Internal Combustion Engine, the short and most popular name is IC Engine. It is one of the types of engines, fuel burns, and creates pressure to a piston inside the cylinder. Fuel burns or combusts inside of the cylinder, that’s the reason it is knowns as Internal Combustion Engine. IC engine is the most important topic for Mechanical Engineering and Automobile stream. Almost everyone has an idea about the IC engine. Nowadays IC engines are the most wide power-generating engine. The type of generated power may be mechanical power or electrical power.

Before we read about IC engines, we will also know about Heat Engines. Because the IC engine is a type of Heat Engine. 

What is a Heat Engine? 

An Engine is a machine that can converts one form of energy into another form in the desired manner. And A Heat Engine is a machine that transforms the chemical energy into thermal energy, and this thermal energy produces mechanical energy. Here chemical energy, obtained from burning the fuel. Where fuel is like wood, coal, petroleum fuel, etc. Heat engines are classified into two major types:

  1. External Combustion Engine 
  2. Internal Combustion Engine

Do you know about the Steam Engine? Yes, the steam engine was invented by James Watt. The steam engine is a perfect example of an external combustion engine. In an external engine, the mixture of fuel and air combust outside and transfers heat to the second fluid. This fluid is the working fluid for the cycle. The steam of the working fluid pushes the piston. Stirling engine is also an external combustion engine.

What is an IC Engine?

Internal combustion engine, in this type of heat engine the fuel and air mixture ignite and directly, pushes the piston. Diesel and Petrol engines are the best examples of the internal combustion engine. Wankel cycle, gas engine, rocket and, jet engines are also examples of internal combustion engines.

IC engines are compact and lighter as compared to external combustion engines. That is the main reason these engines are widely used in automobiles and transport vehicles like cars, buses, locomotives, aircraft, etc. 

The earliest IC engine was Huygens Gunpowder Engine. Was invented in 1680 by famous Dutch physicist Christian Huygens. 

IC Engine: Huygens Gunpowder Engine
Huygens Gunpowder Engine

IC Engine parts:

Let’s check are basic parts of a single-cylinder spark-ignition engine (SI engine). In the below image you can see a sketch layout of a single-cylinder engine. Cylinder block holds the cylinder. And cylinder head covers at the top end. In the cylinder, a piston moves upward to downward and vice-versa. This motion is reciprocating motion. The space enclosed between the upper part of the cylinder and the top of the piston during the combustion process is known as the combustion chamber

The mixture of air and fuel enters the combustion chamber through the inlet port. This charge (air and fuel mixture), before entering the inlet port, comes from carburetor to inlet manifold. The inlet manifold is a connector between air intake and inlet port.

What is the function of the carburetor, Do you know?

The Carburetor is mixing, regulator, and controller device. Means, carburetor makes a mixture of fuel (gasoline) and air. The carburetor regulates the air and fuel ratio. And also controls the engine’s speed by regulating air-fuel mixture with the help of throttle. 

Inlet valve in the cylinder head charges the air-fuel mixture in the combustion chamber and the exhaust valve discharges the combusted product after combustion.

For starting the combustion, the air-fuel mixture requires a spark. A spark plug provides this spark to initiate combustion.

After the combustion process, gases expand and creates a force on the piston. This force displaces the piston downward. A couple of rings i.e, piston rings prevent gas leakage during expands the gas. And a gudgeon pin provides smooth swivel motion between piston and crank rod.

Piston’s downward movement rotates the crankshaft with the help of a crank rod. The crank rod or connecting rod helps to convert reciprocating motion into rotational motion. And crankshaft is a translator, which translates the reciprocating motion into rotational motion. The crankshaft is enclosed in a crankcase. It is the main engine body. Inside the crankcase, the crankshaft is supported by bearings.

From which part of the engine operates the valves? Did you think that?

Now, let’s go back to the combustion process. Here, the charge intakes through the inlet valve and the combusted product discharges from exhaust valves. Both, the intake and exhaust valves are operated by the valve mechanism. The Crankshaft also drives the camshaft with the help of timing gears. This camshaft transform motion to the pushrod and rocker arm for opening the valves. The valve springs develop force against the rocker arm force and this closes the valves again.

Engine parts are made from what kind of materials?

Did you think what is material used to make piston? Let’s we will take a short time to know that material. Not only for piston, but we will discuss in a brief about materials of other engine parts also.

IC Engine Basic Parts
IC Engine Basic Parts

Engine Part Name


Manufacturing Method

1. Cylinder head Aluminum alloy, Cast Iron Casting, forming
2. Cylinder Cast Iron Casting
3. Piston Aluminum alloy, Cast Iron Casting, forging
4. Piston rings Silicon Cast Iron Casting
5. Gudgeon (Piston) pin Steel Forging
6. Valve Alloy Steel Forging
7. Connecting rod Steel Forging
8. Cylinder liner Nickel-based alloy, Steel, Cast Iron Casting
9. Bearings Bronze alloy, White metal Casting
10. Crankshaft Alloy steel, Ductile (Nodular) cast iron Forging
11. Crankcase Aluminum alloy, cast iron, alloy steel Forging
12. Rocker arm Cast iron, carbon steel, aluminum alloy Forging, casting

 Terminology in IC Engine:

The following terms are used in IC engine.

  1. Stroke (L) – The distance traveled by a working piston in a cycle.
  2. Piston Area (A) – The cross-sectional area of the piston.
  3. Cylinder Bore (D) – The nominal inner diameter of the cylinder.
  4. Dead Center – The position of the piston during working either at the topmost point or bottommost point of the cylinder. In an engine, there are two dead centers i.e; Top dead and Bottom dead center.
    1. Top dead center (TDC) – The furthermost or topmost position of the piston with respect to the crankshaft is the top dead center. TDC is known as inner dead center (IDC) in the case of horizontal engines.
    2. Bottom dead center (BDC) – The bottommost or nearest position of the piston with respect to the crankshaft. TDC is known as outer dead center (ODC) in the case of horizontal engines.
  5. Displacement Volume (Vs) – The volume generated by the piston when traveling between one dead center to another dead center. It is the product of the piston area and stroke. Another name of displacement volume is swept volume. 
                                                                                      Vs = A x L
  6. Clearance Volume (Vc) – While piston goes on TDC, the volume of the combustion chamber is clearance volume.
  7. Cylinder Volume (V) – The total of displacement volume and clearance volume. 
                                                                                     V =  Vs + Vc
  8. Compression ratio (r) – The compression ratio is the ratio of the cylinder volume and clearance volume. 
                                                                                      r = V / Vc

In this article, we have read about the Heat engine and IC engine, The general parts, and the terminology of the engine. In the next article, we will also discuss the base of classification and types of IC engines. Till stay continues with us.

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