円筒閉容器の圧力応答特性を利用した非定常流量の簡易計測方法

抄録

In this study, a simple measurement method of unsteady flow in the pipeline is proposed. In this method, a cylindrical air chamber is arranged in the pipeline, and the unsteady flow is absorbed as a change in volume of the air chamber. The unsteady flow rate is measured by using only the pressure change in the air chamber caused by its volume change. The thermodynamic state in the air chamber is affected by the speed of the change in volume and/or the shape of the air chamber. In this paper, a simple experimental formula that describes the changes in amplitude and phase of pressure wave caused by the change of state in the air chamber is investigated by using the experimental results. In the experiment, the radius and the height of the cylindrical air chamber and the frequency of volume change were varied. And the thermodynamic state in the air chamber was widely ranged from isothermal change to the adiabatic change. The amplitude-ratio and phase-shift between the measured pressure wave in the air chamber and the adiabatic pressure wave that would exist for the adiabatic air chamber with same volume were calculated. A highly correlation between the amplitude-ratio/phase-shift and oscillate Fourier number were obtained. Here, the oscillate Fourier number is the dimensionless number determined from three experimental variables. Simple experimental formulas that describe the relationship between the oscillate Fourier number and the amplitude-ratio/phase-shift were obtained from these results. Adiabatic amplitude/phase in frequency domain were calculated by using these simple experimental formulas, and adiabatic pressure in time domain was obtained through inverse Fourier transform. The volume change was simply calculated using the adiabatic pressure, and then unsteady flow rate was estimated. In proposed method, good agreements were achieved between the measured and the estimated unsteady flow rate, and then the accuracies of these methods were discussed.