Gas Turbine Engine - Coursework Example

Running Header: Gas Turbine Engine Student’s Name: Instructor’s Name: Course Code: Date of Submission: Table of Contents Table of Contents 2 Abstract 3 Introduction 4 Main Body 6 Turbines Engines 6 History of Gas Turbine Engines 6 Parts and Working Principles of a Gas Turbine Engine 7 Types of Gas Turbine Engines 9 Types depending on Structure/Design 9 Types depending on the Application 10 Advantages of Gas Turbine Engines 15 Disadvantages of Gas Turbine Engines 16 Conclusion 16 References 17 Abstract All turbine engines apply the same principle when they are working. Gas turbine engines function through generation of thrust. Thrust depends on the mass of released products and velocity at which they are released. Gas turbine engines have three main areas or units; they include compressor, combustion region and turbine. Compressor unit compresses air entering the turbine increasing its pressure and velocity. The compressed air then moves to combustion region where it is helps the fuel to burn at extremely high pressure producing gas. The high pressure gas moves to the turbine section where its energy rotates the turbines. These turbines rotate the shaft producing the required thrust. The use of Gas turbine engines has been there for a long time. They have been used in cars, planes, navy ships and other areas that use engines like industrial plants. Gas Turbine engines have been developed and generated through several stages. Many people including engineers and scholars like Dr. Franz Stolze designed their own types of gas turbines. Others were developed by companies like Brown Boveri Company in Switzerland in 1939. All these had a main aim of developing a working and efficient gas turbine engine. They are several advantages and disadvantages associated with gas turbine engines. Power to weight ratio of gas turbine engines is exceptionally high compared to others. However, they are extremely expensive. Introduction Force that moves any aircraft through the air is referred to as thrust. Thrust force is generated by propulsion system or engines of the aircraft. Different thrusts are developed in different ways by different propulsion systems. However, all thrust is developed or generated through application of the third law of motion by Newton. It states that “every action has opposite and equal reaction”. A working fluid in any propulsion system is usually accelerated by the system itself and reaction to this acceleration ends up producing force or thrust on the system. According to thrust equation, amount of generated thrust depend on gas mass flow through the engine as well as gas exit velocity. Gas turbine is a resourceful source of propulsion or shaft power. It has an increasing number of uses that ranges from driving big and small engines. All parts of gas turbine engines have common parts although the sizes and shapes are different. Gas turbine is also referred as combustion turbine. It is a rotary engine which usually extracts energy from combustion gas flow. Gas turbine has an upstream compressor joined or coupled to a turbine downstream with a combustion chamber between them. Getting enough power or force that can move aircraft up is very much possible with gas turbine. Gas turbines are designed in such a way that they are able to generate enough thrust depending on the size and the intended purpose. There is added energy to the gas stream in the combustor area. Air and fuel mixture is ignited. Combustor’s high pressure environment, temperature is increased due to combustion of the fuel. This eventually increases fluid pressure in the space of fixed volume. The combustion products are then released through a nozzle to the turbines at incredibly high pressure and speed. This spins the turbines at extremely high speed and enough force to power tanks, trains, and aircraft. The engine’s motion of impulse is equivalent to mass of the fluid multiplied by the speed of mass emission (About.com, 2009). Are gas turbine engines effective among other types of engines and are they capable of producing recommendable amounts of power? I think they are. Main Body Turbines Engines Turbines are of different varieties. However, they apply the same principle but the materials being used varies. Materials may include wind, steam, water, and gas. Turbines driven by water are referred to as water turbines. Turbines are different from others because water is denser and slow moving than steam or gas. Turbines driven by steam are referred as steam turbines. Most of steam turbine plants use natural gas, oil, nuclear reactor or coal to generate steam. Turbines that are driven by wind are referred as wind turbines. They are also referred as wind mills because they use wind as their motive force. A gas turbine uses gas to turn the turbines through pressurized gas. Gas turbine engines produce their own gas through combustion of some fuels. When fuels combust, the heat that come out of it expands the surrounding air which in turn comes out at an extremely high speed. The high speed of air rotates the turbines (Marshall, 1998). History of Gas Turbine Engines Gas turbine engine concept started all the way from 150 AD. The engine invented was called Hero’s Engine. In 1500, another invention was Chimney Jack that was drawn by Leonardo DA Vinci. This was a turning roasting spit. Hot air rose from fire through fans series which turned roasting spit. Taqi al-Din invented steam turbine in 1551, this used to power a self-rotating spit. Giovanni Branca developed a stamping mill mainly due to steam jets that rotated turbine which rotated driven machinery in 1629. In 1678, Ferdinand Verbiest built a carriage model that relied on jet steam for power. An Englishman John Barber was given a patent in 1791 for the first true gas turbine. Barber’s invention had most elements that are found in present gas turbines. His turbine was mainly designed to power a carriage that was horseless. Dr. Franz Stolze designed a gas turbine engine in 1872 although it did not run on its own power. In 1895, a three 4-ton 100 kilowatt parson’s generator was used to power first electric lighting in the street within the city. These generators were installed in Cambridge power station. Norwegian man, Elling built first gas turbine in 1903; this turbine was able to produce even more power than it needed in running its own components. Using turbines and compressors it produced 11 hp. Sir Frank Whittle used Elling’s work later. In 1918, General Electric Ltd which is one of the current gas turbine manufacturers’ begun their gas turbine division. Dr. A. A. Griffith developed gas flow practical theory through passages in-to more formal theory of gas through the airfoils. Sir Frank Whittle patented gas turbine design for jet propulsion in 1930. However, his work relied on previous works in the same filed. His engine was successfully used in April 1937. Pateras de Pescara patented free-piston engine as a gas generator for gas turbines in 1934. Hans Von Ohain and Max Hahn developed their own patented design of engine in Germany in 1936; this was during the time when Sir Frank Whittle was developing his design in England. The first gas turbine engine for generation of power was developed in 1939 by Brown Boveri Company in Switzerland. Parts and Working Principles of a Gas Turbine Engine Gas turbine engine has three parts that include compressor, combustion region and turbine. Compressor compresses air that is incoming resulting to high pressure. Air is usually sucked in on compressor’s right side. Compressor is a cone-shaped cylinder that has small blades of the fan which are attached in rows. Air at normal pressure is forced through the stage of compression where its velocity and pressure rise considerably. In some cases, air pressure can rise even by a factor of 30. Air enters the combustion area at high pressure. Fuel injectors ring injects a steady stream of fuel. Fuel may be natural gas, kerosene, jet fuel, or propane. In Combustion area, fuel burns producing high velocity and high-pressure gas. This gas moves into turbine section where the energy is extracted from high-velocity and high-pressure gas that flows from the combustion chamber. This energy produces the thrust required to propel the movement of the shaft. Gas turbines are explained thermodynamically through Brayton cycle. In this case, air is compressed isentropically with combustion occurring at a pressure that is constant. Expansion at turbine takes place isentropically back to the initial pressure. In a real situation, turbulence and friction cause non-isentropic expansion, non-isentropic compression and loss of pressure at the intake of air. For Non-isentropic compression, any given overall pressure ratio, the temperature of compressor delivery is higher than that of the ideal temperature. The loss of pressure at the intake of air, combustor and exhaust reduces the available expansion in-order to provide useful work. For non-isentropic expansion: even if the temperatures of turbine drop necessary to drive, compressor is usually unaffected. The pressure ratio that is associated is usually greater; it decreases the available expansion so as to provide useful work. Higher temperature of combustion in all cyclic heat engines means greater efficiency. However, they are some limiting factors like the ability of ceramic, steel, nickel and other materials that make the engine be able to withstand pressure and heat. There are engineering aspects used in the process of trying to recover exhaust heat in order to avoid wastage. Some of the heat exchangers used are recuperators, they pass exhaust heat to the compressed air before combustion. Gas turbines are less complex mechanically as compared to internal combustion piston engines. In most cases, simple turbines have one moving part. This is shaft/compressor/turbine without counting fuel system. All the three parts turn as a single unit. There are usually two turbine sets. The first set drives compressor directly. At the final stage are vanes that are on a single set. The final stage of turbines with output shaft is separate free-wheeling unit. They spin without any connection from other parts of the engine. Hot gases blowing through turbine blades have enough energy to generate enough power that rotates turbine blades. Some turbines are complicated because they have multiple shafts with hundreds of turbine blades, combustors, heat exchangers, complex piping and movable stator blades. As the engine becomes smaller, there is a need to have higher rotation rate of shaft in order to maintain high speed. The higher the speed by turbine blade, the higher the pressure gained hence maximum produced power. This is usually independent of engine size (Marshall, 2001). Types of Gas Turbine Engines Types depending on Structure/Design Gas turbines engines have various varieties. Turbo-fan engines are gas turbine engines with a large fan at the front part of the engine. The shaft on the final turbine is connected on the fan at the front. Therefore, as the shaft rotates, it powers the fan. The shafts ride over each other concentrically. The main purpose of this fan is to increase air amounts entering the engine hence increased thrust of the engine. It increases air needed for combustion as well as the amount of air getting out or bypass air hence increased speed that provides higher thrust. Turboprop engine is in some aspect similar to turbofan except that it has a propeller at the front section instead of a fan. Output shaft is connected to a gearbox that reduces the speed. The propeller of the engine is turned by gearbox output. Types depending on the Application There are several types of gas turbines. They include jet and aero-derivates engines, amateur gas turbines, auxiliary power units, and gas turbines for industrial electric generation, turbo shaft engines, radial gas turbines, scale jet engines, micro-turbines, and gas turbines in vehicles among others. Aero-derivates and jet engines are optimized to generate thrust or force from the exhaust gases. They also produce thrust from ducted fans that are connected to the gas turbines. Turbojets are jet engines that produce thrust from direct impulse of exhaust gases. Turbofans are jet engines that produce thrust from ducted fan action. Many liquid propellant rockets use gas turbines. Turbo-pump is used to power gas turbine in order to permit the use of low pressure and light-weight tanks which saves substantial dry mass. Aero-derivates are mainly used to generate electric power mainly due to their ability to shut down, start up, and even handle changes in load more quickly than the industrial machines. Aero-derivates are as well used in the marine industry with the main purpose of reducing weight. Amateur gas turbines are increasingly being constructed using amateurs. The simplest type of self constructed gas turbine uses an automotive turbocharger being the main component. A combustion chamber is usually fabricated and plumbed between turbine sections and compressor sections. Auxiliary power units are small gas turbines that are designed for back up power of large machines like those inside an aircraft. They provide air that is compressed for ventilation of aircraft with appropriate design of compressor, power for starting up larger jet engines, and hydraulic and electric power. Electric generation industrial turbines usually differ from aero-derivative in that the bearings, frames and blades are heavier in terms of construction. Industrial gas turbines are of various sizes from complex systems to truck mounted plants. These turbines are extremely efficient; they are 60 percent efficient when gas turbine waste is recovered by a steam generator of heat recovery in order to power a conventional steam turbine mainly in a combined cycle configuration. Cogeneration configuration can as well be used; this is the use of exhaust to heat space and water. It also drives absorption chiller for refrigeration or cooling. These engines have enclosures and that protect both the operators from noise and the engine from elements. Gas turbine construction takes few months to construct. Their main advantage include their ability to turn on and off within minutes hence supplying power during the time of peak demand. Gas turbines are used as peaking power plant because they are less efficient than combined-cycle plants. They operate for several hours a day depending on the demand of electricity and capacity of generation in the region. A large single-cycle gas turbine is capable of producing 100 to 300 megawatts of power with thermal efficient of 35-40 percent. They are some single cycle turbines that have reached efficiency of 40 percent. These are the ones that use gas turbine exhaust heat to power a separate turbine driving yet a different electrical generator (Claire, 2008). Scale jet engines are also known as micro-jets or miniature gas turbines. This engine can produce a thrust of up to 22 Newton. Micro-turbines are other types of gas turbines; these are also referred to as micro-turbine, turbo-generator, and turbo alternators. Micro turbines are becoming prevalent for combined power and heat as well as distributed power applications. This is one of the assuring technologies for hybrid electric vehicles powering. Micro-turbines range from hand-held units that produce less than 1 kW to commercial sized systems which produce hundreds of Kilowatts. The technology of electric power switching eliminates the need of synchronizing generator with power grid. This allows integration of generator with turbine shaft. Micro-turbine systems are mainly preferred over reciprocating engine generators. This is because they have higher power to weight ration with low emissions and few moving parts. Micro-turbines are also designed with foil bearings as well as air-cooling, they operate without coolants, lubricating oil, or other materials that are hazardous. Micro-turbines are made in such a way that most of the waste heat is contained in high temperatures making it easier for it to be captured. This is different from that of reciprocating engines where waste heat is split between cooling and exhausts system. However, reciprocating engines respond quickly to changes with slightly higher efficient. The micro-turbine efficient is also increasing as more inventions continue to emerge. In most cases, micro-turbines lose more efficiency when at low-power levels as compared to reciprocating engines. Micro-turbines use commercial fuels like natural gas, kerosene, gasoline, propane, diesel, biogas, and biodiesel among others. Designs of micro-turbine have single stage radial compressor, recuperator and a single radial turbine. It is usually difficult to design and even manufacture recuperators. This is generally because they function under different temperatures and pressures. The exhaust heat is used to heat water, heat space or for absorption chillers. Typical micro-turbine has an efficient of 25 to 35 percent. However, efficiencies of more than 80 percent can be achieved if power and heat cogeneration system is used. Gas turbines in most cases are internal combustion engines. However, it is possible to have an external combustion gas turbine. External combustion is mainly used for the purpose of pulverized coal use or other biomass that are finely ground like sawdust being fuels. Indirect systems have a heat exchanger that is used to clean air in the process of eliminating combustion products travelling via power turbines. Indirect external combustion systems have lower thermal efficiency; however the blades of turbines are not subjected to products of combustion. This gives room for the use of cheaper or lower quality fuels. Gas turbines are used in locomotives, tanks, ships, helicopters as well as on buses, motorcycles and cars. Gas turbines are used in turboprops and jets for propulsion. This is mainly due to their capability of high altitude superior performance when compared with piston engines. Another advantage is the power to weight ratio which is of enormous importance to those jets. Gas turbines in most cases offer an engine that is high powered, light and with extremely small package. However, they are not efficient and responsive as small piston engines. This is mainly in terms of a wide range of powers and revolution per minutes needed in vehicle application. Production of turbines has been expensive when compared to piston engines. This is mainly due to mass production of piston engines in mass quantities. The only closely mass produced turbine is turbo-charger. Gas turbine powered automobiles experiments have been conducted. One of the largest experiments was done by Chrysler. There are also some interests in turbine engine use for hybrid electric cars. British car manufacturers Rover Chief engineer Maurice Wilks and designer F.R. Bell, designed a gas turbine engine for powering a car in 1950. Its top speed was 87mph or 140 km/h with a turbine speed of 50,000 (rpm) during the test. Chrysler (American car manufacturer) demonstrated a variety of prototype gas turbine cars. This was from early 1950s to early 1980s. Fifty Chrysler Turbine Cars were built in 1963 where trial was conducted for these gas turbine powered cars. Rotating recuperator was employed in those turbines which increased efficiency significantly. Several gas turbine cars were demonstrated by Toyota. They included Century gas turbine in 1975 with Sports 800 Gas Turbine demonstrated in 1979. GTV was the last turbine car to be demonstrated in 1985 by Toyota. In 1977, the GT24 engine was demonstrated although it was not in a vehicle. Volvo launched the Volvo Environmental concept car in 1990s which was powered by gas turbine. General motors introduced first commercial hybrid vehicle that was powered by a gas turbine in 1993. BRM Formula One and Rover teams joined together in production of a gas turbine powered coupe referred as Rover-BRM. Trace car entered the race in 1963 referred as 24 Hours of Le Mans. It was driven by Richie Ginther and Graham Hill. Its average speed was 173 km/hr or 107.8 mph with a top speed of 229 km/hr or 142 mph. in 1968, Mckee engineering and Howmet Corporation were joined together by American Ray Heppen-stall in developing gas turbine sports car of their own. Howmet TX ran several European and American events that included two wins. In 1968, it took part in24 Hours of Le Mans race. The use of Continental gas turbines set a record of 6 FIA land records of speed for cars that were turbine driven (Gennady and Haydn, 2004). Arrival of capstone Micro-turbine eventually led to designing of hybrid buses at Tennessee in 1999. It started with HEV-1 by AVS. This was followed by ISE and Ebus Research in California and later in Design-Line Corporation in New Zealand. The successful bus designs by Design-line are now operating in 6 countries with more than 30 buses. Several buses are being taken to New York City and Baltimore. In 2000, first turbine engine motorcycle appeared. These were Rolls-Royce Allison model 250 with turbo engine. It produced 380 bhp (283 kW). Its speed was highest as it tested up-to 227 mph or 365 km/hr. it is one of the most powerful motorcycle and subsequently the most expensive. Bombardier’s Jet train is one of the recent locomotives being powered by gas turbines. It was in 1954 when first gas turbine was used in an armored fighting vehicle. C.A. Parsons & Co. developed, installed and even trialed in a conqueror tank of British. It is since then that gas turbines have been used especially in U.S. M1 Abrams tanks and Soviet/Russian T-80s. They are smaller and lighter than diesel engines. However, they are less efficient in terms of fuel especially at idle as they require more fuel in order to achieve same range of combat. This problem was solved through the installation of secondary generators or battery packs that power system of the tank when it is stationery. Because of their sensitivity to fine sand and dust, air filters should be changed regularly when operating in deserts (Tony, 2009). Gas turbines are also used in naval vessels. Their power-to-weight ratio is extremely high. This makes them to accelerate quickly with high ability to get underwater fast. Royal Navy’s Motor Gun Boat was the first gas turbine naval vessel in 1947. Beryl engine was developed by Metropolitan Vickers where it was equipped F2/3 jet engine with a power engine. After a successful test, Fast Patrol Boats Bold pathfinder and bold pathfinder that were built in 1953 were first gas turbine ships. Royal Navy’s Type 81 was the first gas turbine ship that was large scaled. U.S. first gas turbine ships were USCGC Hamilton that was commissioned in 1967. First Navy’s amphibious assault ship will be Wasp-Class amphibious assault ship that will be powered by gas turbine. Presence of sea salt in the air makes marine gas turbine work in the atmosphere that is corrosive. Advantages of Gas Turbine Engines Compared to reciprocating engines, gas turbines have the power to weight ratio that is extremely high. They are smaller compared to reciprocating engines with the same rating in power. Gas turbine engines have less vibration when compared to reciprocating engines, they as well move in the same direction. Gas turbine’s moving parts are fewer than those of reciprocating engines. They also operate at low pressures with high-operating speeds. The lubrication consumption and cost is low. Disadvantages of Gas Turbine Engines However, they are some disadvantages associated with gas turbine. They are in most cases incredibly costly. During the idle time, they are less efficient when compared to reciprocating engines. Gas turbines take longer to startup as compared to reciprocating engines. Gas turbine engine respond extremely slowly to power demand changes as compared to reciprocating engines which respond extremely rapidly. Conclusion Theoretically, gas turbines are easier to maintain and more reliable than piston engine. This is mainly because they are easier to construct and has fewer moving parts. However, most turbine parts experience a higher wear rate mainly due to their higher working speeds. The blades of turbine are extremely sensitive to fine sand and dust. Gas turbine technology has advanced and evolved steadily since its initiation. There is ongoing active research towards producing a gas turbine smaller in size. Computer designs like finite element analysis and CFD have allowed higher temperatures and compression ratios, better engine cooling, and combustion that is more efficient. Gas turbine engines are one of the best engines that I can recommend. Their advantage outweighs disadvantages at a great extent. Even though their efficiency is not extremely high, they are effective engines in almost all applications. Nevertheless, there is need for further research and development in order to increase efficiency. References About.com. (2009). How a Jet Engine Works. Retrieved April 6, 2010, from http://inventors.about.com/library/inventors/blhowajetengineworks.htm Claire, S. (2008). Gas turbines: a handbook of air, land, and sea applications. California: Butterworth-Heinemann. Gennady, G. & Haydn, A. (2004). Dynamic modeling of gas turbines: Identification, simulation, condition monitoring, and optimal control. Michigan: Springer. Marshall B. (1998). How Gas Turbine Engine Work. Retrieved April 6, 2010, from http://science.howstuffworks.com/turbine.htm Marshall B. (2001). How Gas Turbine Work. Retrieved April 6, 2010, from http://www.massengineers.com/Documents/howgasturbinework.htm Tony, G. (2009). Gas Turbine Handbook: principles and Practice, Fourth Edition. London: The Fairmont Press, Inc. Read More

All parts of gas turbine engines have common parts although the sizes and shapes are different. Gas turbine is also referred as combustion turbine. It is a rotary engine which usually extracts energy from combustion gas flow. Gas turbine has an upstream compressor joined or coupled to a turbine downstream with a combustion chamber between them. Getting enough power or force that can move aircraft up is very much possible with gas turbine. Gas turbines are designed in such a way that they are able to generate enough thrust depending on the size and the intended purpose.

There is added energy to the gas stream in the combustor area. Air and fuel mixture is ignited. Combustor’s high pressure environment, temperature is increased due to combustion of the fuel. This eventually increases fluid pressure in the space of fixed volume. The combustion products are then released through a nozzle to the turbines at incredibly high pressure and speed. This spins the turbines at extremely high speed and enough force to power tanks, trains, and aircraft. The engine’s motion of impulse is equivalent to mass of the fluid multiplied by the speed of mass emission (About.com, 2009).

Are gas turbine engines effective among other types of engines and are they capable of producing recommendable amounts of power? I think they are. Main Body Turbines Engines Turbines are of different varieties. However, they apply the same principle but the materials being used varies. Materials may include wind, steam, water, and gas. Turbines driven by water are referred to as water turbines. Turbines are different from others because water is denser and slow moving than steam or gas. Turbines driven by steam are referred as steam turbines.

Most of steam turbine plants use natural gas, oil, nuclear reactor or coal to generate steam. Turbines that are driven by wind are referred as wind turbines. They are also referred as wind mills because they use wind as their motive force. A gas turbine uses gas to turn the turbines through pressurized gas. Gas turbine engines produce their own gas through combustion of some fuels. When fuels combust, the heat that come out of it expands the surrounding air which in turn comes out at an extremely high speed.

The high speed of air rotates the turbines (Marshall, 1998). History of Gas Turbine Engines Gas turbine engine concept started all the way from 150 AD. The engine invented was called Hero’s Engine. In 1500, another invention was Chimney Jack that was drawn by Leonardo DA Vinci. This was a turning roasting spit. Hot air rose from fire through fans series which turned roasting spit. Taqi al-Din invented steam turbine in 1551, this used to power a self-rotating spit. Giovanni Branca developed a stamping mill mainly due to steam jets that rotated turbine which rotated driven machinery in 1629.

In 1678, Ferdinand Verbiest built a carriage model that relied on jet steam for power. An Englishman John Barber was given a patent in 1791 for the first true gas turbine. Barber’s invention had most elements that are found in present gas turbines. His turbine was mainly designed to power a carriage that was horseless. Dr. Franz Stolze designed a gas turbine engine in 1872 although it did not run on its own power. In 1895, a three 4-ton 100 kilowatt parson’s generator was used to power first electric lighting in the street within the city.

These generators were installed in Cambridge power station. Norwegian man, Elling built first gas turbine in 1903; this turbine was able to produce even more power than it needed in running its own components. Using turbines and compressors it produced 11 hp. Sir Frank Whittle used Elling’s work later. In 1918, General Electric Ltd which is one of the current gas turbine manufacturers’ begun their gas turbine division. Dr. A. A. Griffith developed gas flow practical theory through passages in-to more formal theory of gas through the airfoils.

Sir Frank Whittle patented gas turbine design for jet propulsion in 1930.

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