| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 103 === Because of the narrow upper respiratory tract, patients with Obstructive Sleep Apnea Syndrome (OSAS) symptom may stop breathing momentarily during sleep and frequently downgrade their life quality seriously. Previous investigations have demonstrated that Continuous Positive Airway Pressure (CPAP) is the most efficient alternative for the OSAS treatment via delivering the compressed air stream through trachea. However, to achieve the optimal effect, a well-designed centrifugal fan is required in the CPAP device. Therefore, designing an appropriate centrifugal fan is an essential and challenging task for the OSAS treatment and become the goal of this study. At first, a sophisticated CFD code Fluent is chosen in utilizing scheme to simulate the flow pattern inside the centrifugal fan. With the high rotating speed, this work considers the flow as a compressible flow in the steady state. Later, through observe the detailed flow visualization of the reference fan for upgrading sleeping quality, a parametric study of the fan geometry is executed for realizing the corresponding influences with the emphasis on the blade curvature, rotor outer diameter, height of the rotor, and the blocking plate used to separate flow of upper and downward level. Thereafter the prototype of optimized design is manufactured by the CNC technique to carry out the corresponding experimental performance verifications. To ensure a reliable outcome, the fan’s performance and noise tests are executed in the AMCA and the semi-anechoic chambers by following AMCA-210-99 and CNS-8753 codes. Besides, by comparing the experimental and numerical results, a remarkable agreement is illustrated to validate the reliability of this CFD model and analysis. Consequently, under the operating pressure 400 mm-Aq and the same rotating speed, the aerodynamic performance of this optimum fan design with a 10dB noise reduction is significantly superior to the reference fan by 50% and 29% increases on its maximum static pressure and the efficiency, respectively. In conclusion, this study successfully establishes a reliable and systematic scheme to design the centrifugal fan used in the CPAP machine.
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