Gases ejected from an engine as waste products.
An exhaust system of an internal combustion engine performs a number of functions. The main features that must be considered are:
- Acoustic design - Acoustic Ducts, Acoustic Filter Elements.
- Construction and manufacturing process
- Dynamic tune
- Emissions control
- Exhaust system backpressure
- Orifice position
- Shell radiated noise
- System mounting and structural coupling
- Thermal stress
- Turbo/super charging
The layout shape of the exhaust system will be determined by the position of the exhaust outlet on the cylinder head, the obstacles the exhaust has to negotiate on its way down the underside of the vehicle, the position of silencers and the final position of the orifice itself.
At this stage the first acoustic mode of the system has been set by the overall length of the pipe (first mode of a pipe closed at one end valve face and open at the other exhaust tailpipe orifice), although there will be some changes depending on silencer internals, exhaust gas temperature along the length of the system (affecting the basic speed of sound in the gas), exhaust pipe diameters (hence gas flow rate) and a number of other minor effects.
Subjects: Mechanical Engineering