Fuel Vapor Purging Diagnostics for Boosted Engines
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Solution Overview
Problem
Existing fuel vapor recovery systems in vehicles with boosted internal combustion engines face issues with reverse flow of air and fuel vapors, leading to over-pressure and degradation of components, as well as excessive evaporative emissions, due to stuck or degraded valves and increased intake manifold pressure.
Innovation Solution
A method is implemented to monitor and diagnose reverse flow by sensing changes in fluid pressure and flow using a fuel tank pressure sensor, enabling the engine controller to identify improper flow and promptly disable boost to prevent component damage and reduce emissions, by configuring the system to seal the fuel vapor recovery system from the intake manifold during boosted conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the canister purge valve and check valve are used in a boosted engine system, then fuel vapor purging function is achieved, but reverse flow of boosted air may occur causing over-pressure and component degradation
Solution Approach 1:
The system performs preliminary sealing of the fuel vapor recovery system from the intake manifold during boosted conditions before reverse flow can occur. The controller monitors boost conditions and proactively seals the system, preventing the harmful reverse flow of boosted air that would otherwise cause over-pressure and component degradation.
Solution Approach 2:
The system uses a fuel tank pressure sensor to continuously monitor pressure conditions in the fuel vapor recovery system. This feedback mechanism allows the controller to detect reverse flow conditions and take corrective action by sealing the system, creating a closed-loop control that prevents damage while maintaining purging functionality.
2Object-affected harmful factors
If the fuel vapor recovery system is sealed from the intake manifold during boosted conditions, then reverse flow is prevented, but monitoring for reverse flow diagnostics is required
Solution Approach 1:
The fuel tank pressure sensor serves multiple functions: it monitors pressure for reverse flow detection, tracks system status for diagnostic purposes, and provides data for controller decision-making. This multi-functionality reduces the need for additional dedicated sensors while maintaining comprehensive monitoring capability.
Solution Approach 2:
The system uses existing components (fuel tank pressure sensor, controller) to perform reverse flow monitoring and diagnostics without requiring separate dedicated monitoring hardware. The controller analyzes pressure data and system state to autonomously determine reverse flow conditions, making the system self-diagnosing.
3Productivity
If reverse flow is not detected and mitigated, then system operation continues, but component degradation and excessive evaporative emissions occur
Solution Approach 1:
The controller continuously monitors pressure sensor data to detect reverse flow conditions. When reverse flow is detected, the system provides feedback to the controller which then seals the fuel vapor recovery system from the intake manifold, stopping the harmful process before excessive emissions occur while maintaining system operational status.
Solution Approach 2:
The system detects reverse flow conditions that would normally cause harm (emissions, over-pressure) and converts this potentially harmful situation into a beneficial diagnostic opportunity. By monitoring pressure changes during sealed operations, the system identifies valve degradation issues before they cause significant damage, turning a problem condition into a preventive maintenance trigger.
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 reduces component degradation and excessive evaporative emissions by identifying and mitigating reverse flow, ensuring the fuel vapor recovery system operates within safe pressure limits and maintains emissions quality.
Implementation Method 1
sensing changes in fluid pressure and/or fluid flow in a fuel vapor recovery system, for example fluid pressure and/or fluid flow changes across a component of the fuel vapor recovery system (such as a fuel tank pressure sensor)
Implementation Method 2
the vaporized hydrocarbons (HCs) are stored in a fuel vapor canister packed with an adsorbent which adsorbs and stores the vapors
Data Source
AI summary
Systems and methods are provided for monitoring reverse flow of fuel vapors and/or air through a vehicle fuel vapor recovery system, said fuel vapor recovery system coupled to an engine intake of a boosted internal combustion engine. One example method comprises, during boost, when the fuel vapor recovery system is commanded to be sealed from the intake, indicating degradation based on a pressure value at a venturi in the fuel vapor recovery system.