TURBOJET ENGINES

Introduction

Turbojet engine takes its oxygen supply from the surrounding atmosphere. The turbojet engine consist of a diffuser, compressor, combustion chamber, turbine and a expansion nozzle.

The air is compressed in to the chamber, heated and expanded by the fuel combustion and then allowed to expand out through the turbine in to nozzle were it is accelerated to high speed to provide propulsion (moving forward)

Working Principle: - Atmospheric air enters into the diffuser with the same velocity as that of the propulsive unit. The function of the diffuser is to convert the kinetic energy of entering air in to pressure energy of it. High pressure air now enters into the compressor were its pressure is further increased and its temperature also increases correspondingly.

The high pressure and high temperature compressed air now inters in to a combustion chamber in which a liquid fuel is injected through a ring of injectors by means of a pump. In the combustion chamber, the fuel burns at constant pressure by coming in contact with hot compressed air. Hot gases thus produced in the combustion chamber, now enter into a gas turbine in which it expands producing power. It is with this power that compressor and the fuel pump are operated. The exhaust gases from the turbine now pass in to the atmosphere through the expansion nozzle. As the exhaust gases pass through the nozzle. Its pressure energy is converted into kinetic energy and the gases leave the nozzle with a very high velocity producing a reactive force or thrust in the opposite direction. This thrust carries the propulsive unit forward. To start the unit, a starting device such as electric motor is required.

The Turbojet Engines Are Used In Aircraft

Advantages of turbojet engine

 The following are the advantages

·         Simplicity in construction

·         Free from vibrations

·         Higher rates of climb

·         Uninterrupted and smooth power supply

·         Low specific weight (weight to power ratio)

·         Speed as high as 3000 kmph are possible

·         Minimum over-hauling

 Disadvantages of turbojet engine

The following are the disadvantages

·         Low efficiency

·         expensive materials

·         not efficient in performance below 550 kmph speed

·         More noisy