Gas Turbine Load Reduction Control via Fuel-Air Ratio Management
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Solution Overview
Problem
Existing technologies fail to maintain gas turbine operation during load reduction without causing compressor surges or accidental fires, which hampers quick recovery from abnormalities and missed power generation opportunities.
Innovation Solution
A control device that calculates fuel flow rate commands through feedback control and load decreasing control, adjusting air suction rates to maintain a fuel-air ratio within a predetermined range, allowing for rapid output reduction while preventing surges and fires, by synchronizing fuel and air flow rate reductions within 2 to 5 seconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the air-suctioning amount of the compressor is reduced quickly to decrease load, then the output reduction speed increases, but the compressor may experience surge
Solution Approach 1:
The control device performs preliminary action by reducing the fuel flow rate command value before reducing the air suction flow rate. This sequential approach ensures that the fuel-air ratio remains within a safe range during the transition, preventing compressor surge while achieving rapid load reduction. The fuel reduction is completed first (within 2-5 seconds), creating a buffer that allows subsequent air flow reduction without causing instability.
2Speed
If the fuel flow rate is reduced quickly to decrease load, then the output reduction speed increases, but accidental fire may occur in the combustor
Solution Approach 1:
The control device performs preliminary action by reducing the fuel flow rate command value first, before reducing the air suction flow rate. This ensures that the fuel-air ratio remains within a predetermined safe range throughout the load reduction process, preventing accidental fire in the combustor while achieving rapid output reduction.
Solution Approach 2:
The control device uses feedback control to monitor the actual fuel-air ratio during the load reduction process and adjusts the fuel flow rate command value accordingly. This feedback mechanism ensures that the fuel-air ratio stays within the predetermined safe range, preventing accidental fire while maintaining rapid response capability.
3Reliability
If load shutoff is performed to ensure safety during abnormality, then the gas turbine stops, but power generation opportunity is lost
Solution Approach 1:
The control device changes operating parameters by reducing the fuel flow rate command value to a predetermined level and maintaining the fuel-air ratio within a specific range. This parameter adjustment allows the gas turbine to continue operating in a safe manner during abnormalities, avoiding complete shutdown while ensuring safety through controlled parameter modification.
Data Source
AI summary
A control device selects and executes any of normal control of outputting a fuel flow rate command value through feedback control based on a deviation between a target output and an actual output of a gas turbine and load decreasing control of outputting the fuel flow rate command value for reducing an output of the gas turbine to a predetermined target output during a predetermined first time without performing feedback control, and performs control of reducing a flow rate of air flowing into a compressor of the gas turbine such that an air-fuel ratio settles within a predetermined range, in parallel with execution of the load decreasing control when the load decreasing control is selected.