Viscometer with Stirling Chiller for Jet Fuel Sub-ambient Testing
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Solution Overview
Problem
Existing methods for characterizing jet fuel at sub-ambient temperatures, such as freeze point, are inadequate, and there is a need for a more reliable method to determine pumpability, freeze point, and pour point to ensure safe aircraft operations.
Innovation Solution
A self-contained viscometer with a reciprocating piston and a chiller, like a Stirling engine, measures dynamic viscosity continuously from ambient to very low temperatures, allowing for rapid temperature changes and determining the pumpability limit, freeze point, and pour point by analyzing viscosity-temperature data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If freeze point characterization is used for jet fuel, then historical measurement simplicity is maintained, but accuracy and reliability of fuel suitability assessment at sub-ambient temperatures deteriorates
Solution Approach 1:
The patent combines the viscometer with an integrated cooling system and temperature control mechanism into a single apparatus. The viscometer measures viscosity while the cooling system simultaneously controls temperature, merging multiple functions (viscosity measurement, temperature control, cooling) into one integrated device that determines pumpability limit, freeze point, and pour point through continuous viscosity-temperature data collection
Solution Approach 2:
The invention measures viscosity across a range of temperatures rather than at a single freeze point temperature. By continuously varying temperature and measuring viscosity at each point, the system identifies critical parameters (pumpability limit, freeze point, pour point) based on viscosity changes, providing more comprehensive fuel characterization
2Measurement precision
If viscosity measurement at sub-ambient temperatures is implemented, then fuel characterization accuracy is improved, but measurement complexity and equipment requirements increase
Solution Approach 1:
The patent combines the viscometer with an integrated cooling system and temperature control mechanism into a single apparatus. The viscometer measures viscosity while the cooling system simultaneously controls temperature, merging multiple functions (viscosity measurement, temperature control, cooling) into one integrated device that determines pumpability limit, freeze point, and pour point through continuous viscosity-temperature data collection
Solution Approach 2:
The viscometer automatically controls the cooling rate and temperature progression through its microprocessor system. The system self-regulates by continuously monitoring viscosity measurements and adjusting temperature accordingly, eliminating the need for separate manual temperature control operations and reducing operational complexity
3Loss of time
If rapid temperature decrease is applied to determine freeze point, then measurement time is reduced, but measurement accuracy may deteriorate due to thermal gradients
Solution Approach 1:
The invention uses a dynamic measurement approach where the temperature is continuously changed rather than held static. The cooling system dynamically adjusts temperature while the viscometer continuously measures viscosity, allowing the system to capture viscosity-temperature relationships in real-time and identify critical points based on measurement trends rather than equilibrium conditions
Solution Approach 2:
The system uses feedback control where viscosity measurements are continuously monitored and used to adjust the cooling rate. The microprocessor system analyzes viscosity data in real-time and modulates the cooling system to maintain optimal measurement conditions, ensuring accuracy even during rapid temperature changes by detecting viscosity anomalies that indicate phase transitions
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
Enables accurate characterization of jet fuel at sub-ambient temperatures, ensuring safe flight operations by determining the suitability of fuel for low-temperature conditions, thereby avoiding potential freezing or crystallization issues.
Implementation Method 1
Dynamic viscosity of the liquid is measured using an oscillating piston measuring technique
Implementation Method 2
Very low temperatures are obtained using a chiller such as a Stirling engine
Data Source
AI summary
An apparatus and method is shown for determining the pumpability limit, freeze point and/or pour point of liquids, particularly fuels, at sub-ambient temperatures. A sample is placed in a viscometer which viscometer is rapidly cooled by a chiller. During cooling, after some measurements of temperature and viscosity, further temperatures and viscosity are approximated using the least squares method, which temperature and viscosity are subsequently measured to determine the pumpability limit. Continuation of the method will also give the freeze point and pour point of the sample being tested.