Key Aspects of the Jet Engines - Coursework Example

Jet Engine No: Out line Jet engines Introduction: Jet engines are efficient and have more power toweight ratio as compared to normal internal combustion engines. Thesis statement: Jet engines are highly efficient combustion engines. Several types of jet engines are utilized in various applications. Main body Jet engines are gas turbine engines. The main parts of the jet engines or gas turbine engine are turbine, compressor, fuel ignition system and a connection rod that connects turbine and compressor. Jet engine output is evaluated with respect to the amount of thrust. Forward momentum moves the engines vehicle in forward direction. During the flight of aeroplane gross thrust is more than net thrust. The four types of gas turbine engines are the turbojet, turbo fan, turbo propeller and after burning turbo jet. Turbo propeller jet engines have a propeller that is attached to the main rotor of the jet engine that drives turbine and compressor. Afterburning turbojet engines have an afterburner at the back of the turbine. Altitude, air pressure, air temperature influence the thrust of the engine. Advantages: Maximum power to weight ratio as compared to other types of engines. Consumes less fuel for constant load. Immense rotating speed that is good of airplanes. Fewer engines parts. Small and compact according to output power produced. Disadvantages Jet engines produce high frequency and high pitch sound. The sounds can produce temporary and permanent hearing problems. Consumes more amount of fuel even when running in idle mode. No suitable for variable load like cars, trucks, cranes, etc. Much expensive as compared to normal engines. Careful design and materials selection due to immense heat rejected by the jet engines. Conclusion: Jet engines are highly efficient and have more power to weight ratio. Commercial aeroplanes utilize jet engines due to high fuel efficiency. Jet Engine With the knowledge of energy conversion processes, engines are developed that convert chemical energy of the fuel into mechanical energy. As the time passed, advanced engine technologies developed that utilized less fuel and gave more power as compared to the previous models. Internal combustion engines have less power to weight ratio. However, newer models of internal combustion engines have comparatively more power to weight ratio. Jet engines are efficient and have more power to weight ratio as compared to the any other type of engines. A jet engine is a gas turbine engine that is a type of internal combustion engine. Fuel and air is mixed and ignited inside the cavity of the engine. However, jet engines are different for other type of internal combustion engines, as they have no pistons. Jet engines have lesser moving parts as compared to the piston based internal combustion engine. The main parts of the jet engines or gas turbine engine are turbine, compressor, fuel ignition system and a connection rod that connects turbine and compressor. The compressor, ignition system (burner) and the turbines are the core of the jet engine. The word gas generator refers the core of the jet engines as hot gases are produced within the core of the jet engines. The compressor compresses the air inside the engine. The compressed air is mixed with fuel and ignited. Due to the ignition, the fuel burns rapidly in the presence of air and hot gases rush out of the engine through the turbine. The turbine rotates as the hot gases rush out of the engine due to the aerodynamic energy (Birch 2001, p.74). Turbine and compressor are connected with a same shaft. The rotation of the turbine rotates the compressor that compresses more air into the engine. Jet engine output is evaluated with respect to the thrust it produces. Each jet engine in the aircraft produces thrust that makes the aircraft to move forward (Soares, 2008, p.67). The motion in the aircraft verifies Newton’s third law that states, “For every action there is an equal and opposite reaction” (Holzner 2011, p.45). The thrust of the engine is in the backward direction that produces an opposite and equal amount of force in the airplane and airplane moves in the forward direction. Forward momentum allows the locomotive having jet engine to move in forward direction. Forward momentum depends on the net thrust. Net thrust of a jet engine makes the airplane or any other locomotive to move in the forward direction. However, in case when there is no forward momentum, the jet engine produces gross thrust. In case, when the airplane remains at rest and jet engine remains running, net thrust equals to gross thrust. While, when the airplane is moving forward, the gross thrust is more than the net thrust (Treager 1996, p.68). The four types of gas turbine engines are the turbojet, turbo fan, turbo propeller and after burning turbo jet (NASA 2008). Ramjet is also a type of jet engines. Most of the commercial airplanes have turbofan jet engines. Turbofan engines are highly efficient in terms of fuel economy, mass to thrust ratio and cost effectiveness. High bypass triple spool turbofan jet engines are common type of turbofan jet engines that are utilized in most commercial airplanes. Some military planes utilize the turbo propeller jet engines; however, common use of turbo propeller jet engines does not seem to be cost effective. The internal structure of the all the type of jet engines is same but there are some differences that makes then different. Turbo propeller jet engines have a propeller that is attached to the main rotor of the jet engine that drives turbine and compressor. In turbofan jet engines, fan with several aerodynamic blades attaches to the main rotor of the jet engine that drives the main rotor of the plane; however, the fan remain in a canopy that has a wide opening and a narrow end. The opening captures the air while the narrow opening generates output thrust. Turbo propeller jet engines have three to five blades, while turbofan jet engines have several blades with little width between them. Both the engines produce different type of noises. Turbofan planes produce high frequency noise due to the lower diameter allowed for thrust. Turbofan jet engines are highly efficient as compared to the turbo propeller jet engines. Turbofan jet engine consumes much less amount of fuel as compared to the turbo propeller jet engines to produce similar amount of thrust. Turbofan jet engines have higher thrust to mass ratio as compared to the turbo propeller jet engines (NASA: National Aeronautics and Space Administration, 2014). Turbojet engines are the simplest type of jet engines. Other types of jet engines evolved after turbojet engines. In the turbojet engines, air enters through the compressor. The multiple foils of the compressor increment the pressure of the air. After passing through each foil the pressure of the air rises. When the air reaches the burner compartment, it is under high pressure. At this stage, the burner mixes a small amount of fuel with the help of injectors and ignites the mixture of fuel and air. Under high pressure, the air and fuel mixture burns at a rapid rate and hot gases rust out of the engine through the turbine. The output thrust runs the turbine of the jet engine. The energy extracted at the turbine is used to run the compressor as the turbine and compressor are linked. However, at initial stage external energy is required to run the compressor of the engine (NASA: National Aeronautics and Space Administration, 2014). Both the turbofan and turbo propeller jet engines utilize the turbojet engines as the major component of the engines. Besides turbojet engine, fan is linked with the rotor of turbojet engine in the turbofan engines and propeller is linked with the turbojet engine in turbo propeller engines (NASA: National Aeronautics and Space Administration, 2014). Afterburning turbojet engines have an afterburner at the back of the turbine. Afterburning turbojet engines have the similar core as that of the turbojet engines. The major difference is the afterburner in the afterburning turbojet engines. The afterburner mixes the fuel directly with the exhaust of the core. Due to the high temperature of the hot gases coming out of the core, the fuel burns at a rapid rate. On the other hand, the exhaust has still a high amount of oxygen that helps in burning. The afterburner increases the amount of thrust. These types of engines are utilized in some military airplanes (NASA: National Aeronautics and Space Administration, 2014). Ramjets have no physical moving parts. Forward momentum is attained by burning the fuel inside the chamber of the engine. The hot gases rush out of the engines with immense speed. The immense speed of the hot gases, which are rushing out of the engine, makes the locomotive to move forward. Ramjets are utilized in rockets and missiles. Ramjets have high forward momentum but low fuel economy, as the fuel burns rapidly to move the locomotive. Turbo shaft jet engines do not utilize the thrust of the engine to move the locomotive. Turbo shaft jet engines utilize air only to burn fuel that rotate the rotor of the jet engine. As the rotor moves, it moves the shaft that is usually attached to a helicopter. The shaft is not directly attached to the rotor of the helicopter. A number of gears monitor the speed of the rotor of helicopter and couples it with the speed of the turbo shaft jet engines. The performance of the jet engine depends on external as well as internal factors. The external factors that influence the thrust of the jet engines are air velocity, air temperature and altitude. As the velocity of the air increases, the thrust of the jet engine also increases. Higher velocity of air promotes the more airflow inside the engine and thus the mass flow of air increases that increases the thrust (Cavcar 2004). Air temperature also influences the output thrust of the jet engines. As the air temperature rises, the total mass of airflow decreases due to the thermal expansion of air that changes volume of air. Air temperature is inversely proportional to the output thrust of the jet engines. At lower air temperature, the thrust of the jet engines increase (Cavcar 2004). Altitude also influences the thrust of the jet engines. As the altitude increases, the pressure of air decreases. Lower air pressure does not allow more air to enter the jet engine and the thrust of the jet engine decreases. In case of the airplanes, as the altitude increases the temperature of the air also decreases. Both the factors in combination make the jet engine to produce same amount of thrust all the time while flying (Cavcar 2004). Advantages and disadvantages of jet engines The major advantage of the jet engines is that these types of engines have great power to weight ratio. Power to weight ratio is the property that enhances the engines output efficiency. The engines have least weight of its own with respect to the power it generates. This property influences greatly in airplanes. Jet engines are comparatively much small as compared to the piston based internal combustion engines. Due to the small and compact features of the jet engines, theses engines require fewer parts as compared to the not vehicular engines. Jet engines are highly efficient is case when there is a constant load. In power generation units and airplanes, under constant load conditions, jet engines remain the first priority for the manufacturers (Brain, 2014). The major disadvantage of the jet engines is that these engines are highly expensive. Besides being expensive, jet engines rotate at magnificent speed and thus produce high frequency and high pitch sounds that becomes a reason for the temporary and permanent deafness, if the person remain exposed for long terms. Jet engines reject high amount of waste heat. Jet engines require special materials that can bear high amount of heat. On the other hand, careful designing of the jet engines also reduces the burden of the parts. Jet engines consumes massive amount of fuel even at idle operation or when they are not bearing any load. However, the fuel consumption during idle operation is lesser as compared to the normal operation mode. Due to this reason, jet engines are good for high rotating speed and constant load applications like power plants and airplanes but not goods for cars, trucks and cranes (Brain, 2014). Jet engines are highly efficient engines. In bigger commercial planes, the fuel cost per kilometre is the same as that of the normal passenger car. This is due to the highly efficient jet engines. Jet engines are extremely powerful and produce immense amount of thrust that reduces the time taken by the flight. Bibliography Birch, R. (2001). Gas turbine engines for pilots and mechanics. 1st ed. Englewood, Colo.: Jeppesen Sanderson. Brain, M. (2014). HowStuffWorks "Advantages and Disadvantages of Jet Engines". [online] HowStuffWorks. Available at: http://science.howstuffworks.com/transport/flight/modern/turbine2.htm [Accessed 27 May. 2014]. Cavcar, M. (2014). Jet Engines. 1st ed. [ebook] Eskisehir, Turkey: Anadolu University, School of Civil Aviation. Available at: http://home.anadolu.edu.tr/~mcavcar/common/Jetengine.pdf [Accessed 6 May. 2014]. Holzner, S. (2011). Physics I For Dummies. 1st ed. Hoboken: John Wiley & Sons. NASA: National Aeronautics and and Space Administration, (2014). Types of Gas Turbines. [online] Available at: https://www.grc.nasa.gov/www/k-12/airplane/trbtyp.html [Accessed 6 May. 2014]. Soares, C. (2008). Gas turbines. 1st ed. Amsterdan: Butterworth-Heinemann. Treager, I. (1996). Aircraft gas turbine engine technology. 2nd ed. New York: Gregg Division, McGraw-Hill. Read More