Types of fuel used in internal combustion engines

Before starting discussing the types of fuels used in internal combustion engines, we, first need to elaborate the types of internal combustion engines and their mechanisms. After having discussed the mechanical features of different types of internal combustion engines, we will find out which types of fuel are used in various types of engine, what why a specific type of fuel is fit for a specific engine. Here are some kinds of internal combustion engines. Along with the different types of mechanisms involved in these engines, we will discuss the different types of fuels used in them, and also mention the reason behind the use of a specific types of fuel used in an engine.

(1). Two stroke Petrol Engine:

A two-stroke petrol engine completes its one rotation by taking out two strokes. In the first stroke, the piston of the engine moves into the combustion chamber. The piston at half of its journey sucks the fuel mixed with air, and on the second half of its journey, it pushes the fuel-enriched air and compresses it to some extent. The first stroke carries out two jobs, (i) sucking the air, (ii) compressing the air. Therefore this stroke is known as the charging+compression stroke. When the piston is completely inside the combustion chamber, the sparking plug sparks the fuel mixture. On sparking, the fuel mixture gets combusted. At this stage, both the inlet and the outlet holes are closed, so that the heated gases may push the piston backward. When the piston is pushed backward, it crosses over the outlet hole, thus allowing the hot gases out through the outlet hole. After exhausting the waste gases, the second phase of this stroke starts. When the gases are expelled out, the piston is still pushed down by means of the flying wheel. At this stage, the fuel mixture is again sucked via the suction plate. This stroke carry out two tasks, (i) exhausting the burnt gases, (ii) sucking the new fuel mixture. This is why we can it as the exhausting+charging stroke.

A two-stroke engine is so called, because the rotation of the wheel is completed by only two strokes  (to-and-fro motion) of the piston.

Fuel used in this type of engine: Unlike a diesel engine the fuel mixture is not compressed too much, therefore, the compression does not result in a compressional heat to ignite the fuel. We need a sparking plug to ignite the fuel. We can not use diesel in these types of engines, because diesel does not combust by an ignition spark. Therefore petrol is needed to be easily ignited by a sparking plug.

(2). Four Stroke Petrol Engine:

Four-stroke engine - WikipediaA four-stroke petrol engine completes its one rotation by taking-out the four strokes, meaning that four movements of the pistons.

  1. First stroke is known as the charging stroke. In this stroke, the piston (standing completely inside the combustion chamber) starts moving downward in the combustion chamber This is known as charging stroke. When piston starts moving downward, the inlet valve opens and allows the air and fuel to be inhaled.
  2. Second stroke starts when the piston again starts moving upward in the combustion chamber. At this stage both the inlet and outlet valves are closed, thus the piston pushed the air/fuel and compresses it to some extent. When piston is on its top, it has completely compressed the air/fuel. At the end of this stroke a sparking plug hits the piston with a spark to ignite the fuel.
  3. Third stroke starts with the ignition of fuel, and in this stroke piston again moves downward due to the combustion energy (both the valves are closed). When the piston is fully pushed downward the third comes to its end. At the end of the third stroke the outlet valves gets opened.
  4. The fourth stroke starts with the opening of the outlet valve. Now the piston again moves upward, with outlet valve opened, thus pushing the burnt gases out of the chamber. The fourth stroke completes with the complete exhaust of the burnt gases.

Fuel used in a four-stroke petrol engine: In this type of engine we use petrole, because unlike diesel engine the fuel is not compressed too much to create enough compressional heat to ignite the fuel. Therefore, the sparking plug can ignite petrol rather than diesel. Petrol is much combustible as compared to diesel.

(3). Diesel Engine (four-stroke):

Four-stroke gasoline or diesel engine: how it works, animation
Explanation of the 4 strokes of a diesel engine

A diesel engine uses diesel for generating mechanical energy. The working mechanism of a diesel engine and the four-stroke petrol engine is quite similar. The only difference is, in a 4-stroke petrol engine the ignition is taken out by means of a sparking plug, while in a diesel engine the ignition is taken out by the compression heat produced by the compression of air and fuel. The rest of the mechanism between both the engines is similar.

(4). Wankel or Rotary Engine:

A Wankel engine also called rotary engine is an Internal combustion engine, which uses petrol as fuel to produce mechanical energy.  Unlike the piston-cylinder arrangement the Wankel engine uses the eccentric rotor design, which directly converts the pressure energy of gases into rotatory motion. While in the piston-cylinder arrangement, the linear motion of the piston is used to convert into rotatory motion of crankshaft.

Rotary Engine - an internal combustion engine, the heat rather than the piston movement into rotary movement | Wankel engine, Automotive engineering, Engineering
Working Mechanism of a Wankel Engine

Basically, in a simple way, the rotor revolve in housings shaped in a fat figure-of-eight. During rotation, the eccentric crank rotor compresses the fuel-air, and by means of the sparking plug the fuel is ignited. The rotation continues and at another stage, the combustion chamber is widened due to the eccentric motion of the rotor. At widening stage, there is opening/outlet valve to expel the burnt gases out of the chamber.

(5). Jet Engines/ Rotary Turbine:

The Jet Engines are also called the “Gas Turbine”. It uses petrol, methane gas or maybe hydrogen gas to produce mechanical energy.

A Jet-engine works on the simple principle. The engine sucks air in at the front by means of a fan. After sucking the air, the compressor raises the pressure of the air. The compressor has many blades attached to a shaft. The blades spin at high speed and compress or squeeze the air. The compressed air is then sprayed with fuel and an electric spark lights the mixture. The burning gases expand and blast out through the nozzle, at the back of the engine. As the jets of gas shoot backward, the engine and the aircraft are thrust forward. As the hot air is going to the nozzle, it passes through another group of blades called the turbine. The turbine is attached to the same shaft as the compressor. Spinning the turbine causes the compressor to spin.

Turbojet Engine

This animated image explains the working mechanism of a jet-engine well.


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