Axial Thrust Foil Air Bearing with Integrated Load Sensor
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Solution Overview
Problem
Small gas turbine engines for UAVs face challenges in supporting high-speed rotors due to the limitations of roller bearings, which are not suitable at speeds over 70,000 rpm, and traditional lubrication systems are weight and space-intensive, making dry foil air bearings necessary but inefficient at high speeds.
Innovation Solution
The implementation of radial and axial foil air bearings with integrated axial thrust load sensors using strain gages connected to a circuit for active thrust management, allowing for modulation of cooling air flow pressure to maintain thrust balance and accommodate axial thrust loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If roller bearings with lubrication system are used, then load carrying capacity is improved, but weight and device complexity increase significantly
Solution Approach 1:
The patent removes the lubrication system (reservoir, pump, pipes) from the bearing system, extracting only the essential load-carrying function. This is achieved by using foil air bearings that operate without lubricant, eliminating the weight penalty while maintaining bearing functionality through a different physical mechanism (air film support).
Solution Approach 2:
The patent employs air bearings that use compressed air to create a load-supporting film between the rotor and stator. This pneumatic approach replaces the traditional mechanical lubrication system, providing load carrying capacity through gas pressure rather than liquid lubricant, thereby reducing weight and complexity.
2Force
If roller bearings with lubrication system are used, then load carrying capacity is improved, but device complexity increases due to lubricant reservoir, pump, and pipes
Solution Approach 1:
The patent extracts and removes the entire lubrication subsystem (reservoir, pump, piping infrastructure) from the engine architecture. The bearing system is simplified to only the essential elements needed for air film generation and load support, dramatically reducing device complexity while maintaining load-carrying capability through the air bearing mechanism.
Solution Approach 2:
The air bearing system is self-sufficient, requiring no external lubrication infrastructure. The compressed air supply serves multiple functions (cooling and load support), and the bearing surfaces are self-lubricating through the air film, eliminating the need for separate lubricant delivery and return systems.
3Weight of moving object
If foil air bearings are used, then weight is reduced, but reliability deteriorates at speeds over 70,000 rpm
Solution Approach 1:
The patent employs active thrust management that dynamically adjusts cooling air flow based on real-time thrust sensor feedback. This dynamic control system adapts the air bearing operating conditions to match the actual load and speed conditions, maintaining stable operation and reliability across the full operating range including high-speed conditions over 70,000 rpm.
Solution Approach 2:
The patent incorporates thrust sensors that provide real-time feedback on axial load conditions to the thrust management system. This feedback loop enables the system to actively adjust cooling air flow and bearing parameters to maintain optimal performance and reliability, preventing instability that would otherwise occur at high speeds with passive air bearing designs.
4Stability of the object's composition
If active thrust management with sensors is implemented, then operational stability is improved, but device complexity increases
Solution Approach 1:
The thrust sensors serve multiple functions: they measure axial load for control purposes, provide diagnostic information about bearing condition, and enable both active thrust management and condition monitoring. This multi-functionality justifies the added complexity by providing operational stability benefits across multiple system aspects simultaneously.
Solution Approach 2:
The thrust sensors provide real-time feedback on axial load conditions to the thrust management system, enabling active adjustment of cooling air flow and bearing parameters. This feedback mechanism maintains operational stability by continuously adapting the bearing operation to match actual thrust conditions, preventing instability that would occur with passive designs.
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 enables efficient thrust management and balancing in small gas turbine engines, reducing weight and space requirements while maintaining operational stability at high speeds by directly measuring thrust loads and adjusting cooling air flow, thereby enhancing performance and reliability.
Implementation Method 1
an axial thrust load sensor with strain gages connected by wires to a circuit for strain gage measurement
Implementation Method 2
Compressor bleed air is used to cool a bearing
Implementation Method 3
the rotor is supported by radial and axial foil air bearings
Data Source
AI summary
An axial thrust load sensor for an axial thrust foil bearing used in a small gas turbine engine, the axial thrust load sensor having a axial thrust foil bearing plate and an intermediate washer plate and a load sensor plate arranged face to face to form the load sensor. The load sensor plate has three pedestals on a front side and three pedestals on a back side so that all six pedestals alternate at equal spacing. Next to each pedestal is a strain gauge connected to a controller. The controller regulates a supply of cooling air to the axial thrust bearing in order to control a thrust balance.