SUPERSONIC COMBUSTION

What is supersonic?

             Any speed over the speed of sound (Mach 1), which is approximately 340 m/s, 1,087 ft/s, 761 mph or 1,225 km/h in air at sea level, is said to be supersonic.

what is supersonic combustion?

            If any engine reaches that speed, that engine is called as sonic propeller. Here the combustion takes place above the speed of sound. Therefore it is called as supersonic combustion.

INTRODUCTION
 

During the 1st century, Hero of Alexandria

invented the aeolipile.

It uses steam to power jets that turn a metal 

Aeolipile demonstrates the first use of jet propulsion principles.

      

PRINCIPLE OF JET


 PROPULSION

                              

                  Jet propulsion is based on Newton’s second law and third laws of motion. Newton’s second law states that the rate of change of momentum in any direction is proportional to the force acting in that direction.

                    

                   Force = Mass x Acceleration

         Newton’s third law of motion states that “for every action, there is an equal and opposite reaction”.

 TURBO MACHINERY

      Turbo machinery: Rotating machinery incorporating a turbine that operates through the 

action of rows of blades in order to add or remove mechanical power from a continuously 

flowing stream of fluid.

Used to attain speeds from much less than Mach 1 all the way to Mach 24(theoretical).

Efficient in moving large and heavy objects a large distance.

Used in various applications and machines:

Generators

Aircraft

Cars

                     Ships ETC...,

MACH NUMBERS


                      Dividing an object’s speed by the speed of sound yields its Mach number, a ratio named for 19th-century Austrian physicist Ernst Mach, who laid out the principles of supersonic speed. Mach 1 equals the speed of sound (transonic), and a Mach number lowers than 1 is subsonic. Supersonic covers speeds greater than Mach 1 up to Mach 5, and hypersonic is any speed greater than Mach 5.

 REQUIREMENTS OF SCRAM JET ENGINES

                  

                     Normal aircraft engines in today’s high performance aircraft have no hope of achieving orbital velocity. To date, the fastest manned aircraft powered by an air-breathing engine is a Lockheed SR-71 “Blackbird”, and it set the speed record at 2,193 mph (Mach 3.2), still hopelessly below orbital velocity.   The “Blackbird” aircraft were powered by ramjet engines, and were constructed almost entirely of titanium and titanium alloys.

BASIC DESIGN OF THE SCRAM JET ENGINE

 

             The design of scram jet engine is very similar to a basic ramjet engine.  The main difference is that the airflow through the engine remains supersonic.  To accomplish this, scram jet engines rely heavily on the shape of the entire aircraft.  A concept known as “airframe-integrated scram jet” became the standard for most vehicle designs and wind tunnel tests (Rogers, et. al., 1998). 

          The front section of the aircraft is shaped such that the shock waves produced at the aircraft’s leading edges are funneled into the engine.  This concept, along with the geometry of the engine inlets, compresses the air for combustion with the fuels. 

SCRAM JET

        1 Supersonic Combustion Ramjet.

         2 Very similar to the Ramjet.

         3 Compresses air and keeps it at a supersonic speed.

         4 Combustion occurs with the use of hydrogen instead of jet fuel.

         5 Air’s temperature and pressure drastically increase, accelerating the aircraft.

         
         6 Scram jet only works once it has reached a speed of Mach 5.

         7 Theoretical speeds range between Mach 12 to Mach 24 or hypersonic.

         8 Fastest recorded speed is Mach 9.6 by NASA’s X-43A.

COMBUSTION

 

 

 ADVANTAGES OF SCRAM JET 

1 There are two main advantages of scram jet propulsion over rocket propulsion for lifting vehicles into orbit. 

2 The first major advantage is weight savings.  By avoiding the requirement to carry one’s own oxidizer, weight of orbital vehicles can be drastically reduced.  This in turn requires drastically less fuel, the end result being a dramatic reduction in overall cost. 

3   The second major advantage is maneuverability.  Should malfunctions occur during takeoff or ascent, a scram jet-powered aircraft could safely cut its engines and return to its runway.

EARLY ATTEMPTS

           Experiments continued on various geometries for inlets, combustion chambers, and exhausts.  Scram jet test capability has been continually improved at LaRC over the past 40 years… More than 3500 tests were performed, providing about 30 hours of testing, equivalent to about 4 trips around the world at Mach 5. Results from these tests verified scramjet powered vehicle performance and were instrumental in the Supersonic combustion research history 1984.

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