Exhaust Purification Catalyst Dynamic Air-Fuel Control
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Solution Overview
Problem
The NOx purification rate in internal combustion engine exhaust systems decreases when the exhaust purification catalyst temperature rises, as the NOx storage catalyst's effectiveness falls at high temperatures.
Innovation Solution
An exhaust purification system with a hydrocarbon feed valve and an exhaust purification catalyst downstream, where hydrocarbons are partially oxidized and injected at predetermined intervals to maintain a lean air-fuel ratio, and a basic layer on the catalyst enhances NOx reduction, with two NOx purification methods used based on engine operating states to maintain high NOx removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the exhaust purification catalyst temperature increases, then the catalyst activity increases, but the NOx purification rate decreases
Solution Approach 1:
The patent implements dynamic switching between two NOx purification methods based on catalyst temperature. When temperature is high, the first method (hydrocarbon injection at predetermined intervals with lean air-fuel ratio) is used. When temperature is low, the second method (switching air-fuel ratio to rich) is used. This dynamic adaptation resolves the contradiction by selecting the appropriate method for each temperature condition.
Solution Approach 2:
The patent changes the operational parameters of the exhaust purification system based on temperature. It modifies hydrocarbon injection timing, air-fuel ratio, and purification method selection according to catalyst temperature conditions. This parameter adaptation allows the system to maintain high NOx purification rates across different temperature ranges.
2Reliability
If hydrocarbons are injected frequently to maintain high NOx purification rate, then NOx removal efficiency increases, but fuel consumption increases
Solution Approach 1:
The system dynamically adjusts hydrocarbon injection frequency and air-fuel ratio based on catalyst temperature and engine operating conditions. By switching between two purification methods, it optimizes the balance between NOx removal efficiency and fuel consumption, avoiding excessive hydrocarbon injection when not necessary.
Solution Approach 2:
The patent changes operational parameters including hydrocarbon injection amount, injection intervals, and air-fuel ratio based on temperature and engine state. This adaptive parameter adjustment ensures effective NOx control while minimizing unnecessary fuel consumption.
3Use of energy by moving object
If the air-fuel ratio is maintained lean to reduce fuel consumption, then fuel efficiency improves, but NOx storage capacity decreases
Solution Approach 1:
The system dynamically switches between maintaining lean air-fuel ratio (first method) and rich air-fuel ratio (second method) based on catalyst temperature and NOx storage requirements. This dynamic adjustment resolves the contradiction by temporarily enriching the mixture when NOx storage is needed while maintaining lean operation for fuel efficiency during normal conditions.
Solution Approach 2:
The patent implements periodic switching between lean and rich air-fuel ratio conditions. The system alternates between storing NOx during lean operation and releasing/reducing NOx during rich operation intervals. This periodic action allows the system to maintain both fuel efficiency and adequate NOx storage capacity over time.
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 allows for a high NOx purification rate across varying engine operating conditions by selectively using methods that adjust air-fuel ratios and hydrocarbon injection intervals, ensuring effective NOx removal even at high catalyst temperatures.
Implementation Method 1
an exhaust purification catalyst for reacting NOx contained in exhaust gas and hydrocarbons which are injected from the hydrocarbon feed valve and are partially oxidized
Implementation Method 2
hydrocarbons which are injected from the hydrocarbon feed valve and are partially oxidized
Implementation Method 3
a basic layer is formed on the exhaust purification catalyst
Data Source
AI summary
A method of purifying NOX contained in exhaust gas, the method including a first NOX purification method and a second NOX purification method, wherein the first NOX purification method and the second NOX purification method include injecting hydrocarbons into an exhaust gas passage at predetermined feed intervals, wherein in the first method, the injected hydrocarbons are partially oxidized and an air-fuel ratio flowing into an exhaust purification catalyst is lean, and in the second method, the injection of the hydrocarbons occurs at intervals longer than the predetermined feed intervals in the first method, and an air-fuel ratio is switched from lean to rich.