Development of ultrasonic transducers for measuring liquid flow rates at high temperature and high pressure

Ultrasonic flowmeters developed at ONERA within the framework of studies on the pogo effect in liquid propellant rocket engines permit the measurement of propellant flowrates, with a 200 Hz passband and an accuracy of 1% at pressures up to 30 bar and temperatures from - 180 C to + 80 C. These devices, now industrially available, are in use in Europe, the U.S. and Japan. The extension of this kind of instrument to the conditions of temperature and pressure encountered in nuclear engineering has required fundamental changes in the design of the ultrasonic probes. During the numerous technological studies which are presented several solutions were tried, of which two appear satisfactory. Theoretical difficulties arising from temperature gradients in the duct have also had to be overcome. The transducers were tested in water up to 300 C and 200 bar; an accuracy of the order of 1% has been obtained up to 200 Hz.