Investigating the Sound Reflector of a Gas Inlet Tube

In summary: This would create a more uniform distribution of gas and possibly result in a square wave shape. It would be interesting to experiment with different gas inlet configurations and see the effect on the flame shape. In summary, the conversation discusses the theory behind a Ruben's tube and potential issues with the gas inlet and sound reflector. Suggestions are made to improve the design, including changing the gas inlet location and experimenting with different configurations to achieve a square wave shape.
  • #1
pkc111
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TL;DR Summary
Ive built a prototype Rubens tube from aluminium 50mm diameter and 1.2m long. It runs on natural gas. With a 1 inch flame I can get a nice node within the first 30cm of the speaker end of the tube only (only at certain frequencies that match the expected resonance frequencies). My problem is nothing happens at the other end (gas inlet) even at higher resonance frequencies. If I raise the volume they start to appear but then the ones at the speaker end roar and then blow out.
My theory is that the gas inlet end, which is supposed to act as a sound reflector may not be doing a great job because it is plastic and has a hole cut in the centre for the gas inlet port. But by that reasoning, the flames at the end most distant from it (the sound inlet end) should be the hardest standing waves to create, but the opposite is true, they are the easiest to create with the smallest sound volume required.
Ive attached a photo of the tube at low volume sound and you can see the reduction in flame height (node) at the left hand end only (sound inlet).
Any ideas would be appreciated.
Many thanks
 

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  • #3
If you think of that tube as a resonant structure, then all of those holes along it's length would represent losses. I wonder if there's too much damping by the time you get to the end. It would be interesting to know what would happen if you had tiny holes, or maybe if you plugged a bunch of them.
 
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  • #4
I think you might need a perfect seal for the speaker, a flat heavy plate at the far end and a small gas inlet tube on the side. I have seen one operated with very large flames, but the one offered by an equipment supply company does show small flames.
 
  • #5
tech99 said:
I think you might need a perfect seal for the speaker, a flat heavy plate at the far end and a small gas inlet tube on the side. I have seen one operated with very large flames, but the one offered by an equipment supply company does show small flames.
Thank tech99 I am thinking the same thing. I will change the gas entry to the centre of the tube and place a hard plate at the end. The speaker end is perfectly sealed witha balloon so there shouldn't be much problem there. I just tried with propane and its a lot better.
Although the flames now have a square sort of shape. Is it possible to get a square sound wave in a Ruben's tube??
My sound generator is sine wave.
 
  • #6
pkc111 said:
Thank tech99 I am thinking the same thing. I will change the gas entry to the centre of the tube and place a hard plate at the end. The speaker end is perfectly sealed witha balloon so there shouldn't be much problem there. I just tried with propane and its a lot better.
Although the flames now have a square sort of shape. Is it possible to get a square sound wave in a Ruben's tube??
My sound generator is sine wave.
Regarding the square wave, I am wondering if the gas inlet needs to be large and the individual holes small.
 

1. What is a sound reflector and how does it work?

A sound reflector is a device that redirects sound waves in a specific direction. In the case of a gas inlet tube, it is used to direct sound waves towards the gas source. This is achieved through the use of reflective surfaces, such as curved or angled walls, which bounce the sound waves in the desired direction.

2. Why is it important to investigate the sound reflector of a gas inlet tube?

Investigating the sound reflector of a gas inlet tube is important because it can affect the efficiency and accuracy of the gas flow measurement. If the reflector is not functioning properly, it can cause sound waves to be scattered or absorbed, leading to inaccurate readings. Additionally, a faulty reflector can also result in noise pollution and potential safety hazards.

3. What factors can affect the performance of a sound reflector?

The performance of a sound reflector can be affected by various factors, such as the shape and size of the reflector, the material it is made of, and the angle at which the sound waves hit the surface. Other factors include the presence of any obstructions or imperfections on the surface of the reflector, and the distance between the sound source and the reflector.

4. How can the sound reflector of a gas inlet tube be tested?

The sound reflector of a gas inlet tube can be tested using various methods, such as acoustic testing, laser scanning, or computational fluid dynamics (CFD) simulations. Acoustic testing involves measuring the sound pressure level at different points around the reflector to determine its effectiveness. Laser scanning can provide detailed 3D images of the reflector's surface, allowing for analysis of any imperfections. CFD simulations use computer modeling to predict the behavior of sound waves in the presence of the reflector.

5. Can the sound reflector of a gas inlet tube be improved or optimized?

Yes, the sound reflector of a gas inlet tube can be improved or optimized through design modifications or adjustments. This can involve changing the shape or size of the reflector, using different materials, or adjusting the angle at which the sound waves hit the surface. Testing and analysis, such as those mentioned in the previous question, can help identify areas for improvement and guide the optimization process.

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