Urea Injection Control for SCR Catalyst Deposit Reduction
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Solution Overview
Problem
Diesel vehicles' aftertreatment systems face issues with urea deposition, leading to reduced NOx conversion efficiency, increased urea consumption, and white smoke due to improper urea injection amounts, which are either too low or too high.
Innovation Solution
A method for controlling urea injection in the SCR catalyst based on soot production levels, adjusting the amount during decreased and increased soot production phases to optimize urea economy and NOx conversion efficiency, and adjusting regeneration parameters to remove accumulated urea deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection amount of urea is increased to improve NOx conversion efficiency, then NOx conversion efficiency is improved, but urea deposits accumulate in the system which decrease NOx efficiency and increase urea slip
Solution Approach 1:
The patent applies dynamics by making the urea injection amount variable rather than fixed. The injection amount is dynamically adjusted based on real-time operating conditions including soot generation rate, exhaust temperature, and exhaust flow rate. This allows the system to optimize NOx conversion efficiency while preventing urea deposit accumulation by reducing injection when conditions favor deposition.
Solution Approach 2:
The patent changes multiple parameters simultaneously to resolve the contradiction. It adjusts urea injection amount based on soot generation rate, exhaust temperature, and exhaust flow rate. By monitoring and responding to changes in these parameters, the system maintains optimal urea injection levels that prevent deposit formation while ensuring sufficient NOx conversion.
2Loss of substance
If the injection amount of urea is decreased to reduce urea deposits, then urea deposit accumulation is reduced, but NOx conversion efficiency becomes too low to meet regulation standards
Solution Approach 1:
The patent implements feedback control by continuously monitoring operating conditions such as soot generation rate, exhaust temperature, and exhaust flow rate, and using this information to adjust urea injection amount. This closed-loop control ensures that injection is increased when conditions support high conversion efficiency and decreased when conditions favor deposit formation, maintaining optimal performance continuously.
Solution Approach 2:
The system dynamically adjusts injection based on real-time feedback from sensors monitoring soot generation, temperature, and flow rate. This dynamic response allows the system to prevent deposit accumulation while maintaining sufficient NOx conversion efficiency across varying operating conditions.
3Productivity
If too much urea is injected to maintain NOx conversion efficiency, then NOx conversion efficiency is maintained, but urea consumption increases thereby reducing urea economy
Solution Approach 1:
The patent optimizes urea consumption by adjusting injection amount based on multiple parameters including soot generation rate, exhaust temperature, and exhaust flow rate. By responding to changes in these parameters, the system injects only the necessary amount of urea required for effective NOx conversion, avoiding excessive consumption while maintaining regulatory compliance.
4Productivity
If urea injection is increased to improve NOx conversion, then NOx conversion efficiency is improved, but white smoke increases in the exhaust at high temperatures when the deposit is decomposed and released
Solution Approach 1:
The patent applies preliminary anti-action by preventing urea deposit formation in the first place through dynamic injection control. By adjusting injection amount based on operating conditions before deposits can accumulate, the system eliminates the source of white smoke that would later be generated during deposit decomposition, rather than merely treating the symptom.
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 reduces urea deposits, increases NOx conversion efficiency, and minimizes white smoke by optimizing urea injection levels in relation to soot generation, thereby improving urea economy and aftertreatment system performance.
Implementation Method 1
a selective catalytic reduction (SCR) system
Implementation Method 2
a diesel particulate filter
Implementation Method 3
when the deposit is decomposed and released
Data Source
AI summary
Various systems and methods are described for controlling a diesel aftertreatment system coupled to an exhaust system of an engine which includes a selective catalytic reduction (SCR) catalyst and a diesel particulate filter (PF). In one example, a threshold amount of urea injected to the SCR catalyst is adjusted based on an amount of soot generated by the engine and the total amount of urea injected to the SCR catalyst is limited by the threshold.