Turbomachine Accessory Gearbox Bracket Shear Interface
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Solution Overview
Problem
Mounting accessory gearboxes to turbomachines is challenging due to vibrations and the weight of the gearboxes, which complicates the process and can lead to relative movement between the gearbox components during operation.
Innovation Solution
A gearbox assembly that includes a housing structure, a shear bracket connected to a hanger via a thermal spray layer, which interfaces with the housing structure, providing increased friction and resisting relative movement between the shear bracket and the housing structure, and utilizing mechanical fasteners for securement, with the thermal spray layer composed of nickel and aluminum composite particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the accessory gearbox is mounted directly to the turbomachine case, then the mounting structure is simple, but vibrations cause relative movement between the gearbox and housing structure during operation
Solution Approach 1:
A shear bracket is introduced as an intermediary component between the accessory gearbox housing structure and the turbomachine case. The shear bracket includes a shear interface that intentionally allows controlled relative movement through a thermal spray layer, while maintaining overall mounting stability. This mediator absorbs vibrations and prevents direct rigid coupling that would cause harmful relative movement.
Solution Approach 2:
The interface between the shear bracket and housing structure uses a thermal spray layer that changes its friction parameters under different conditions. The thermal spray coating provides high friction when stationary to prevent movement, but allows controlled shear when vibration forces exceed the friction threshold, thereby managing stability dynamically.
2Strength
If heavier accessory gearboxes are used in land-based turbomachines, then the gearbox can handle higher loads, but the increased weight complicates mounting and increases inertial vibrations
Solution Approach 1:
The shear bracket design compensates for the weight of heavy land-based gearboxes by providing a compliant mounting interface. The thermal spray layer on the shear bracket creates a controlled friction interface that reduces the impact of inertial forces and vibrations generated by the heavy gearbox during operation, making the mounting process more manageable despite the increased weight.
3Strength
If mechanical fasteners are used to secure the shear bracket to the housing structure, then the connection is strong, but the thermal spray layer is needed to prevent relative movement under vibration
Solution Approach 1:
The interface combines mechanical fasteners with a thermal spray coating layer to create a composite connection system. The mechanical fasteners provide structural strength and positioning, while the thermal spray layer (composed of nickel and aluminum composite particles) provides friction-based stability and vibration damping, creating a multi-functional interface that addresses both strength and stability requirements.
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 thermal spray layer effectively increases friction between the shear bracket and the housing structure, reducing relative movement and enhancing the mounting stability of the accessory gearbox, thereby simplifying the mounting process and addressing vibration issues.
Implementation Method 1
a thermal spray layer between the shear bracket and the housing structure
Implementation Method 2
The thermal spray layer is a plasma spray layer
Data Source
AI summary
A gearbox assembly includes a housing structure, a shear bracket that connects the housing structure to a hanger to hold the housing structure relative to a turbomachine, and a thermal spray layer between the shear bracket and the housing structure.