Evaporative Emissions System Liquid Fuel Carryover Detection
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Solution Overview
Problem
Existing fuel vapor recovery systems face issues with liquid fuel entering the fuel vapor canister, leading to adsorption efficiency loss in activated charcoal and increased HC emissions, as existing detection methods do not effectively prevent liquid fuel from contacting the charcoal or purge liquid fuel from the evap recovery lines.
Innovation Solution
A method involving venting the fuel tank to atmosphere during refueling and sealing it afterward, then running the engine in reverse to force air through the vapor storage system and return liquid fuel to the tank, using a fuel tank isolation valve, canister purge valve, and canister vent valve to manage pressure and purge fuel vapors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid fuel enters the fuel vapor canister during refueling, then the canister becomes filled with liquid fuel, but the activated charcoal loses adsorption efficiency and HC emissions increase
Solution Approach 1:
The system performs a preliminary purge operation before normal canister filling to detect and remove liquid fuel from the evap recovery lines. By checking for liquid fuel presence before the canister becomes saturated, the system prevents liquid fuel from entering the activated charcoal, thereby maintaining adsorption efficiency and preventing HC emissions increase.
Solution Approach 2:
The system uses feedback from the purge operation to detect liquid fuel presence in the evap recovery lines. Based on this feedback, the control system adjusts subsequent refueling operations to prevent liquid fuel from reaching the canister, thus protecting the activated charcoal's adsorption efficiency and reducing HC emissions.
2Productivity
If purge operation is performed to clear fuel vapor from the canister, then fuel economy is maintained, but liquid fuel may be sucked into the canister and corrupt the activated carbon
Solution Approach 1:
Before performing the purge operation to maintain fuel economy, the system first checks for liquid fuel presence in the evap recovery lines. This preliminary detection prevents the purge operation from sucking liquid fuel into the canister, thereby protecting the activated carbon from corruption while still allowing beneficial vapor purging to occur.
Solution Approach 2:
The system uses feedback from liquid fuel detection to control the purge operation. When liquid fuel is detected, the system modifies or prevents the purge operation, allowing it to proceed only when safe, thus maintaining fuel economy without risking activated carbon corruption.
3Productivity
If liquid fuel is purged to the intake, then the purge operation completes, but engine power reduces due to extremely low air-fuel ratio
Solution Approach 1:
The system performs a preliminary check for liquid fuel in the evap recovery lines before initiating the purge operation. By detecting liquid fuel presence in advance, the system prevents the purge operation from introducing liquid fuel into the engine intake, thereby avoiding the extremely low air-fuel ratio condition that causes engine power reduction.
Solution Approach 2:
The system uses feedback from liquid fuel detection to control the purge operation timing and execution. When liquid fuel is detected, the system adjusts the purge strategy to prevent liquid fuel from reaching the intake, thus completing the purge operation without compromising engine power.
4Quantity of substance
If pump operator adds fuel after automatic shut-off to maximize fuel pumped, then fuel quantity increases, but liquid fuel enters the evap recovery lines and corrupts the canister
Solution Approach 1:
The system uses feedback from liquid fuel detection during refueling to alert the pump operator or automatically control the refueling process. When liquid fuel presence is detected in the evap recovery lines, the system provides feedback to stop or modify the refueling operation, preventing further liquid fuel from entering the canister while still allowing maximum safe fuel quantity to be pumped.
Solution Approach 2:
The system performs self-diagnosis during refueling by monitoring for liquid fuel presence in the evap recovery lines. This self-service capability allows the system to automatically detect and respond to potential canister corruption conditions, protecting adsorption efficiency while enabling the pump operator to maximize fuel quantity within safe operating limits.
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 method quickly diagnoses and mitigates liquid fuel in the evap recovery lines, preventing it from entering the vapor canister and maintaining adsorption efficiency, reducing HC emissions and engine power loss.
Implementation Method 1
running the engine un-fueled in reverse to force air from an intake manifold of the engine through the vapor storage system into the tank
Implementation Method 2
vaporized hydrocarbons (HCs) released from a fuel tank are captured and stored in a fuel vapor canister containing a quantity of fuel-absorbing material such as activated charcoal
Data Source
AI summary
Methods and systems are provided for detecting and mitigating the presence of liquid fuel carryover in an evaporative emissions control system of a vehicle in response to a refueling event. In one example, an electric motor is operated to spin a vehicle engine unfueled in reverse in order to pressurize the evaporative emissions system and the fuel system responsive to an indication of liquid fuel in the vapor recovery lines. In this way, indication of liquid fuel carryover following a refueling event may be quickly diagnosed, and mitigating actions may be taken to ensure liquid fuel is returned to the tank prior to contacting the adsorbent material within the vapor canister.