Exhaust Purification Catalyst Dynamic Hydrocarbon 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 diminishes at high temperatures.
Innovation Solution
An exhaust purification system is implemented with a hydrocarbon feed valve and an exhaust purification catalyst downstream, where precious metal catalysts on a basic surface facilitate NOx reduction by varying the hydrocarbon concentration within specific amplitude and period ranges, controlling the injection of hydrocarbons to optimize NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the exhaust purification catalyst temperature increases, then the exhaust gas flow rate increases, but the NOx purification rate decreases
Solution Approach 1:
The patent applies dynamic control by periodically varying the hydrocarbon concentration in the exhaust gas flowing through the catalyst. This dynamic approach allows the system to adapt to high temperature conditions by creating oscillating rich and lean periods, enabling NOx reduction during rich periods while maintaining overall system efficiency even when the catalyst temperature is high
Solution Approach 2:
The patent implements periodic action by controlling the hydrocarbon feed valve to create cyclic variations in hydrocarbon concentration with specific amplitude and period parameters. This periodic injection creates alternating reducing and oxidizing environments within the catalyst, allowing NOx to be reduced during reducing phases while oxygen is replenished during oxidizing phases, thereby maintaining purification effectiveness at high temperatures
2Reliability
If the hydrocarbon concentration is increased to reduce NOx, then the NOx purification rate increases, but the formation of nitrates increases
Solution Approach 1:
The patent uses periodic action with carefully controlled amplitude and period parameters to create cyclic hydrocarbon concentration variations. During the rich phases, NOx is reduced, while during the lean phases, nitrates are decomposed and converted back to NOx or fully oxidized to CO2 and H2O. This periodic cycling prevents excessive nitrate accumulation while maintaining high NOx purification rates
Solution Approach 2:
The patent changes the concentration parameter of hydrocarbons dynamically by controlling the hydrocarbon feed valve opening degree and injection timing. By adjusting the amplitude and period of concentration variations, the system optimizes the balance between NOx reduction efficiency and nitrate formation prevention, allowing effective NOx purification without excessive nitrate storage
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 maintains a high NOx purification rate even at high catalyst temperatures by effectively reducing NOx in the exhaust gas and stored NOx, without forming excessive nitrates, thus overcoming the temperature-related decline in purification efficiency.
Implementation Method 1
an exhaust purification catalyst for reacting NOx contained in exhaust gas and reformed hydrocarbons is arranged inside of the engine exhaust passage downstream of the hydrocarbon feed valve
Implementation Method 2
a precious metal catalyst is carried on an exhaust gas flow surface of the exhaust purification catalyst
Implementation Method 3
a basic exhaust gas flow surface part is formed around the precious metal catalyst
Data Source
AI summary
In an internal combustion engine, inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged. At the time of engine operation, the amplitude of change of the concentration of hydrocarbons which flow into the exhaust purification catalyst (13) is made to become within a predetermined range of amplitude by control of the injection amount of hydrocarbons from the hydrocarbon feed valve (15), the concentration of hydrocarbons flowing into the exhaust purification catalyst (13) is made to vibrate by a predetermined range of period by control of the injection period of hydrocarbons from the hydrocarbon feed valve (15), and thereby the NOx contained in the exhaust gas and the NOx stored in the exhaust purification catalyst (13) are reduced.