Acoustic emission generated from fluid leakage

Abstract

Acoustic emission (AE) offers significant promise for the monitoring of the structure integrity. This study mainly describes laboratory experiments conducted to clarify the AE sources and characteristics of AE signals associated with the fluid leakage ie. saturated steam, subcooled water, pressurized water and air, to find out how AE signals may vary with the leak rate, the stagnation pressure and temperature, and the leak hole geometry (L/D). Signal rms value for leaks increases linearly with the square root of the leak rate for the saturated steam leakage, in agreement with the aerodynamic energy model. Signal rms values of low frequency are greater than that of high frequency. The discontinuity of the signal rms values appears near a 0.18MPa stagnation pressure for a air, saturated steam, and subcooled water due to the critical flow. The cavitation which occur above 0.392MPa stagnation pressure in a water leakage play a major role on acoustic emission source. The flashing source of subcooled water has a burst peak frequency spectrum at a low L/D ratio and large leak rate. Acoustic emission monitoring is capable of detecting leaks as small as 0.12g/s for saturated steam and monitoring the leak size.