Research Of Flow Measurement Technology Based On Ultrasonic Transit-time Difference Method

In recent years, the ultrasonic technology has been widely used and quickly developed in the field of flow measurement. The fluid carries the information about flowing velocity when the ultrasonic wave is propagating in the fluid. Various methods can be used to receive the ultrasonic wave to extract the relevant information and calculate the flow velocity and the instantaneous flow. The popular methods of flow measurement include the Transit-time Difference Method and the Doppler Method. The ultrasonic flow-meter will not impede the movement of the fluid and be particularly suitable for high-volume, large diameter measurements. The Transit-time Difference Method, with high accuracy of measurement, is not suitable for fluid with solid particles inside, and the flow velocity also affects the accuracy. The Doppler Method is widely used in the field of the flow measurement with suspended particles, bubbles inside or two-phase flow.In the paper, based on the Ultrasonic Transit-time Flow Measurement theory, the FPGA and DSP system are used as the control and operation core of the system. In this system, a continuous sinusoidal signal is used as the excitation of the ultrasonic sensor, and the flow velocity is good to know by measuring the phase difference of the receiving signal and the transmitting signal. By the way of transforming the measurement of time debris into the measurement of electrical parameter, with the full use of the Cumulative Measurement Method, a high precision, multi-functional single-phase ultrasonic flow-meter is designed. Firstly, this paper gives a brief introduction of the development and research background of ultrasonic flow measurement technology, and the ultrasonic flow measurement theory based on the Transit-time Difference Method. Based on the theory, the measurement scheme of ultrasonic flow-meter is proposed. The instantaneous flow in the pipe can be acquired by measuring the flow rate along the center line of the pipe, where the flow rate trends to be steady. The possible factors that may affect the accuracy of measurement have been analyzed and practicable solutions are given in this paper. On these bases, an ultrasonic flow-meter is designed to measure the flow in the pipe, including the design of signal transmitting and receiving circuit, charging measurement circuit, computing and controlling core circuit. During the design, an adequate debugging and test for each part have been done. Customized system software for the flow-meter designed before need to be coded to accomplish the flow measurement. Then, details of the flow measurement model and ultrasonic sensors used in the flow-meter are also given in the paper. To verify the design of ultrasonic flow-meter, an experimental apparatus is designed, which produces incremental airflow with uniform velocity. The experimental data can be used to evaluate the reliability and stability of the ultrasonic flow-meter designed.Finally, a summary to the task achievement of this subject is done in the end of this paper. Also, the future picture of the research work is given to improve the performance of the ultrasonic flow-meter.