What is IC Engine? and It’s type

An internal combustion engine (I.C. engine) is an engine in which the ignition and combustion of fuel take place inside the engine cylinder. It works on the principle that a fuel–air charge is ignited inside a combustion chamber at high pressure, and the energy released during combustion is converted into mechanical work.

Basics of I.C. Engine

In primitive times, human muscle power was the primary source of energy. Later, animals were domesticated and used for performing work. With technological development, humans learned to convert energy from one form to another using machines called engines.

An engine is a mechanical device that converts heat energy into mechanical energy. Engines that operate on this principle are known as heat engines.

Broadly, heat engines are classified into:

• External Combustion (E.C.) Engines

• Internal Combustion (I.C.) Engines

Both E.C. and I.C. engines can further be classified as:

• Reciprocating engines

• Rotary engines

An I.C. engine is one in which combustion occurs inside the engine cylinder itself, unlike an E.C. engine where combustion occurs externally (e.g., steam engines).

A diesel engine is a common example of an I.C. engine, where air acts as the working fluid. I.C. engines are widely used in:

• Automobiles

• Aviation

• Power generation

• Agricultural and industrial applications

Main Components of an I.C. Engine

• Cylinder

• Piston

• Piston rings

• Connecting rod

• Crankshaft

• Valves

• Spark plug (SI engine)

• Fuel injector (CI engine)

• Oil sump

Major Classification of I.C. Engines

1. Based on Type of Ignition

(a) Spark Ignition (SI) Engine

In SI engines, a pre-mixed charge of air and fuel is drawn into the cylinder during the intake stroke. The mixture is compressed and ignited by a spark plug.

Example: Petrol (gasoline) engine

(b) Compression Ignition (CI) Engine

In CI engines, only air is drawn into the cylinder and compressed to a high pressure and temperature. Fuel is then injected into the hot compressed air, causing self-ignition.

Example: Diesel engine

2. Based on Number of Strokes per Cycle

(a) Four-Stroke Engine

A four-stroke engine completes one cycle in four piston strokes:

1. Intake

2. Compression

3. Power

4. Exhaust

It requires two crankshaft revolutions (720°) per cycle and is the most widely used engine in automobiles.

(b) Two-Stroke Engine

A two-stroke engine completes one cycle in two piston strokes:

• Compression

• Power

Only one crankshaft revolution (360°) is required.

(c) Six-Stroke Engine

This is an advanced concept engine designed to improve fuel efficiency and reduce emissions. It combines features of both two-stroke and four-stroke engines, resulting in six strokes per cycle.

3. Based on Thermodynamic Cycle

(a) Otto Cycle Engine

The Otto cycle is an ideal cycle for spark ignition engines. It consists of:

• Two isentropic processes

• Two constant-volume (isochoric) processes

(b) Diesel Cycle Engine

The diesel cycle is the ideal cycle for CI engines, consisting of:

• Two isentropic processes

• One constant-pressure (isobaric) process

• One constant-volume process

(c) Dual Cycle Engine

The dual (or mixed) cycle is a combination of Otto and Diesel cycles, where heat addition occurs partly at constant volume and partly at constant pressure.

4. Based on Type of Fuel Used

(a) Petrol (Gasoline) Engine

Uses petrol as fuel, ignited by a spark plug.

(b) Diesel Engine

Uses diesel fuel and operates on compression ignition.

(c) Bi-Fuel Engine

Can operate on two different fuels, commonly natural gas and petrol, using a dual-fuel system.

5. Based on Method of Ignition

• Spark Ignition (SI) Engine – ignition by spark plug

• Compression Ignition (CI) Engine – self-ignition due to compression

CI engines operate at high compression ratios (up to 22:1).

6. Based on Number of Cylinders

(a) Single-Cylinder Engine

Uses only one cylinder. Simple, compact, and economical.

(b) Multi-Cylinder Engine

Uses multiple cylinders (commonly 2, 4, 6, or 8) to provide smooth and continuous power output.

7. Based on Cylinder Arrangement

• Horizontally Opposed (Boxer) Engine

• Vertical Engine

• V-Type Engine (60°–90° V angle)

• Radial Engine (star-shaped arrangement)

• Inline Engine

• X Engine (used historically in aircraft engines)

• Opposed Piston Engine (two pistons per cylinder)

• W Engine (multiple cylinder banks)

8. Based on Cooling System

(a) Air-Cooled Engine

Heat is dissipated through airflow over cooling fins.

(b) Water-Cooled Engine

Uses water or coolant circulated through water jackets to remove heat.

(c) Oil-Cooled Engine

Uses engine oil as a cooling medium, often combined with an oil cooler.

Modern Advancements in I.C. Engines

Modern I.C. engines incorporate:

• Advanced fuel injection systems

• Lightweight materials

• Improved combustion chamber design

• Emission control technologies

These advancements aim to achieve:

• Higher fuel efficiency

• Reduced emissions

• Lower vehicle weight

• Improved engine performance