SCR Coating Reduction via Periodic Exhaust Temperature Control
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Solution Overview
Problem
SCR systems in vehicles experience coating build-ups, such as urea crystals, which can affect engine performance and lead to increased nitrogen oxide emissions when the coating is reduced, especially during static conditions with low exhaust temperatures.
Innovation Solution
A method that controls the nitrogen oxide content in the exhaust flow by raising the exhaust temperature and halting additive supply, while monitoring downstream NOx levels to take remedial measures, such as adjusting engine delivery or additive dosing, to maintain acceptable emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If additive is supplied to reduce nitrogen oxides in the exhaust flow, then nitrogen oxide emissions are reduced, but coating build-up occurs in the post-treatment system
Solution Approach 1:
The system alternates between normal operation mode (additive supply enabled, nitrogen oxide reduction active) and coating reduction mode (additive supply halted, high exhaust temperature maintained to burn off coatings). This periodic switching resolves the contradiction by temporarily suspending nitrogen oxide reduction to eliminate harmful coating accumulations, then resuming normal operation.
Solution Approach 2:
The system changes operational parameters by halting additive supply and maintaining high exhaust temperature during coating reduction periods. This parameter change temporarily shifts the system from nitrogen oxide reduction mode to coating elimination mode, resolving the contradiction between reducing emissions and preventing coating build-up.
2Reliability
If exhaust temperature is raised to reduce coating build-up, then crystal formations are reduced, but nitrogen oxide emissions increase
Solution Approach 1:
The system implements periodic switching between normal operation (lower temperature, additive supply active) and coating reduction mode (high temperature, additive supply halted). During brief high-temperature intervals, nitrogen oxide emissions increase temporarily as coatings are burned off, but the system quickly returns to normal operation where emissions are controlled, thus resolving the contradiction over time.
Solution Approach 2:
The system performs rapid, brief high-temperature excursions to burn off coatings before nitrogen oxide emissions can accumulate to problematic levels. By skipping quickly through the high-emission state and returning to normal operation, the system minimizes the duration of increased emissions while still achieving coating reduction.
3Reliability
If additive supply is halted to reduce coatings, then crystal build-up is prevented, but nitrogen oxide reduction capability is lost
Solution Approach 1:
The system periodically halts additive supply to perform coating reduction, accepting temporary loss of nitrogen oxide reduction capability during these brief intervals. The periodic resumption of additive supply restores nitrogen oxide reduction capability, thus resolving the contradiction by balancing coating maintenance with emission control over time.
Solution Approach 2:
The system performs preliminary coating reduction by halting additive supply before excessive coating build-up occurs. This preliminary action prevents coating problems from developing while minimizing the duration of nitrogen oxide reduction capability loss through brief, proactive maintenance intervals.
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
Prevents coating build-ups and maintains nitrogen oxide levels within regulatory limits by effectively reducing crystal formations and controlling NOx emissions during the coating reduction process.
Implementation Method 1
The additive supplied to the catalyst is adsorbed (stored up) in the catalyst, and nitrogen oxides in the exhaust gases react with the additive stored in the catalyst.
Implementation Method 2
The additive supplied to the catalyst is adsorbed (stored up) in the catalyst, and nitrogen oxides in the exhaust gases react with the additive stored in the catalyst.
Implementation Method 3
nitrogen oxides in the exhaust gases react with the additive stored in the catalyst
Data Source
Figure 1A
Figure 1B
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AI summary
The present invention relates to a method for reduction of a first coating in a post-treatment system (200), which system is intended to treat an exhaust flow arising from combustion in a combustion engine (101), said first coating being formed by an additive supplied to said post-treatment system (200) by being supplied to a first catalyst (201) for reduction of at least one first compound (NOx) in said exhaust flow. The method, during the reduction of said first coating, comprises - determining a first content (Hi) of said first compound (NOx) at a location downstream of said first catalyst (201), and - taking a first remedial measure to reduce the content of said first compound (NOx) when said first content (H1) is greater than a second content (H2). The invention relates also to a system and a vehicle.