I talked with Ron at Spintech about a group buy of 2 into 1

cruiser

mufflers fabricated from
 > >> 321 stainless.

If you are thinking of not collecting the headers before the muffler

you will

be leaving a bunch of power on the table.

Lynn E. Hanover

I agree. As one pulse travels through the collector it's inertia
cause a low pressure pulse in the other pipe which of course
increases the exhaust flow out of the other rotor 180 degrees
out of phase.


Paul Lamar

If the 13B, which is 180 degrees out of phase needs a 31" header for maximum
power at 6500 rpm, then what header length would a 3-rotor, which is 120
degrees out of phase need in order to maximize power at the same rpm?  Seems
to me that something less than 31", like maybe 20-24" would provide more
scavaging.  Or, am I missing the bigger picture here?

First a collector system won't work on a three rotor.
Tuned pipes will help of course.

The exhaust pulse travels down the pipe at the speed of sound.
As the RPM changes the distance between the pulse changes.
Higher RPM shorter distance. Optimum length occurs as one
pulse is leaving the collector and another is being emitted by
the engine. 

The speed of sound is about 880 feet per second.
Each rotor fires once per rev. At 6000 RPM or 100 RPS
pulses are every 1/100 of a second apart or .01 second.
It takes the pulse about .003 seconds to travel 32 inches.
That is an exact multiple of .01 second. So the pressure
wave is bouncing back and fourth in the pipe three times
and the low pressure part of the wave arrives back at
the exhaust port just as the port opens again. This 
also sync's in the collector enhancing the low pressure
part of the wave in the other pipe. Multiples of 32 inches
also work such as 16 inches at 6000 RPM.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2002 All world wide rights reserved.