In this article, you learn what is IC Engines? Its parts, working principle, and types of Internal Combustion Engines.
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, 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, is 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.
Parts of Internal Combustion Engine
The principal parts of an internal combustion engine are shown in the Figure.
- Cylinder
- Cylinder head
- Valves
- Piston
- Piston ring
- Connecting rod
- Crankshaft
- Crankcase
- Flywheel
#1. Cylinder.
In an internal combustion engine, the main part is the cylinder in which combustion takes place. The cylinder has to withstand high temperatures 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 the 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 vapor 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. 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 temperatures. 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 the rotary motion of the crankshaft.
The upper end of the connecting rod is called the small end, which carries the piston using a floating pin called a 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 built up with one or more eccentric parts called crank or crank throws. These crank throws are mainly responsible for producing the 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 protects the parts from dirt and also it acts as a lubricant sump.
#9. Flywheel.
A flywheel is a larger solid wheel mounted on the crankshaft. This acts as an energy reservoir to store excess energy during the power stroke and delivers it during the compression stroke.
Working Principle of Internal Combustion Engines
In IC engines (internal combustion engines) the combustion 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 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 vapor, in the correct proportion, is supplied to the engine cylinder.
Compression Stroke In this stroke, the fuel vapor is compressed in the engine cylinder.
Expansion Stroke In this stroke, the fuel vapor burned by the spark plug is provided on the top of the engine cylinder. when the fuel is burned suddenly raises 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 vapor.
Types of Engines
- External combustion engines (EC)
- Internal combustion engines (IC)
External combustion engines – If the combustion of fuel is placed 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.
Classification of IC Engines
IC engines are categorized according to the number of strokes, fuel type, and engine cylinder arrangement. The following list provides a few details about this classification of IC engines:
Based on the Number of Strokes
Two-stroke Engine
A two-stroke engine is an internal combustion engine that uses two piston strokes to complete a power cycle. It is less complicated than a four-stroke engine, but it uses less fuel.
Two-stroke engines are widely utilized in small power tools, scooters, and some motorcycles. Compared to four-stroke engines, they feature a simpler design and require just two piston strokes to complete a power cycle.
Four-stroke Engine
Four-stroke engines are internal combustion engines that complete four distinct phases in one complete cycle: intake, compression, power, and exhaust.
It’s commonly utilized in automobiles, motorbikes, and other vehicles. As compared to two-stroke engines, these engines have a more complicated design, which makes them more difficult to maintain.
Based on Fuel Type
Spark-ignition Engine
In a spark ignition engine, air and petrol are combined and injected into the cylinder during the intake process. After the piston compresses the fuel-air mixture, a spark ignites the mixture, starting the combustion process.
During the power stroke, the piston is pushed by the expansion of the combustion gasses that follow. These are frequently found in compact vehicles, motorcycles, and passenger cars.
Compression-ignition Engine
Diesel engines just pump air into the engine, which is afterward compressed. The heated compressed air is then carefully fed with fuel at a controlled rate, igniting it. Diesel engines are widely employed in vehicles, buses, and heavy machinery.
Based on Engine Configuration
Inline Engine
Inline engines have cylinders that are placed in a straight line. This arrangement is widely used in compact automobiles and motorcycles.
V Engine
The V engine, also referred to as the Vee engine, is a popular internal combustion engine layout. It is made up of two cylinder banks, usually with the same number of cylinders each, that are linked together by a common crankshaft.
It is primarily utilized in high-performance motorcycles like cruisers and sports bikes.
Flat Engine
A flat engine, also known as a horizontally opposed engine, has two banks of cylinders facing each other, arranged horizontally. This design is often used in airplanes and high-performance sports automobiles.
Radial Engine
Radial engines have cylinders arranged in a circular configuration around the crankshaft. This specific configuration is commonly found in aircraft.
IC Engine Performance Parameter
The following are common parameters that are considered in the performance of an IC engine.
#1. Indicated Power (IP).
Indicated Power (IP) is the total power created by fuel combustion within the combustion chamber.
#2. Brake Power (BP).
The power output that is available at the engine’s output shaft is referred to as brake power. It is defined as the amount of power capable of effectively overcoming resistance or counteracting braking forces.
#3. Frictional Power.
The amount of power required to overcome internal friction in an engine is known as its friction power. It is the difference between the brake power and the indicated power, and it accounts for any losses resulting from the indicated power.
#4. Mechanical Efficiency.
The braking power to indicated power ratio indicates the mechanical efficiency of an internal combustion engine.
#5. Indicated Mean Effective Pressure.
The pressure that is theoretically expected to be applied to the piston during an engine’s power stroke is called Mean Effective Pressure, or MEP.
It shows the average pressure at which the mechanical work produced by an engine cycle would equal that of the actual work.
#6. Brake Mean Efficiency Pressure.
Brake Mean Effective Pressure (BMEP) is a hypothetical average pressure acting on the piston, similar to Indicated Mean Effective Pressure (IMEP) based on indicated power.
It provides an estimate of the mean effective pressure equivalent to brake power derived from the brake power of the engine.
#7. Specific Output.
Specific Power is a performance measurement that represents the brake power produced per unit of piston displacement. It is a crucial indicator of engine performance since it measures the engine’s power-to-size ratio.
#8. Volumetric Efficiency.
The volumetric efficiency of an IC engine is the ratio between the intake and exhaust volume for the suction stroke (adjusted to standard conditions).
It is crucial for measuring engine performance since it measures how well an engine uses its maximal cylinder capacity for intake.
#9. Specific Fuel Consumption.
Specific Fuel Consumption is a measure of an engine’s fuel consumption rate, expressed in kilos per hour per kilowatt (kW) of power produced.
#10. Thermal Efficiency.
The ratio between the amount of work or power generated by an engine and the pace at which chemical energy or heat is produced during fuel combustion in the engine is known as thermal efficiency.
#11. Compression Ratio.
The ratio of the combustion chamber’s total volume at the bottom dead center (BDC) position to the chamber’s volume at the top dead center (TDC) position is known as the compression ratio of an internal combustion engine.
#12. Air-to-fuel Ratio.
The mass ratio of air to fuel in a combustion process is known as the air-to-fuel ratio, or AFR.
#13. Cylinder Pressure.
The pressure that an internal combustion engine’s cylinders experience during combustion is referred to as cylinder pressure.
Applications of IC Engines
The following are the applications of ic engine:
- IC engines are used in Road vehicles like scooters, motorcycles, buses, etc.
- It is also used in aircraft.
- IC engine is commonly used in motorboats.
- IC engine has great application in small machines, such as lawnmowers, chainsaws, and portable engine generators.