Advanced Materials Research Vols. 1070-1072

Abstract: To predict accurately the stress and deformation of combustion chamber components of large slow speed two stroke marine diesel engines, based on AVL Fire and ANSYS Workbench software, multi-field coupling modeling and analysis technology was employed to carry out the strength analysis for combustion chamber components of crosshead type marine diesel engine. The boundary conditions, i.e., the temperature field distribution, the mean temperature and the mean heat transfer coefficient are obtained firstly. Then the strength analysis for cylinder liner of crosshead type marine diesel engine under the thermal loads, mechanical loads and thermal mechanical coupled loads was conducted. The results show that the strength meets the design requirement and the stress concentration and the deformation of the cylinder liner were mainly dependent on the thermal load.

Abstract: Through researching the fault vibration signal characteristics of planetary gearbox, various forms of quadratic phase coupling phenomenon were found in the signals. Bispectrum has properties such as detecting the quadratic coupling phenomena and restraining gaussian noise signal, and it can be well used in the planetary gearbox fault diagnosis. Meanwhile, the sun gear distributed fault (gear wear) and partial fault (root crack, partial broken teeth) are simulated in the wind turbine test bench built in the laboratory. By analyzing the structure characteristics of its frequency through bispectrum, the fault of the gear is effectively diagnosed.

Abstract: The lift coefficient of any wind turbine must have highest limit. In this paper, an analytical expression of lift coefficient associated with tip-speed ratio and lift-drag ratio of airfoil of wind turbine with ideal chord has been deduced by integrating along the blade wingspan using the blade element - momentum theory, which can be used for pre-estimating lift coefficient of actual wind turbine in design. Further, considering ideal fluid environment ( the drag coefficient is close to 0 ), an expression of the highest performance of lift only associated with tip-speed ratio has been deduced too, which is the highest boundary of lift coefficient of any actual wind turbine with same tip-speed ratio. The results show that for the wind turbine in steady state, there is a theoretical limit of the lift coefficient, 0.57795, which is the highest boundary that any actual wind turbine can not be crossed; if the tip-speed ratio is greater than 6 and lift-drag ratio less than 200, the lift coefficient is unlikely to exceed 0.2.

Abstract: The double PWM welding power supply which can inhibit network side current harmonics,in order to suppress the transient intermediate DC link voltage fluctuations in large, by increasing the DC capacitor capacity its weaknesses are: slow dynamic response, equipment of large volume,high cost, low life.This paper presented a welding power supply double PWM power based on feedforward control, voltage fluctuation suppression intermediate DC link power using feedforward strategy is feasible. Power system composed of this control method has the advantages of small size capacitor , high power factor, good dynamic performance,simple and feasible,and has application prospect.

Abstract: In order to increase the performance of lift-type wind turbine, at the minimal torque value area, two interfere air flow is used to rebuilding the air flow. Based on multiply stream-tubes model, the effect of interfere air on promotion performance of blade element are studied. the results prove the interfere air method does greatly arise the torque, the attack angle of blade element at 0°~15 and 165°~180°azimuth angle, and promote the torque of single blade wind turbine with two or three blades. The paper provides a new way for vertical axis wind turbine designing and application.

Abstract: To be able to more accurate analysis aerodynamic characteristic variation under yaw of NREL Phase VI wind turbine. The influence of yaw on the aerodynamic characteristic by using a three-dimensional unsteady CFD methods based sliding mesh in this paper. To flow, the overall performance and Cp of the three-dimensional flow numerical simulation were compared with experimental results with the same wind speeds to confirm the reliability of the model at a given axial wind speed conditions. In the yaw conditions, the effect of yaw on the aerodynamic performance of wind turbine blades, changing law and reveal the aerodynamic performance is in the flow details and rules in different azimuth.

Abstract: In order to accurately analysis the aerodynamic characteristic variations of wind turbines under shear, the influence of axial and shear on the aerodynamic characteristic of a horizontal-axis wind turbine is simulated in this paper by using a sliding grid method based on FlowVision. By using the TJÆREBORG wind turbine as the object of study, a three-dimensional model of a uniform wind flow can be created. The CFD calculation results, the experimental results and the Bladed results can be used to confirm the reliability of the model. In order to investigate the effect of wind shear with regard to three-dimensional unsteady flow characteristics and a three-dimensional flow field in a wind turbine impeller, an analysis of wheel wind speed of 11m/s and an investigation of the influence of wind shear on turbine performance are carried out.

Abstract: Acoustic emission (AE) method of nondestructive check is based on exertion wave radiation and their registration during fast local material structure reorganization. It is used as a means of analysis of materials, constructions, productions control and diagnosis during operating time. In the article, it is applied to structural health monitoring of Wind Turbine Gearbox (WTG). Acoustic emission testing has been used for years to test metallic structures. More recently it has become the primary method of testing WTG; all are present in the failure of WTG. AE has been very successful at detecting all of these failure mechanisms and sometimes identifying them from amplitude analysis of the AE signals. However in large structures, the high acoustic attenuation in WTG precludes amplitude analysis unless the origin of the individual signals can be identified and corrections for the distances traveled applied to the signal amplitudes. The usual method of testing WTG structures has been to apply an array of sensors spaced so that a moderate amplitude AE signal occurring midway between them will just barely trigger each sensor.

Abstract: This paper establishes the mathematical models of the ship generator sets, including the diesel, speed governor system, synchronous generator, excitation system and static load, simulates the ship generator sets by Matlab/Simulink software, and tests the performance of each system to verify effectiveness of the models. The simulation results indicate that the whole system model meets technical requirements of military standard GJB.

Abstract: The fast network restoration is required to restore the Shipboard power system (SPS) to near pre-fault condition for proper functioning. This paper proposed an improved Particle Swarm Optimization for restoration of shipboard power system. Firstly, we proposed an improvement strategy of S-Curve Decreasing Inertia Weight. Secondly, the feedback mechanism was introduced to improve the algorithm rate of convergence. Particle swarm optimization algorithm enables to find the optimal combination of loads that can be supplied after the occurrence of the fault, considering the priorities of the loads and the constraint of balance between the total load and total generation. The proposed method is applied to a naval shipboard power system model.