Post-Catalyst Air Injection for Exhaust Emission Control
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Solution Overview
Problem
Internal combustion engines operating under heavy load conditions produce undesirable non-stoichiometric combustion products and excess emissions, which are challenging to manage while meeting regulatory requirements and providing diagnosis and component protection.
Innovation Solution
An engine system employing a three-way catalytic converter followed by air injection and mixing, utilizing a bow-shaped mixing plate and substrate chamber with catalyst coatings to convert hydrocarbons and carbon monoxide into innocuous constituents, with air injection controlled by a controller based on engine load and exhaust gas parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine operates at richer conditions under heavy load, then component protection and diagnosis purposes are achieved, but non-stoichiometric combustion products and emissions increase
Solution Approach 1:
The patent extracts the air injection function from the traditional pre-catalyst position and places it downstream from the three-way catalytic converter. This allows the rich operation benefits (component protection, diagnosis) to be maintained while the harmful emissions are treated by the catalyst before the injected air completes the oxidation process in the oxidation chamber.
Solution Approach 2:
The three-way catalytic converter acts as an intermediary between the rich combustion process and the final exhaust emission. It partially converts the harmful compounds before the post-injected air completes the oxidation, mediating between the need for rich operation and emission control requirements.
2Stability of the object's composition
If a traditional air injection system is used upstream from the catalytic converter, then mixing is achieved, but the catalytic converter efficiency is reduced under rich operation
Solution Approach 1:
Instead of injecting air before the catalytic converter (traditional approach), the patent inverts the sequence by injecting air after the catalytic converter. This reversal allows the catalyst to work with the rich mixture first, then the injected air completes the oxidation process downstream where it cannot interfere with catalyst performance.
3Object-generated harmful factors
If exhaust air injection is implemented downstream from the three-way catalytic converter, then carbon monoxide conversion is enhanced, but system complexity increases
Solution Approach 1:
The exhaust air injection system serves multiple functions: it provides oxygen for complete oxidation of remaining CO and hydrocarbons, creates turbulence for enhanced mixing, and works synergistically with the three-way catalyst and oxidation chamber to achieve comprehensive emission control without requiring entirely separate systems.
4Stability of the object's composition
If a bow-shaped mixing plate is used to enhance mixing, then carbon monoxide conversion is improved, but manufacturing complexity increases
Solution Approach 1:
The mixing plate uses a bow-shaped (curved) geometry instead of a flat plate. This curvature creates more effective turbulence and mixing patterns as the exhaust gases flow over and around it, enhancing the oxidation process. The curved shape is manufacturable using standard forming processes despite being more complex than a flat plate.
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
Effectively reduces tailpipe emissions of hydrocarbons, carbon monoxide, and particulate matter under various load conditions, ensuring compliance with emission regulations and enhancing engine performance and component protection.
Implementation Method 1
A three-way catalytic converter is disposed in the exhaust system. The three-way catalytic converter converts hydrocarbons, carbon monoxide and nitrogen oxides to innocuous elements or compounds.
Implementation Method 2
A nozzle is configured to inject air into the exhaust system downstream from the three-way catalytic converter.
Implementation Method 3
The mixing plate is bow shaped with a concave shaped side facing the nozzle to enhance carbon monoxide conversion.
Implementation Method 4
An oxidation chamber is disposed downstream from the catalytic converter. An oxidation chamber is configured to convert carbon monoxide to carbon dioxide.
Data Source
AI summary
Engine systems use a three-way catalyst followed by air injection and mixing to convert all hydrocarbons and carbon monoxide under various load conditions when exhaust gas temperature is above 500 degrees Celsius. A three-way catalytic converter is disposed in the exhaust system. A nozzle is configured to inject air into the exhaust system downstream from the three-way catalytic converter. A mixing plate with or without catalyst coatings is disposed in the exhaust system downstream from the nozzle. The mixing plate is bow shaped with a concave shaped side facing the nozzle to enhance carbon monoxide conversion. Optional two way catalytic converters are added downstream from the mixing plate to further reduce tailpipe hydrocarbon and carbon monoxide emissions.