Exhaust Catalyst Dihedral Angle for Uniform Flow
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Solution Overview
Problem
Existing engine exhaust devices with catalysts in series configurations face challenges in achieving uniform exhaust gas flow, leading to reduced efficiency, increased flow resistance, and limited mountability of control devices due to non-uniform flow and overlap configurations.
Innovation Solution
The engine exhaust device design features a configuration where a part of the side surface of the first catalyst is shorter than a predetermined range, facing the upstream end surface of the second catalyst, eliminating the need for a connecting flange and incorporating a wall step with a curvature radius to diffuse exhaust gas uniformly into the second catalyst, reducing flow resistance and enhancing mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If catalysts are arranged laterally with overlap to reduce area, then the area for catalysts is reduced, but the exhaust gas flow becomes non-uniform causing reduced catalyst efficiency and increased flow resistance
Solution Approach 1:
The exhaust passage is divided into distinct upstream and downstream segments with clear spatial separation. The first catalyst is positioned in the upstream segment while the second catalyst is positioned in the downstream segment, eliminating overlapping arrangements. This segmentation allows each catalyst to receive uniform exhaust gas flow independently, maintaining high catalyst efficiency while still achieving compact overall dimensions through optimized segment layout.
2Area of stationary object
If catalysts are arranged laterally with overlap to reduce area, then the area for catalysts is reduced, but the flow resistance increases decreasing output
Solution Approach 1:
By dividing the exhaust passage into separate upstream and downstream segments housing different catalysts, the design eliminates flow disturbances caused by overlapping structures. This segmentation ensures smooth, uniform exhaust gas flow through each catalyst bed, minimizing flow resistance and pressure losses, thereby maintaining high engine output while achieving compact catalyst arrangement.
3Area of stationary object
If small overlap is used between catalysts, then space is saved, but the mountability of control devices such as sensors decreases
Solution Approach 1:
The exhaust passage is segmented into distinct upstream and downstream sections with adequate spatial separation between catalysts. This segmentation creates sufficient mounting space in the connecting segment for control devices such as temperature sensors and oxygen sensors, while still maintaining a compact overall device footprint through optimized segment dimensions and arrangement.
4Productivity
If non-uniform exhaust gas flow occurs, then catalyst usage efficiency decreases, but flow resistance increases
Solution Approach 1:
The exhaust passage is divided into separate upstream and downstream segments, each housing a catalyst. This segmentation ensures that exhaust gas flows uniformly through each catalyst bed independently, maximizing catalyst usage efficiency. The segmented design also eliminates flow convergence and divergence issues that would increase flow resistance, maintaining low pressure losses throughout the system.
Data Source
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AI summary
An engine exhaust device includes: a first catalyst provided in an exhaust path of the engine to purify exhaust gas discharged from the engine; a second catalyst placed downstream of the first catalyst in a flow of the exhaust gas to purify the exhaust gas, which has passed through the first catalyst; and a connecting member shaped into a tube and forming a part of the exhaust path, and connecting the first catalyst to the second catalyst. A downstream end surface of the first catalyst and an upstream end surface of the second catalyst form a dihedral angle within a range from 60 degrees to 120 degrees. A part of the upstream end surface of the second catalyst is close to and faces a part of a side surface of the first catalyst. On a cross-section including a central axis of the first catalyst and being parallel to a central axis of a second catalyst, a length of the part of the side surface of the first catalyst is longer than or equal to 10% and shorter than 50% of an entire length of the first catalyst.