Phase identification technique for the local void sensor signal of the two phase flow

The signals from a local void sensor to get the information of phasic interface in the two-phase flow have different signal levels according to each phase at the sensor tip. For an ideal case, there should be a discontinuity in void signals at the time when the phasic interface contacts the sensor and the signal should have a discrete form corresponding to each phase. Due to the characteristics of signal processing unit and the fabrication of sensor as well as those of physics near the sensor tips, however, the signals show some interval of transient curved line near the instant that the sensor contacts the interface. To get the information of various physical variables from the measured signal, signal processing for the identification of each phase should precedes. In other words, one should convert the signals to discrete form as in the ideal case. This report describes the signal processing logic and software program to convert the continuous raw signal into the discrete form illustrating definite phase. Prior to the signal processing, one should define the phasic interface definitely. In actual flow conditions, the level varies abruptly at the instant that a sensor contacts the interface. The transient is shown at the various level states of signals. This study defines the instant of the interface as the beginning point of transient. The developed program is used by inserting it into the data acquisition software. In the latter part of this report, the example illustrating this program is presented as a part of data processing software. The signal characteristics can be different by depending on the sensor, working fluid and the experimental conditions. Therefore, it is necessary to check whether the program works well under the actual flow conditions, and if required, the set parameters in the program can be tuned