Gas Turbine Engine Configuration - Essay Example

Gas Turbine Engine Configuration No: Gas Turbine Engine Configuration As the man developed the concepts of transformation of energy and the utilization of fuel to extract mechanical energy, the concepts of engines developed. At first man made simple but innovative designs to develop engines that ignite or burn fuel to provide the mechanical energy. A conventional and typical type of engine burns the mixture of fuel and air in a closed chamber that pushes the piston and the vehicle moves. At first the motive of utilizing the fuel is to drive the crank shaft of the motor vehicle, the main motive remained the same but a newer and powerful type of engine is being utilized today for various purposes that require much more torque and power like in the jet aero planes, etc. such type of engines are known as gas turbine engines. A gas turbine engine is totally an internal combustion engine that burns the fuel to extract the chemical energy stored in the fuel. A gas turbine engine has no cavity that could be named piston. It works on utilizing the behavior of fuel when burnt with a compressed air. The main part of a gas turbine engines is the main turbine and rotor assembly that has the various section that changes the flow of air through the turbine engine. A turbine sucks air into the engine cavity, a compressor attached with the turbine compresses the air (Birch 2001), the next step is to mix the air with the fuel and ignite it and then a compressor that pushes the hot gasses out. The gas turbine engines are classified into four types depending on which part the fuel is ignited. All the four types of the engine have three parts in common compressor, burner and turbine that are named as the core of a gas turbine engines. The four types of gas turbine engines are turbojet, turbo fan, turbo propeller and after burning turbo jet (NASA 2008). Thrust is the amount of force that is the output power of the gas turbine engine and it is responsible for the motion of air craft, etc. The motion of the air craft, which is fitted with a gas turbine engine, is because of the thrust produced by the gas turbine engine (Soares 2007). The motion of an air craft of some other vehicle having a gas turbine engine utilizes the Newton’s third law that states, “For every action there is an equal and opposite reaction” (Holzner 2011). When the fuel is burnt in the Gas turbine engine, the thrust produced by the engine makes the aircraft or turbine to move forward. Forward momentum is the product of mass of the airplane or the vehicle and the velocity with which the aircraft or vehicle is moving. The more the engine produces the thrust, the more will be the forward momentum. In gas turbine engine net thrust is the force that acts on the air craft or the vehicle to help it move. The gross thrust is the force that is produced when the forward momentum is nil. When the aircraft or the vehicle having gas turbine engine is in rest position and the engine is running the gross thrust equals the net thrust but in case when the aircraft or the vehicle having the gas turbine engine is moving or flying the force known as gross thrust is always more than the net thrust. While, in any condition the difference between the gross thrust and the forward momentum is the net thrust (Treager 1996), it can be simplified as the difference between the two momentums acting while the engine is running; the two momentums are out going gas momentum on the exhaust and the incoming air momentum that is entering the engine. Three main factors can vary the thrust of a gas turbine engine, namely, air velocity, air temperature and altitude. Air velocity can be a huge factor that can affect the thrust of a gas turbine engine. At higher velocities the thrust of an air craft increases because the higher the velocity of air the higher will be the air intake pressure and thus higher will be the air mass flow. Inversely, if the air velocity is low, the gas turbine engine behaves normally and the air mass flow remains lower than that of at higher velocity and thus lessen will be the thrust. The second important factor that should be considered is the air temperature, which also affects the thrust of a gas turbine engine. The thrust of a gas turbine engine varies inversely with the change in the temperature, as the air temperature goes up, the thrust of the gas turbine engine becomes less and with lower air temperatures, the thrust of the gas turbine engine increases. In simple words, we can write as at lower air temperature the engine will work better as compared to at higher temperatures. The third important factor that can affect the thrust of a gas turbine engine is the altitude. Altitude is also inversely proportional of the thrust of a gas turbine engine. As the altitude increases the thrust decreases. The reason for the decrease in the thrust is that at higher altitudes the pressure of the air is low and thus the density of the air decreases and in this way, the thrust of the gas turbine engine decreases. If the gas turbine engine is utilized in an air craft, the factor can have a visibility but as the altitude increases the temperature of the atmosphere decrease but the temperature maintains a fixed value all the time (Cavcar 2004). There are many differences in the high bypass triple spool turbo fan engine and a turbo propeller engine. A turbofan is the most utilized type of gas turbine engine. Passengers’ planes are fitted with the turbofan gas turbine engine. Both the engines types have many similarities as both of the engines are gas turbine engines. A turbine, an air compressor, and a fuel ignition mechanism are common in both types of engines. The major difference is that the turbo propeller gas turbine engine has a propeller just like a piston fitted internal combustion engine. Some of the military aircrafts have turbo propeller engines. Before the high bypass triple spool turbofan engines, low bypass twin spool engines were utilized to perform various functions like providing transportation. The high bypass triple spool turbofan gas turbine engines have higher efficiency as compared to all the previous models of the turbofan gas turbine engines. The main differences between the turbofan gas turbine engines the turbo propeller gas turbine engines are that the turbofan gas turbine engines have a canopy covering the fan and the number of blades in the fan is higher, while the blades in the turbo propeller gas turbine engines are three to five and having no canopy to cover the blades. If the both the gas turbine engines are considered economically, the high bypass triple spool turbofan gas turbine engines are much economic as compared to the economy of the turbo propeller gas turbine engines. If both of the gas turbine engines are producing the same amount of thrust, the high bypass triple spool turbofan gas turbine engine will consume much less amount of fuel but in reality turbo propeller gas turbine engines produces less thrust as compared to that of the high bypass triple spool gas turbine engines. That is the reason of utilizing the triple spool gas turbofan gas turbine engines in the passenger aircrafts. Most of times, the gas turbine engines utilize the same type of fuel. The fuel is also known as the standard aviation fuel. The aviation fuel is a petroleum fuel but it may contain some other elements that are included to ensure the higher efficiency and safety during the flight. Anti freezing elements are also included to avoid the fuel from freezing. Lead is the material that is introduced to the fuel to increase the efficiency of the fuel. The latest high bypass triple spool turbofan gas turbine engines are such built to utilize the biofuel that is manufactured from the Jatropha but the turboprop engines utilize the conventional type of fuel. As the high bypass triple spool turbo fan engines are able to produce more trust as compared to turboprop gas turbine engines, the high bypass triple spool turbo fan engines can go to much higher altitudes. However, at altitude the efficiency of the high bypass triple spool turbo fan engines is reduced by the low air pressure. While, the turboprop engines have not the capability to reach such heights that the high bypass triple spool turbo fan engines are capable of. The whole scenario looks like the aircrafts that have the triple spool high bypass turbofan gas turbine engines have the capability of cover higher distances in less time as compared to the turboprop gas turbine engines. Gas turbine engines are the most versatile type of internal combustion engines. A simple gas turbine engine has four most important parts. Air enters the engine through the inlet, a compressor compresses the air. Fuel is then mixed with the compressed air and ignited. The ignition produces thrust and run the turbine, which remains joined to all other parts of the gas turbine engine. Gas turbine engines can be divided into four major categories, which are; turbofan gas turbine engines, turboprop (turbo propeller) gas turbine engines, turbojet and afterburning turbojet. All the engine work on the similar principles of gas turbine engines but having a little differences in the working. A turbofan has a bypass fan that increases the thrust of the engine. A turboprop works on the similar principle as that of the turbo fan but fan is replaced by a propeller. A turbojet has no fan or propeller assembly and directly sucks air and burns it producing a heavy amount of thrust. The similar operation is of the afterburning turbojet but it has an extra stage that again mixes the fuel with the exhaust and burns it to achieve even more thrust. The thrust of a gas turbine engine can be influenced by three main factors that are; air temperature, air velocity and altitude. With increase in the air temperature the capability of the gas turbine engine to produce thrust reduces. With the increases in the air velocity, the capability of the gas turbine engine to produce thrust increases and with increases in altitude the efficiency of the gas turbine engine decreases. Bibliography Birch, R. E. (2001). Gas Turbine Engines: For Pilots and Mechanics. Jeppesen Sanderson. Cavcar, Mustafa. (2004). Jet Engine. Turkey: Anadolu University, School of Civil Aviation. Retrieved on 31st December 2011 from http://home.anadolu.edu.tr/~mcavcar/common/Jetengine.pdf Treager, I.E. (1996). Aircraft Gas Turbine Engine Technology. New York: McGraw-Hill Higher Education. Soares, Claire (2007). Gas Turbines: A Handbook of Air, Land, and Sea Applications. USA: Butterworth Heinemann. Holzner, Steven. (2011). Physics I for Dummies. 2nd Edition. USA: John Wiley and Sons NASA: National Aerostatics and Space Administration. (2008). Types of Gas Turbines. Glenn Research Center. Retrieved on 31st December 2011 from http://www.grc.nasa.gov/WWW/K-12/airplane/trbtyp.html Read More