Air Dithering for Engine Exhaust Gas Control
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Solution Overview
Problem
Conventional internal combustion engine systems face challenges in achieving responsive, predictable, and precise adjustments to the air-to-fuel ratio in the exhaust gas stream, particularly due to delays and inconsistencies caused by the distance and complexity between fuel injection points and oxidation catalysts, leading to suboptimal engine performance and increased emissions.
Innovation Solution
An air dithering system that injects air directly into the exhaust gas stream upstream of the oxidation catalyst, allowing for faster and more precise adjustments to the air-to-fuel ratio, reducing the impact on combustion events and maintaining a rich operating environment for the engine while ensuring the oxidation catalyst receives sufficient oxygen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fuel is injected into the air intake stream upstream of the combustion cylinders, then the air-to-fuel ratio in the exhaust gas can be adjusted, but the responsiveness is delayed due to the long distance and high number of components between the fuel injection site and the oxidation catalyst
Solution Approach 1:
The patent introduces air injection as an intermediary mechanism in the exhaust stream to adjust the air-to-fuel ratio. By injecting air directly into the exhaust gas downstream of the engine and upstream of the oxidation catalyst, the system achieves rapid air-to-fuel ratio adjustments without the delays associated with upstream fuel injection, while still achieving the desired exhaust treatment效果
Solution Approach 2:
Instead of adjusting the air-to-fuel ratio by controlling fuel injection upstream (conventional approach), the patent inverts the approach by injecting air into the exhaust stream downstream. This reversal eliminates the delay caused by the long path from upstream fuel injection to the oxidation catalyst, achieving responsive control while maintaining engine combustion stability
2Measurement precision
If smaller fuel injectors are positioned at various locations within the air intake system for fuel dithering, then more precise adjustments to the air-to-fuel ratio can be achieved, but the complexity of the system increases
Solution Approach 1:
The patent extracts the air-to-fuel ratio adjustment function from the complex upstream fuel injection system and relocates it to a simpler air injection system in the exhaust stream. This extraction eliminates the need for multiple small fuel injectors positioned at various locations in the air intake system, reducing system complexity while maintaining precise control capability
Solution Approach 2:
The patent uses air injection as an intermediary to achieve precise air-to-fuel ratio adjustments without requiring complex fuel injection hardware. By injecting controlled amounts of air into the exhaust stream, the system achieves dithering-level precision with a simpler, more reliable mechanism
3Measurement precision
If fuel dithering is performed upstream of the combustion cylinders, then the air-to-fuel ratio in the exhaust gas can be adjusted, but the combustion events in the cylinders are negatively impacted
Solution Approach 1:
The patent segments the air-to-fuel ratio control function from the combustion process. By performing air injection in the exhaust stream rather than in the intake stream, the system separates the exhaust gas composition control from the combustion event control, allowing precise air-to-fuel ratio adjustments without interfering with combustion stability
Solution Approach 2:
The patent uses the exhaust stream as an intermediary zone to perform air-to-fuel ratio adjustments. This intermediary location allows the system to modify exhaust gas composition without directly affecting the combustion process in the cylinders, thereby maintaining combustion stability while achieving precise control
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 air dithering system enhances the responsiveness and consistency of air-to-fuel ratio adjustments, improving engine efficiency and reducing emissions by directly influencing the exhaust gas stream closer to the oxidation catalyst, thus overcoming the limitations of conventional fuel dithering techniques.
Implementation Method 1
an air injector in air injecting communication with exhaust gas in the exhaust line at a location downstream of the internal combustion engine and upstream of the exhaust aftertreatment component
Implementation Method 2
An oxidation catalyst utilizes oxygen in the exhaust gas stream to oxidize carbon monoxide into carbon dioxide and/or oxidize (e.g., burn) unburned hydrocarbons. During lean exhaust conditions (e.g., higher than a 1:1 air-to-fuel ratio), excess oxygen not used to oxidize carbon monoxide or unburned hydrocarbons can be stored on the walls of the catalyst
Implementation Method 3
An oxidation catalyst utilizes oxygen in the exhaust gas stream to oxidize carbon monoxide into carbon dioxide and/or oxidize (e.g., burn) unburned hydrocarbons
Data Source
AI summary
Described herein is an air dithering system for an internal combustion engine generating exhaust gas that includes an exhaust line in exhaust gas receiving communication with the internal combustion engine. The system also includes an exhaust aftertreatment component positioned within the exhaust line in exhaust gas receiving communication with exhaust gas in the exhaust line. Further, the system includes an air injector in air injecting communication with exhaust gas in the exhaust line at a location downstream of the internal combustion engine and upstream of the exhaust aftertreatment component.