NOx Emission Control via NO2-Promoting EGR Mode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling nitrogen oxides (NOx) emissions in diesel engines, particularly in relation to passive regeneration of particulate filters, are insufficient due to reduced NO2 production when NOx emissions are minimized, leading to inefficient particulate filter regeneration and potential risks from high temperatures during active regeneration.
Innovation Solution
A method that adjusts the exhaust gas recirculation (EGR) rate to promote NO2 generation by simulating the effects of modified EGR rates on NO oxidation efficiency, ensuring increased NO2 production for improved passive regeneration of particulate filters, while maintaining efficient operation of downstream NOx after-treatment devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the EGR rate is reduced to increase NOx emissions, then NO2 production increases for passive regeneration, but the amount of fresh air entering the engine decreases and exhaust gas temperature changes significantly
Solution Approach 1:
The invention changes engine operating parameters (EGR rate, injection timing, injection quantity) in a coordinated manner to achieve the desired increase in NO2 production while maintaining exhaust gas temperature within acceptable ranges. Specifically, the controller is configured to adjust these parameters based on detected engine operating conditions to promote passive regeneration without causing excessive temperature fluctuations that would harm the exhaust aftertreatment system.
2Object-generated harmful factors
If the EGR rate is increased to minimize NOx emissions, then NOx emissions decrease, but the amount of NO2 produced in the DOC decreases making passive regeneration insufficient
Solution Approach 1:
The invention dynamically adjusts engine operating parameters based on detected conditions. When passive regeneration is needed, the controller modifies the EGR rate along with injection timing and quantity to increase NO2 production in the DOC. This allows the system to temporarily deviate from minimal NOx emission operation to enable effective passive regeneration of the particulate filter.
Solution Approach 2:
The system dynamically switches between different operating modes depending on the regeneration needs of the particulate filter. The controller continuously monitors engine operating conditions and adjusts parameters in real-time, enabling the engine to transition between normal emission-controlled operation and regeneration-promoting operation as needed.
3Reliability
If active regeneration is performed by injecting additional fuel to heat up to soot combustion temperatures, then soot is burned off, but the temperature reaches about 600°C which requires precise control to avoid damage
Solution Approach 1:
The invention promotes passive regeneration where the particulate filter regenerates itself using NO2 produced during normal engine operation, without requiring additional fuel injection or external heating. The system utilizes the engine's own exhaust gas composition and temperature to enable spontaneous oxidation of soot by NO2 in the particulate filter, eliminating the need for active regeneration interventions.
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 enhances passive regeneration efficiency, reducing the need for fuel injection during active regeneration and minimizing risks to particulate filters, while ensuring effective NOx treatment, even at low engine duty cycles.
Implementation Method 1
a proportion of nitrogen oxide (NO) contained in the exhaust stream is oxidized into nitrogen dioxide (NO 2 )
Implementation Method 2
an oxidation reaction occurs between NO 2 (mainly formed in the DOC) and soot, according to the formula: 2 NO 2 + C → 2 NO + CO 2
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A method of controlling NOx emissions in an internal combustion engine is proposed, wherein the engine comprises an exhaust system with oxidation - promoting catalyst means (22) having a NO oxidation efficiency, and wherein the engine is normally operated on a map of normal EGR rates. The engine is operable in a NO2-promoting mode that comprises the steps of: determining whether operating the engine under a modified EGR rate would lead to an increased generation of NO2, said determination taking into account the variability of the NO oxidation efficiency with the oxidation temperature and the exhaust flow rate; and using the modified EGR rate for engine control in case it leads to an increased NO2 generation.