Measurement of dispersed two-phase gas-liquid flow by cross correlation of modulated ultrasonic signals

A technique for metering two-phase gas-liquid mixtures is described. The measuring apparatus consists of a concentric constriction device and an ultrasonic cross-correlation velocity meter (Coulthard 1973). The constriction device breaks up the gaseous phase and generates a near-homogeneous type of flow, with characteristics largely independent of those existing in the approach section. The mean velocity of the resulting flow is obtained by cross-correlating the modulations of two parallel ultrasonic beams, transmitted across the pipe. The peak value of the cross-correlation function is found to occur at a time delay virtually equal to the mean transit time of the mixture between the centre lines of the beams.

The main advantages of this type of non-intrusive meter are its averaging capabilities and relative insensitivity to pressure transients.