Fuel Tank Leak Detection via Differential Pressure Sensing
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Solution Overview
Problem
Existing vapor management systems for vehicles, particularly high-pressure fuel tanks, face challenges in detecting leaks without bleeding off pressure, which is necessary to comply with environmental regulations and maintain elevated pressure to suppress fuel evaporation.
Innovation Solution
A diagnostic system that includes a fuel tank with a vapor cavity, a differential pressure sensor, and a temperature sensor connected to a processor, utilizing a sample tube structure to measure differential pressure and temperature intervals, allowing for leak detection without venting the tank pressure, using algorithms to determine if a leak is present based on pressure and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure is bled off before tank diagnostics, then leak detection can be performed using existing methods, but the elevated pressure needed to suppress fuel evaporation is lost
Solution Approach 1:
The patent changes the operating parameters of the leak detection system by using differential pressure sensors capable of measuring pressure differences in high-pressure environments (up to 10 bar). The system measures differential pressure between the tank interior and exterior without equalizing pressures, enabling leak detection while maintaining elevated tank pressure to suppress evaporation
Solution Approach 2:
The patent replaces the mechanical pressure equalization process (bleeding off pressure) with a differential pressure measurement system. Instead of mechanically venting pressure to enable detection, the system uses differential pressure sensors to directly measure pressure differences across the tank wall, substituting a mechanical process with a sensing-based approach
2Reliability
If existing leak detection methods are used, then diagnostic capability is provided, but the system requires pressure to be bled off which complicates the operation
Solution Approach 1:
The system performs self-diagnosis by continuously monitoring differential pressure across the tank wall during normal operation. The microprocessor controller automatically analyzes pressure differential data to detect leaks, eliminating the need for manual pressure equalization procedures and enabling autonomous diagnostic functionality
Solution Approach 2:
The differential pressure monitoring system operates continuously during normal tank pressurization, enabling ongoing leak detection without interrupting the pressure maintenance function. This continuous monitoring approach eliminates the need for periodic pressure bleeding and repressurization cycles
3Ease of operation
If differential pressure sensing is implemented in high pressure environment, then leak detection without pressure bleeding is enabled, but sensor durability and measurement accuracy become critical challenges
Solution Approach 1:
The patent segments the pressure measurement function into two separate pressure sensing points: one measuring tank interior pressure and another measuring tank exterior pressure. By measuring each pressure independently and calculating the differential, the system achieves accurate leak detection while using sensors rated for the respective pressure environments
Solution Approach 2:
The patent introduces a differential pressure measurement approach as an intermediary method between direct high-pressure sensing and atmospheric pressure sensing. The system uses the pressure differential across the tank wall as the measurement parameter, which remains small and measurable even when absolute pressures are high, thereby protecting sensor accuracy
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 effective leak detection in high-pressure fuel tank environments without the need to bleed off pressure, ensuring compliance with environmental standards and maintaining the benefits of elevated tank pressure, thereby preventing fuel vapor release into the atmosphere.
Implementation Method 1
A differential pressure sensor has one side thereof connected to the sense tube and another side thereof connected to the vapor cavity so that the pressure sensor can measure a differential pressure (DP) between a volume of the vapor cavity and a volume of the sense tube containing the liquid fuel
Implementation Method 2
A temperature sensor is provided in the vapor cavity, with signals from the pressure sensor and temperature sensor being received by the processor
Implementation Method 3
The differential pressure (DP) and the temperature (T) are measured at certain time intervals to determine the temperature at time zero (T0), the differential pressure at time zero (DP0), the temperature at a certain time (Tt), and the differential pressure at a certain time (DPt)
Data Source
AI summary
A vapor management system (10) includes a sense tube (47) disposed in a fuel tank (12). A differential pressure sensor (17) has one side connected to the sense tube and another side connected to a vapor cavity so that the pressure sensor can measure a differential pressure (DP) between a volume of the vapor cavity and a volume of the sense tube containing liquid fuel. A temperature sensor (26) is in the vapor cavity. A processor 1) receives DP and T measurements at certain time intervals to determine the temperature at time zero (T0), the differential pressure at time zero (DP0), the temperature at a certain time (Tt), and the differential pressure at a certain time (DPt), and 2) when (Tt−T0) is greater than a certain value, compares DPt to a certain differential pressure value.