EVAP Canister Switching During Refueling to Prevent Vapor Overflow
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Solution Overview
Problem
Parallel vapor canister systems in vehicle emission control face issues with uneven loading, leading to overloading and emissions, as natural variability and degradation cause one canister to become more restrictive, resulting in vapor overflow during refueling.
Innovation Solution
A method that determines the load of each canister and directs vapor flow to the less loaded canister during refueling, switching as the fuel level changes, and balances canister loads post-refueling by sealing them from the tank and opening to a common vent line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one vapor canister becomes more restrictive due to natural variability or degradation, then vapor flow favors the less restrictive canister, but the less restrictive canister may overload and spew vapors to the atmosphere, thereby increasing emissions
Solution Approach 1:
The system continuously monitors the restriction level of each canister using pressure sensors during refueling operations. Based on this feedback, the control system dynamically directs vapor flow to the canister with lower restriction, preventing overload and vapor spewing. This closed-loop control ensures reliable vapor distribution while minimizing emissions.
Solution Approach 2:
The system dynamically adjusts vapor flow distribution between canisters based on real-time restriction measurements. The control system modifies the operating state of the vapor recovery system by switching which canister receives vapor flow, adapting to changing conditions such as natural variability or degradation of canister performance over time.
2Device complexity
If a single vapor canister is used, then the system is simpler, but during refueling the canister may become overloaded and spew vapors to the atmosphere
Solution Approach 1:
The vapor recovery system is segmented into multiple parallel canisters instead of using a single canister. This segmentation allows the system to distribute vapor flow across multiple storage units, preventing any single canister from becoming overloaded during refueling operations, thereby reducing vapor spewing and emissions.
Solution Approach 2:
The control system uses pressure sensors to monitor the restriction level of each canister in real-time during refueling. Based on this feedback, the system intelligently directs vapor flow to the appropriate canister, ensuring optimal performance and preventing emissions while managing the complexity of the multi-canister system.
3Reliability
If the vapor canister restriction increases over time due to degradation, then the canister becomes less effective at storing vapors, but increasing canister size to compensate may increase restriction in the vapor line
Solution Approach 1:
Instead of using a single large canister that would increase vapor line restriction, the system segments the vapor storage capacity across multiple smaller canisters. This approach maintains effective vapor storage capacity while avoiding the increased restriction that would result from enlarging a single canister and its associated vapor line.
Solution Approach 2:
The system dynamically manages canister usage based on their current restriction levels. As canisters degrade and restriction increases over time, the control system adjusts vapor flow distribution to favor canisters with lower restriction, maintaining vapor storage effectiveness without requiring increases in canister size that would worsen vapor line restriction.
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 prevents overloading and reduces emissions by ensuring even vapor distribution and balancing canister loads, maintaining efficient vapor management during refueling and extending the useful life of the canisters.
Implementation Method 1
The stored vapors may be purged during a later engine operating condition. The stored vapors may be routed to an engine intake for combustion
Data Source
AI summary
Methods and systems are provided for an evaporative emission fuel (EVAP) system. In one example, a method for the EVAP system includes loading canisters in parallel sequentially during a refueling event. The method further includes switching loading from one canister to another in response to a fuel level during the refueling event.