Pneumatic Liquid Measurement System for Aircraft Fuel Tanks
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Solution Overview
Problem
In aircraft fuel tanks, measuring the quantity of liquid is challenging due to irregular shapes and complex structures, and conventional methods require numerous sensors, which pose electrical hazards and violate aviation regulations by introducing electrical energy into flammable environments.
Innovation Solution
A liquid measurement system using a single pressure sensor and densitometer, which introduces a known mass of air to measure the change in air pressure, determining the volume of ullage and combining it with density measurements to calculate the liquid quantity without electrical components inside the tank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensor arrays with electrical interfaces are used to measure liquid quantity in aircraft tanks, then measurement coverage at all fuel levels and attitudes is ensured, but electrical hazards and ignition risks are introduced into the flammable environment
Solution Approach 1:
The patent replaces electrical sensors and electronics with a purely mechanical measurement system. A float indicator mechanism physically moves with fuel level changes, driven by buoyancy forces on the float. This mechanical system eliminates all electrical components from the fuel tank environment, resolving the contradiction between measurement accuracy and electrical safety hazards.
Solution Approach 2:
The patent employs pneumatic principles where compressed air is introduced into the tank to displace fuel and measure volume changes. The air pressure system mechanically interacts with the fuel-air interface, allowing quantity measurement without electrical sensors in the hazardous zone. This pneumatic approach maintains measurement capability while eliminating electrical ignition risks.
2Measurement precision
If multiple sensors and measurement electronics are installed in the tank to ensure accurate measurement, then liquid quantity can be determined at all levels, but system complexity and weight increase
Solution Approach 1:
The patent replaces complex electrical sensor arrays with simple mechanical components: a float that rises and falls with fuel level, connected to an indicator mechanism. This mechanical substitution dramatically reduces system complexity and component count while maintaining measurement functionality across all fuel levels.
Solution Approach 2:
The float indicator mechanism serves multiple functions simultaneously: it tracks fuel level position, provides visual indication, and can trigger alerts at critical levels. This multi-functional mechanical design eliminates the need for separate sensors and electronics for each measurement task, reducing overall system complexity.
3Measurement precision
If conventional measurement systems with numerous components are used, then comprehensive fuel level monitoring is achieved, but system weight increases
Solution Approach 1:
The patent replaces heavy electrical sensors, wiring harnesses, and electronic processing units with lightweight mechanical components. The float indicator mechanism consists primarily of buoyant materials and simple mechanical linkages, significantly reducing the weight of the measurement system while maintaining measurement accuracy.
Solution Approach 2:
The patent employs simple, inexpensive mechanical components that can be easily manufactured and replaced if needed. The float and indicator mechanism uses basic materials rather than expensive electronic components, reducing both initial weight and long-term maintenance burden.
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 system reduces complexity and weight, ensures safety by avoiding electrical hazards, and provides accurate and continuous measurement of liquid quantity within the tank, suitable for irregularly shaped tanks like those on aircraft.
Implementation Method 1
measuring the change in air pressure within the tank in response to the introduction of the known mass of air
Implementation Method 2
a densitometer able to measure a density of the liquid within the tank
Data Source
Figure 1A~1B
AI summary
A liquid measurement system for determining a quantity of a liquid within a tank (10) includes a pressurized air supply (22), a valve (20) connected to the pressurized air supply with the valve able to introduce a known mass of air into the tank, a pressure sensor (26) able to measure the change in air pressure within the tank, and a processor (30) operatively connected to the valve and the pressure sensor. The processor is able to determine the volume of the liquid within the tank from the known mass of air introduced into the tank and the change in air pressure within the tank.