Drop Impingement onto a Plate Heated in High-Temperature Environments

• Main Authors: Wen-ChiehHsu, 許文潔
• Other Authors: Ta-Hui Lin
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/74850139066232025399

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 100 === Past research of drop impact on a hot surface was mostly limited to a single-phase drop (water, alkane, alcohol, etc) in a room temperature environment. There was not much research concerning the phenomena of a water drop in a convective high-temperature gaseous environment or a W/O (water in oil) emulsion drop in the combustion process impinging on a heated solid plate. This study was emphasized on the phenomena and features of these two subjects. In this experiment, a smooth quartz plate, which acted as the solid surface was inserted into a small combustion chamber in a high-temperature gaseous flow at three different positions and the surface temperature of the plate was 720, 509 or 407oC. Water or W/O emulsion drops with different diameters (di) and water proportions (β) which fell freely and impinged onto the heated solid plate were observed. The results of water drop experiments showed that the impact types of water drop varying with different Weber numbers and hot surface temperatures can be classified into four regimes: Rebound, Break-up, Boiling Break-up, and Boiling Break-up with water film. And the main parameter affecting the impact regimes was the hot surface temperature; the drop diameter was secondary. The results of W/O emulsion drop experiments indicated that the impact types of W/O emulsion drop were significantly affected by the hot surface temperature (Ts) and water proportion (β), but not by the change of drop diameters (di). The results of micro-explosion observations showed that the small droplets from the disintegration of W/O emulsion drops micro-exploded in the downstream region of the hot surface for all cases investigated. However, the micro-explosion of the droplets on the heated surface from contraction of the W/O emulsion drop only occurred for some cases.