Hexagonal Pin for Turbine Disk Spacer Anti-Rotation
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Solution Overview
Problem
In axial compressors of turbine engines, the relative rotational movement between disks and spacers becomes unbalanced during hot shutdown due to differential cooling rates, causing the spacers to shift and potentially break the small cylindrical anti-rotation pins, leading to imbalances that require engine disassembly for reset.
Innovation Solution
A pin with a stem received within the recessed area of the disk and a hexagonally shaped head with flats received within the recessed area of the spacer, providing a secure engagement that restricts relative rotation through complementary surfaces, maintaining alignment and stability during thermal changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a small cylindrical anti-rotation pin is used to couple the spacer to the disk, then the device complexity is reduced, but the reliability deteriorates due to pin breakage during hot shutdown
Solution Approach 1:
The pin is segmented into two distinct parts: a cylindrical stem received by the disk and a hexagonal head received by the spacer. This segmentation allows each part to be optimized for its specific function - the stem provides rotational restraint while the hexagonal head prevents axial withdrawal, solving the reliability problem without increasing overall complexity
Solution Approach 2:
The pin design adds a dimensional aspect by using a hexagonal head configuration that engages with complementary surfaces in the spacer. This transforms the simple cylindrical pin into a multi-dimensional coupling solution that addresses both rotational and axial constraints simultaneously
2Temperature
If the spacer cools and shrinks at a higher rate than the disk during hot shutdown, then the thermal interference engagement is relieved, but the stability deteriorates allowing rotational shift
Solution Approach 1:
The pin is installed in advance during assembly, creating a preliminary mechanical constraint that prevents rotational movement. This preliminary action compensates for the future thermal contraction that would otherwise cause misalignment, maintaining stability throughout the thermal cycle
3Ease of operation
If the rotational inertia of the spacers breaks the pins, then the ease of operation is improved during assembly, but the loss of time increases due to engine disassembly for reset
Solution Approach 1:
The hexagonal head design provides beforehand cushioning by creating a mechanical lock that prevents the pin from breaking under rotational inertia loads. This prior cushioning measure eliminates the need for engine disassembly during maintenance, reducing downtime while maintaining assembly simplicity
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 pin design effectively reduces relative rotational movement and enhances the durability of the disk-spacer engagement, preventing pin breakage and maintaining engine balance without the need for disassembly during hot shutdowns.
Implementation Method 1
The head of the pin includes at least two flats corresponding to complementary surfaces of the recessed area of the spacer
Implementation Method 2
An interference engagement or, more particularly, a thermal interference engagement and a small cylindrical anti-rotation pin are used to couple each spacer to a corresponding disk
Data Source
AI summary
An axial compressor of a turbine engine includes a plurality of disk and spacer pairs oriented along a common axis of rotation. Each of a disk and a spacer of the disk and spacer pairs has a contacting face defining an engagement between the disk and the spacer. The contacting face of each of the disk and the spacer includes a recessed area. A pin has a stem received within the recessed area of the disk and a head received within the recessed area of the spacer. The head of the pin includes at least two flats corresponding to complementary surfaces of the recessed area of the spacer.