Two-shaft Gas Turbine Compressor Degradation Control
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Solution Overview
Problem
In 2-shaft gas turbines, long-term use leads to decreased compressor efficiency due to airborne dust, causing increased NOx emissions when controlling rotating speeds to maintain constant compressor performance, as existing methods either reduce air volume or increase fuel flow, exacerbating NOx production.
Innovation Solution
A method for controlling the 2-shaft gas turbine that adjusts the inlet guide vane angle and fuel flow rate to maintain optimal compressor efficiency, using sensors to detect efficiency degradation and adjust target speeds to prevent excessive reduction in air flow, thereby stabilizing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the angle of the inlet guide vane is reduced to maintain constant rotating speed when compressor efficiency decreases, then the rotating speed can be kept constant, but the air volume of the compressor decreases leading to higher fuel concentration and increased NOx emission
Solution Approach 1:
The patent changes the control parameter from maintaining constant rotating speed to maintaining constant corrected rotating speed that accounts for compressor efficiency degradation. By introducing a correction factor based on compressor performance degradation, the system adjusts the target rotating speed to prevent excessive IGV angle reduction, thereby maintaining better fuel-to-air ratio and reducing NOx emissions while still keeping rotating speed relatively stable.
2Power
If fuel flow rate is increased to compensate for decreased air volume when controlling rotating speed, then the power output can be maintained, but the NOx emission increases further
Solution Approach 1:
The patent implements a feedback control mechanism where the actual rotating speed is continuously monitored and compared with the corrected target rotating speed. The control system uses this feedback to adjust the fuel flow rate and IGV angle in a coordinated manner, preventing excessive fuel injection that would occur with simple constant power control. This feedback loop ensures that fuel flow is optimized based on actual compressor performance, maintaining power output while limiting NOx formation by preventing overly rich fuel-to-air ratios.
3Measurement precision
If the angle of the inlet guide vane is reduced further to maintain rotating speed as compressor efficiency degrades, then the rotating speed control precision is improved, but the compressor performance decreases leading to even larger NOx emission
Solution Approach 1:
The patent introduces dynamic adjustment of the target rotating speed based on compressor efficiency degradation. Instead of using a fixed target speed, the system dynamically calculates a corrected target speed that compensates for compressor performance loss. This dynamic approach allows the system to maintain adequate rotating speed precision while avoiding excessive IGV angle reduction that would occur with static control, thereby preventing overly rich combustion and reducing NOx emissions.
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
This approach effectively suppresses NOx emissions by maintaining a balanced fuel-to-air ratio in the combustor, even with compressor efficiency degradation, ensuring reliable operation and reduced environmental impact.
Implementation Method 1
a compressor (1) that compresses air (100)
Implementation Method 2
at least one combustor (2) that burns fuel (200) with the compressed air (101)
Implementation Method 3
a turbine (3) that generates combustion gas (102) by burning the compressed air (101)
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A 2-shaft gas turbine is provided that can suppress an increase in NOx emission from a combustor (2) even when degradation of a compressor efficiency occurs due to decrease in performance with long-term use. The 2-shaft gas turbine having a gas generator (4) and a power turbine (5) includes: means for measuring control parameters of the compressor (1); and a controller (400) configured to set, in accordance with the degree of the degradation (Δη) of the compressor efficiency computed from the measured control parameters, a target speed (NB) of the gas generator at a level lower than a target speed (N0) in a state where degradation of the compressor efficiency has not occurred, and to control the rotating speed of the gas generator on the basis of a difference between the target speed (NB) thus set and an actual rotating speed (N1).