Patent ID: 8662820

Claim:
A method of reducing steam flow during a shutdown phase of a turbomachine, the method comprising: a. providing a turbomachine comprising at least a first section and a second section, and a rotor partially disposed within the first section and the second section; b. providing a first valve configured for controlling steam flow into the first section; and a second valve configured for controlling steam flow into the second section; c. determining whether the turbomachine is operating in a shutdown phase; which begins when a load on the turbomachine is reduced and steam flow into each section is gradually stopped and the rotor is slowed to a turning gear speed; d. determining an allowable turbine operating space (ATOS) which approximates operational boundaries for each section of the turbomachine, wherein ATOS incorporates data from at least one of the following: steam flow through each section, a thrust limit of each section, and an exhaust windage limit; e. determining an allowable range within ATOS of a physical parameter associated with the shutdown phase; f. modulating the first valve to reduce steam flow entering the first section, wherein the modulation is partially limited, by the allowable range of the physical parameter; g. modulating the second valve to reduce steam flow entering the second section, wherein the modulation is partially limited by the allowable range of the physical parameter; and h. wherein ATOS, in real time, expands operational boundaries of the first section and the second section, and allows unbalanced steam flow between the first section and the second section of the turbomachine during the shutdown phase.