Evaporative Canister Adsorbent Pore Structure for Low DBL Emissions
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Solution Overview
Problem
Current evaporative emission control systems face challenges in achieving low diurnal breathing loss (DBL) emissions and maintaining working capacity over the life of a vehicle, due to high vapor retention and flow restriction issues with conventional particulate adsorbents, especially in high-performance and hybrid engine designs.
Innovation Solution
The use of particulate adsorbent materials with a macroporosity to microporosity ratio greater than 150%, low butane retentivity, and a length-to-diameter ratio of 2 or more, which are cost-effective, robust, and provide low flow restriction, allowing for effective DBL emissions control even under low purge conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional particulate adsorbents are used, then vapor adsorption capacity is improved, but flow restriction increases and diurnal breathing loss emissions worsen
Solution Approach 1:
The patent applies porous materials by specifying adsorbents with controlled pore size distributions, including micropores (0.001-0.006 micrometers) and mesopores (0.006-0.06 micrometers), to achieve optimal balance between vapor adsorption capacity and flow restriction characteristics, thereby reducing diurnal breathing loss emissions while maintaining working capacity
Solution Approach 2:
The patent applies parameter changes by optimizing specific physical parameters of the adsorbent including pore size distribution, particle diameter (0.2-2.0 mm), and surface area (500-1500 m²/g), to resolve the contradiction between high vapor capacity and low flow restriction, achieving compliance with stringent DBL emission standards
2Object-generated harmful factors
If higher purge volumes are used, then DBL emissions are reduced, but working capacity over vehicle life deteriorates due to vapor retention
Solution Approach 1:
The patent replaces the mechanical approach of using high purge volumes with a material-based solution, utilizing adsorbents with specific pore size distributions and surface properties that inherently reduce vapor retention and DBL emissions without requiring excessive purge, thereby preserving working capacity over the vehicle lifecycle
Solution Approach 2:
The patent applies composite materials by combining adsorbent materials with complementary pore structures and surface characteristics, creating a multi-functional adsorbent that simultaneously achieves low vapor retention, low DBL emissions, and maintained working capacity without requiring high purge volumes
3Quantity of substance
If particulate adsorbents with high microporosity are used, then vapor adsorption is improved, but flow restriction increases
Solution Approach 1:
The patent applies porous materials with a balanced pore size distribution including both micropores (0.001-0.006 μm) for vapor adsorption and mesopores (0.006-0.06 μm) for fluid flow, achieving optimal balance between vapor adsorption capacity and flow restriction characteristics
Solution Approach 2:
The patent uses composite adsorbent materials that integrate different pore structures, combining the high surface area of microporous materials with the flow-friendly characteristics of mesoporous materials, thereby simultaneously improving vapor adsorption while maintaining low flow restriction
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
These adsorbent systems achieve DBL emissions of less than 50 mg or 20 mg with low volumes of purge, maintaining performance and reducing vapor retention, thus meeting stringent regulatory standards while minimizing flow restriction and production complexity.
Implementation Method 1
the adsorbed fuel vapor is periodically removed from the activated carbon by purging the canister systems with ambient air to desorb the fuel vapor from the activated carbon
Implementation Method 2
the adsorbed fuel vapor is periodically removed from the activated carbon by purging the canister systems with ambient air to desorb the fuel vapor from the activated carbon
Data Source
AI summary
The present disclosure describes an evaporative emission control canister system that includes: one or more canisters comprising at least one vent-side particulate adsorbent volume comprising a particulate adsorbent having microscopic pores with a diameter of less than about 100 nm; macroscopic pores having a diameter of about 100-100,000 nm; and a ratio of a volume of the macroscopic pores to a volume of the microscopic pores that is greater than about 150%, and having a retentivity of about 1.0 g/dL or less. The system may further include a high butane working capacity adsorbent. The disclosure also describes a method for reducing emissions in an evaporative emission control system.