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    Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Stress Analysis on Complex Shrunk-on Rotor of Steam Turbines
    TAN Shangjiong, CHEN Gang, WANG Weizhe, CHEN Hanping
    2013, 33(8): 581-585.
    Abstract ( )   Knowledge map   Save
    The structural characteristics, temperature environment and mechanical load of a multi-stage disc-shared complex shrunk-on rotor for nuclear steam turbine were studied, while its stress and temperature distribution calculated using Abaqus finite element software under assembly and steady operation conditions. Simultaneously, the effect of magnitude of assembly interference between the disc and main shaft on operation safety of the rotor was analyzed. Results show that the maximum temperature on surface of the shrunk-on rotor may reach up to 250 ℃ in steady-state operation; from the inlet to the outlet, the rotor temperature decreases gradually along the axial direction; the temperature of last disc at outlet end is lower than 70 ℃; the effects of centrifugal load and thermal expansion on the contact stress are relatively obvious under steady-state operation condition; the reduction amplitude of contact stress produced by interference in the initial stage of assembly is relatively great during steady-state operation, however, under the existing magnitude of interference, safe operation of the shrunk-on rotor can still be guaranteed.
  • Steam Turbine and Gas Turbine
    Calculation of Turbine Rotor Temperature Based on Inertial Element
    YANG Yu, QI Hao, DENG Zhicheng, CHEN Gang
    2013, 33(8): 586-590.
    Abstract ( )   Knowledge map   Save
    The theory and calculation method of high-pressure rotor temperature field based on first-order inertia element were introduced, while the simplified iterative calculation formula used in the control system deduced. For a 1 000 MW ultra-supercritical steam turbine, its temperature field was calculated using finite element method, so as to verify the rationality to use the internal surface temperature of inner cylinder instead of the outer surface temperature of rotor in thermal stress monitoring. The average volume temperature and center temperature of high-pressure turbine rotor were calculated during the process of cold start, warm start, hot start, extreme hot start, and shutdown at sliding parameters by three methods, namely first-order inertia element, differential method, and definite element method, after which a comparison was made to the calculation precision of surface and center temperature difference of rotor among above three methods. Results show that the first-order inertial element method has a high calculation precision and is easy to use, which therefore may be taken as an effective method for temperature filed monitoring of turbine rotors.
  • Steam Turbine and Gas Turbine
    Study on Bending Stiffness of Curvic Couplings
    GE Qing, TAN Luyi, LI Yifeng, LI Pu
    2013, 33(8): 591-594.
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    For axially interrupted connection of rotor structure with curvic couplings, bending stiffness of the curvic couplings was calculated under the action of different pre-tightening forces using both theoretical and nonlinear contact analysis method based on 3D finite element, after which the stiffness corrective coefficient of curvic coupling was proposed in relation to the integrated structure of rotors, while the influence of key structural parameters on the bending stiffness analyzed. Results show that for obtaining a stable bending stiffness, it is necessary to keep the pre-tightening force being larger than the separating force induced by the bending moment; the stiffness corrective coefficient is slightly affected by both the inner and outer diameter of curvic couplings, which, however, decreases with increasing teeth number.
  • Steam Turbine and Gas Turbine
    Numerical Simulation on Inner Flow in a 90° Circular-sectioned Bend with Fore-end Valve
    WEI Zhi, WANG Yuzhang
    2013, 33(8): 595-599.
    Abstract ( )   Knowledge map   Save
    A 3D numerical simulation was carried out on inner flow in a 90° circular-sectioned bend with fore-end valve using large eddy simulation (LES) method, so as to obtain the flow field characteristics in different sections and the vortex structure in different radial cross sections at full open state of the butterfly valve, which were subsequently compared with particle image velocimetry (PIV) method. Results show that the LES method can well simulate the inner flow field in curved bend, and its result fits well with that of actual experiment; the influence of disturbance from butterfly valve on the inner flow field is relatively high in the area 20 mm above the curved bend center section, where the high speed region moves rearward; vortex structure is found in each section at angle θ=0; the vortex structure at outer side of curved bend is more obvious than at the inner side, and its position is relatively fixed.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    Study on Control Characteristics and Strategies of a 600 MW Supercritical Unit
    ZHANG Weijie, YANG Jingqi, LI Zhuolin, WANG Lin, YU Kang
    2013, 33(8): 600-605.
    Abstract ( )   Knowledge map   Save
    By analyzing the effects of fuel mass flow disturbance, feedwater mass flow disturbance and turbine control valve's opening disturbance on dynamic response of main steam pressure and separator outlet temperature of a supercritical power unit, corresponding dynamic characteristics and couplings of relative process variables are obtained. Based on theoretical analysis of the correlation among fuel demand, feedwater demand and fuel-water ratio, the dynamic and static relations between unit demand and boiler demand are put forward. The concept of integrated steam-water control is proposed for the supercritical power unit, of which the control strategy is optimized by adopting the variable setpoint, variable parameter and dynamic feed-forward control mode, so as to make the unit response follow AGC requirements steadily and rapidly, and subsequently guarantee stable operation of the supercritical power unit under variable parameters.
  • Automatical Controlling and Detecting Diagnosis
    Mechanical Fault Diagnosis of Fan Based on Wavelet Packet Energy Analysis and Improved Support Vector Machine
    XU Xiaogang, WANG Songling, LIU Jinlian
    2013, 33(8): 606-612.
    Abstract ( )   Knowledge map   Save
    To accurately diagnose the mechanical faults of fan, a new method was proposed based on wavelet packet energy analysis and improved support vector machine. Vibration signals of the fan were acquired on a 4-73 No.8D test bench under 13 different operating conditions, which were subsequently denoised, decomposed and reconstructed by wavelet packet to extract and obtain multipoint information fusion wavelet packet energy eigenvectors under various operating conditions. The sample set of above eigenvectors was trained and tested by improved support vector machine so as to diagnose and classify the mechanical faults of the fan. Results show that this method is able to effectively diagnose the category, severity and site of the fan mechanical faults with high diagnostic accuracy rate, short testing time and good online diagnosis performance.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Performance Evaluation on a Two-stage Low-temperature Gas-coolant Heater
    ZHANG Ruiqing, YANG Hairui, L Junfu
    2013, 33(8): 613-618.
    Abstract ( )   Knowledge map   Save
    For heat recovery purposes, it is an effective way to set up a low-temperature gas-coolant heater in the waste heat recovery system so as to reduce the exhaust temperature of the flue gas. An evaluation was carried out tostudy the performance of a 1 000 MW unit, where a two-stage gas-coolant heater was arranged respectively in the upstream of its electrostatic precipitator (ESP) and flue gas desulphurization (FGD) absorber. Results show that after the gas-coolant heater being put into operation, the heat rate of steam turbine reduces by 0.56% and the net coal consumption drops by 1.59 g/(kW·h), when the gas temperature is kept to be above the acid dew pont, resulting in reduced corrosion risk of relevant facilities; meanwhile, the water consumption in FGD system decreases by 39.75 t/h, under the premise of a guaranteed desulphurization efficiency; simultaneously, with an increased removal efficiency of ESP, the average dust concentration at ESP outlet drops to 14.05 mg/m3, which meets the requirements of the corresponding new national emission standards. The two-stage low-temperature gas-coolant heater will have a bright prospect in application as its enhanced effect in energy saving of unit, water saving of FGD system and dust removal of ESP.
  • Auxiliary Equipment Technology
    Calculation on Variable Condition Features and Optimum Vacuum of a Condenser Considering the Tide Impact
    XIA Lin, LIU Deyou, WANG Feng, JIAO Shiyuan, LUO Chengchun
    2013, 33(8): 619-624.
    Abstract ( )   Knowledge map   Save
    To overcome the deficiency of inaccurate calculation on variable condition features and optimum vacuum of a condenser due to negligence of tide impact, an improvement was carried out to the calculation model by considering the influence of sea level change caused by the tide on the cooling water flow, unit incremental power and pump power consumption, on the basis of a once-through sea water cooling system in 2×800 MW power units, after which corresponding calculation results were obtained and compared with and without consideration of tide impact under variable condition features. Results show that tide has significant impact on the condenser pressure, and the impact increases with the rise of inlet water temperature of condenser. Both the optimal operation mode of pump and corresponding optimum vacuum of condenser are different calculated in the case with and without consideration of tide impact. However, the optimal operation mode of pump calculated by considering tide impact can always guarantee better economic benefits of the unit.
  • Auxiliary Equipment Technology
    Study on Flow Path Design of Plate Condenser for Turbo-Generator Units
    XU Lei, ZHANG Tao, YANG Lijun, LIU Yun, DU Xiaoze
    2013, 33(8): 625-632.
    Abstract ( )   Knowledge map   Save
    To improve the water cooling capacity for 50 MW peak demand of a 300 MW direct air cooling thermal power unit, the feasibility of applying plate condenser to cool the exhaust steam was studied, based on which a design scheme was put forward by taking BR-05 herringbone plate as the heat exchanger component under the condition of given steam turbine backpressure, steam-side pressure drop and water-side pressure drop. The effects of following factors on the heat-transfer and flow characteristics of the plate condenser were analyzed, such as the steam-side plate spacing, water-side plate spacing, water-side flow path and water-side flow pattern, etc. Results show that the flow arrangement of condenser should take the plate structure into consideration;the water-side flow path should be designed to be less than three; the influence of water-side plate spacing of the performance of plate condenser is relatively small, while that of steam-side plate spacing is relatively great.
  • Auxiliary Equipment Technology
    Experimental Study on Pressure Drop of Falling Film Flow Across Tube Bundles in Rotated Square Arrangement
    LIU Hua, SHEN Shengqiang, CHEN Shi, GONG Luyuan, LIU Rui, CHEN Xue
    2013, 33(8): 633-636.
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    To study the effects of flow resistance in large-scale seawater desalination facility on the performance itself, an experimental setup was built to simulate the steam flow process in a horizontal-tube falling film evaporator, so as to analyze the influence of saturated steam temperature and spray density on the flow resistance in the tube bundle. The new parameter (Reynolds number of spray water) was used to fit the experimental results, and subsequently a pressure drop coefficient formula was obtained for the steam flow across the tube bundle in rotated square arrangement. Results show that for a constant steam flow and spray density, the pressure drop reduces with rising saturated steam temperature, and the error of differential pressure is within ±15% between predicted value and actual measurement.
    • Energy System Engineering
  • Energy System Engineering
    Structural Coefficient Calculation Equation for Regenerative System of a Coal-fired Power Unit
    LI Huijun, MA Chao, GU Kaina
    2013, 33(8): 637-642.
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    Based on matrix method and theory of partial differentiation, structural coefficient calculation equations for regenerative system of coal-fired power units were proposed under constant output conditions, with which the coefficient σi of structural bonds and coefficient βi of external bonds were calculated and analyzed throughout the regenerative system of an N-1000 unit. Results show that above coefficients can reflect the impact of local exergy loss and input exergy of all heaters on overall exergy loss and input exergy of the whole regenerative system, which therefore may serve as a reference for design optimization of coal-fired power units through improvements on local systems.
  • Energy System Engineering
    Experimental Research on Practical Rated-sliding Pressure Operation Curve of Power Units
    SHAO Feng, HUANG Qilong, DAI Weibao, MA Xiaofeng
    2013, 33(8): 643-647.
    Abstract ( )   Knowledge map   Save
    Taking a 600 MW air-cooling unit as an example, the economic, safe and practical rated-sliding pressure operation curve was sought by means of performance test based on energy consumption analysis of local system, without affecting the operating safety of the boiler and turbine. Meanwhile, a linear relationship was found between variation of the main and exhaust steam pressure through theoretical analysis under the sliding pressure operation mode in load management control. Finally the rated-sliding pressure operation curve was optimized by taking the exhaust steam pressure as variables to set the main steam pressure offset, which was subsequently verified with experimental data. Results show that the optimization scheme is proved to be effective for the unit in energy saving and consumption reduction.
  • Energy System Engineering
    Calculation on Coal-saving Benefits of a Flue Gas Waste Heat Recovery System
    HE Yihao, LI Bizheng, ZHU Qingguo, LIU Jianjiang, CHEN Zhengdong
    2013, 33(8): 648-652.
    Abstract ( )   Knowledge map   Save
    Coal-saving benefits of the flue gas waste heat recovery system for purposes of heat supply or condensate water heating were studied, based on the first and second law of thermodynamics and the heat balance diagram of steam turbine, while a comparison made between theoretical values of calculation examples and performance test data of actual engineering projects. Results show that the appropriate way for calculating the coal saving benefits is to firstly calculate the waste heat recovered from flue gas, then figure out the heat balance diagram for obtaining new heat rate of steam turbine, and finally calculate the saving value of coal consumption by the formula given out. To improve the coal-saving benefit, it is recommended to economize the steam as much as possible at bleed points of higher stages, but not to simply reduce the flue gas temperature, during performance design of flue gas waste heat recovery systems.
    • Material Science
  • Material Science
    Experimental Study on Low-cycle Fatigue Properties of Domestic Supercritical Turbine Rotor Steels
    L Fangming, WANG Kun, HUANG Shuhong, OUYANG Kunbei
    2013, 33(8): 653-658.
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    To study the static tension and low-cycle fatigue properties of domestic supercritical turbine rotor steels, monotonic tensile tests and total strain-controlled low-cycle fatigue tests were carried out to 5 domestic supercritical turbine rotor steels respectively at 540 ℃ and 593 ℃, after which corresponding mechanical properties and strain-life formulas were obtained based on the tests data. Results show that the Vickers hardness of the five rotor steels has reduced by about 15 at 540 ℃ and 20 at 593 ℃, indicating an obvious cyclic softening behavior.
  • Material Science
    Effects of Steam-side Oxide Scale on Creep Rupture Lifeof T91 Boiler Steel Tubes
    BIAN Caixia, ZHOU Keyi, ZHU Zhenglin, XU Jianqun
    2013, 33(8): 659-664.
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    A calculation model was built up for the creep rupture life of T91 steel tubes, with which the effects of steam-side oxide scale on the creep rupture life were analyzed quantitatively from the aspects of temperature and equivalent stress, while a comparison made to the calculation results obtained under different conditions of heat flux and tube size. Results show that the increase of metal temperature resulted from steam-side oxide scale is the main cause of creep rupture life reduction, and the rise of equivalent stress is the secondary one; a parabolic relationship exists between the reduction of creep rupture life and the thickness of steam-side oxide scale; the effect of steam-side oxide scale on the creep rupture life intensifies with the rise of heat flux; the steam-side oxide scale has greater influence on creep rupture life of tubes with smaller outside diameter but larger wall thickness.