A measurement method of the flow rate in a pipe using a microphone array

Abstract

A method of measuring the flow rate in a pipe is proposed. The method utilizes one-dimensional acoustic pressure signals that are generated by a loud speaker. A microphone array mounted flush with the inner pipe wall is used to measure the signals. A formula for the flow rate, which is a function of the change of wave number, is derived from a simple mathematical model of sound field in the pipe conveying a viscous fluid. The change of the wave number, which is one of the results caused by flow, is estimated from the recursive relation among the measured microphone array signals. Since measurement errors, due to extraneous measurement noise and mismatch of response characteristics between microphones, exist in the estimated flow rate, a method of compensating the errors is proposed. By using this measurement method, the flow rate can be obtained more accurately than that of our previous method. To verify applicability of the measurement method, numerical simulation and experiments are performed. The estimated flow rates are within 5% error bound.

Prediction of Flow Velocity from the Flexural Vibration of a Fluid-Conveying Pipe Using the Transfer Function Method

“…Moreover, these devices incur lower maintenance costs, are easy to install, and do not affect the flow rate [4]. Thus far, non-invasive flow measurements using ultrasonic waves and acceleration signals have been developed [5][6][7][8][9][10][11]. By considering the velocity profiles across a water pipeline, the flow rate using hybrid ultrasonic flow meter was calculated [5].…”

“…In another study, the velocity under two-phase flow was measured using ultrasonic signals, the corresponding flow was visualized [7,8]. The wavenumbers of the fluid conveying pipe by using the differences of acceleration, microphone signals, and added mass were estimated to predict its flow velocity [9][10][11]. Wavenumbers related to the characteristics of the pipeline system are essential for measuring the flow rate.…”

Adaptive calibration of a three-microphone system for acoustic waveguide characterization under time-varying conditions

“…5,6 Several of such methods have been designed to take measurements in the presence of a steady mean flow. [7][8][9][10][11] In most cases, the measurements are "non-intrusive" in the sense that wall flush mounted pressure sensors of near-zero input admittance are employed, meaning that minimal interference with the acoustic field can be assumed.…”