| Summary: | 碩士 === 國立勤益科技大學 === 冷凍空調系 === 99 === In this study, an experimental method was conducted. The experiment was performed by using a test bench specially designed to simulate the inlet clearance leakage of a centrifugal fan. The pressure drop and air volume flow rate are measured by utilizing a wind tunnel apparatus following AMCA-210-99 fig.12 code. In the thesis different radial clearance(ε, 0.75, 1.5, 3, 5, 7.5 mm), overlap length(L, 10, 20, 30, 40, 50 mm) and rotating speed(N, 0 ,600 ,1200 ,1800 ,2400 ,3000 ,3600 rpm) were tested and analyzed how to affect clearance drag coefficient(Cd). Moreover, experimental data of these three parameters were summarized and processed to induce two empirical equations correlate with Cd.
The experiment results show that (1)When N, ε is fixed, Cd increased gradually as L increased. However, when ε increases gradually, the effect of increasing overlap length to increase Cd will more and more weak. when ε is 7.5 mm, increases L instead to cause Cd to drop. (2)when ε, L is fixed, Cd increased as N increased gradually, the phenomena show that rotation effect will increase the axial flow resistance, thereby reducing clearance leakage, and the effect is stronger in large clearance than in small one.
The first Cd empirical equation derived from 0.75mm, 1.5mm and 3mm three clearance experimental data showed that Cd was correlated with three parameters, , , . The influence effect of the three parameter to Cd from large to small were , , , respectively. The error of this empirical equation within the suitable clearance range is ± 13.3%. The second Cd empirical equation derived from 1.5mm, 3mm, 5mm and 7.5 mm four clearance experimental data showed that Cd was correlated with three parameters, u, , . The influence effect of the three parameter to Cd from large to small were , , u, respectively. The error of this empirical equation within the suitable clearance range is ± 22%.
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