Aircraft Fuel Tank Strain Sensing for Accurate Quantity Measurement
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Solution Overview
Problem
Existing fluid quantity sensor systems for aircraft fuel tanks face challenges in accurately measuring fuel quantity while reducing sensor count to minimize installation costs and improve safety, particularly in composite structures where conventional methods are inadequate.
Innovation Solution
A fluid quantity sensor system utilizing strain sensors, such as fiber Bragg grating sensors, integrated into the composite material of the tank structure to measure strain caused by the fuel, canceling out externally induced stress and determining the weight of the fluid by differential measurement between opposite locations on the tank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive sensors and pressure sensors are used to measure fuel quantity, then measurement accuracy is achieved, but sensor count increases leading to higher installation cost and reduced safety
Solution Approach 1:
The patent combines multiple sensing functions into a single strain sensor system. The strain sensor simultaneously measures tank deformation caused by fuel weight and external stresses, eliminating the need for separate capacitive sensors, pressure sensors, and densitometers. This merging of functions directly reduces sensor count while maintaining measurement capability.
Solution Approach 2:
The strain sensor system performs multiple functions: it measures fuel quantity through weight detection, compensates for external stresses (temperature, structural loads), and determines fuel density. This multi-functionality allows a single sensor type to replace multiple specialized sensors, reducing overall system complexity.
2Device complexity
If strain sensors are integrated into composite tank structure, then sensor count is reduced and safety is improved, but externally induced stress interferes with fuel weight measurement
Solution Approach 1:
The system uses strategically placed strain sensors that measure opposing deformations. By positioning sensors to detect strains in opposite directions or locations, the system creates counterbalancing measurements that cancel out external stress effects while preserving the fuel weight signal.
Solution Approach 2:
The system continuously monitors strain measurements and uses this feedback to distinguish between external stress effects and fuel weight effects. By analyzing strain patterns and comparing measurements from multiple sensor locations, the system can identify and compensate for external interference in real-time.
3Reliability
If multiple sensors are installed in aircraft fuel tanks, then measurement redundancy is achieved, but installation cost increases and safety is reduced due to more electrical components
Solution Approach 1:
The patent replaces electrical sensing systems (capacitive sensors, pressure sensors with electrical wiring) with optical strain sensors that use light-based measurement. This substitution eliminates the need for extensive electrical wiring and electronic components within the fuel tank, reducing installation complexity and potential electrical hazards while maintaining 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
Accurately measures fuel quantity in aircraft fuel tanks by eliminating the need for pressure sensors and reducing sensor count, enhancing safety and lowering installation costs through embedded strain sensors that compensate for external stress.
Implementation Method 1
The one or more strain sensors can be one or more fiber Bragg grating (FBG) sensors
Implementation Method 2
one or more strain sensors configured to be disposed in physical communication with the tank to sense a strain on one or more portions of the tank
Data Source
AI summary
A fluid quantity sensor system for sensing a fluid quantity in a fluid tank can include one or more strain sensors configured to be disposed in physical communication with the tank to sense a strain on one or more portions of the tank. The one or more strain sensors can include at least a first strain sensor disposed in physical communication with a first portion of the tank, and a second strain sensor disposed in physical communication with the second portion of the tank such that the first strain sensor is configured to sense a strain of the first portion of the tank and the second strain sensor is configured to sense a strain of the second portion of the tank. The first strain sensor and the second strain sensor can be positioned such that externally induced stress on a structure forming and/or supporting the tank can be cancelled out such that such that a strain caused by only the fluid in the tank can be determined to determine a weight of the fluid in the tank.