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India-US jet engine deal: What are jet engines? Why is this deal important?

Technology around manufacturing jet engines capable of powering fighter aircraft is very closely guarded and remains the biggest impediment for countries wanting to develop their own combat aircraft

GE F414 (GE Aerospace website)

GE F414 (GE Aerospace)

Mayank Pandey New Delhi
Giving new wings to the India-US ties, US jet engine manufacturer General Electric (GE) and India's Hindustan Aeronautics Limited (HAL) have signed a Memorandum of Understanding (MoU) on Thursday, June 22 to produce combat aircraft engines for the Indian Air Force.

The announcement was part of Prime Minister Narendra Modi's agenda on his state visit to the United States of America (USA). The agreement paves the way for the potential joint manufacturing of GE's famous F414 engines in India. This engine will power India's homegrown Light Combat Aircraft (LCA) Tejas Mk2.


Why is the deal so special?

The deal assumes significance because very few countries around the world have the know-how to develop their own jet engine. So far, only the US, Russia, the UK, and France have the expertise to develop jet engines independently.

The technology and metallurgy around manufacturing a jet engine capable of powering a fighter aircraft are very closely guarded and remain the single biggest impediment for countries worldwide wanting to develop their own combat aircraft.

In fact, India has been ambitious about developing its own jet engine, and to this end, it sanctioned the Kaveri engine project in 1989. However, DRDO's Gas Turbine Research Establishment (GTRE) could not achieve the desired results after multiple attempts. This engine's thrust and power figures were not adequate to meet Indian Air Force's operational needs.

This resulted in a situation where the LCA Tejas program had to choose a GE F404 engine.


How good is the GE F414 engine?

The US Navy has used the technology setup used to build the GE F414 engine for more than thirty years. This engine is used in F-18 Super Hornets and is known for its reliable performance.

The F414G, the single-engine variant of the F414, has been chosen for Saab's Gripen E/F aircraft, GE's official website said. Its predecessor, the GE F404, powers the Tejas LCA.

The GE website says more than 1,600 GE F414 engines have been delivered.


What is a jet engine?

A jet engine is an internal combustion engine that pushes an aircraft ahead by producing a rearward discharge of a fluid jet. The 'jet' refers to the discharge of a mix of hot exhaust gases produced by burning fuel with air.


How do jet engines work?

Imagine when a balloon filled with air slips from our hands before we have tied a knot on it, and it starts moving in all directions. It does so until it has air in it. The balloon makes these movements because of the fast release of air from one end that pushes the balloon in the opposite direction of the release of the air. This is what Newton explained with his third law of motion.

Simply put, something similar happens in the jet engine, where the plain air is replaced by a stream of gases containing fuel and air that leave the engine at a very high temperature and velocity, producing the required thrust that propels the aircraft forward.

In order to achieve this thrust, air enters the engine through its wide inlets in the first stage. As the air travels further inside, it is compressed in multiple stages. Air compression is carried out using various fan-like rotators placed one behind another, with their size becoming smaller and smaller.

Another mechanism that compresses the air is the design of the engine case itself. The engine's cross-section is widest at the air-inlet point, and it is narrower as the air travels through the engine and towards the outlet.

As the air travels through the engine, it is taken through various compression stages. As the compressed air reaches the combustion chamber, fuel droplets are introduced to the compressed air. (Combustion chamber is part of the jet engine that contains multiple tubes that discharge fuel. When this fuel meets the compressed air, combustion happens.)

At this stage, the hot air ignites the fuel generating a high-energy fluid that makes the turbine blades turn as it leaves the combustion chamber. As the gases leave the turbine and rotate it, the rotational energy thus produced is utilised to power the turbines placed near the inlet point of the jet engine. As the fluid exits the jet engine, it generates the required thrust that pushes the aircraft forward.
 

Types of Jet Engines

There are six types of jet engines: 

  1. Turbojet 
  2. Turboprop
  3. Turbofan
  4. Turboshaft
  5. Ramjet, and
  6. Scramjet


Each engine has a slightly different design and is used in different kinds of aerial vehicles.


Turbojet engine

These are the most basic and oldest type of jet engines. They work on the principle of taking the air and compressing it to a point where it becomes hot and pressurised. At this point, fuel is added to the combustion chamber resulting in the burning of fuel that produces extra thrust to push the aircraft forward.


Turboprop engine

The turboprop engine is nothing but a Turbojet engine attached to a propeller. A turbine attached near the engine outlet is turned by the hot gases produced in the combustion chamber, much like in turbojet engines.

These engines have better propulsion efficiency and are suitable for aircraft that fly at speeds below 500 miles per hour. Thus, they are used in small airliners and transport aircraft.


Turbofan jet engines

A turbofan jet engine is characterised by the presence of a large fan at its front end. The fan helps suck more air. In these engines, not all air passes through the jet engine, some of which passes from the outside of the engine. This makes the engine quieter and produces more thrusts at low speeds.

Because of their better fuel efficiency, most commercial airlines are powered by turbofan engines.

 
Turboshaft engines

Turboshaft engines are also a type of gas-turbine engine, but the primary focus in these engines is to create maximum shaft power instead of jet thrust.

In these engines, a power shaft is attached at the end of the jet engine, which utilises the exhaust thrust to rotate itself at high speeds. Due to their additional power output, high reliability, and compact form, they are used in helicopters.


Ramjet engines

This engine is the most simple in its construction as it has no moving parts. While ramjets also work on the same principle of compressing air to high temperatures and adding fuel thereafter, these engines do the same but differently.

With no turbines and propellers present, ramjet engines need to reach a certain speed to become active. In other words, they can not work at speeds below a certain level. Essentially, they need the air to be rammed into their inlets at high speeds.

This means that a ramjet vehicle requires some form of assistance to reach such speeds. For optimum performance, ramjets need to attain speeds of around 0.5 Machs, before they can start functioning.

These engines are primarily used in the guided-missile systems and space vehicles.


Scramjet engines

A scramjet engine is a type of ramjet engine that operates at supersonic speeds (more than the speed of sound). Scramjet engines allow aerial vehicles to attain even faster speeds. They have a more streamlined design which is only possible because they do not need the airflow to be slowed for combustion. Rather, they utilise the high-speed intake of air directly without the need for a combustion chamber housing in the engine. This makes scramjets engines more fuel-efficient at high speeds.

However, attaining supersonic speeds adds to the complexities of this engine. Compared with ramjets and turbojets, they are also more expensive to manage and maintain.
 

Companies that make jet engines

There are a number of companies engaged in manufacturing these jet engines, mostly based in the Western world. Prominent jet engine manufacturers include Pratt & Whitney (US), General Electric (US), Honeywell Aerospace (US), Safran (France), Rolls-Royce (UK), Aviadvigatel (Russia), NPO Saturn (Russia).
 

Countries that can make their own jet engines

So far, only the US, Russia, the UK, and France have the expertise to develop jet engines independently.


Cost of jet engines

Commercial jet engines can cost between $5 and $50 million, depending on the size and use-case requirements. The engines used in the ace US fighter plane Lockheed Martin F-35 cost anywhere between $45 and $65 million, according to a simpleflying report.

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First Published: Jun 23 2023 | 3:50 PM IST

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