This site will look much better in a browser that supports web standards, but it is accessible to any browser or Internet device.
Clubs, glossaries, museums, shops and much more......
...all of your model making needs from one site.
The exhaust system on an internal combustion engine may be used to reduce noise and/or increase power. A pressure tapping is also used on many exhaust systems to pressurise the fuel tank and hence allow the engine to operate at any attitude.
C = speed of sound = 343m/s (at 20°C) this will be closer to 400m/s for typical exhaust gas temperatures seen in glow plug engines
This all looks horrific!
Lets simplify it and explain what it means.
Starting with the cross-sectional area of the pipes (S) and exhaust silencer (Sc).
Therefore, you may reduce the exhaust noise by reducing the basic pipe diameter that forms the manifold and link to the expansion chamber and the final pipe diameter on the outlet of the expansion chamber. The downside is reduced power and maximum engine speed.
Increasing the expansion chamber size will also reduce the noise from the exhaust system. This may be difficult to package.
The resonant frequency fn is dependent on the speed of sound (over which we have no control) and the length of the silencer (this we can choose to suit the installation).
Increasing the silencer volume by a large amount may not reduce the noise of your engine if there are other sources of noise. e.g. inefficient propeller design, engine is mounted directly to the airframe....
See also: Engines