Bearing-Mounted Speed Sensor Target for Faster Turbine Overspeed Detection
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Solution Overview
Problem
Current gas turbine engines face challenges in accurately detecting over-speed conditions due to torsional deflection and load variations, which can lead to delayed triggering of mitigation measures such as reducing fuel flow.
Innovation Solution
A bearing assembly with a speed sensor target that is rotatable and defines a rotation path, allowing a speed sensor probe to read the rotational speed, is strategically located to provide a surrogate speed measurement for the shaft, enhancing over-speed detection time by being radially spaced from the shaft by a specific percentage of its diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a speed sensor probe reads the speed directly from the shaft, then the measurement should be accurate, but torsional deflection and load variations cause delayed detection of over-speed conditions
Solution Approach 1:
The patent introduces a bearing assembly as an intermediary component between the shaft and the speed sensor probe. The bearing assembly includes a speed sensor target that is radially spaced from the shaft by a specific distance (10%-60% of shaft diameter). This intermediary position allows the probe to read shaft speed without being directly affected by torsional deflection at the shaft surface, thereby improving over-speed detection accuracy and reducing detection time.
2Measurement precision
If the speed sensor target is located close to the shaft, then the measurement reflects actual shaft speed, but torsional deflection causes measurement errors
Solution Approach 1:
The bearing assembly serves as an intermediary structure that carries the speed sensor target at an optimized radial distance from the shaft. This position balances two competing requirements: being close enough to accurately reflect shaft speed, yet far enough to minimize the impact of torsional deflection that occurs at the shaft surface. The bearing assembly effectively mediates between these conflicting demands.
Solution Approach 2:
The patent optimizes the radial spacing parameter between the shaft and the speed sensor target, specifying it as 10%-60% of the shaft diameter. By changing this spatial parameter, the system achieves optimal measurement accuracy while reducing the harmful effects of torsional deflection. This parameter optimization allows the speed sensor to read from a position that is less affected by shaft deformation.
3Measurement precision
If the bearing assembly is radially spaced from the shaft by a large distance, then torsional deflection effects are reduced, but the complexity of the bearing assembly increases
Solution Approach 1:
The bearing assembly performs multiple functions: it supports the shaft mechanically, positions the speed sensor target at the optimal radial distance for accurate speed measurement, and reduces the impact of torsional deflection on measurements. By combining these functions into a single component, the patent avoids increasing overall system complexity while achieving improved measurement accuracy.
Data Source
AI summary
A gas turbine engine includes, among other things, a fan, a fan drive gear system that is coupled with the fan and a fan drive input shaft, a compressor section that includes a first compressor and a second compressor, and a turbine section. The turbine section includes a first turbine coupled with a first shaft and a second turbine coupled through a second shaft to the second compressor. A bearing supports the fan drive input shaft. The bearing is located proximal to, and radially spaced from, a forward end of the first shaft. The bearing includes a speed sensor target that is rotatable with the forward end and that defines a rotation path. A speed sensor probe is situated proximal to the rotation path and is operable to read the speed sensor target.