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:

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

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

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 resistance 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 knocking. A 50/50 mix of octane and

heptane would have a moderate resistance against knocking.