Split Exhaust Passage Layout to Protect an Auxiliary Catalyst
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Solution Overview
Problem
In existing exhaust systems, the auxiliary exhaust catalyst on the upstream side is prone to thermal degradation due to excessive exhaust gas flow during high-flow operation regions, leading to potential damage and reduced effectiveness.
Innovation Solution
The exhaust system includes separate first and second exhaust passages with independent flow control, allowing the auxiliary exhaust catalyst to be protected by reducing its exposure to high-flow exhaust gas, and utilizing a flow amount adjustment unit and controller to manage exhaust gas distribution based on engine operation states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary exhaust catalyst is provided on the upstream side to purify exhaust gas, then exhaust gas purification is improved, but the auxiliary exhaust catalyst is exposed to large amounts of exhaust gas during high-flow operation, causing thermal degradation
Solution Approach 1:
The exhaust passage is segmented into a first exhaust passage containing the auxiliary exhaust catalyst and a second exhaust passage without catalyst. This segmentation allows exhaust gas to be divided into two separate flows, enabling the auxiliary catalyst to process only a portion of the total exhaust gas, thereby reducing thermal exposure while maintaining purification effectiveness.
Solution Approach 2:
The system changes the flow distribution parameter by dynamically controlling the split ratio between the first and second exhaust passages. During high-flow operation, more exhaust gas is directed through the second passage, reducing the thermal load on the auxiliary catalyst in the first passage while maintaining overall purification performance.
2Productivity
If exhaust gas flow through the auxiliary exhaust catalyst is increased to improve purification capacity, then exhaust gas treatment is enhanced, but the auxiliary exhaust catalyst suffers from thermal degradation
Solution Approach 1:
The exhaust flow is segmented into two independent passages, with the auxiliary catalyst positioned only in the first passage. This allows the system to maintain high overall treatment capacity through the second passage while protecting the auxiliary catalyst from excessive thermal exposure by limiting its exposure to a controlled portion of the exhaust flow.
Solution Approach 2:
The second exhaust passage acts as an intermediary route that handles the high-volume, high-temperature exhaust flow during peak operation, thereby shielding the auxiliary exhaust catalyst in the first passage from the full thermal burden while still contributing to overall exhaust gas treatment.
Data Source
AI summary
An exhaust passage includes a first exhaust passage which is opened and closed by a first exhaust valve, a second exhaust passage through which exhaust gas is caused to flow independently from the first exhaust passage and which is opened and closed by a second exhaust valve, and a third exhaust passage in which the first exhaust passage and the second exhaust passage merge together, and exhaust catalysts include a main exhaust catalyst which is provided in the third exhaust passage and an auxiliary exhaust catalyst which is arranged in the first exhaust passage and has a smaller capacity than the main exhaust catalyst.