IC

1. IC Engines
Internal Combustion Engines:
An engine, such as a gasoline or diesel engine, in which fuel is burned inside the engine.
Designed to be run on any fuel that vaporizes easily or on any flammable gas .
External Combustion Engines:
An engine, such as a steam engine, in which fuel is burned outside the engine. Fuel is burned to
produce heat to make steam. Fuel burning can take place within a few feet of the engine to
several miles away.
Engine Classifications:
1) Thermodynamic cycle
 Otto Cycle (Heat produced or released at constant volume)
 Diesel Cycle
 Dual Combustion Cycle
2) Working cycle
 The number of working strokes required to do work.
2 stroke= 1 cycle completed in 2 strokes
4 stroke= 1 cycle completed in 4 strokes
3) Fuel
Engines are classified by the type of fuel used. Gasoline engines burn gasoline. Diesel
engines burn diesel fuel. Liquefied petroleum gas (LPG), gasohol (10% alcohol, 90%
gasoline), and pure alcohol can also be used to power an engine.
4) Fuel supplied or Method of fuel supply
 Atomizor
 Electric Fuel Injector
 Carborator
5) Method Of ignition
Two basic methods are used to ignite the fuel in an engine combustion chamber:

2. a. spark ignition (Uses an electric arc at the spark plug to ignite the fuel ) as in otto
engine.
b. compression ignition (Squeezes the air in the combustion chamber until it is hot
enough to ignite the fuel)as in Diesel Engine.
6) Methods of cooling
There are two types of cooling systems:
 Liquid cooling system
 surrounds the cylinder with coolant
 coolant carries combustion heat out of the cylinder head and engine block
 Air cooling system
 circulates air over cooling fins on the cylinders
 air removes heat from the cylinder
7) Speed Of Engine
 Low Speed Engine (Pump Water)
 Medium Speed Engine
 High Speed Engine (Sports Cars)
8) Field Of application
 Stationary Engines (Generators)
 Marine Engines (Ships)
 Automotive Engines (Cars)
 Airo Engines ( All applications related to air)
 Locomotive Engines (steam Engines)
9) Lubrication system
Pressure lubrication
10) Method Of control under variable loading
Load is controlled by quality and quantity of fuel.
 Quality:
Fuel rich mixture
Fuel lean mixture

3.  Quantity:
Chemically correct mixture
11) Basic Engine Design
 Single Cylinder Engine
 Multi Cylinder Engine ( V-type, Radial, Rotary)
12) Number Of cylinders
Most car and truck engines have either 4, 6, or 8 cylinders . Some may have 3, 5, 10, 12, or
16 cylinders. Engine power and smoothness are enhanced by using more cylinders .
13) Valve or Port Design
 Popit Valves ( 4 Stroke Engines)
 Over Head Valve ( At the Top Of the Cylinder)
 Inclined Valve
 Rotary valve
14) Combustion Chamber Design:
Shape Of chamber describes how efficient combustion take place. Combustion will be more
efficient if the mixing is better.
1) Wedge Combustion Chamber
2) Hemispherical combustion Chamber
3) Radial Combustion Chamber
Comparison Of 4 Stroke and 2 Stroke Engines:
4 Stroke Engines:
1) One power stroke in every 2 revolutions.
2) Heavier Flywheel
3) Power for same engine is less ( Larger in size)
4) Valves and valve operating mechanism
5) Initial cost high
6) Normally water cooled ( Less lubricant)
2 stroke Engines:
1) One power stroke in every 1 revolutions.
2) Lighter flywheel

4. 3) Power more ( Engine smaller)
4) Ports
5) Cost low
6) Air cooled ( more lubricant)
octane number
The octane number of a fuel indicates its resistanc e against self-ignition when put under
pressure. Two hydrocarbons are used as a reference: iso-octane and heptane, also called n-heptane.
The chemical formulas are C8H18 and C7H16, respectively.
The exact chemical structure of these hydrocarbons is not all that important for this
discussion. What matters is the fact that the two have rather different properties when it
comes to self-ignition. If you heat up the vapor of these hydrocarbons enough, and put it
under sufficient pressure (as in an internal combustion engine), it will eventually ignite (or
burn) by itself. Octane has a high resistance to self-ignition, heptane has a low resitance to
self-ignition.
We have to discuss this self-ignition stuff at this point. When gasoline is burnt inside an
internal combustion engine, the air-fuel mixture should ignite when the spark plug produces
a spark, and not any sooner. If the air-fuel mixture ignites too soon, very bad things
happen. Temperatures inside the cilinder spike, and the piston and valves will be damaged
severely. This phenomenon is called knocking, pinging (after the sound that it
produces), pinking, or pre-ignition.
Apparently there is a difference between knocking and pre-ignition. As far as I can
determine, knocking occurs when combustion of the air-fuel mixture starts at more than
one point in the combustion chamber. Pre-ignition seems to describe the situation when the
air-fuel mixture ignites even before the spark plug produces a spark. Pre-ignition is even
worse than knocking, apparently.
Back to the octane number. As we mentioned, octane has a high resistance agains
knocking, and heptane has a low resistance agains knoc king. A 50/50 mix of octane and
heptane would have a moderate resistance against knocking.