Vacuum Pump Pressurization for Liquid Fuel Carryover Mitigation
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Solution Overview
Problem
Existing methods for detecting and mitigating liquid fuel carryover in fuel vapor canisters during refueling events do not effectively prevent canister degradation and increased HC emissions, as they fail to accurately diagnose and remedy liquid fuel presence in evap recovery lines, leading to potential damage from liquid fuel contacting the adsorbent material.
Innovation Solution
A method involving a vacuum pump to pressurize the fuel system based on fuel tank pressure decay rates, where the pump is activated if the first decay rate is less than a threshold and maintained until atmospheric pressure is reached, and deactivated if the second decay rate is greater than a threshold, to diagnose and mitigate liquid fuel carryover by returning it to the fuel tank, thereby avoiding contact with the canister adsorbent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum pump is activated to pressurize the fuel system during refueling, then liquid fuel carryover in evap recovery lines can be mitigated by returning it to the fuel tank, but the system complexity and energy consumption increase
Solution Approach 1:
The system activates the vacuum pump during refueling operations to pressurize the evap recovery lines before liquid fuel can enter the canister. This preliminary action prevents liquid fuel carryover from reaching the canister in the first place, thereby protecting the adsorbent material from degradation while managing the complexity through condition-based activation
Solution Approach 2:
The system uses the vehicle's existing vacuum pump (designed for leak detection) to serve a dual function: pressurizing the fuel system to mitigate liquid fuel carryover. This self-service approach reduces additional device complexity by repurposing an existing component rather than adding a dedicated pump
2Object-generated harmful factors
If the vacuum pump is activated during refueling to prevent liquid fuel carryover, then HC emissions are reduced, but the energy consumption increases
Solution Approach 1:
The vacuum pump is activated periodically only during refueling operations when liquid fuel carryover is likely to occur. The control system monitors refueling conditions and activates the pump only when needed, rather than continuously, thereby reducing energy consumption while still preventing HC emissions during the critical refueling period
Solution Approach 2:
The system changes the operational parameters of the vacuum pump by activating it in reverse mode (pressurization) during refueling, rather than using it in its normal vacuum mode. This parameter change allows the existing pump to serve the prevention function during high-risk periods, reducing overall energy consumption compared to continuous operation
3Ease of operation
If liquid fuel is not mitigated in the evap recovery lines, then the system operation is simpler, but the adsorbent material degrades and loses efficiency
Solution Approach 1:
The control system monitors fuel tank pressure decay rates to detect the presence of liquid fuel in the evap recovery lines. When liquid fuel is detected (indicated by abnormal pressure decay), the system automatically activates the vacuum pump to pressurize the lines and return liquid fuel to the tank. This feedback mechanism maintains adsorbent efficiency without requiring continuous complex intervention
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 approach effectively diagnoses and mitigates liquid fuel carryover, preventing canister degradation and reducing HC emissions by ensuring liquid fuel is not drawn into the vapor canister during purging events, thus extending the life of the adsorbent and maintaining fuel system efficiency.
Implementation Method 1
activating a vacuum pump to pressurize the fuel system
Data Source
AI summary
Methods and systems are provided for detecting and mitigating the presence of liquid fuel carryover in an evap system of a vehicle in response to a refueling event. In one example, during a first condition, a vacuum pump is activated to pressurize the fuel system responsive to a first fuel tank pressure decay rate being less than a threshold, and responsive to a second fuel tank pressure decay rate being greater than a threshold, the vacuum pump is maintained on until a fuel tank pressure decreases to atmospheric pressure. In this way, liquid fuel carryover can be quickly and accurately diagnosed, such that mitigating actions may be taken to ensure liquid fuel is returned to the tank prior to contacting the adsorbent material within the vapor canister.