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    Boiler Technology
  • Boiler Technology
    Experiment Study on the Ignition Method for Super-high Temperature Flames Based on Oxygen-enriched Combustion
    YAN Gaocheng
    2020, 40(4): 265-271. https://doi.org/10.19805/j.cnki.jcspe.2020.04.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To avoid the failures like coking and burning damage occurring in the internal-combustion pulverized coal burner of thermal power boilers, a super-high temperature flame ignition method was proposed based on the oxygen-enriched combustion. Hot-state experiments were conducted to study the performance of a super-high temperature flame generator under pure oxygen environment, with focus on the analysis of the potential relationship between the flame feature and the oxygen flow rate, following which, an external-combustion pulverized coal burner was presented to ignite the flowing lean coal powder, while experimental tests were carried out to study the effects of coal feed rate and oxygen flow rate on the pulverized coal combustion. Results show that with the help of pure oxygen, the super-high temperature flame generator can produce dazzle-white oil flame with the temperature up to 1 970 ℃, in which case, the maximum temperature of lean coal combustion reaches 947 ℃, the optimal concentration of pulverized coal is 0.35 kg/kg, and the optimal range of oxygen concentration in pulverized coal stream is 33%-37%.
  • Boiler Technology
    Co-pyrolysis Characteristics of Zhundong Coal and Corn Stalk and the Release of Related Gaseous Products
    ZHANG Ruipu, JIN Jing, ZHAO Bing, HANG Yixuan, LIU Zhongyi, ZHU Yizhou
    2020, 40(4): 272-281. https://doi.org/10.19805/j.cnki.jcspe.2020.04.002
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    Co-pyrolysis characteristics of Zhundong coal and corn stalk mixtures were studied by the way of TG-MS and in situ DRIFT to analyze the release of main small-molecule gas products (H2, CH4, CO and CO2), and to study the effects of functional groups on the release of gas products. Results show that the co-pyrolysis components of Zhundong coal and corn stalk interact with each other. When the blending ratio of Zhundong coal to corn stalk K is less than or equal to 0.4, the weight loss rate of the mixture would rise, and the promotion effect would reach the highest at K=0.2. In the case of K=0.2, the high concentration of alkali metals in corn stalk and the large amount of H radicals generated in the process would promote the progress of pyrolysis, and the presence of alkali metals could improve the yield of H2, CO and CO2, and enhance the demethanation reaction. Furthermore, the addition of corn stalk would promote the dehydrogenation process of functional groups, and the oxygen-containing functional groups could catalyze the cracking and recombination of semi-volatile organic components in the mixed samples.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Study on Rotordynamic Performance of a Self-adjusting Anti-stagnant Labyrinth Seal
    GU Qianlei, ZHANG Wanfu, WANG Jiarong, LI Chun, YANG Jiangang
    2020, 40(4): 282-289. https://doi.org/10.19805/j.cnki.jcspe.2020.04.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To suppress the circumferential flow in seal cavities and improve the stability of the seal system, a novel structure was proposed for the self-adjusting anti-stagnant labyrinth seal. The design of micro anti-stagnant nozzles on the seal tooth connecting adjacent seal cavities could automatically adjust the circumferential flow inside the cavity via the opposed jet caused by pressure differential of adjacent seal cavities. The identification method based on infinitesimal theory was applied to study the effects of the layout, inlet pressure and rotational speed of anti-stagnant nozzles on the rotordynamic performance of the self-adjusting anti-stagnant labyrinth seal, while a comparison was made between the new structure and traditional labyrinth seal. Results show that the effective damping coefficient of the new structure is 170% that of the traditional one at high whirling frequency, and its stability improves with the rise of inlet pressure and rotational speed. The anti-stagnant nozzles arranged in upstream could effectively improve the dynamic stability of the seal, which have little influence on the leakage flowrate.
  • Steam Turbine and Gas Turbine
    Effects of Nonlinear Characteristics on the Performance of a Gas Turbine Fuel Control System
    XIAO Wang, HUANG Dawen, LIU Gongyin, MA Yongfei, ZHANG Huisheng
    2020, 40(4): 290-296. https://doi.org/10.19805/j.cnki.jcspe.2020.04.004
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    Taking the gas turbine for driving purpose as an object of study, a model was established for the fuel control system considering the nonlinear characteristics of the electro-hydraulic servo actuator based on the hydro-mechanical theory, so as to investigate the effects of the following factors on the performance of the fuel control system, such as the dynamic behaviors of the fuel metering unit, the dead zone relay characteristics of the servo actuator, etc. Results show that the electro-hydraulic servo actuator can control the opening of the metering valve fast and precisely, and the constant differential pressure valve can maintain the pressure difference at 0.25 MPa. The width of dead zone has a great effect on the dynamic performance of the gas turbine.
  • Steam Turbine and Gas Turbine
    Experimental Study on Pollutants Formation Characteristics in a Biogas-fired Micro Gas Turbine Combustor
    LIU Aiguo, WANG Dong, CHEN Xuanren, YANG Yudong, ZENG Wen
    2020, 40(4): 297-304. https://doi.org/10.19805/j.cnki.jcspe.2020.04.005
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    An experimental study was conducted on the pollutants formation characteristics in a single-head combustor designed for the low-emission micro gas turbine combustor using medium and low calorific value gas fuels, while a comparative analysis was carried out on the effects of gas fuel category, injector location, jet depth and pilot-to-main fuel staged ratio on the pollutants emission behavior. Results show that the combustor has good fuel adaptability in the load range of 50%-100%. The maximum NOx emission is 76.9 mg/m3, which meets the requirements of environmental protection. The nozzle position, mixing distance and main fuel pressure would affect the mixing uniformity of fuel and air, and then affect the formation of pollutants. The change of pilot-to-main fuel staged ratio would affect the uniformity of temperature distribution in the combustor, and the pollutants emission reduces with the decrease of fuel fraction in pilot stage.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Experimental Study on Misalignment of Coupling Deflection Angle in Multi-span Rotor System
    PAN Honggang, PANG Zhiyuan, XIAO Zenghong, LI Li
    2020, 40(4): 305-310. https://doi.org/10.19805/j.cnki.jcspe.2020.04.006
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    To reduce the probability of misalignment faults occurring in the coupling of a multi-span rotor system, a test setup was established for the double-span three-support rotor system, based on which, finite element analysis was carried out for the rotor system, and subsequently the analysis results were compared with actual measurements for the critical speed. Meanwhile, the frequency spectrum, axis trajectory and time domain waveform of the rotor system were measured in the case of misalignment faults. Results show that with the increase of misalignment degree, the increase rate of the amplitude of fundamental frequency rises gradually when the rotor system passes through the critical speed, while the doubled frequency accompanies the whole speed-up process, and the axis trajectory presents an "8" shape. For the double-span three-support system, the rotor on opposite side of the coupling is less affected by the unsymmetrical vibration caused by the misalignment of the coupling.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Effects of the Parameters of Half-moon-shaped Baffles on the Friction Coefficient Along the Flow Path
    FENG Lele, TANG Guoli, Lü Junfu, WU Yuxin, ZHANG Yang, ZHANG Man
    2020, 40(4): 311-316. https://doi.org/10.19805/j.cnki.jcspe.2020.04.007
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    Numerical simulation was conducted to investigate the influence of the following factors on the friction coefficient along the flow patch, such as the Reynolds number, pipe diameter, baffle number and spacing, etc., so as to analyze the change rule of friction coefficient for the pipe flow with baffles, following which, an empirical correlation was proposed to predict the friction coefficient at high Reynolds numbers. Results show that when the Reynolds number is larger than 20 000, the friction coefficient of pipe flow with baffles is hardly related to the Reynolds number. The friction coefficient decreases with the rise of both the pipe diameter and the baffle spacing, which increases first and then comes to a constant with the growth of baffle number. When the pipe flow with baffles is magnified in equal proportion, the friction coefficient would change, and the values could be recalculated with the empirical correlation proposed.
  • Engineering Thermophysics
    Heat Transfer Enhancement by an Oscillating Reed in a Heated Channel Based on Fluid-Solid Coupling
    JIANG Xinyu, YANG Mo
    2020, 40(4): 317-322. https://doi.org/10.19805/j.cnki.jcspe.2020.04.008
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    Using Arbitrary Lagrangian-Eulerian (ALE) method, the flow and heat transfer in the heated channel of low Reynolds number with an inverted reed internally installed were studied, so as to simulate the reed vibration, flow field characteristics and their combined effects on the heat transfer in the channel under different bending stiffness coefficients. Results show that with the increase of bending stiffness coefficient, there are in total following four motion modes of the inverted reed found in the channel with uniform inflow: deflection mode, large-scale flapping mode, small-scale flapping mode and stable mode. Compared with typical channels, the wall temperature of the channel with oscillating reed reduces and the average Nusselt number increases significantly, under the large-scale flapping mode; the wall temperature decreases and the average Nusselt number increases slightly, under the small-scale flapping mode. Whereas, under the stable mode, the disturbance of the reed is very small on the flow field, and the wall temperature and the average Nusselt number are almost the same as the typical channels; in the deflection mode, because the reed always deviates to the lower side of the channel, the flow in the downstream is easy to be blocked, when the wall temperature increases significantly, and the average Nusselt number drops a lot. Therefore, to enhance the heat transfer in heated channels, the inverted reed should be installed in the large-scale flapping mode, but not in the deflection mode or stable mode, in actual engineering applications.
  • Engineering Thermophysics
    CPFD Simulation Study on the Effects of Partial Blockage in Air Distribution Plate on the Gas-Solid Two-phase Flow in the Fluidized Bed
    CHEN Hongwei, ZHANG Wei, LIU Tuo, LIU Yuqiang, JIA Jiandong
    2020, 40(4): 323-329. https://doi.org/10.19805/j.cnki.jcspe.2020.04.009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the method of computational particle fluid dynamics (CPFD), a three-dimensional fluidized bed with partial blockage in the distributor was simulated. By simulating the effects of partial blockage on the fluidization state and mixing characteristics in the bed, the factors affecting the high concentration region caused by partial blockage were analyzed. Simulation results show that partial blockage may lead to a high concentration area in the bed, which affects the mixing of particles, and the high concentration area tends to diffuse to the periphery. As the gas velocity increases, the diffusion degree of high concentration region decreases, which is slightly influenced by the bed height. The increase in blockage area enhances the degree of diffusion to some extent.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Numerical Simulation and Field Testing on Separation Characteristics of Dynamic Separators
    KANG Zhizhong, LI Jianrui, MENG Tao, SUN Zhe, ZHAO Hujun
    2020, 40(4): 330-336. https://doi.org/10.19805/j.cnki.jcspe.2020.04.010
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    Field sampling tests and numerical simulations were performed to study the separation characteristics of dynamic separators under different rotor speeds and milling outputs. By setting the inlet mass proportion of differently sized coal particles, and comparing the fineness of coal powder between numerical simulation and field testing, a more reliable mathematical model was obtained. Results show that at high milling output, when the rotor speed is increased, the reduction of pulverized coal fineness R90 would be slowed down; the appropriate rotor speed is about 67.5 r/min, and high rotor speed would result in rapidly increased separation power consumption, but slightly improved pulverized coal fineness. Whereas, at low milling output, when the rotor speed is increased, the reduction of pulverized coal fineness R90 would be accelerated, and the setting of higher rotor speed would result in finer pulverized coal particles, when better combustion stabilization effects are to be obtained under low load conditions.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Experimental Study on NOx Reduction by Urea Injection in Primary Combustion Zone Based on Air Staging
    BI Degui, YU Juan, ZHU Zhixiang, ZHANG Zhongxiao
    2020, 40(4): 337-341. https://doi.org/10.19805/j.cnki.jcspe.2020.04.011
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    Experimental tests were carried out on a bench-scale combution system to study the characteristic law of NOx reduction by urea injection in the primary combustion zone based on air staging, while the key influencing factors were analyzed. Results show that the stoichiometric ratio KSR1 in the primary combustion zone is one of the key factors influencing the NOx reduction; in the case of KSR1 being less than or equal to 0.85, the higher the KSR1 is, the better the NOx reduction effectiveness will be; high reduction atomphere (KSR1=0.65) is on the contrary not benefitial to the NOx reduction; the optimal KSR1 for NOx reduction is 0.85; when the KSR1 is less than or equal to 0.85, the higher the temperature is, the better the NOx reduction effectiveness will be; the maximum NOx reduction efficiency reaches 42.66% at the temperature of 1 673 K. High temperature benefits the generation of intermediate products OH and H in the combustion process, which is the necessary condition for NOx reduction with NH3 in the absence of oxygen.
    • System Engineering
  • System Engineering
    Experimental Study on Water Recovery from Flue Gas Condensation in Coal-fired Power Plants
    YANG Jianguo, XU Minglu, CHEN Yonghui, ZHAO Min, WANG Chenhui, KANG Kewei, PENG Yueyu, ZHAO Hong
    2020, 40(4): 342-348. https://doi.org/10.19805/j.cnki.jcspe.2020.04.012
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    To recover the water in flue gas of coal-fired power plants, and to investigate the condensation and recovery characteristics of vapor in the low-temperature wet flue gas, a flue gas condensation and recovery test platform was constructed for the WFGD exit of a coal-fired unit. Based on theoretical calculations, an analysis was conducted on several key factors, such as the flue gas state in the desulfurization system and the condensation process of the saturated flue gas. Moreover, field tests were carried out to study the effects of relative cooling water flow on the heat transfer characteristics, to analyze the influence of flue gas temperature drop on the recovery of condensate water, and to investigate the water collection performance of the flue gas condenser. Results show that the decline in flue gas temperature has a linearly correlation with the flue gas water recovery rate and condensate water recovery rate. For a temperature decrease of 10 K in the test system, the flue gas water recovery rate is about 35%, and the condensation water recovery rate gets close to 80%; the total heat transfer coefficient of the cooling water remains stable as the relative flow rate reaches 3. In the meantime, the heat transfer coefficient of flue gas is about 9 times that in pure convective condition; the condensate recovery rate of flue gas condenser could achieve 56%, which means that the remaining 44% of the condensation droplets need to be recovered by the separator.