use of ORIFICE for controlling pulsation by pressure wave

[MHKIM]

I am looking for any information regarding pulsation control in exhaust system.

In two stroke engine, many cylinders are connected to one common exhaust pipe(plenum). Therefore, those pressure waves resulted from the blowdown and the reflected ones.

And the pulsation amplitude may become unexpected large.
Then, engine performance will be less.

I've heard that the simplest way to control the pulsation is to insert orifices in the exhaust pipe(plenum)

Therefore, I'd like to get any information of the theoritical approach for use of orifice.

Could you please help me?

 

[richdubbya]

I know the practical but not the theoretical. The end of the expansion chamber is closed off and good wave reflection is retained. A small tube is inserted perpendicular to the wave directions into the expansion chamber to bleed off the pressure. The tube is sized just big enough to handle the max exhaust flow.

 

[richdubbya]

I am not sure i was clear. each cylinder has a seperate expansion chamber, the orfices merge to a plenum.

 

[magnograil]

Check NACA report 1192. They made theoretical calculations and experimental measurements on 77 muffler designs including the Quincke tube (quarter wave side branch).

 

[Tmoose]

Gordon Jennings suggests if the "stinger" restriction is too much, overheating will result. IF the individual pipes end abruptly at the plenum wall (no diverging taper)AND the plenum length/width/height is much larger than the pipe diameter then pressure waves bouncing around the plenum will not efficiently re-enter the small pipes ( or leave through small exit holes).

If this a modern design from a big name brand manufacturer then I suspect a LOT of thought and testing has gone into it. I would make my modifications removable.