Impeller Shroud Pneumatic Piston Clearance Control
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Solution Overview
Problem
Existing turbine engines with centrifugal compressors face inefficiencies due to rigid shroud mounting, which prevents adjustment of blade tip clearance, leading to increased leakage and potential rubs, and prior clearance control systems are cumbersome, heavy, and power-intensive.
Innovation Solution
A dynamically moveable impeller shroud assembly with an air piston system that uses high-pressure actuating air to axially deflect the shroud relative to the centrifugal compressor, maintaining radial alignment and allowing for precise control of blade tip clearance through sensors and pressure adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the shroud is rigidly mounted to the engine casing, then the structure is simple and reliable, but the blade tip clearance cannot be adjusted leading to increased leakage and reduced efficiency
Solution Approach 1:
The shroud is transformed from a rigid, fixed structure to a dynamically adjustable one through the introduction of a pneumatic piston system. The piston can extend or retract to move the shroud axially, allowing the blade tip clearance to be dynamically adjusted based on operating conditions while maintaining a relatively simple overall structure.
Solution Approach 2:
A pneumatic piston system is introduced to provide the actuation force for shroud movement. The piston uses pneumatic pressure to extend or retract, thereby adjusting the shroud position and blade tip clearance without requiring complex mechanical linkages or significant electrical power systems.
2Reliability
If the blade tip clearance is set to avoid rubs during highest clearance closure, then reliability is improved, but leakage increases and compressor efficiency decreases
Solution Approach 1:
The blade tip clearance is transformed from a static, fixed dimension to a dynamically adjustable parameter. The pneumatic piston system allows the clearance to be optimized for different operating conditions - reduced when efficiency is prioritized and increased when rub prevention is the concern - thereby resolving the contradiction between reliability and productivity.
Solution Approach 2:
The blade tip clearance parameter is made variable rather than fixed. By changing the clearance parameter dynamically through piston actuation, the system can optimize compressor efficiency under normal operation while maintaining reliability during transient conditions, eliminating the need to compromise efficiency permanently.
3Productivity
If prior clearance control systems are used to adjust blade tip clearance, then leakage is reduced and efficiency improves, but the systems are cumbersome, heavy, and power-intensive
Solution Approach 1:
The patent employs a pneumatic piston system that uses readily available pneumatic power sources in turbine engines to actuate the shroud. This approach avoids heavy mechanical linkages and complex electrical actuation systems, achieving clearance control with minimal added weight and power consumption while maintaining compressor efficiency.
Solution Approach 2:
The pneumatic piston system utilizes existing pneumatic resources within the turbine engine environment, effectively making the clearance control system self-sufficient without requiring external heavy-duty actuators or dedicated power sources. The system leverages the engine's own pneumatic infrastructure to achieve clearance adjustment.
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 leakage and improves compressor efficiency by dynamically adjusting blade tip clearance, eliminating the need for complex linkages and significant power, while allowing for efficient operation across various operating conditions.
Implementation Method 1
an air piston system that uses high-pressure actuating air to axially deflect the shroud relative to the centrifugal compressor
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A system for controlling the clearance distance between an impeller blade tip (213) of a centrifugal compressor (210) and a radially inner surface of an impeller shroud (220) in a turbine engine. The system comprises a high pressure air source (262), an air piston (264) mounted between an engine casing (231) and the shroud and adapted to receive high pressure air from the high pressure air source, a mounting arm (277, 278) coupling the shroud and air piston, and a slidable coupling (266) adapted to allow axial movement of the shroud and joining the shroud to an axial member.