Charge Air Reducing Agent Injection for Exhaust NOx Reduction
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Solution Overview
Problem
Internal combustion engines face challenges in enriching exhaust gases with reducing agents to effectively reduce nitrogen oxides, particularly due to thermal overload issues and the inefficiency of existing methods that require additional fuel injection, which can lead to increased fuel consumption and combustion instability.
Innovation Solution
A method is introduced to enrich the exhaust gas with a reducing agent in the exhaust gas discharge system upstream of the exhaust gas aftertreatment system when the engine is not under load, utilizing residual heat and reducing agent introduction into the charge air rather than the hot exhaust gas, thereby avoiding thermal overload and minimizing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional fuel is injected into the exhaust gas to enrich it with reducing agents, then nitrogen oxide reduction is improved, but thermal overload of the exhaust system occurs and fuel consumption increases
Solution Approach 1:
The reducing agent is injected into the charge air before combustion occurs, allowing the exhaust gas to be enriched with reducing agents during the combustion process itself, rather than adding fuel to the already hot exhaust gas afterward
Solution Approach 2:
The invention uses the main combustion process to create a copy effect where the charge air, enriched with reducing agents, becomes part of the exhaust gas, effectively enriching the exhaust without direct fuel injection into the hot exhaust stream
2Reliability
If post-injection of fuel is used to enrich exhaust gas with unburned hydrocarbons, then nitrogen oxide reduction is improved, but oil dilution and increased fuel consumption occur
Solution Approach 1:
The charge air injection system serves multiple functions: it provides oxygen for combustion, enriches the exhaust with reducing agents, and enables regeneration of the aftertreatment system without requiring separate fuel injection systems
Solution Approach 2:
The system uses the engine's own charge air and combustion process to generate the reducing agents needed for nitrogen oxide reduction, rather than requiring external fuel injection into the exhaust stream
3Reliability
If sub-stoichiometric operation is used to enable nitrogen oxide reduction, then exhaust gas enrichment with reducing agents is improved, but combustion stability deteriorates at low loads
Solution Approach 1:
The system dynamically adjusts the air ratio by controlling charge air quantity and composition rather than relying on fixed sub-stoichiometric operation, allowing combustion stability to be maintained while still enabling nitrogen oxide reduction when needed
Solution Approach 2:
The invention changes the composition of the charge air by enriching it with reducing agents before combustion, rather than changing the overall air ratio, thereby enabling nitrogen oxide reduction while maintaining stable combustion conditions
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 allows for efficient nitrogen oxide reduction without exposing the exhaust system to excessive temperatures, reducing fuel consumption, and maintaining combustion stability, while also reducing the frequency of internal engine measures for enrichment, thus enhancing the operational efficiency and longevity of exhaust aftertreatment devices.
Implementation Method 1
a device for introducing reducing agent into the charge air fed through the internal combustion engine and into the exhaust gas discharge system is provided
Implementation Method 2
catalytic reactors are used, which ensure oxidation of HC and CO even at low temperatures by using catalytic materials which increase the speed of certain reactions
Implementation Method 3
utilizing residual heat and reducing agent introduction into the charge air rather than the hot exhaust gas, thereby avoiding thermal overload
Data Source
AI summary
A method for enriching the exhaust gas of an internal combustion engine with a reducing agent is provided, the internal combustion engine including at least one cylinder and having an intake system for admission of charge air, an exhaust gas discharge system for discharging exhaust gases, and at least one exhaust gas aftertreatment system for reducing nitrogen oxides arranged in the exhaust gas discharge system and which is periodically provided with a supply of reducing agent. The method comprises enriching the exhaust gas with the reducing agent in the exhaust gas discharge system upstream of at least the one exhaust gas aftertreatment system when a fuel supply of the at least one cylinder of the internal combustion engine is deactivated due to an absence of load demand.