某氦制冷氢液化主体设备的热力学分析

对一套中型氢液化设备进行介绍,跟据火用分析理论对循环各个部件分别进行热力学第一和第二定律分析,给出了各个部件的输入和产出火用公式,计算了损失分布。通过计算分析,明确了能量损失的部位及量的多少,为氢液化系统的优化设计提供了参考。     

Failure analysis of gas turbine blades in a thermal power plant

A case study of failure analysis of a 40 MW gas turbine blade made of Udimet 500 is presented. The cause of failure is found to be intergranular cracks which started during exposure to high temperature. The cracks initiated from the grain boundaries and propagated to the critical length to result in catastrophic fracture. In many locations M₆C type secondary carbides were found agglomerated on grain boundaries. Also micro-cavities were found on fracture surfaces which served as an origin of creeping failure mechanism.     

Exergetic analysis and evaluation of coal-fired supercritical thermal power plant and natural gas-fired combined cycle power plant

The present work has been undertaken for energetic and exergetic analysis of coal-fired supercritical thermal power plant and natural gas-fired combined cycle power plant. Comparative analysis has been conducted for the two contestant technologies. The key drivers of energetic and exergetic efficiencies have been studied for each of the major sub-system of two contestant technologies. Overall energetic and exergetic efficiency of coal-fired supercritical thermal power plant are found to be 43.48 and 42.89 %, respectively. Overall energetic and exergetic efficiency of natural gas-fired combined cycle power plant are 54.47 and 53.93 %, respectively. The major energetic power loss has been found in the condenser for coal-fired supercritical thermal power plant. On the other hand, the major energetic power loss has been found in both the condenser and heat recovery steam generator for gas-fired combined cycle thermal power plant. The exergetic analysis shows that boiler field is the main source of exergetic power loss in coal-fired supercritical thermal power plant and combustion chamber in the gas-fired combined cycle thermal power plant. It is concluded that natural gas-fired combined cycle power plant is better from energetic and exergetic efficiency point of view. These results will be useful to all involved in the improvement of the design of the existing and future power plants.     

热电厂采用热电冷联供的适用性分析

利用等效发电效率概念,以300MW级抽凝式供热机组为例,对热电冷联供的适用性进行分析。在目前电、热价格以及发电机组装备水平的基础上,提出城市热电厂推广使用热电冷联供的约束性条件。     

Failure analysis of a run-of-the-river hydroelectric power plant

One of the challenges posed by hydraulic energy generation stems from the exploitation of hydrological resources that carry significant amounts of sediment that erodes the surfaces of turbines. This is the case for the Amaime hydroelectric plant, which is located in the western mountainous region of Colombia and was seriously affected by sediment after a brief period of operation. The main symptom indicating failure was a rise in the temperature of the bearings caused by an increase of almost two bars in the pressure between the cover on the side of the generator and the runner, which was caused by the wearing of the seal labyrinths. Inspections that were carried out after six months of operation indicated that there was a 300% increase in the clearance between the covers and the runner, which caused a higher axial thrust on the bearing. The inspections verified that severe wear had occurred on important elements of the turbine, such as the runner, guide vanes and turbine covers, which required major repairs to the two generation groups of the plant in less than 2 years, which is a much shorter time between repairs than is recommended by international standards. Analyses of the material, medium, particles and the worn surfaces demonstrated that the wear on the turbine was mainly due to erosion by hard particles, which was caused by the high sediment concentration and the low hardness of the material used to construct the turbine.     

Test interval optimization of safety systems of nuclear power plant using fuzzy-genetic approach

Probabilistic safety assessment (PSA) is the most effective and efficient tool for safety and risk management in nuclear power plants (NPP). PSA studies not only evaluate risk/safety of systems but also their results are very useful in safe, economical and effective design and operation of NPPs. The latter application is popularly known as “Risk-Informed Decision Making”. Evaluation of technical specifications is one such important application of Risk-Informed decision making. Deciding test interval (TI), one of the important technical specifications, with the given resources and risk effectiveness is an optimization problem. Uncertainty is inherently present in the availability parameters such as failure rate and repair time due to the limitation in assessing these parameters precisely. This paper presents a solution to test interval optimization problem with uncertain parameters in the model with fuzzy-genetic approach along with a case of application from a safety system of Indian pressurized heavy water reactor (PHWR).     

Measurement of thermal fluxes in power plant components

A method of recovering the thermal flux acting on a sensing element with respect to measurements of sensing element signals is described.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 6, pp. 990–994, June, 1985.     

Predicting microdroplet force response using a multiscale modeling approach

An axisymmetric microscale finite element model of a microdroplet test specimen is developed where the structural response of the fiber–droplet interface is accounted for by surface-based cohesive behavior. In this study, the interface cohesive response is estimated using a nanoscale interface finite element model that explicitly includes the effects of fiber surface topography and the interphase region. The interphase behavior in the nanoscale interface model is calibrated using indirect experimental data. Once calibrated, the fiber surface topography in the nanoscale interface model is modified in order to estimate the parameters defining the surface-based cohesive behavior of similar fiber–matrix systems with different fiber topography. The effect of altering the fiber topography on the force response of the microdroplet test can then be predicted by the microdroplet FE model. Comparing the simulation results with experimental data from the literature shows that this multiscale modeling approach gives accurate predictions for the interfacial shear stress.     

Monte Carlo simulation approach for a modified FMECA in a power plant

This paper presents a new tool for failure mode and effect analysis developed for a new Integrated Gasification and Combined Cycle plant in an important Italian oil refinery. The methodology is based on the integration between a modified Failure Mode Effect and Criticality Analysis (FMECA) and a Monte Carlo simulation as a method for testing the weights assigned to the measure of the risk priority numbers (RPNs). The RPN proposed consists of a weighted sum of six parameters (safety, machine importance for the process, maintenance costs, failure frequency, downtime length, and operating conditions) multiplied by a seventh factor (the machine access difficulty). Adopting this tool and considering the budget constraints, the best maintenance policy has been selected for each plant facility (about 140 in total). Copyright © 2000 John Wiley & Sons, Ltd.     

Exergy analysis of a Gifford-McMahon cycle cryorefrigerator

Exergy analysis of a Gifford-McMahon cycle refrigerator is presented. Exergy losses occurring in various components are considered and the exergy balance is shown in tabular form. It is observed that the major losses occur in the compressor and at the cold end.     

Solar power plant site selection modeling for sensitive ecosystems

Clean Technologies and Environmental Policy - Reducing dependence on fossil fuels and increasing energy production based on renewable energy sources is a powerful alternative to alleviate global...     

火电厂给水再循环管道振动分析与控制

针对某火电厂给水再循环管道振动的原因和集中位置进行分析并提出相应的控制方案。首先建立再循环管道和水流的实体模型、支吊架简化模型并进行装配,然后导入至ANSYS中进行CFX流体分析,得到水流作用于管道内壁的冲击压力并导入至结构力学模块进行二次分析,再将分析数据传递至模态分析模块进行运算,得到流固耦合作用下管系前50阶的固有频率和前6阶振型,最后结合实验测试结果分析再循环管道振动的原因和振型最大点位置分布规律,并提出相应的支吊架调整干预方案,调整后管系各阶固有频率有所上升,管系振动明显好转,表明所提控制方案可行、有效。该文工作对于火电厂给水再循环管道振动的监测和控制有参考价值。     

Failure analysis on a primary superheater tube of a power plant

In this paper failure analysis on the SA213-T12 superheater tube by visual inspection, in situ measurements of hardness and finite element analyses is presented. A primary superheater tube has failed with a wide open burst after running at around 28,194 h. Heavy clinkers were found to almost entirely cover the primary superheater region. In situ hardness measurements were carried out on the selected primary superheater first row tubes at the middle region between furnace rear screen tube and primary superheater blower flow path. Hardness measurements are also taken on the as-received failed tube. Finite element analyses on possible features prior to failure are also conducted in order to illustrate and deduce the failure mechanism and failure root cause. Localized short-term overheating of the tube due to localized and concentrated flue gas flow resulted in a failure of the primary superheater tube.     

An analysis of maintenance failures at a nuclear power plant

In this paper, a study of faults caused by maintenance activities is presented. The objective of the study was to draw conclusions on the unplanned effects of maintenance on nuclear power plant (NPP) safety and system availability. More than 4400 maintenance history reports from the years 1992–1994 of Olkiluoto BWR NPP were analysed together with the maintenance personnel. The human action induced faults were classified, e.g. according to their multiplicity and effects. This paper presents and discusses the results of a statistical analysis of the data. Instrumentation and electrical components appeared to be especially prone to human failures. Many human failures were found in safety related systems. Several failures also remained latent from outages to power operation. However, the safety significance of failures was generally small. Modifications were an important source of multiple human failures. Plant maintenance data is a good source of human reliability data and it should be used more in the future.     

Reactive power cost allocation by using a value-based approach

This study proposes a value-based approach to allocate the cost of reactive power production/absorption and the useful VAr reserve provided by the generators. Reactive power support can be segregated into two broad categories: the utilised component of the support and the reactive power reserve component for system security. The utilised reactive power capacity can be decomposed further into the support required for meeting the reactive power loads and that required to meet additional reactive power transmission losses for the MW load shipment. A value-based sensitivity approach has been utilised to compute utilisation factors (UFs) for allocation of the cost of reactive power production/absorption and reserve provision. This method provides transparency in determining the relative utilisation and supply of reactive power by sources to the customers. System operator (SO) can utilise this method for allocation of the cost incurred by the reactive power providers to the load serving entities. Case studies on five-bus test system, IEEE 24-bus reliability test system (RTS) and 75-bus Indian system demonstrate the proposed approach.     

Removal of 2,4-dichlorophenol and pentachlorophenol from waters by sorption using coal fly ash from a Portuguese thermal power plant

Chlorophenols are one of the most important groups of priority pollutants, due to their high toxicity, mutagenicity and carcinogenicity. Although activated carbon has been the preferred choice for the removal of such pollutants from wastewaters, the search for cheaper alternative sorbents became common in the last years. Fly ash, a by-product from coal burning power plants, has a surface composition that may enable the sorption of specific organic compounds. Therefore, this feasibility study presents the optimization of the operating parameters of a fixed-bed column containing fly ash particles, percolated by aqueous solutions of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) with concentrations of 1 and 100 microg/ml. Both chlorophenols were analysed by gas chromatography with electron capture detection (GC-ECD), after solid-phase microextraction (SPME), with limits of detection (LODs) of 7.28 microg/l for 2,4-DCP and 1.76 microg/l for PCP. Removal efficiencies above 99% were obtained for an initial concentration of 10 microg/ml of chlorophenols. Column saturation was achieved after 7h of continuous operation for 2,4-DCP and 10h for the PCP for feed levels of 10 microg/ml. Fly ash exhibited more affinity towards the sorption of PCP, in comparison to 2,4-DCP.     

Applications of microstructural characterization and computational modeling in damage analysis of a turbine blade exposed to service conditions in a power plant

Microstructural characterization and computational modeling were used to analyze the damage produced by overheating of a turbine blade exposed to service conditions in a power plant. Various electron-optical techniques were used to characterize the microstructure. Localized overheating was reflected by the microstructural features of the blade material particularly the extent of interdiffusion between the coating and alloy substrate, coarsening of the γ′-phase, and re-precipitation of M₂₃C₆ carbide by a discontinuous mechanism at grain boundaries. Damage associated with these effects included creep cavities at grain boundaries and intergranular oxidation leading to ductile intergranular cracking at the leading edge of the blade. Most evidence pointed out that improper internal cooling of the blade resulted in excessive overheating at leading edge. Qualitatively, the temperature profile across the blade as indicated by microstructural variations was consistent with the results derived from computational modeling.     

某抽水蓄能电站地下厂房热湿环境测试分析

水电站地下厂房的通风空调系统对维持厂房内的热湿环境,使其满足人员工作及设备运行的要求有着重要作用。为了对某抽水蓄能电站地下厂房的热湿环境进行评估,对主厂房各层空间空气的热湿参数及通风量进行测试,并结合室外天气状况得出室外天气对厂房内的热湿环境的影响。在测试过程中发现,其蜗壳层设备及管路表面结露问题严重。根据对结露现象的分析,提出相应的解决方案,为水电站地下厂房的热湿环境的调控提供参考。     

Exergetic analysis of solar concentrator aided coal fired super critical thermal power plant (SACSCTPT)

Comparative energetic and exergetic analysis of coal-fired supercritical thermal power plant (CSCTPT) and solar concentrator aided coal fired supercritical thermal power plant (SACSCTPT) have been carried out in this article. Optical analysis of Linear Fresnel reflecting (LFR) solar concentrator is used to predict the effect of focal distance and width of reflector upon the local concentration ratio and the tilt (θ) angles that are important parameters for SACSCTPT performance studies. Energetic and exergetic analysis for evaluating the effect of concentration ratio and inlet temperature of the fluid on LFR solar concentrator are carried out. An instantaneous increase in power generation capacity of about 20 % is observed by substituting turbine bleed streams to all the low pressure and high pressure feed water heaters of CSCTPT with solar concentrator aided feed water heaters (SAFWH). Coal consumption is increased by 3.35 % for reheat of the steam by substitution of high pressure feed water heaters with SAFWH. Energetic efficiencies of SACSCTPT appear high as compared to the solar alone thermal power plant and low as compared to coal-fired super critical thermal power plants. Furthermore, for a SAFWH, it is found that the land area requirement is 4.78 ha/MW.