Experiments on Nonequilibrium,Nonstationary Expansion of Water Vapour/Carrier Gas Mixture in a Shock Tube.

摘要

The investigation of condensation process in a nonstationary nonequilibrium expansion of water vapour/carrier gas (ultra pure N2) mixture is presented here. The density variations,pressure variations and onset of condensation due to such expansion,are monitored at two fixed locations in the driver section of the shock tube by using a laser Fabry-Perot interferometer, a differential interferometer and piezotrons transducer devices. The effect of the cooling rate on the supersaturation at onset of condensation and its delay time (nonequilibrium zone) is determined. An empirical relation is derived between the supercooling and the rate of cooling at onset of condensation. A theoretical analysis is performed using this empirical relation in order to determine the location of the onset of condensation in such expansions. It is shown that the location of the onset is uniquely determined for a given initial driver condition, e.g., (1) relative humidity, (2) vapour mass fraction,and (3) temperature. A parametric study,using these 3parameters is also given. The experimental findings are in agreement with the theoretical prediction of onset. (Author)