Exhaust Purification Catalyst NOx Reduction Strategy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The NOx purification rate in exhaust purification systems for internal combustion engines decreases at high temperatures due to the degradation of NOx storage catalysts.
Innovation Solution
An exhaust purification system that employs a hydrocarbon feed valve to inject hydrocarbons into the engine exhaust passage, where a precious metal catalyst and a basic exhaust gas flow surface interact to reduce NOx, using two methods: a first method with predetermined feed intervals to lower the air-fuel ratio and a second method by reducing hydrocarbon feed amounts during specific engine strokes, thereby maintaining high NOx purification efficiency even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrocarbons are fed at predetermined intervals to reduce NOx, then NOx purification rate is improved, but at high temperatures the purification rate deteriorates
Solution Approach 1:
The system dynamically switches between two hydrocarbon feed methods based on operating conditions. The first method uses predetermined feed intervals for normal operation, while the second method reduces hydrocarbon feed amount and feeds fuel during specific engine strokes (second half of expansion stroke or exhaust stroke) when high temperature occurs, adapting the feed strategy to temperature conditions to maintain purification efficiency
Solution Approach 2:
The system changes the hydrocarbon feeding parameters based on temperature. At high temperatures, it transitions from the first method (predetermined intervals) to the second method (reduced feed amount with specific timing during expansion/exhaust strokes), modifying the feeding parameters to prevent nitrate formation and maintain NOx reduction effectiveness
2Reliability
If hydrocarbon feed amount is increased to maintain purification rate, then nitrate formation is prevented, but energy consumption increases
Solution Approach 1:
The second hydrocarbon feed method uses partial action by reducing the hydrocarbon feed amount compared to the first method. Instead of maintaining full feed levels, it feeds hydrocarbons at reduced amounts during specific engine strokes, achieving sufficient NOx purification without excessive energy consumption that would lead to nitrate formation
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 system selectively uses hydrocarbon feed methods to maintain a high NOx purification rate across varying temperatures, preventing the formation of nitrates and ensuring effective NOx reduction without significant nitrates formation, even at high catalyst temperatures.
Implementation Method 1
an exhaust purification catalyst for causing a reaction between hydrocarbons injected from the hydrocarbon feed valve and NOx contained in exhaust gas
Implementation Method 2
a basic exhaust gas flow surface part is formed around the precious metal catalyst
Data Source
AI summary
In an internal combustion engine, inside an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged. A first hydrocarbon feed method which injections hydrocarbons from the hydrocarbon feed valve (15) by predetermined feed intervals (ΔT) so that the air-fuel ratio of the exhaust gas falls to the demanded minimum air-fuel ratio (X) to thereby remove the NOx contained in the exhaust gas and a second hydrocarbon feed method which lowers the feed amount of hydrocarbons from the hydrocarbon feed valve (15) and feeds fuel to the combustion chambers (2) during a second half of the expansion stroke or the exhaust stroke are selectively used.