Scavenging in the engine is the process of releasing of burnt gases from the cylinder and entering fresh charge inside the engine cylinder.
Scavenging occurs when both the inlet valve and exhaust open at the same time, which is happen at the ending of the exhaust stroke.
Scavenging is an important process for the engine to remove the remaining burnt gases from the engine otherwise if these gases mix with a fresh charge causes improper combustion and results in low power output.
Hence If the scavenging process is not done properly in an engine, then it causes chances of auto-ignition, decreases the engine efficiency as well reduces the power output.
The 2 stroke engines don’t have sufficient time for scavenging during valve overlapping as like 4 stroke engines. Thus different types of scavenging are used in two strokes engines.
Types of engine scavenging:
There are three types of scavenging which are as follows:-
- Cross-flow scavenging
- Uniflow scavenging
- Reverse or loop scavenging
1] Cross-flow scavenging:-
In the cross-flow scavenging, the inlet port is located at one side of the piston and the exhaust port is located at the other side piston means valves are at opposite sides to each other as shown in the above figure.
2] Uniflow scavenging:-
In the uniflow scavenging, the inlet ports are located at the sides of the piston as well as exhaust port is mounted at the top of the engine cylinder.
3] Reverse or loop scavenging:-
In loop or reverse scavenging, both the intake port and the exhaust port are located at the same side of the engine cylinder.