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What is IC Engines? and Different Types of IC Engines (PDF)

In this article, you learn what is IC Engines its Parts, working principle, Types of Internal Combustion Engines. And difference between steam engine and IC engine.

And also download the PDF file of this article at end of it.

Internal Combustion Engines

As the name implies or suggests, the internal combustion engines (briefly written as I.C. Engine) are those engines in which the combustion of fuel takes place inside the engine cylinder.

In other words, the internal combustion engines are those engines in which the combustion of fuel takes place inside the engine cylinder by a spark. These are petrol, diesel and gas engines.

An engine is a device, which by using the chemical energy of the fuel, transforms it into thermal energy by combustion, to produce mechanical work. We have seen in steam engines that the fuel, fed into the cylinder. It is in the form of steam. Which is already heated and is ready for work in the combustion cycle of the engine.

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Parts of Internal Combustion Engine

The principal parts of an internal combustion engine are shown in the Figure.

  1. Cylinder
  2. Cylinder head
  3. Valves
  4. Piston
  5. Piston ring
  6. Connecting rod
  7. Crankshaft
  8. Crankcase
  9. Flywheel
Internal Combustion Engines

#1 Cylinder

In an internal combustion engine, the main part is the cylinder in which combustion takes place. The cylinder has to withstand high temperature and high pressure. Normally the cylinder is made of cast iron or steel alloy.

#2 Cylinder Head

This is a block placed as a cover on the cylinder. The cylinder head has provision for setting the inlet and exhaust valves. A hole is also provided to screw in a spark plug or injection nozzle.

The cylinder head is normally made of cast iron. When head is mounted on the cylinder, an asbestos gasket is provided in between the cylinder and the cylinder head.

#3 Valves

The valves are placed in the correct setting in the provision made especially for them in the cylinder head. Two valves are provided. Through the inlet valve the mixture of air and fuel vapour is sent in.

The exhaust valve is for discharging the products of combustion. The valves are held in position by valve springs. The opening and closing of these valves are performed with the help of cam mechanisms. They are made of Nickel Chromium Steel.

#4 Piston

The piston is the main active part of the engine as shown in Figure. It has a close fit with the cylinder. The movement of the piston changes the volume of the cylinder and provides the combustion space.

Generally, pistons are made up of aluminum alloy. Aluminum alloy is the lightest one and has good heat conductive properties. A hole is centrally provided to insert a pin to connect the small end of the connecting rod. Circumferential grooves are provided on the surface of the piston to accommodate piston rings.

#5 Piston Rings

Piston rings are made up of special steel alloys to retain elastic properties at high temperature. These are circular rings fitted in the circumferential grooves of the piston. There are two sets of rings.

Upper rings are called compression rings, which provide an airtight seal. This will prevent the leakage of burnt gases into the casing. The lower rings are called oil scrapper rings. These are provided to remove the oil film from the engine cylinder and to prevent the leakage of oil into the cylinder.

#6 Connecting rod

This is the connecting link between the piston and the crankshaft. The reciprocating motion of the piston is converted into rotary-motion of the crankshaft.

Upper end of the connecting rod is called small end, which carries the piston by means of a floating pin called piston pin or gudgeon pin. The lower end is called big end of the connecting rod, which connects the crankshaft through the crankpin. This is made of forged steel, alloy steel.

#7 Crankshaft

Crankshafts are made up’ of special steel alloys. The crankshaft is the main member from which we obtain the rotary power. This shaft is build up with one or more eccentric parts called crank or crank throws. This crank throws are mainly responsible for producing reciprocating motion of the piston.

#8 Crankcase

This is the main housing at the bottom of the engine, providing support for the cylinder and crankshaft bearings. The other engine parts are arranged in proper alignment on this crankcase. The crankcase provides protection to the parts from dirt and also it acts as a lubricant sump.

#9 Flywheel

Flywheel is a larger solid wheel mounted on the crankshaft. This acts as an energy reservoir to store excess energy during power stroke and delivers during the compression stroke. 

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Working Principle of Internal Combustion Engines

In IC engines (internal combustion engines) the combustion of takes place inside the cylinder, therefore, the thermal energy of the fuel is directly converted into mechanical work.

the IC engine has a higher thermal efficiency than the thermal efficiency of EC engines. In internal combustion engines, when the IC engine is working continuously, we may consider a cycle starting from any strokes.

We know that when the engine returns back to the stroke where it starts we say that one cycle has been completed. The IC engine has four steps to complete one cycle as follows:

Suction Stroke In this stroke the fuel vapour, in the correct proportion, is supplied to the engine cylinder.

Compression Stroke In this stroke, the fuel vapour is compressed in the engine cylinder.

Expansion Stroke In this stroke, the fuel vapour burn by the spark plug is provided on the top of the engine cylinder. when the fuel is burned suddenly raise the pressure, due to the expansion of the combustion products in the engine cylinder. The rise of the pressure pushes the piston with a high force and rotates the crankshaft. The crankshaft, in turn, drives the machine connected to it.

Exhaust Stroke In this stroke, the burnt gases are exhausted from the engine cylinder to make space available for the fresh fuel vapour.

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Types of Engines

  1. External combustion engines (EC)
  2. Internal combustion engines (IC)

External combustion engines – If the combustion of fuel place outside the engine cylinder, it is an external combustion engine. Ex: Steam turbine, Gas Turbine, Steam Turbine etc.

Internal combustion engines – If the combustion fuel takes place inside the engine cylinder, it is an internal combustion engine. Ex: Petrol engine, Diesel Engine.

Types of Internal Combustion Engines

Following is the list of type of IC Engines (Classified according to different method):

  1. Working Cycle Employed
    1. Two-stroke Engine
    2. Four-stroke Engine
  2. Fuel Used
    1. Petrol
    2. Diesel
    3. Gas Engine
  3. Nature of Thermodynamics Cycle Used
    1. Otto Cycle
    2. Diesel Cycle
    3. Dual Cycle
  4. Methods Of Cooling
    1. Air Cooling
    2. Water Cooling
  5. Speed Of The Engine
    1. High-speed Engine
    2. Medium-speed Engine
    3. Low-speed Engine
  6. Field Of Application
    1. Stationary Engine
    2. Automobile Engine
    3. Portable Engine
    4. Aero Engine
  7. Method Of Ignition
    1. Spark-ignition Engine
    2. Compression-Ignition Engine
  8. Arrangement Of The Engine Cylinder
    1. Horizontal Engine
    2. Verticle Engine
    3. Radial Engine
    4. V-type Engine

Working Principle of Four Stroke Engine

In the IC Engine, the reciprocating motion of the piston inside the cylinder is converted into rotary motion of the crankshaft.

The piston downward motion is caused by the expansion of burnt gases during the combustion of the fuel in the engine cylinder. When the engine is running four events occur cyclically. They are suction, compression, power (expansion) and exhaust.

Working of a Four Stroke Petrol Engine

The petrol engine works on the principal of otto cycle also known as constant volume cycle. The spark plug fitted at the top of the cover initiates the ignition of the petrol. In four stroke engine, all the events, i.e. suction, compression, power and exhaust are completed in two revolutions of crankshaft. They are as follows.

Suction stroke

The stroke begins when the piston is at Top Dead Centre (TDC). The piston moves downward. The inlet valve opens. A mixture of petrol and air vapours, mixed proportionately by the carburetor enters the cylinder and fills the space in the cylinder. The piston reaches its lowest position known as Bottom Dead Centre (BDC).

Compression stroke

The piston moves up after the intake stroke. The inlet valve closes when the piston moves upward. The exhaust valve also remains closed. The piston compresses the fuel-air mixture by pushing it upward into clearance space at the top of the cylinder. The pressure and temperature of the mixture increased during compression.

Power stroke

The fuel-air mixture at high pressure and temperature is ignited by a spark. The spark ignites the fuel-air mixture. This burning increases the pressure and temperature of the gases further. The gases expand producing an explosive force pushing the piston down.

Piston moves down at high acceleration. The piston is connected to the connecting rod. The connecting rod is attached to the crankshaft. The linear movement of the piston is converted into the rotary motion of the crankshaft.

Exhaust stroke

Piston reaches the bottom centre at the end of the power stroke. The exhaust valve open, the bunt gases escape at greater speed. The piston moves up from bottom center and push out the remaining burnt gases inside the cylinder. At the end of the exhaust stroke, the exhaust valve closes. The cycle is repeated. For every 4-stroke of the piston, the crankshaft rotates revolutions.

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Working of a Four-Stroke Diesel Engine

The basic construction of a four stroke diesel engine is same as that of four stroke petrol engine, except instead of spark plug, a fuel injector is mounted in its place in fig. A fuel pump supplies the fuel oil to the injector at higher pressure. It works on diesel cycle or constant pressure cycle.

Suction stroke

Suction stroke is the first stroke. Piston moves down. The inlet valve is open allows air to enter the cylinder and fills the space. Piston reaches the bottom center and again starts moving up.

Compression stroke

The piston start moving up the inlet valve is closed. Air is compressed. The pressure and temperature of the air increase due to compression. Just before the piston reaching top dead, diesel fuel is sprayed inside the cylinder.

Fuel is sprayed by means of a fuci injector. The fuel is sprayed at a very high pressure overcoming the pressure of the compressed air and it gets mixed up with air. The air contains Oxygen. Since the fuel is a hydrocarbon the temperature of compressed air is sufficient to initiate the combustion. The fuel is burnt.

Power stroke

The piston moves from top dead centre to bottom dead center. The heat released by combustion increases the pressure and temperature of the air further. The maximum pressure and temperature of the burnt gases act on the top of the piston and forces the piston to move last, accelerates the piston downwards. This is the power stroke. Just before the piston reaches the bottom dead centre exhaust valve opens.

Exhaust stroke

The piston reaches the bottom dead centre and starts moving up. The burnt gases are being pushed out by the piston. The gases escape through exhaust valve. Before the piston reaches top dead centre the inlet valve is opened. The cycle is repeated.

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Working Principle of Two Stroke Engine

Working of a two stroke Petrol Engine

The two stroke engine requires one revolution of crankshaft or two strokes of the piston to complete the cycle of events (i.e, suction, compression, power and exhaust).

Two stroke petrol engine also work on the principle of working of the otto cycle. Figure 4.4 shows the construction and the working of a two stroke petrol engine.

First stroke

Assume that the piston is at its B.D.C position. During this stroke, the piston moves upwards from bottom dead centre to top dead centre. It closes the transfer port and the exhaust port.

The charged air-petrol mixture which is already there in the cylinder is compressed. Due to upward movement of the piston, a partial vacuum is created in the crank case and a fresh charge is drawn in to the crank case through the uncovered inlet port. At the end of this stroke, the piston reaches the T.D.C position.

Second stroke

The compressed charge is ignited in the combustion chamber by means of an electric spark produced by the spark plug, slightly before the completion of the compression stroke. Due to combustion piston is moved downward direction.

During this stroke, the inlet part is covered by the piston and the fresh charge is compressed in the crank case. Further downward movement of the piston uncovers the exhaust port and then the transfer port.

The expanded gases start escaping through the exhaust port and at the same time fresh charge which already compressed in the crank case is forced in to the cylinder through the transfer port.

The charge strikes the deflector, on the piston crown, rises to the top of the cylinder and pushes out most of exhaust gases. The piston is now at the bottom dead center position. The cylinder is completely filled with the charge. The cycle of events is then repeated.

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Two Stroke Cycle Diesel Engine

The Two stroke Diesel engine works as that of the Petrol engine but it injects diesel at end of compression stroke. The working principle is given below:

First Stroke

As the piston moves down on the power stroke, it first uncovers the exhaust port, and the cylinder pressure drops to atmospheric pressure as the products of combustion come out from the cylinder.

Further downward movement of the piston uncovers the transfer port and slightly compressed air enters the engine cylinder from the crankcase. Due to deflector on the top of the piston, the air will move up to the top of the cylinder and expels out the remaining exhaust gases through the Exhaust port.

Second Stroke

During the upward movement of the piston, first the Transfer port and then the exhaust port closes. As soon as the exhaust port closes the compression of the air starts. As the piston moves up, the pressure in the crankcase decreases so that the fresh air is drawn into the crank case through the open inlet port.

Just before the end of the compression stroke the fuel is forced under pressure in the form of fine spray into the engine cylinder through the nozzle into this hot air at this moment, the temperature of the compressed air is high enough to ignite the fuel.

It suddenly increases the pressure and temperature or the products of combustion. The rate of fuel injection is such as to maintain the gas pressure constant during the combustion period. Due to increased pressure the piston is pushes down with a great force.

Then the hot products of combustion expand. During expansion some of the heat energy produced is transformed into mechanical work. When the piston is near the bottom of the stroke it uncovers exhaust port which permits the gases to flow out of the cylinder. This completes the cycle and the engine cylinder is ready to suck the air once again.

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Difference Between Steam Engines and Internal Combustion Engines

Following are the difference between steam engine and internal combustion engine:

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Difference Between Petrol Engine and Diesel Engine

The main difference between a petrol engine and a diesel engine is a petrol engine draws a mixture of petrol and air during the suction stroke. And a diesel engine draws only air during the suction stroke.

The petrol engine works on the Otto cycle. It is easy to start, lighter and cheaper, It has a high running cost and low maintenance cost.

The diesel engine works on the diesel cycle. It difficult to start, heavier and costlier, It has low running cost and high maintenance cost.

The petrol engines thermal efficiency is about 26%. These are high-speed engines and used in light-duty vehicles. Where diesel engines thermal efficiency is about 40%. These are low-speed engines and used in heavy-duty vehicles.

Applications of IC Engines

Following are the application of ic engine:

  1. IC engines are used in Road vehicles like scooters, motorcycles, buses etc.
  2. It is also used in Aircraft.
  3. IC engine is commonly used in Motorboats.
  4. IC engine has great application in small machines, such as lawnmowers, chainsaws, and portable engine-generators.

So now, we hope that we have clear all your doubts about Internal Combustion Engine. If you have still any doubts about the “Types of IC Engines” you can ask in the comments.

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About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

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