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    Boiler Technology
  • Boiler Technology
    Influence of Low-load Flue Gas Recirculation on Combustion and NOx Emission in Pulverized Coal Boiler
    LIU Kunpeng, WEI Bo, CHEN Lijuan, WANG Jianjiang, LI Jian, LIU Jiangshan
    2021, 41(5): 345-349. https://doi.org/10.19805/j.cnkij.cspe.2021.05.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the structural parameters and low-load operation parameters of a 330 MW boiler, effects of different flue gas circulation rates on average temperature, O2 volume fraction, CO volume fraction and NOx emission mass concentration in the furnace at low load were analyzed. Results show that NOx emission mass concentration can be effectively reduced by flue gas recirculation with primary air at low load. With the increase of flue gas recirculation rate, average furnace temperature,CO volume fraction and NOx emission mass concentration gradually decrease. Compared with no flue gas circulation, at the flue gas circulation rate of 15%, NOx emission mass concentration is reduced by 67.88 mg/m3 and NOx emission reduction efficiency is increased by 20.36%, respectively.
  • Boiler Technology
    Effect of Heating Rate and Pressure on the Transformations of Nitrogen- and Sulfur-containing Functional Groups on Pyrolytic Char Surface
    ZHANG Yanchao, LEI Ming
    2021, 41(5): 350-357. https://doi.org/10.19805/j.cnkij.cspe.2021.05.002
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    The characterization of nitrogen- and sulfur-containing functional groups on pyrolytic char surface at different heating rates and pressures was studied by X-ray photoelectron spectroscopy (XPS) analysis in the drop tube furnace and the tube furnace. Results show that the heating rate and the pressure obviously affect the transformations of nitrogen- and sulfur-containing functional groups on the char surface. Compared with the slow pyrolysis, the rapid pyrolysis with high heating rate restrains the decomposition of pyridine (N-6), but the decomposition and transformation of quaternary nitrogen (N-Q) is promoted. For the sulfur-containing functional groups, the rapid pyrolysis reduces the stability of pyrite and sulfide. However, the decomposition of sulfoxide and sulfate was inhibited. With the increasing of pyrolysis pressure, nitrogen in the interior-molecular structure bound to the aromatic structures, but the transformation of pyrrole (N-5) to N-6 is inhibited. Finally, both N-5 and N-6 transform to N-Q in the interior-molecular structure, and the stability of nitrogen oxide (N-X) is improved. For the organic sulfur, the increase of pressure enhances the decomposition of sulfide and sulfoxide, and improves the stability of sulphone and thiophene, but has an insignificant influence on the occurrence of inorganic sulfur.
  • Boiler Technology
    Co-gasification Characteristics of Sludge and Zhundong Coal in CO2 Atmosphere
    ZHANG Zhiyuan, JU Rui, ZHOU Hengtao, YU Tingting, CHEN Hongwei
    2021, 41(5): 358-367. https://doi.org/10.19805/j.cnkij.cspe.2021.05.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to explore the co-gasification characteristics of sludge and Zhundong coal in CO2 atmosphere, the characteristics of gasification products and co-gasification reaction kinetics were studied by thermogravimetric analyzer in an electric heating fixed bed.The activation energy of co-gasification was calculated by Model-free Method. Results show that the volume fraction of CO, H2 and CH4 in isothermal gasification process increases at first and then decreases with the reaction. With the increase of Zhundong coal content, the volume fraction of CO in combustible gas increases gradually, the volume fraction of H2 and CH4 decreases gradually, and the cold gas efficiency increases at first and then decreases. In the dry desorption stage and slow gasification stage of temperature programmed gasification, the total weight loss of samples gradually decreases with the increase of Zhundong coal content. However, in the rapid gasification stage, the total weight loss of samples decreases with the increase of Zhundong coal content. The average activation energy of co-gasification decreased first and then increased with the increase of Zhundong coal content. The mixing of sludge and Zhundong coal has a positive synergistic effect on the gasification reaction. When the mass ratio of sludge to Zhundong coal is 4∶6, the synergistic effect of co-gasification is the strongest.
  • Boiler Technology
    Study on Wireless Transmission Characteristics of Heating Surface Temperature Monitoring Signals in a Power Plant Boiler
    HOU Zhefan, WANG Xinyu, LI Hongyuan, XU Hong
    2021, 41(5): 368-373. https://doi.org/10.19805/j.cnkij.cspe.2021.05.004
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    The finite element model of temperature characteristic signal wireless transmission on the heating surface of a power plant boiler was established with surface acoustic wave (SAW) temperature measurement as the principle. The model was verified by experiment and different wireless transmission characteristics of temperature signal under three antenna structures, namely dipole antenna, normal spiral antenna and planar inverted F antenna (PIFA), were compared. Results show that the finite element model can effectively reflect the wireless transmission characteristics of surface acoustic wave temperature characteristic signal; the wireless transmission gain of temperature characteristic signal from dipole antenna and normal spiral antenna is circumferential symmetrical distribution, while the wireless transmission gain of temperature characteristic signal from PIFA antenna has obvious directionality; the temperature characteristic signal from dipole antenna has the largest wireless transmission gain and the largest wireless transmission bandwidth, which is about 40 MHz. While the wireless transmission bandwidth of normal spiral antenna is the smallest, which is only 3 MHz.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Effects of Rim Seal Purge Flow on Film Cooling Characteristics of Downstream Rotor Endwall
    GAO Qing, QU Jie, WANG Ting, MA Tingshan, JU Wenping, LI Jun
    2021, 41(5): 374-379. https://doi.org/10.19805/j.cnkij.cspe.2021.05.005
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    The film cooling characteristics of the rotor endwall under the interaction of the rim seal purge flow and the main flow were studied. By solving the three-dimensional RANS equations and SST Turbulence model, the effects of aerodynamic parameters such as coolant mass flow ratio (MR) and purge flow swirl ratio on film cooling characteristics of rotor endwall were analyzed in detail. Results show that increasing MR is beneficial to improve the film cooling efficiency at the endwall region in the leading edge of the rotor blade, but even under the condition of large MR, the middle-rear part of rotor hub platform still can not get enough film protection. By adjusting the purge flow swirl ratio to make the cooling airflow enter the rotor blade passage at the designed angle of attack, the optimal film cooling characteristics of rotor endwall can be obtained.
  • Steam Turbine and Gas Turbine
    Numerical Study on Suppression of the Secondary Flow by Endwall Jet in Leading Edge
    ZHAO Shu, CHEN Liu, DAI Ren
    2021, 41(5): 380-386. https://doi.org/10.19805/j.cnkij.cspe.2021.05.006
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    Based on the active flow control method of jet flow,jet holes were set at the leading edge of turbine cascade endwall.Effects of jet hole position,skew angle,pitch angle and momentum coefficient on leading edge horseshoe vortex and flow loss were analyzed by numerical simulation.Results show that as the jet holes are arranged on the separation line of leading edge horseshoe vortex flow and the skew angle direction is consistent with the limit streamline of the proximal endwall where the jet holes are located,the ratio of total pressure loss coefficient reaches the minimum in the case of pitch angle β=40° and momentum coefficient Cμ=0.1%, which is regarded as the optimal combination scheme.The scheme can suppress the multi-vortex structure of the leading horseshoe vortex,weaken the strength of turbulent kinetic energy and reduce the flow loss. Finally, the total pressure loss coefficient near the outlet can be reduced by 8.83%.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Fault Analysis of Rotor Oil Film Instability Based on Synchrosqueezed Wave Packet Transform
    TANG Guiji, XU Zhenli
    2021, 41(5): 387-393. https://doi.org/10.19805/j.cnkij.cspe.2021.05.007
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    Aiming at the shortcomings of the existing time-frequency analysis methods in rotor non-stationary feature extraction, synchrosqueezed wave packet transform(SSWPT) was introduced to analyse the fault of rotor oil film instability. Firstly, the signal of vibration was transformed into wavelet packet transform coefficients and then the instantaneous frequency of signal was obtained. Finally, the coefficients of wavelet packet transform were compressed along the instantaneous frequency direction so that the frequency components were clearly presented in time-frequency diagram. Simulated signals, experimental signals and field fault data of oil film whirl were used to verify the method, which was compared with Hilbert-Huang transform (HHT). Results show that the proposed method can successfully extract the characteristic frequency of rotor oil film instability fault, reflecting its superiority in rotor oil film instability fault diagnosis.
  • Monitoring and Measurement
    Research on Gas Turbine Compressor Fault Early Warning Based on LSTM-SVM
    PENG Daogang, JI Chuansheng, TU Xuan, WANG Danhao
    2021, 41(5): 394-399. https://doi.org/10.19805/j.cnkij.cspe.2021.05.008
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    In order to detect the four common faults of compressor blade fouling, wear and corrosion, air intake icing and surge at an early stage, a new method of gas turbine compressor failure early warning based on long short term memory (LSTM) and support vector machine (SVM) was proposed. Firstly, the normal historical data of compressor characteristic parameters were utilized to establish multiple single-input single-output predictive models, and the operation data of compressor characteristic parameters were substituted into the corresponding predictive models to output residual curves between the predicted and actual values of each parameter, and the early warning thresholds were set for over-limit alarm. Then, the positive and negative deviation method was used to extract the fault samples of the alarm information at the alarm point, which was the input parameters of the SVM for fault identification and early warning of the compressor fault type. Results show that the prediction error of the prediction model output is within 0.5%. The method can find the early failure trend of the compressor, extract the fault characteristics and early warning of the different compressor failure type, which provides a reference for the early fault warning of the gas turbine compressor.
  • Monitoring and Measurement
    Influence of Shaft Alignment Deviation on Vibration of Single-support Shafting
    LIU Weixun, YANG Jiangang, SHEN Deming
    2021, 41(5): 400-403. https://doi.org/10.19805/j.cnkij.cspe.2021.05.009
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    The finite element model of single-support shafting was established to study the influence of shaft alignment deviation on the vibration of single-support shafting. Results show that the shaft alignment deviation would change the load of intermediate bearing and the rigidity of oil film, and then affect the vibration transmission characteristics. The vibration of single-support shafting is not completely reflected in the span of the unbalanced rotor. In the case of shafting alignment deviation, unbalance of the low-pressure rotor would stimulate large vibration on the adjacent high-pressure rotor.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Study on Adsorption of Mercury by Prepared Bio-char Under Different Heating Rates
    QIAO Xiaolei, JIA Li, GUO Jinrong, ZHANG Yongqiang, FAN Baoguo, JIN Yan
    2021, 41(5): 404-410. https://doi.org/10.19805/j.cnkij.cspe.2021.05.010
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    Walnut shell bio-chars were prepared in the tube furnace under different pyrolysis heating rates. The mercury adsorption performance of bio-char was characterized by the fixed bed reactor. The pore structure and surface functional groups were analyzed by N2 adsorption/desorption and Fourier transform infrared spectroscopy (FT-IR),and the mercury adsorption mechanism was further investigated.Results show that during the same adsorption time, with the increasing of pyrolysis temperature in fix temperature preparation and the final pyrolysis temperature in heating up preparation, the bio-char mercury adsorption performance exhibits from strong to weak at the temperature of 600 ℃, 800 ℃, 1 000 ℃ and 400 ℃. The cumulative mercury adsorption amount reaches the highest value (2 942 ng/g) within 300 min at 600 ℃ in fix temperature preparation. The mercury adsorption performance of bio-char increases first and then decreases with the increases of heating rate, and the bio-char has the best adsorption performance under the heating rate of 10 K/min. 3-5 nm mesopores play a major role in the physical mercury adsorption of bio-char. The larger cumulative pore volume is, the higher adsorption amount is, and the larger cumulative pore volume is conducive to the mercury adsorption by bio-char.At final pyrolysis temperature of 600 ℃, the number of functional groups on the surface of bio-char firstly increases and then decreases with the increase of heating rate, which coincides with the adsorption performance and indicates that functional groups on the bio-char surface can affect the mercury adsorption performance of bio-char.
    • New Energy
  • New Energy
    Research on Performance Enhancement of Farms Vertical Axis Wind Turbine Based on Gurney Flap
    NI Lulu, MIAO Weipao, LI Chun, LIU Qingsong, ZHANG Wanfu
    2021, 41(5): 411-419. https://doi.org/10.19805/j.cnkij.cspe.2021.05.011
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    In order to investigate the effect of Gurney flaps on the aerodynamic performance of vertical axis wind turbines, a numerical simulation on vertical axis wind turbines was carried out in combination with TSST turbulence model. Results show that the Gurney flap can significantly improve the aerodynamic performance of vertical axis wind turbines at low tip speed ratios, but reduce the aerodynamic efficiency at high tip speed ratios. The fluid velocity between vertical axis wind turbines increases with the increase of tip speed ratio. High-speed fluid can effectively improve wind energy utilization rate,The aerodynamic performance of downstream wind turbine at each tip speed ratio is higher than that of a single wind turbine due to the fluid acceleration between the units, and when the tip speed ratio is 2.72, the maximum average torque of the downstream wind turbine 20.3% higher than that of the original single wind turbine. The installation of Gurney flaps on the upstream wind turbines can effectively improve the fluid acceleration effect between the wind turbines and make the downstream wind turbines have higher upwind speeds. When the tip speed ratio is 2.51, the average torque of the downstream wind turbines of the Gurney flap is 36.5% and 24% higher than that of the original single wind turbine and the Gurney flap wind turbine respectively.
    • System Engineering
  • System Engineering
    Study on the Dynamic Characteristics of a Supercritical CO2 Power System During Emergency Shutdown
    LI Xinyu, LIU Huimin, LIN Zhimin
    2021, 41(5): 420-425. https://doi.org/10.19805/j.cnkij.cspe.2021.05.012
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    A dynamic model of a 300 kW supercritical CO2 simple cycle power system was established, the dynamic responses of the system during emergency shutdown and the influence of valve characteristics on process control quality were studied. Results show that the turbine bypass strategy can effectively control the speed rise of the system during emergency shutdown and ensure the safety of the system. The emergency shutdown process which can be divided into two stages lasts about 50 s. The first stage which lasts for several seconds is mainly dominated by the characteristics of bypass valve. The quick opening valve with a full action time smaller than 2 s can meet the safety control requirements of the system. The second stage which lasts for 40-50 s is monotonic decay and mainly affected by the characteristics of the system itself. In the first stage, the pressure of compressor outlet and turbine outlet increase by 1.5% and 7.3%, the inlet mass flow rate of cold side and hot side of recuperater increase by 35% and 80%, and the inlet temperature of hot side of recuperater increases about 30 K. The impact of shock effect on equipment safety should be considered in the design of supercritical CO2 power system.
  • System Engineering
    Analysis of Abnormal Fluctuation of CO2 Refractive Index near the Critical Region by Molecular Dynamics Simulation
    SUN Hui, ZHANG Lixin, YANG Qiguo, LIU Jingnan, GAO Ming
    2021, 41(5): 426-432. https://doi.org/10.19805/j.cnkij.cspe.2021.05.013
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    To reveal the abnormal fluctuation of CO2 refractive index near the critical region, the micro-structure of CO2 molecules and chaotic characteristics of time series were analyzed by molecular dynamics simulation. Results show that near the critical region, CO2 exists in a multicomponent mixed state of single molecule and clusters, and the diverse clusters are heterogeneous in density and time-dependent, which affects the search for the shortest path by light. Irregular stripes appear on the screen, which makes the acquisition of CO2 refractive index near the critical region by the characteristics of light spots and stripes become difficult. In this region, the system density fluctuates dramatically, which can directly cause strong fluctuation of linear or nonlinear refractive index in view of Lorentz-Lorenz equation. Therefore, CO2 refractive index in this region can't be obtained directly.