Diesel Particulate Filter Ash Layer for Passive Regeneration
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Solution Overview
Problem
Conventional diesel particulate filters face challenges with runaway exothermic soot oxidation reactions and increased back pressure due to soot load density and non-combustible ash deposits, which can damage the filter and increase fuel consumption.
Innovation Solution
An engine system that burns high ash oil to generate an ash deposit on the diesel particulate filter, maintaining a stable soot load density by controlling the NOx to soot ratio and temperature, with an ash layer interposed between the filter and soot load, allowing passive soot regeneration without active regeneration processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If active regeneration is performed to oxidize soot, then soot load is reduced, but fuel consumption increases due to additional fuel injected into the aftertreatment system
Solution Approach 1:
The system enables passive regeneration where the engine's own exhaust gases, containing NOx and soot, facilitate soot oxidation on the filter without requiring external fuel injection. The NOx in the exhaust stream acts as an oxidant to convert soot to CO2 and N2, allowing the system to regenerate itself using existing exhaust components rather than adding separate regeneration fuel systems.
Solution Approach 2:
The invention changes the chemical parameters of the exhaust stream by controlling the NOx to soot ratio and temperature to enable passive oxidation. By adjusting engine operating parameters to maintain specific temperature ranges and NOx concentrations, the system creates conditions where exhaust gases alone can oxidize soot without additional fuel, transforming the exhaust from a waste product into a regeneration medium.
2Productivity
If soot load density is increased to reduce back pressure, then engine efficiency improves, but the risk of runaway exothermic oxidation reaction increases
Solution Approach 1:
The system continuously monitors exhaust temperature and NOx to soot ratio to maintain optimal conditions for passive regeneration. By using feedback control to adjust engine operating parameters, the system ensures that temperature remains below the threshold for runaway oxidation while maintaining sufficient soot oxidation rates to prevent filter clogging, creating a self-regulating mechanism that balances efficiency and safety.
Solution Approach 2:
NOx acts as an intermediary substance that mediates between the soot load and the oxidation process. Rather than allowing direct combustion of soot which could lead to runaway reactions, NOx serves as a controlled oxidant that gradually converts soot to CO2 and N2, preventing thermal runaway while maintaining effective soot removal.
3Object-generated harmful factors
If ash deposits are present on the filter, then back pressure increases, but ash blocks the filter and obstructs soot oxidation
Solution Approach 1:
The invention converts the harmful effect of ash deposits into a beneficial barrier layer. The ash forms a controlled deposit on the filter surface that actually protects the underlying catalyst from direct contact with exhaust gases, preventing catalyst degradation while allowing soot oxidation to proceed through the ash layer. This transforms the traditionally harmful ash into a protective functional layer.
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 stabilizes soot load density, reduces the risk of filter damage, and minimizes fuel consumption by avoiding the need for active regeneration, while maintaining efficient NOx reduction and preventing excessive back pressure.
Implementation Method 1
an ash layer interposed between the filter and soot load, allowing passive soot regeneration
Implementation Method 2
stabilizing the soot load density via controlled ash deposits on a diesel particulate filter
Implementation Method 3
Such materials facilitate a conversion of NO to NO2, thereby increasing the ratio of NO2 to NO upstream of the SCR substrate
Implementation Method 4
The elevated level of NO2 provided by the oxidation catalyst may assist in both improving NOx conversion over the SCR catalyst and oxidizing soot particles
Implementation Method 5
SCR is a process where a reductant, most commonly urea ((NH2)2CO), a water/urea solution or the like, is selectively injected into the exhaust gas stream of an engine and absorbed onto a downstream substrate. The injected urea solution decomposes into ammonia (NH3), which reacts with NO in the exhaust gas to form water (H2O) and diatomic nitrogen (N2)
Implementation Method 6
A runaway exothermic oxidation reaction is generally undesirable since temperatures can become briefly so high that the filter substrate (e.g., zeolite) may become cracked or otherwise damaged
Implementation Method 7
Active regeneration of a diesel particulate filter refers to a process by which the accumulated soot in the diesel particulate filter is oxidized by increasing the temperature at the filter
Data Source
AI summary
An engine system includes an electronically controlled compression ignition engine configured to burn diesel fuel and a high ash oil to produce an exhaust with a temperature and NOx to soot ratio as well as a controlled level of ash deposits on the particulate filter of the system. An aftertreatment system is fluidly connected to the engine and includes a diesel oxidation catalyst, a reductant supply, and a diesel particulate filter coated with a NOx reduction catalyst. The soot load density on the diesel particulate filter can be stabilized by oxidizing soot at about a same rate as the compression ignition engine is supplying soot to the aftertreatment system.