Cold-Start Evaporative Emissions Test via Dual Vapor Storage Segmentation
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Solution Overview
Problem
Existing methods for conducting evaporative emissions tests during cold-start events are challenged by the difficulty in distinguishing between undesired evaporative emissions and pressure bleed-up due to fuel vaporization, especially when the exhaust catalyst is below the temperature required for oxidation of hydrocarbons, leading to potential false indications of emissions.
Innovation Solution
A system and method that separates a first fuel vapor storage device from a second by a one-way vacuum-actuated check valve, routing fuel vapors from the fuel tank through the first device during cold-start events to adsorb vapors and prevent them from entering the intake manifold, allowing for an evaporative emissions test without increasing undesired emissions, and switching to the second device during other conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If evaporative emissions test is conducted during cold-start events, then fuel vaporization effects are minimized and test accuracy is improved, but exhaust catalyst temperature is below threshold causing undesired emissions
Solution Approach 1:
The vapor storage device is divided into two separate devices: a first fuel vapor storage device and a second fuel vapor storage device. This segmentation allows the system to route fuel vapors through different paths depending on operating conditions, enabling accurate testing during cold-start events while preventing undesired emissions during normal operation.
Solution Approach 2:
A one-way vacuum-actuated check valve is introduced as an intermediary component between the two vapor storage devices. This valve controls the flow of fuel vapors based on pressure differentials, allowing vapors to move from the first device to the second device during normal operation while preventing backflow during testing, thus resolving the contradiction between test accuracy and emission control.
2Measurement precision
If fuel vapors are routed through the first vapor storage device during cold-start, then test accuracy is improved, but fuel vapors may still enter the intake manifold causing emissions
Solution Approach 1:
The system extracts and separates the fuel vapor storage function into two distinct devices with different operational roles. The first device is used during cold-start events for testing, while the second device handles normal operation. This extraction prevents fuel vapors from entering the intake manifold during testing by isolating them in the first device, thus eliminating emissions while maintaining test accuracy.
Solution Approach 2:
The system dynamically switches between the first and second vapor storage devices based on operating conditions. During cold-start events, the first device is activated for testing, while during normal operation, the second device is used. This dynamic switching allows the system to adapt to different conditions, preventing emissions during testing while maintaining effective vapor management during normal operation.
3Device complexity
If a single vapor storage device is used, then device complexity is reduced, but inability to distinguish between vaporization effects and emissions occurs
Solution Approach 1:
The vapor storage system is segmented into two separate devices with distinct functions. This segmentation enables the system to distinguish between fuel vaporization effects and actual evaporative emissions by routing vapors through different paths. The first device handles testing during cold-start events, while the second device manages normal operation, thereby improving detection accuracy without excessive complexity.
Solution Approach 2:
The one-way vacuum-actuated check valve serves as an intermediary that controls the interaction between the two vapor storage devices. This intermediary component enables the system to distinguish between vaporization effects and emissions by allowing controlled flow between devices based on pressure differentials, thus improving measurement precision while maintaining reasonable system complexity.
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
Enables accurate evaporative emissions testing during cold-start events without complications from fuel vaporization, reducing the risk of false emissions indications and maintaining low exhaust emissions.
Implementation Method 1
routing fuel vapors from the fuel tank through the first fuel vapor storage device into an intake manifold of an internal combustion engine
Implementation Method 2
a one way vacuum-actuated check valve positioned between the first fuel vapor storage device and the second fuel vapor storage device
Data Source
AI summary
Methods and systems are provided for conducting an evaporative emissions test diagnostic on a vehicle fuel system and evaporative emissions control system during engine-on conditions. In one example, a first fuel vapor storage device is separated from a second fuel vapor storage device by a one-way check valve, thus preventing loading of the first fuel vapor storage device during conditions such as refueling operations, diurnal temperature fluctuations, or from running-loss vapors from a vehicle fuel tank. In this way, the evaporative emissions test diagnostic may be conducted during a cold-start event where an exhaust catalyst is below a predetermined threshold temperature required for catalytic oxidation of hydrocarbons in the engine exhaust, without increasing undesired exhaust emissions.