Active Clearance Control Using Fourth Stage Bleed Air
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Solution Overview
Problem
Existing methods for active clearance control in gas turbine engines, such as active thermal and mechanical control, face inefficiencies due to slow thermal response and added weight from mechanical equipment, which affect compressor performance and stability.
Innovation Solution
An active clearance control system that utilizes fourth stage compressor bleed air to cool the inner annular casing of a turbomachine, reducing thermal expansion and clearance between compressor blades and the casing, through a manifold and impingement system, thereby enhancing thermal response and reducing mechanical parts and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If active thermal control methods use compressor bleed air and fan exhaust air to cool the inner compressor casing, then the clearance between compressor blade tips and the inner compressor casing is maintained, but the thermal response is slow
Solution Approach 1:
The patent applies local quality by using fourth stage compressor bleed air specifically at the location where thermal response is most critical. The system directs cooler fourth stage bleed air to the inner compressor casing through a dedicated cooling system, creating a localized cooling zone that achieves faster thermal response compared to using warmer fan exhaust air or later stage bleed air.
Solution Approach 2:
The patent changes the temperature parameter of the cooling air by selecting fourth stage bleed air, which is inherently cooler than fan exhaust air or later stage bleed air. This parameter change (using cooler air from an earlier compression stage) directly improves the thermal response speed of the inner compressor casing cooling system.
2Speed
If active mechanical control methods use linkages and actuators to control the clearance between compressor blade tips and the inner compressor casing, then the response rate is quick, but the additional equipment adds weight to the aircraft
Solution Approach 1:
The patent replaces the mechanical control system (linkages, actuators, segmented shrouds) with a thermal control system that uses air flow management. Instead of mechanically adjusting the casing position, the system uses fourth stage bleed air cooling to control thermal expansion and maintain clearance. This substitution eliminates heavy mechanical components while achieving comparable or improved response rates through thermal management.
Solution Approach 2:
The patent extracts and removes the heavy mechanical control equipment (actuators, linkages, segmented shroud systems) from the engine design. By eliminating these mechanical components and relying solely on thermal control using air flow, the system reduces aircraft weight while maintaining effective clearance control functionality.
3Speed
If active mechanical control methods use segmented shrouds and actuators to control clearance, then the response rate is quick, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical control systems with a simplified thermal control approach. Instead of using segmented shrouds, linkages, and multiple actuators, the system uses air flow management through the cooling system to control clearance. This substitution significantly reduces device complexity while maintaining quick response rates through effective thermal management.
Solution Approach 2:
The patent makes the fourth stage bleed air cooling system serve multiple functions: it cools the inner compressor casing to control thermal expansion, maintains blade tip clearance, and provides a simplified control mechanism. This multi-functionality eliminates the need for separate mechanical clearance control systems, reducing overall device complexity.
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 achieves quicker thermal response and reduced weight by using cooler fourth stage bleed air to control clearance, improving engine performance and stability without the need for additional mechanical components.
Implementation Method 1
The plurality of conduits is configured to channel a flow of cooling fluid to the impingement system. The impingement system is configured to channel the flow of cooling fluid to the radially outer surface of the inner annular casing
Implementation Method 2
cooling fluid to the radially outer surface of the inner annular casing, thereby cooling the radially outer surface of the inner annular casing
Data Source
AI summary
The turbomachine includes a compressor, an inner annular casing, and an outer annular casing. The inner annular casing and the outer annular casing define at least one cavity therebetween. The clearance control system includes a manifold system including at least one conduit disposed within the cavities and configured to channel a flow of cooling fluid between the cavities. The clearance control system also includes an impingement system including a header and at least one plenum configured to channel the flow of cooling fluid to the inner annular casing. The conduits configured to channel the flow of cooling fluid to the impingement system. The clearance control system further includes a channel system including at least one channels configured to channel the flow of cooling fluid to the turbomachine. The channels are configured to control the flow of cooling fluid to the manifold system.