Fuel Tank Isolation Valve Layout for Multi-Canister Vapor Control
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Solution Overview
Problem
Heavy duty vehicles face challenges with onboard vapor recovery systems due to large fuel tanks, which can lead to premature refueling pump shut-off and inadvertent vapor release during long shut-off events with high diurnal temperatures.
Innovation Solution
A fuel system comprising a fuel tank, multiple vapor canisters, and a first fuel tank isolation valve (FTIV) that fluidly couples the fuel tank to multiple canister vent lines, reducing system complexity, depressurization times, and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single large canister is used in heavy duty vehicles, then the refueling pump shut-off issue is avoided, but the system complexity increases and depressurization time increases
Solution Approach 1:
The single large canister is divided into multiple smaller canisters (first canister, second canister, third canister) that work in parallel. This segmentation reduces the complexity of managing a single large component while maintaining the total vapor storage capacity needed to prevent refueling pump shut-off issues.
2Device complexity
If a series canister arrangement is used, then the system complexity is reduced, but the refueling pump shut-off occurs prematurely
Solution Approach 1:
Instead of a series arrangement where vapors pass through multiple canisters sequentially, the patent uses parallel canisters that can simultaneously store vapors. This maintains low system complexity while ensuring sufficient vapor storage capacity to prevent premature refueling pump shut-off.
3Reliability
If parallel canister arrangements are used, then the refueling pump operation is maintained, but vapors are released during long shut-off events with high diurnal temperatures
Solution Approach 1:
A fuel tank isolation valve is introduced as an intermediary component that controls the connection between the fuel tank and the canister system. During long shut-off events with high temperatures, this valve can be closed to prevent vapor expansion and potential release, while allowing normal vapor recovery operations during refueling and vehicle operation.
Solution Approach 2:
The system uses dynamically controllable valves (fuel tank isolation valve, canister vent valves) that adjust the vapor flow paths based on operating conditions. This allows the system to maintain parallel canister operation for refueling reliability while preventing vapor release during temperature extremes by closing appropriate valves.
4Reliability
If parallel canister arrangements are used, then the refueling pump operation is maintained, but the system complexity increases
Solution Approach 1:
The parallel canister arrangement is implemented with multiple canisters of comparable size rather than one large canister, which simplifies manufacturing and installation while maintaining the total storage capacity needed for reliable refueling operations.
Solution Approach 2:
The fuel tank isolation valve acts as a central control point that manages the parallel canister system, simplifying the overall control logic by providing a single valve to open or close based on temperature conditions, rather than requiring complex control of multiple individual canister valves.
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
The proposed solution effectively manages fuel tank pressures and canister loads, reducing emissions and improving fuel system efficiency by optimizing vapor flow and purging processes.
Implementation Method 1
the canister(s) being sized to adsorb vapors during refueling, running loss, hot soak, and vehicle off
Data Source
AI summary
Methods and systems are provided for a fuel system. In one example, a fuel system includes a plurality of canisters with a fuel tank isolation valve (FTIV) configured to control a fluid coupling between each of the plurality of canisters and a fuel tank. The FTIV is actuated based on one or more of a fuel tank pressure and a load of each of the plurality of canisters.