Off-board Fuel Leak Detection Using CO2 Injection and Pressure Decay
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Solution Overview
Problem
Current on-board and off-board systems face challenges in detecting and locating small fuel leaks in vehicle fuel containment systems, particularly with hole diameters smaller than 0.020 inches, due to limitations in sensitivity and accuracy, leading to false diagnostic codes and inability to identify leaks effectively.
Innovation Solution
An off-board diagnostic system utilizing a vacuum and pressure pump, pressure transducer, reservoir chamber, and calibrated orifice, along with a gas analyzer capable of detecting carbon dioxide and hydrocarbons, to verify and locate leaks in the fuel containment system by monitoring pressure changes and gas composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional on-board and off-board detection systems are used, then the system can detect fuel leaks, but the detection accuracy and sensitivity are insufficient for leaks smaller than 0.020 inches
Solution Approach 1:
The system divides leak detection into two distinct phases: a decay test phase that uses pressure monitoring to detect and size leaks, and a location test phase that uses CO2 injection and gas analysis to locate leaks. This segmentation allows each phase to be optimized for its specific function, improving overall detection accuracy while reducing false positives.
Solution Approach 2:
The system introduces CO2 as an intermediary substance to enhance leak detection. By injecting CO2 into the fuel containment system and monitoring its presence at potential leak points using gas analysis, the system can accurately detect and locate small leaks that would otherwise be undetectable, thereby improving measurement precision without increasing false diagnostic codes.
2Adaptability or versatility
If the leak test threshold is set at 0.040 inch diameter, then it meets OBDII emission requirements, but smaller leaks below this threshold cannot be detected
Solution Approach 1:
The system dynamically adjusts the detection threshold and methodology based on the test phase. During the decay test phase, it can detect leaks as small as 0.008 inches by monitoring pressure changes over time. During the location test phase, it uses CO2 injection to specifically target and locate leaks. This dynamic approach allows the system to meet OBDII requirements for 0.040 inch leaks while simultaneously detecting smaller leaks that exceed current regulatory standards.
3Ease of manufacture
If smoke machines are used for off-board testing, then visual leak detection is possible, but they cannot detect leaks smaller than 0.015 inch diameter
Solution Approach 1:
The system replaces the mechanical/visual smoke detection method with a pressure-based decay test and a gas analysis-based location test. The decay test uses pressure transducers to detect pressure changes caused by leaks as small as 0.008 inches, while the location test uses CO2 injection and gas analysis to precisely locate leaks. This substitution eliminates the minimum detectable hole size limitation of smoke machines while maintaining ease of off-board testing.
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 detection and sizing of leaks as small as 0.008 inch diameter, reducing false diagnostic codes and improving the ability to identify and locate leaks in the fuel containment system, enhancing the reliability of leak testing and diagnosis.
Implementation Method 1
An off-board diagnostic system utilizes a vacuum and pressure pump, pressure transducer, reservoir chamber, and calibrated orifice
Implementation Method 2
pressure transducer to verify and locate leaks in the fuel containment system by monitoring pressure changes
Implementation Method 3
a gas analyzer capable of detecting carbon dioxide and hydrocarbons, to verify and locate leaks in the fuel containment system
Data Source
AI summary
An off-board vehicle fuel handling and containment system leak tester that uses CO2 gas in order to find the location of the leak site. An external source of CO2 gas is used to pressurize the fuel containment system to a pressure greater than the surrounding pressure. An electronic detector capable of detecting CO2 gas is used to scan at least some of the containment system's external surfaces for the presence of the escaping CO2 gas. When the electronic detector senses the CO2 gas an alert system is activated. Once the leak site area is known a leak finding composition of matter is applied to the leak site area in order to identify the exact point of leakage.