EXPERIMENTAL STUDY ON BINARY DROPLET EVAPORATION AT ELEVATED PRESSURES AND TEMPERATURES

摘要

The evaporation characteristics of single and multicomponent droplets hanging at the tip of a quartz fiber are studied experimentally at the different environmental conditions under normal gravity. Heptane and Hexadecane are selected as two fuels with different evaporation rates and boiling temperatures. At the first step, the evaporation of single component droplet of both fuels has been examined separately. At the next step the evaporation of several blends of these two fuels, as a binary component droplet, has been studied. The temperature and pressure range is selected between 400 and 700℃, and 0.1 and 2.5 MPa, respectively. A high-temperature environment was provided by a falling electrical furnace. The initial diameter of droplet was in the range of 1.1 and 1.3 mm. The evaporation process was recorded by a high-speed CCD camera. The results of binary droplet evaporation show the three-stage evaporation. In the first stage the more volatile component evaporates. The droplet temperature rises after an almost non-evaporative period and, in the third stage, a quasi-linear evaporation takes place. The evaporation of the binary droplet at low pressure is accompanied with bubble formation and droplet fragmentation and leads to incomplete microexplosion. The component concentration affects the evaporation behavior of the first two stages. The bubble formation and droplet distortion does not appear at high environment pressure.