Experimental study on the liquid film characteristics of annular flow in the helical rectangular channel

A detailed insight into the liquid film characteristics in the helical channel of single screw expander is of great significance for avoiding the leakage loss of higher pressure gas to lower pressure region. The liquid film thickness and fluctuation characteristics of the annular flow on the outer side of the helical rectangular channel is measured using the digital image processing algorithm, and they are evaluated under various flow rates, dimensionless curvature, and dimensionless pitch at different angle positions. Results show that increasing the Reg will decrease the instantaneous liquid film thickness, and a larger decrease in the liquid film fluctuation is found. A larger average liquid film thickness is located at the angle of 90 degrees than that of the 180 degrees and 270 degrees. The instantaneous and average liquid film thicknesses are decreased with increasing the dimensionless curvature and dimensionless pitch at each angle position. Moreover, increasing the dimensionless curvature can weaken the effect of angle position on the liquid film thickness. The time distribution of the liquid film thickness changes dramatically in both wave height and amplitude as increasing the Rel at the smaller dimensionless pitch.