Boost-Assisted Purge Flow for Evaporative Emissions Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional evaporative emissions (EVAP) systems for boosted engines are unable to draw a sufficient amount of fuel vapor into the induction system, limiting engine power and efficiency due to the Venturi effect's inefficiency in positive pressure environments.
Innovation Solution
The EVAP system incorporates a boost line connected to a vapor canister with a boost pressure control valve, purge lines to the engine and exhaust treatment system, and a controller to manage boost pressure and direct fuel vapor flow, including an exhaust purge valve for enriching exhaust gas and regenerating NOx traps, ensuring optimal fuel vapor delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a Venturi effect is used to draw fuel vapor into the induction system, then fuel vapor can be delivered to the engine, but the amount of fuel vapor drawn is insufficient in positive pressure environments
Solution Approach 1:
Instead of using negative pressure (Venturi effect) to draw fuel vapor into the induction system, the patent applies positive boost pressure to force fuel vapor out of the canister and into the induction system. This inversion of the pressure approach resolves the contradiction by making the purge system effective in positive pressure environments where conventional Venturi systems fail.
Solution Approach 2:
The patent changes the pressure parameter from negative (vacuum) to positive (boost pressure) to enable fuel vapor delivery in boosted engine conditions. By controlling the boost pressure applied to the vapor canister, the system can reliably deliver sufficient fuel vapor quantities regardless of the engine's operating pressure conditions.
2Quantity of substance
If boost pressure is applied to the vapor canister to force fuel vapor out, then fuel vapor delivery is improved, but the air/fuel ratio may become unbalanced
Solution Approach 1:
The controller monitors engine operating conditions and adjusts the boost pressure applied to the vapor canister accordingly. This feedback control ensures that fuel vapor is delivered at the appropriate rate to maintain the correct air/fuel ratio, preventing enrichment while still achieving sufficient vapor delivery in boosted conditions.
Solution Approach 2:
The system dynamically adjusts the amount of boost pressure applied to the vapor canister based on real-time engine conditions. This dynamic control allows the system to optimize fuel vapor delivery while maintaining proper air/fuel ratio balance across varying operating conditions, resolving the contradiction between delivery quantity and composition stability.
3Device complexity
If conventional EVAP systems are used for boosted engines, then the system structure is simple, but the system cannot obtain desired fuel vapor amounts
Solution Approach 1:
The boost pressure control valve serves multiple functions: it controls boost pressure to the vapor canister for fuel vapor delivery, and can also direct fuel vapor to the exhaust treatment system for LNT regeneration. This multi-functionality allows the system to achieve desired fuel vapor amounts without proportionally increasing device complexity, as a single component handles multiple purge requirements.
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 solution enhances fuel vapor delivery to the engine and induction system, maintains a stoichiometric air/fuel ratio, and regenerates NOx traps without rich air/fuel mixtures, improving engine efficiency and reducing emissions.
Implementation Method 1
a boost pressure control valve disposed in-line along the boost line and configured to control an amount of boost pressure provided to the vapor canister
Implementation Method 2
Conventional EVAP systems for boosted engines utilize a hose (e.g., connected after a turbocharger) and an injector tee to create a Venturi effect that draws fuel vapor into the induction system
Implementation Method 3
the exhaust purge valve is configured to provide the fuel vapor into exhaust gas in the exhaust treatment system at a point upstream from a catalytic converter
Data Source
AI summary
A vapor canister of an evaporative emissions (EVAP) system is configured to store fuel vapor evaporated from a liquid fuel housed in a fuel tank of a vehicle. A boost line is connected between a high-pressure side of a boost system of an engine and the vapor canister, a boost pressure control valve is disposed in-line along the boost line and configured to control an amount of boost pressure provided to the vapor canister, and a set of purge lines are connected between the vapor canister and at least one of the engine, an induction system of the engine, and an exhaust treatment system of the engine. A controller is configured to control the boost pressure control valve to control the boost pressure provided to the vapor canister to control an amount of fuel vapor forced from the vapor canister through at least one of the set of purge lines.