Development of Hydrodynamic Mechanical Face Seal for Aircraft Engine Gearboxes With Gas–Liquid Hybrid Lubrication

Abstract In high-speed rotating equipment such as turbomachinery, low-loss, low-wear, and low-leakage sealing technology is needed to achieve higher efficiency, longer service life, and lower environmental impact. The authors have proposed a hydrodynamic mechanical face seal based on “gas–liquid hybrid lubrication” technology, which maintains a noncontacting gap between sliding surfaces from very low speed rotation immediately after startup to very high speed rotation, and are investigating its application to various high-speed rotating equipment. The gas–liquid hybrid lubrication technology is a new technology that uses liquid hydrodynamic lubrication to maintain a noncontacting state at very low speeds during startup and stop and automatically transitions to gas lubrication at high speeds and operates with lower losses compared to liquid lubrication. Numerical analysis has shown the lubrication characteristics of this seal. Then rotating tests were conducted to evaluate the sliding surface temperature of the new technology in comparison with conventional seals, simulating the environment of an aircraft gearbox. The results indicated that the sliding surface temperature did not increase from low-speed to high-speed rotation, and it was also experimentally confirmed that the seals operated stably and without contact. Furthermore, no leakage was observed, and good sealing characteristics were confirmed. These results demonstrate the feasibility of a seal that achieves low loss, long life, and low leakage when applied to aircraft gearboxes.