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    Boiler Technology
  • Boiler Technology
    Cause Analysis on Water-wall Fireside Oxidation in a Supercritical Opposed Firing Boiler
    YIN Libao, MA Lun, ZHANG Cheng, FANG Qingyan, XU Qisheng, CHEN Gang
    2015, 35(4): 257-262.
    Abstract ( )   Knowledge map   Save
    In view of the large oxidation area occurring in water wall around burners of a supercritical opposed firing boiler, the in-furnace flow, combustion and heat/mass transfer were numerically simulated based on cold aerodynamic field test, as well as macroscopic examination and composition analysis of the scale samples. Results show that the formation of oxide scales is caused by overheating over the fireside water wall adjacent to burners. The oxidation phenomenon is finally inhibited after taking following measures, such as adjusting the in-furnace combustion, reducing the output of burners near two side walls, painting anti-corrosion layer, performing regular inspection and replacing relevant tubes, etc.
  • Boiler Technology
    Influence of Overfire Air Jet Form on Low NOx Retrofit Effect of an Opposed Firing Boiler
    LI Ming, WANG Xuecai, SUN Shuweng, ZHEN Xiaowei, LI Qiang, ZHANG Tao
    2015, 35(4): 263-269.
    Abstract ( )   Knowledge map   Save
    Numerical simulation was conducted to the low NOx combustion retrofit for a 330 MW subcritical opposed firing boiler, so as to study the influence of overfire air jet form on its penetration capability through high-temperature viscous flame in the furnace, the carbon burnout rate and the NOx emission under retrofit conditions, on the premise of same overfire air ratio, constant distance from top coal burner to the nozzle and of fixed nozzle area. Results show that the circular nozzle direct flow overfire air has the strongest penetration capability, followed by the rectangular nozzle direct flow overfire air, and the overfire air in the form of outer cyclone inner direct flow has the weakest penetration capability. Highest CO emission is generated under the condition with circular nozzle direct flow overfire air due to its lowest comprehensive level of covering area of jet roots on the horizontal cross section in the furnace and its lowest air layer thickness along flue gas flow path. Lowest unburned carbon exists in the fly ash in the over-fire air jet form of outer cyclone inner direct flow because of its high-intensity turbulent mixing effect during later jet period. The overfire air in three different jet forms discussed play little role in NOx emission.
  • Boiler Technology
    Experimental Study on Burnout Characteristics of Large Coal Particles in a CFB Boiler
    LI Jinjing, ZHAO Zhenning, ZHANG Qingfeng
    2015, 35(4): 270-273.
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    Thermogravimetric analysis was conducted to large coal particles (with diameters in 9-15 mm) in a tubular furnace with the combustion rate equal to that in a CFB boiler by properly setting the temperature and air flow rate, during which the burnout time was measured. The combustion constant k and burnout exponent n, determined by the coal property of sample A and sample B, are fitted from the burnout time of large coal particles in above size range. Results show that the bed pressure drop of CFB boiler burning sample A is 600 Pa lower than that burning sample B. Sample A shows an advantage in saving electrical power consumption of primary and secondary air fans.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Structural Analysis and Optimization on Exhaust Hood of High Backpressure Industrial Steam Turbines
    ZHANG Chao, LIU Longhai, LI Xiangpeng
    2015, 35(4): 274-279.
    Abstract ( )   Knowledge map   Save
    Structural simulations were conducted for the high backpressure reactionary industrial steam turbine using finite element method, multi-physics thermosetting coupling method and nonlinear contact theory. The steady state temperature field and comprehensive stress field under criteria and ultra-criteria condition were calculated, and a comparison was made for the strength of exhaust hood and the steam tightness of horizontal flange under above two conditions. Corresponding suggestions were subsequently proposed for the structure improvement to overcome the deficiency occurring under ultra-criteria condition, such as increasing the wall thickness, changing the bolt material, size and location, and resetting the pre-tightening loads, etc. Results show that the simulation data under criteria condition agree well with that of the design criteria, which proves the calculation method to be accurate. Compared with the criteria condition, the strength safety margin of exhaust hood under ultra-criteria condition drops from 3.16 to 2.42, and the contact gap of rear shaft seal rises from 0.047 mm to 0.082 mm, both of which have exceeded the design criteria. The newly improved structure can meet all the requirements on performance indicators in actual engineering projects.
  • Steam Turbine and Gas Turbine
    Numerical Simulation on Film Cooling Effectiveness on a Flat Plate with Sister or Single-inlet Double-outlet Holes
    ZHANG Ling, GUO Ruihong, LI Hao, GUO Dafei
    2015, 35(4): 280-286.
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    By steady state calculation using Fluent segregated implicit solver, and in combination with Realizable k-ε turbulence model, numerical simulations were conducted to the film cooling effectiveness on a flat plate respectively with cylindrical, single-inlet double-outlet and sister holes at blowing ratios of 0.5, 1.0, 1.5 and 2.0, so as to study the film cooling effectiveness in main stream and lateral direction as well as to study the flow field. Results show that along the main stream direction, the cooling efficiency of sister holes is higher than that of single-inlet double-outlet hole in the near region of hole, and their difference increases with the rise of blowing ratio; but in the far region of hole, the cooling efficiency of sister holes drops a little and becomes lower than the single-inlet double-outlet hole, due to the earlier wall attachment of jet and the momentum loss caused by the mix of jet with main stream. Whereas along the lateral direction, the cooling film of sister holes is relatively uniform in the near region of hole, and the cooling effectiveness of single-inlet double-outlet hole is good at one side and poor at the other side in the far region of hole, due to the film displacement caused by jet velocity difference of the primary and secondary hole. It is concluded that the cooling effectiveness of single-inlet double-outlet hole is better in the case of lower blowing ratios, while the cooling effectiveness of sister holes becomes better in the case of higher blowing ratios.
    • Environmental Science
  • Environmental Science
    Numerical Simulation on Motion of Chain-like Particle Aggregates in Standing Wave Acoustic Field
    YANG Xufeng, FAN Fengxian
    2015, 35(4): 287-291.
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    A dynamic model was established for chain-like particle aggregates in horizontal standing wave acoustic field, with which the motion characteristics of chain-like aggregates generated by coagulation of monodisperse particles were studied using numerical simulation. Results show that the motion of chain-like particle aggregates is characterized as oscillation in wave direction and rotation at an angle within certain range; the oscillation is independent of the number of primary particles in the aggregate, but the rotation frequency increases with the number of primary particles; the motion of chain-like aggregates differs greatly from that of an equivalent sphere. The oscillation is not affected by the initial angle (θ0) between aggregate and wave direction, and the rotation range is determined by the initial angle; in an angle range of 0<θ0<π/2, the rotation will be kept in the range of [-θ0, θ0]. When the initial position of aggregate mass center moves from velocity node to velocity loop, both the oscillation amplitude and the rotation frequency will increase, which will reduce with the size of primary particles.
  • Environmental Science
    Coagulating Simulation of Particles in Flow Field of Coagulator 2D Single Turbulence Column
    LIU Hanxiao, YAO Yuping, LI Jianguo
    2015, 35(4): 292-297.
    Abstract ( )   Knowledge map   Save
    Taking the 2D single turbulence column as an object of study, the turbulent flow field was simulated using 2d-LES model by CFD software and Lagrange method, while the trajectory of particles was calculated using discrete phase model (DPM). The law of particle coagulation was subsequently obtained through further calculation by Euler's method using population balance model (PBM), via the introduction of turbulence coagulation kernel function and piecewise kernel function by the user-defined functions (UDF). Results show that the turbulence column has a good vortex effect, which makes differently sized particles be mixed effectively. The effect of turbulence coagulation is remarkable, which has a positive correlation with the turbulence intensity and energy.
  • Environmental Science
    Experimental Research on Simultaneous Decarbonization and Desulfurization by Ammonia Solution in a Packed Column
    WANG Chunbo, BAI Yanfei
    2015, 35(4): 298-305.
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    Factors influencing the simultaneous removal of CO2 and SO2 from simulated flue gas by spraying low concentration ammonia solution into a packed column were studied, such as the ammonia concentration, liquid-gas ratio, CO2 concentration, pH value, reaction temperature and SO2 concentration, etc., after which optimum working conditions were determined for the continuous cyclic operation, while the effect of experimental parameters on the aerosol emission was analyzed, with control measures proposed for the aerosol entrainment. Results show that the CO2 removal efficiency increases with rising ammonia concentration, rising liquid-gas ratio, reducing CO2 concentration and reducing SO2 concentration; with the reduction of pH value, the CO2 removal efficiency generally reduces besides the pH value of 9.6-10.2, it keeps basically unchanged; in the temperature range of 15-60 ℃, the highest CO2 removal efficiency appears at 35 ℃. Above factors slightly affect the SO2 removal efficiency, which can be kept above 99%. In the continuous cycle operation test for 260 minutes, the CO2 removal efficiency could reach more than 95% within 5 minutes, maintaining for 30 minutes; the SO2 removal efficiency could reach almost 100% within 3 minutes, always being kept more than 92%.
  • Environmental Science
    Distribution of Polycyclic Aromatic Hydrocarbons in PM2.5 and PM2.5-10 from Fly Ash of Coal-fired Power Plants
    LI Jingwei, SHI Haoxun, LI Min, WU Dongli, SHI Guozhong, LI Xiaodong
    2015, 35(4): 306-311.
    Abstract ( )   Knowledge map   Save
    Concentration of sixteen polycyclic aromatic hydrocarbons (PAHs) recommended by USEPA in PM2.5 and PM2.5-10 samples separated from fly ash with experimental facilities were analyzed using a gaseous chromatograph coupled with a mass spectrometer (GC-MS), so as to analyze the distribution characteristics of the PAHs in PM2.5 and PM2.5-10. Results show that the mean concentration of PAHs in PM2.5 is 1.86 times of that in PM2.5-10; 3-rings and 4-rings PAHs account for the main parts in PM2.5, and the concentration of 6-rings PAHs is low in both PM2.5 and PM2.5-10. The adsorption capacity of various PAHs is different in PM2.5 and PM2.5-10; PM2.5 has a stronger adsorptivity for 2-rings, 3-rings and 4-rings PAHs than PM2.5-10, but appears to be relatively weaker in adsorbing 5-rings and 6-rings PAHs.
    • Energy System Engineering
  • Energy System Engineering
    Study on Economic Load Dispatch Based on Improved CPSO Algorithm for Thermal Power Plants
    HAN Chaobing, L Xiaoming, SI Fengqi, XU Zhigao
    2015, 35(4): 312-317.
    Abstract ( )   Knowledge map   Save
    An improved chaos particle swarm optimization (ICPSO) algorithm was proposed by quadratic and chaotic inertial weight approach (QCIWA), where the crossover operation in genetic algorithm was integrated with chaos particle swarm optimization (CPSO) to increase the diversity of population. Meanwhile a new economic load dispatch model of thermal power plant was established considering the valve-point effect of steam turbine by using equal probability constraint treatment mechanism to deal with the constraint conditions, with which the economic load dispatch of 40 units was numerically calculated. Results show that compared with typical CPSO algorithm, the optimum coal cost obtained by ICPSO algorithm can be reduced by 0.78%; in comparison with other optimization algorithms, the ICPSO algorithm is proved to have better optimization effects and higher robustness.
  • Energy System Engineering
    Study on Static Load Response of Thermal Power Units Caused byCondensate Throttling Based on Steam-Water Distribution Equation
    LIU Jizhen, LIU Yuxin, WANG Wei
    2015, 35(4): 318-324.
    Abstract ( )   Knowledge map   Save
    Based on the steam-water distribution general matrix equation of thermal power systems, the relationship between variation of unit load and condensate flow was studied, and subsequently a functional relationship was established between above two variables, with which the goal can be achieved to meet the load demand by adjusting the condensate flow. Taking the 600 MW unit in Datang Panshan Power Plant as an example, the functional relationship was analyzed and verified. Results show that with the functional relationship, the load capacity can be regulated by changing a certain amount of condensate flow under fixed working conditions; whereas under different working conditions, the higher the unit load is, the better effectiveness of load adjustment will be obtained by adopting the condensate throttling method.
    • Material Science
  • Material Science
    Aging Properties of T23 Weld Joint in Water Wall of USC Boilers
    WANG Xue, LI Xiqiang, YANG Chao, GE Zhaoxiang, YANG Xianbiao, REN Yaoyao
    2015, 35(4): 325-330.
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    To analyze the effect of aging on microstructure, hardness and toughness of a T23 weld joint, aging tests were conducted to the joint at 500-650 ℃ for 0-3 000 h. Meanwhile, creep rupture behavior of the joint was also investigated at 470 ℃ and 550 ℃, so as to study the mechanism of its early failure. Results show that aging temperature has significant influence on mechanical properties of the weld metal. At the aging temperature below 550 ℃, T23 weld metal remains high hardness and has obvious brittle tendency during long term aging; whereas at the aging temperature above 600 ℃, carbides precipitate in the weld joint, contributing to the reduction in hardness and the increase in toughness. Wedge creep cracking is responsible for the early failure of weld joint. To guarantee the PWHT effectiveness and the reliability of weld joint, it is suggested that the upper limit of hardness be controlled at 250 HB for the weld metal.
  • Material Science
    Research on Coarsening Behavior of Carbides in T91 Steel During High-temperature Services
    WAN Qiang, CHEN Lin, WAN Jin, LUO Chang
    2015, 35(4): 331-335.
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    To investigate the aging behavior of T91 steel after long-term high-temperature services, the microstructure of T91 samples taken from an actual power plant was analyzed by optical microscopy (OM) and scanning electron microscopy (SEM), of which the results were compared with that of as-received T91 steel. Moreover, the growth equation of carbides in T91 steel was proposed based on the general growth equation and the data of quantitative metallography. Results show that after a long-term service of T91, the carbide particles gather and get coasening in the grain boundary, resulting in reduced quantity of carbides in grains, and accordingly weakened strengthening effect.
    • Nuclear Technology
  • Nuclear Technology
    Process Control of Nuclear Power Engineering Tests
    ZHENG Hongliang, LI Cong, GU Guoxing, HUANG Weiqing
    2015, 35(4): 336-340.
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    According to the quality assurance (QA) provisions for research and development of nuclear power projects, and based on implementation process of the test routing specified in the basic features of "special process" in QA, the main denotation of test success and related criteria are brought forward. The control elements and validation requirements for each stage of the nuclear power engineering test are defined from the aspect of both essential targets and quality assurance of the test. The availability validation of test facility is the most important link in the process control; before formal test starts, verification and validation must be taken to assure the correctness of pertinent parameters of test model, the accuracy of key parameter measurement, the controllability of test systems, the acceptability of mass/energy balance qualification and the rationality of typical working conditions, so as to guarantee enough confidence of test data. The management procedures resulted from this process control method have been completely implemented in the Research-Development Projects of Large Advanced PWR in National Science-Technology Program, which help to promote the success rate of relevant tests.