Boat Propulsion Device Intake Noise Reduction
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Solution Overview
Problem
Existing boat propulsion devices face challenges in reducing low-frequency noise, as conventional Helmholtz resonators require larger intake and exhaust devices to shift resonance frequencies, leading to increased size and design limitations.
Innovation Solution
The design incorporates a main intake or exhaust pipe with a connected extension pipe that includes a resonance chamber, where a partition wall closes the extension pipe except for a portion adjacent to the main pipe, allowing for angled connections and reduced size while maintaining noise reduction through air-column resonance, and enabling adjustable resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the volume of the resonance chamber is increased to shift the resonance frequency to the lower frequency side, then the noise reduction effectiveness is improved, but the size of the intake device or exhaust device becomes larger
Solution Approach 1:
The resonance chamber is nested within the extension pipe, utilizing the pipe's internal volume. The partition wall closes the extension pipe except for a portion adjacent to the main pipe, creating a compact resonator structure that does not increase overall device size while maintaining noise reduction effectiveness at low frequencies
Solution Approach 2:
The extension pipe extends from the connection between the first and second pipes in a direction that may be angled relative to the axial direction of the first pipe. This spatial arrangement allows the resonance chamber to be positioned in three-dimensional space without increasing the device's footprint, effectively utilizing available volume in alternative dimensions
2Object-affected harmful factors
If a conventional Helmholtz resonator is used for noise reduction, then the resonance frequency can be adjusted, but the device complexity and size increase
Solution Approach 1:
The resonance chamber is merged with the extension pipe structure, eliminating the need for a separate Helmholtz resonator assembly. The partition wall integrates the closure function directly into the pipe structure, simplifying the overall design while maintaining noise reduction functionality
Solution Approach 2:
The extension pipe serves multiple functions: it extends the main pipe connection, provides structural support, and houses the resonance chamber for noise reduction. This multi-functionality reduces the number of separate components needed, simplifying the overall device structure
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 reduces the size of intake and exhaust devices, facilitates design changes, and maintains noise reduction by utilizing the extension and main pipes as resonators, shifting resonance frequencies without increasing device size.
Implementation Method 1
including a resonance chamber therein, wherein the extension pipe includes a partition wall that closes the extension pipe except for a portion of the extension pipe adjacent to the main intake pipe
Implementation Method 2
Helmholtz resonators are commonly used as the resonator. The Helmholtz resonator has a neck portion that branches from the intake duct and a resonance chamber connected to the neck portion
Data Source
AI summary
An outboard motor includes an engine main body, and an intake device to supply air to the engine main body. The intake device includes a main intake pipe including a first intake pipe and a second intake pipe connected to a downstream end of the first intake pipe and extending at an angle with respect to an axial direction of the first intake pipe and through which the air supplied to the engine main body flows, and an extension pipe extending from a connection between the first intake pipe and the second intake pipe and including a resonance chamber therein. The extension pipe includes an extended peripheral wall and an end wall that closes the resonance chamber except for a portion adjacent to the main intake pipe.