Multi-Cylinder Engine Exhaust Port Cooling Design
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Solution Overview
Problem
The existing cooling structure for multi-cylinder internal combustion engines with an exhaust collecting part in the cylinder head lacks effective cooling of exhaust gas, leading to thermal deterioration of the catalyst due to uneven exhaust temperatures between cylinders.
Innovation Solution
The design includes exhaust ports that extend from each cylinder's port openings, merging outside the joining surface of the cylinder head, increasing the surface area in contact with exhaust gas and adjusting the partitioning wall lengths to balance cooling effects across cylinders, thereby reducing temperature variations and preventing thermal deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If exhaust ports are made short and merge close to the combustion chamber, then device complexity is reduced, but the surface area in contact with exhaust gas is insufficient and cooling effect is inadequate
Solution Approach 1:
The exhaust ports are designed to extend in the axial direction of the crankshaft beyond the joining surface, utilizing the third dimension (depth/length along crankshaft axis) to increase the cooling surface area without increasing radial or lateral complexity. This allows the exhaust ports to achieve sufficient length for effective cooling while maintaining a compact overall structure.
2Ease of manufacture
If exhaust ports for inner and outer cylinders are made equal length, then manufacturing is simplified, but exhaust temperature variation between cylinders cannot be balanced
Solution Approach 1:
The exhaust ports are designed with different lengths according to their specific positional requirements: inner cylinder exhaust ports extend to a first axial position while outer cylinder exhaust ports extend to a second axial position. This local differentiation allows each exhaust port to be optimized for its specific thermal conditions, balancing exhaust temperatures across all cylinders and preventing catalyst thermal deterioration.
3Temperature
If exhaust ports extend beyond the joining surface, then cooling surface area is increased and cooling effect is improved, but device complexity increases
Solution Approach 1:
The exhaust port system is segmented into individual ports for each cylinder that extend independently beyond the joining surface. Each exhaust port is formed as a separate passage with its own length and configuration, allowing optimized cooling for each cylinder while maintaining manufacturing simplicity through standardized formation processes.
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 configuration effectively cools the exhaust gas by increasing the surface area in contact with the exhaust ports, balances exhaust temperatures between cylinders, and prevents thermal deterioration of the catalyst, ensuring proper cooling and extended catalyst life.
Implementation Method 1
the surface area of the exhaust port in contact with the exhaust gas is not large. The cooling effect is not as great as expected
Data Source
AI summary
The disclosure provides a multi-cylinder internal combustion engine having a cylinder head that includes an exhaust port capable of cooling exhaust gas more effectively. The cylinder head includes: a first ceiling surface that closes a first cylinder having a cylinder axis separated from an exhaust opening by a first distance; a second ceiling surface that closes a second cylinder having a cylinder axis separated from the exhaust opening by a second distance shorter than the first distance; and an exhaust port that extends toward the exhaust opening from two port openings which are open to a combustion chamber for each individual cylinder. The exhaust port individually extends from each of the port openings and merges with each cylinder outside a joining surface of the cylinder head for a cylinder block in a plan view.