How Does an Internal Combustion Engine Work?

What is an internal combustion engine?

An internal combustion engine (ICE or IC engine) is a heat 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 exerts a direct force on some components of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle.

This force moves the component over a distance, converts chemical energy into usable kinetic energy, and is used to drive, move, or propel whatever the motor is attached to. This replaces the external combustion engine for applications where the weight or size of the engine is important.

The term internal combustion engine usually refers to an engine in which combustion is intermittent, such as the more popular four-stroke and two-stroke piston engines, along with variants such as the six-stroke piston engine and the rotary Wankel engine.

The second class of internal combustion engines uses continuous combustion: gas turbines, jet engines, and most rocket engines, each of which is an internal combustion engine on the same principle as previously described. Firearms are also a form of an internal combustion engine, although they are so specialized that they are usually treated as a separate category.

In contrast, in external combustion engines, such as steam or Stirling engines, energy is given off to a working fluid that does not consist of combustion products, is mixed with them, or is contaminated by them. Working fluids for external combustion engines include air, hot water, pressurized water, or even liquid sodium that is heated in a boiler.

Read More: What is External Combustion Engine?

ICEs are usually powered by energy-dense fuels such as gasoline or diesel fuel, fluids made from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for vehicles such as cars, aircraft, and boats.

 An internal combustion engine (ICE) is a heat 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.

How does an internal combustion engine work?

In an internal combustion engine (ICE), the ignition and combustion of the fuel occur within the engine itself. Combustion, also known as burning, is the basic chemical process for releasing energy from a fuel-air mixture. The engine then converts some of the energy from the combustion into work.

The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion. The expansion of the combustion gases pushes the piston during the power stroke.

Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels.

Two types of internal combustion engines are currently in production: the spark ignition gasoline engine and the compression ignition diesel engine. Most of them are four-stroke, which means it takes four piston strokes to complete a cycle. The cycle comprises four different processes: intake, compression, combustion and power stroke, and exhaust.

Spark ignition gasoline and compression ignition diesel engines differ in the way they deliver and ignite fuel. In a spark-ignition engine, the fuel is mixed with air and then sucked into the cylinder during the intake process. After the piston compresses the fuel-air mixture, the spark ignites it and causes combustion.

The expansion of the combustion gases pushes the piston during the power stroke. In a diesel engine, the air is just drawn into the engine and then compressed. Diesel engines then spray the fuel in a suitable, metered amount into the hot compressed air, which ignites it. 

Applications of internal combustion engines

Internal combustion engines are the most broadly applied and widely used power-generating devices currently in existence. Examples include gasoline engines, diesel engines, gas-turbine engines, and rocket-propulsion systems.

IC engine has many applications like,

  • Gasoline Engines: Automotive, Marine, Aircraft
  • Gas Engines: Industrial Power
  • Diesel Engines: Automotive, Railways, Power, Marine
  • Gas Turbines: Power, Aircraft, Industrial, Marine

Different Types Of Internal Combustion Engine

There are two kinds of internal combustion engines currently in production: the spark ignition gasoline engine and the compression ignition diesel engine. Most of these are four-stroke cycle engines, meaning four piston strokes are needed to complete a cycle.

IC engines can be classified on the basis of fuel used, thermodynamic cycle, type of ignition, type of cooling system, cylinder arrangement, method of charging, etc.  Now we study it in detail.

1) According to Cycle of Operation:

We know IC engines convert chemical energy into mechanical energy in cyclic operation. There are many thermodynamic cycles e.g. Carnot cycle, Otto Cycle, Diesel Cycle, Rankine cycle, etc. IC engines work on three cycles Otto cycle, the Diesel cycle, and the Dual cycle. So according to it, the IC engines can be classified into the following types.

1. Otto Cycle Engine:

It is also known as a spark-ignition engine or constant volume heat addition engine, Petrol engine, etc. In this cycle heat addition (fuel burn) and rejection (exhaust) takes place at constant volume and expansion and compression take place at isentropic. These engines give low power at high speed.

2. Diesel Cycle Engine

This is known as a compression-ignition engine, diesel engine, constant pressure engine, etc. In this cycle heat addition (fuel burn) takes place at constant pressure and heat rejection takes place at constant volume. This engine gives high power at low speed.

3. Duel Cycle Engine:

The dual cycle is a combination of the Otto cycle and the diesel cycle. In this engine, heat addition takes place both at constant volume and constant pressure in some ratio.

Some engines work on the Stirling cycle and Ericsson cycle but these are not used commercially.

2) According to Type of Fuel Used:

Most of us know about these engines. These are petrol engines and diesel engines. Nowadays gaseous fuel like LPG, CNG, hydrogen, etc. is also used in IC engines. These engines are called non-traditional engines.

3) According to the Method of Charging:

The charging means how the admission of the fuel-air mixture takes place. This can be classified as follow.

1. Natural aspirated engine:

In this engine, admission of the air-fuel mixture (SI Engine) or air alone (CI engine) takes place due to pressure difference inside the cylinder and atmospheric pressure.

2. Supercharged Engines:

In this engine, a separate compressor is used to the admission of charge inside the cylinder. This compressor is run using engine power (connected with the crankshaft with belt drive).

3. Turbocharged Engine:

This engine uses a turbine that draws air into the cylinder and runs by using exhaust gas power. It is also like supercharge but the compressor is run by a turbine which is rotated by exhaust gases.

4) According to Ignition:

In IC engine ignition of charge can take place in two ways. In the first one, a separate spark plug or any other device is used to ignite the fuel (Spark Ignition Engine) and the other one is fuel ignite due to heat generated during compression or fuel (Compression Ignition Engine).

So according to these methods, two engines are available spark-ignition engine or SI engine (Petrol Engine) and a compression ignition engine or CI engine (Diesel Engine).

5) According to a type of Ignition System:

In petrol engines, we used a spark plug to ignite the fuel. This spark at the spark plug, produce by an ignition system. According to the ignition system, two types of engines are there. The first one is the battery ignition engine (use a battery to generate spark) and another one is a magneto ignition engine (use a small generator to generate spark).

6) According to Design of Engine:

1. Reciprocating Engine:

In this type of engine, a piston is used which moves in reciprocating motion by using pressure force generated by the burning of fuel. The crankshaft converts this reciprocating motion into rotary motion. Most of the automobile engines are reciprocating type.

Read More: What is Reciprocating Engine?

2. Rotary Engine:

In a rotary engine, a rotor is used. The pressure force generated by the burning of fuel is exerted on this rotor, which further rotates the wheel. The Wankel engine is one type of rotary engine. These engines are currently not used in automobile engines.

7) According to cooling:

Two types of cooling are used in IC engines, air cooling, and water cooling. So the engines are air-cooled engines or water-cooled engines. Both these cooling systems have their own advantages, which we will discuss later. Engine oil is also serving as a cooling medium.

8) According to stroke of engine:

We know that the stroke is the maximum distance a piston can travel inside a cylinder or between TDC to BDC. If an engine moves from TDC to BDC, it is called one stroke. If it returns to BDC it is called two strokes. A crankshaft makes one rotation in two strokes. According to it, three types of engines have been invented.

1. Two-stroke Engine:

In this engine, the crankshaft makes one rotation in one power stroke. This engine gives more power compared to others. It is used in shooters, ships, generators, etc.

Read More: What is Two-stroke Engine? and What is a Four-stroke Engine?

2. Four-stroke engines:

This engine gives two crankshaft rotations in one power stroke. They give low power but high efficiency. It is used in cars, trucks, bikes, etc.

3. Six stroke engines:

These engines are in the development process. As the name implies, it will give three crankshafts rotation in one power stroke.

9) According to an arrangement of engine:

arrangement of engine

These engines can be better understood by diagrams compared to words.


Who Invented The Internal Combustion Engine?

In 1823, Samuel Brown patented the first internal combustion engine to be applied industrially in the U.S.; one of his engines pumped water on the Croydon Canal from 1830 to 1836.

The first commercially successful internal combustion engine was created by Étienne Lenoir around 1860 and the first modern internal combustion engine was created in 1876 by Nicolaus Otto. In 1872, American George Brayton invented the first commercial liquid-fueled internal combustion engine.

What is the importance of an IC engine?

The development of the internal combustion engine helped to free men from the hardest manual labor, made possible the airplane and other forms of transportation, and helped to revolutionize power generation.

What is the difference between IC and SI engines?

Si engine is an internal combustion engine that operates on the principle of spark ignition. It uses petrol and utilizes the Otto cycle. The diesel (Ci) engine is also an internal combustion engine, which uses diesel fuel and operates on a diesel cycle.

Where are IC engines used?

Internal combustion engines (ICE) are the most common form of heat engines, as they are used in vehicles, boats, ships, airplanes, and trains. They are named as such because the fuel is ignited in order to do work inside the engine. The same fuel and air mixture is then emitted as exhaust.

What is the explosion ratio in an IC engine?

AFR is the mass ratio of air to fuel present in an internal combustion engine. For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air to one part of fuel. It depends on the type of fuel.

What is the temperature in IC engine?

The temperature of the burning gases in the engine cylinder reaches up to 1500 to 2000°C, which is above the melting point of the material of the cylinder body and head of the engine. (Platinum, a metal that has one of the highest melting points, melts at 1750 °C, iron at 1530°C, and aluminum at 657°C.)

What is the function of a piston in an IC engine?

The piston is a fundamental part of the internal combustion engines. It has a reciprocating motion and converts heat energy into mechanical power. It travels up and down inside a cylinder when the engine produces power. The purpose of the piston is to stand the expansion of gases and send it to the crankshaft.

What is an ICE vehicle?

ICE vehicle means a conventional vehicle powered solely by an Internal Combustion Engine.

Is IC or EC a more efficient engine?

The internal combustion engine has an efficiency of about 35-45 %. As compared to the external combustion engine has an efficiency of about 15-25 %. The Fuel cost of the internal combustion engine is relatively high. As compared to the fuel cost of the external combustion engine is relatively low.