Browse Topic: Mathematical analysis
Bearings are essential mechanical components that support external loads and facilitate rotational motion. With the increasing demand for high-performance applications in industries such as semiconductors, aerospace, and robotics, the need for accurate and robust performance evaluation has intensified. Traditionally, bearing performance has been assessed using static or quasi-static theoretical approaches. However, these methods are limited in their ability to capture time-dependent behaviors, which are critical in real-world applications. In this study, a rigid body dynamics analysis was proposed to evaluate the time-dependent behavior of bearings. The methodology was first applied to a deep groove ball bearing, and the results were compared with those obtained from bearing theory to validate the approach. Subsequently, the method was extended to an automotive wheel bearing, and the time-dependent contact angles and ball loads were analyzed under axial and radial loading conditions
This study focuses on the numerical analysis of weather-strip contact sealing performance with a variable cross-sectional design, addressing both static and dynamic behaviors, including the critical issue of stick-slip phenomena. By employing finite element modeling (FEM), the research simulates contact pressures and deformations under varying compression loads, DCE (Door Closing Efforts) requirements, typical in automotive applications. The analysis evaluates how changes in the cross-sectional shape of the weather-strip affect its ability to maintain a consistent sealing performance, especially under dynamic vehicle operations. The study also delves into stick-slip behavior, a known cause of noise and vibration issues, particularly improper/ loosened door-seal contact during dynamic driving condition. This study identifies key parameters influencing stick-slip events, such as friction coefficients, material stiffness, surface interactions, sliding velocity, wet/dry condition
This research investigates the potential of salt gradient solar ponds (SGSPs) as a sustainable and effective solution for thermal energy storage. The study examines the design, construction, and performance of SGSP systems that incorporate coal cinder, comparing their performance with traditional SGSPs without coal cinder. A combination of experimental and numerical approaches is used to evaluate the thermal characteristics and energy efficiency of these systems. The findings indicate that the salt gradient solar pond with coal cinder (SGSP-CC) achieves notably higher temperatures across the Upper Convective Zone (UCZ), Non-Convective Zone (NCZ), and Lower Convective Zone (LCZ), with measured temperatures of 42.57°C, 56.8°C, and 69.86°C, respectively. These represent increases of 7.53%, 12.01%, and 15.49% over those in the conventional SGSP (SGSP-C). Additionally, the energy efficiency gains in the UCZ, NCZ, and LCZ for the SGSP-CC are noteworthy, with increases of 38.06%, 39.61%, and
Direct injection strategies have been successfully used on spark ignited internal combustion engines for improving performance and reducing emissions. Among the different technologies available, outward opening injectors seem to have found their place in renewable applications running on gaseous fuels, including natural gas or hydrogen, as well as in a few specific liquid fuel applications. In order to understand the key operating principles of these devices, their limitations and the resulting sprays, it is necessary to accurately describe the pintle dynamics. The pintle’s relative position with respect to the injector body defines the internal flow geometry and therefore the injection rates and spray characteristics. In this paper both numerical and experimental investigations of the dynamics of an outward opening injector pintle have been carried out. The injector average flow rates and instantaneous pintle position have been experimentally measured at a variety of pressures and
The end-gas auto-ignition and associated pressure wave generation in a premixed gas with a spatial distribution is numerically investigated. This study assumes that the auto-ignition phenomenon in the end-gas of PCCI combustion, a next-generation combustion method which is expected to achieve both low fuel consumption and low emissions at a high level. Detailed numerical analysis considering the chemical kinetics on the one-dimensional compressible fluid flow with high spatial and time resolution was performed to clarify the detailed phenomena of the auto-ignition and onset of the pressure wave and its propagation in the end-gas. Followings are results. (1) The pressure wave generations related with the auto-ignition in the end-gas is categorized into two types. The cases that the auto-ignition velocity, which is the localized auto-ignitive propagation velocity relative to the unburned mixture, exceeded the local sound speed, or not. The spatial distribution of the equivalence ratio in
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