Particulate Filter Soot Load Estimation During Engine Shutdown
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Solution Overview
Problem
Existing methods for estimating soot load on particulate filters during engine non-combusting conditions do not account for soot oxidation, leading to inaccurate initial estimates and potentially increased exhaust backpressure, frequent regenerations, and reduced fuel efficiency.
Innovation Solution
Estimating soot load on particulate filters during engine shutdown by using the initial temperature and temperature profile, along with oxygen flow, to calculate the amount of soot burned during the non-combusting period, allowing for accurate updates at the start of the subsequent engine cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If soot load estimation is performed during engine operation without accounting for oxidation, then the monitoring process is simple, but the estimation accuracy deteriorates due to unaccounted soot loss during shutdown periods
Solution Approach 1:
The system performs preliminary estimation of soot oxidation during the engine shutdown period before the next drive cycle begins. By calculating the expected soot loss during shutdown using temperature profiles and oxidation models, the system prepares an adjusted initial soot load value that accounts for oxidation effects, thereby improving measurement precision without adding complex hardware
Solution Approach 2:
The system uses feedback from temperature sensors and oxidation rate models to continuously adjust the soot load estimation. The estimated oxidation amount during shutdown is fed back into the soot load calculation, creating a closed-loop estimation process that compensates for oxidation effects and maintains accuracy
2Reliability
If the initial soot load estimate at engine restart is inaccurate, then the estimation process is simple, but the exhaust backpressure control deteriorates leading to potential performance issues
Solution Approach 1:
Before the engine restarts and begins the next drive cycle, the system performs a preliminary calculation of soot oxidation that occurred during shutdown. This preliminary action adjusts the initial soot load estimate to reflect the actual reduced soot amount, ensuring reliable exhaust backpressure control from the start of the new drive cycle without waiting for actual measurements
Solution Approach 2:
The system applies a compensatory adjustment to the initial soot load estimate that cushions against the potential error of ignoring oxidation. By pre-calculating the oxidation amount and subtracting it from the accumulated soot load, the system creates a buffer that prevents overestimation and ensures reliable backpressure management
3Productivity
If PF regeneration is scheduled based on inaccurate soot loads, then the scheduling is simple, but fuel economy deteriorates due to increased regeneration frequency
Solution Approach 1:
The system incorporates feedback from oxidation modeling into the soot load estimation used for regeneration scheduling. By continuously updating the soot load estimate with oxidation losses calculated from temperature profiles and shutdown duration, the system achieves more accurate scheduling decisions that improve fuel economy by avoiding unnecessary regenerations
Solution Approach 2:
The system performs preliminary oxidation accounting before regeneration scheduling decisions are made. By calculating the net soot load after shutdown oxidation in advance, the system can make more accurate regeneration scheduling decisions that optimize fuel economy without requiring complex real-time adjustments during operation
4Loss of energy
If deceleration fuel shut-off events are altered based on inaccurate soot loads, then the control logic is simple, but fuel efficiency deteriorates
Solution Approach 1:
The system uses feedback from accurate soot load estimation that includes oxidation effects to make informed decisions about deceleration fuel shut-off events. By knowing the true soot load level after shutdown oxidation, the system can optimize DFSO timing and duration to maximize fuel efficiency without compromising emissions control
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 ensures accurate scheduling of particulate filter regeneration, optimizing fuel efficiency and emissions quality by accounting for soot oxidation during engine-off periods.
Implementation Method 1
particulate filters (PF) may be included in the engine exhaust to filter out exhaust PMs
Implementation Method 2
Oxidation of accumulated soot on the PF may occur during engine non-combusting conditions
Implementation Method 3
based on a temperature of the PF at shutdown and a corresponding temperature profile of the PF during the engine shutdown period
Data Source
AI summary
Methods and systems are provided for monitoring a change in exhaust particulate filter (PF) soot load during an engine non-combusting condition. In one example, a method may include, responsive to a higher than threshold PF temperature immediately prior to an engine shutdown, estimating a rate of soot burn when the engine is no longer combusting, and estimating a soot load on the PF during and at an onset of immediately subsequent engine start based in part on the rate of soot burn.