Cryogenic Liquid Level-Sensing using Fiber-Optic Strain Sensor (FOSS) Technology Project

<p>Armstrong innovators have developed a highly accurate method for measuring liquid levels using optical fibers. Unlike liquid level gauges that rely on discrete measurements to give broad approximations of liquid levels, Armstrong’s novel method provides measurements at ¼-inch intervals within a tank. The system uses fiber optic Bragg sensors located along a single fiber optic cable. These sensors actively discern between the liquid and gas states along a continuous fiber to pinpoint the liquid level. This significant leap forward in precision and accuracy in liquid level sensing offers significant benefits to many industries. Designed to monitor a rocket’s cryogenic fuel levels, the technology can be used in many medical and industrial applications.</p><p><strong>Work to date</strong>: The technology has been demonstrated in multiple environments using conventional validation techniques. First, water level measurements have been conducted to demonstrate operation within a benign environment. Second, liquid level measurements were conducted in liquid nitrogen using a 6-foot dewer. Measurements also were conducted within a liquid hydrogen environment using a 4-foot dewer. The technology performed well in all three cases, demonstrating the ability to measure liquid to ¼ inch. </p><p><strong>Looking ahead</strong>: The team continues to push the fields of application with future tests to determine boundary layers between different fluids such as oil and water. Also there are planned opportunities to demonstrate the technology in a NASA-operated cryogenic test bed, simulating a cryogenic fuel management scenario.</p><p><strong><em>Benefits</em></strong></p><ul><li><strong>Precise</strong>: Can gauge liquid levels within a ¼-inch</li><li><strong>Simple</strong>: Requires just one fiber optic strand and one metallic wire, as opposed to conventional measurement systems, which require many more wires</li><li><strong>Safe</strong>: Is not susceptible to electromagnetic interference (EMI)</li><li><strong>Robust</strong>: Can be used in corrosive or toxic liquids without damaging the fiber or contaminating the liquid</li></ul><p><strong><em>Applications</em></strong></p><ul><li>Aerospace launch vehicles and satellites</li><li>Chemical and refinery plants</li><li>Industrial tanks</li></ul>

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