Liquid Level Sensor System Using Thermal Conduction for Oil Monitoring
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Solution Overview
Problem
Accurately determining the oil level in gas turbine engine lubrication systems is challenging due to varying oil temperatures and sloshing, especially during flight or operation, leading to inaccurate measurements and potential mechanical damage from overfilling.
Innovation Solution
A liquid replenishment system utilizing two resistance temperature detectors (RTDs) positioned at different levels in the reservoir, connected to a controller that monitors temperature changes to determine when to add or stop oil replenishment, ensuring accurate level detection and preventing overfilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance sensors are used to provide accurate readings while oil environment is stable, then measurement precision is improved, but device complexity and weight increase due to noise shielding and compensative wires
Solution Approach 1:
The patent replaces complex capacitance sensors with simple temperature sensors (RTDs) to detect oil level. Instead of using electrical fields and capacitance measurements that require noise shielding and compensative wires, the invention uses thermal conduction principles where temperature sensors detect whether they are immersed in oil or air, providing a mechanically simpler solution with fewer components
Solution Approach 2:
The patent changes the detection parameter from electrical capacitance to temperature. By heating the temperature sensors and monitoring temperature changes over time, the system determines oil level based on thermal conduction differences between oil and air environments, achieving accurate measurement with simpler hardware
2Measurement precision
If capacitance sensors are used to provide accurate readings, then measurement precision is improved, but weight increases due to noise shielding and compensative wires
Solution Approach 1:
The patent replaces heavy capacitance sensor assemblies with lightweight temperature sensors. By eliminating the need for noise shielding and compensative wires, the system achieves significant weight reduction while maintaining measurement accuracy through thermal-based detection
Solution Approach 2:
The patent extracts and removes the unnecessary components (noise shielding and compensative wires) from the sensor system. By using temperature sensors that inherently provide sufficient signal without additional shielding, the system eliminates extraneous weight while preserving measurement capability
3Measurement precision
If temperature sensors are heated to detect oil level through thermal conduction, then measurement precision is improved, but energy consumption increases during the heating process
Solution Approach 1:
The patent implements periodic heating cycles where temperature sensors are heated only during measurement intervals rather than continuously. The controller heats the sensors, waits for thermal equilibrium, takes the measurement, then allows cooling before the next cycle, significantly reducing overall energy consumption while maintaining measurement accuracy
Solution Approach 2:
The patent dynamically controls the heating process by adjusting heating duration and power based on real-time temperature feedback. The system monitors temperature changes and terminates heating when sufficient thermal contrast is achieved, optimizing energy usage while ensuring accurate oil level detection
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 system provides reliable and accurate oil level monitoring, allowing for precise refilling without overfilling, thus preventing mechanical damage and maintaining efficient engine operation.
Implementation Method 1
sensing temperature of the temperature sensors. The controller heats the temperature sensors, determines if the temperature of the temperature sensors has changed a predetermined amount in response to the heating, and determines the quantity of liquid in the reservoir based on whether the temperature of the temperature sensors has changed
Data Source
AI summary
A liquid replenishment system includes a reservoir, a first temperature sensor positioned in the reservoir at a full level, a second temperature sensor positioned in the reservoir at an add level, and a controller. The controller is connected to both the first and second sensors. The controller receives temperature signals from the first and second temperature sensors at first and second times. The controller sends an add liquid signal if temperature sensed by the first temperature sensor is substantially different at the first and second times and if temperature sensed by the second temperature sensor is substantially different at the first and second times. The controller sends a full signal if temperature sensed by the first temperature sensor is substantially the same at the first and second times and if temperature sensed by the second temperature sensor is substantially the same at the first and second times.