SCR Ammonia Storage Control Before Engine Restart
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Solution Overview
Problem
Existing exhaust after treatment systems in vehicles face challenges in maintaining sufficient ammonia storage levels in the SCR catalyst during engine shutdown and re-start, leading to inefficient emission control.
Innovation Solution
A computer system determines predicted vehicle operational information, including travel route and topography, to adjust the ammonia storage level in the SCR catalyst before engine shutdown, using injectors to inject a predetermined amount of reductant to achieve a set threshold, optimizing ammonia storage for the upcoming travel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SCR catalyst operates at high temperature to ensure sufficient NOx conversion, then the conversion efficiency is improved, but the ammonia storage capacity decreases
Solution Approach 1:
The system performs preliminary action by injecting reductant before the predicted engine shutdown to pre-charge the SCR catalyst with ammonia. This ensures that when the engine restarts, the catalyst already has sufficient ammonia storage capacity to handle the expected emission load, resolving the contradiction between maintaining high conversion efficiency and preserving ammonia storage capacity through temperature management.
2Use of energy by moving object
If the engine is shut down to save fuel, then fuel economy is improved, but the ammonia storage level becomes insufficient upon re-start
Solution Approach 1:
The control system determines predicted vehicle operational information including future shutdown and restart events, then performs preliminary reductant injection before the shutdown occurs. This preliminary action ensures the SCR catalyst maintains adequate ammonia storage levels even when the engine is shut down for fuel economy, guaranteeing reliable emission control upon restart.
Solution Approach 2:
The system continuously monitors current ammonia storage levels and compares them against required levels based on predicted operational conditions. This feedback mechanism allows the system to adjust reductant injection timing and quantity to maintain reliable ammonia storage levels while enabling fuel-saving shutdown operations.
3Reliability
If reductant is injected continuously to maintain ammonia storage, then emission control reliability is improved, but reductant consumption increases
Solution Approach 1:
Instead of continuous reductant injection, the system employs periodic action by injecting reductant only at strategically determined intervals based on predicted engine shutdown/restart events and current ammonia storage levels. This reduces unnecessary reductant consumption while maintaining emission control reliability through targeted injection timing.
Solution Approach 2:
The system dynamically changes injection parameters (timing, quantity, frequency) based on real-time monitoring of ammonia storage levels and predicted operational conditions. By adapting these parameters rather than using fixed continuous injection, the system maintains reliable emission control while minimizing reductant consumption.
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 emissions such as NOx and ammonia slip by ensuring adequate ammonia storage in the SCR catalyst, enhancing emission control efficiency during engine re-start.
Implementation Method 1
Urea, or an ammonia comprising substance, referred to as a reductant, is injected upstream of the SCR catalyst to assist in converting nitrogen oxides, also referred to as NOx, with the aid of a catalyst, into diatomic nitrogen (N2), and water (H2O)
Implementation Method 2
The process for transforming the injected reductant into NH3 are temperature dependent
Data Source
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AI summary
A computer system comprising processing circuitry configured to: - determine predicted vehicle operational information for a vehicle including at least predicted travel route (110) for a vehicle (1), a predicted shutdown of a combustion engine (10) of the vehicle (1) along the predicted travel route (110), and a predicted subsequent re-start of the combustion engine (10), - determine the topography (120) of the predicted travel route (110) subsequent to the predicted re-start of the combustion engine (10), - determine a set ammonia storage level threshold of a selective catalytic reduction, SCR, catalyst (31, 32) arranged in an exhaust after treatment system (30) to the combustion engine (10) in response to the topography (120) of the predicted travel route (110) subsequent to the predicted combustion engine re-start, - control an injector (34a, 34b) of the exhaust after treatment system (30) to inject a predetermined amount of reductant achieving the set ammonia storage level threshold prior to shutdown of the combustion engine (10).