Gas Turbine Casing Indentations Tip Clearance Flow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Tip clearance flow between rotor blade tips and stationary casings in gas turbine engines leads to performance and stability losses due to temporary and permanent increases in clearance size, affecting fuel consumption and surge margin.
Innovation Solution
An annular casing with shallow, circumferential indentations of a depth matching the tip clearance, positioned between the leading and trailing edges of airfoils, reduces double tip leakage and minimizes sensitivity to tip clearance size by partially blocking upstream flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If tip clearance is reduced to improve aerodynamic performance, then fuel consumption improves, but manufacturing precision requirements increase and wear over time becomes more detrimental
Solution Approach 1:
The patent applies local quality by creating indentations at specific locations on the casing inner surface where tip clearance flow occurs. These localized modifications alter the flow characteristics only in the critical regions between blade tips and casing, without requiring precision control of the entire tip clearance gap. The indentations are positioned axially between projections of leading and trailing edges of airfoils onto the inner surface, creating localized flow control that reduces sensitivity to overall clearance variations.
Solution Approach 2:
The patent implements preliminary action by pre-forming indentations in the casing during manufacturing, before the engine operates and wear occurs. These pre-formed indentations are designed to compensate for future wear and clearance increases, ensuring that the casing maintains effective flow control even as the tip clearance grows over the engine's operational life. The indentations are created with depths of an order of magnitude of the clearance between rotor and stator.
2Stability of the object's composition
If tip clearance is reduced to improve stability, then surge margin improves, but the complexity of maintaining clearance increases
Solution Approach 1:
The indentations create local flow control features that stabilize the tip clearance flow without requiring complex active control systems. By modifying the casing geometry locally at the indentation sites, the patent achieves improved surge margin through passive geometric features rather than active clearance adjustment mechanisms.
3Loss of energy
If shallow indentations are added to reduce tip leakage, then aerodynamic performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by introducing indentations only in specific axial regions where tip clearance flow occurs, rather than modifying the entire casing surface. The indentations are confined to regions between projections of leading and trailing edges of airfoils, creating localized flow control with minimal impact on overall casing structure and manufacturing complexity.
Solution Approach 2:
The patent uses partial action by implementing shallow indentations with depths of an order of magnitude of the clearance, which is sufficient to control tip leakage without requiring deep or extensive modifications. This partial modification achieves the desired flow control while keeping manufacturing complexity manageable.
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 solution reduces the sensitivity of aerodynamic performance and stability to tip clearance size, increasing the stall/surge margin and maintaining robust engine performance even with increased tip clearance, while avoiding significant weight increase and manufacturing complexity.
Implementation Method 1
The plurality of indentations being defined in a region of the inner face defined axially between projections of leading and trailing edges of the airfoils onto the inner surface of the annular body
Data Source
AI summary
A gas turbine engine shroud for surrounding one of a rotor and a stator having a plurality of radially extending airfoils is provided. The shroud includes an annular body defining an axial and a radial direction. The body has a radially inner surface and a plurality of indentations is annularly defined therein. Each of the plurality of indentations has a depth of an order of magnitude of a clearance between the one of the rotor and the stator and the inner surface. The plurality of indentations is defined in a region of the inner face defined axially between projections of leading and trailing edges of the airfoils onto the inner surface of the annular body.