Accurate measurement of gaseous hydrogen flow-rate by ultrasound requires new transducers that overcome hydrogen's low acoustic impedance (Z). New ways of mounting these transducers must be found to avoid acoustic short circuits. Two low-Z transducers will be designed. The first uses slow, leaky flexural waves propagating in a conical radiator. The frequency-distance product controls the phase velocity of the leaky flexural waves and the ultrasonic radiation pattern in the H2 gas. In the second, the gas is sandwiched between a laser-perforated plate 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 measure the bi-directional flow of low-Z cryogens with response times o0.1 seconds. Success, however, requires that small-contact-area mounts, slow-wave structures, or other isolation means be perfected.
Potential Commercial Applications: Applications could be in measurement of mass flow rate and quality of a variety of single and two-phase fluids; as a fast-response, bi-directional flowmeter to measure oscillatory and pulsating flows in engines and pumps; and in biomedical measurements of the breathing dynamics.STATUS: Phase I Only
