Pressure wave excitation and water pipeline leakage detection by using an air nozzle

Abstract Pressure wave is widely used in leakage detection because of its property of carrying energy and signal. However, the existing pressure wave generating devices used for leakage detection have certain limitations in terms of portability, safety and controllability. Based on this, a device which used compressed gas to impact water pipeline by the nozzle to actively excite pressure wave was designed (nozzle type pressure wave generator) and applied to the experimental platform for water pipeline. The excitation characteristics of the pressure wave generator was explored through experiments, and a 2D numerical model based on k – ϵ turbulence was further developed to describe the excitation flow. Finally, experiments of single and double points leakage were conducted in a 123.3 m pipeline to identify and locate pipeline leakage. The experimental results illustrated that safety-controllable pressure wave was portably generated by the nozzle type pressure wave generator. When intake pressure was 608 kPa, the maximal pressure amplitude was about 364 kPa, which was significantly higher than closed valve and negative pressure wave methods under the same flow condition. Moreover, there was a critical impact time of 120 ms which made the maximum pressure amplitude. With the increase of intake pressure and liquid level, the pressure amplitude also increased. Increasing the diameter of the nozzle throat, the length of the contraction section and appropriate expansion angle of the nozzle was conducive to the increase of the pressure amplitude. Furthermore, stable continuous pressure wave performance was demonstrated when the vertical pipe near nozzle outlet was connected to the atmosphere and the impact interval was controlled. Single and double points leakage were well identified and localized by utilizing the pressure wave excited by the nozzle with a maximum relative and absolute error of 1.16 m and 6.82% respectively under the working condition in this paper.