With the dawning of the new scenario man wants speed to satisfy his demands, his needs, but this is not possible with the conventional jet engines due to the many constraints regarding the speed of jet engine and this gives birth to the very high speed engine which achieve even the hypersonic speed called as scramjet engine. In the scramjet engine the design is made in such way that, without any working parts it achieve hypersonic speed.
Since the down of human civilization, it has been man’s strong desire to fly like a bird. This dream comes true with the invention of flying machines. The airplane. But still he is not satisfied; one thing which attracts him is speed. He would like to fly higher and faster, so the jet engines are invented. The hunger for the speed and the power goes on increasing. Therefore a passionate beast man is still going for new invention. One of the jewel in his hand is newly designed “scramjet engine”.
This paper gives an overview of a 21st century engine “scramjet” which can attend a speed up to mach no 10 (8000 km/hr). Research is being carried out throughout the world by various organizations viz. NASA (National Aeronautics and Space Administration), NAL (National Aerospace Limited), QUEENSLAND University of Australia and also in India by DRDO (Defense Research and Development Organization) and ISRO (Indian Space Research Organization) on the same. All these organizations have their own rules and regulations to keep the information confidential. Scramjet technology depends upon ramjet and turbojet technology, which are the types of jet engine. So first turn towards the first engine.
During the Second World War, in 1939 the jet fighter named the Heinkel HE 178 built by Emst Heinkel became the world’s first combat jet aircraft. Within two years, it was followed by the Gloster E 28/39 powered by a jet engine designed by WHITTLE.
How the Jet Engine works is based on the Newton’s third law of motion- “To every action there is equal and opposite reaction”. A gas turbine engine consists of three main parts. At its front is compressor, which is a series of fans that spin at very high speeds (around 16,000 revolutions per minute). These blades pull air in and send it through a channel that gets progressively narrow. As the air in and send it through a channel that gets progressively narrow. As the air moves through this channel, it is compressed until it is anywhere from 10 to 30 times more dense than it was to start with. Alternating with these spinning blades are the stationary fan blades also called stators, they are there to make the
flow of compressed air move in a straight line rather than in swirling currents that would make the air burn less efficiently when it reaches the combustion chamber.
The combustion chamber is the second main section of a gas turbine engine. There, fuel- a refined form of kerosene, in the case of jet airplanes- is injected into the pressurized gas. When the engine is first started, igniter plugs are used to get the mixture burning. Once initial ignition is achieved, combustion is continuous, with the gas that is already burning igniting the fuel-and –air mixture that flows into chamber. Temperatures of around 2,500 degrees Fahrenheit are typical inside a gas turbine combustion chamber.
The third section of a jet engine is the turbine. As the hot gasses are expelled-at speeds well above 1,540 km per hour-they provide power in the form of thrust. They also turn a series of fans that are much like the blades found in the compressor portion of the engine. These fans in turn provide the power to turn those compressor blades. Remember, it is the pressure exerted by the thrust is on the wall of engine itself and not the pressure of gas pushing against the outside air.
1. Simplest type of gas turbine having no moving parts.
2. Cheap and require no maintenance
3. Due to absence of turbine, maximum temperature allowed ramjet is 2000 C as
compared to about 900 C in turbojets.
4. Specific fuel consumption is better than other gas turbine at high speed and high
5. No upper limit of flight speed.
Since the compression of air is obtained by virtue of its speed relative to the engine, the take-off thrust is zero and it is not possible to start the ramjet without an external launching device.
Today scramjet is not just a concept, as it has become a reality. Though a scramjet has simple mechanism, it is technically so complex engine. Successful working of this engine is solely depend upon the airflow. This engine requires careful designing and construction with negligible tolerance. Within a decade or so hyper planes and such highly sophisticated aircraft will become a part of your routine life. In the future, scramjets could be used to launch satellites, visit space stations, or travel from New York to Tokyo in under three hours. In other words, the dream of space tourism is likely to come true.
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