Dual-Stage Exhaust Aftertreatment with Intercooler and Air Ejector
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Solution Overview
Problem
Existing exhaust aftertreatment systems for internal combustion engines fail to effectively reduce particulate matter, hydrocarbons, and nitrogen oxides, particularly due to the high operating temperatures of catalytic converters causing NOx reforming and the inability to remove volatile hydrocarbon condensables in their gaseous form.
Innovation Solution
An exhaust aftertreatment system comprising a first catalytic converter, an exhaust gas intercooler to cool the exhaust to 300° F. to 500° F., and a second catalytic converter with a gas particulate filter, where compressed air is introduced into the exhaust conduit to increase oxygen concentration and promote oxidation reactions, along with a method for regenerating the gas particulate filter by temporarily increasing exhaust temperature during idling or coasting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high operating temperatures are used in catalytic converters to improve conversion efficiency, then oxidation and reduction reactions are enhanced, but nitrogen oxide reforming occurs which is undesirable
Solution Approach 1:
The catalytic converter is divided into two separate stages: a first catalytic converter for NOx reduction at high temperatures, and a second catalytic converter for CO and hydrocarbon oxidation at lower temperatures. This segmentation allows each stage to operate at its optimal temperature range, preventing NOx reforming while maintaining high conversion efficiency for all pollutants.
2Productivity
If standard exhaust aftertreatment systems are used, then gaseous pollutants are converted, but volatile hydrocarbon condensables in gaseous form cannot be removed
Solution Approach 1:
The system changes the temperature parameter of the exhaust gas by cooling it from high operating temperatures to between 300-500°F. This temperature reduction causes volatile hydrocarbon condensables to transition from gaseous to liquid or solid phase, enabling their removal by the gas particulate filter in the second catalytic converter stage.
3Productivity
If compressed air is introduced into the exhaust conduit to increase oxygen concentration, then oxidation reactions are promoted, but system complexity increases
Solution Approach 1:
The compressor is designed to serve dual functions: it provides compressed air to the engine intake for combustion, and simultaneously supplies compressed air to the exhaust conduit for promoting oxidation reactions. This multi-functionality increases oxidation efficiency without adding separate dedicated equipment, thereby minimizing system complexity.
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 configuration enhances the removal of particulate matter and hydrocarbons by condensing volatile hydrocarbons into liquids or solids, reduces nitrogen oxide formation, and improves engine efficiency by minimizing back pressure and promoting oxidation reactions, thereby meeting emissions standards and enhancing engine performance.
Implementation Method 1
cooling the exhaust gases to between 300° F. to 500° F. causes at least a portion of the volatile hydrocarbon condensables to undergo a phase change into a liquid
Implementation Method 2
The second stage catalytic converter promotes oxidation reactions that convert carbon monoxide and unburned hydrocarbons into carbon dioxide and water
Implementation Method 3
The first stage catalytic converter promotes reduction reactions that convert nitrogen oxide compounds into nitrogen and oxygen
Data Source
AI summary
An exhaust aftertreatment system includes a first stage catalytic converter, a second stage catalytic converter, and a conduit extending from the first stage catalytic converter to the second stage catalytic converter. The conduit passes through an exhaust gas intercooler, between the first and second stage catalytic converts, that reduces the temperature of the exhaust to about 300° F. to about 500° F. Air is ejected into the exhaust conduit to increase the oxygen concentration in the exhaust before it passes through the second stage catalytic converter. The air can be ejected from an air ejection conduit that extends to an engine charger compressor or a compressed air conduit that extends from the engine charger compressor, such as a turbo charger and/or a supercharger, to the engine. A gas particulate filter can be disposed in the exhaust conduit or it can be integrated with the second stage catalytic converter, for example as a catalyzed gas particulate filter.