This document discusses a presentation on two-stroke petrol engines given by three students - Shahzaib Akhtar, Hassan Abbas Niazi, and Abdullah Saddiq. It defines the basic components of a two-stroke engine like the piston, connecting rod, crankshaft, and spark plug. It explains that in a two-stroke engine, the intake, compression, power, and exhaust strokes are completed in two strokes of the piston rather than four. The intake and exhaust ports are opened and closed by the piston's motion rather than valves. The document outlines the working principle, advantages like lighter weight and lower cost, disadvantages like lower efficiency, and common applications of two-stroke engines.

2. Swedish College of Engineering & Technology
Lab Incharge : Engr.Shah Nawaz
Department : Mechanical
Semester : 3rd
Topic : 2 Stroke Petrol Engine
Subject Name : Thermodynamics-2
Active Learning assignment

3. Prepared by:
Name
 Shahzaib Akhtar
 Hassan Abbas Niazi
 Abdullah Saddiq
Enrollment no.
 14F-UET-ME-013
 14F-UET-ME-014
 14F-UET-ME-012

5. Presentation Topic-
Two Stroke Engine

6. Stroke
 Reciprocating motion used in reciprocating engines and other mechanisms is back
and fourth motion .Each cycle of reciprocation consists of two opposite motions ,
there is a motion in one direction and then a motion back in the opposite direction .
Each of this motion is called stroke.

7. 2 stroke
A two-stroke petrol engine is an internal combustion engine that completes the
process cycle in one revolution of the crankshaft . Thus one power stroke is obtained
in each revolution of the crank shaft.

8. Basic parts of 2-stroke petrol engine
 Piston
 Piston Ring
 Spark plug
 Connecting rod
 Crankshaft

9. Spark Plug
 Electronic match is used to begun the combustion process of burning air and petrol
to create heat.
 It provides the means of ignition when the petrol engine’s piston is at the end of
compression stroke close to Top Dead Central (TDC)

10. Connecting rod
 Connects the piston and piston point to the crankshaft

11. Piston
 A sliding plug that harness the force of the burning gases in the cylinder

12. Crankshaft
 Along the piston pin and the connecting rod is converts the up and down motion (
reciprocating ) of the engine to spinning (rotary) motion

13. Working & parts of 2-Stroke
As the name itself implies, all the processes in the two stroke
cycle engine are completed in two strokes. These engine have 1
power stroke per revolution of the crankshaft.
In the two stroke engine there is a two opening called ports are
provided in place of valve of four stroke engines.
These ports are opened and closed by reciprocating motion of
the piston in the cylinder.
One port known as a inlet port and another port is known as a
exhaust port.
Two stroke engine consist of a cylinder with one end fitted with a
cylinder head and other end fitted with a hermitically sealed
crankcase which enables it to function as a pump in conjuction
with the piston.
Transfer port
Crank case
Exhaust port

14. Working Principle of 2 stroke
 Here suction and exhaust strokes are eliminated . Instead of valves , ports are used.
 The exhaust gases are driven out of the cylinder by the fresh fuel entering the cylinder.
 The intake & exhaust are controlled by movement of piston.
 The fresh fuel enter to cylinder due to difference of pressure.
 The fuel is compressed by the pumping action of the piston due to the design of
crankcase.
 As the piston continues to move upward , exhaust and transfer port get closed and the
compression is continued.
 In the end of the compression the spark is created which ignites the fuel & in result of
combustion thrust the piston moves from TDC to BDC.

15. This cycle is repeated continuously

16. Video clips…….

17. Advantages
 The power developed will be nearly twice that of four stroke engine of same
dimension and operating at the same speed
 The work required to overcome the friction of the exhaust and suction strokes is
saved
 Low weight
 Construction is simple
 Low thermal efficiency.
 Can run at higher speeds (5000 rpm)
 Low maintenance cost

18. Disadvantages
 As working on otto-cycle , a part of the fresh mixture is lost through exhaust port
 Part of the piston stroke is lost
 Heavy consumption of lubricating oil
 Two-stroke engines are not fuel efficient, so we would get fewer miles per gallon.

19. Use of 2-stroke engine
 Dirt Bike
 Lawn mowers
 Outboard engines
 Chain saws
 Line Trimmers
 Jet Skis
 Snowmobiles
 Model Air Planes
 Light Motorcycles
 Go Karts
 Ultra lights
 Scooters
Go-Karts

20. Example picture-
Dirt Bike Jet Skis
Chain sawsLawn mowers