Reductant Injection Control for Low Engine Load Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing feedback control systems for reductant injection in emission reduction systems of internal combustion engines face accuracy issues at low engine load rates due to inaccuracy in reductant flow measurement, leading to potential NOx level increases and reductant slip.
Innovation Solution
Implementing a control method that alternates between allowing and restricting reductant flow cycles when the engine operates below a predetermined threshold, using a low mode setpoint value during allowing cycles and preventing reductant flow during restricting cycles to maintain accurate control, thereby compensating for flow meter inaccuracy at low load rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback control system with flow meter is used to control reductant injection, then control accuracy is improved at high and middle engine load rates, but measurement precision deteriorates at low engine load rates causing NOx levels to rise above required levels
Solution Approach 1:
The control system dynamically switches between two operational modes: a first control mode for low engine load rates where the flow meter is bypassed and a second control mode for high and middle engine load rates where the flow meter is used. This dynamic adaptation allows the system to maintain reliable control accuracy across the entire engine operating range by selecting the appropriate measurement method based on current load conditions.
Solution Approach 2:
The system changes the operational parameter of the flow meter by switching it between active and inactive states based on engine load rate thresholds. When the engine operates at low load rates below a first threshold, the flow meter is deactivated and its signal ignored. When the engine operates at high or middle load rates above the threshold, the flow meter is activated and its measurements are used for feedback control. This parameter change resolves the contradiction by avoiding the use of inaccurate flow meter readings at low loads.
2Speed
If reductant flow is continuously adjusted based on flow meter feedback, then control responsiveness is improved, but control accuracy deteriorates at low load rates due to flow meter inaccuracy
Solution Approach 1:
The system dynamically adjusts the control strategy based on engine load rate. At low load rates, the system switches to a dynamic injection pattern using alternating allowing cycles and restricting cycles, which maintains control responsiveness without relying on inaccurate flow meter measurements. At high and middle load rates, the system uses continuous feedback control with the flow meter for accurate measurement-based adjustment. This dynamic approach resolves the contradiction by adapting the control method to match the reliability of available measurements.
Solution Approach 2:
At low engine load rates, the system implements periodic allowing cycles and restricting cycles for reductant injection. During allowing cycles, reductant injection is permitted with a low mode setpoint value; during restricting cycles, reductant injection is prevented. This periodic action provides controlled reductant delivery that maintains effectiveness without requiring accurate continuous flow measurement, thus resolving the contradiction between responsiveness and measurement precision at low loads.
Data Source
AI summary
When an internal combustion engine is driven at a low rate below a certain threshold value, exemplary embodiments as disclosed herein allow and restrict a reductant flow to an injector in repeating allowing cycles and restricting cycles. During the allowing cycles the controller is set to keep the reductant flow as close as possible a determined low point setpoint value. During the restricted cycles the reductant flow is prevented.