Investigation of Oil Vapours in Hydro-Generator

The article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the article suggests ways to reduce the amount of oil mist. For their implementation, a calculation methodology based on the substitution scheme of the hydraulic path of the bearing support unit is created which takes into account the design features of the bearing and the parameters of the environment around the oil bath. The methodology employed is presented. The numerical method of modelling the aerodynamic fields of the entire hydro generator is used to estimate the air flows and pressures in the oil bath zone of the thrust bearing. Additionally, the method made it possible to track suspected oil particles that could get from the thrust-bearing bath into the surrounding area of the generator. Measures are proposed to reduce the level of oil mist through the competent design of the oil vapour removal system from the bearing bath.

Air interaction around outdoor air-cooled condensers

In order to increase cooling or heating efficiency,a porous computational fluid dynamics（CFD）model is employed to predict the thermo-fluid status and optimize the placement of outdoor units.A full scale model is established to validate the accuracy of CFD simulation in terms of velocity and temperature distributions.The comparison between the measurement and the simulation shows a good agreement.By evaluating the condensers＇ sucked air temperature with CFD for three units installed in a row,it is found that the minimum separation distance among neighboring units is 0.2 m;a vertical wall should be apart from the unit line by at least 0.8 m;and large different operating pressures among units do not impact the flow rate and the heat transfer of the other units meaningfully.

Resonance of electromagnetic and mechanic coupling in hydro-generator

Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations,instabilities of hydro-generator rotors caused by the unbalanced magnetic pull,which comes from the eccentricity of the rotor,are discussed.Considering nonlinear properties of the unbalanced magnetic pull,the super-harmonic resonance phenomena are observed as the critical rotating speed of rotors is close to twice of the operating speed.This is verified by a model experiment,and should be considered during the design of hydro-generator rotors.

Precipitation of α_2 Phase in α+β Solution-Treated and Air-cooled Ti-Al-Sn-Zr-Mo-Si-Nd Alloys

A series of Ti-Al-Sn-Zr-Mo-Si-Nd alloys with various content of Al were solution treated in α+β phase field and air-cooled. The precipitation of a2 phase in cooling was investigated by transmission electron microscopic analysis The precipitation characteristic of α2 phase was discussed. The precipitation of α2 phase would proceed by the nucleation and growth of α2 phase dependent on the diffusion of Al atoms. And a comparison on the difference of precipitation of α2 phase was carried out under the conditions of air-cooling and quenching in water. The investigation showed that the air-cooling and even quenching could supply enough time for the precipitation and growth of α2 phase when Al content reached a certain value even though far away from the stoichiometric composition of Ti3Al.

Microstructure and properties of rheo-HPDC Al-8Si alloy prepared by air-cooled stirring rod process

A new and effective semisolid slurry preparation process with air-cooled stirring rod(ACSR)is reported,in which the compressed air is constantly injected into the inner cavity of a stirring rod to cool the melt.The slurry of a newly developed high thermal conductivity Al?8Si alloy was prepared,and thin-wall heat dissipation shells were produced by the ACSR process combined with a HPDC machine.The effects of the air flow on the morphology ofα1-Al particles,mechanical properties and thermal conductivity of rheo-HPDC samples were studied.The results show that the excellent slurry of the alloy could be obtained with the air flow exceeding3L/s.Rheo-HPDC samples that were produced with the air flow of5L/s had the maximum UTS,YS,elongation,hardness and thermal conductivity of261MPa,124MPa,4.9%,HV99and153W/(m·K),respectively.Rheo-HPDC samples show improved properties compared to those formed by HPDC,and the increasing rates of UTS,YS,elongation,hardness and thermal conductivity were20%,15%,88%,13%and10%,respectively.

Effect of Chromium on CCT Diagrams of Novel Air-Cooled Bainite Steels Analyzed by Neural Network

The quantitative effects of chromium content on continuous cooling transformation （CCT） diagrams of novel air-cooled bainite steels were analyzed using artificial neural network models. The results showed that the chromium may retard the high and medium-temperature martensite transformation.

3D Eddy Current and Temperature Field Analysis of Large Hydro-generators in Leading Phase Operations

As a common practice,a large hydro-generator will operate in leading phase conditions to absorb the reactive power of the power grid.However,the accurate and precise prediction of the leading phase operation capacity of a large hydro-generator has always been a formidable challenge to engineers and academicians because it is extremely hard to compute the eddy currents and losses as well as the local overheating in the pressure plate and finger.To address this problem,a full three dimensional(3D)finite element model and method of the coupled eddy current and temperature fields in the end region of a large hydro-generator are developed.The equivalent medium parameters used in the computations are comprehensively discussed.Moreover,some numerically based solution methodologies for accurate computation of the field and armature currents under different leading phase conditions are proposed.Numerical results on the coupled eddy current and temperature fields in the end regions of a 250 MW hydro-generator confirm positively the feasibility of the present work.

Research on remote hydro-generator sets diagnosis system

A type of remote monitoring and diagnosis system is brought forward which based on Matlab Web Server.Firstly,wavelet packet decomposition is introduced to acquire energy features of which reflect hydrogenerator sets performance to be Feature Parameter.Then these Feature Parameters can be adopted as BP Neural Network input variable to realize fault diagnosis.Most of all,it is the first time to adopt Matlab Web Server to hydro-generator sets faults diagnosis field to implement distributed remote monitoring and diagnosis system.Therefore,remote diagnosis application is independent from the OS used on server side.There is no need for software maintenance by clients.And clients can finish remote diagnosis by Web Browser and without installation of Matlab-software.Client users can monitor and diagnose hydro-generator sets by Browser.Finally,further research work is pointed out such as hydro-generator sets fault modeling,accelerating BP Neural Network learning speed and convergence property,improving data transfer speed of Matlab Web Server to meet the needs of real-time diagnosis for hydropower generator sets.

Feasibility Analysis of Back-Pressure Steam Feeding Water Pump for Direct Air-Cooled Unit

As the performance of an air-cooled condenser is apt to be affected by the fluctuating ambient condition, some difficulties are brought to the use of a steam feeding water pump in an air-cooled unit. This paper introduces a new design of for steam feeding the water pump of an air-cooled unit using the back-pressure steam turbine as the prime motor. Using variable condition analysis on a 600 MW direct air-cooled unit, and with consideration of the effect on the ambient conditions, the feasibility, economy, and adaptability of the design are verified.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Physical Properties of Crushed Air-cooled Blast Furnace Slag and Numerical Representation of Its Morphology Characteristics

Physical properties and geometrical morphologies of crushed air-cooled blast furnace slag （SCR） and crushed limestone （LCR） were comparatively investigated. The shape, angularity, surface texture and internal pore structure of aggregate particles for different size and gradation were numerically represented by sphericity （ψ） and shape index （SI）, angularity number （AN）, index of aggregate particle shape and texture （IAPST）, porosity and pore size, respectively. The results show that SCR is a porous and rough aggregate. Apparent density, void, water absorption and smashing index of SCR are obviously higher than those of LCR with the same gradation, respectively. However, bulk density of SCR is lower than that of LCR with the same gradation. SI, AN, IAPST and porosity of SCR are obviously higher than those of LCR with the same gradation, respectively. The smaller particle size of SCR, the larger of its AN, IAPST and porosity.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

Effect of Crushed Air-cooled Blast Furnace Slag on Mechanical Properties of Concrete

Morphology characteristics of mix aggregates with crushed air-cooled blast furnace slag（SCR） and crushed limestone（LCR） with 5-20 mm and 20-40 mm gradation were represented by numerical parameters including angularity number（AN） and index of aggregate particle shape and texture（IAPST）.The effect of mix aggregates containing SCR on compressive strength and splitting tensile strength of concrete was investigated.Fracture characteristics of concrete,interfacial structure between aggregates and matrix were analyzed.The experimental results show that porous and rough SCR increases contact area with matrix in concrete,concave holes and micro-pores on the surface of SCR are filled by mortar and hydrated cement paste,which may increase interlocking and mechanical bond between aggregate and matrix in concrete.SCR can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with LCR.The increase of AN and IAPST of aggregate may enhance mechanical properties of concrete.

Quantitative analysis of Ni effect on CCT diagrams of novel air-cooled bainite steels using artificial neural network models

The quantitative effect of Ni content on continuous cooling transformation （CCT） diagrams of novel air-cooled bainite steels was analyzed using artificial neural network models. The results showed that Ni may retard the high- and medium-temperature transformation and martensite transformation. The results conform to the materials science theories.

The Experimental Investigation of Recirculation of Air-Cooled System for a Large Power Plant

The paper introduces thermal buoyancy effects to experimental investigation of wind tunnel simulation on direct air-cooled condenser for a large power plant. In order to get thermal flow field of air-cooled tower, PIV experiments are carried out and recirculation ratio of each condition is calculated. Results show that the thermal flow field of the cooling tower has great influence on the recirculation under the cooling tower. Ameliorating the thermal flow field of the cooling tower can reduce the recirculation under the cooling tower and improve the efficiency of air-cooled condenser also.

Influence of thermal flow field of cooling tower on recirculation ratio of a direct air-cooled system for a power plant

In order to get thermal flow field of direct air-cooled system,the hot water was supplied to the model of direct air-cooled condenser(ACC). The particle image velocimetery (PIV) experiments were carried out to get thermal flow field of a ACC under different conditions in low velocity wind tunnel,at the same time,the recirculation ratio at cooling tower was measured,so the relationship between flow field characteristics and recirculation ratio of cooling tower can be discussed. From the results we can see that the flow field configuration around cooling tower has great effects on average recirculation ratio under cooling tower. The eddy formed around cooling tower is a key reason that recirculation produces. The eddy intensity relates to velocity magnitude and direction angle,and the configuration of eddy lies on the geometry size of cooling tower. So changing the flow field configuration around cooling tower reasonably can decrease recirculation ratio under cooling tower,and heat dispel effect of ACC can also be improved.

Water, Air Emissions, and Cost Impacts of Air-Cooled Microturbines for Combined Cooling, Heating, and Power Systems： A Case Study in the Atlanta Region

The increasing pace of urbanization means that cities and global organizations are looking for ways to increase energy efficiency and reduce emissions. Combined cooling, heating, and power （CCHP） systems have the potential to improve the energy generation efficiency of a city or urban region by providing energy for heating, cooling, and electricity simultaneously. The purpose of this study is to estimate the water consumption for energy generation use, carbon dioxide （CO2） and NOx emissions, and economic impact of implementing CCHP systems for five generic building types within the Atlanta metropolitan region, under various operational scenarios following the building thermal （heating and cooling） demands. Operating the CCHP system to follow the hourly thermal demand reduces CO2 emissions for most building types both with and without net metering. The system can be economically beneficial for all building types depending on the price of natural gas, the implementation of net metering, and the cost structure assumed for the CCHP system. The greatest reduction in water consumption for energy production and NOx emissions occurs when there is net metering and when the system is operated to meet the maximum yearly thermal demand, although this scenario also results in an increase in greenhouse gas emissions and, in some cases, cost. CCHP systems are more economical for medium office, large office, and multifamilv residential buildings.

The Selection of Cooling Systems of Giant Hydro-Generators

The selection of cooling system for hydro-generator in Ertan Hydropower Station is reviewed in this paper. The new viewpoint on air-cooled system of hydraulic generator of recent years is analyzed and described. That is, "Full air-cooled system is always preferred to

Thermal Management of Air-Cooling Lithium-Ion Battery Pack

Lithium-ion battery packs are made by many batteries, and the difficulty in heat transfer can cause many safety issues. It is important to evaluate thermal performance of a battery pack in designing process. Here, a multiscale method combining a pseudo-two-dimensional model of individual battery and three-dimensional computational fluid dynamics is employed to describe heat generation and transfer in a battery pack. The effect of battery arrangement on the thermal performance of battery packs is investigated. We discuss the air-cooling effect of the pack with four battery arrangements which include one square arrangement, one stagger arrangement and two trapezoid arrangements. In addition, the air-cooling strategy is studied by observing temperature distribution of the battery pack. It is found that the square arrangement is the structure with the best air-cooling effect, and the cooling effect is best when the cold air inlet is at the top of the battery pack. We hope that this work can provide theoretical guidance for thermal management of lithium-ion battery packs.

Research and Demonstration of Direct Air-Cooling System for 600-MW Fossil-Fired Power Plants

Given the distribution feature of resources such as coal and water, the requirements for the development of Chinese power industry, and the fact of monopoly by foreign companies, it is very necessary and significant to independently research and develop air-cooling technologies. Through experimental research, simulative calculation, process and equipment development, field tests and a demonstration project, the design and operation technologies for air-cooling system are grasped and relevant key equipment is developed. The results of the demonstration project show that the technical indicators for the air-cooling system have met or exceeded the design requirements. Part of the research results have been incorporated into the relevant national design standards. The technologies developed have been applied to more than 23 sets of thermal power units of or above 600 MW in China.