This document discusses internal combustion engines. It describes the two main types as four-stroke and two-stroke engines, with two-stroke completing a cycle in one crankshaft revolution and four-stroke in two revolutions. The two types of internal combustion engines are also identified as petrol/gasoline engines which use a carburetor to mix fuel and air before ignition by a spark plug, and diesel engines which compress only air and inject fuel to ignite via compression heat. Key features of diesel engines are discussed as being eco-friendly with less carbon monoxide, more efficient fuel burning, durable requiring less maintenance, and compact with less noise. The basic working components and cycles of two-stroke engines are outlined.

1. AENG 251- Farm Power and Machinery
Er. N. Hari
Assistant professor
Department of Agricultural Engineering
Agricultural College, Aswaraopet
PROF. JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Rajendranagar, Hyderabad – 500 030

2. classified in two types
They are four stroke and two stroke engines.
1. When the cycle is completed in two revolutions of the
crankshaft, it is called four stroke cycle engines.
2. When the cycle is completed in one revolution of the
crankshaft, it is called two stroke cycle engines.
classification of Internal combustion engines

3. I.C. engines are of two types: (i) Petrol engine (carburetor type, spark ignition
engine), and (ii) diesel engine (compression ignition engine).
Petrol engine: It is the engine, in which liquid fuel is atomized, vaporized and
mixed with air in correct proportion before entering onto the engine cylinder
during suction stroke. The fuel is ignited in the cylinder by an electric spark.
Diesel engine: In this engine, during suction stroke, only air is entered into the
cylinder and compressed. The fuel is injected through fuel injectors and ignited
by heat of compression.

4.  Eco-friendly: It is also known to be eco-friendly as it
helps to shorten the amount of carbon monoxide
released into the air.
 Efficient Properties: compared to other types of fuels
diesel engine has a better burning properties.
 Durable: this engine requires less maintenance so it
tends to last for a long period of time and this are also
considerably durable compared to its counterparts.
 Less Noisy and Compact: This is another advantage of
these engines because it is less noisy and compact in
size.
Features of Diesel Engine

5. Working components of I.C.Engine

6. Working of two stroke cycle engine

8. Scavenging: The process of removal of burnt or exhaust gases
from the engine cylinder is known as scavenging. Entire burnt
gases do not go out in normal stroke, hence some type of blower
or compressor is used to remove the exhaust gases in two stroke
cycle engine.
When the piston is at the top of its stroke, it is said to be at the
top dead centre (TDC). When the piston is at the bottom of its
stroke, it is said to be at its bottom dead centre (BDC). In two
stroke cycle engine.

14. Key points
 The pressure in the engine cylinder is less than atmospheric
pressure during this stroke in Suction stroke
Both valves are closed during this stroke in Compression stroke
there is only one power stroke and three idle strokes.
Scavenging: The process of removal of burnt or exhaust gases
from the engine cylinder is known as scavenging.
Thermal efficiency varies between 32 and 38% in Diesel engine
Thermal efficiency varies between 25 and 32% in Petrol engine