Gas Turbine Load Variation Control via Stator Vanes and Anti-Surge Valves
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Solution Overview
Problem
Gas turbines face challenges in managing sudden load disconnections and reductions, particularly in double shaft types, due to low mechanical inertia, which can lead to excessive rotation and combustion issues during supply disconnection or sudden load reductions.
Innovation Solution
A method that reduces gaseous fuel flow to a minimum, activates a selective burner feeding sequence, modifies adjustable stator vane angulation, and opens anti-surge and overboard bleeds to control compressor air flow, thereby managing load variations and preventing high rotation regimes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the turbine operates with low mechanical inertia (double shaft type), then the response speed to load changes is improved, but the rotation regime becomes excessively high during supply disconnection
Solution Approach 1:
The control method activates preliminary actions by detecting the supply disconnection condition and immediately initiating a sequence of control operations including reducing fuel flow, modifying stator vane angulation, and opening anti-surge valves before the excessive rotation regime is fully developed, thereby preventing the harmful effect in advance
Solution Approach 2:
The method employs feedback control by continuously monitoring the rotation regime and supply connection status, and adjusting the fuel flow, stator vane positions, and valve openings based on the detected conditions to maintain reliable operation despite the low inertia characteristic
2Reliability
If the rotation regime is rapidly reduced during load rejection, then the harmful effect of excessive rotation is prevented, but combustion malfunctions occur
Solution Approach 1:
The control method segments the load rejection process into distinct phases: initial fuel flow reduction, selective burner feeding sequence activation, stator vane angulation modification, and anti-surge valve opening. This segmentation allows each parameter to be adjusted in a controlled manner, preventing combustion malfunctions while achieving rotation control
Solution Approach 2:
The method dynamically adjusts multiple parameters (fuel flow rate, burner feeding sequence, stator vane angles, valve positions) in a coordinated manner during the load rejection process, allowing the system to adapt to changing conditions and maintain stable combustion while controlling the rotation regime
3Speed
If the fuel flow is reduced to minimum value, then the turbine speed is controlled, but the combustion stability deteriorates
Solution Approach 1:
The control method implements preliminary action by activating a selective burner feeding sequence before completely reducing fuel flow to minimum values. This ensures that combustion is maintained in a controlled manner during the speed reduction process, preventing combustion instability
Solution Approach 2:
The method applies local quality by selectively controlling which burners receive fuel during the load rejection process. Instead of uniformly reducing fuel to all burners, the selective feeding sequence maintains adequate fuel supply to specific burners, preserving combustion stability while achieving overall turbine speed control
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
The method effectively reduces turbine speed and manages load rejection procedures without causing combustion malfunctions, ensuring stable operation during supply disconnections and partial load reductions.
Implementation Method 1
modifying the angulation of said plurality of adjustable stator vanes in order to reduce the speed rate of said compressor
Implementation Method 2
opening said one or more anti-surge valves and said one or more overboard bleeds in order to reduce the air flow at the inlet of said combustor
Implementation Method 3
a combustor, in which the combustion takes place of gaseous fuel added to the compressed air
Data Source
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AI summary
A method is described for controlling load variations in a gas turbine. The method comprises reducing the flow of gaseous fuel entering the combustor to a predefined minimum value, if an increase is observed in the rotation regime of said turbine above a predefined maximum value and a total reduction in the load, activating a selective feeding sequence of the burners if the turbine is operating in normal functioning or premixed flame mode, modifying the angulation of the adjustable stator vanes, in order to reduce the speed rate of the compressor, and opening one or more anti-surge valves and one or more overboard bleeds, in order to reduce the air flow at the inlet of the combustor.