Abstract
This paper deals with a simple measurement method of unsteady flow in the pipeline. In this method, a cylindrical air chamber is arranged in the pipeline, the unsteady flow is absorbed as a change in volume of the air chamber. The unsteady flow rate is measured by using only pressure change of the air chamber caused by its volume change. In this method, the characteristic of the air chamber is utilized for the measurement. The characteristic of the air chamber is described as the relationship between the oscillate Fourier number and amplitude-ratio/phase-shift obtained from the measurement pressure of the air chamber and the adiabatic pressure that would exist for the adiabatic air chamber with the same volume change. Here, the oscillate Fourier number is the dimensionless number determined with the shape of the air chamber and the volume change frequency. In this study, the transfer function was identified from the estimated characteristics of the air chamber. The measured pressure wave was used as an input signal, and the adiabatic pressure wave in time domain was directly calculated from the transfer function. The volume change was simply calculated using the adiabatic pressure, and then unsteady flow rate was estimated. In proposed methods, good agreements were achieved between the measured and the estimated unsteady flow rate, and then the accuracies of these methods were discussed. The pulse wave which has many frequency components was measured by our method, and good agreements were achieved.
