Centrifugal Compressor Impeller Hub Forward Lean Design
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Solution Overview
Problem
Centrifugal compressor impellers in gas turbine engines face issues with axial tip deflections due to thinner back plate support, leading to increased tip clearance and poorer aerodynamic performance.
Innovation Solution
The impeller design features a hub surface with a forward lean configuration, forming an arch shape that provides additional mechanical structure to counteract axial tip deflections, with a varying orientation angle from 0° to greater than 90° and back, creating an axial recess to enhance support and reduce tip deflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the back plate support is made thinner to reduce weight and axial space, then the impeller weight and axial dimensions are reduced, but the support rigidity decreases leading to larger axial tip deflections
Solution Approach 1:
The hub surface is designed with a curved profile that leans forward toward the inlet, creating an arch-shaped structure. This curvature provides structural reinforcement to the thin back plate, reducing axial tip deflections while maintaining the weight and space benefits of a thinner design.
Solution Approach 2:
The solution introduces a new geometric dimension by varying the hub surface orientation angle along the axial direction. The hub surface angle transitions from acute (leaning forward) to obtuse (leaning backward), creating a three-dimensional arch structure that adds structural rigidity without increasing the two-dimensional footprint or weight.
2Length of moving object
If the back plate support is made thinner to reduce axial space, then the axial dimensions are reduced, but the support rigidity decreases leading to larger axial tip deflections
Solution Approach 1:
The curved arch profile of the hub surface provides structural reinforcement within the limited axial space. The forward lean creates a compressive arch structure that resists the centrifugal forces acting on the thin back plate, maintaining rigidity without requiring additional axial length.
Solution Approach 2:
By utilizing the radial and angular dimensions through the varying hub surface orientation, the design achieves structural reinforcement without extending the axial dimension. The arch structure leverages the third dimension (angular orientation) to provide stiffness in a space-constrained application.
3Reliability
If larger tip clearance is increased to accommodate larger tip deflections, then the impeller can tolerate more deflection, but the aerodynamic performance deteriorates
Solution Approach 1:
The forward-leaning hub surface creates preliminary structural support that counteracts the centrifugal forces before they can cause excessive tip deflection. This preventive structural reinforcement maintains tip clearance within optimal ranges, preserving aerodynamic performance while accommodating operational variations.
Solution Approach 2:
The hub surface orientation angle is varied as a design parameter, transitioning from acute to obtuse angles along the axial direction. This parameter change optimizes the structural support distribution, maintaining adequate tip clearance and aerodynamic performance across different operating conditions.
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 forward lean design reduces axial tip deflections, allowing for better clearance management and improved aerodynamic performance by increasing mechanical resistance and structural support for the vanes.
Implementation Method 1
The forward lean design reduces axial tip deflections, allowing for better clearance management and improved aerodynamic performance by increasing mechanical resistance and structural support for the vanes.
Data Source
AI summary
An impeller for increasing the pressure of a fluid circulating in an annular fluid path, the impeller comprising: a plurality of centrifugal compressor vanes circumferentially interspaced around the axis of the annular fluid path, the plurality of compressor vanes extending from an axially-oriented inlet to a radially-oriented outlet, and each having an inner edge and a free edge, the free edge of the plurality of compressor vanes coinciding with an outer limit of the annular fluid path, and a hub having a solid-of-revolution shape centered around an axis, the hub having an outer hub surface forming an inner limit to the annular fluid path and to which the inner edge of the plurality of centrifugal vanes is secured, the outer hub surface having a portion which leans forward, forming an axial recess therein.