Experimental Investigation of the Delay Effect of Phase Transformation of Water Vapor in Shock Tube
激波管内水汽相变滞后效应的实验研究

Processes of the unsteady transient phase transformation of water vapor and gas mixture induced by rarefaction waves and reflected rarefaction waves in a shock tube were studied experimentally. The phase transformation processes of water vapor were measured by dual--wavelength light extinction method. The experimental results show that the temperature for the unsteady transient phase transformation of water vapor is much lower than the condensing--point or freezing--point occurring in the atmosphere. The more the mixture gas expands, the lower the temperature point for the transient phase transformation of water vapor is. It is mainly because the pressure of the gas mixture decreases rapidly during the processes of transient expansion that the temperature of transient the phase transformation of water vapor is much lower than that of an equilibrium phase trans.formation of water vapor. It is also shown that during the processes of the unsteady transient phase transformation of water vapor the size of the formed droplets after the transient phase transformation is kept constant, but the number density changes with time.