Cryogenic Rocket Engine Seminar Report

The Cryogenic Rocket Engine

Mechanical engineering is totally based upon the laws of physics, Engineering-Mechanics, and Mathematics. Cryogenics is the study of production of very low temperature nearly about ‘123K’ in which the material’s behavior and properties are studied at that temperature. Cryogenic rocket engine is a type of rocket engine designed to use the fuel or oxidizer which must be refrigerated to remain in liquid state.

Working of Cryogenic Rocket Engine

Gas Generator 

The gas generator is used in order to drive the turbo by a gas flow. The gas generated produces this energy by pre-burning some amount of liq. Fuel. Use of Gas generator aligned with Turbopump increases the efficiency of this engine to a great Extent 

Turbo Pumps 

The working of this engine is very easy to understand as it does not involve any complicated cycles or any reciprocating mechanism. The fuel from tanks is firstly passed through the turbopumps which rotate at a speed of about 14000 rpm by which the mass flow rate of fuel increases to about 2.4 tons before reaching the combustion chamber. 

Injector 

Injector plays the most important role in the rocket engine it is like heart of the engine that pumps out the appropriate amount of fuel from the turbo pump to the combustion chamber as per requirement. Injector ensures the stability of the combustion chamber therefore deigning of injector is the most challenging part of the designs department of cryogenic engine even today. The frequency of the combustion chamber is to be maintained between 100-500 cycles per second. If this rate is affected even slightly shifted above or below leads to the failure of engine which has been seen in tragedy of ‘Discovery Spacecraft’.But if the injector is so designed so as to increase the specific impulse more than 700 Space crafts can travel such long distances in the universe. Injector is the only component of this engine which is still under construction yet. 

Combustion Chamber  

Finally when this finely distributed fuel droplets enter into the thrust chamber at such high velocities & at their cryogenic temperatures they colloid to each other in the trust chamber, this reaction at such specific conditions increases the pressure of chamber to about 250 bar with a release of huge amount of thrust which is more than 15000 lb. 
This high amount of trust is then manipulated by a narrow opening towards the nozzle. The opening is kept narrow so as to follow law of rate of discharge which states that ‘velocity is inversely proportional to area’. By this technique, we get the desired amount of thrust which helps a spacecraft to achieve its escape velocity. Due this reaction in continues period of time the temperature of Combustion Chamber as well as nozzle raises up to 3000-4000°C. To withstand such a high temperature for  long period of time without any deformation a cooling Jacket is required. 

Cooling Jacket  

Cooling Jacket is the necessity of this engine but  this facility is provided by the fuel of the engine itself so no external energy is to be used. The mechanism usually used in cooling jackets is active cooling. In this Technique the cooling jacket is made such that a flow if liq. Proponents is passed through the tubes provided from between the jackets. Theliq. propellant passed are already at their cryogenic temperature so provide a very effective cooling. This simple mechanism permits the. Use of this technology throughout it's journey without any deformation in Combustion chamber or Nozzle. 
When all these components work in their perfect algorithm ,only then we can achieve our goal a successful launch of a space vehicle for it's space mission. 

Plume characteristics  

After the reaction in the thrust chamber, Tremendous amount of energy comes from the nozzle through the small opening in the form of plumes. These plumes have a very high temperature during their emissions. Therefore  nozzle is also provided with cooling jacket. As the rocket heads from ground the shape of plumes also changes with respect to height achieved by the rocket.
When the height of rocket is near to sea altitude the ambient pressure acting on rocket & indirectly on engine is more, hence more energy is required to overcome it, so the plume area is less than nozzle diameter at this altitude also efficiency is less.  
When the Rocket advances to a optimum altitude the plume boundary equals the diameter of nozzle  that means ambient pressure equals exhaust pressure.Therefore maximum efficiency is achieved i.e. 100% this phrase gives full efficiency which is only possible in cryogenic engine. After heading this altitude the rocket advances toward vacuum environmental , this area gives optimum efficiency near about 88% which remain constant here onwards. 


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