Diesel Engine | Working, Types, Applications [Full Guide with Images]

By | October 7, 2018

What is a Diesel engine?

Diesel engine is a machine (Internal Combustion Engine) that converts chemical energy of diesel fuel into the Mechanical energy. It was invented by Rudolf Diesel.

It is a type of Internal combustion engine which works on Diesel (fuel). In Diesel engine combustion of fuel happens due to high temperature and pressure inside the combustion chamber.

Types of Diesel engines

On the basis of number of strokes required to complete the combustion process, diesel engines can be classified into two types.

  1. Two stroke diesel engine
  2. Four stroke diesel engine

Working of Diesel engine

Diesel engine works on the Diesel cycle. Irrespective of number of strokes required to complete the combustion process, a diesel engine works in following steps.

Note: We are not particularly concerned here on two stroke or four stroke engine.

Step 1: Suction of air from environment

In this step engine sucks air from the environment and then compresses it.

Step 2: Injection of fuel

In this step fuel is injected to the engine at very high temperature and pressure.

Step 3: Combustion

Due to very high temperature and pressure inside the engine, the fuel explodes, which results in the reciprocating movement of the piston.

Step 3: Exhaust

In this step exhaust gases of combustion process are made out of the engine.

Again, fresh air is sucked and the cycle goes on and on.

Here is a video showing working of diesel engines (and its comparison with Gasoline or Petrol engine).

Diesel Cycle explanation

A diesel engine works on diesel cycle. There are four processes in diesel cycle (as shown in diagram)

Diesel Cycle

Diesel Cycle

Process 1-2

It is the isentropic compression of the air which is sucked in from environment. In this process work (Win) is done by the system to compress the air.

Process 2-3

It is where the diesel is injected. It is an isobaric process. Here fuel burns due to high temperature and pressure. In this process engine gets heat (Qin).

Process 3-4

It is the power stroke. It is an isentropic expansion process. The work obtained here is Wout.

Process 4-1

In this an isochoric process. In this step all the exhaust gases of combustion process are made out of the engine. Some heat also gets wasted with exhaust gases i.e. Qout.

Advantages of Diesel engines

There are several advantages (compared with Gasoline or petrol engines) of Diesel engines, some of them are.

  • They are more efficient
  • They are more durable
  • They generate greater torque
  • Absence of spark plugs lowers the cost

Limitations or disadvantages of Diesel engines

Some disadvantages of diesel engines (compared with Petrol or Gasoline engines) are.

  • High speed performance is not that good
  • Regular maintenance is required
  • They are heavier

Applications of Diesel engines

There are several applications of diesel engines and some of them are.

  • Diesel generators
  • Locomotives
  • Farming equipment
  • In construction equipment
  • In cargo and cruise ships
  • In buses and trucks

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