General Classification of IC Engine

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What will you know after reading this article?

  • General Classification of IC engines
  • Main difference between four stroke engine and two stroke engine
  • Main difference between SI engine and CI engine


In previous articles, We have learnt about Engine types, parts and nomenclature. We know there are two types of engine, first one is internal combustion engine and other one is external combustion engine. Both these engines are widely used in mechanical industries but due to low weight to power ratio and mobile facility IC engines are widely used in  automobile industries. 
IC engines are a major part of automobile study. Mostly we aware about only two types, petrol engines and diesel engines but, there are many other parameter on which a engine can classified. 

Classification of IC engine:

IC engines can be classified on the basis of fuel used, thermodynamic cycle, type of ignition, type of cooling system, cylinder arrangement, method of charging etc.  Now we study about it in detail. 

According to Cycle of Operation:

We know IC engines convert chemical energy into mechanical energy in a cyclic operation. There are many thermodynamic cycles like Carnot cycle, Otto Cycle, Diesel Cycle, Rankine cycle etc. IC engines works on three cycles Otto cycle and Diesel cycle and Dual cycle. So according to it, IC engine can be classified into following types.

Otto Cycle Engine: It is also known as spark ignition engine or constant volume heat addition engine, Petrol engine etc. In this cycle heat addition (fuel burn) and rejection (exhaust) takes place at constant volume and expansion and compression takes place at isentropically. These engines give low power at high speed.

Diesel Cycle Engine: This is known as compression ignition engine, diesel engine, constant pressure engine etc. In this cycle heat addition (fuel burn) takes place at constant pressure and heat rejection takes place at constant volume.  This engine gives high power at low speed.

Duel Cycle Engine: Dual cycle is combination of Otto cycle and Diesel cycle. In this engines, heat addition take place both at constant volume and constant pressure in some ratio. 
Some engines works on Strilling cycle and Ericsson cycle but these are not used commercially. 

According to Type of Fuel Used:

Most of us know about these engines. These are petrol engine and diesel engine. Now days gaseous fuel like LPG, CNG, hydrogen etc. are also used in IC engines. These engines are called non-traditional engines.

According to Method of Charging:

Charging means how admission of fuel air mixture take place. This can be classified as follow.

Natural aspirated engine: In this engines, admission of air fuel mixture (SI Engine) or air alone (CI engine) takes place due to pressure difference inside the cylinder and atmospheric pressure.

Supercharged Engines: In this engines, a separate compressor is used to admission of charge inside cylinder. This compressor is run by using engine power (connect with crankshaft with belt drive).

Turbocharged Engine: This engines, uses a turbine which draw air into the cylinder and run by using exhaust gas power. It is also like supercharge but the compressor is run by a turbine which is rotate by exhaust gases.

According to Ignition:

In IC engine ignition of charge can be take place in two ways. In first one, a separate spark plug or any other device used to ignite the fuel (Spark Ignition Engine) and other one is fuel ignite due to heat generate during compression or fuel (Compression Ignition Engine). So according to this methods, two engines are available spark ignition engine or SI engine (Petrol Engine) and compression ignition engine or CI engine (Diesel Engine).

According to type of Ignition System:

In petrol engines, we used spark plug to ignite the fuel. This spark at spark plug, produce by an ignition system. According to ignition system two types of engines are there. The first one is battery ignition engine (use a battery to generate spark) and other one is magneto ignition engine (use a small generator to generate spark).

According to Design of Engine:

Reciprocating Engine: In this type of engine, a piston is used which moves in reciprocating motion by using pressure force generated by burning of fuel. The crankshaft converts this reciprocating motion into rotary motion. Most of automobile engines are reciprocating type.

Rotary Engine: In rotary engine, a rotor is used. The pressure force generated by burning of fuel exerted on this rotor, which further rotate the wheel. Wankel engine is one type of rotary engine. These engine are currently not used in automobile engines. 

According to cooling:

Two types of cooling used in IC engines, air cooling and water cooling. So the engines are air cooled engine or water cooled engine. Both these cooling system have their own advantages, which we will discuss later. Engine oil is also serves as cooling medium.

According to stroke of engine:

In the previous¬†article “nomenclature of IC engine“, we have learnt about stroke. We know stroke is the maximum distance a piston can travel inside the cylinder or distance between TDC to BDC. If a engine moves from TDC to BDC, it is called one stroke. If it return to BDC it is called two stroke. A crankshaft makes one rotation in two strokes. According to it, three types of engines have invented.

Two stroke Engine: In this engines, crankshaft makes one rotation in one power stroke. This engines give more power compare to others. It is used in shooters, ships, generator, etc.
Four stroke engine: This engine gives two crankshaft rotation in one power stroke. They gives low power but high efficiency. It is used in cars, trucks, bikes etc.
Six stroke engine: These engines are in development process. As the name implies, it will give three crankshaft rotation in one power stroke.

According to arrangement of engine:

These engines can be better understood by diagram compare to words.

Now you should ask yourself these questions?

  • How IC engine can be classified?What are supercharged and turbocharged engine?
  • What are difference between SI and CI engine?
  • What are main ignition and cooling system used in IC engines?


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