BACKGROUND

The disclosure relates generally to the operation of turbomachinery. More specifically, embodiments of the disclosure provide a methodology for controlling rotor stress within portions of a turbine system during a startup operation where a turbomachine may experience backpressure on or within a turbine element.

Power generation systems, also known as power plants, typically include a variety of different systems (e.g., turbomachine, generator, and/or other interconnected assemblies) that are used to generate a power output. Such power plants may include a power source (e.g., a turbomachine, solar panel, nuclear reactor, etc.), a prime mover (e.g., a rotatable shaft or similar element) for coupling the power source to an electric generator, and/or various components of the electric generator. For instance, a power generation system may include a gas turbine assembly having a compressor coupled to a gas turbine. The gas turbine in turn may be coupled to and drive a generator mounted on the same shaft. The generator produces a power output.

Power generation systems typically include a variety of different turbomachines and/or systems that are used to generate a power output. Examples of such power systems may include gas turbine systems and/or combined cycle power plants, which typically include one or more gas turbine systems. Conventional combined cycle power plants employ one or multiple gas turbine systems operatively coupled to one or multiple steam turbine systems. The gas turbine system includes a compressor coupled to a gas turbine. The gas turbine is usually coupled to and drives an external component, such as a generator, for producing a load or power output. The steam turbine system typically includes a high pressure (HP) turbine portion operatively coupled to an intermediate pressure (IP) turbine portion that, in turn, is coupled to a low pressure (LP) turbine. Similar to the gas turbine of the gas turbine system, the HP, IP and LP turbines are employed to drive an external component (e.g., generator).

In a typical combined cycle power plant, exhaust gas from the gas turbine is passed to a heat recovery steam generator (HRSG), which may be used to reheat and provide steam to the various turbine sections of the steam turbine system for enhanced efficiency of the system and/or power plant. Downstream of the HRSG the exhaust gas is released to the atmosphere through a stack. A technical challenge associated with steam turbine (ST) operation is assuring safe, reliable operation of the steam turbine components during startup, and maintaining various parameters within their targeted boundaries. Increases in temperature and pressure from their non-operational values throughout the turbine may affect the health and lifespan of ST components, in addition to affecting the power output from the ST system.

BRIEF DESCRIPTION

Aspects of the disclosure provide a method for controlling steam pressure within a turbine component during a startup operation, the turbine component being fluidly coupled between an inlet having an inlet valve for controlling steam flow into the turbine component and an exhaust having an exhaust valve for controlling steam flow to a discharge passage, the method including: adjusting the exhaust valve to a fully open position and the inlet valve to a fully closed position; calculating a predicted stress on a rotor of the turbine component based on a predicted steam flow with the inlet valve in a minimum load position, a rotor surface temperature, and an inlet steam temperature; determining whether the predicted stress exceeds a threshold; in response to the predicted stress exceeding the threshold, adjusting the inlet valve to a warming position that is less open than the minimum load position, such that a steam flow through the turbine component pressurizes the discharge passage; in response to steam in the discharge passage reaching a target pressure, partially closing the exhaust valve while maintaining the warming position of the inlet valve; determining whether a safety parameter of the turbine component violates a boundary, while maintaining the warming position of the inlet valve; in response to the safety parameter of the turbine component violating the boundary, partially opening the exhaust valve while maintaining the warming position of the inlet valve; recalculating the predicted stress on the rotor with the inlet valve in the warming position; and in response to the predicted stress not exceeding the threshold, opening the inlet valve to at least the minimum load position.

Further aspects of the disclosure provide a program product stored on a computer readable storage medium for controlling steam pressure within a turbine component during a startup operation, the turbine component being fluidly coupled between an inlet having an inlet valve for controlling steam flow into the turbine component and an exhaust having an exhaust valve for controlling steam flow to a discharge passage, the computer readable storage medium comprising program code for causing a computer system to perform actions including: adjusting the exhaust valve to a fully open position and the inlet valve to a fully closed position; calculating a predicted stress on a rotor of the turbine component based on a predicted steam flow with the inlet valve in a minimum load position, a rotor surface temperature, and an inlet steam temperature; determining whether the predicted stress exceeds a threshold; in response to the predicted stress exceeding the threshold, adjusting the inlet valve to a warming position that is less open than the minimum load position, such that a steam flow through the turbine component pressurizes the discharge passage; in response to steam in the discharge passage reaching a target pressure, partially closing the exhaust valve while maintaining the warming position of the inlet valve; determining whether a safety parameter of the turbine component violates a boundary, while maintaining the warming position of the inlet valve; in response to the safety parameter of the turbine component violating the boundary, partially opening the exhaust valve while maintaining the warming position of the inlet valve; recalculating the predicted stress on the rotor with the inlet valve in the warming position; and in response to the predicted stress not exceeding the threshold, opening the inlet valve to at least the minimum load position.

Additional aspects of the disclosure provide a turbine system including: a turbine component fluidly coupled between an inlet having an inlet valve for controlling steam flow into the turbine component and an exhaust having an exhaust valve for controlling steam flow to a discharge passage; a control system operatively coupled to the inlet valve and the exhaust valve of the turbine component, wherein the control system performs actions including: adjust the exhaust valve to a fully open position and the inlet valve to a fully closed position; calculate a predicted stress on a rotor of the turbine component based on a predicted steam flow with the inlet valve in a minimum load position, a rotor surface temperature, and an inlet steam temperature; determine whether the predicted stress exceeds a threshold; in response to the predicted stress exceeding the threshold, adjust the inlet valve to a warming position that is less open than the minimum load position, such that a steam flow through the turbine component pressurizes the discharge passage; in response to steam in the discharge passage reaching a target pressure, partially close the exhaust valve while maintaining the warming position of the inlet valve; determine whether a safety parameter of the turbine component violates a boundary, while maintaining the warming position of the inlet valve; in response to the safety parameter of the turbine component violating the boundary, partially open the exhaust valve while maintaining the warming position of the inlet valve; recalculate the predicted stress on the rotor with the inlet valve in the warming position; and in response to the predicted stress not exceeding the threshold, open the inlet valve to at least the minimum load position.

The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.

