Exhaust Device Uniform Catalyst Flow
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Solution Overview
Problem
In internal combustion engine exhaust systems, the flow velocity and temperature distributions in catalyst carriers become non-uniform due to differing exhaust gas flow velocities and temperatures from collective and individual exhaust pipes, leading to early catalyst deterioration and potential cracks.
Innovation Solution
The exhaust device configures a collective exhaust pipe with a larger cross-sectional area than individual exhaust pipes, with the individual pipes merging near the catalytic converter and introducing exhaust gases at a more inclined angle, ensuring uniform flow velocity and temperature distributions across the catalyst carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If exhaust ports for some cylinders merge inside the cylinder head to form a collective exhaust pipe, then high-temperature exhaust gas is introduced to the catalytic converter for early activation, but the flow velocity distribution and temperature distribution in the catalyst carrier become non-uniform
Solution Approach 1:
The exhaust system is segmented into multiple independent exhaust pipes (first exhaust pipe for center cylinders, second exhaust pipe for end cylinders) rather than using a single collective exhaust pipe. This segmentation allows each pipe to be optimized independently for its specific cylinder group, maintaining uniform flow velocity and temperature distribution while still enabling early catalyst activation through the shorter first exhaust pipe.
2Productivity
If the passage cross-sectional area of the collective exhaust pipe is set larger than that of individual exhaust pipes, then exhaust gas flow is accommodated, but the flow velocity in the collective exhaust pipe becomes relatively slow causing exhaust gas to spread out and collide locally with the catalyst carrier
Solution Approach 1:
Instead of using one large collective exhaust pipe that reduces flow velocity, the system segments the exhaust flow into multiple smaller pipes (first and second exhaust pipes). Each pipe maintains higher flow velocity appropriate for its cylinder group while collectively accommodating the total exhaust gas flow, preventing local collision and spreading issues at the catalyst carrier.
3Speed
If individual exhaust pipes connect directly to the catalytic converter with high flow velocity, then exhaust gas reaches the catalyst quickly, but the exhaust gas locally collides with a part of the end surface of the catalyst carrier causing non-uniform distribution
Solution Approach 1:
The exhaust system applies different pipe configurations to different cylinder groups based on their specific requirements. The first exhaust pipe serving center cylinders has optimized characteristics for early catalyst activation, while the second exhaust pipe serving end cylinders is configured to ensure uniform distribution. This local quality approach allows each pipe to be tailored to its specific function, achieving both high velocity and uniform distribution.
Data Source
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AI summary
In inline four cylinder internal combustion engine (1), exhaust ports for a #2 cylinder and a #3 cylinder merge inside cylinder head (3) and form an opening serving as a single collective exhaust port. Exhaust manifold (5) has individual exhaust pipes (6, 7) for #1 and #4 cylinders and collective exhaust pipe (8), and the leading ends of these three exhaust pipes (6, 7, 8) are connected to catalytic converter (11). Exhaust gas introduction angle (θ2) of each of individual exhaust pipes (6, 7) is larger by 30-60 degrees than exhaust gas introduction angle (θ1) of collective exhaust pipe (8). Consequently, flow velocity distribution and temperature distribution in a catalyst carrier become uniform.