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.

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.

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.

Design of Balanced Reactor Welded with Water-Cooled Aluminum Busbars

A new process of welding aluminum water-cooled busbars is proposed, It can not only reduce the weight and cost, but also improve the dynamic and thermal stability. Furthermore~ both finite element method analysis and a prototype test testify the advantages of the design which is not limited by load current and provides a new approach for water-cooled reactors.

Analysis and optimization of heat loss for water-cooled furnace roller

A heat transfer model of furnace roller cooling process was established based on analysis of furnace roller＇s structure. The complicated model was solved with iteration planning algorithm based on Newton search. The model is proved logical and credible by comparing calculated results and measured data. Then, the relationship between water flow velocity, inlet water temperature, furnace temperature and roller cross section temperature, outlet water temperature, water temperature rise, cooling water heat absorption was studied. The conclusions and recommendations are mainly as follows： l） Cooling water temperature rise decreases with the increase of water flow velocity, but it has small relationship with inlet water temperature; 2） In order to get little water scale, inlet water temperature should be controlled below 30 ℃. 3） The cooling water flow velocity should be greater than critical velocity. The critical velocity is 0.07 m/s and water flow velocity should be controlled within 0.4-0.8 m/s. Within this velocity range, water cooling efficiency is high and water temperature rise is little. If cooling water velocity increases again, heat loss will increase, leading to energy wasting.

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.

Numerical Simulation on Subcooled Boiling Heat Transfer Characteristics of Water-Cooled W/Cu Divertors

In order to realize safe and stable operation of a water-cooled W/Cu divertor under high heating condition,the exact knowledge of its subcooled boiling heat transfer characteristics under different design parameters is crucial.In this paper,subcooled boiling heat transfer in a water-cooled W/Cu divertor was numerically investigated based on computational fluid dynamic（CFD）.The boiling heat transfer was simulated based on the Euler homogeneous phase model,and local differences of liquid physical properties were considered under one-sided high heating conditions.The calculated wall temperature was in good agreement with experimental results,with the maximum error of 5%only.On this basis,the void fraction distribution,flow field and heat transfer coefficient（HTC）distribution were obtained.The effects of heat flux,inlet velocity and inlet temperature on temperature distribution and pressure drop of a water-cooled W/Cu divertor were also investigated.These results provide a valuable reference for the thermal-hydraulic design of a water-cooled W/Cu divertor.

Preparation of Al-Zn-Mg-Cu alloy semisolid slurry through a water-cooled serpentine pouring channel

The semisolid slurry of Al-Zn-Mg-Cu alloy was prepared through a self-designed water-cooled copper serpentine pouring channel(WSPC) machine. Influences of pouring temperature, the number of turns and the cooling water flow rate on the microstructure of the semisolid Al-Zn-Mg-Cu alloy slurry were investigated. The results show that the semisolid Al-Zn-Mg-Cu alloy slurry with satisfactory quality can be generated by the WSPC when the pouring temperature is in the range between 680 ℃ and 700 ℃. At a given pouring temperature, the average grain size of primary α-Al decreases and the shape factor increases with the increase of the number of turns. When the cooling water flow rate is 450 L·h^(-1), the obtained semisolid slurry is optimal. During the preparation of the semisolid Al-Zn-Mg-Cu alloy slurry with low superheat pouring, the alloy melt has mixed inhibition and convection flow characteristics by "self-stirring". When the alloy melt flows through the serpentine channel, the chilling effect of the inner wall of the channel, the convection and mixed inhibition of the alloy melt greatly promote the heterogeneous nucleation and grain segregation. This effect destroys the dendrite growth mode under traditional solidification conditions, and the primary nuclei gradually evolve into spherical or nearspherical grains.

Optimization of the Water-Cooled Structure for the Divertor Plates in EAST Based on an Orthogonal Theory

An orthogoual experimental scheme was designed for optimizing a water-cooled structure of the divertor plate. There were three influencing factors： the radius R of the water- cooled pipe, and the pipe spacing L1 and L3. The influence rule of different factors on the cooling effect and thermal stress of the plate were studied, for which the influence rank was respectively R 〉 L1 〉 L3 and L3 〉 R 〉 L1. The highest temperature value decreased when R and L1 increased~ and the maximum thermal stress value dropped when R, L1 and L3 increased. The final optimized results can be summarized as： R equals 6 mm or 7 mm, L1 equals 19 mm, and L3 equals 20 mm. Compared with the initial design, the highest temperature value had a small decline~ and the maximum thermal stress value dropped by 19~ to 24~. So it was not ideal to improve the cooling effect by optimizing the geometry sizes of the water-cooled structure, even worse than increasing the flow speed, but it was very effective for dropping the maximum thermal stress value. The orthogoaal experimental method reduces the number of experiments by 80%, and thus it is feasible and effective to optimize the water-cooled structure of the divertor plate with the orthogonal theory.

Analysis of surface cracking in water-cooled rolls and heat transfer between furnace chamber and rolls in a direct flame furnace

In the direct fired furnace of a continuous annealing line, seal rolls are susceptible to deformation that leads to surface defects of steel strips. According to failure analysis, the reasons include improper structural design and heat imbalance. An improved design has been proposed to reduce stress concentration and thermal radiation. A heat transfer model has been employed to determine the proper water flow rate for roll cooling. Industrial application proves that seal rolls with the new design has less deformation and longer service life.

Fully Immersing Water-Cooled Radial Slab Laser and its Incoherent Beam Combination

A novel scheme of fully immersing water cooling is proposed for a Nd：glass radial slab laser. The slab medium is entirely immersed in the circulating water Ailing the pumping cavity, which enables much lower temperature and reasonably smaller thermal gradient in the slab medium. The radial slab is symmetrically and synchronously pumped by eight flash lamps, and produces multi-output beams with a total energy of 469md. Incoherent beam combination property of the multi-output beams is also investigated. The approach suggested here provides a way of scaling the slab lasers to much higher output levels and also a convenience for beam combinations.

The Corrected Simulation Method of Critical Heat Flux Prediction for Water-Cooled Divertor Based on Euler Homogeneous Model

An accurate critical heat flux（CHF） prediction method is the key factor for realizing the steady-state operation of a water-cooled divertor that works under one-sided high heating flux conditions.An improved CHF prediction method based on Euler＇s homogeneous model for flow boiling combined with realizable k-ε model for single-phase flow is adopted in this paper in which time relaxation coefficients are corrected by the Hertz-Knudsen formula in order to improve the calculation accuracy of vapor-liquid conversion efficiency under high heating flux conditions.Moreover,local large differences of liquid physical properties due to the extreme nonuniform heating flux on cooling wall along the circumference direction are revised by formula IAPWSIF97.Therefore,this method can improve the calculation accuracy of heat and mass transfer between liquid phase and vapor phase in a CHF prediction simulation of water-cooled divertors under the one-sided high heating condition.An experimental example is simulated based on the improved and the uncorrected methods.The simulation results,such as temperature,void fraction and heat transfer coefficient,are analyzed to achieve the CHF prediction.The results show that the maximum error of CHF based on the improved method is 23.7%,while that of CHF based on uncorrected method is up to 188%,as compared with the experiment results of Ref.[12].Finally,this method is verified by comparison with the experimental data obtained by International Thermonuclear Experimental Reactor（ITER）,with a maximum error of 6% only.This method provides an efficient tool for the CHF prediction of water-cooled divertors.

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

Improvement of microstructure and mechanical properties of Al−Cu−Li−Mg−Zn alloys through water-cooling centrifugal casting technique

The microstructure and mechanical properties of as-cast Al−Cu−Li−Mg−Zn alloys fabricated by conventional gravity casting and centrifugal casting techniques combined with rapid solidification were investigated.Experimental results demonstrated that compared with the gravity casting technique,the water-cooling centrifugal casting technique significantly reduces porosity,refinesα(Al)grains and secondary phases,modifies the morphology of secondary phases,and mitigates both macro-and micro-segregation.These improvements arise from the synergistic effects of the vigorous backflow,centrifugal field,vibration and rapid solidification.Porosity and coarse plate-like Al13Fe4/Al7Cu2Fe phase result in the fracture before the gravity-cast alloy reaches the yield point.The centrifugal-cast alloy,however,exhibits an ultra-high yield strength of 292.0 MPa and a moderate elongation of 6.1%.This high yield strength is attributed to solid solution strengthening(SSS)of 225.3 MPa,and grain boundary strengthening(GBS)of 35.7 MPa.Li contributes the most to SSS with a scaling factor of 7.9 MPa·wt.%^(-1).The elongation of the centrifugal-cast alloy can be effectively enhanced by reducing the porosity and segregation behavior,refining the microstructure and changing the morphology of secondary phases.

Creation and Development of Turbo-generators with Water-Cooled Stator and Rotor Windings in Shanghai Electrical Machinery Mfg Works

1. An Overview of Manufacture and Operation A turbine generator utilizing a new technology of electrical machinery industry, i.e. the windings of its stator and rotor all being inner water-cooled, was first successfully created in China and was known afterwards as a turbine generator with watercooled stator and rotor windings (Abbrev, TGWSR). The teachers from Zhejiang University came to Shanghai between

Flow Field and Temperature Field of Water-Cooling-Type Magnetic Coupling

At present, the water-cooling simulation of the water-cooled magnetic coupler is based on the water-cooled motor and the hydraulic coupler, which cannot accurately characterize the temperature distribution of the rotating watercooled coupling of the coupler. Focusing on rotating water cooling radiating, the present paper proposes simulating the water cooling temperature field as well as the flow field through the method of combining fluid-solid coupled heat transfer and MRF(Multiphase Reference Frame). In addition, taking an 800 kW magnetic coupling as an example, the paper optimizes the shape, number, cooling water inlet speed? and so on? of the cooling channel. Considering factors such as the complete machine’s temperature, and drag torque, it is proved that the cooling e ect is best when there are 36 involute curved channels and when the inlet speed is 3 m/s. Further, through experiments, the actual temperature values at six di erent positions when 50 kW and 70 kW thermal losses di er are measured. The measured values agree with the simulation results, proving the correctness of the proposed method. Further, data have been collected during the entire experimental procedure? and the variation in the coupling’s temperature is analyzed in depth, with the objective of laying a foundation for the estimation of the inner temperature rise as well as for the optimization of the structural design.

DEVELOPMENT OF SINGLE-PHASED WATER-COOLING RADIATOR FOR COMPUTER CHIP

In order to cool computer chip efficiently with the least noise, a single phase water-cooling radiator for computer chip driven by piezoelectric pump with two parallel-connection chambers is developed. The structure and work principle of this radiator is described. Material, processing method and design principles of whole radiator are also explained. Finite element analysis （FEA） software, ANSYS, is used to simulate the heat distribution in the radiator. Testing equipments for water-cooling radiator are also listed. By experimental tests, influences of flowrate inside the cooling system and fan on chip cooling are explicated. This water-cooling radiator is proved more efficient than current air-cooling radiator with comparison experiments. During cooling the heater which simulates the working of computer chip with different power, the water-cooling radiator needs shorter time to reach lower steady temperatures than current air-cooling radiator.

Mathematical model on heat transfer of water-cooling steel-stick bottom electrode of DC electric arc furnace

For predicting and controlling the melted depth of bottomelectrode during the process of steelmaking, the water-cooling steel-stick electrode is taken as an example, to analyze the process ofheat transfer, then 3D mathematical model by control capacity methodis built. At the same time, the measurement on the melted depth ofbottom electrode is conducted which verified the correctness of thebuilt mathematical model. On the base of verification, all kinds ofkey parameters are calculated through the application and a series ofresults are simulated. Finally, the optimum parameters are found andthe service life of bottom electrode is prolonged.

Research on the Flow and Heat Transfer Characteristics of a Water-Cooling Plate in a Heat Dissipation System

The water-cooling heat dissipation technology can solve the heat dissipation and noise problems of the calculation plate.Therefore,the structural design of the water-cooling plate directly affects its flow and heat transfer characteristics,which restricts the promotion and application of the technology.To this end,the water-cooling plate of a heat dissipation system was taken as the research object,and its flow and heat transfer characteristics were numerical simulated and experimental studied.Through comparative analysis,the rationality of the numerical simulation method was verified.Based on this,three improved schemes of water-cooling plate structure were proposed and numerical simulation was carried out,and the optimal model was verified by experiments.The results of the study show that compared with the original water-cooling plate,the optimized water-cooling plate has increased internal flow velocity and distributes uniformly,increased heat transfer amount by 4.2%,and the average temperature of the calculation plate decreased by 5.3%.

Experimental study of destruction to porcine spleen in vivo by microwave ablation

AIM: To discuss the safety, feasibility and regularity of destruction to porcine spleen in vivo with congestion and tumescence by microwave ablation (MWA). METHODS: Ligation of the splenic vein was used to induce congestion and tumescence in vivo in five porcine spleens, and microwave ablation was performed 2-4 h later. A total of 56 ablation points were ablated and the ablation powers were 30-100 W. The ablation time (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 min) was performed at a power of 60 W. After ablation, the ablation size was measured in pigs A, C, D and E and spleen resection. In pig B, the ablation size was measuredand 2 ablation points were sent for pathology analysis and all tissues were sutured following ablation. Pig B was killed 1 wk later and the ablation points were sent for pathology analysis. Bleeding, tissue carbonization surrounding electrodes, and pathological changes were observed, and the effect on destruction volume relative to different ablation powers, times and positions was analyzed. RESULTS: The incidence of bleeding (only small amounts, < 20 mL) in the course of ablation was 5.4% (3/56) and was attributed to tissue carbonization surrounding electrodes, which also exhibited an incidence of 5.4% (3/56). The destruction volume was influenced by different ablation powers, times and points. It showed that the ablation lesion size increased with increased ablation time, from 1 to 10 min, when the ablation power was 60 W. Also, the ablation lesion size increased with the increase of ablation power, ranging from 30 to 100 W when the ablation time was set to 3 min. A direct correlation was seen between the destruction volume and ablation time by the power of 60 W (r = 0.97542, P < 0.0001, and also between the destruction volume and ablation powers at an ablation time of 3 min (r = 0.98258, P < 0.0001). The destruction volume of zone Ⅱ (the extra-2/3 part of the spleen, relative to the fi rst or second class vascular branches), which was near the hilum of the spleen, was noteably larger than the destruction volume of zoneⅠ(the intra-1/3 part of the spleen) which was distal from the hilum of the spleen (P = 0.0015). Pathological changes of ablation occurring immediately and 1 wk after MWA showed large areas of coagulation. Immediately following ablation, intact spleen tissues were observed in the areas of coagulation necrosis, mainly around arterioles, and there were no obvious signs of hydropsia and inflammation, while 1 wk following the ablation, the coagulation necrosis was well distributed and complete, as many nuclear fragmentations were detected, and there were obvious signs of hydropsia and inflammation.CONCLUSION: In vivo treatment of congestion and tumescence in the spleen using microwave ablation of water-cooled antenna is a safe and feasible method that is minimally invasive.