Intake Silencing Techniques 2

[Superfry]

I am working on a weight/noise reduction contract for a small military generator. I am trying to investigate methods of reducing intake noise and was wondering if anyone has any experience they can share on the subject. I've seen one type of intake silencer using a tubular silencing technique that uses specific length tubes protruding into the intake filter housing, but I have no idea as to how to size the tubing or plenum, etc. The engine is a yanmar L48 single cylinder diesel, 211cc.
Thanks in advance for any info.
-Tony

 

[alochin]

Interesting, this looks a lot like impedance matching on Radio electronic systems.

This is what we use to impedance match our prototype circuits:

http://www.maurymw.com/products/rfdcs/mantunrs/mntnrs3/mntnrs3.htm

This is for Radio circuit, and has nothing to do with engine, except the theory is amazingly similar.

A triple stub will match anything, but will be very narrow band. We match our RF transistors with that, then use software to design a matching cell according to the length of the quarter-wave tubes.

Also, the stubs are not quarter wave length, but slightly different, the difference being whatever reactive impedance is required to cancel the disturbance.

To empirically match your intake, built a triple stub of enough length, and then adjust each stub. I would be curious to know if it works!

One other point, in a radio circuit, matching the input will affect the output impedance, so we need to match both.