Advanced Materials Research Vols. 291-294

Abstract: A general model of the optimum design of structural vibration with the random parameters is introduced. Dynamic optimization design of stochastic finite element using the Preconditioned Conjugate Gradient method (PCG) is presented. The vibration equation of a system is transformed to a static problem by using the Willson method and stochastic finite element analysis of structural vibration adopts the PCG.An example is given respectively and the proposed method is robust and efficient.

Abstract: This paper addresses the quantification of environmental variability of wavelet packet energy spectrum (WPES) extracted from the ambient dynamic responses of a suspension bridge using wavelet packet transform (WPT). The daily averaged WPES using multi-sample averaging technique are first obtained to eliminate the inherent randomness arising from the identification algorithm. Then the effect of temperature on the measured WPES is quantified using the seasonal correlation models. The traffic-induced and wind-induced variability are further quantitatively evaluated by establishing the traffic-WPES and wind-WPES correlation models. The analysis results reveal that temperature and inherent randomness are the critical sources causing WPES variability, and the WPES variability caused by wind speed and traffic loadings is negligible compared with temperature and inherent randomness. Considering seasonal correlation models of temperature-WPES can effectively eliminate the temperature effect and inherent randomness, it is suitable for structural damage warning of long-span bridges if future seasonal correlation models deviate from these normal models.

Abstract: Absorber is a key component of absorption refrigeration system, in which there is a complicated heat and mass transfer. To improve the performance of absorber, the magnetic field was used as a enhancing way, the experiments of NH₃/H₂O bubble absorption in magnetic field were carried out. The results showed that the NH₃/H₂O bubble absorption can be strengthened by the magnetic field. Both AR(absorption rate) and EAR(effective absorption ratio) increase with the increase of magnetic intensity within the range of 0~280mT. The EAR is always higher than 1 when the external magnetic field exists. The EAR reaches the maximum 1.069 when the initial ammonia concentration is 20wt% and the magnetic intensity is 280mT. The primary strengthening mechanisms are also explained.

Abstract: An efficient method utilizing the concept of inverse heat conduction is presented for the thermal analysis of pistons based on application to the piston head of a marine diesel engine. An inverse heat conduction problem is established in the form of an optimization problem. In the optimization problem, the convection heat transfer coefficient（HTC）on the top side of the piston is defined as the design variable, while the error between the measured and analysed temperatures is defined as objective function. For the optimization, an axi-symmetrical finite element conduction model is presented. The optimum distribution of the HTC at the top side of piston is successfully determined through a numerical implementation. The temperature obtained via an analysis using the optimum HTC is compared with the measured temperature, and reasonable agreement is obtained. The present method can be effectively utilized to analyze the temperature distribution of engine pistons.

Abstract: The paper sets up an upwind local differential quadrature-Lagrange interpolation (DQ-Lagrange) method for solving the flow field in the interlocking labyrinth seal. The implementation of the Dirichlet boundary condition and the Neumann boundary condition is improved. The paper analyzes the influence of support domain size, the implementation of boundary condition and the upwind scheme on the accuracy of the calculation. Numerical simulation result shows that the high order Lagrange interpolation may cause numerical oscillation and the local differential quadrature method is recommended. The upwind support domain can improve the accuracy of the calculation. Solution accuracy may be better in case of that the velocity support domain is larger than the pressure support domain.

Abstract: A new kind of alloy (conductor for electric and magnetic), is proposed in this paper, which applied in induction motor rotor bars, and a kind of induction motor with compound cage rotor(IMCCR) is obtained. By using the electromagnetic-thermal coupling analysis method, the transient temperature field of an IMCCR is numerically analyzed, and the transient thermal process of motor operating with blocked rotor for 10s and then stopped for 10min natural cooling is calculated. The heat diffusion of stator equivalent windings and the double-directions heat transmission processes in stator are analyzed. Based on which, the influences of rotor material permeability and conductivity on motor performance are studied. Comparing with the normal nonmagnetic material, the alloy could improve motor performance significantly while ensure motor thermal performance, which indicates the wide application of such alloy in electrical machines.

Abstract: Keeping appropriate temperature of battery pack is crucial for EV/HEV’s safe operation and optimal performance. Existing literatures mainly concerned theoretical analysis on comparison of different cooling/heating methods and distribution of temperature field in a battery pack. This paper reviewes recent research about design, test and optimization of thermal management system, and presents a prediction of development. Further research should focus on coefficient-of-performance (COP) analysis, closed-cycle control of heating/cooling power, optimizing the theoretical designs and testing more battery packs.

Abstract: Boiler heat tube failure is a long-term technical problem plaguing the production of electricity. The research on how to prevent failure of boiler heat tubes has practical significance. In this paper, select the type of the Tangshan Dong fang power plant SG-490/13.8-M572 CFB boiler as the research object, part by pressure, failure type, and run-time statistics on the heat tubes failure of two boilers throught the collation and analysis on records, the basic rules of the failure are found out, statistics show that the water wall and super heater tubes explosion causes boiler shutdown time accounted for unplanned boiler shutdown time about 82%, small power generating capacity of about 11% of the total time. Finally, relevant technical strategies including improving maintenance quality and strengthening boilers regular inspection are proposed, the unplanned outage of units is radically reduced, and the safety and reliability of boiler operation is comprehensively improved.

Abstract: According to the vacuum bursting process for fresh chestnut shell and requirements for relevant vacuum system, a vacuum system of steam jet pump was designed with a start-up jet pump attached to it. Of which the waste gas from ejector was used for reheating in the bursting process to lead the vacuum bursting unit to run more reliably and stably with efficiency improved and energy consumption reduced. The rate of bursting came up to 95% in the process test.

Abstract: Isothermal chamber, which is fabricated by empty chamber stuffed with thin metal wires, is a kind of test devices for flow rate characteristics of pneumatic components, and its temperature characteristics are critical to the accuracy of test results. In this paper, the stuffers in isothermal chamber were considered as porous medium with large porosity, so the temperature characteristics could be studied by numerical simulation. Though there are differences between simulation and experiment, they have same trends and the law of variation can be seen from the simulation results, which demonstrates the reliability of numerical simulation. Consequently, simulation can be an efficient method, which is energy-saving and cost-reducing.