Experimental Visualization for Flows over the Porous Spheres and Cylinders with/without Blowing
| Autor: | Hui-Zhen Chen, 陳慧真 |
|---|---|
| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 This thesis carries out the experiments to visualize the flowfields over burners in a wind tunnel. The smoke-generation wire and laser-sheet lighting are employed to visualize the cold flow behaviors over the burners. The parameters are incoming flow velocity (i.e. Re), blowing ejection velocity and geometric variations of burner. The cold flow visualization consists of two parts. The first one is to visualize the flow behaviors around and behind the burners without air blowing. The resultant patterns are eventually confirmed by the relative literatures. The separation angles as a function of Re for each burner are measured. It is found that the occurrence of separation for the cylinder is earlier than that for the sphere with the same diameter. It is attributed to that the flow is subjected to more frictional force in the cylinder case. The second part is to investigate the effect of the blowing from burners on the flow behaviors. The flow pattern for each burner with a fixed air ejection velocity (Vw) is described in details. For the case of 15mm-diameter cylinder, it is found that as Vw is set at 1.76 cm/s, the wake does not approach to the cylinder surface until Re increases to 907. Similarly, for the 20mm-diameter cylinder under the specified Vw of 1.32 cm/s, the wake returns to the rear of burner as Re approaches to 1,057. As to the sphere burner, the critical value of Re is 1,720 under the specified Vw of 4.72 cm/s. Moreover, for these three different burners, under the various Vw at the critical incoming flow velocity (Uin), above which the wake returns to the rear of burner, are observed. For each burner, Vw and critical Uin are correlated into an equation, respectively. Finally, the cold flow structures can partially correspond to the resultant flame behaviors, which the lift-off flame is transformed into second wake flame, at the same Re. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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