Advanced Materials Research Vols. 317-319

Abstract: High efficiency /high power density is one of the hottest research spots in power electronics technique. Due to simple structure and high conversion efficiency, the LLC resonant DC-DC converter has great utilization potential in many application areas. To improve the conversion efficiency and the power density further, synchronous rectifier is widely adopted at the secondary-side. Based on the existed synchronous rectified LLC resonant DC-DC converter reviewed in this paper, advantages and disadvantages are analyzed and compared in detail. A novel primary-side current sensing strategy and a new current driving method for voltage-doubler rectifier are presented. Finally, this paper proposes a family of novel single package structure for synchronous rectifier from the view point of power electronics integration to improve the performance further.

Abstract: This article focuses on the topic of material real running mode in order to put forward the theoretical reference for the structure optimization and equipment commissioning. The authors analyzed the operational regularity of loose material in horizontal circling vibrating dryer, and then established the mathematical model of the material running law and time in the single layer plate. The thesis simulated the material operational time to any position by programming, and represented that the simulation result had the good agreement with the measured data. The conclusions of this thesis have great significance for the practical structure design of this series of equipment, which can reduce the commissioning time and optimize the structure to a large extent.

Abstract: According to the studying on the force analysis of floating ring of centrifugal pump, the paper think that floating ring stress will change with the change of centrifugal pump’ s condition. Using fluent software, the floating ring seal was simulated and analyzed. Results show that the liquid force acted on the floating ring is nonuniform and asymmetrical as wedging effect, and that section maximum pressure is not lies in the smallest clearance place, but in the wedge area where liquid flows to the minimum clearance, because the effect of Leak resistance is better in high pressure than low pressure. The leakage decreases and liquid resistance increases with the increases of RPM. The leakage increases with the increases of differential pressure in sealing ring sides and eccentricity. Pressure distribution within the seal clearance is not uniform with the increases of eccentricity.

Abstract: Digital Lensless Fourier Holography setup for recording and reconstructing object is presented. By using optical fiber of high numerical aperture, almost-perfect spherical reference wave can be acquired. Pre-imaging method is used to enlarge the view-field of object. Speckle noise as multiplicative noise in digital holography can be transformed to additive noise through homomorphic transform. Median filtering algorithm is successfully used to reduce speckle noise.

Abstract: The full flow field model of a widely used multi-blade centrifugal fan was built, and unstructured grids were used to discrete the computational domain. The moving reference frame is adopted to transfer data between the interfaces of the rotating field and the stationary field. Pressure boundary conditions are specified to the inlet and the outlet. The SIMPLE algorithm in conjunction with the RNG k-ε turbulent model was used to solve the three-dimensional Navier-Stokes equations. The steady and unsteady numerical simulations of the inner flow in the fan at different working conditions were presented using the CFD method. The numerical simulation results were validated by contrasting to the experiment results. The results displayed the characteristics of the velocity field, pressure field, pressure fluctuation at two monitoring points in the centrifugal fan. The results can provide basis for optimizing the fan design and the internal flow, and have important value of engineering applications in the increase of the overall performance in operation.

Abstract: This paper demonstrates three-dimensional modeling method of virtual reality, and presents a 3D interactive virtual scene design based on the Unity 3D technology, combined with AutoCAD, MultiGen Creator and Unity 3D software platform. In this process, the scene and different format file has been optimized, the network interactive viewing of virtual scene is realized too. It focuses on an example designed to obtain a better real-time, interactive and good visual effects.

Abstract: In order to efficiently search for new soliton solutions to differential-difference equations (DDEs), three kinds of triangle rational functions are first introduced. Then a kind of formal solutions of DDEs are presented which are expressed by a unified nonlinear combination of the three kinds of triangle rational functions. As illustrative examples, the periodic travelling-wave solutions of the discrete modified KdV(mKdV) equations are obtained.

Abstract: Many researchers explore the issue about how to predict equipment failures and how to analyze the cause of the failures and to solve them. The mass imbalance is the most common cause of the malfunction of the rotating machinery. Based on the theory of rotor dynamics, we can diagnose the failure and its causes more accurately by applying the software to doing simulation analysis of characteristics of rotor dynamic. And, it provides the reliable basis for the further solutions of the failures. In this paper, we analyze a corporation's compressor with abnormal vibration in operation, and finding out the reasons for its vibration. According to the calculated results, we transformed the local structures of its rotor. After transformation, the compressor runs smoothly.

Abstract: The original control system adopts MEH controller and maintains the operation of the unit by continually backflow. But surge problem still exists in the running, which constitutes a serious threat to the safety of the unit, meanwhile wastes a lot of energy. Later S5 Duplex control system of CCC Company is adopted in the reconstructed control system, which rebuilds the compression anti-surge control system, eliminates surge threat and huge energy consumption. Millions of profits can be created by this renovation each year. The targets of stable operation and energy conservation can be achieved as well.

Abstract: Aiming at the contradiction between rapid response, stability and accuracy in position control of pump-control electro-hydraulic servo system, a multi-mode extension control electro-hydraulic servo system was proposed, applying extension method in system design. According to the characteristic information of the system, correlation function was established by multi-mode extension control switch. The movement process was divided into three parts according to correlative degree and controlled in each zone by Bang -Bang controller, fuzzy controller and PID controller respectively. Simulation results showed that the system had rapid response and strong robustness, and can realize high precision control.