Suction-Based Active Clearance Control for Gas Turbines
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Solution Overview
Problem
Gas turbine engines face challenges in actively controlling radial clearances between rotors and shrouds due to the complexity and expense of existing systems that rely on complex manifold structures and valving for heating or cooling.
Innovation Solution
A suction-based active clearance control system using a valve located downstream of an active clearance control manifold, which utilizes fan bypass air to control turbine case temperature and clearance, eliminating the need for complex upstream valving and piping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex manifold structures and upstream valving are used to deliver heating or cooling air to the turbine case, then active clearance control is achieved, but system weight and expense increase
Solution Approach 1:
The patent inverts the conventional approach by placing the valve downstream of the manifold rather than upstream. This allows the manifold to remain simple and lightweight while the valve controls flow after it enters the turbine case, achieving active clearance control without the weight penalty of complex upstream valving and piping
Solution Approach 2:
The patent extracts the valve from the upstream portion of the system and relocates it downstream. This separation allows the manifold structure to be simplified and reduced in weight, while the valve performs its control function at a different location in the flow path
2Reliability
If complex manifold structures and piping are used to deliver bleed air to the turbine case, then active clearance control is achieved, but system complexity increases
Solution Approach 1:
By inverting the valve location to downstream, the patent eliminates the need for complex upstream piping and valving arrangements. The manifold becomes a simple distribution structure, and the single downstream valve provides all necessary flow control, significantly reducing system complexity
Solution Approach 2:
The patent extracts the complex valving function from the upstream manifold system and consolidates it into a single downstream valve. This separation simplifies the manifold and piping structure while maintaining full active clearance control capability
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 reduces the weight and expense of active clearance control systems while effectively managing tip clearances, minimizing the risk of blade rubs and optimizing engine efficiency across varying operating conditions.
Implementation Method 1
an annular manifold surrounding a portion of the outer surface of the turbine case... an inlet port in communication with the outer surface
Implementation Method 2
controls turbine case temperature and clearance... effectively managing tip clearances
Data Source
AI summary
A clearance control apparatus for a gas turbine engine including an annular turbine case having opposed inner and outer surfaces; an annular manifold surrounding a portion of the turbine case, the manifold including: an inlet port in fluid communication with the manifold and the outer surface of the turbine case, and an exit port; and a bypass pipe having an upstream end coupled to the exit port, a downstream end coupled to a low-pressure sink, and a valve disposed between upstream and downstream ends, the valve selectively moveable between a first position which blocks flow between the upstream and downstream ends, and a second position which permits flow between the upstream and downstream ends.