SCRAMJet Engines

Scramjet is upgrade of ramjet we can say. It stands for supersonic combustion ramjet engine. It is not really different from ramjets.

Here the combustion of fuel happens at supersonic speed. The aircraft fitted with this type of engines can fly at hypersonic speeds i.e. Mach No. > 5.

Ramjets!!!

Oh its been a while i wrote a blog, anyway i am back!

So not talking about any basics and talk about something really interesting and exciting...

Ramjet engine, makes the aircraft to go lightning fast, probably up to a mind whopping 4 Mach. It does not have rotary parts like compressor or turbine as in turbojets, turbofans, etc. Ramjets are sort of simple designs used more in missiles. This type of propulsion systems need some initial speed to start functioning. So missiles are launched and once it meets the required initiation speed the engine ignites and takes the missile to the target.

At the inlet the Mach no. (M) is greater than one, the compression takes place at M <> 1. You can get an idea of it from the picture above.

Understanding the engines

Reciprocating engines are the efficient compared to

rest. But it has limitation of altitude & payload. Adding supercharger to the engine increases operating altitude for the engine.

Turboprop engines are combination of turbine and propeller. These are also very efficient, have a better payload carrying capacity, can fly at higher altitude compared to reciprocating engines. But cannot go to higher speeds, reason being increase in the blade tip velocity to sou

nd speed may cause the blades to go off the assembly.

Turbojet engine is by far the most efficient engine. It can go at speeds as high as 4 mach. Its efficiency increase with altitude.

Turbofan engine is a combination of turboprop and turbojet. It has a fan before the inlet which draws the air. Its efficiency lies in between turboprop and turbojet.

Types Of Engines

Jet Engines can be mainly divided into two parts: 1. Air Breathing Engines 2. Non air Breathing Engines

Air Breathing Engines include reciprocating, turboprop, turbojet, turbofan and turboshaft engines.

Non air breathing engines include rocket motors, nuclear propulsion system and electric propulsion engines.

There are also other engines like pulse jet engines, pulse detonation engines(PDE), RAM Jet engines and SCRAM Jet engines.

I will discuss these engines in detail in my later posts.

What is PROPULSION?

I wrote about Kaveri engine in detail in my previous blogs. Now i would like to start with some basics of propulsion.

My wish is to write pertaining propulsion, so, let us see what propulsion actually means...

Propulsion means to move any body in some direction with aid of some force.

Propulsion is defines as "the act of propelling, the state of being propelled, a propelling force or impulse" and defines the verb propel as "to drive, or cause to move forward or onward".

From the above definitions we can say that propulsion includes the study of propelling force, the motion caused and the bodies involved.Propulsion involves a body to be propelled and more than one additional bodies, called the propellant.

Prblems in Kaveri project!

Kaveri has many advanced and technologies which would help India to develop jet engines independently. But unfortunately this project was failure due to several problems. The turbine n the engine has a tendency to "throw" the blades off, which required securing blades from SNECMA.

Due to repeated snags in the engine resulted in the 2003 decision to procure the uprated F404-GE-IN20 engine for the eight pre-production Limited Series Production (LSP) aircraft and two naval prototypes. ADA awarded a deal of $105 million to General Electric in February 2004 for development engineering and production of 17 F404-IN20 engines, delivery of which is to begin in 2006.

In mid-2004, the Kaveri failed its high-altitude tests in Russia, ending the last hopes of introducing it with the first production Tejas aircraft. Becasue of all this Indian Ministry of Defence (MoD) orderen 40 more IN20 for the first 20 production aircraft, and openly appealed for technical assistance in the development of Kaveri. In 2006 ADA awarded a contract to SNECMA for technical assistance in rectifying problems in Kaveri.

Kaveri Engine for LCA

This engine is specifically designed as per the indian operating environment, which ranges from hot deserts to high mountains. With overall pressure ration of 27:1 it can help Tejas(LCA) to supercruise (fly at a supersonic speed without afterburner) as per GTRE. It has 13% higher thrust than already used prototypes of GE on the flying machine. Tejas will have such two engines with fully vectoring nozzles which could make the vertical tail redundant. (Tejas do not have a horizantal tail). An indigenous Fully Authority Digital Engine Control(FADEC) unit called Kaveri Digital Engine Control Unit(KADECU) has been developed by Defence Avionics Research Establishment(DARE).

With above specificaions Kaveri seems to be a successful initiation for India in indigenous production of Jet Engines.

Kaveri Engine for LCA

The production of this engine was handed over to Defence Research and Development Organisation(DRDO) in 1986. This was a step to built an indigenous jet powerplant system....

It was decided on at the early times that GE engines will be used to equip prototype aircraft. But if Kaveri project would turn out to be successful, kaveri would be the first priority.

Kaveri Engine for LCA

Light Combat Aircraft(LCA) is a project started in 1980s which is still on the roll. Propulsion system planned for this aircraft is Kaveri. It is a low by pass ratio turbofan engine. This project was handed over to Gas Turbine Research Establishment(GTRE) in 1989 and was expected to be a project of 382 crores.

But the program was de-linked form HAL LCA Project in 2008.