Internal Combustion Engines: Introduction and Classification

The internal combustion engine is an engine 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.

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

1. Application

• Automobile Engine
• Aircraft Engine
• Locomotive Engine
• Marine Engine
• Stationary Engine

2. Basic Engine design

• Reciprocating: Single cylinder, Multi-cylinder In-line, V, radial, opposed cylinder, Opposed Piston.
• Rotatory: Single motor, Multi motor

3. 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. Working cycle

• Four stroke cycle
• Two stroke cycle
• Scavenging ; direct/crankcase/cross flow; back flow/loop; Uni flow
• Naturally Aspirated or Turbocharged

5. 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.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. Mixture preparation

• Carburetion
• Fuel injection

8. Ignition

• Spark ignition
• Compression Ignition

9. Stratification of charge

• Homogeneous Charge
• Stratified charge
• With carburetion
• With fuel injection

10. 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. Cooling

• Direct air-cooling
• Indirect air-cooling
• Low heat rejection engine