Introduction to Engines

By Janith Shehan

Engines are the power source for propulsion systems for land, water and air vehicles as well as emergency generating sets, air conditioning and refrigeration. The engine’s behaviour is described with a mathematical modal and the mechanical, thermodynamics and for the chemical modals for the technical processes in the engine. To understanding of thermodynamics and of chemical reactions, kinetics is an essential requirement for the modelling of engine processes.

Why do we use the engines?

The engine converts heat energy to mechanical output.

Following diagram describes that the primary energies can be converted to secondary energies by using an engine,

engine diagram

Engine Types

  1. Heat engines
  2. Non-thermal chemically powered motors
  3. Electric motors
  4. Physically powered motors

1) Heat engines

The engine that converts thermal energy to mechanical work output is called as a Heat engine. Heat engines are classified into two main types as,

  1. Combustion engines
  2. Non combustion engines

1. Combustion engines

The engines driven by the heat of in a high temperature chemical reaction between a fuel and an atmospheric oxygen(combustion) process are called as combustion engines and they are classified as,     

·         Internal combustion engines (IC engines)
·         External combustion engines (EC engines)
·         Air breathing combustion engines
The representation of extremal and internal combustion
The representation of extremal and internal combustion
An air breathing rocket engine

Both, IC and EC engines can be divided as,

  • Reciprocating engines
  • Rotary engines

2. Non-combusting engines

There are some engines which convert heat in to mechanical work output by non-combustive process. These are called non combusting engines.

e.g.: – steam engines in nuclear power plants, some rocket engines 

Summery on Heat engines

2) Non-thermal chemically powered motors

These are usually powered by chemical reactions.

e.g.: – Molecule motor, synthetic motor

3) Electric motors

Electric motors are can convert electrical energy in to mechanical work output by the interaction of magnetic fields and current carrying conductions.

4) Physically powered motors

The motors powered by potential or kinetic energy they are called physically powered motors.

These are types of physically powered motors,

  • Pneumatic motors
  • Hydraulic motors

What is the most commonly used engine?

Heat engines are the most commonly used engines late 19th century,

Internal combustion engines are the most common heat engine type.

The following diagrams show some common parts of internal combustion engines.

Automobile engines can be divided by using criteria of the configuration of the cylinder piston system. Those are as follows,

  • In-line engine                   
  • V-engine                          
  • Radial engine                   
  • Flat engine
  • Dual-piston engine
  • Opposed piston engine

Manufacturing of engines

The engine body is made by casting. Other parts of an engine are made by forging,

Casting: pouring molten iron in to a mold that is made by sand

Forging: a lump of iron is heated red hot and then formed in to parts by using stumping machine.

What are the materials used to manufacture the engines?

  • Cast iron
  • Alloyed and structural steel
  • Aluminum alloys
  • Aluminum
  • Nickel
  • Copper alloys
  • Magnesium alloys
  • Titanium and its alloys
  • Cobalt base alloys


Engine is a heart of an automobile or any other type of vehicles. The above details give a brief explanation and a little image about the engines. 

To be continued with the articles about the following topics under the Engines,

  • Combustion engines
  • Air-breathing combustion engines
  • Non-combusting engines
  • Electric engines


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