Compressor Casing Cooling Air Passage for Clearance Control
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Solution Overview
Problem
Gas turbine engines experience efficiency degradation at cruise conditions due to increased rotor tip and interstage seal clearances resulting from thermal contraction of compressor components, which are designed for minimal clearances during takeoff.
Innovation Solution
A system and method involving a cooling air passage within the compressor casing that selectively directs cooling air to control rotor tip and interstage seal clearances, using valves to activate cooling during cruise conditions and disable it during takeoff and other specific operational states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If compressor components are designed for minimal clearances during takeoff, then thrust production is enhanced, but efficiency degrades at cruise conditions due to higher clearances from thermal contraction
Solution Approach 1:
The patent applies parameter changes by actively modifying the temperature of the compressor casing through controlled cooling. During cruise conditions, cooling air is supplied to reduce the casing temperature, causing thermal contraction that decreases rotor tip clearance and interstage seal clearance. This dynamic parameter change allows the system to optimize clearance based on operational conditions, improving fuel efficiency during cruise while maintaining acceptable clearance during takeoff without active cooling
Solution Approach 2:
The invention implements dynamics by transitioning from a static clearance design to a dynamic clearance control system. The cooling air passage system allows the compressor casing temperature and dimensions to be actively adjusted during operation. Valves control the flow of cooling air to the casing, enabling real-time modification of clearance parameters based on flight conditions, thus optimizing performance across different operational regimes
2Loss of energy
If cooling air is supplied to reduce clearances during cruise, then fuel efficiency is enhanced, but system complexity increases due to cooling air passages and valves
Solution Approach 1:
The cooling air passage system serves multiple functions: it cools the compressor casing to reduce clearances for improved efficiency, and the same infrastructure can potentially serve other thermal management needs. The passage system is integrated into the existing compressor structure, utilizing available cooling air sources from the engine's air supply system, thus adding clearance control functionality without requiring entirely separate systems
Solution Approach 2:
The system utilizes cooling air that is already present in the engine's air supply system, drawing from existing pressure differentials and flow paths. The cooling effect is achieved passively through the thermal properties of the cooling air as it flows through the passages, without requiring additional active cooling mechanisms or complex control systems beyond simple valve actuation
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 system enhances fuel efficiency and maintains thrust production by reducing clearances during cruise, while allowing thermal expansion during takeoff, thus optimizing engine performance across different operational conditions.
Implementation Method 1
operating temperatures of the compressor stages are lower than at takeoff, resulting in higher clearances due to thermal contraction of the compressor components
Implementation Method 2
The rotor blades and compressor casing are subjected to a range of temperatures during various stages of operation such as ground operation, takeoff, and cruise, resulting in thermal expansion or contraction of these compressor components
Data Source
AI summary
A gas turbine engine clearance control system includes a cooling air passage extending from a cooling air inlet port to a cooling air outlet port. The cooling air inlet port and outlet port are formed within an external surface of a compressor casing of a compressor and are also axially spaced on the external surface of the compressor casing. The cooling air passage extends from the cooling air inlet port radially inwardly to at least one of a flange joint, a radially outer surface of a compressor casing ring, and a radially outer surface of a connector case. The cooling air passage further extends aftward along the radially outer surfaces of the connector case and the compressor casing ring. The cooling air passage further extends radially outward to the cooling air outlet port. Selectively supplying cooling air to the cooling air passage controls a rotor tip clearance between a rotor tip of a rotor blade of the compressor and an inner surface of the compressor casing ring and further controls an interstage seal clearance between an inner band and a rotor spool of the compressor.