NASA’s Marshall Space Flight Center has developed a unique prototype for measuring the liquid level in a tank, employing a novel process. The technology can operate in a wide range of environments, including high and low temperatures and pressures, and is simpler and less expensive than other optical sensing techniques. The instrument also provides far greater accuracy and faster results in cryogenic conditions than typical cryogenic liquid metering methods. It is ideal for cryogenic and non-cryogenic ground tank metering applications, and zero-gravity systems that include stratification or settling techniques.
The device for measuring liquid levels in tanks was initially developed for rocket engine testing. Scientists needed to determine the amount of cryogenic liquid that was being used in the testing quickly and accurately. Data often was very difficult to obtain because such systems usually involve constant mixing between gaseous and liquid states, which can lead to turbulent flow, cavitation, and sloshing.
Other sensors that measure liquid levels in tanks require complicated tank modifications and detection instruments, increasing cost and complexity. Other cryogenic metering systems register the thermal change between liquid and gas fluid phases, limiting accuracy in cryogenic conditions. In contrast to these systems, NASA’s device allows operation at high temperatures and pressures in corrosive environments, and can precisely measure liquid levels to 0.1% of the sensor length with gigahertz data acquisition rates.
The instrument avoids explosion hazards, and requires no electrical signals in the tank. It offers a very rapid response time, enabling measurement of rapidly changing fluid levels or sloshing liquids. Other features include the ability to accommodate snaking through access ports or shaping to fit tank contours, and incorporation directly into a plastic tank, reducing cost and eliminating the need for holes in the tank in some applications.
Applications include rocket propulsion testing, engine fuel tanks, and cryogenic tanks in the aerospace industry, as well as liquid hydrogen fuel tanks, petroleum, gasoline, and liquid natural gas tanks in the automotive industry.