Non-contact Optical Fuel Gauging via External Sensor
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Solution Overview
Problem
Current aircraft fuel gauging systems face challenges such as high costs, increased downtime for maintenance, and safety concerns due to the need for sensors and wiring inside fuel tanks, which also complicate accurate fuel level measurements due to factors like fuel density and tank geometry.
Innovation Solution
A non-contact optical pressure sensor system is used, located outside the fuel tank, employing differential and absolute pressure sensors with optical prism technology to measure fuel levels accurately without the need for in-tank installations, reducing weight, maintenance time, and electromagnetic interference risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive probes are disposed inside the fuel tank to measure fuel level and quantity, then measurement accuracy is improved, but device complexity and weight increase due to requiring multiple sensors, mounting hardware, and wiring
Solution Approach 1:
The sensing elements are extracted from the fuel tank interior and relocated to the exterior surface. The fuel tank wall acts as a transparent medium for optical sensing, allowing measurement without direct sensor contact with fuel. This eliminates the need for internal wiring and mounting hardware while maintaining measurement capability.
Solution Approach 2:
The mechanical/electrical sensing system (capacitive probes with wiring) is replaced with an optical sensing system. Optical sensors mounted on the exterior use light transmission through the tank wall to detect fuel level, eliminating the need for electrical wiring inside the tank and reducing overall system complexity.
2Device complexity
If pressure-based systems are used to measure fuel quantity, then device complexity is reduced with fewer sensors, but measurement reliability deteriorates due to sensitivity to wing distortion and tank pressure variations
Solution Approach 1:
The pressure-based mechanical measurement system is replaced with an optical transmission system. Optical sensors measure fuel level directly through light transmission properties, which are not affected by wing distortion or pressure variations, thereby improving reliability while maintaining low device complexity.
Solution Approach 2:
The measurement parameter changes from pressure differential (which is affected by external factors) to optical transmission properties (which are not affected by wing distortion or pressure). This parameter change fundamentally improves measurement reliability under varying flight conditions.
3Measurement precision
If sensors and wiring are installed inside the fuel tank, then measurement accuracy is improved, but safety concerns increase due to electromagnetic interference and fire hazards
Solution Approach 1:
All electrical components and wiring are extracted from the fuel tank interior. The sensing function is achieved through optical transmission through the tank wall, completely eliminating electromagnetic interference sources from the hazardous fuel environment while maintaining measurement accuracy.
Solution Approach 2:
The electrical sensing system is replaced with an optical system. Optical sensors mounted externally use light transmission to detect fuel level without generating electromagnetic fields that could cause interference or fire hazards, thereby improving safety while maintaining measurement capability.
4Measurement precision
If in-tank sensors and wiring are used, then measurement capability is achieved, but maintenance downtime increases due to complex sensor replacement requirements
Solution Approach 1:
The sensors are extracted from the difficult-to-access interior of the fuel tank and mounted on the exterior surface. This location change enables simple maintenance access without requiring tank drainage or disassembly, allowing rapid sensor replacement and reducing maintenance downtime while preserving measurement capability.
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 provides high accuracy in fuel level measurement, reduces system weight by 35%, minimizes downtime, and ensures safety by eliminating in-tank wiring, while maintaining or exceeding required accuracy standards for aircraft fuel tank measurements.
Implementation Method 1
the optical prism is configured to generate an optical light path therein, and when the optical prism is in contact with liquid inside the receptable, the optical light path is disturbed by the liquid
Implementation Method 2
the plurality of sensor units includes at least one of an optical differential pressure sensor and an optical absolute pressure sensor
Implementation Method 3
the plurality of sensor units includes at least one of an optical differential pressure sensor and an optical absolute pressure sensor
Implementation Method 4
an integrated sensor unit including a temperature sensor configured to measure a temperature at the physical location thereof
Implementation Method 5
pressure-based systems may measure a hydrostatic pressure differential within the fuel tank in order to estimate the quantity of fuel remaining inside the fuel tank
Data Source
AI summary
A measurement system and method for liquid quantity in a receptable, the measurement system including a plurality of sensor units at various locations of the receptacle, the receptable including the liquid therein, each of the plurality of sensor units being on an outside surface of the receptacle, a data receiver coupled to the plurality of sensor units via one or more connectors and configured to receive measurements from the plurality of sensor units via the one or more connectors, and a processor coupled to the data receiver and configured to convert the received measurements from the plurality of sensor units to a measured quantity of liquid inside the receptable.