About Journal | Editorial Board |  Instruction | Subscribe | Editor office board | Contacts Us |  中文 Office 　　Online Submission 　　Manuscript Tracking 　　Peer Review 　　Editor Work 　　Office Work 　　Editor-in-chief Journal 　　Forthcoming Articles 　　Current Issue 　　Next Issue 　　Archive 　　Advanced Search 　　Read Articles 　　Download Articles 　　Email Alert 　　 Member Service Username Password Register Download 　　Instruction 　　Template 　　Copyright Agreement 　　Links 　　Journal Links   Total visitors:   Now online:   Quick Search     Advanced Search     Latest Printed Issue   2008  Vol.28 Number 35 Dec. 15, 2008 Content is this issue   工程热物理   动力机械与工程   热工自动控制   可再生能源发电         工程热物理     1 ZHANG Ju-weiSUN Shao-zengYANG Jian-chengHU Xi-dongQIN Yu-kun   Structure Development of Coal Chars Under High Temperature Reducing Conditions     The structure development of coal chars under high temperature reducing conditions was studied. The chars were produced in a high temperature entrained flow reactor (EFR) which can simulate the temperature and gas-phase environment in flame region of an industrial pulverized coal-fired furnace. Nitrogen adsorption and scanning electron microscopy were applied to characterize the char structure. The influence of gasification on the structure and morphology of the char particles can not be negligible due to the high temperature and reducing atmospheres. According to the pore structure and fractal analysis, it is concluded that the surface area, pore volume, mean diameter and fractal dimensions all have the same variation trends, and the surface area development of chars can be attributed to the formation and variation of micro-pores. Nevertheless, the char structure development is very complicated due to the existence of various competing factors. The scanning electron microscopy micrographs show that the different morphologies of char particles can be attributed to different maceral components and carbon conversion.     2008 Vol. 28 (35): 1-8 [Abstract ] ( 65 ) [HTML 0KB] [PDF 0KB ]( 5 ) 9 DUAN Lun-boZHAO Chang-suiLI Ying-jieLU Jun-yingZHOU WuCHEN Xiao-ping   Investigation on Sulfur Release From Bituminous Coal Combustion in O2/CO2 Atmosphere     The X-ray photoelectron spectroscopy (XPS) was used to study sulfur functionality in the bituminous coal and a thermogravimetric analyzer (TGA) was used to evaluate its combustion behavior in O2/N2 and O2/CO2 atmosphere by changing O2 fraction in the mixture. The Fourier Transform Infrared (FTIR) spectrometer was employed to detect the gas evolved from bituminous coal during the combustion process. Results show that in 21%O2/79%N2 or 30%O2/70%CO2 atmosphere, there are two SO2 absorbance peaks appearing; in 21%O2/79%CO2 atmosphere, a third peak appears; in higher O2 concentration (no less than 40%) atmosphere, there is only one peak left. The integrals of the SO2 absorbance unit show that total SO2 emission from coal combustion in air is less than that in O2/CO2 mixture with the same O2 fraction, and SO2 emission in O2/CO2 mixture goes up first and declines then as O2 concentration increases.     2008 Vol. 28 (35): 9-13 [Abstract ] ( 31 ) [HTML 0KB] [PDF 0KB ]( 4 ) 14 QIN HongSUN Bai-zhongWANG QingZHOU Ming-zhengLIU Hong-pengLI Shao-hua   Analysis on Influence Factors of the Characteristic of Pore Structure During Combustion of Oil Shale Semi-coke     Combustion experiments with semi-coke of Huadian and Wangqing oil shale were conducted in a bench-scale FBC reactor. Ash samples were obtained under different combustion conditions. Adsorption isotherms were determined by Micromeritics Gemini 2380 specific area analyzer under nitrogen atmosphere. The pore size distribution of samples was determined on the basis of BJH theory. Influence factors on pore structure of ash, such as different semi-coke, bed temperature, particle size, apparent fluidized velocity and batch feeding quantity of the above-mentioned semi-coke were investigated. The result shows that pore structure of semi-coke was already well developed and the total porous volume of the fuel decreased gradually during combustion. The pore size distribution of different semi-coke presents obvious difference. Low bed temperature favors the formation of porous structure. Batch feeding quantity has effect on the process of porous structure，but couldn't change the ultimate ash pore structure. Higher fluidized velocity and smaller particle size lead to more pores destroyed.     2008 Vol. 28 (35): 14-20 [Abstract ] ( 43 ) [HTML 0KB] [PDF 0KB ]( 5 ) 21 JIANG YeGAO XiangDU Xue-senMAO Jian-hongLUO Zhong-yangCEN Ke-fa   Effects of Potassium Salts on Selective Catalytic Reduction of NO With NH3 over V2O5/TiO2 Catalysts     Potassium is present in the form of potassium salts, potassium sulphate and potassium chloride, in the flue gas generated by firing the Chinese coal and biomass, respectively. The effects of potassium salts on the selective catalytic reduction of NO with NH3 over V2O5/TiO2 catalysts were studied with static nitrogen physical absorption, temperature-programmed surface reaction (TPSR), Fourier transform infrared (FT-IR) spectroscopy and activity measurements. The results show that potassium salts deactivate the V2O5/TiO2 catalysts. And the stable temperature window of NO removal gradually narrows with increasing sediment of potassium salts on the catalysts and eventually disappears when the molar ratio of K to V reaches 3.0. The potassium salts doped on the catalysts markedly reduce the number of active sites on their surfaces but not change their reactivity significantly. The main reason of the catalyst deactivation is that K preferentially coordinates to Br￠nsted acid sites on the catalysts' surfaces and neutralizes the acidity of them, as a result, the adsorbed NH3 decreases.     2008 Vol. 28 (35): 21-26 [Abstract ] ( 127 ) [HTML 0KB] [PDF 0KB ]( 4 ) 27 SHEN Bo-xiongYANG Ting-tingLIU TingWANG JingZHAO Ning   Study of Preparation and Activity of Selective Catalytic Reduction Nano-loading Catalysts     Nano-TiO2/ceramic supported V2O5-WO3 catalyst (V2O5-WO3/TiO2(C)) was prepared by sol-gel method and impregnation method. The V2O5-WO3/TiO2(C) catalyst was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was studied the influences of heat treatment temperature of TiO2 gel and WO3 loadings on reaction temperature windowand catalyst resistance to SO2 poisoning in NH3-SCR system. The effects of NH3/NO ratio, O2 concentration and gas hourly space velocity (GHSV) on the activity of the catalysts were also evaluated. The results show that V2O5-WO3/TiO2(C) catalyst has high and steady activity over the temperature range 260~420℃. The V2O5-WO3/TiO2(C) (anatase) catalyst shows high resistance to SO2 poisoning. To the contrary, The V2O5-WO3/TiO2(C) (mixture of anatase and rutile) catalyst is easily poisoned by SO2. SO2 poisoning is reversible and regeneration is feasible. The results also show that increasing of WO3 loadings can improve the activity of the catalyst.     2008 Vol. 28 (35): 27-32 [Abstract ] ( 41 ) [HTML 0KB] [PDF 0KB ]( 4 ) 33 ZHANG WeiYANG Wei-juanZHOU Jun-huL Hong-kunLIU Jian-zhongCEN Ke-fa   Experimental Study of the Effect of Sodium Salts on Selective Non-catalytic Reduction of Urea     The effect of sodium salts on selective non-catalytic reduction of urea has been investigated experimentally with a tube reactor at 800~1 150℃ and at differrent oxygen concentration in the simulated gas. The experimental results indicate that the effect of increasing normalized stoichiometric ratio (NSR) is to enhance the NO removal efficiency but to decrease the utilization efficiency of urea. Higher O2 concentration shifts the NO reduction profile towards lower temperatures and slightly lessens the maximum NO removal efficiency. Small amounts of sodium additives perform the obvious promotion effect on NO removal efficiency and widen the temperature window. And its effect becomes greater as the O2 concentration increases. The promotion effect of any kind of sodium salts is similar in our experiments when the sodium concentration in gas is same. CH3COONa is more effective at lower temperature while NaOH and Na2CO3 have a better promoting effect at the whole temperature range.     2008 Vol. 28 (35): 33-38 [Abstract ] ( 46 ) [HTML 0KB] [PDF 0KB ]( 5 ) 39 ZHANG Li-fengWANG Hua-xiang   Image Reconstruction Algorithm for Electrical Capacitance Tomography Based on Wavelet Neural Networks     Electrical capacitance tomography (ECT) technique is a complex nonlinear problem. To solve the ill-posed image reconstruction problem, a new image reconstruction algorithm based on wavelet neural networks (WNN) was proposed. The principal component analysis (PCA) method was used to reduce the dimension of the input vectors (capacitance measurements). Then, a nonlinear map between capacitance measurements and the permittivity distribution in image region was built. The transfer functions of the neurons in the wavelet neural networks were wavelet base functions which were determined by retract and translation factors. BP algorithm was used to train the WNN, and self-adaptive learning rate and momentum coefficient were also used to accelerate the learning speed. Experimental results show the image quality has been improved markedly, compared with the typical linear back projection (LBP) algorithm and Landweber iteration algorithm.     2008 Vol. 28 (35): 39-43 [Abstract ] ( 28 ) [HTML 0KB] [PDF 0KB ]( 4 ) 44 DONG Xiang-yuanGUO Shu-qingLIU Shi   On-line Calibration Method for Combustion Visualization in Porous Media by Using Electrical Capacitance Tomography     Electrical capacitance tomography (ECT) is a fast, multi dimensional measurement technique. It is non-intrusive and non-destructive and can be used for imaging combustion in porous media. It is preferable to calibrate an ECT system on-line, for it is difficult to determine the permittivity of flame under different combustion conditions. Relationship between the measured capacitances and the permittivities of the porous media was derived by an appropriate simplification. A three-point calibration method was presented. The finite element simulation results indicate that the relative errors of the new method are less than 1%. On-line experiments demonstrate the effectiveness of the new method.     2008 Vol. 28 (35): 44-48 [Abstract ] ( 30 ) [HTML 0KB] [PDF 0KB ]( 5 ) 49 ZHOU Yun-longLI Hong-weiHE Qiang-yong   Chaotic Characteristic Analysis of Oil-air-water Three-phase Flow in Vertical Upward Pipe Based on Image Gray Signals     Shooting the dynamic image of the oil-gas-water three-phase flow six typical flow type with the application of high-speed camera was in the vertical upward pipe where was 35# lubricants, air and water as the test medium. Extracting the mean gray of every frame image was to compose time series. Analyzed the chaos of the time series. Methods for the delay time, mainly with the mutual information, the self-relevant law, the average displacement and the C-C algorithm were compared, as well as power spectrum ,chaos associated & HURST index were employed. The oil-gas-water three-phase flow type forming mechanism was analyzed. The test results show that the chaos characteristic of the dynamic image gray fluctuating signals of the oil-gas-water three-phase flow in vertical upward pipe can characterize the three-phase typical flow type clearly.     2008 Vol. 28 (35): 49-56 [Abstract ] ( 22 ) [HTML 0KB] [PDF 0KB ]( 4 ) 57 FAN TaoXIE Yong-huiZHANG Di   Large-eddy Simulation for Control of Flow Separation in Conical Diffuser by Vortex Generator Jets     To investigate the mechanism of active control of flow separation in conical diffuser by vortex generator jet (VGJ) method, the flow field in a 14° conical diffuser was analyzed based on large-eddy simulation (LES) method in this study. The numerical results show good agreement with experimental data. According to the flow charts at several sections, the formation of complex vortices is illuminated, and it is approved the strong vortices near jet holes come from shear-layer vortices. After break and dissipation, shear- layer vortices develop into unsymmetrical counter-rotating vortex pair at downstream and longitudinal vortices at far downstream of jet. The longitudinal vortices are generated in the boundary layer by shear stress and friction from jets. It increases cross-stream mixing of streamwise momentum and then suppresses or eliminates separation in conical diffuser. Compared with the diffuser without VGJs at the same condition, the pressure recovery coefficient is enhanced about 19.8%. The VGJ control strategy is demonstrated to be a usable technique for separation control. The effect of the number of jets and the pitch angle of jet on recovery coefficient of diffuser were analyzed, it is shown that the appropriate choice of parameters such as the number of jets and the pitch angle of jet can effectively control the flow separation in the diffuser.     2008 Vol. 28 (35): 57-65 [Abstract ] ( 51 ) [HTML 0KB] [PDF 0KB ]( 4 ) 66 ZHANG WeiLI Guang-qiuZHANG Zheng-jiangXU Zhi-mingLI Wei   Fouling Model of Internal Helical-rib Tubes Based on Prandtle Analogy     The fouling experiments on heat transfer performance of seven copper helically ribbed tubes in cooling tower were taken under the condition of 1.07 m/s water velocity and Reynolds number is 16 000. The ranges of geometric parameters were number of rib starts (18~45), helix angle 25°~45°, and height (0.33~0.55 mm). The fouling mechanism is a combination of precipitation fouling and particulate fouling and water hardness is 800mg/L. Based on the Prandtle analogy, (Km/Kmp)/(f/fp) and (j/jp)/(f/fp)1/3 were used as evaluation indexes of heat transfer. Comparing to previous studies, this study is a comprehensive analysis involving the structure parameters of helical-rib tubes. A series of semi-theoretical fouling correlations as a function of the evaluation indexes were developed. The correlations can be directly used to assess the fouling potential of enhanced tubes in actual cooling water situations.     2008 Vol. 28 (35): 66-70 [Abstract ] ( 30 ) [HTML 0KB] [PDF 0KB ]( 4 ) 动力机械与工程     71 ZOU Jian-wenSU Zhi-gangLIN Zhong-daWANG Pei-hong   Vibration Characteristics for Reflecting Level of Coal Powder Filling in an Industrial Tubular Ball Mill     To achieve improvements in the production capacity and energy efficiency of an industrial tubular ball mill, a novel method, reflecting the level of coal powder filling in the ball mill by using vibration characteristics, was proposed. Two accelerometers were installed on bearing housing to pick up the vibration transferred from the mill shaft. A system was designed to record the vibration signals and transfer them into energy amplitudes, by using a wavelet packet approach, based on the KINGVIEW program, as well as Visual C++ environment. Based on these, a series of experiments was conducted in a 250 MW power plant to investigate the vibration characteristics corresponding to different powder filling cases, including the effects of different levels without air particle removal, milling times, and varying levels in practical working conditions. The experimental results show that the cases of powder filling in the mill, such as mill over-load, stable case, etc., can be reflected by vibration characteristics. By mean of these vibration characteristics of ball mill, the performance of ball mill can be improved.     2008 Vol. 28 (35): 71-78 [Abstract ] ( 77 ) [HTML 0KB] [PDF 0KB ]( 5 ) 79 LI Chao-shunZHOU Jian-zhongAN Xue-liXIANG Xiu-qiaoZHANG Yong-chuan   Vibration Fault Diagnosis of Generating Set Based on Weighted Fuzzy Kernel Clustering     A new weighted fuzzy kernel clustering(WFKC) method is proposed, in order to avoid the drawbacks of fuzzy C-means (FCM) in handling vibration fault diagnosis of generating set. In this method, samples in original space are mapped to high-dimension feature space by Mercer kernel, and then a similarity based weighting method is used to assign weight to features of the transferred samples, and finally weighted fuzzy clustering in feature space is realized. Experiments on three testing data sets have been designed to verify the validity and accuracy of WFKC. In the end, WFKC has been also applied in practice to analyze vibration fault diagnosis of turbine-generator set, and the result demonstrates that WFKC is valid and efficient in vibration fault diagnosis of generating set.     2008 Vol. 28 (35): 79-83 [Abstract ] ( 22 ) [HTML 0KB] [PDF 0KB ]( 4 ) 84 GAO LinDAI Yi-pingWANG Zhi-qiangXU Ya-taoMA qing-zhong   Effect of Steam Distribution Method on Large Steam Turbine Rotor Stability     Peak shaving operation of more and more large power steam turbines become necessary due to the load fluctuations. The characteristics of steam distribution system of a steam turbine under part-load conditions will affect not only the economy but also the rotor system stability of the unit. A fluid structure interaction method was used in this paper. The rotor system stability of a subcritical 600 MW steam turbine was studied under part-load conditions where unbalanced fluid force was considered. The mechanism of worsen stability of rotor system after turning to sequence valve mode was analyzed. An optimum mode of steam distribution system was proposed. The mode had been used for some practical turbine units and improved their stability of rotor systems. The research may help to improve the performance of the steam distribution system of a large power steam turbine.     2008 Vol. 28 (35): 84-89 [Abstract ] ( 26 ) [HTML 0KB] [PDF 0KB ]( 5 ) 热工自动控制     90 HAN Zhong-xuZHOU Chuan-xinLI DanZHANG WeiMA Huan-junZHANG Chuan-jiang   Soft Measurement Technology of Coal-fired Heat and Its Application on Supercritical Generating Unit Control System     Nonlinear observer is adopted to explore soft measurement technology of coal calorific value through mathematical analysis on the "generalized heat value" observer. This heat value observer has greater stability robustness and can be integrated into coordinated control system (CCS). In condition that a 660 MW supercritical generating unit with rate of 12 MW/min decreasing load from 525 MW to 245 MW in 5 times and the pressure sliding from 24.2 MPa to 12 MPa, the error of active power is within 5 MW. It has been testified that the stability robustness is strongly when the heat value observer integrated into the CCS of generating unit and it can respond to the requirement of automatic generation control (AGC) load changing in large bound quickly.     2008 Vol. 28 (35): 90-95 [Abstract ] ( 28 ) [HTML 0KB] [PDF 0KB ]( 4 ) 96 CHENG Qi-mingDOU Xu-fengGUO Run-qingZHENG Yong   Decoupling Compound Control Method Based on Least Squares Support Vector Machines Multivariable Inverse System and Its Application     To improve the dynamical property and decoupling capability for multivariable, nonlinear and strong coupling system，and to solve the problem of inverse model identification, the decoupling control method of multivariable inverse system based on least squares support vector machines(LS-SVM) was discussed. The fitting characteristic of LS-SVM function was analyzed, and the nonlinear inverse model of the controlled object was offline built with LS-SVM. The LS-SVM inverse model was cascaded before the original object, thus, the original system was decoupled into several independent single variable pseudo-linear subsystems. To overcome the modeling error of direct inverse control and improve the robust stability, the compound control system was also proposed, in which the inverse model was used as feed-forward controller, and PID controller was used to realize feedback control. The characteristics of ball mill control system were analyzed, and the ball mill control system was simulated and studied, the simulative results show that the combined method does not depend on the accurate mathematical model and has strong decoupled ability, good robust stability, high tracking accuracy.     2008 Vol. 28 (35): 96-101 [Abstract ] ( 48 ) [HTML 0KB] [PDF 0KB ]( 4 ) 102 LI Xue-bin   Study of Multi-objective Optimization and Multi-attribute Decision Making of Economic Load Dispatch Problem     The optimal load distribution system in thermal power plants is usually based on the unit coal consumption characteristics. However, these characteristic parameters are valid only on stable conditions. At the same time, the plant-level economic load dispatch problem should also satisfy the adjustment time required in automatic generation control (AGC) mode. A hybrid approach for multi-objective optimization study of plant-level load distribution was proposed. A non-dominated sorting genetic algorithm II (NSGA II) was employed to approximate the set of Pareto solution through an evolutionary optimization process. In the subsequent stage, a multi-attribute decision making (MADM) approach was adopted to rank these solutions from best to worst and to determine the best solution in a deterministic environment with a single decision maker. A example with 10-unit was conducted to illustrate the analysis process. Pareto frontiers were obtained and the ranking of Pareto solution was based on entropy weight and technique for order preference by similarity to ideal solution (TOPSIS) method.     2008 Vol. 28 (35): 102-107 [Abstract ] ( 78 ) [HTML 0KB] [PDF 0KB ]( 4 ) 可再生能源发电     108 FU PengSUN Lu-shiHU SongXIANG JunYANG TaoCHEN Qiao-qiaoZHANG Jun-ying   Evolution of Pore Structure of Maize Straw Particles During Pyrolysis     The changes in pore structure characteristics of maize straw (MS) particles during pyrolysis were studied. The samples were characterized by N2 isothermal adsorption/ desorption method and scanning electronic microscopy (SEM). The results indicate that pyrolysis temperature has a notable impact on the pore structue and morphology of biomass char. Pyrolysis temperature is found to influence the size and the shape of char particles. High temperature leads to plastic deformation of particles resulting in smooth surfaces and large cavities. Brunauer-Emmett Teller (BET) specific surface area SBET undergoes a complex process during pyrolysis: firstly decreases to 1.518 m2/g at 250 ℃, increases to a maximum value of 7.345 m2/g at 500 ℃ subsequently and then decreases to 4.684 m2/g at 900 ℃ again. The change of pore volume is similar to that of BET specific surface area below 500 ℃, however, at higher temperature pore volume increases while BET specific surface area decreases gradually. The fractal dimension DFHH calculated by fractal Frenkl-Halsey-Hill (FHH) equation could represent pore structure satisfactorily. The fractal analysis shows that pyrolysis temperature has close relation to DFHH. There are some correlations between the fractal dimension DFHH and BET specific surface area SBET.     2008 Vol. 28 (35): 108-113 [Abstract ] ( 51 ) [HTML 0KB] [PDF 0KB ]( 4 ) 114 GUO Tie-zhengLIU De-youQIAN Yan-pingCHEN QiangBIAN Xin-gaoGUO Su   Development of Heliostat Tracking Device in Solar Power Tower Plant     The control mode of open loop is generally used for heliostat tracking devices in solar power tower plants, which has the shortcomings of, e.g., low tracking accuracy, high accumulation errors etc. For that, a new type of tracking device using double-axes drive gear is introduced in this paper, including the hardware design, work principle and control strategy. The combination control mode of open and closed loop is adopted for the control system of the tracking device, using DSP (TMS320F2812) as its controller, communicates with the monitor computer which sends the solar position data and control commands. From the experimental results, the new tracking device has the advantages of reasonable design, steady operation and rapid reaction, besides, the real-time tracking accuracy can be higher than 3.5 mrad and overshoot is less than 3.2%, which make heliostat be able to realize the real-time and accurate tracking.     2008 Vol. 28 (35): 114-119 [Abstract ] ( 45 ) [HTML 0KB] [PDF 0KB ]( 5 ) 120 JIA Jun-xiABULITI   Numerical Simulation for Effect of Combustion Zone on Performance of Tubular Solid Oxide Fuel Cell     A model was developed to simulate the operation of a tubular solid oxide fuel cell with combustion zone at the steady and transient operation states. The model included all three polarizations: ohmic, activation and concentration polarization. Radiation between cell tube and air feed tube and heat transfer by convection and conduction was also included in this model. The effects of the length of the combustion zone on the performance of the steady and transient operation were analyzed in detail. Numerical results show that increasing the length of the combustion zone leads to an increasing of the overall cell tube temperature and a shorter response time for transient performance. However, enlarging the combustion zone would hardly change the terminal voltage and output power.     2008 Vol. 28 (35): 120-126 [Abstract ] ( 35 ) [HTML 0KB] [PDF 0KB ]( 5 ) Copyright © 2007 Editorial Office of  PROCEEDINGS OF CESS Support by   Beijing Magtech Co.ltd ,  E-mail: support@magtech.com.cn