Gas Turbine Clearance Control Assembly Thermal Management
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Solution Overview
Problem
Gas turbine engines face efficiency losses due to leakage at blade tip gaps, requiring a balance between minimizing clearance to enhance efficiency and preventing blade tip rubbing, which can lead to damage.
Innovation Solution
A clearance control assembly that adjusts the radial clearance between rotor blades and the shroud by managing the thermal expansion mismatch through a system that includes a case, baffle, and conductive elements to optimize thermal time constants, allowing passive control of clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the radial blade tip clearance is made small to increase engine efficiency, then energy extraction efficiency improves, but the risk of blade tip rubbing against the shroud increases
Solution Approach 1:
The patent changes the thermal parameters of the shroud by introducing a cooling chamber that receives cooling fluid. This allows dynamic adjustment of the shroud's thermal state, enabling the clearance to be optimized for efficiency while preventing blade tip rubbing through active thermal management. The cooling fluid temperature and flow rate are adjusted to control the shroud expansion and maintain safe clearance.
Solution Approach 2:
The patent transitions from a static clearance design to a dynamic clearance control system. The shroud is equipped with an active cooling system that can adjust the clearance in real-time based on operating conditions. The cooling chamber allows the shroud to dynamically respond to thermal changes, maintaining optimal clearance across varying engine loads and speeds.
2Reliability
If the blade tip clearance is made large to prevent blade tip rubbing, then component reliability improves, but engine efficiency decreases due to combustion gas leakage
Solution Approach 1:
The patent applies parameter changes by controlling the thermal state of the shroud through the cooling chamber. By adjusting the cooling fluid parameters (temperature, pressure, flow rate), the shroud's thermal expansion is controlled, enabling the clearance to be kept small for efficiency while preventing blade tip contact through active cooling management.
Solution Approach 2:
The patent replaces passive mechanical clearance design with an active thermal management system. Instead of relying on fixed mechanical clearances, the system uses thermal control via the cooling chamber to dynamically adjust the shroud position, substituting mechanical design constraints with controllable thermal parameters.
3Loss of energy
If active clearance control systems are used to optimize blade tip clearance, then engine efficiency increases, but system complexity and potential failure points increase
Solution Approach 1:
The cooling chamber system operates passively in many cases, utilizing the engine's existing cooling infrastructure. The chamber allows the shroud to self-regulate its thermal state based on the cooling fluid flow, reducing the need for complex active control mechanisms while still achieving clearance optimization.
Solution Approach 2:
The cooling chamber serves multiple functions: it cools the shroud to control clearance, manages thermal stresses, and can adapt to various operating conditions. By integrating this multi-functional component into the existing engine cooling system, the patent avoids adding separate dedicated clearance control systems, thereby reducing overall complexity.
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 solution increases engine efficiency, reduces fuel consumption, and minimizes the risk of blade-shroud contact, while enabling passive control of clearance even if active systems fail.
Implementation Method 1
A baffle is positioned outward along a radial direction from the case to define a chamber therebetween... the pressure differential between the chamber and the outside environment causes the first seal and the second seal to remain engaged with the case
Implementation Method 2
The first seal and the second seal prevent gas leakage between the baffle and the case
Data Source
AI summary
A clearance control assembly for a gas turbine engine that defines an axial direction and a radial direction and includes a stage of rotor blades and a shroud hanger. The assembly includes a case configured to be positioned outward along the radial direction from the stage of rotor blades when installed in the gas turbine engine. The case is further configured to be engaged with the shroud hanger at a first location when installed in the gas turbine engine. The assembly also includes a baffle positioned outward along the radial direction from the case to define a chamber therebetween. The baffle has a forward end and an aft end. The forward end of the baffle is engaged with the case to form a first seal and the aft end of the baffle is engaged with the case to form a second seal. The baffle, the case, or both define an inlet to allow a fluid to enter the chamber and the case defines an outlet to allow the fluid to exit the chamber.