DPF Regeneration Threshold Adjustment for Diesel Exhaust
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Solution Overview
Problem
Conventional exhaust emission purification systems struggle to accurately judge the start timing of forced regeneration in diesel particulate filters (DPFs) due to uneven PM accumulation, leading to excessive temperature rises and potential melting-loss of the DPF during forced regeneration, as constant differential pressure thresholds fail to account for varying mileage and driving patterns.
Innovation Solution
The system adjusts the differential pressure threshold for DPF regeneration by multiplying a reference threshold by a coefficient that varies based on vehicle mileage after previous forced regeneration, increasing the frequency of regeneration and ensuring PM is burned while still small, thus preventing excessive temperature rises and melting-loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant differential pressure threshold is used to judge forced regeneration start timing, then the control system is simple, but it fails to account for varying mileage and driving patterns causing uneven PM accumulation
Solution Approach 1:
The differential pressure threshold is changed from a constant value to a variable threshold that dynamically adjusts based on mileage after previous forced regeneration. The threshold decreases as mileage increases, allowing the system to adapt to varying PM accumulation patterns caused by different driving conditions and mileage history.
Solution Approach 2:
The threshold parameter is modified by introducing a mileage-dependent coefficient that multiplies the reference threshold. This parameter change enables the system to account for mileage and driving pattern variations, improving regeneration timing judgment accuracy without significantly increasing system complexity.
2Quantity of substance
If forced regeneration is delayed until differential pressure reaches a high threshold, then PM accumulation is allowed to build up, but excessive temperature rise and melting-loss of DPF occur during forced regeneration
Solution Approach 1:
The system performs forced regeneration earlier than traditional constant-threshold methods by using a mileage-adjusted threshold. This preliminary action removes PM before it accumulates to excessive levels, preventing the harmful effects of excessive temperature rise and melting-loss during regeneration.
Solution Approach 2:
The system uses mileage information as feedback to adjust the regeneration threshold. By incorporating mileage history, the system learns from previous regeneration cycles and optimizes timing to prevent excessive PM accumulation while avoiding the harmful effects of delayed regeneration.
3Temperature
If forced regeneration is performed frequently to remove unevenly accumulated PM, then temperature rise is controlled, but regeneration frequency increases
Solution Approach 1:
The regeneration threshold dynamically decreases with increasing mileage, which naturally increases regeneration frequency. This dynamic adjustment ensures that PM is removed before excessive accumulation occurs, controlling temperature rise while accepting the trade-off of more frequent regeneration cycles.
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 allows for accurate and timely forced regeneration, preventing excessive PM accumulation and temperature-related damage to the DPF, while also mitigating oil dilution issues during manual regeneration and reducing driver intervention in automatic regeneration.
Implementation Method 1
HC (hydrocarbon) is burnt by oxidation catalyst disposed upstream side of the filter or oxidation catalyst supported by the filter. Through utilization of the oxidation reaction heat, the exhaust gas temperature at the filter entrance or the filter surface is raised.
Implementation Method 2
when the exhaust gas temperature is equal to or higher than approximately 350°C, PM captured by a filter burns continuously to be purified and the filter is regenerated by itself
Implementation Method 3
a forced regeneration start timing of a DPF (diesel particulate filter) is judged based on the comparison of a differential pressure across the DPF with a predetermined differential pressure threshold across the DPF
Data Source
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AI summary
In an exhaust emission purification method and an exhaust emission purification system where forced regeneration start timing of a DPF for purifying the PM (particulate matters) in exhaust gas is judged based on the comparison of a differential pressure across the DPF with a predetermined differential pressure threshold across the DPF, a differential pressure threshold (ΔPs) across the DPF is set by multiplying a reference differential pressure threshold (ΔPs0) across the DPF by a coefficient( α(ΔM)) which varies stepwise or continuously depending on the mileage (ΔM) of a vehicle after previous forced regeneration. Consequently, the PM can be removed by burning while the amount of PM accumulated unevenly in the DPF is still small, and excessive temperature rise in the DPF resulting from excessive accumulation of PM during forced regeneration and melting-loss of DPF due to excessive temperature rise can be prevented.