Papers by Keyword: Transmission Characteristics

Abstract: The gas diffusion layer (GDL) is a crucial component of Proton Exchange Membrane Fuel Cells (PEMFC), water flooding will occur during the operation of PEMFC, resulting in performance degradation, and its water management plays a significant role in PEMFC performance. To investigate the transport mechanism of liquid water in GDL, the lattice Boltzmann method to simulate the behavior of GDL droplets using the 'random reconstruction' method. The accuracy of this model by calculating the tortuosity and comparing it with reported results in literature. The effects of different GDL structural parameters on permeability were studied. Finally, the conductivity and thermal conductivity of the GDL in various directions were examined. The results indicate that the porosity error of the three-dimensional structure model of GDL is within 0.01, enabling a realistic simulation of the GDL structure. The average error between the calculated results and the Bruggeman equation is only 2.5362%, and the average error compared to the reference results is less than 6%, demonstrating the model's high accuracy. As the porosity and fiber diameter of the GDL three-dimensional structure model increase, the permeability also increases. Conversely, the permeability decreases with an increase in the thickness of the GDL three-dimensional structure model. Moreover, an increase in GDL porosity leads to a gradual decrease in electrical conductivity and thermal conductivity in both the thickness and plane directions, with a more pronounced effect on the thickness. This study uncovers the transport characteristics of liquid water in the gas diffusion layer, which can inform the optimization of GDL structure design and serve as a theoretical reference for enhancing water management in proton exchange membrane fuel cells. Future research directions will focus on further optimizing the three-dimensional structure of GDL to improve its transmission characteristics and overall performance.

Abstract: The article presents the results of unpublished research on the new generation current sensors, designed on the basis of cold-cast magnetic materials. The development of current sensors with core cast focused primarily on the possibility of their application for the measurement of large currents and for the purpose of measuring the electricity and power electronics. The article presents the results of measurements of transmission characteristics of the prototype sensor, the sensing ampli­fier design and measurement results of the entire scanning unit.

Abstract: The vibration of pipe systems not only worsens their working environment, but also may result in the loosening of mechanical connections between pipelines, as well as the structural fatigue damages. This paper presents a new method for vibration control of pipe systems, by specially designing some pipe structures based on two vibration reduction mechanisms of phononic crystals, for the vibration frequency in the actual tests. Some numerical analyses are then performed about the effects of the parameters of vibrator, for instance, the ratio of material components, and the numbers of period. The simulation results demonstrate that the proposed phononic crystals structures can reduce the vibration of pipe systems effectively.

Abstract: In order to analyze the transmission characteristics of the knuckle-triangle working mechanism for servo mechanical presses, an experimental prototype was set up, and a wireless measurement system was developed, to measure the kinematic and dynamic characteristics of the working mechanism. The working principle of the dynamic measurement was expressed. The forming force applied to the slide was measured by a donut-shaped load cell. The driving torque applied to the crank was measured by a resistance strain gage. To collect the testing signals of the forming force and driving torque conveniently and synchronously, a wireless measure system based on WiFi is proposed. Moreover, when the input crank rotates at different angular speeds, the slide stroke curves were measured by a grating scale. The experimental results showed that the developed system can perform wireless measurement, and provide experimental basis for the analysis of kinematic and dynamic characteristics of the working mechanism with servo input.

Abstract: Punching mechanisms with servo input are typical variable-input controllable mechanisms. By means of extending the output link infinitely, the Stephenson Ⅲ six-bar linkage is evolved into a six-bar punching mechanism with a slide. A virtual prototype model of this novel punching mechanism was established by using the software ADAMS. The model includes geometry, load and drive, total three sub-models. Based on the model, the kinematic and dynamic characteristics of the slide with variable-input crank motion and instantaneous large load were simulated. The numerical results showed that the Stephenson’s six-bar punching mechanism had good transmission characteristics, improving the working performances and production efficiency, reducing the manufacturing costs of servo mechanical presses.

Abstract: Twin-rotor piston engine is exceedingly compact, and several times more power dense than conventional IC engines. It is necessary to analyze the transmission characteristics of the special geared linkage mechanism which is used for the power transmission equipment of the engine. Transmission angle is mainly adopted in order to obtain the transmission characteristics. Firstly, the force transmission behavior of one end of the output component is derived through the force analysis of the planet gear. Secondly, the torque transmission angle is proposed based on the multi-point force situation. Lastly, the torque transmission angle is depicted and analyzed in detail through the equivalent composite force graphical method. The result shows that the geared linkage mechanism will not produce counteractive torque to the rotation direction and has no dead point.

Abstract: Due to those disadvantages of the cycloidal-pin wheel transmission, such as low efficiency, low bearing capacity and poor rigidity, a new kind of axis-fixed cycloid transmission is proposed after generalizing those advantages of axis-fixed drive, cycloid drive and oscillating-tooth drive. Special output mechanism is unnecessary here because the motion is exported directly by the cycloid gear. Thus, there are many advantages of this new transmission-simple structure, small size, high transmission efficiency and large torsional stiffness. The transmission theory and basic structure are analyzed and the formula for the transmission efficiency is derived. A prototype is manufactured and the efficiency experiment is carried out on the test bed. The experimental result verifies the correctness of the therotical analysis.

Abstract: The free vibration of a fluid/structure system consisting of a cylindrical blockage submerged in a liquid enclosed by a cylindrical shell is investigated for the purpose of pipe line transportation monitoring. The wavenumbers are obtained and the reflection and transmission characteristics of these waves at the blockage interfaces are investigated theoretically. Reflection and transmission ratios are obtained in the axisymmetric mode, as functions of frequency. High order modes play an important role in the near field of the discontinuity and are taken into account.

Abstract: Until now, surface defects of continuous casting slab have been removed by the enforced surface scarfing to produce high quality steel materials. An evaluation technique for surface and internal defects of slab is required to enhance the production of medium carbon steels and acquire defect-map. Accordingly as a preliminary step, longitudinal wave testing and Rayleigh wave testing were carried out on slab specimens of medium carbon steel to get basic transmission characteristics of ultrasonic waves. This research provides as basic data for on-line defect estimation using a laser ultrasonic or EMAT in non-contact ultrasonic detecting techniques in future.