Journal of Engineering and Thermal Sciences
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Measurement of stability of a pipe system with flowing fluid
Get PDFThe two dimensional system of coupled vibrating pipes is investigated. The model of a pipe system consisting from two dimensional beams is employed. The problem of stability because of the reduction of stiffness caused by the flow of fluid is solved and the stability eigenmodes are determined. The places where the deflections of the stability eigenmodes are large are recommended for the location of measurement devices
Comparative blast study of simulation and approximation method of armored vehicles
Get PDFTo protect the troopers, it is important to consider the assessment of hazardous areas inside the military vehicle. For armored vehicles, the design, analysis, and test of explosive seat protection are significant to ensure the trooper survivability. Particularly, we note that the significant factor affecting the trooper survivability is ability of trooper seat to absorb shock generated by the explosion. Therefore, this research focused on the allegorize between blast simulation method and blast approximation method of armored vehicle. A crucial step for armored vehicles design is to analyze the pressure caused by the explosion. However, the blast simulation method does not always provide accurate results. To ensure that the models are reliable, the purpose of this research is to determine and compare the results between the created model and the theory. Results showed that the simulation models provided the force that affects the vehicle similar to the theoretical-based method. The simulation model designed can be developed and applied to design the various components of the armored vehicle to predict the blast behavior
Investigation of radial force and hydraulic performance in a centrifugal pump with different guide vane outlet angle
Get PDFIn order to investigate the effect of the guide vane outlet angle on the performance of centrifugal pumps, a centrifugal pump with guide vanes was used as the research model and its specific speed is 165. Keep all the other geometry parameters of the pump as constants, the guide vane outlet angle was designed to be 28°, 20°, 15°,10°, 5° and 3° respectively. The whole flow field in the pump under different guide vane outlet angles was simulated by commercial code CFX and the simulation was unsteady. The simulation results were validated by experiment results. According to the simulations, the hydraulic performance, internal flow and radial force of the pump under different guide vane outlet angles were compared and analyzed in detail. The research results indicate that the head and efficiency of the pump are the best when the guide vane outlet angle is 10°. With the decrease of the blade outlet angle of guide vane, the length of flow channels in the guide vane become bigger and its width gets smaller, the uniformity of inner flow in the centrifugal pump gets better, and therefore the radial force on the impeller reduces. With the decrease of the guide vane blade outlet angle, the pulsation frequency of radial force does not change, but the pulsation amplitude of the radial force reduces obviously. The vector distribution of the unsteady radial force is symmetric around the origin and mainly lies in 5 regions, which is same as the blade number of impeller
Damping multi-model adaptive switching controller design for electronic air suspension system
Get PDFThis paper presents the design and verification of a damping multi-model adaptive switching controller for electronic air suspension (EAS) system. In order to improve the convergence rate of identification algorithm of conventional adaptive controller, multiple local linear full-car vehicle models of EAS system with fixed parameters are established according to the actual damping control process of EAS for different vehicle driving conditions and an adaptive model whose initial value of parameters can be re-assigned is introduced to enhance the system control precision. The model switching control strategy based on minimum error is used to select the best matching model online and the optimum damping force is regulated by adaptive control algorithm, thus constituting the damping multi-model adaptive control for EAS. Simulation results show that the control method proposed in this paper can improve the damping regulating performance of EAS effectively in wide range driving conditions, especially for the case of sudden change in driving conditions
Adaptive vibration control of a nonlinear quarter car model with an electromagnetic active suspension
Get PDFThe main goal of the active suspension system used in a vehicle is reducing the vehicle vibration. In this study, an adaptive control approach is applied to a nonlinear quarter car model with an active suspension system. An electromagnetic actuator is used in the active suspension system. The attractive aspect of the applied control method is not required to both vehicle parameters and actuator parameters. Using Lyapunov based stability analysis; it is shown that all the signals in the closed loop system are bounded. Hence, the applied controller ensures the vibration reduction of the nonlinear quarter car model. The simulation results show that the applied adaptive controller provide a good ride comfort despite the parametric uncertainties while keeping suspension travel and tire deflection in acceptable limits
Optimum design of printed electronics inkjet printer using response surface model and multi-objective genetic algorithm
Get PDFThe purpose of this project is to improve the optimization design of complex mechanical structure based on the combination of response surface model and multi-objective genetic algorithm (MOGA). First of all, we built the finite element model (FEM) for the printed electronics inkjet printer through experimental modal analysis (EMA) and finite element analysis (FEA). The analysis of the static and dynamic characteristics of the FEM confirms the weak points of the structure and its actual performance. Next, using central composite design (CCD) method, it selects sample points in the design space and carries out numerical simulation and establishes the initial second order response surface model with eight design variables to further determine the inkjet printer’s first order natural frequency, weight and maximum deformation of the inkjet head. Finally, it carries out an approximation optimization of response surface model using MOGA to obtain the Pareto optimal solution set. Our simulation results determine that the optimal solution can increase the first order natural frequency of the inkjet printer by 36.3 % to effectively avoid the resonance region caused by the servo motor excitation. The maximum deformation of inkjet head decreases by 33 % and the weight of the inkjet printer can be reduced by 19.5 %. We believe that optimization can improve the performance of the inkjet printer and reduce its weight at the same time. The method proposed in this study is suitable for multi-objective optimization of complex structures similar to the printed electronics inkjet printer
Analysis on fatigue life of a certain gear transmission system
Get PDFAs the certain gear transmission system becomes more complex and precise, the flexibility of shaft will influence the dynamic response of system. Build the rigid model of gear system and the finite element model of the gear shaft. Establish the rigid-flex coupling model with the virtual prototype technology, simulation and make a contrast between rigid model and rigid-flex model. Find the influence of shaft flexibility on the dynamic response of gear system, which can enhance the accuracy rating of the model. With the increase of the bearing interval, the impact of coupling will become severely. Furthermore, we analysis the influencing factor of the fatigue life of the shaft. Analysis the law of the fatigue life in the different d/D, the result can provide a reference for the optimum structural design of the gear transmission system
Research on active control strategy of vibration in complex environment
Get PDFFxLMS algorithm has been widely used in active vibration control field theoretically. This paper is aimed at the complex situations in actual environment including interference and occasional divergence due to algorithm. Firstly the effects to control process and result caused by those situations are analyzed, then select different means based on different characteristics of the effects to deal with them, and integrate all those means to derive a new optimal control strategy which is suitable to actual applications. The experiment shows that the improved control strategy can response effectively different occasional situations without any weakness of normal control, and it can promote the practical application ability of the algorithm and is able to adapt to complex environments in active vibration control
Numerical analysis of aerodynamic features of porosity-optimized wind barriers and running safety of train
Get PDFA 2-D model-bridge with different porosity barriers is simulated with CFD to explore the windbreak mechanism. The accuracy of simulation is verified by a wind tunnel test. The porosity of the barriers is optimized by analyzing the aerodynamic features of the train-bridge system subjected to cross winds. It is found that wind velocity on the windward track changes greater than that on the leeward track. The train rolls towards the barrier when porosity is lower than 10 % and away from barrier when porosity is higher than 30 %, and the rolling moment is minimized when porosity is 30 %. The dynamic response of running train with and without wind barrier is compared, from which the windbreak effect of barrier is identified
Research on liquid sloshing model of partially-filled tank by nonlinear external excitation
Get PDFThe parameters of elliptical tank can greatly affect the roll stability of the elliptical tank with different filled levels, the exact equations for the mass centre of the tank were developed. The solutions of the transient mass centre of sloshing liquid in a tank with modified elliptical cross sections were obtained by a new vehicle rollover model. To achieve Euler transform 6-degree of freedom (DOF) motion equation of tank, Liquid Sloshing model of partially-filled tank was built by Nonlinear External Excitation. In addition, MATLAB ODE was used to investigate the numerical simulation. According to the different filled level of the tank by simulating, force and moment about X, Y and Z-axis of the coordinates of the mass centre were obtained. It is shown that the nonlinear mathematical models of liquid sloshing and vehicle motion equation can accurately describe the tank truck dynamic response in turing. The finding of this study may provide a theoretical basis to improve the roll stability of the tank