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Introduction to Internal Combustion Engine

What is Internal Combustion Engine?

Internal Combustion engine, or ICE, in simple words is a heat engine system in which the Combustion of fuel in presence of oxidiser occurs within the combustion chamber, inside the engine itself. Due to the combustion, the high-temperature and high-pressure gases expand, applying direct force to components of engines like piston, rotor, turbine etc. The conversion of chemical energy (combustion) into mechanical energy is most efficiently done by the use of an Internal Combustion Engine. The first ever internal combustion engine was invented by Étienne Lenoir in 1858. However, the first Modern Internal Combustion Engine wasn’t invented until 1876 by Nicolaus Otto. Since then, there’ve been hundreds if not thousands of improvements made on these engines and today almost every sector or field is heavily dependent on ICE.

Types of Internal Combustion Engine

The Internal Combustion engine is broadly of two types, Four-stroke engines and Two-stroke engines. Stroke is referred to as the full movement of the piston along the cylinder, in either direction. So the engines are classified by the number of strokes they take to complete one thermodynamic cycle.

Four- Stroke Engine

It is a type of IC engine that takes 4 strokes to complete one cycle. Each stroke rotates the crankshaft by 180 degrees, which means during a cycle, the crankshaft completes two whole revolutions, i.e., 720 degrees. Invented in 1862 by Carl Eugen Langen and Nicolaus Otto, this was the first type of Internal Combustion engine. The major components of a Four-stroke engine are as follows –

  • Piston
  • Crankshaft
  • Camshaft
  • Spark plug
  • Cylinder
  • Valves
  • Carburetor
  • Flywheel
  • Connecting rod
  • Fuel injectors
 4 Stroke Internal Combustion Engine
4 Stroke Engine

The engine completes a total of Four strokes during one complete cycle. Therefore, in order to understand it’s working mechanism, we can take a look at the different strokes and see what happens during those strokes.

  • INTAKE– Intake, or suction stroke is the first stroke of the cycle, in which the piston moves from Top Dead Center (T.D.C.)  to the Bottom Dead Center (B.D.C.) while the intake valve is open. This creates a vacuum in the cylinder, causing the air/fuel mixture to fill up the cylinder.
  • COMPRESSION– In this stroke, the piston moves from B.D.C. to T.D.C., while both the intake and exhaust valves are closed, which leads to the air/fuel mixture to get compressed and all ready for the power stroke.
  • POWER– Also known as ignition or combustion stroke, in this stroke, the compressed air/fuel mixture is ignited by the spark plug. Due to this, the piston is moved from T.D.C. to B.D.C. This produces mechanical energy to rotate the crankshaft.
  • EXHAUST– This is the last stroke, during which the piston again returns from B.D.C. to T.D.C. while the exhaust valve is open, due to which the exhaust gases are ejected out of the cylinder. Hence the cycle is completed and the piston is back to its initial position to begin the next cycle.
Working of a 4 Stroke Internal Combustion Engine
Working of a 4 Stoke Engine

Two- Stroke Engine

As the name suggests, it is a type of IC engine that takes 2 full strokes for the thermodynamic cycle to complete. In each stroke the crankshaft is rotated by 180 degrees, hence the crankshaft makes one complete rotation by the end of the 2 strokes.  It was invented by German inventor Karl Benz in 1880 and was widely used during the world war due to its simple design and cheap maintenance. Its components include –

  • Fuel Injector
  • Cylinder
  • Cylinder Head
  • Crank
  • Crankshaft
  • Connecting rod
  • Ports
  • Piston
  • Piston Rings
2 Stroke  Internal Combustion Engine
2 Stroke Engine

Similarly, in order to understand the mechanism of a Two stroke engine, we need to look at the strokes individually and see what happens in the engine during the cycle.

  • COMPRESSION– Inlet port opens and the air/fuel mixture fills up the cylinder. The Piston moves upwards, from B.D.C to T.D.C., causing the mixture to get compressed. The spark plug then ignites the compressed mixture and power stroke begins.
  • POWER– The combustion of the mixture produces force, which moves the piston downwards, from T.D.C. to B.D.C. due to the expansion of gases. The exhaust gases are ejected by opening the exhaust port.
Working of a 2 Stroke Internal Combustion Engine
Working of a 2 Stroke Engine

Advantages and Disadvantages

Although both these types of IC engines are widely used throughout industries worldwide, they too come with their fair share of flaws and strengths.

A four- stroke engine has more efficiency when compared to a two-stroke engine, but the heavier weight is what puts it at a disadvantage. Also, because a four- stroke engine consumes fuel only during one single stroke, therefore it is more fuel efficient. The four-stroke engines are quieter and produce a higher torque at a lower RPM, whereas two-stroke engines create high torque at higher RPMs.

Also, a two-stroke engine produces more power. But due to them working at higher RPMs, they are always at a higher risk of wear and tear, therefore the point for durability goes to the Four-stroke engine. But on the other hand, due to their simpler design, it is way easier to repair and maintain two-stroke engines compared to four-stroke engines.
As for heavy marine vessels, two stroke engines with a uniflow type scavenging is ideal and is used globally for a multitude of reasons, prime of which are, high power output and easy maintenance over long run.
Hence it is always advised to understand the type of application one is going for, before deciding which type of Engine is going to best suit their requirements.

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