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  • 2018 Volume 38 Issue 5
    Published: 15 May 2018
      
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  • Design and Development of a 660 MW High Efficiency Ultra-supercritical Double-furnace CFB Boiler
    ZHANG Man, CAI Runxia, JIANG Xiaoguo, LÜ Junfu, GAO Xinyu, YANG Hairui
    2018, 38(5): 341-346.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The design principle of a 660 MW high efficiency ultra-supercritical circulating fluidized bed (CFB) boiler was discussed, while its main performance parameters were predicted. The boiler adopts two parallel furnaces, and each furnace has an independent air supply system. External heat exchangers are used in the scheme, while panel superheaters and panel reheaters are arranged in the upper furnace. To reduce the deviation of steam temperature caused by incomplete symmetry of both the temperature and mass flow of flue gas and bed material in the two independent loops, the air supply rate, coal feeding rate and bottom ash discharging rate are controlled, steam mixture headers are used, while the flow direction of inlet flue gas in the backpass is changed. Results show that the design scheme with double furnaces can well solve the problem of temperature deviation, and ensure the positive flow characteristics in waterwalls even at low mass flux. Additionally, the auxilary power comsuption can also be reduced due to lower water pump head.
  • Cold-state Experimental Study and Prediction on Circulation Flow Rate of Particles in a Double-circulating Fluidized Bed
    CHEN Hongwei, YANG Xin, LIANG Zhanwei, XU Wenliang, SUN Chao
    2018, 38(5): 347-352.
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    Cold-state experimental tests were conducted on a self-built double-circulating fluidized bed to study the effects of following factors on the circulating flow rate of particles, such as the static bed height, average size of particles, wind speed in bubbling bed and fast bed as well as the air distribution ratio, etc., following which an empirical correlation was proposed for above control parameters and the circulation flow rate. Results show that the circulating flow rate varies little with the increase of wind speed in the bubbling bed, which increases with the rise of primary air ratio and total fluidization wind speed in the fast bed, and when the primary air ratio and total fluidization wind speed get up to a certain value, the growth trend gradually slows down. The circulating flow rate increases with rising height of bubbling bed and with reducing average size of particles, with the latter one effecting more. In addition, the empirical correlation proposed can be used to predict the circulating flow rate of particles well.
  • A New Judgement Method for Combustion Characteristics of Blended Coal at Constant Temperature Based on Coal Properties
    YUE Shuang, WANG Chunbo, SI Tong, LI Yipeng, WANG Ziming
    2018, 38(5): 353-359.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A new judgement method was proposed for combustion characteristics of blended coal at constant temperature based on coal properties. By introducing the judgement index FZ as a comprehensive expression of coal properties, and by defining the judgement indexes D1, D2, and S as the quantitative reflection of combustion characteristics, a judgement curve was drawn, based on which, the effects of FZ on D1, D2, and S were studied under different working conditions. With the help of a self-developed thermogravimetric analyzer, and by the new judgement method, the influence law of coal quality on the combustion characteristics has been analyzed under different conditions, during which the reliability of the new judgement method is proved to be effective. Results show that FZ covers the parameters of main coal properties, while D1, D2, and S successfully express the combustion characteristics in different stages. With the variation of temperature and oxygen concentration, the slope of D1, D2, and S curves can accurately reflect the effect degree of coal properties on the combustion characteristics.
  • Effect of Reaction Mechanism on NO Emission of a Gas Turbine at High Pressures Calculated with CFD
    XI Zhongya, FU Zhongguang
    2018, 38(5): 360-365.
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    Four reaction mechanisms, including GRI3.0, Skeletal mech, 8-steps mech, and GRI3.0_modify, were used to calculate the temperature field and the distributions of NO production rate and NO mole fraction in the lean premixed swirl flames of methane as well as the outlet NO concentration of the gas turbine combustor, following which, a comparison was made on the outlet NO concentration between calculated results and actual measurements. Results show that for all mechanisms, the NO generation is mainly located on the surface of flame, and prompt NO, N2O and NNH are the major sources of NO. In terms of distributions of NO production rate and mole fraction, the results from GRI3.0 and Skeletal mech are almost the same; the result from GRI3.0_modify is higher than that from GRI3.0 and Skeletal mech, while the result from 8-steps mech is obviously lower than other mechanisms. The outlet NO concentrations from GRI3.0, Skeletal mech and GRI3.0_modify are in accordance with experimental results accurately; with accurate prediction results of NO emission, Skeletal mech requires less calculation time (almost half of GRI3.0); GRI3.0_modify presents higher accuracy than GRI3.0 in predicting NO emission; 8-steps mech produces a relatively large deviation from actual measurements.
  • Research on Wall Cooling Structure and Cooling Performance of a Single Cylinder H2-O2 Combustion Chamber
    GAO Jiajia, LU Kun, WEI Xiaolin
    2018, 38(5): 366-373.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A novel single cylinder H2-O2 combustion chamber with wall cooling was proposed based on the new hydrogen and oxygen gas turbine thermal cycle system. The wall cooling structure was optimized by CFD, based on which, experimental studies were carried out on the water cooling characteristics. Results show that, the cooling performance of the cooling structure with small depth-to-width ratio is better than that with high depth-to-width ratio. The wall temperatures of the combustion chamber are all below 400 K at different loads. In the primary zone around x=0.035 m, the maximum local wall heat flux is about 246.5 kW/m2 for the cooling water flow rate of 0.8 m3/h; the local wall heat flux increases with the rise of cooling water flow rate.
  • A Method for Predicting Bearing Health Degradation Trend of Wind Turbines
    DONG Xinghui, ZHANG Guang, CHENG Youxing, WANG Shuai
    2018, 38(5): 374-379.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking the bearing of a wind turbine as an object of study, using the monitored parameters by supervisory control and data acquisition (SCADA), the correlation coefficient between monitored parameters and bearing temperatures was calculated and normalized to obtain the influence weight, and subsequently a model for degradation trend of bearing health was established. The degradation trend with non-steady characteristics was decomposed by modified ensemble empirical mode decomposition (EEMD) to acquire several relatively steady components, and then each component was predicted by time series neural network, and final prediction results were formed by superposition of the predicted results of all components. Results show that the method proposed has higher prediction accuracy, which helps to improve the degree of conformity with actual degradation curves.
  • Fault Analysis of a Cracked Rotor Based on Morphological Characteristics of Axis Orbits
    XIANG Ling, ZHANG Yue
    2018, 38(5): 380-385.
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    With the aid of dynamic model of a cracked rotor, a crack fault diagnosis method was proposed based on the change of morphological characteristics of axis orbits considering the variable stiffness. The morphological characteristics of axis orbits were analyzed when the rotor passing through the 1/3 and 1/2 subcritical speed. Results show that the shape and offset direction of inner loops in axis orbits change with the rotating speed around the 1/3 and 1/2 subcritical speed, and the offset direction varies in a certain angle. The change rule of axis orbits provides a new method for judgment of crack faults, thus the efficiency of fault diagnosis is improved.
  • Effects of Immersed Tubes on Movement and Heat Transfer of Particles in a Spouted Bed and Numerical Simulation of the Tube Wall Abrasion
    LI Bin, MA Mengxiang, ZHANG Lei, YU Yang, CHEN Cuiling
    2018, 38(5): 386-393.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A microscopic study was conducted on the spouted bed with immersed tubes by coupling the discrete element method with computational fluid mechanics, so as to analyze the effects of immersed tubes on the movement and heat transfer of particles in the spouted bed, and to quantitatively study the abrasion of relevant immersed tube walls. Results show that immersed tubes can effectively reduce the fluctuation of bed height, shorten the time to form a stable spouted fluidization in the bed, enhance the convective gas-solid heat transfer, improve the mean temperature of particles in the spouted bed, promote the collision of particles, and therefore make the temperature distribution of particles become more uniform. Heaviest erosion occurs at the bottom region near the nozzle and the regions close to the wall suffer the slightest erosion.
  • Effects of Diluents on Pollutant Emission from Syngas Combustion
    XI Jianfei, GU Zhongzhu, YUAN Ye, ZHANG Xianpeng
    2018, 38(5): 394-399.
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    Diffusion combustion experiments of syngas were carried out on a self-developed test rig, so as to study the effects of H2/CO volume ratio on the flame shape and pollutant emission, and to analyze the variation law and causes of NO & CO emission indexes in the syngas flame with diluents CO2, N2 and Ar, respectively. Results show that at the H2/CO volume ratio of 10:0 (pure H2) or 9:1, a pale yellow flame would be generated, whereas, at the H2/CO volume ratio of 8:2, blue color would occur. The flame color gradually changes from pale blue to bright blue, and the clarity of flame improves with rising proportion of CO in the syngas. With the rise of H2/CO volume ratio, the NO emission index increases and that of CO reduces. All the three kinds of diluents can reduce the NO emission index, in which CO2 works best, while N2 and Ar have basically the same effect. It is also found that the addition of diluents can increase the CO emission index, and with the rise of dilution ratio, the CO emission increases rapidly. The effect of diluents on NO & CO emission index weakens with the increase of H2/CO volume ratio.
  • Two-way Fluid-structure Interaction Analysis of Tower Shadow Effect of a 5 MW Wind Turbine
    LI Li, PAN Yang, HU Danmei
    2018, 38(5): 400-405.
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    Taking the NREL 5 MW wind turbine as an object of study, a two-way fluid-structure interaction numerical simulation was carried out to analyze the effects of tower shadow on large-scale wind turbines. Results show that the tower enhances the fluctuation of the aerodynamic load of turbine blades. The fluctuation of torque and thrust forces on the rotor would be more than three times compared with the condition without tower, as a result, the deformation and equivalent stress of the rotor and blades also increase and fluctuate observably, which means that the tower makes the rotor work in a worse condition. In summary, the tower shadow effect has some negative influence on the working stability of wind turbines.
  • Optimization of TMD Parameters Based on MIGA for a Floating Wind Turbine
    ZHOU Hongjie, DING Qinwei, LI Chun, HAO Wenxing, YU Wan
    2018, 38(5): 406-411.
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    Taking the ITI Barge floating wind turbine platform as an object of study, the configuration parameters of tuned mass damper (TMD) matched for the wind turbine were optimized and designed based on global multi-objective optimization algorithm with multi-island genetic algorithm (MIGA). After resetting the TMD parameters with optimal solution, the control effect of optimized TMD controlled floating wind turbine were compared with that of uncontrolled and traditional TMD controlled wind turbine. Results show that, both the tower top displacement and the platform roll first reduce and then increase with rising TMD mass; the damping variation has a certain influence while the stiffness change affects little on above two parameters. The roll standard deviation of optimized TMD controlled floating wind turbine is respectively 37% and 63% of the uncontrolled and traditional TMD controlled one, and the top displacement standard deviation is respectively 42% and 67% of the latter two accordingly.
  • Performance Analysis of a Pre-compression S-CO2 Brayton Cycle
    WANG Bingbing, QIAO Jiafei
    2018, 38(5): 412-417.
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    To analyze the performance of a pre-compression S-CO2 Brayton cycle, a mash model was set up, based on which, the effect of key cycle parameters on the cycle efficiency was studied, the influencing mechanism was explored, the optimum pressure ratio and pre-compression pressure were calculated, while a comparison was made between the pre-compression and re-compression S-CO2 Brayton cycle. Results show that the cycle efficiency is related to the pre-compression pressure, and there exists an optimal pre-compression pressure, when highest cycle efficiency could be achieved. The cycle efficiency reduces with the rise of minimum cycle temperature, which increases with the rise of maximum temperature and pressure. Under same conditions, the efficiency of the pre-compression S-CO2 Brayton cycle is slightly higher than that of the re-compression S-CO2 Brayton cycle, but the difference is not obvious.
  • Study on Two-phase Flow Resistance in a Rod Bundle Channel Based on Separated Models
    JIN Guangyuan, HAN Yueyang
    2018, 38(5): 418-424.
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    The flow resistance of air-water two-phase flow in a 3×3 rod bundle was experimentally investigated at ambient temperature and pressure. Five normally used separated models were chosen to predict the frictional pressure drop in the rod bundle, after which, an empirical formula was proposed for calculating the parameter C in the Lee-Lee model. Results show that the prediction values of Chisholm model are greatly dispersed, but the average error is relatively small, which can be used to estimate the frictional pressure drop of two-phase flow in rod bundle channels. The prediction errors of Mishima-Hibiki and Zhang-Mishima model are all above 30% for different flow patterns, because these models are set up for small-or micro-channels. The Sun-Mishima model has poor adaptability to rod bundle channels, since too many influence factors are involved in its empirical formula. In addition, the prediction results of modified Lee-Lee model agree well with experimental data.