Combined Cycle Plant Start-Up Control for Steam Turbine Thermal Stress
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Solution Overview
Problem
The challenge in the power generation industry is to shorten the time from gas turbine start-up to reaching rated output while minimizing thermal stress in the steam turbine.
Innovation Solution
A method and control program to manage the steam flow rate into the steam turbine based on output and thermal stress, allowing the gas turbine to reach rated output quickly without excessive thermal stress by controlling steam turbine input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the gas turbine output is rapidly increased to the rated output, then the start-up time is shortened, but high thermal stress is generated in the steam turbine
Solution Approach 1:
The patent applies dynamics by making the steam flow rate control adaptive and variable rather than fixed. The control device dynamically adjusts the steam flow rate based on real-time monitoring of thermal stress conditions in the steam turbine, allowing the system to transition from conservative low-flow conditions to optimized higher-flow conditions as the turbine warms up and can tolerate increased thermal stress, thereby reducing overall start-up time while protecting against excessive stress
Solution Approach 2:
The patent changes the parameter of steam flow rate from a static predetermined value to a dynamically adjustable parameter based on thermal stress measurements. By monitoring thermal stress levels and adjusting the steam flow rate parameter accordingly, the system optimizes the balance between rapid start-up and thermal stress protection, allowing faster start-up than traditional methods while preventing excessive thermal stress damage
2Stress or pressure
If the gas turbine output is maintained at initial output lower than rated output, then thermal stress in steam turbine is reduced, but start-up time is extended
Solution Approach 1:
The patent implements feedback control by continuously monitoring thermal stress levels in the steam turbine and using this information to adjust the steam flow rate. The control device receives thermal stress data from sensors and automatically modifies the steam flow rate to maintain optimal conditions, creating a closed-loop system that adapts to real-time turbine conditions rather than following a predetermined fixed schedule
Solution Approach 2:
The steam turbine essentially serves itself by providing thermal stress feedback that the control device uses to determine appropriate steam flow rates. The turbine's own thermal state information is used to control its own steam supply, allowing the system to self-regulate and optimize performance without external intervention or conservative predetermined limits
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid gas turbine output attainment with reduced thermal stress in the steam turbine, thus shortening the start-up time.
Implementation Method 1
a waste heat recovery boiler that generates steam by using heat from exhaust gas exhausted from the gas turbine
Implementation Method 2
a steam turbine driven by the steam from the waste heat recovery boiler, a condenser that returns the steam exhausted from the steam turbine to water, and an ST generator that generates electricity by drive of the steam turbine
Data Source
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AI summary
Provided is a combined cycle plant start-up method in which the following steps are executed: a gas turbine start-up step in which the output of a gas turbine is increased to the rated output; a ventilation step in which the supply of steam from an exhaust heat recovery boiler to a steam turbine is started when the temperature of the steam becomes equal to or greater than a preset temperature; and an ST output control step in which after connecting a generator, the flow rate of steam flowing into the steam turbine is controlled so that the output of the generator increases in accordance with a target output change pattern. When the thermal stress becomes equal to our greater than a preset first thermal stress in the ST output control step, the flow rate of steam flowing into the steam turbine is controlled so that the change in the output of the generator becomes smaller than the change indicated by the target output change pattern.