Segmented Adsorbent Canister for Low Emissions
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Solution Overview
Problem
Current evaporative emission control systems face challenges in achieving high working capacity while maintaining low diurnal breathing loss (DBL) emissions, particularly in hybrid vehicles and other powertrain designs where purge frequency and volume are limited, leading to increased hydrocarbon emissions.
Innovation Solution
A shaped adsorbent material with a high ASTM Butane Working Capacity (BWC) of at least 13 g/dL, composed of an activated adsorbent powder bound with a binder such as carboxymethyl cellulose (CMC) or bentonite clay, with a pore volume ratio of 0.05-1 micron to 0.05-100 microns greater than 80%, is used in both fuel-side and vent-side adsorbent volumes within the canister system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high working capacity activated carbon is used to increase adsorption capacity, then the system can handle higher vapor loads, but diurnal breathing loss emissions increase due to limited purge frequency and volume
Solution Approach 1:
The canister is divided into two distinct adsorbent zones: a fuel-side zone containing high BWC activated carbon for maximum vapor capture, and a vent-side zone containing low DBL activated carbon for emission control. This segmentation allows each zone to perform its specialized function optimally, resolving the contradiction between high working capacity and low emissions.
Solution Approach 2:
Different regions of the canister are assigned different adsorbent materials with tailored properties. The fuel-side region uses high BWC carbon for adsorption efficiency, while the vent-side region uses low DBL carbon for emission suppression. This local differentiation of material properties enables simultaneous optimization of both working capacity and emissions performance.
2Object-generated harmful factors
If purge frequency and volume are increased to reduce DBL emissions, then emissions performance improves, but system complexity and energy consumption increase
Solution Approach 1:
The vent-side adsorbent zone continuously suppresses DBL emissions through passive adsorption without requiring active purge operations. The low DBL properties of this zone provide automatic emissions control during diurnal temperature cycles, eliminating the need for complex purge scheduling and reducing system operational complexity.
3Volume of moving object
If canister size is reduced to improve compactness, then space efficiency increases, but working capacity decreases
Solution Approach 1:
The canister employs a composite adsorbent structure combining two types of activated carbon with complementary properties. The fuel-side high BWC carbon maximizes vapor uptake per unit volume, while the vent-side low DBL carbon maintains emission control. This composite approach achieves high working capacity in a compact volume by optimizing the functional contribution of each material.
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
The solution enables the design of more compact, cost-effective evaporative emission control systems that demonstrate lower DBL emissions, as evidenced by DBL emissions of 100 mg or less under standard test procedures, even at low purge volumes, thereby addressing the dilemma of high working capacity and low emissions performance.
Implementation Method 1
a more space efficient activated carbon adsorbent for this application is characterized by an n-butane vapor adsorption isotherm that has adsorption capacity steeply sloped towards high vapor partial pressures
Implementation Method 2
the adsorbent favors release of these captured vapors when exposed to a low vapor concentration or partial pressure, such as during purge
Data Source
AI summary
The present description provides high working capacity adsorbents with low DBL bleed emission performance properties that allows the design of evaporative fuel emission control systems that are lower cost, simpler and more compact than those possible by prior art. Emission control canister systems comprising the adsorbent material demonstrate a relatively high gasoline working capacity, and low emissions.