Abstract
A pulse ultrasonic Doppler method has been developed for a new type of flow metering system. This new system, which is under investigation, is a hybrid of time-of-flight (TOF) type ultrasonic flowmeter and ultrasonic velocity profile (UVP) type flowmeter, and it has the advantages of these two types. Our final purpose is to apply the hybrid ultrasonic flow metering system to an accurate flow rate measurement of feed- or recirculation- water in nuclear power plants. The pulse ultrasonic Doppler method (UDM) has the capability to obtain instantaneous velocity profiles along an ultrasonic beam. The principle of the UDM flow metering system is based on the integration of an instantaneous velocity profile over a pipe diameter. Hence, the system is expected to eliminate installation problems such as entry length, and also to follow transient flow rate precisely by increasing the number of ultrasonic transducers. However, it needs reflectors for receiving ultrasonic Doppler signals. On the other hand, the TOF ultrasonic flow metering system does not need any reflector, but it needs profile factors (PFs) which depend on velocity profiles. PF is one of the important experimental coefficients for the accurate flow rate measurement. Therefore PFs must be corrected according to the changes in flow conditions.
