Air Nozzle with Protruding Shaft Core for Noise Reduction
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Solution Overview
Problem
Existing air nozzle technologies fail to effectively reduce noise caused by underexpanded jets while maintaining necessary impingement pressure, particularly when high-pressure air is used for cleaning workpieces.
Innovation Solution
An air nozzle design featuring a shaft core portion connected to a tubular portion via a connecting portion, where the shaft core protrudes from the tubular portion, forming an annular air ejection port between the small-diameter hole and the shaft core, which reduces noise by allowing the underexpanded jet to flow around the shaft core, thereby attenuating vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-pressure air is ejected from a conventional nozzle, then cleaning effectiveness is improved, but noise is significantly increased due to underexpanded jet
Solution Approach 1:
The nozzle outlet is segmented into an inner shaft core portion and an outer tubular portion, creating multiple flow paths. The high-pressure air flow is divided into a central jet and an annular flow, which interact to reduce noise while maintaining cleaning effectiveness.
Solution Approach 2:
The shaft core portion is nested within the tubular portion, with the shaft core inserted into a small-diameter hole of the tubular portion. This nested structure creates an annular air ejection port between them, allowing the underexpanded jet to flow around the shaft core and reduce noise through flow interaction.
2Object-generated harmful factors
If noise-reducing elements are added to the nozzle, then noise is reduced, but device complexity increases
Solution Approach 1:
Instead of adding complex noise-reducing elements inside the nozzle, the invention extracts the noise-reducing function to the nozzle outlet structure itself. The annular configuration and shaft core protrusion naturally guide the underexpanded jet flow to wrap around and attach to the shaft core, reducing noise without additional components.
Solution Approach 2:
The annular air ejection port acts as an intermediary between the high-pressure air source and the external environment. It creates a laminar flow that merges with the central air stream and induces ambient air, mediating the harsh underexpanded jet to reduce noise while maintaining cleaning performance.
3Object-generated harmful factors
If the shaft core portion protrudes further from the tubular portion, then noise reduction is improved, but impingement pressure decreases
Solution Approach 1:
The invention optimizes the protrusion length of the shaft core portion as a critical parameter. By setting the axial length within the specific range of 3-15 mm, the design achieves optimal balance between noise reduction and impingement pressure, allowing the underexpanded jet to attach to the shaft core effectively while maintaining sufficient cleaning pressure.
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
The design significantly lowers noise levels while maintaining or exceeding the impingement pressure requirements, as demonstrated by experimental comparisons with traditional single-hole and silencing nozzles, with optimal axial length of the shaft core portion between 3 mm and 15 mm for optimal performance.
Implementation Method 1
when high-pressure air is introduced into a tapered nozzle, the air becomes choked in the nozzle and the air is ejected from the tapered nozzle without fully expanding to the atmospheric pressure. This underexpanded jet has a shock cell structure in which shock waves and expansion waves appear alternately
Implementation Method 2
This underexpanded jet has a shock cell structure in which shock waves and expansion waves appear alternately
Implementation Method 3
the underexpanded jet to flow around the shaft core, thereby attenuating vibrations
Data Source
Figure 1
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AI summary
A shaft core portion (20) is connected to a tubular portion (12) via a connecting portion (22), the shaft core portion is inserted into a small-diameter hole (16) provided at the distal end of the tubular portion, protrudes from the distal end of the tubular portion, and an annular air ejection port (26) is formed by a gap existing between the wall surface of the small-diameter hole and the outer surface of the shaft core portion.