Electric Heated Catalyst for Lean NOx Trap Temperature Control
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Solution Overview
Problem
The existing aftertreatment systems for internal combustion engines, particularly those with lean nitrogen-oxides traps (LNT), face challenges in maintaining efficiency and minimizing fuel consumption during regeneration events, especially under cold start conditions and low temperatures, leading to NOx slip and increased fuel penalty.
Innovation Solution
The method involves using an electric heated catalyst (eHC) upstream of the LNT, activated based on predetermined threshold conditions of storage efficiency and exhaust gas temperature, to optimize regeneration events by warming up the LNT and reducing fuel consumption, while avoiding NOx slip during rich purges and minimizing the frequency of denitrification events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the engine is switched to rich-combustion mode for LNT regeneration, then NOx stored on the LNT is desorbed and converted to nitrogen and ammonia, but fuel consumption increases
Solution Approach 1:
The system changes the temperature parameter by activating the electric heated catalyst to warm up the LNT before regeneration, allowing the regeneration process to occur at optimal temperature conditions that improve conversion efficiency and reduce the fuel penalty associated with rich-combustion mode
2Adaptability or versatility
If the LNT is operated during cold start conditions, then the system can function under various operating conditions, but the LNT temperature is insufficient for efficient NOx reduction
Solution Approach 1:
The electric heated catalyst is activated in advance to warm up the LNT to the optimal temperature range before regeneration events are initiated, ensuring that the LNT is ready to efficiently reduce NOx even during cold start conditions or low exhaust temperature scenarios
Solution Approach 2:
The electric heated catalyst acts as an intermediary device that transfers thermal energy to the LNT, enabling the LNT to reach optimal operating temperature without requiring the entire exhaust system to be hot, thus bridging the gap between cold start conditions and efficient NOx reduction
3Reliability
If denitrification events are performed frequently to maintain LNT efficiency, then NOx conversion efficiency is maintained, but fuel penalty increases
Solution Approach 1:
By changing the temperature parameter through eHC activation, the system extends the operational life of the LNT between regeneration events, allowing longer intervals between denitrification events while maintaining conversion efficiency, thus reducing the cumulative fuel penalty from frequent regeneration cycles
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 NOx reduction with lower fuel consumption during regeneration events, even under cold start conditions, by optimizing the LNT's temperature and reducing the frequency of denitrification, thereby minimizing fuel penalty and NOx slip.
Implementation Method 1
an electric heated catalyst (eHC), activated based on predetermined threshold conditions of storage efficiency and exhaust gas temperature, to optimize regeneration events by warming up the LNT
Implementation Method 2
a lean nitrogen-oxides trap (LNT) where a NOx adsorbent material, such as a zeolite, is disposed
Implementation Method 3
the NOx stored on adsorbent sites of the LNT reacts with reductants contained in the exhaust gas, such as unburned Hydrocarbons (HC), and are desorbed and converted to nitrogen (N2) and ammonia (NH3)
Data Source
AI summary
A method and system for operating an aftertreatment system of an internal combustion engine is disclosed. A value of a storage efficiency for the lean nitrogen-oxide trap is determined. A value of an exhaust gas temperature is measured upstream of the lean nitrogen-oxide trap. An electric heated catalyst enabling condition may be fulfilled if the storage efficiency of the lean nitrogen-oxide trap is smaller than a threshold value thereof and the value of the exhaust gas temperature upstream of the lean nitrogen-oxide trap is greater than a lower threshold value and less than an upper threshold value. The electric heated catalyst is activated if the enabling condition is fulfilled. An inhibition enabling condition may be fulfilled if the value of storage efficiency is less than a second threshold value and the electric heated catalyst is deactivated and a denitrification of the lean nitrogen-oxides trap is started.