In-Line Air Sensor for Hydraulic Fluid

Air in aircraft hydraulic systems can cause cavitation, higher oil operating temperatures, oxidation, noisy operation, vibration, and changes in system natural frequency. To address this problem, the Air Force has developed purification systems to remove both free and dissolved air. The problem is that there is currently no sensor available for controlling the cart that can detect and quantify the amount of both free and dissolved air in the hydraulic fluid. Many approaches exist for detecting free air since it affects many bulk fluid properties. Dissolved air is much more difficult to detect and quantify, because it does not affect bulk fluid properties. We believe no sensor technology that monitors changes in bulk fluid properties will work here. Creare’s dissolved air sensor concept causes the dissolved air to temporarily come out of solution so that it can be detected and quantified in a similar manner as free air. Phase I will focus on developing and optimizing the dissolved air sensor and showing the appropriate relationships between the amount of dissolved air and the sensor output. Phase II will include the development of an integrated prototype that can be tested in existing purification carts.