scavenging 

Scavenging

what is  scavenging????

 it is the process of removing exhaust gases from the cylinder after combustion and replenishing with fresh air known as scavenging.

In a two stroke engine, cycle is completed in one revolution of crankshaft so gas exchange process at the end of power stroke has to occur when piston near BDC.
1st exhaust port or valve open and then scavenge port open by fresh charge AIR remaining is expelled from the cylinder.
Efficient scavenging is necessary for good combustion and it is required for replacing  exhaust .
scavenge air also assist cooling of cylinder,Piston cylinder head ,exhaust valve etc .
The term scavenging is used to describe the process riddling  the cylinder of burnt exhaust gases at the end of expansion stroke and early part of compression stroke .

Time available for scavenging process in two stroke engine is less than  four stroke .
Types of scavenging
1.cross scavenging
2.loop screening
3. uniflow scavenging

what do you mean by scavenging efficiency??????

Scavenging efficiency is equal to wt. of air enter into the cylinder divided by weight of air for stroke volume.

 what is the importance of scavenging
1. it affects overall efficiency efficienicy 2.power output per unit weight
3. fuel consumption per unit power
4. incomplete scavenging result in poor combustion
5. lubricating oil contamination
6 wear piston rings and liner
7.mean temperature of cylinder high

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