TWO STROKE ENGINE

Two stroke engine-: As the name implies, the two stroke engine only requires two piston movement or one cycle. In two stroke engines , the two ideal cycle i.e. suction and exhaust stroke are eliminated ( in other words both are not have separate stroke ). So we have one power stroke per revolution of crank in two stroke engine.

                      In two stroke engine ports are used instead of the inlet and exhaust valves oprated by complicated mechanism. The engine is able to produce power after one cycle because intake and exhaust of the gas occur simultaneously. 

Two - stroke engine 

Two stroke engine contain two processes:-

1. Compression stroke -: In this stroke first the inlet port open, air-fuel mixture enters in the chamber and piston move upward. Movement of the piston from downward to upward compress the fuel mixture at high pressure ratio. due to compression temperature and pressure of fuel increase and now spark plug ignite and burn the mixture at this point compression stroke end.

2. Power stroke-: In the power stroke the brunt fuel gases exerted very high pressure on the piston ,due to this pressure piston move downward ( expansion) and waste or exhaust gases is out from the exhaust port due to piston movement. Now one cycle is complete. 

As compare to four-stroke engine , two stroke engines are lighter , more efficient and also have tha ability to use lower- grade fuel. Therefore the lighter engines results in a higher power to weight ratio.

Two stroke engine can proceed with intaking the fuel mixture as seen in processes --:

Process 1-2-: During process 1-2 inlet port open and piston at the bottom dead centre to come upward top dead centre . Now fuel-air mixture intake and piston move upward, compresse the fuel. Due to compression cause the mixture to increase temperature and pressure and no heat exchange in this process. This is a adiabatic process. At the end of the process fuel is met by the spark plug to be ignited. 

Process 2-3-: In this process, fuel is burn by the sapkr plug ignition and combustion of fuel occurs. Due to combustion high pressure heat is generated at this point this process is end. 

 P -V diagram of two stroke engine 

Process 3-4-: The thermal energy in the chamber as a result of combustion is used to do work on the piston which pushes the piston downward and increasing the volume of the chamber. This process also known as power stroke.

Process 4-1-: In this process 4-1 , all the waste gases is expelled from the engine chamber.  As the heat leave the gas , molecules lose kinetic energy causing the decreasing in pressure. There is no exhaust phase in a two stroke engine, so the cycle begins again by allowing the air-fuel mixture in the combustion chamber. 

Two stroke engines ideal for ships , motorcycles and lawnmower etc.