CRYOGENIC ULTRASONIC MASS FLOWMETER AND QUALITY METER

IN ORDER TO ACCURATELY MEASURE THE MASS FLOWRATE OF GASEOUS H2 BY ULTRASOUND, IT IS FIRST NECESSARY TO DEVELOP NEW TRANSDUCERS CAPABLE OF OVERCOMING H2'S LOW ACOUSTIC IMPEDANCE (Z). SECOND, IT IS NECESSARY TO DEVELOP NEW WAYS OF MOUNTING THESE TRANSDUCERS ON CONDUIT SO THAT ACOUSTIC SHORT CIRCUIT DOES NOT OVERWHELM THE RECEIVER. TWOINNOVATIVE LOW-Z TRANSDUCER (SENSOR) DESIGNS ARE HEREIN PROPOSED. THE FIRST USES SLOW LEAKY FLEXURAL WAVES OF FREQUENCY F PROPAGATING IN A CONICAL RADIATOR OF THICKNESS D. THE FD PRODUCT CONTROLS THE PHASE VELOCITY CF OF THE LEAKY FLEXURAL WAVES AND THEREBY CONTROLS THE ULTRASONIC RADIATION PATTERN IN THE H2 GAS. THE SECOND LOW-Z TRANSDUCER USES A LASER-PERFORATED PLATE TO SANDWICH THE GASBETWEEN ITSELF AND THE SOLID SURFACE OF AN ULTRASONIC PISTON. WHEN THE PISTON IS ENERGIZED, THE COMPRESSED GAS SQUIRTS THROUGH THE PERFORATIONS AS A VELOCITY-TRANSFORMED PULSE HAVING ULTRASONIC FREQUENCY COMPONENTS CORRESPONDING TO VORTICES SHED BY THE HOLES. BOTH TRANSDUCERS, IF SUCCESSFULLY DEVELOPED, WOULD ENABLE BIDIRECTIONAL FLOW OF LOW-Z CRYOGENS TO BE MEASURED AT RESPONSE TIMES <0.1 S. SUCCESS, HOWEVER, REQUIRES THAT SMALL-CONTACT-AREA MOUNTS, SLOW-WAVE STRUCTURES OR OTHER ISOLATION MEANS BE PERFECTED.