Types of Heat Engines [Internal & External Combustion] | Comparison

By | December 5, 2021

What is a Heat Engine?

Before moving on to the heat engines (Classification of Heat Engines), let us first understand what is an engine.

An Engine is a device which converts one form of energy into another form.

Engines can further be divided into two types i.e. combustion engines and non-combustion engines. Examples of non-combustion engines are wind turbine and water turbine. Example of combustion engine is heat engine.

Now we will move on to the definition of heat engines.

A heat engine is a device converts chemical energy of fuel into thermal energy and utilize this thermal energy to perform useful work.

Types of Heat Engines

Heat Engines can be broadly classified into Internal and External Combustion Engines.

Internal Combustion Engines are the Engines in which fuel is burned inside the cylinder. Chemical energy of fuel gets converted into thermal energy which ultimately gets converted to mechanical energy.

External Combustion Engines are the Engines in which fuel is burned outside the cylinder and with the help of working fluid, brought to cylinder. Chemical energy of fuel gets converted into thermal energy which ultimately gets converted to mechanical energy.

Both the types of Heat Engines can be divided into Rotary and Reciprocating each. In Rotary Engines work is obtained from the heat with the help of Rotary devices (e.g. Turbines). In reciprocating Engines heat is converted to the work with the help of reciprocating mechanism (e.g. piston and cylinder).

Below are some abbreviation

IC – Internal Combustion

EC – External Combustion

Heat Engines

  1. IC Engines

(i) Rotary

  • Open Cycle Gas Turbine
  • Wankel Engine

(ii) Reciprocating

  • Gasoline Engine
  • Diesel Engine
  1. EC Engine

(i) Reciprocating

  • Steam Engine
  • Stirling Engine

(ii) Rotary

  • Steam Turbine
  • Closed Cycle Gas Turbine

Comparison between internal and external combustion engines

Internal Combustion Engines External Combustion Engines
Initial Cost is low Initial cost is high
Can’t be operated by solid fuels Can be operated by solid fuels
They require less space They require more space

Featured image source: By Jeff Dahl, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=3235265

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