Exhaust Purification Catalyst Temperature Control via Oxygen Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing exhaust purification systems for engines, particularly diesel engines, face challenges in efficiently regulating the temperature of NOx storage catalysts during regeneration processes, leading to decreased efficiency in the removal of sulfur oxides and hydrocarbons, as temperature fluctuations affect the release of these components.
Innovation Solution
An exhaust purification apparatus that includes fuel injection means, temperature detection, and oxygen concentration adjustment to maintain the catalyst temperature within a set range by adjusting the frequency and volume of fuel injection, and oxygen concentration during the regeneration process, using post-injection techniques to control the air-fuel ratio and catalyst temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel is injected into the exhaust path to enrich the air-fuel ratio for regeneration, then nitrogen oxides are reduced, but sulfur oxides are generated and stored in the catalyst
Solution Approach 1:
The patent converts the harmful sulfur component in fuel into a beneficial process by controlling its oxidation. Sulfur oxides generated during fuel injection are intentionally allowed to form and then systematically removed through controlled lean burn periods, transforming the harmful sulfur presence into a manageable and ultimately beneficial purification process.
Solution Approach 2:
The patent implements periodic alternation between rich and lean air-fuel ratio periods. During rich periods, fuel is injected to reduce nitrogen oxides. During lean periods, sulfur oxides are oxidized and removed. This periodic switching allows the system to address both nitrogen oxide reduction and sulfur oxide removal without simultaneous conflicts.
2Reliability
If the air-fuel ratio is enriched to perform sulfur oxide removal, then sulfur oxides are released, but the catalyst temperature must be maintained at high levels
Solution Approach 1:
The patent employs feedback control by monitoring catalyst temperature and adjusting the air-fuel ratio accordingly. When temperature drops below the threshold for effective sulfur oxide removal, the system automatically enriches the mixture. When temperature is sufficient, it switches to lean operation, creating a self-regulating thermal management system.
Solution Approach 2:
The patent changes the air-fuel ratio parameter dynamically to control catalyst temperature. By switching between rich and lean conditions, the system regulates temperature to maintain it above the sulfur oxide removal threshold while avoiding excessive temperature rise, thus controlling the thermal state for optimal performance.
3Temperature
If fuel injection frequency is increased to maintain catalyst temperature, then temperature stability improves, but hydrocarbon emissions increase
Solution Approach 1:
The patent applies partial action by providing just enough fuel enrichment to maintain catalyst temperature without excessive fuel injection. The air-fuel ratio is enriched only to the extent necessary to prevent temperature drop, avoiding over-enrichment that would cause hydrocarbon emissions. This optimal point balancing acts as the solution.
4Reliability
If the catalyst is heated to high temperature for regeneration, then sulfur oxides are released, but nitrogen oxides may be re-formed
Solution Approach 1:
The patent uses periodic alternation between rich and lean periods to prevent nitrogen oxide re-formation. During lean periods when temperature is high for sulfur oxide removal, the system quickly switches to rich conditions after sulfur oxide release is complete, preventing the thermal conditions that would otherwise cause nitrogen oxide re-formation.
Solution Approach 2:
The patent rushes through the high-temperature sulfur oxide removal phase quickly by using brief, intensive lean periods followed immediately by rich periods. This rapid transition prevents the prolonged thermal exposure that would allow nitrogen oxides to re-form, skipping the dangerous intermediate state.
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 suppresses temperature fluctuations of the NOx storage catalyst, enhancing the efficiency of sulfur oxide and nitrogen oxide discharge during regeneration, thereby maintaining consistent catalyst performance and reducing emissions.
Implementation Method 1
An exhaust path of the engine, therefore, is provided with, for example, a three way catalyst for decomposing (for example, bringing to reduction) these substances
Implementation Method 2
The fuel also contains a sulfur component as a noxious component. Thus, the sulfur component reacts with oxygen to turn into sulfur oxides (SO x )
Implementation Method 3
The NO x storage catalyst stores NO x contained in the exhaust when the air-fuel ratio of the exhaust is lean
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An exhaust purification apparatus of an engine, which can regulate the temperature (Te1) of an exhaust purification catalyst (52) appropriately and which can release components of an exhaust efficiently by a regeneration process, is provided. When the regeneration process is performed by a regeneration process execution means (71), the oxygen concentration of the exhaust at the time of supply of hydrocarbon by the regeneration process execution means is adjusted, as appropriate, in accordance with a temperature difference (Te3) between the temperature of the exhaust purification catalyst and a set temperature (Te2).