Internal Combustion Engines: Introduction and Classification

The internal combustion engines are the engines in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine the expansion of the high temperature and high pressure gases produced by combustion apply direct force to some component of the engine. The force is applied typically to pistons, turbine blades or a nozzle.

Principle of operation:

Air-fuel mixture in the combustion chamber is ignited, either by a spark plug (in case of SI Engines) or by compression (in case of CI engines). This ignition produces tremendous amount of heat energy and pressure inside the cylinder. This induces reciprocating motion in the piston.
Power of the piston is transmitted to a crankshaft which undergoes rotary motion. The rotary motion is ultimately transmitted to the wheels of the vehicle, via a transmission system, to produce propulsion in the vehicle.
As the combustion takes place internally inside the cylinder (a part of working fluid circuit) the engine is called internal combustion engine.
Internal combustion (IC) engine cutaway figure

Classification of Internal Combustion Engines:

Today’s IC engines can be classified in several ways. Some of the ways of classification of Internal Combustion (IC) engines is listed below:

1. Based on application
  • Automobile Engine
  • Aircraft Engine
  • Locomotive Engine
  • Marine Engine
  • Stationary Engine
2. Based on basic engine design
  • Reciprocating: Single cylinder, Multi-cylinder In-line, V, radial, opposed cylinder, Opposed Piston.
  • Rotatory: Single motor, Multi motor
3. Based on operating cycle
  • Atkinson (For complete expansion SI Engine)
  • Diesel (For the Ideal Diesel Engine)
  • Dual (For the Actual Diesel Engine)
  • Miller (For Early/Late Inlet valve closing type SI Engine)
  • Otto (For the Convectional SI Engine)
4. Based on working cycle
  • Four stroke cycle
  • Two stroke cycle
    • Scavenging ; direct/crankcase/cross flow; back flow/loop; Uni flow
    • Naturally aspirated or turbocharged
5. Based on Valve/port design and location
  • Design of valve/port
    • Poppet valve
    • Rotatory valve
  • Location of valve/port
    • T-head
    • L-head
    • F-head
    • L-head
6.Based on Fuel
  • Convectional
    • Crude oil derivatives; Petrol, diesel
    • Other sources; coal, bio-mass, tar stands, shale
  • Alternative
    • Petroleum derived: CNG, LPG
    • Bio-mass derived: alcohols, vegetable oils, producer gas, biogas and hydrogen
  • Blending
  • Bi-fuel and dual fuel
7. Based on mixture preparation
  • Carburetion
  • Fuel injection
8. Based on ignition
  • Spark ignition
  • Compression Ignition
9. Based on stratification of charge
  • Homogeneous Charge
  • Stratified charge
    • With carburetion
    • With fuel injection
10. Based on combustion chamber design
  • Open chamber: Disc, wedge, hemispherical, bowl-in-piston, bath tub.
  • Divided chamber:
    • (For CI) 1. Swirl chamber, 2. Pre-chamber
    • (for SI) 1. CVCC, 2. Other designs
11. Based on cooling system

Vinodh Reddy is an Editor-in-chief of ME Mechanical. He holds Bachelor of Engineering (Honours) degree in Mechanical Engineering from BITS-Pilani. He also writes for vrcworks.net and EduGeneral.

All Comments

  • thanks for your post 🙂

    Tahmid Khan Mar 23, 2014 1:07 am Reply
  • Sir , given the max power of an engine at an rpm ….and max torque at an rpm…and i have an engine that is of a bike and needed to be fit to a car ..can we figure out the torque-rpm or rpm-power diagram of my engine, out of this given data?

    dileep Dec 13, 2015 12:28 pm Reply
  • Sir,
    I have a doubt regarding SI engine and CI engine, If we look into the SI engine it is more efficient on 60km/hr something at high speed but case of CI engine it will be at low speed why its happening……??

    Kiran Feb 12, 2016 4:57 pm Reply
  • Thanks so much for your time in writing this blog post.

    Kerry Finlay Jun 10, 2016 5:58 pm Reply

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