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    Boiler Technology
  • Boiler Technology
    Hot-state Experiments on Coupled Reburning of Biomass Gas and Pulverized Coal for NO Reduction
    YANG Zhangning, LU Xiaofeng, NI Gang, RAN Shenming
    2020, 40(10): 781-785. https://doi.org/10.19805/j.cnki.jcspe.2020.10.001
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    Taking biomass gas as the reburning fuel, hot-state experiments on coupled reburning of biomass gas and lean/bituminous coal were carried out for NO reduction in a 50 kW down-flow furnace, during which, the effects of the following factors on the NO mass concentration conversion rate, pulverized coal burnout characteristics and outlet gas temperature were studied, such as the injection position, biomass gas blending ratio and boiler load, etc. Results show that the coupled combustion of biomass gas and pulverized coal can effectively reduce the NO concentration; the NO reduction effectiveness by coupled reburning of biomass gas and bituminous coal is better than that of biomass gas and lean coal; optimum effectiveness of NO reduction could be obtained when the biomass gas is injected in the reduction area close to the burnout zone; the decreasing amplitude of NO mass concentration conversion rate reduces when the blending ratio of biomass gas exceeds 10%; the reburning of biomass gas has little effect on the burnout rate of pulverized coal, but the outlet gas temperature would be increased by about 10 K.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Multi-parameter Optimization of a Staggered Labyrinth Seal Based on Response Surface Model and Multi-island Genetic Algorithm
    QIAN Zhaosheng, YANG Ailing, CHEN Eryun, ZHANG Wanfu, LI Guoping
    2020, 40(10): 786-792. https://doi.org/10.19805/j.cnki.jcspe.2020.10.002
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    Researches were conducted on the multi-parameter design and optimization of a staggered labyrinth seal with minimum leakage flow as the optimization goal, during which, a parameterized geometric model and a second-order response surface model were established for the seal, while the multi-island genetic algorithm was used to carry out corresponding calculation and optimization. Results show that the R2 of the second-order response surface model for the staggered labyrinth seal is 0.962 71, which can effectively reduce the amount of optimization calculation. The optimal set of structural parameters obtained by the multi-island genetic algorithm agrees well with the CFD results, with an error in leakage flow calculation being about 6.8%. Structural parameters, such as the number of sealing teeth, and the height and position of the boss, have a great impact on the leakage characteristics of the staggered labyrinth seal, and there are optimal values, which are the key geometric parameters for the design and modification of staggered labyrinth seals.
  • Steam Turbine and Gas Turbine
    Influence of Gas Turbine Stator Profile on the Adiabatic Film-cooling Effectiveness
    WEI Jingying, CHI Zhongran, ZANG Shusheng
    2020, 40(10): 793-800. https://doi.org/10.19805/j.cnki.jcspe.2020.10.003
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    Film holes with similar geometric parameters were arranged on both front-loading and aft-loading guide vanes of gas turbines by using the parametric design method. The influence of the following factors on the adiabatic film-cooling effectiveness was studied, such as the airfoil shape, the supplying pressure of cooling air and the cascade expansion ratio, etc. Results show that the film-cooling effectiveness and the blowing ratio in the leading area (lc≤0.4) on pressure side are obviously affected by the supplying pressure of cooling air. The cooling effectiveness in tail area on pressure side (lc>0.4) and on suction side is less susceptible to the supplying pressure. Increasing the supplying pressure of cooling air would induce strong passage vortices, and form a low-cooling zone on the suction side. The similarity design method is generally effective, in which the major discrepancy is related to the different performance of film holes with compound angles. The expansion ratio of cascade, which mainly affects the blowing ratio of jet, has limited influence on the cooling performance.
    • Automatic Control
  • Automatic Control
    Multi-variable Feedforward Foreseeable Predictive Control for Supercritical Thermal Power Units
    NIU Yuguang, HE Qingbo, LI Yongsheng, CHEN Yanqiao, ZHANG Wenliang, FAN Guochao
    2020, 40(10): 801-807. https://doi.org/10.19805/j.cnki.jcspe.2020.10.004
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    A multi-input multi-output mathematical model was established using neural network algorithm for the coordinated control system of a supercritical thermal power unit, based on which, the feedforward, foreseeable and predictive method were used to optimize the control of the unit, thus to form a multivariable feedforward foreseeable predictive (FFP) control system. Results show that the neural network predictive control enables the unit to track the AGC curve, the sliding pressure target value and the midpoint temperature set value more quickly and accurately, whereas the feedforward control aggravates the fluctuation of the main steam pressure and the intermediate point temperature, while the foreseeable control has the effect of making these two indicators tend to be stable. Therefore, using the feedforward foreseeable predictive (FFP) algorithm to control the supercritical thermal power unit could improve the AGC response speed, the economy, the stability and the safety of the unit.
  • Automatic Control
    Optimized Control for Desulphurization of Coal-fired Units Based on PFC Prediction
    FAN Haopeng, XIA Fengyi, BAO Junyu, YANG Jiachen
    2020, 40(10): 808-814. https://doi.org/10.19805/j.cnki.jcspe.2020.10.005
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    A multi-input dual-output model applicable to the limestone-gypsum wet desulfurization system of a power plant was obtained by identifying the following parameters based on particle swarm optimization (PSO) algorithm, such as the slurry pH value, the slurry flow rate and the load of the desulfurization system, etc. Then, a predictive fuzzy proportional-integral-differential (PFPID) controller was designed for the desulfurization system using feedforward-feedback composite control to eliminate the influence of interference variables, combined with predictive functional control (PFC) and fuzzy state feedback control. Results show that the method proposed can help to maintain the pH value of slurry at about 5.6, and keep the outlet SO2 concentration to be lower than 30 mg/m3, which may serve as a reference for the improvement of desulfurization control methods.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Phase Change Heat Transfer Process in a Square Bottom-heated Cavity and the Nonlinearity
    CHEN Gang, YANG Mo, ZHANG Zheng, HU Zhuohuan
    2020, 40(10): 815-819. https://doi.org/10.19805/j.cnki.jcspe.2020.10.006
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    Phase change heat transfer process of the paraffin heated and melted in a square cavity was calculated by Fluent software and enthalpy method, so as to study the variation law of temperature field and velocity field in the square cavity, and to comparatively analyze the phase change heat transfer at different numbers of Ra in the case of natural convection of liquid phase. Results show that the phase change heat transfer is mainly in the form of heat conduction at first, and then it turns to the form of natural convection, with the rise of liquid fraction of paraffin; as the number of Ste rises, the melting speed of paraffin increases. When the number of Ra is relatively small, the velocity field keeps stable in the phase change heat transfer process, and with the rise of Ra, the velocity field starts to oscillate periodically, and when the Ra is relatively large, the velocity field oscillates chaotically, indicating complex nonlinear characteristics of the phase change heat transfer process.
  • Engineering Thermophysics
    Experimental Study on Heat Transfer and Fluid Flow Characteristics of a DN Storage Element
    GAO Jianqiang, ZHANG Qiaobo, WEI Riguang, SONG Tongtong, CAO Hao
    2020, 40(10): 820-824. https://doi.org/10.19805/j.cnki.jcspe.2020.10.007
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    To solve the problems of ash accumulation and low temperature corrosion existing in a rotary air preheater caused by SCR technology, the DN (double notched) type of heat storage element was studied and compared with the DU heat storage element through experiments, during which, their heat transfer and fluid flow characteristics were obtained, while corresponding empirical correlations were fitted for the two heat storage elements. In addition, a study was conducted on the change of heat transfer and fluid flow of the air preheater before and after enamel processing of the DN heat storage element. Results show that compared with the DU heat storage element, the heat release coefficient of DN element is 32% higher, and the Darcy resistance coefficient is 17% lower. After enamel processing, the heat release coefficient of DN element is reduced by 9%, while the Darcy resistance coefficient is reduced by 36%.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Influence Factors and Evaluation Method on the Uniformity of Flow Field in a WFGD Tower
    RAN Jingyu, DENG Qingbo, NIU Juntian, YANG Zhongqing, PU Ge, ZHANG Li
    2020, 40(10): 825-831. https://doi.org/10.19805/j.cnki.jcspe.2020.10.008
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    Considering the crucial effect of flue gas velocity distribution on the gas-liquid mixing in a wet desulfurization tower, the flow field uniformity in the tower was calculated by using the velocity uniformity index (λ) based on area weighted and mass weighted average velocity as well as the relative velocity standard deviation (CV) to determine the evaluation indexes and to study the influence of inlet flue gas velocity and liquid-gas ratio on the uniformity of the flue gas in the tower. Results show that the two evaluation indexes can well reflect the uniformity of the flow field, and the velocity uniformity index is finally selected as the evaluation index based on comprehensive consideration. In addition, the λ is negatively correlated with the inlet flue gas velocity and positively correlated with the liquid-gas ratio. When the liquid-gas ratio achieves 12.08 L/m3, the λ hardly increases. The lower the inlet flue gas velocity is, the more efficient the slurry integration effect will be. The higher the inlet flue gas velocity is, the larger the amount of slurry will be required for the flue gas to be effectively integrated. Therefore, to reduce the liquid-gas ratio and energy consumption of the system, the inlet flue gas velocity should be controlled in a lower range.
  • Environmental Protection Technology and Equipment
    Energy Saving Analysis of Wide Load Denitration Technology with No.0 HP Heater
    JIANG Xiaofeng, TAO Youhong, TAO Li, ZHU Xiaolei, CAO Jianwen
    2020, 40(10): 832-837. https://doi.org/10.19805/j.cnki.jcspe.2020.10.009
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    Taking the 660 MW ultra supercritical unit as an example, a wide load denitration technology with No.0 high pressure (HP) heater was proposed, to which, an economic analysis was carried out by thermal calculation of the boiler and steam turbine. The wide load denitration technology aims to improve the feed water temperature by adding a No.0 HP heater in front of the No.1 HP heater, thus to achieve simultaneous low load denitration and low coal consumption of the unit. Results show that at high loads, the throttling loss caused by extraction steam pressure regulation of No.0 HP heater is very high, resulting in poor economy of the unit; whereas at low loads, the heat rate of the turbine is obviously reduced, resulting in high economy of the unit.
    • New Energy
  • New Energy
    Influence Mechanism of Discrete Trailing-edge Flap Gap on Aerodynamic Performance of the Airfoil and its Modification
    HAO Wenxing, LI Chun
    2020, 40(10): 838-844. https://doi.org/10.19805/j.cnki.jcspe.2020.10.010
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    To study the effects of discrete trailing-edge flap gaps on aerodynamic performance of the airfoil and on the control ability of the flap, the gaps in different shapes were researched based on macroscopic mechanics and microscopic flow field structure of the airfoil using computational fluid dynamics (CFD) combined with two turbulence models. The profile of the gap was then modified by comparing the aerodynamic performance and flow field structure of the non-contoured gap and contoured gap, and subsequently the aerodynamic performance of the modified flap was further analyzed. Results show that the loss of lift coefficient in attached flow caused by non-contoured gap is greater than the contoured gap, but in separated flow, the non-contoured gap has stronger capability in stall delay. The improved flap can well fit the fluid flow state; compared with the non-contoured gap, the lift loss of contoured flap in attached flow is smaller. As for the control ability of the flap, the unimproved gap weakens the control ability of the flap, but does not affect the control ability when the flap deflects in the positive direction.
  • New Energy
    Research on Coupling Relationship Between Wheel Vibration and Noise in a Horizontal Axis Wind Turbine
    DAI Yuanjun, HE Kai, ZHAI Mingcheng
    2020, 40(10): 845-851. https://doi.org/10.19805/j.cnki.jcspe.2020.10.011
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    To find the correlation between wheel vibration and noise in a small three-blade horizontal-axis wind turbine, a modal experiment was conducted on the wheel, while an experiment was carried out on the coupling characteristics between the wheel vibration and noise in a direct-current wind tunnel. Results show that the natural frequency of the wheel can not be taken as the vibration frequency. In the case that the centrifugal force of wind turbine wheel is fixed and the aerodynamic load is increased regularly, all the disc effect, the first and second order vibration frequency, the maximum sound pressure level corresponding to the fundamental rotating frequency and the sound pressure level corresponding to the blade tip vortex shedding frequency would keep unchanged basically; whereas in the case that the aerodynamic load is fixed and the centrifugal force is increased regularly, all the disc effect, the first and second order vibration frequency, the maximum sound pressure level corresponding to the fundamental rotating frequency and the sound pressure level corresponding to the blade tip vortex shedding frequency would increase accordingly, indicating that the vibration frequency of a small horizontal-axis wind turbine is positively correlated to the sound pressure level.
    • System Engineering
  • System Engineering
    Analysis on the Development Trend and Features of Smart Energy Sources
    CHEN Yiming, LI Zhi
    2020, 40(10): 852-858. https://doi.org/10.19805/j.cnki.jcspe.2020.10.012
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    An introduction is presented to the connotation, basic structure and framework construction of smart energy systems, with focus on the 5 development trends, such as in the guarantee of national energy security, in the establishment of business integration platform, in deep application of artifical intelligence, in the integration of industrial/ecological technologies and in the development of independent controllable technologies, together with the following 4 development features, such as the long-term coexistence of various operation modes, the great-leap-forward development of traditional energy industry driven by information technology, the remodeling of business modes and the formation of an energy community. This may serve as a reference for high-quality efficient development and application of digital, intelligent and clean energy systems.
  • System Engineering
    Design and Performance Analysis of an Improved Biomass Gasifier Heat and Power Cogeneration System
    WEI Haohan, WEN Zhiwei, SU Shiliang, LI Jizhou
    2020, 40(10): 859-864. https://doi.org/10.19805/j.cnki.jcspe.2020.10.013
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    A heat and power cogeneration system was established based on a Stirling engine in combination with a modified biomass gasifier, where a combustion tube was installed in the pyrolysis zone of the upper suction fixed bed gasifier. The high-temperature gas generated in the combustion tube was used to heat the Stirling engine, and then the mechanical energy was converted into the electrical energy through a shaft generator. Results show that the direct burning of synthetic gas and tar in the built-in combustion tube in the gasifier without decoking procedure could greatly simplify the structure of the combustion system, increase the combustion intensity, and continuously produce high-temperature gas in the thermal cracking zone. The low contents of CO, NOx, sulfide and excess oxygen in the flue gas prove the system to be environmentally friendly. By adjusting the equivalence ratio of biomass gasification, the rated power output of the Stirling engine could be stabilized at 35 kW, with maximum power output of 44 kW, and an exergy efficiency of 61%, proving the cogeneration system to be effective.