Evaporative Emission Mitigation System with Membrane Module
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Solution Overview
Problem
Existing evaporative emission mitigation systems for motor vehicles, particularly hybrid vehicles, face challenges in efficiently capturing hydrocarbon vapors at low concentrations and addressing emissions that are not sequestered or spontaneously desorbed from adsorbent materials, due to intermittent engine operation and less frequent purging.
Innovation Solution
An evaporative emission mitigation system incorporating a membrane module that separates gaseous hydrocarbon fuel vapors from inert air components using a solution-diffusion mechanism, paired with a conventional adsorbent canister, where the membrane module continuously evacuates the permeated hydrocarbons to maintain separation efficiency and return them to the canister for adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single adsorbent canister is used, then the system structure is simple, but the capture efficiency at low vapor concentrations is insufficient
Solution Approach 1:
The single canister is segmented into two functional zones: an upstream zone with high-capacity adsorbent for high concentration vapors and a downstream zone with low-concentration optimized adsorbent for residual vapors. This segmentation allows each zone to specialize in capturing vapors at different concentration levels, improving overall capture efficiency without adding multiple separate canisters.
Solution Approach 2:
Different adsorbent materials or configurations are placed in different locations within the canister based on local vapor concentration requirements. The upstream portion uses adsorbent optimized for high-concentration capture while the downstream portion uses adsorbent optimized for low-concentration capture, creating local quality variations that address the specific needs of each zone.
2Reliability
If a second adsorbent capture element is added downstream, then the capture efficiency at low concentrations is improved, but the device complexity increases
Solution Approach 1:
Two functional capture elements are merged into a single canister structure, combining the functions of high-concentration capture and low-concentration capture in one integrated component. This merging achieves the capture efficiency benefits of a two-canister system while maintaining the structural simplicity of a single canister.
Solution Approach 2:
The downstream low-concentration capture element is nested within the same canister housing as the upstream high-concentration capture element. The canister is designed with internal partitions or flow channels that allow both capture zones to coexist in a nested arrangement, maximizing space utilization and maintaining compact structure.
3Loss of energy
If the engine operates intermittently in hybrid vehicles, then fuel economy is improved, but the purging frequency decreases leading to vapor accumulation
Solution Approach 1:
The adsorbent canister continuously captures and stores hydrocarbon vapors during periods when the engine is not running, performing the vapor capture action in advance before the engine becomes available for purging. This preliminary action prevents vapor accumulation and emission during extended idle periods between engine operations.
Solution Approach 2:
The adsorbent canister provides continuous vapor capture functionality regardless of engine operation status, maintaining uninterrupted vapor sequestration during both engine-on and engine-off periods. The system ensures continuous useful action by decoupling the vapor capture function from the engine operation cycle, allowing vapor mitigation to proceed continuously even when the engine is idle.
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 system effectively reduces the environmental release of fuel vapors by efficiently capturing residual hydrocarbon vapors that were not initially adsorbed or have desorbed from the canister, enhancing overall emission mitigation efficiency beyond conventional systems.
Implementation Method 1
The membranes within the disclosed evaporative emission mitigation system separate gaseous hydrocarbon fuel vapors from inert air components, e.g. oxygen and nitrogen, via a solution-diffusion mechanism
Implementation Method 2
The membranes used in these systems are selectively permeable to hydrocarbon vapors, providing a method for separating the gaseous hydrocarbons from inert air components
Implementation Method 3
a canister packed with an adsorbent material, such as activated carbon... engineered to efficiently sequester hydrocarbon vapors entering the canister
Implementation Method 4
the membrane is used to concentrate the hydrocarbon vapors before passing them on to a condenser, with the condensate ultimately being returned to the fuel tank
Data Source
AI summary
An improved evaporative emission mitigation system for a motor vehicle includes a canister filled with an adsorbent material connected to a membrane module. The membrane module contains a membrane that separates gaseous hydrocarbons from inert air components within fuel vapor generated by the evaporation of fuel due to the heating of the motor vehicle. The gaseous hydrocarbons separated by the membrane are returned to the canister, where they will again be adsorbed by the adsorbent material. The inert air components are vented from the membrane module into the open atmosphere outside of the motor vehicle.