Fuel Tank Pressure Adjustment Using Canister Bypass Venturi Purging
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Solution Overview
Problem
The series connected carbon filled canisters in evaporative emissions control systems limit the depressurization of fuel tanks, leading to increased pressurization and purging times, which can affect engine combustion stability and are particularly problematic in hybrid vehicles where faster purging is desired.
Innovation Solution
Opening a fuel tank isolation valve and a bypass valve of a first carbon filled canister to facilitate faster depressurization and air flow into the fuel tank, utilizing a venturi pump to mix air with fuel vapors and improve engine combustion stability by reducing the delivery of fuel slugs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If series connected carbon filled canisters are used to store fuel vapors, then evaporative emissions control is improved, but fuel tank depressurization time increases
Solution Approach 1:
The system divides the single series path into multiple parallel paths by providing multiple carbon canisters (first canister and second canister) with selective bypass capabilities. This segmentation allows vapor to flow through different routes simultaneously, increasing overall flow capacity while maintaining emission control functionality.
Solution Approach 2:
The bypass valve acts as an intermediary component that provides an alternative flow path around the carbon canisters. When opened, it mediates between the need for rapid depressurization and the emission control function, allowing unrestricted airflow when canister capacity is sufficient.
2Object-affected harmful factors
If series connected carbon filled canisters are used to store fuel vapors, then evaporative emissions control is improved, but purging speed decreases
Solution Approach 1:
The purging function is segmented across multiple canisters with independent bypass controls. The system can selectively engage bypass valves for individual canisters based on their saturation levels, enabling parallel purging operations that increase overall purging speed while maintaining emission control.
Solution Approach 2:
The system dynamically adjusts flow paths based on real-time canister saturation conditions. The controller monitors canister states and selectively opens bypass valves to optimize purging speed at different stages of the purging process, transitioning from emission-controlled mode to rapid purging mode when appropriate.
3Productivity
If fuel vapors are delivered directly to the engine, then purging function is achieved, but engine combustion stability deteriorates
Solution Approach 1:
The bypass system acts as an intermediary between the fuel tank and engine, providing a controlled mixing zone where vapor and air can combine before reaching the engine. This mediation prevents direct delivery of concentrated fuel vapor slugs, smoothing out the air-fuel mixture and maintaining combustion stability.
Solution Approach 2:
The system changes the concentration parameter of the vapor delivery by introducing air mixing through the bypass path. This transforms the delivery from high-concentration vapor slugs to a more diluted and stable air-vapor mixture, improving combustion stability while maintaining purging effectiveness.
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 reduces pressurization and depressurization times in fuel vapor storage systems, enhances engine combustion stability, and is beneficial for hybrid vehicles by allowing quicker evaporative emissions system purging.
Implementation Method 1
a venturi pump and bypass valves may allow vacuum to be quickly removed from a fuel tank by allowing air to flow around fuel vapor canisters
Data Source
AI summary
Methods and systems for purging fuel vapors from an evaporative emissions system of a vehicle are described. The methods and systems may include opening one or more bypass valves of carbon filled canisters to supply air to a low pressure port of a venturi pump. The bypass valves may be opened when fuel vapors are being moved from a fuel tank to an engine while the engine operates.