油圧管路の動特性を利用した遠隔瞬時流量計測手法 第２報 実時間準遠隔瞬時流量計測手法の検討

Abstract

Recently, we proposed remote and quasi-remote instantaneous flow rate measurement methods by making use of the dynamic characteristics between pressures and flow rates at two cross-sections (upstream and downstream of the pipeline) distant from the finite length along the hydraulic pipeline. By using these methods, an instantaneous flow rate at the location difficult to insert a flowmeter can be accurately estimated in real time. The remote instantaneous flow rate measurement method has been investigated using the experiment in the previous paper.This paper describes the quasi-remote instantaneous flow rate measurement method. In the case of the upstream flow rate measurement, flow rate qu (t) is estimated by implementing convolutions of measured upstream pressure pu (t) and downstream flow rate qd (t) with corresponding weighting functions gp (t) and gq (t) , respectively. The high-speed numerical operation of the convolutions is realized in real time by utilizing the preset tables on memories in the microcomputer system.The weighting functions in the time domain are obtained by the inverse Laplace transform or inverse fast Fourier transform of the transfer functions in the frequency domain which are derived from the transfer matrix. In a similar manner, downstream flow rate qd (t) can be estimated from measured downstream pressure pd (t) and upstream flow rate qu (t) .The estimated flow rate waveforms by the method are compared with directly measured ones at the same instant by a cylindrical choke-type instantaneous flowmeter which is used for calibration. The results show good agreement between the estimated and measured flow rate waveforms under an unsteady laminar flow.As a result of improving and scheming the high-speed operation of convolutions, data processing on the system in real time is achieved using only software.