Gas Turbine Cool-Down Clearance Control via Dynamic Cooling Air Flow
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Solution Overview
Problem
Gas turbines face efficiency losses due to clearance gaps between rotating and stationary parts, which increase with temperature variations and thermal expansion, leading to reduced performance and potential damage from rubbing during the cool-down phase.
Innovation Solution
A method of operating a gas turbine during the cool-down phase by adjusting the flow rate of cooling air to the turbine vane carrier based on temperature differences, using a higher flow rate when the carrier is cooler and a lower flow rate when it is hotter, to minimize clearance reduction and maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the cooling air flow rate is increased to cool the turbine vane carrier during the cool-down phase, then the turbine vane carrier temperature is reduced, but the clearance between rotor and stator increases due to thermal contraction, leading to increased leakage and reduced efficiency
Solution Approach 1:
The cooling air flow rate is dynamically adjusted based on the turbine vane carrier temperature and the temperature difference between the carrier and cooling air. The system transitions from a static cooling approach to a dynamic one where the flow rate varies with operating conditions, allowing optimization of both temperature control and clearance management during the cool-down phase
Solution Approach 2:
The invention changes the flow rate parameter of cooling air based on temperature conditions. By monitoring the turbine vane carrier temperature and cooling air temperature, the system adjusts the flow rate parameter to achieve optimal performance - reducing flow rate when the carrier is hotter than cooling air to minimize clearance increase, while still achieving adequate cooling
2Loss of energy
If the clearance gap between rotor and stator is minimized to reduce leakage, then efficiency increases, but the risk of rubbing between rotating and stationary parts increases during temperature variations
Solution Approach 1:
The system implements feedback control by continuously monitoring the turbine vane carrier temperature and cooling air temperature, then using this information to adjust the cooling air flow rate. This closed-loop approach allows the system to respond to changing thermal conditions and maintain optimal clearance, preventing both excessive leakage and rubbing risks
Solution Approach 2:
The invention applies preliminary cooling action during the cool-down phase by controlling the cooling air flow rate before the turbine reaches steady state. By proactively managing the thermal contraction process through controlled cooling, the system prepares the clearance conditions in advance to prevent rubbing while minimizing leakage
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 reduces the cooling rate of the turbine vane carrier, allowing for a decrease in clearance between blades and vanes, thereby increasing gas turbine performance and reducing leakage, while maintaining safety by controlling the turbine vane carrier temperature effectively and at a lower cost compared to active clearance control measures.
Implementation Method 1
feeding a flow of cooling air from the compressor to the turbine vane carrier
Implementation Method 2
These temperature variations can result in significant amounts of thermal expansion
Data Source
AI summary
The application describes a method of operating a gas turbine during a cool-down phase. The gas turbine provides a compressor, a combustor downstream of the compressor, and a turbine downstream of the combustor, with the turbine providing a turbine vane carrier. The method includes feeding a flow of cooling air from the compressor to the turbine vane carrier, measuring a temperature of the flow of cooling air and measuring a temperature of the turbine vane carrier. In the method, the flow of cooling air is fed at a first flow rate when the temperature of the turbine vane carrier is lower than the temperature of the cooling air, and the flow of cooling air is fed at a second flow rate when the temperature of the turbine vane carrier is higher than the temperature of the cooling air, wherein the first flow rate is higher than the second flow rate.