Key Engineering Materials Vol. 517

Abstract: To conserve operation energy consumption and improve outflow availability, a novel low concentration photovoltaic/thermal system with constant volume refrigeration was proposed in this paper. The outdoor experiment, carried out in Nanjing, suggested that the thermal efficiency could approach to 39.4%, while the electrical efficiency could reach 14.1% with 40 outflow. Applying the implicit finite-volume method, a model of this system was also derived. Based on the measured environment data, the performance of this system was simulated and validated by the experiment data.

Abstract: In this paper, a line focus solar cooker with deflection trough concentrators and heat pipe was for Tibet area successfully developed. The designed cooker met the demands of indoor use, miniaturization and improved the power and temperature of current solar cooker. It included two key parts: array of deflection trough concentrators and heat pipe. Firstly, the structure of the solar cooker was described, especially the improvement of the structure of the heat pipe. The condensing section of the heat pipe was designed to simplify the process of heat transfer, reduce the heat loss and improve the heat efficiency. Secondly, the mirror array of the deflection trough concentrators was tested experimentally. Meanwhile, the overall performance of the solar cooker was also estimated. Simultaneously, the solar radiation flux at the focal spot was improved. With the temperature of the condensing section of the heat pipe increasing, the power of the cooker was amplified. Finally, the data of the experiment was analyzed. The result showed that under the conditions of Nanjing, the power of the solar cooker was enhanced and it could reach 1200W. The temperature tested in the experiment reached the desired temperature, which maximum value was 214, so it will work well in Tibet.

Abstract: In this paper, a concentrating photovoltaic (CPV) system with low ratio was successfully developed. In the design of CPV concentrator, a quasi-parabolic reflector was adopted. With the research of basic optical mechanisms, a mathematic model was built with the corresponding program. In addition, the width of light spot was analyzed with considering the symmetry of tracking errors and glass deformation in manufacture to identify reasonable values. The system was designed with a reflector of 10 flat mirrors, which has a geometrical concentration ratio of 8.18 and a flux concentration ratio of 5. The concentrating photovoltaic system was investigated experimentally under the various weather conditions. The output voltage profile and the output power of the flat PV system and the CPV system were presented to analyze the concentration ratio and the electric power. And the influence of soiling was also discussed. The results showed that the performance of tracking system was good in a clear day. Compared to the flat cell with the same system, the electric power was nearly increased by 4-5 times.

Abstract: The difference existed between results of silos pressure calculation and the actual case, because the influence of density stratification was not taken into consideration. The aim of this paper was to obtain silo pressure calculating formula by consider of storage materials density stratified. To this end, we assume that the density was continuous changed along the height and differential equation of the storage materials pressure was established. By compared the results calculated from the equation with the results calculated from the code, it is found that the maximum pressure increased. The results showed density stratified is an import factor for silo pressure calculation and the equation obtained in this paper can provide references for the theory of silo pressure calculation.

Abstract: The choice of structural reinforcement, such as increasing cross-section, steel-bonded, carbon fiber reinforced and etc, is affected by many factors. How to create optimal model is a major unresolved issues for designers to decide more scientific and rational structural reinforcement. The research obtains the weight of factors by Analytic Hierarchy Process and ascertains relative membership degree of factors by theory of Fuzzy Mathematics, and transforms qualitative impact of these factors into quantitative analysis, then the optimizing model is set up by The Generalized Hamming Distance as p=1 which is analyzed by an actual engineering that we can certificate the model valuable and useful. The research provides a simple and intuitive method of quantitative analysis for reinforcement by establishing optimization model, especially for both multi-objective and multi-factor decision-making, and overcome the arbitrariness when determining the reinforcement.

Abstract: Heliostat is the major part of solar tower power station whose wind resistance is deemed significant in design. The CFD model of single heliostat under typical operating situation was founded by technology of numerical simulation based on standard k-ε model. This paper puts forward a mesh generation method applied to complex projects under different working conditions. The corresponding UDF program was framed & used to simulate proper wind field entry conditions. The wind pressure distributions variation rules at different wind direction & elevation angles got summarized. The drag coefficients, the lift coefficients, and the three-dimensional moment coefficients in wind power coordinate under different operating conditions were computed. The results agree well with experimental data though a little bigger error exists locally. Moreover, the flow field distribution hard to acquire in wind tunnel test was compensated to further explain origin of heliostats wind pressure distribution. The influencing factors and the variation rules discovered reveals that prediction by numerical simulation is practically satisfactory.

Abstract: In order to improve the construction control precision of long-span hybrid girder cable-stayed bridge, the design parameters such as the weight of girder, the cable tensile force and the stiffness of cable are conducted sensitivity analysis through computing and comparing the influences of these parameters on the deflection of girders, the stress of girders and the cable force in the bridge's completion state. It was shown by the computation results that the main parameters of long-span hybrid girder cable-stayed bridge are the weight of girder and the cable tensile force, the stiffness of cable has a little influence on the completion state of the bridge. With this approach, through modifying the main parameters, while ignoring the influences of the secondary ones, the Jingyue Yangtze River Highway Bridge construction control has been successfully done. The test results show that the cable force and the contour of the bridge are in good state. They are both in the range of control, the relative error of the cable force is less than 3% and the elevation deviation is less than 5mm.

Abstract: By response spectrum method, superposition method based elastic time-history analysis and nonlinear time-history analysis of Newmark-β based linear increasing acceleration method, the finite element models of frame piers 21#~29# of the Ziya River Bridge on Tianjin to Baoding railway are established, and an assistant program code is generated to analyze seismic response of the frame pier. Results indicate that the vibration modes of frame piers are scattered. Only a few modes would be aroused in a narrow band spectrum. And the seismic response obtained by the response spectrum method is generally 10%~20% smaller than which obtained by the elastic time-history analysis. Under seismic excitations along the longitudinal direction, the ratio of displacement difference between two columns to the maximum value is generally liner increased with the increasing of the girder deviation from the centre of the pier beam. And the plastic hinge yielding would occur both at the bottom and the top of pier columns under excitations of the transversal direction. As a result, taking more than 30 vibration modes into account is suggested in a seismic response analysis or design calculation for frame piers. A time-history analysis is recommended as well. The evaluation of earthquake resistant capability of the transversal direction should consider both the bottom and top of the columns, and the anti-seismic capability design of the longitudinal direction is one of the key points for frame piers in the ductility design.

Abstract: s. In this paper, we discuss the design and calculation methods of Circular-shaped Corrugated Steel Culvert Pipe (CCSCP) used in highway construction. With many advantages such as lightweight, environment friendly, cost-effective, rapid construction, etc., Corrugated Steel Culvert Pipe (CSCP) have been widely used in highway construction acting as the alternative of RC culvert in China in recent years. It will not crack under impact loads or vibrations due to the inherent strength of steel and the flexibility of the corrugated pipe section. The high ring compression of the pipe absorbs and transfers the load to the surrounding soil around the entire circumference. In this paper CCSCP is a kind of culvert which is fabricated to a circular shape by several pieces of corrugated steel plates jointed by high strength bolts. In this paper, a serial test is conducted on site in process of the fabricating of the CCSCP used in the construction of Shanghai North Outer Ring Line Highway in China. In addition, 3D FEM analysis is performed with the intent of contrasting with the result of the test. Some design methods are proposed in this paper, and they will be useful guidelines for safe design of CCSCP.

Abstract: On the basis of vibration testing of flanged connection structure, AE signals gathered are carried on processing with MATLAB,mainly the reconstructed signals. The concepts of characteristic frequency band and the superiority frequency band are drawn, and the layers of wavelet packet decomposition are determined, and the frequency band distributed characteristics of acoustic emission (AE) are obtained. With the percentage of wavelet packet energy band, the strengths of superiority frequency band and the relationship of torque and it are gotten quantitatively and it is found that the energy has certain regularity with the torque changing, and proposed that express its rule characteristic with wavelet packet energy spectrum rate of change this target in order to achieve the identification of the connection structure condition.