On-Wing Thrust Measurement Using Strain Gauges and Temperature Compensation
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Solution Overview
Problem
Current methods for on-wing thrust measurement of aircraft engines are inaccurate, with errors ranging from ±3 to ±5%, and cannot detect performance-reducing wear effects in real flight conditions, leading to overdimensioning and increased costs.
Innovation Solution
The method involves using strain gauges and temperature sensors on the engine mount's force transferring elements to determine strain and temperature, compensating for both static and transient temperature effects to accurately calculate the thrust force, enabling direct measurement of the physically transferred thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used for thrust measurement, then measurement capability is provided, but temperature effects cause measurement errors
Solution Approach 1:
A heat-conductive element is introduced as an intermediary between the engine mount and the strain gauges. This element has high thermal conductivity to equalize temperature across the strain gauge locations, while being thermally isolated from the engine mount to prevent heat transfer from the engine. The intermediary thus mediates between the heat source and the sensitive measurement devices, creating uniform thermal conditions for accurate measurement.
Solution Approach 2:
The heat-conductive element serves itself by using its high thermal conductivity property to automatically equalize temperature differences across the strain gauge locations. No external control or adjustment is needed - the physical property of the material itself provides the temperature equalization function, making the system self-regulating.
2Reliability
If engine is overdimensioned to compensate for wear, then certified thrust is maintained, but weight and costs increase
Solution Approach 1:
The measurement system provides continuous feedback on the actual thrust produced by the engine during flight. This real-time data allows operators to monitor engine performance and detect wear effects as they occur. With accurate feedback, the engine can be operated at optimal levels without excessive overdimensioning, as performance degradation is actively managed through monitoring and maintenance planning.
Solution Approach 2:
By implementing continuous thrust measurement and monitoring during flight, wear effects are detected in advance before they significantly impact performance. This preliminary detection allows for planned maintenance interventions rather than reactive overdimensioning, enabling the engine to be sized more efficiently while still maintaining certified thrust through timely maintenance.
3Device complexity
If correction variables are kept constant during flight, then calculation simplicity is maintained, but wear effects cannot be detected
Solution Approach 1:
The patent replaces the complex computational approach (using thermodynamic models and variable correction factors) with a direct mechanical measurement approach. Instead of calculating thrust from multiple sensor inputs and complex models, the system directly measures the force transmitted through the engine mount using strain gauges. This substitution of direct measurement for indirect calculation simplifies the system while improving accuracy.
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 approach provides high accuracy in thrust force determination, allowing for real-time monitoring of wear effects and reducing the need for overdimensioning, thereby lowering costs and weight while maintaining certified thrust levels.
Implementation Method 1
a number of strain gauges on a surface of the force transferring elements enabling a determination of a strain state of the force transferring elements
Implementation Method 2
a number of temperature sensors at least corresponding to the number of strain gauges is provided for measurement of a surface temperature
Implementation Method 3
a heat-conductive element is provided for equalization of temperatures in a region in which the strain gauges are disposed on the surface of the force transferring elements
Data Source
AI summary
A method determines a thrust force of an aircraft engine that is attached to an aircraft by a force transferring element having a strain gauge for determining its strain state and a temperature sensor for measuring a surface temperature of the force transferring element adjacent to the strain gauge. The method includes: determining the surface temperature; determining a strain of the force transferring element; determining the strain state of the force transferring element based on the determined strain and compensating for temperature effects by taking into account the surface temperature, the compensation of the temperature effects taking into account both static and transient influences; and calculating the thrust force of the aircraft engine from the determined strain state.