒸汽发生系统蒸发器传热计算过程,利用Fluent软件建立三维模拟,通过合理的假设对蒸发器传热过程进行求解。计算结果表明:计算机数值模拟计算方法能够较好地反应蒸发器的真实传热过程,与传统理论计算、商业软件和实验数据有较好的契合度,表明数值模拟计算方法能够作为一种太阳能光热蒸汽发生器性能设计和优化的有效方法。     

Engineering design and exergy analyses for combustion gas turbine based power generation system

This paper presents the engineering design and theoretical exergetic analyses of the plant for combustion gas turbine based power generation systems. Exergy analysis is performed based on the first and second laws of thermodynamics for power generation systems. The results show the exergy analyses for a steam cycle system predict the plant efficiency more precisely. The plant efficiency for partial load operation is lower than full load operation. Increasing the pinch points will decrease the combined cycle plant efficiency. The engineering design is based on inlet air-cooling and natural gas preheating for increasing the net power output and efficiency. To evaluate the energy utilization, one combined cycle unit and one cogeneration system, consisting of gas turbine generators, heat recovery steam generators, one steam turbine generator with steam extracted for process have been analyzed. The analytical results are used for engineering design and component selection.     

A cooling system for the secondary helium loop in VHTR-based SI hydrogen production facilities

Nuclear hydrogen production facilities consist of a very high temperature gas-cooled nuclear reactor (VHTR) system, intermediate heat exchanger (IHX) system, and a sulfur–iodine (SI) thermochemical process. This study focuses on the coupling system between the IHX system and SI thermochemical process. To prevent the propagation of the thermal disturbance owing to the abnormal operation of the SI process components from the IHX system to the VHTR system, a cooling system for the secondary helium of the IHX is required. In this paper, a conceptual flow diagram of the coupling system has been proposed. The temperature fluctuation of the secondary helium owing to the abnormal operation of the SI process was then calculated based on the proposed coupling system model. Finally, the conceptual design of the cooling system for the secondary helium of the IHX with a steam generator and forced-draft air-cooled heat exchanger to mitigate the thermal disturbance has been carried out.     

核电站蒸汽发生器水位的自抗扰多模型控制方法研究

针对核电站蒸汽发生器水位控制的非线性分布特点,在自抗扰控制技术的基础上结合多模型控制提出了蒸汽发生器水位系统新的控制方案.在该控制方案中,对蒸汽发生器设计了多模型控制系统,并针对各个模型分别设计了不同负荷下的自抗扰控制器,可以对扩张状态进行在线实时估计,因此设计的扰动补偿不依赖于模型便能够达到快速消去扰动的效果.将该方法用于蒸汽发生器水位控制系统进行仿真研究,结果表明：该控制方案实现了对蒸汽发生器水位良好的动态控制,具有较强的鲁棒性和抗干扰能力,且算法简单,便于调试.