Particulate Filter Regeneration via Secondary Air Injection
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Solution Overview
Problem
Direct injection engines face challenges in efficiently regenerating particulate filters due to delayed exhaust temperature reach, which can lead to decreased engine performance and adverse effects on catalyst temperature, affecting emissions and fuel efficiency.
Innovation Solution
A method involving routing exhaust gases through a three-way catalyst and a gasoline particulate filter, controlling engine air-fuel ratio enrichment, and injecting secondary air to create an exotherm at the filter, while adjusting engine operations to maintain catalyst temperature above light-off temperature, using air pumps and valves for closed-loop control of air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If engine air-fuel ratio is enriched and secondary air is injected to increase particulate filter temperature, then regeneration time is reduced, but catalyst temperature decreases which adversely affects emissions quality
Solution Approach 1:
The exhaust stream is segmented into different air-fuel ratio zones: a first portion is enriched (richer than stoichiometric) to generate heat for PF regeneration, while a second portion remains at or near stoichiometric to maintain catalyst temperature and emissions performance. This segmentation allows simultaneous achievement of rapid regeneration and emissions compliance.
Solution Approach 2:
Different regions of the exhaust system are given different air-fuel ratio characteristics: the region upstream of the particulate filter receives enriched mixture for heat generation, while the region at the catalyst maintains stoichiometric mixture for optimal catalytic function. This local differentiation resolves the temperature conflict between PF and catalyst.
2Loss of time
If spark timing is retarded to increase particulate filter temperature, then regeneration is expedited, but fuel efficiency decreases
Solution Approach 1:
Instead of changing spark timing (which affects fuel efficiency), the system changes the air-fuel ratio parameter by injecting secondary air to create an enriched mixture. This generates the necessary heat for regeneration without the fuel efficiency penalty associated with spark retardation.
3Productivity
If secondary air is injected upstream of particulate filter, then oxidation rate of soot is increased, but catalyst temperature drops due to cooling effect
Solution Approach 1:
The exhaust flow is divided into two streams with different air-fuel ratios: an enriched stream that generates heat for soot oxidation and a stoichiometric stream that maintains catalyst temperature. This segmentation allows the cooling effect of secondary air injection to be localized to the PF region while the catalyst region receives sufficient heat.
Solution Approach 2:
A control system acts as an intermediary to balance the air-fuel ratio distribution between the catalyst and particulate filter regions. By dynamically adjusting the enrichment level, the control system ensures that the catalyst maintains its light-off temperature while the PF receives sufficient heat for regeneration.
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 expedites particulate filter regeneration without degrading drivability or engine performance, maintaining catalyst temperature and reducing the time required to reach regeneration temperature, thus improving emissions and fuel efficiency.
Implementation Method 1
injecting air into the GPF to create an exotherm with the enriched exhaust gases entering the GPF
Data Source
AI summary
Methods and systems are provided for heating an exhaust particulate filter (PF) to enable filter generation. In one example, a method may include adjusting engine air fuel ratio and injecting secondary air flow upstream of the PF to increase PF temperature. The level of engine air fuel ratio adjustment and the amount of secondary air injection upstream of the PF may be adjusted to account for enrichment induced cooling at a three-way catalyst (TWC) positioned upstream of the PF.