Silencer Design

Does anyone have any tips re designing a silencer(s) for a rotary piston (roots) type blower?

The silencers need to be relatively compact but still facilitate high gas flow (3500 cfm). Blower outlet is 10", frequency is ~240Hz (est.).

I am thinking of installing 2 silencers in series, one reactive (using baffles) and one absorptive (with deadening material). I am also looking into the possibility of incorporating a Helmholtz Resonator in the design.

Any advice will be welcome as I am very new to this.

Thanks.

Shane.
shanev@themutual.net

 

[Hatch]

A good reactive design with internal absorbtive chambers at the discharge end should provide the insertion loss you require. Adding multiple silencer configurations will result in a very long complex silencer and the resulting configuration will probably have a high pressure drop (which is important in silencer design).

When installing silencers on a rotary blower, the operating pressure is important. Is the silencer on the discharge side or intake side? If it is on the discharge side, then it may require "pressure vessel" certification and/or ACME flanges (higher cost). It is usually cheaper to purchase a reactive silencer (or any large silencer) rather than design and build a unit.

One other thing, the first chamber of a reactive silencer usually sees very high pressure, and velocity. It must be robust to withstand the pressure and corrosion (if there is some moisture in the flow stream).

 

[butelja]

I agree with Hatch that the first part of the silencer should be reactive. Absorptive silencers will tend to get their "guts blown out" by the severe pressure fluctations from a roots type blower. Have you checked the off the shelf offerings from silencer companies such as Stoddard Silencer or Universal Silencer? If there is a stock item it will save much time and $ compared to designing your own. Even if the stock silencers don't quite meet your requirements, they may give you design ideas.