Study of Critical Flow : Completely Separated Gas-Liquid Two-Phase Flow

Abstract

Critical flow is studied for a completely separated two-phase flow which is a compressible gas flow coexisting with an incompressible liquid flow without mutual mixing within a constant-area duct. It is predicted from a theoretical analysis that the critical state appears at the exit of the duct with the condition : M_q=1+KM³_g; where K=(1-x)/x(p_g/p_i)²(a/u_i)³, M_g : mach number of gas flow, x : quality, p_g : density of gas, p_i : density of liquid, a : sonic velocity of gas, and u_i : velocity of liquid flow. The two quantities M_g and K included in the afore-mentioned equation have a possible range of 1≤M_g<√(3) and 0≤K<2/√(27) respectively. For the experimental verification of the analytical prediction, the condition of a completely separated two-phase flow is successfully realized in a specially designed apparatus with use of air and water. The state of flow at the exit of the duct is determined quantitatively by making use of the characteristics of the present two-phase flow, and the data thus obtained reveal that the analytical prediction afore-mentioned is satisfied in the experiment.