OSC Reactivation Control for Gasoline Emissions Systems
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Solution Overview
Problem
Conventional three-way catalytic converters have low selectivity, leading to ammonia re-oxidization to nitrogen oxides downstream, affecting the air-to-fuel ratio balance and exhaust composition, which complicates the reactivation of oxygen storage capacity (OSC) materials in catalytic converter systems.
Innovation Solution
A method involving monitoring exhaust gas oxygen and nitrogen oxide concentrations to calculate and control OSC reactivation times and rates for both upstream and downstream catalysts, using specific lambda setpoints and temperature conditions to manage OSC material capacity and prevent nitrogen oxide remake, with catalysts comprising ceria-zirconia and precious group metals like palladium and platinum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional three-way catalytic converters are used to oxidize exhaust gases, then nitrogen oxides can be converted to nitrogen, but ammonia is re-oxidized to nitrogen oxides downstream, reducing purification effectiveness
Solution Approach 1:
The catalytic converter is divided into multiple functional zones: a first catalyst layer for nitrogen oxide reduction to ammonia, and a second catalyst layer for ammonia oxidation to nitrogen. This segmentation allows each zone to perform its specific function independently, preventing ammonia re-oxidization and improving overall purification reliability.
Solution Approach 2:
Different catalyst materials are used in different zones of the converter. The first catalyst contains nitrogen oxide reduction catalysts, while the second catalyst contains ammonia oxidation catalysts. This local differentiation ensures that ammonia produced in the first zone is selectively oxidized to nitrogen in the second zone, preventing reformation of nitrogen oxides.
2Object-generated harmful factors
If oxygen storage capacity (OSC) materials are used to maintain stoichiometric air-to-fuel ratios, then hydrocarbon and carbon monoxide purification improves, but OSC materials require periodic reactivation which complicates system control
Solution Approach 1:
The system performs preliminary actions by maintaining the OSC material in a reduced state during normal operation and proactively reactivating it when regeneration is needed. The control method monitors oxygen storage capacity and initiates reactivation before the OSC material becomes fully oxidized, simplifying the control strategy by avoiding complex real-time adjustments during reactivation.
Solution Approach 2:
The OSC material continuously cycles between oxidized and reduced states, maintaining stoichiometric air-to-fuel ratios throughout the engine operation cycle. The control system ensures continuous useful action by seamlessly managing the transition between storage and reactivation phases, eliminating interruptions in purification performance.
3Object-generated harmful factors
If the air-to-fuel ratio is maintained stoichiometrically balanced, then both nitrogen oxides and hydrocarbons can be purified, but OSC materials become saturated and require regeneration, disrupting the balance
Solution Approach 1:
The OSC material undergoes periodic cycles of oxygen storage and reactivation. During the storage phase, it maintains stoichiometric balance and purifies exhaust gases. When saturated, it enters a reactivation phase where it releases stored oxygen and is regenerated. This periodic action allows the OSC material to continuously maintain purification effectiveness without permanent saturation.
Solution Approach 2:
The system discards excess oxygen from the OSC material during reactivation and recovers the material's oxygen storage capacity for future use. By controlled reactivation, the OSC material releases its stored oxygen to maintain air-to-fuel ratio balance, then regains its storage capacity, extending its operational duration between regenerations.
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 effectively maintains stoichiometric air-to-fuel ratios, minimizes nitrogen oxide reformation, and optimizes OSC material reactivation, enhancing the purification efficiency of hydrocarbons and carbon monoxide while controlling nitrogen oxide emissions.
Implementation Method 1
The OSC material absorbs oxygen when the oxygen concentration in exhaust gas is high and releases oxygen when the oxygen concentration of the exhaust gas is low
Implementation Method 2
a three-way catalytic converter to assist with oxidizing the formed carbon monoxide, hydrocarbons, and nitrogen oxides gases into carbon dioxide, nitrogen, and water
Implementation Method 3
a three-way catalytic converter to assist with oxidizing the formed carbon monoxide, hydrocarbons, and nitrogen oxides gases
Implementation Method 4
ammonia converted from nitrogen oxides at a location upstream (e.g., at the front end catalytic converter) has the potential to be re-oxidized to nitrogen oxides at a location downstream
Data Source
AI summary
A catalytic converter system having oxygen storage materials is disclosed and methods for determining whether to reactivate oxygen storage materials and monitoring failure events of the oxygen storage materials are also disclosed.