Exhaust Gas Purification Catalyst Deterioration Control
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Solution Overview
Problem
Exhaust gas purification catalysts in internal combustion engines tend to deteriorate when the temperature is high and oxygen is supplied, especially when a turbine is positioned upstream, causing exhaust gases to diffuse widely before reaching the catalyst, leading to potential deterioration across a wide range.
Innovation Solution
The system controls the degree of opening of the turbo bypass valve and throttle valve during fuel cut processing to minimize the flow of diffused exhaust gases into the catalyst, with the turbo bypass valve being closed and the throttle valve opened wider when the catalyst temperature exceeds a predetermined level, directing bypass exhaust gases to flow directly into the catalyst's upstream end face through a narrower passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the turbine is arranged in the exhaust passage at the upstream side of the exhaust gas purification catalyst, then the exhaust gas can be driven through the turbine to generate power, but the exhaust gas tends to diffuse before flowing into the catalyst, causing deterioration in a wide range of the catalyst
Solution Approach 1:
The exhaust passage is segmented into a first exhaust passage (through the turbine) and a second exhaust passage (bypassing the turbine). A bypass passage connects these two passages, allowing selective routing of exhaust gas. This segmentation enables control over whether exhaust gas flows through the turbine or bypasses it, preventing unwanted diffusion into the catalyst while still allowing power generation when needed.
Solution Approach 2:
A bypass valve is introduced to dynamically control the flow distribution between the first and second exhaust passages. The bypass valve can adjust its opening degree based on operating conditions, enabling the system to switch between turbine-driven mode (for power generation) and bypass mode (to prevent catalyst deterioration from diffused exhaust gas).
2Object-affected harmful factors
If the degree of opening of the wastegate valve is made larger during fuel cut processing when catalyst temperature is high, then exhaust gas diffusion is suppressed, but the flow speed of exhaust gas becomes slow, making diffusion more likely and causing catalyst deterioration in a wide range
Solution Approach 1:
The bypass passage acts as an intermediary pathway that receives exhaust gas from the first exhaust passage (after the turbine) and directs it to merge with the second exhaust passage (before the catalyst). This intermediary structure allows the system to control flow characteristics separately: the wastegate valve controls the amount of exhaust gas, while the bypass passage geometry and bypass valve control the flow speed and direction, preventing diffusion before the exhaust gas reaches the catalyst.
Solution Approach 2:
The system changes the flow parameters by introducing the bypass passage with specific geometry (narrower at the outlet) and controlling the bypass valve opening degree. This allows adjustment of exhaust gas flow speed and distribution, enabling the exhaust gas to maintain sufficient speed to prevent diffusion while still protecting the catalyst from deterioration during fuel cut processing at high temperatures.
3Ease of operation
If the bypass passage has a larger diameter, then exhaust gas flow is easier, but the exhaust gas diffuses more before reaching the catalyst, causing deterioration in a wide range
Solution Approach 1:
The bypass passage is designed with varying diameter along its length - larger at the inlet to accommodate exhaust gas from the turbine and narrower at the outlet to prevent diffusion. This parameter change in geometry allows the passage to easily receive and transport exhaust gas while maintaining sufficient flow velocity and preventing unwanted diffusion before the exhaust gas merges with the main flow entering the catalyst.
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 the deterioration of the exhaust gas purification catalyst by reducing the inflow of diffused exhaust gases and increasing the flow speed of bypass gases, ensuring they enter the catalyst through a narrower range, thereby minimizing catalyst deterioration.
Implementation Method 1
the bypass passage is constructed so as to direct a direction of flow of bypass exhaust gas, which is exhaust gas flowing out from the bypass passage into the exhaust passage, toward the upstream side end face of the exhaust gas purification catalyst
Implementation Method 2
an exhaust gas purification catalyst having an ability to store oxygen in exhaust gas
Data Source
AI summary
The deterioration of an exhaust gas purification catalyst is suppressed as much as possible. An exhaust gas purification system for an internal combustion engine comprising: a throttle valve; a turbocharger; an exhaust gas purification catalyst; a bypass passage; a turbo bypass valve (TBV); and a controller. The controller is configured to carry out fuel cut processing and deterioration suppression control. In the deterioration suppression control, when a temperature of the exhaust gas purification catalyst is equal to or higher than a predetermined temperature in the course of the execution of the fuel cut processing, the degree of opening of the TBV becomes smaller, and the degree of opening of the throttle valve becomes larger, than when the temperature of the exhaust gas purification catalyst is lower than the predetermined temperature in the course of the execution of the fuel cut processing.