Capacitive Chip Detection With Size Filtering for Engine Fluids
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Solution Overview
Problem
Existing magnetic chip detectors in aircraft engines are prone to nuisance detections due to the accumulation of harmless metallic particles, known as 'fuzz,' which can trigger false alarms and lead to unnecessary maintenance, as they lack the ability to differentiate between small and large chips effectively.
Innovation Solution
A capacitive chip detector system utilizing a cylindrical capacitor with electric conductors and a strainer to detect changes in capacitance caused by metallic chips, allowing only chips above a certain size to accumulate and prevent smaller particles from passing through, thereby reducing false alarms by providing a more accurate indication of engine health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic chip detector is used to detect all metallic particles, then detection sensitivity is improved, but false alarms increase due to accumulation of harmless fuzz
Solution Approach 1:
The detector is segmented into two functional zones: a first region with a magnetic attractor for capturing larger chips, and a second region with a strainer for filtering smaller particles. This segmentation allows the system to differentiate between significant chips and harmless fuzz, resolving the contradiction between detection sensitivity and false alarm rate.
Solution Approach 2:
Different regions of the detector have different local qualities: the first region has magnetic properties for attracting ferromagnetic chips, while the second region has filtering properties with a strainer. This local differentiation enables selective detection of chip sizes, improving reliability by excluding harmless small particles from triggering false alarms.
2Measurement precision
If all metallic chips are collected for analysis, then diagnostic accuracy is improved, but maintenance complexity increases due to unnecessary investigations
Solution Approach 1:
The strainer extracts and retains only particles above a certain size threshold, separating them from smaller harmless particles. This extraction principle ensures that only potentially significant chips are collected for analysis, reducing maintenance complexity by eliminating unnecessary investigations of benign particles while maintaining diagnostic accuracy for actual problems.
3Measurement precision
If a strainer with small mesh size is used to filter chips, then detection accuracy is improved, but fluid flow resistance increases
Solution Approach 1:
The strainer applies partial filtering action by only retaining particles above a specific size threshold rather than filtering all particles. This partial action maintains detection accuracy for significant chips while minimizing fluid flow resistance, as the mesh size is optimized to pass harmless small particles while capturing problematic larger chips.
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 capacitive chip detector system effectively reduces nuisance detections by allowing smaller particles to pass through while accumulating larger chips, providing a more accurate assessment of engine health and minimizing unnecessary maintenance alerts.
Implementation Method 1
an electric circuit including the capacitor, the electric circuit providing an output indicative of a change in capacitance of the capacitor caused by a presence of one or more chips between the first electric conductor and the second electric conductor
Implementation Method 2
an electric field between the first electric conductor and the second electric conductor
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Capacitive chip detectors (28; 328) for detecting metallic chips (42A, 42B, 42C) in engine fluid (26) of an engine (10) are provided. A capacitive chip detector (28; 328) includes a capacitor having first and second electric conductors (36, 38). The detector (28; 328) further includes an inlet (48) for receiving engine fluid (26) between the first and second electric conductors (36, 38). The capacitive chip detector (28; 328) includes an electric circuit (34; 334) including the capacitor, which capacitance changes when metallic chips (42A, 42B, 42C) are present between the first and second electric conductors (36, 38). The electric circuit (34; 334) provides an output indicative of a chip detection between the first and second electric conductors (36, 38).