Turbine Casing Tip Clearance Control via Impingement Cooling
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Solution Overview
Problem
Current methods for controlling tip clearance in gas turbine engines lack responsiveness during transient flight phases, leading to potential rubbing of turbine blades against the casing and inefficiencies due to mismatched radial expansion between the blades and the casing.
Innovation Solution
An arrangement involving inboard and outboard ducts with impingement holes on the turbine casing surface, using temperature control fluid to radially expand or contract the casing, ensuring minimal tip clearance through precise heating and cooling, with features like ribs and angled holes for enhanced heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tip clearance is set larger when the engine is cold to prevent blade rubbing, then the reliability is improved, but the productivity deteriorates due to increased specific fuel consumption
Solution Approach 1:
The patent applies dynamics by making the tip clearance adjustable rather than fixed. The system dynamically changes the clearance based on operating conditions (cold start vs. steady state) through controlled thermal expansion of the casing, allowing optimal clearance at each stage of operation
Solution Approach 2:
The patent changes the physical parameter of casing temperature to control tip clearance. By controlling the thermal expansion parameter of the casing through heated air passages, the system adjusts the radial dimension of the casing to maintain optimal clearance between blade tips and casing throughout operation
2Productivity
If the tip clearance is reduced to improve engine efficiency, then the productivity is improved, but the reliability deteriorates due to increased risk of blade rubbing
Solution Approach 1:
The system dynamically adjusts tip clearance based on operating conditions. During cold start, larger clearance prevents rubbing. During steady state, reduced clearance improves efficiency. The dynamic adjustment is achieved through controlled thermal expansion of the casing
Solution Approach 2:
The patent applies preliminary action by pre-heating the casing before the engine reaches steady state operation. This preliminary thermal expansion ensures the casing is in the correct dimensional state to maintain optimal clearance once the engine is running, preventing the need for larger clearance during efficient operation
3Productivity
If the casing is cooled to reduce radial expansion and maintain smaller tip clearance, then the productivity is improved, but the device complexity increases due to additional cooling ducts
Solution Approach 1:
The patent applies multi-functionality by using the same heated air passages for both cooling the casing during steady state operation and for other engine functions. The air passages serve dual purposes: controlling thermal expansion for clearance management and supporting overall engine thermal management
Solution Approach 2:
The system uses self-service by utilizing the engine's own hot air from the combustion process to heat the casing and control thermal expansion. Rather than requiring external cooling systems, the engine's inherent thermal energy is redirected to achieve the desired clearance control
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 maintains a minimal tip clearance during transient operations, enhancing engine efficiency by reducing specific fuel consumption (SFC) and preventing blade rubbing, with demonstrated reductions in tip clearance and improved SFC performance.
Implementation Method 1
the turbine 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
a flow of relatively hot cooling air is routed to the spacing cavity to provide cooling for the seal segments
Implementation Method 3
a flow of relatively hot cooling air is routed to the spacing cavity to provide cooling for the seal segments
Data Source
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AI summary
An arrangement for heating and cooling a turbine casing of a gas turbine engine, the arrangement comprising an inboard duct, adjacent to an inboard surface of the turbine casing, an outboard facing wall of the inboard duct having a plurality of impingement holes opening towards the inboard surface of the casing, through which temperature control fluid can pass from within the inboard duct to impinge upon the inboard surface of the turbine casing.