Outboard Engine Gear Case Protruding Section for Noise Reduction
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Solution Overview
Problem
Outboard engine units experience unwanted noise due to vortex water flows that suck in engine exhaust gas, which current designs fail to adequately address.
Innovation Solution
The outboard engine unit incorporates a protruding section on the gear case's side surface, positioned rearward of the exhaust port, which diverts water flows away from the horizontal central axis, reducing the size of the separation region behind the gear case and minimizing vortex water flows that can suck in exhaust gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the exhaust port is positioned near the anti-cavitation plate, then the exhaust gas can be discharged efficiently, but vortex water flows suck in the exhaust gas and produce unwanted noise
Solution Approach 1:
A protruding section is introduced as an intermediary structure between the exhaust port and the separation region. This protruding section acts as a physical barrier that redirects water flows away from the exhaust port area, preventing vortex water flows from sucking in exhaust gas and eliminating the noise problem while maintaining exhaust discharge efficiency
Solution Approach 2:
The protruding section extends in a direction perpendicular to the main water flow direction, creating a three-dimensional obstruction that effectively blocks the path of vortex water flows without interfering with the vertical exhaust gas discharge path, thus resolving the contradiction between exhaust efficiency and noise reduction
2Device complexity
If water flows are allowed to flow freely along the side surface, then the flow path is simple, but the separation region behind the gear case becomes large and produces noise
Solution Approach 1:
The side surface of the gear case is segmented by adding a protruding section that divides the continuous water flow path into different regions. This segmentation redirects water flows away from the separation region without requiring complete restructuring of the water flow path, thus reducing noise while maintaining relatively simple overall design
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 design effectively reduces the size of the separation region and the amount of vortex water flows that release noise to the atmosphere, thereby decreasing unwanted noise levels.
Implementation Method 1
a protruding section provided on the side surface of the gear case at a position located rearwardly of the exhaust port, the protruding section protruding laterally outwardly from the side surface for changing a direction of water flows flowing along the side surface
Implementation Method 2
If the first and second surfaces of each of the protruding sections are interconnected by a sharply-angled surface, new vortexes and turbulence of water would be produced by the sharply-angled surface. However, the present invention, where the first and second surfaces of the protruding section are interconnected by the gently curved surface, can reliably prevent such new vortexes and turbulence of water
Data Source
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AI summary
Outboard engine unit (10) includes: an anti-splash plate (27) and an anti-cavitation plate (28) provided on a gear case (15) at a vertical interval from each other and extending horizontally from the gear case; an exhaust port (31) provided in a side surface (32) of the gear case for discharging exhaust gas from an engine (11); and protruding section (33) provided on the side surface of the gear case at a position located rearwardly of the exhaust port (31), the protruding section (33) protruding laterally outwardly from the side surface for changing a direction of water flows flowing along the side surface.