Active retractable seal for turbo machinery and related method

A retractable seal assembly for use between a turbine stator and a turbine rotor component of a turbine, the seal assembly comprising:

• a plurality of seal rings mounted to said turbine stator, each ring having at least two arcuate seal segments movable toward and away from said turbine rotor between respective closed and open positions as a function of pressure drop in a fluid flowing axially along said rotor;
• and
• a fluid bypass circuit for directing fluid around one or more of said plurality of seal rings to thereby reduce the pressure drop across said one or more of said seal rings;
• wherein said fluid bypass circuit includes a conduit extending from an inlet at a location upstream of said at least one seal ring and terminating at an outlet location downstream of said at least one seal ring, and wherein a bypass control valve is located in said fluid bypass circuit, between said inlet and said outlet, said control valve enabling active control of pressure drop across said at least one seal ring such that said at least one seal ring can be moved via said one or more actuators_to said open position during operation and under any operating condition of the turbomachinery.