Abstract
The fuel (liquid hydrogen) turbo-pump (FIP) of the LE-7A engine, the first stage main engine of H-IIA launch vehicles, has been attended, from the outset of development, with problems of excessive sub-synchronous whirl vibration. Test data indicate system damping of the rotor system becomes nearly zero and actions of the rotor system readily respond to external random force. The outstanding reduction in system damping was shown due primary to Thomas force induced by the high power turbine. It was generated by torque difference, depending on tip clearance distribution of rotating turbine blades. For estimation of blade force, CFD was used to predict flow in the turbine. The present study was conducted so as to find means for augmenting damping. Determination was made of seal characteristics and system damping was evaluated. It was estimated that the rotor system could become sufficiently stable by injecting seal fluid in a counter rotating direction. Hot firing test data indicate the vibration was sufficiently suppressed using this seal.
