Soot Load Estimation During Idle Using Exhaust Flow Modulation
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Solution Overview
Problem
During idle or low load operating conditions, soot load estimation in aftertreatment systems for internal combustion engines is inaccurate due to low pressure measurements, leading to disregarded delta pressure soot load estimates and potential significant soot buildup in particulate filters, which can result in errors or fault codes when engines operate at higher speeds.
Innovation Solution
A controller subroutine periodically decreases the flow threshold for delta pressure soot load estimation and increases exhaust gas flow through the aftertreatment system by modifying engine speed, exhaust gas recirculation, and other parameters to acquire accurate delta pressure soot load measurements, which are then used to update the combined soot load estimate, thereby preventing excessive soot buildup and triggering regeneration processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If delta pressure soot load estimation is used during idle or low load conditions, then soot load measurement is obtained, but measurement accuracy deteriorates due to low pressure values and sensor errors
Solution Approach 1:
The controller performs preliminary actions by periodically increasing exhaust gas flow through engine speed modulation and EGR valve adjustment before taking the pressure measurement. This ensures that the measurement is taken under conditions where the pressure differential is sufficiently high to overcome sensor errors and provide accurate soot load data, even during extended idle or low-load operation.
Solution Approach 2:
The system implements periodic action by conducting delta pressure soot load estimation at predetermined time intervals (e.g., every 8, 10, 20, or 100 hours of operation). This periodic measurement approach ensures that soot buildup is monitored over time without requiring continuous high-flow conditions, resolving the contradiction between measurement availability and measurement precision.
2Reliability
If delta pressure soot load estimation is disregarded during idle or low load conditions, then measurement reliability is maintained, but soot buildup detection accuracy deteriorates over extended periods
Solution Approach 1:
The system applies dynamics by adaptively adjusting operating parameters (engine speed, EGR valve position) to create optimal measurement conditions temporarily. This dynamic adjustment allows the system to maintain measurement reliability by ensuring measurements are taken when pressure differentials are sufficient, while still capturing accurate soot load data during extended idle or low-load periods.
Solution Approach 2:
The controller changes physical parameters (exhaust gas flow rate, engine speed, EGR rate) temporarily to enable accurate soot load measurement. By modifying these parameters periodically, the system maintains measurement reliability while improving soot load estimation accuracy over extended operating periods.
3Measurement precision
If engine speed is increased to improve pressure measurement accuracy, then exhaust gas flow increases improving measurement quality, but engine operating conditions change
Solution Approach 1:
The controller performs preliminary engine speed increases and EGR valve adjustments before taking the soot load measurement. These preliminary actions create the necessary flow conditions for accurate measurement, then the system returns to normal operating conditions, minimizing disruption to overall engine operation.
Solution Approach 2:
The system uses periodic action by temporarily modifying engine speed and EGR settings only at predetermined measurement intervals. This approach improves measurement precision while maintaining ease of operation, as the parameter changes occur briefly and periodically rather than continuously.
Data Source
AI summary
A system can include an engine, an aftertreatment system with a particulate filter, and a controller. The controller is configured to compare a time value since a last delta pressure soot load estimate process to a predetermined time threshold. Responsive to the time value being greater than or equal to the predetermined time threshold, the controller decreases a flow threshold value to a lower flow threshold value. If the flow amount is greater than or equal to the lower flow threshold value, then the controller activates a delta pressure soot load estimation process. A combined soot load estimate is then calculated using a delta pressure soot load estimation of the delta pressure soot load estimate process responsive to the lower flow threshold value.