IC Engine.

Internal combustion engine (IC engine) is the heart and soul of countless machines that power our modern world. IC engines have revolutionised transportation and provided unprecedented mobility, from cars and motorcycles to ships and airplanes. Combustion reaction within these engines involves a complex interplay of fuel, air, and ignition, releasing energy that propels vehicles forward.

In this article, readers shall be apprised of the Internal Combustion Engine and its working principle.

What is an Internal Combustion Engine?

An internal combustion engine (IC engine) is a type of heat engine that converts the chemical energy stored in fuel into mechanical energy. It is commonly used in vehicles, power generators, and various industrial applications. Fuel and air are mixed, combusted, and burned in an IC engine within a combustion chamber. The resulting high-pressure gases exert force on a piston, which translates the pressure into rotational motion through a crankshaft. This mechanical energy is then used to power the vehicle or operate machinery. IC engines come in different variations, such as gasoline engines and diesel engines, each with its own combustion process and characteristics.

Components of IC Engine

Fig: Components of IC Engine

The main Components of IC Engine are:

Exhaust camshaft

Exhaust valve bucket

Spark plug

Intake valve bucket

Intake camshaft

Exhaust valve

Intake valve

Cylinder head

Piston

Piston pin

Connecting rod

Engine block

Crankshaft

These are explained below:

Exhaust camshaft: A rotating shaft that controls the opening and closing of the exhaust valves.

Exhaust valve bucket: A component that sits on top of the valve stem and transfers the motion from the camshaft to open and close the exhaust valve.

Spark plug: A device that ignites the air-fuel mixture in the combustion chamber to initiate the combustion process.

Intake valve bucket: Similar to the exhaust valve bucket, it transfers the motion from the camshaft to open and close the intake valve.

Intake camshaft: A rotating shaft that controls the opening and closing of the intake valves.

Exhaust valve: A valve that opens to allow the exhaust gases to exit the combustion chamber during the exhaust stroke.

Intake valve: A valve that opens to allow the fresh air-fuel mixture to enter the combustion chamber during the intake stroke.

Cylinder head: The topmost part of the engine that houses the combustion chambers, valves, and spark plugs.

Piston: A cylindrical component that moves up and down inside the cylinder, driven by the force generated by the combustion process.

Piston pin: Also known as a wrist pin, it connects the piston to the connecting rod, allowing the piston to pivot.

Connecting rod: Connects the piston to the crankshaft and transfers the linear motion of the piston into rotational motion.

Engine block: The main housing of the engine that contains the cylinders and provides support for various engine components.

Crankshaft: Converts the reciprocating motion of the pistons into rotational motion, which drives the transmission and, ultimately, the wheels.

Working Principle of IC Engine

A schematic description of the working principle of IC Engine is given below:

Intake Stroke 

At the start of the intake stroke, the piston is near the top dead center (TDC). The intake valve opens, initiating the piston's downward movement towards the bottom dead center (BDC). During this stroke, the cylinder draws in fresh air or an air-fuel mixture. This phase is known as the intake stroke, as it involves the intake of new air/mixture into the engine. The intake stroke concludes when the piston reaches the BDC. Throughout the intake stroke, the engine expends energy as the crankshaft rotates due to the inertia of its components.

Compression Stroke

The compression stroke commences after the completion of the intake stroke, with the piston positioned at the Bottom Dead Center (BDC). During this stroke, both the intake and exhaust valves remain closed as the piston moves towards the Top Dead Center (TDC). As the air or mixture becomes compressed, the pressure within the cylinder increases, reaching its maximum when the piston nears the TDC. Just before the piston reaches the TDC (in close proximity), specific actions occur depending on the engine type:

For gasoline engines, a spark is generated to initiate the combustion process.

For diesel engines, fuel is injected into the highly compressed air to trigger combustion.

Power Stroke

The power stroke commences with the piston positioned at the Top Dead Center (TDC). During this stroke, both the intake and exhaust valves remain closed. At the end of the compression stroke, combustion of the air-fuel mixture begins, resulting in a substantial rise in cylinder pressure. This increased pressure forcefully drives the piston downward towards the Bottom Dead Center (BDC). During the power stroke, the engine generates energy, converting the force exerted by the pressure into mechanical work.

Exhaust Stroke

The exhaust stroke commences as the piston reaches the Bottom Dead Center (BDC), following the completion of the power stroke. Throughout this stroke, the exhaust valve opens, allowing the movement of the piston from BDC to Top Dead Center (TDC). This piston motion effectively expels the majority of the exhaust gases from the cylinder, directing them into the exhaust pipes. Similar to the previous strokes, the engine expends energy during the exhaust stroke as the crankshaft rotates due to the inertia of its components.