Bypass Catalyst Diagnostic System for Fast Cold Start
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional engine exhaust aftertreatment systems face challenges in achieving low tailpipe emissions immediately after a cold engine start due to low catalyst conversion efficiency, often requiring faster light-off temperatures at the cost of backpressure, durability, longevity, and complexity.
Innovation Solution
The system incorporates a light-off catalyst bypass system with a bypass catalytic converter and valve that directs exhaust gas through a bypass catalyst located close to the cylinder head, allowing rapid heating and efficient conversion of harmful constituents before the main catalyst reaches light-off temperature, along with a diagnostic method using oxygen sensors to monitor and determine the efficiency and useful life of the bypass catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the catalyst is designed to achieve faster light-off temperature, then the conversion efficiency during cold start is improved, but the exhaust system backpressure increases and durability decreases
Solution Approach 1:
The exhaust aftertreatment system is segmented into two separate catalytic converters: a bypass catalytic converter positioned near the cylinder head for cold start emissions control, and a main catalytic converter for normal operation. This segmentation allows each catalyst to be optimized for its specific function without compromising the other, resolving the contradiction between fast light-off performance and durability.
2Productivity
If the catalyst is designed to achieve faster light-off temperature, then the conversion efficiency during cold start is improved, but the exhaust system complexity increases
Solution Approach 1:
A bypass valve is incorporated into the exhaust system that dynamically routes exhaust flow between the bypass catalytic converter and the main catalytic converter based on operating conditions. During cold start, the valve directs exhaust through the bypass catalyst; during normal operation, it routes exhaust through the main catalyst. This dynamic switching capability allows the system to achieve fast cold start light-off without permanently increasing system complexity.
3Loss of time
If the bypass catalytic converter is used during cold start, then the light-off time is reduced, but the precious metal usage increases
Solution Approach 1:
The bypass catalytic converter is designed to handle only the cold start phase emissions, which is a partial application period. By limiting the bypass catalyst's function to cold start operation only (partial action), the system achieves fast light-off performance when needed without requiring excessive precious metal content in both catalysts, as the main catalyst handles the bulk of normal operation emissions.
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 approach enables extremely fast catalyst light-off, high conversion efficiency, reduced precious metal usage, and extended catalyst life by selectively activating the bypass catalyst only during cold starts, thereby improving emissions compliance and reducing degradation.
Implementation Method 1
a bypass catalytic converter configured to selectively receive exhaust gas from the internal combustion engine... high conversion efficiency
Implementation Method 2
a first oxygen sensor disposed upstream of the bypass catalytic converter, and a second oxygen sensor disposed downstream of the bypass catalytic converter... signals from the first and second oxygen sensors are voltage signals indicating an oxygen content of the exhaust gas
Data Source
AI summary
An internal combustion engine system includes an internal combustion engine, a main exhaust aftertreatment system with a main catalytic converter, and a light-off catalyst bypass system with a bypass passage and a bypass catalytic converter. An emissions control system includes a controller in signal communication with a first oxygen sensor disposed upstream of the bypass catalytic converter, and a second oxygen sensor disposed downstream. The emissions control system performs a diagnostic of the bypass catalytic converter, by the controller, including (i) monitoring signals from the first and second oxygen sensors for a predetermined time period during an engine cold start condition, (ii) determining a ratio of oxygen content at the second oxygen to the first oxygen sensor based on the signals from the first and second oxygen sensors, and (iii) comparing the determined ratio to a predetermined threshold ratio to determine if the bypass catalytic converter has failed.