Details

Autor(en) / Beteiligte

• Nomura, Hiroshi
• Ujiie, Yasushige
• Rath, Hans J.
• Sato, Jun'ich
• Kono, Michikata

Titel

Experimental study on high-pressure droplet evaporation using microgravity conditions

Ist Teil von

• Symposium, International, on Combustion, 1996, Vol.26 (1), p.1267-1273

Ort / Verlag

Elsevier Inc

Erscheinungsjahr

1996

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Evaporation of an individual fuel droplet at high pressures and high temperatures has been studied experimentally under microgravity conditions. A suspended n-heptane droplet was used in the experiments at pressures in the range of 0.1–5.0 MPa and temperatures varying from 400 to 800 K. Temporal variations of the droplet diameter were measured with a computer-aided image analysis system. Microgravity conditions, which were produced by using 5-m and 110-m drop towers and parabolic flights, were employed to prevent natural convection that complicates the phenomena. It was observed that dense fuel vapor surrounded a droplet and the droplet surface became obscure at high pressures and high temperatures. The slope of the temporal variations of the squared droplet diameter initially increases but later becomes approximately constant at ambient pressures below the critical pressure of the fuel. At a pressure of 5.0 MPa and temperatures below the critical temperature, the slope becomes less in the latter half of the evaporation lifetime. The ratio of the initial heat-up time to the evaporation lifetime was used as a measure of unsteadiness of droplet evaporation. The ratio is almost independent of ambient temperature at an ambient pressure of 0.1 MPa, but, as ambient pressure is increased, its tendency to rise with ambient temperature becomes noticeable. Corrected evaporation lifetime t c decreases monotonically as ambient temperature is increased. The slope of its curve becomes steeper as ambient pressure increases. Dependence of t c on ambient pressure changes according to ambient temperature. Above 550 K, t c decreases as ambient pressure is increased. Below 450 K, t c tends to increase as ambient pressure is increased. It is suggested that there exists a certain ambient temperature at which ambient pressure has little effect on t c .