SCR and DPF Control Using Road Preview for Engine Shut-Off
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Solution Overview
Problem
The operation of diesel engine systems with exhaust aftertreatment systems, particularly during cold-starts, faces challenges in balancing ammonia storage in SCR catalysts for efficient NOx conversion while avoiding high temperatures that reduce ammonia capacity and emissions, and managing soot levels in DPFs for effective particle filtration.
Innovation Solution
A method that uses preview information about upcoming road events and engine operations to predict ammonia storage, ammonia slip, and soot levels, adjusting reductant injection and engine NOx output to maintain threshold levels, thereby optimizing engine system operation to reduce emissions and ensure efficient exhaust treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is shut-off to reduce fuel consumption, then fuel economy is improved, but the EATS temperature drops below the level required for efficient NOx conversion
Solution Approach 1:
The control system performs preliminary actions by storing ammonia in the SCR catalyst before engine shut-off occurs. This pre-stored ammonia enables subsequent NOx conversion to proceed efficiently even when the EATS temperature is low and engine shut-off is active, thus resolving the contradiction between fuel economy and temperature maintenance.
2Object-generated harmful factors
If the engine is shut-off to reduce emissions, then emissions are reduced, but the EATS cannot maintain the temperature needed for effective exhaust treatment
Solution Approach 1:
Ammonia is preliminarily stored in the SCR catalyst before engine shut-off. This pre-stored ammonia acts as a reservoir that can be utilized during the shut-off period to maintain NOx conversion efficiency, allowing the system to reduce emissions through shut-off while compensating for the temperature drop through the stored chemical reactant.
3Quantity of substance
If reductant injection is increased to maintain ammonia storage threshold, then ammonia storage is improved, but ammonia slip increases when temperature is high
Solution Approach 1:
The control system employs feedback mechanisms by continuously monitoring both ammonia storage levels and EATS temperature. Based on this feedback, the system dynamically adjusts reductant injection rates - increasing injection when ammonia storage is low and temperature is low, and reducing injection when temperature is high to prevent ammonia slip, thus resolving the contradiction between maintaining ammonia storage and preventing harmful ammonia slip.
4Object-generated harmful factors
If engine out NOx is increased to reduce ammonia storage, then ammonia slip is reduced, but soot accumulation in DPF increases
Solution Approach 1:
The control system uses feedback from multiple sensors to monitor ammonia storage, ammonia slip, and DPF soot levels. When ammonia slip is detected, the system increases engine out NOx to consume the excess ammonia through SCR reactions. Simultaneously, the system monitors soot levels and adjusts engine operation to facilitate DPF regeneration when needed, balancing the contradiction between reducing ammonia slip and managing soot accumulation.
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 improves the efficiency of the exhaust aftertreatment system by preventing unnecessary emissions, maintaining sufficient ammonia storage, and managing soot levels, thus reducing NOx and particle emissions while allowing for engine shut-off to conserve fuel and lower emissions.
Implementation Method 1
Urea, or an ammonia comprising substance, 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
a diesel particulate filter (DPF)... The cleaned, or at least emission reduced, exhaust gases then leaves the EATS
Data Source
AI summary
A method for controlling the operation of an engine system in a vehicle. The engine system including an engine and an exhaust aftertreatment system having an SCR catalyst and a DPF. The method includes determining preview information of the vehicle operation based at least on an upcoming road event and an engine operation associated with the upcoming road event; performing, in response of the preview information, at least one of: controlling the operation of the engine system by increasing reductant injection to meet an ammonia storage threshold level; controlling the operation of the engine system by increasing the engine out NOx to reduce the ammonia storage in the SCR catalyst to meet an ammonia slip threshold level in the SCR catalyst; controlling the operation of the engine system by decreasing the engine out NOx to increase the amount of engine out particles to meet a soot threshold level in the DPF.