The aim of the current paper is to analyse the effect of an air pocket on the transient pressure wave signal using physical data. Transient pressure data were collected from an experimental laboratory facility assembled at Instituto Superior Técnico. The pipe system has a reservoir-pipe-valve configuration and the pipe is made of copper, is 15 m long and has a 20 mm inner diameter. The simulated entrapped air pocket is located in the middle of the pipe. Each test was repeated several times (ca. 20 times for non air pocket tests and 5 times for air pocket tests) for each flow rate in order to obtain mean and standard deviation values in time of the pressure signal. Transient pressures were collected at 40 kHz acquisition frequency to illustrate the signal post-processing procedure. Mean pressure signal values and down-sampled values were calculated and used in the subsequent analysis. Collected data have shown that maximum overpressures can be higher than the Joukowsky maximum pressure pulse depending on the air pocket initial volume and initial Reynolds number. A reflected pressure wave is generated associated to the entrapped air contraction and expansion. A clear pressure wave delay and damping is observed for the air pocket tests.
Pressure wave behaviour due to entrapped air in hydraulic transient events
GHEZZI, EMANUELE;Ferrante, M.;
2018
Abstract
The aim of the current paper is to analyse the effect of an air pocket on the transient pressure wave signal using physical data. Transient pressure data were collected from an experimental laboratory facility assembled at Instituto Superior Técnico. The pipe system has a reservoir-pipe-valve configuration and the pipe is made of copper, is 15 m long and has a 20 mm inner diameter. The simulated entrapped air pocket is located in the middle of the pipe. Each test was repeated several times (ca. 20 times for non air pocket tests and 5 times for air pocket tests) for each flow rate in order to obtain mean and standard deviation values in time of the pressure signal. Transient pressures were collected at 40 kHz acquisition frequency to illustrate the signal post-processing procedure. Mean pressure signal values and down-sampled values were calculated and used in the subsequent analysis. Collected data have shown that maximum overpressures can be higher than the Joukowsky maximum pressure pulse depending on the air pocket initial volume and initial Reynolds number. A reflected pressure wave is generated associated to the entrapped air contraction and expansion. A clear pressure wave delay and damping is observed for the air pocket tests.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
