Integrated Engine Aftertreatment Control for Ammonia Slip Prevention
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Solution Overview
Problem
Existing engine systems face challenges in maintaining effective reduction reactions for NOx emissions due to rapid changes in exhaust mass flow rate, NOx percentage, and temperature fluctuations, leading to undesirable slip events such as ammonia or NOx slip, which cannot be undone once occurred.
Innovation Solution
An integrated engine and aftertreatment control system that includes an electronically controlled engine with a reductant delivery system and an electronic aftertreatment controller, which communicates exhaust control signals to adjust engine operation and reductant dosing to prevent slip events by detecting preconditions for outgas slip and altering engine operation in response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steady state reductant dosing control is used to convert NOx to desirable gases, then the reduction reaction can proceed effectively under stable conditions, but the system cannot respond quickly to rapid changes in exhaust mass flow rate, NOx percentage, and temperature, resulting in slip events
Solution Approach 1:
The patent implements dynamic control by continuously monitoring exhaust conditions (mass flow rate, NOx percentage, temperature) and adjusting reductant dosing in real-time. The electronic aftertreatment controller modifies dosing rates dynamically based on sensed changes, allowing the system to adapt to rapidly changing exhaust conditions while maintaining effective reduction reaction
Solution Approach 2:
The system employs feedback control through sensors that detect exhaust parameters and feed this information back to the electronic aftertreatment controller. The controller uses this feedback to continuously adjust reductant dosing, ensuring the reduction reaction remains effective under varying operating conditions and preventing slip events
2Reliability
If reductant dosing is increased to ensure complete NOx conversion, then the reduction reaction equilibrium improves, but excess reductant causes ammonia slip events
Solution Approach 1:
The patent dynamically adjusts reductant dosing parameters based on real-time exhaust conditions. By changing dosing rates according to actual NOx levels, temperature, and flow conditions, the system achieves complete NOx conversion while preventing excess reductant accumulation that would cause ammonia slip
Solution Approach 2:
The system applies partial dosing rather than excessive dosing by precisely matching reductant injection to actual NOx levels. This controlled partial action ensures sufficient reductant for complete conversion without over-dosing, thereby preventing ammonia slip events
3Object-generated harmful factors
If reductant dosing is decreased to prevent ammonia slip, then ammonia emissions are reduced, but insufficient reductant causes NOx slip events
Solution Approach 1:
The electronic aftertreatment controller uses feedback from NOx sensors and other exhaust parameter sensors to continuously monitor reduction reaction effectiveness. When NOx slip is detected or predicted, the controller increases dosing; when ammonia slip risk is detected, it decreases dosing, dynamically balancing between preventing both types of slip
Solution Approach 2:
The system dynamically adjusts dosing levels based on real-time conditions rather than using fixed dosing rates. This dynamic adjustment allows the system to prevent ammonia slip by reducing dosing when appropriate while maintaining sufficient dosing to prevent NOx slip when conditions require it
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
The system effectively reduces undesirable emissions by preemptively adjusting engine operation to prevent slip events, ensuring that NOx and reductant are balanced, thereby maintaining a stable reduction reaction and minimizing the occurrence of ammonia or NOx slip at the tailpipe.
Implementation Method 1
a reductant injection nozzle is positioned in the exhaust passage upstream from the reductant catalyst in order to mix an added reductant with exhaust gases before arrival at the catalyst where a reduction reaction occurs
Implementation Method 2
convert undesirable NOx emissions into more desirable gas species prior to exiting the engine system at the tailpipe
Implementation Method 3
a dedicated electronic aftertreatment controller utilizes a variety of sensors to detect the state of the exhaust flow, and respond to that sensed state with urea dosing control signals to improve equilibrium of the reduction reaction
Data Source
AI summary
An engine system includes an integrated engine and aftertreatment control system via an electronic aftertreatment controller that is in communication with the electronic engine controller. An aftertreatment control algorithm is operable to generate an exhaust control signal and a reductant dosing control signal. The dosing control signal is used to control a flow rate of a reductant (e.g. urea) injection rate into the exhaust system for facilitating a reduction reaction with NOx in the exhaust flow at a suitable downstream catalyst location. The exhaust control signal is communicated to the electronic engine controller, which responds by altering engine operation to change some aspect of the engine exhaust. In one specific example, an ammonia slip event precondition is detected by the electronic aftertreatment controller, and an exhaust control signal in the form of an increase NOx request is communicated to the engine controller, which responds by altering engine operation to increase NOx output in the hopes of preempting the expected ammonia slip event prior to its actual occurrence to maintain undesirable emissions low at the tailpipe.