Segmented Impeller Axial Clearance Control
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Solution Overview
Problem
Conventional radial compressor impellers with asymmetric solid bores deflect axially under high centrifugal loads and temperature gradients, requiring larger clearances that reduce compressor efficiency during off-design operations.
Innovation Solution
A multi-piece hollow impeller design with first and second portions secured by a bonding material, featuring an interior cavity for cooling and a circumferential gap to allow axial movement, reducing stress and maintaining dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional asymmetric solid bore impeller is used, then the impeller structure is simple and strong, but the impeller tip deflects axially under high centrifugal loads and temperature gradients, requiring larger clearances that reduce compressor efficiency
Solution Approach 1:
The impeller is divided into multiple segments (first impeller portion, second impeller portion, third impeller portion) that can move independently relative to each other. The first and second portions are connected by a first joint allowing axial movement, while the second and third portions are connected by a second joint. This segmentation allows the impeller to accommodate thermal expansion and centrifugal deflection without compromising tip clearance control.
Solution Approach 2:
The impeller transitions from a rigid solid bore structure to a dynamic segmented structure with joints that allow controlled movement. The first and second joints enable the impeller segments to adjust their positions dynamically in response to centrifugal loads and temperature gradients, maintaining optimal tip clearance across varying operating conditions.
2Reliability
If larger clearances are provided to accommodate impeller deflection, then the impeller can operate across the entire range without contact, but the compressor efficiency is reduced during off-design point operation
Solution Approach 1:
The segmented impeller with movable joints dynamically adjusts its configuration based on operating conditions. During off-design operation, the joints allow the impeller segments to shift positions that maintain smaller optimal clearances, thereby preserving compressor efficiency while still preventing contact across the entire operating range.
Solution Approach 2:
The impeller's effective geometry changes dynamically through the movement of segments at the joints. This parameter change allows the impeller to adapt its tip position and clearance characteristics to match different operating conditions, optimizing efficiency during off-design operation while maintaining reliability across the full range.
3Manufacturing precision
If a multi-piece hollow impeller with segmented portions is used, then axial tip clearance and alignment are improved throughout the operating range, but the impeller structure becomes more complex
Solution Approach 1:
The impeller is segmented into three portions connected by joints, which enables precise control of axial tip clearance through the controlled movement at each joint. This segmentation allows the complex clearance control requirement to be achieved through modular, manageable components rather than a monolithic structure.
Solution Approach 2:
The joints are strategically positioned to provide movement freedom only where needed for clearance control, while other portions of the impeller maintain rigid structural integrity. This localized flexibility at the joints achieves the desired clearance control without requiring the entire impeller structure to be complex or flexible.
4Ease of manufacture
If the impeller is designed as a single solid piece, then manufacturing is simpler, but the impeller cannot accommodate thermal gradients and centrifugal loads without deflection
Solution Approach 1:
The impeller is manufactured as separate segments that are subsequently assembled with joints. This approach maintains relative manufacturing simplicity for each segment while enabling the overall structure to accommodate thermal gradients and centrifugal loads through the controlled movement at the joints between segments.
Solution Approach 2:
The impeller employs a composite structure combining rigid segmental components with flexible joint connections. This composite design maintains the manufacturing advantages of simpler individual components while achieving the dimensional stability required to withstand thermal gradients and centrifugal loads through the coordinated behavior of the segmented structure.
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 design improves axial tip clearance and alignment throughout the compressor's operating range, enhancing efficiency and reducing the need for excessive clearances.
Implementation Method 1
The first and second impeller portions are secured to one another using a bonding material arranged near the tip of the impeller by a transient liquid phase process, for example
Implementation Method 2
inlet and outlet holes are provided on the impeller and arranged in communication with the inner cavity to provide a cooling flow there through
Implementation Method 3
The deflection is caused by centrifugal inertial loads on the asymmetric impeller and by temperature gradients in the impeller
Implementation Method 4
The deflection is caused by centrifugal inertial loads on the asymmetric impeller and by temperature gradients in the impeller
Data Source
AI summary
An impeller includes first and second impeller portions that are secured to one another. An interior cavity is formed between the first and second portions. The first impeller portion supports multiple blades. The first and second impeller portions respectively include first and second surfaces that are secured to one another near a tip of the impeller. Inlet and outlet apertures are provided in the impeller and are in communication with the inner cavity to provide a cooling flow path there through. A circumferential gap is arranged between the first and second impeller portions opposite the tip to permit relative axial movement between the first and second impeller portions during centrifugal loading of the impeller.