When the temperature in the core reaches about 100 million degrees, the helium will begin to fuse into carbon by a reaction known as the triple-alpha process, because it converts three helium nuclei into one carbon atom. And roughly 1.2 billion years after it leaves the main sequence, at the height of its glory as a red giant, the center of the helium core of the Sun will become sufficiently massive, dense, and hot that something amazing will happen: within a matter of minutes, it will ignite and burn. The temperature and pressure in the Sun's core will soar to 10 times their current values. It is an odd paradox: even as the outer layers of a red giant star are expanding into a huge but tenuous cloud, its inner core is contracting down to form a buried white dwarf. As the helium "ashes" continue to pile up at its center, a higher fraction of them turn electron-degenerate.
The model reproduced the range and change tendency of the experimentally measured oscillation frequency.The beginning of the end for a red giant the mass of our Sun occurs very suddenly. The resonant frequencies under both the 100% natural gas and hydrogen–natural gas conditions were successfully calculated. A whole piping model was then developed by adding a casing and an air supply pipe to the combustor. However, the model could not reproduce the experimental value under the hydrogen–natural gas condition. A swirler-combustor model was then constructed to get closer to the actual configuration and shape of the experimental setup. Conversely, the experimentally observed frequencies under the hydrogen–natural gas condition were not accurately predicted. The experimental frequencies of the 100% natural gas condition were successfully predicted. To analyze the resonant frequency, two- and four-region models considering unburned and burned regions of the combustor were developed. Journal of Verification, Validation and Uncertainty QuantificationĪ combustion oscillation experiment showed combustion oscillation frequencies of around 350 Hz when only natural gas was used as fuel and approximately 200 and 400 Hz when a hydrogen–natural gas mixture was used.Journal of Thermal Science and Engineering Applications.Journal of Offshore Mechanics and Arctic Engineering.Journal of Nuclear Engineering and Radiation Science.Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems.Journal of Nanotechnology in Engineering and Medicine.Journal of Micro and Nano-Manufacturing.Journal of Manufacturing Science and Engineering.Journal of Engineering Materials and Technology.Journal of Engineering for Sustainable Buildings and Cities.Journal of Engineering for Gas Turbines and Power.Journal of Engineering and Science in Medical Diagnostics and Therapy.Journal of Electrochemical Energy Conversion and Storage.Journal of Dynamic Systems, Measurement, and Control.Journal of Computing and Information Science in Engineering.Journal of Computational and Nonlinear Dynamics.Journal of Autonomous Vehicles and Systems.ASME Letters in Dynamic Systems and Control.ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part B: Mechanical Engineering.Mechanical Engineering Magazine Select Articles.
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