Compressor Case Surface Features for Tip Clearance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in gas turbine engines is to maintain optimal tip clearance between the compressor blades and the casing, as variations in tip clearance due to thermal and centrifugal loads affect compressor efficiency and specific fuel consumption (SFC).
Innovation Solution
The compressor case is designed with surface features to enhance heat transfer and control flow velocities of cooling air, allowing for precise adjustment of tip clearance through thermal contraction and expansion management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tip clearance is reduced to improve compressor efficiency, then compressor efficiency improves, but blade tips may contact the casing causing rubbing
Solution Approach 1:
The patent changes the thermal state parameter of the casing by introducing cooling air flow to selectively cool specific regions of the casing. This thermal parameter change causes differential thermal contraction, allowing the casing to contract radially in controlled areas to reduce tip clearance without uniformly contracting the entire casing structure.
Solution Approach 2:
The patent applies thermal expansion principles in reverse (thermal contraction) by cooling the casing. The cooling air causes the casing material to contract thermally, reducing the radial distance between the casing inner surface and blade tips. This controlled thermal contraction allows tip clearance reduction while maintaining structural integrity.
2Manufacturing precision
If cooling air flow is increased to reduce tip clearance, then tip clearance control improves, but heat transfer efficiency may decrease due to laminar flow
Solution Approach 1:
The patent introduces circumferential ridges with curved surfaces into the casing cooling channels. These curved geometric features disrupt the laminar cooling air flow, creating turbulence that enhances heat transfer between the cooling air and casing. The curvature-induced turbulence allows effective heat removal without requiring excessive cooling air flow.
Solution Approach 2:
The patent uses circumferential ridges to mechanically disrupt the cooling air flow, creating flow turbulence and eddies. This mechanical disturbance of the flow pattern enhances convective heat transfer coefficients, allowing the cooling system to achieve better heat removal efficiency with reduced air flow rates.
3Loss of energy
If circumferential ridges are added to enhance heat transfer, then heat transfer coefficient improves, but device complexity increases
Solution Approach 1:
The patent incorporates circumferential ridges that create a ribbed, somewhat porous-like internal structure within the casing cooling channels. This structured geometry provides multiple flow paths and surface areas for heat transfer, enhancing thermal performance while maintaining a relatively simple overall casing design that can be manufactured using conventional techniques.
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 effectively maintains optimal tip clearance, improving compressor efficiency and reducing SFC by actively controlling the tip clearance in response to engine conditions.
Implementation Method 1
the casing also expands as it is heated but there is typically a mismatch in radial expansion between the disc/blades and the casing
Implementation Method 2
configuring case components to control flow velocities of cooling air and modifying surface features of the components to enhance heat transfer
Implementation Method 3
modifying surface features of the components to enhance heat transfer
Data Source
Figure 1
Figure 2
AI summary
A compressor case to blade tip clearance system comprising a rotor having blades with tips, the case including an inner case comprising at least one surface feature fluidly coupled to a distribution manifold disposed in a cooling air passageway, the at least one surface feature configured to interact with the cooling air, and a tip clearance located between the tips and the inner case; wherein the tip clearance is maintained responsive to a flow of the cooling air over the at least one surface feature.