Turbines

Outline Introduction Classification of turbine Gas turbine classification Advantages Disadvantages Open Gas Turbine Cycle Closed Cycle Gas Turbine

Introduction A turbine is defined as a device which draws energy from a fluid moving at a high speed and converts that energy into work. The purpose of turbines is basically to produce electricity and to propel various machinery and objects via the mechanical energy produced. A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and water wheels. Every turbine has a one basic principle that is a moving fluid which can be water, steam, wind or gas is made to run over blades at a high speed, the blades induced by the moving fluid start rotating and as a result they start the rotor engine attached to the device which is responsible for converting the energy into work. Turbines came into being after the industrial revolution when the entire world changed its shape. Almost the entire electricity of the world is produced by turbines; however the source of energy may vary. The first turbines to be used were the steam turbines but now on the basis of the fluid from which energy is extracted there are four major types of turbines:

Types Of Turbines Steam turbines Water turbines Wind turbines Gas turbines

Steam Turbine

Steam turbines were the first turbines ever produced by man. These turbines are composed of shaft blades and a rotor engine. The steam which is produced by the burning of coal, oil or from nuclear reactor is made to pass through blades which spin at a very high speed to drive the generator which produces energy. The principle on which it works is that the thermal energy which is extracted from the steam is converted into mechanical energy. Although officially steam engines were put into use by the efforts of the English engineer Charles Algernon Parsons in 1884, it believed that he was not the first person who came up with the idea. The concept of converting the energy produced by fast moving steam into work was first given in the first century by a Greek mathematician. However since there were not many resources at that time the concept was not given much of a thought. For more than a century steam turbines were majorly used for production of electricity but later other types of turbines took over. Because of the fact that they use up the fossil fuels which are now are being diminished they are not preferred today for the making of electricity for masses.

Water Turbine

Water turbines work on the same principle as the steam turbines but the difference is that they use water instead of steam. The water used by these turbines comes from lakes and rivers. Dams which are built in these huge water bodies store the water at one end, at the other end they posses hydraulic turbines which posses a shaft bearing vertical blades and a generator which produces hydroelectric power which is in turn used as electricity. Water turbines today are the major source of electricity all over the world. Nearly 70% of the world uses hydroelectric power to produce electricity. They are more preferable than the steam turbines as they do not waste up the fossil fuels. The first water turbines were built in Niagara falls at the end of the 19th century but their use became massive at the mid of the 20th century with the fall of industries.

Wind Turbines

Wind turbines use up the moving wind to produce electricity. These turbines might not be as popular as water and steam turbines but in many parts of the world like in Scotland and some parts of America this turbine is used to produce electricity. Long egg beater- like shafts, possessing bow shaped blades, are placed high in the sky. These blades move with the moving wind to produce electricity. Producing electricity from wind may sound a good option as wind is a resource which can never end; however this process has huge restrictions as wind is as reliable as water. It can only be applicable in parts of the world where wind moves fast continuously.

Gas Turbine

Gas turbines use up high pressure gas to produce energy. These turbines are not used for producing electricity but they are used to propel jet engines. Gas turbines are the latest types of turbines. Their structure is advanced but the principle is same.

How to work turbine Nacelle Fan Low pressure Compressor High pressure compressor Combustion chamber High pressure turbine Low pressure turbine Core nozzle Fan nozzle

Gas turbine classification According to the path of the working substance Open Cycle Gas Turbine Closed Cycle Gas Turbine According to the process of heat absorption Constant pr. Gas turbine Constant vol. Gas turbine Marin turbine, Air craft turbine, power-plant turbine Single stage or multi stage , Single shaft or multi shaft

Advantages: There are two big advantages: Gas turbine engines have a great power-to-weight ratio compared to reciprocating engines.  That is, the amount of power you get out of the engine compared to the weight of the engine itself is very good. Gas turbine engines are also smaller than their reciprocating counterparts of the same power. The Gas Turbine Plant is simple in Design and Construction.It has few Reciprocating Parts and is lighter in weight. The Gas Turbine is quite useful in the regions where due to scarcity it is not possible to supply water in abundance for raising steam.

Disadvantages: The main disadvantage of gas turbines is that, compared to a reciprocating engine of the same size, they are expensive. Because they spin at such high speeds and because of the high operating temperatures, designing and manufacturing gas turbines is a tough problem from both the engineering and materials standpoint. Gas turbines also tend to use more fuel when they are idling and they prefer a constant load rather than a fluctuating load. That makes gas turbines great for things like trans-continental jet aircraft and power plants.

Open Cycle Gas Turbine Open gas turbine cycle is the most basic gas turbine unit. The working fluid does not circulate through the system, therefore it is not a true cycle. It consists of a compressor, a combustion chamber and a gas turbine. The compressor and the gas turbine are mounted on the same shaft. The compressor unit is either centrifugal or axial flow type. The working fluid goes through the following processes: 1-2 irreversible but approximately adiabatic compression 2-3 constant pressure heat supply in the combustion chamber 3-4 irreversible but approximately adiabatic expansion of combustion gases

Closed Cycle Gas Turbine A closed-cycle gas turbine is a turbine that uses a gas (e.g. air, helium, etc.) for the working medium as part of a closed system (thermodynamics). Heat is supplied from an external source. Such recirculating turbines follow the Brayton cycle. Historically, they found most use as external combustion engines "with fuels such as bituminous coal, brown coal and blast furnace gas" but were superseded by open cycle gas turbines using clean-burning fuels (e.g. "gas or light oil"), especially in highly-efficient combined cycle systems. Closed-cycle gas turbines hold promise for use with future high temperature solar and nuclear power generation. They have also been proposed as a technology for use in long-term space exploration. Super-critical carbon dioxide closed-cycle gas turbines are under development; "The main advantage of the super-critical CO2 cycle is comparable efficiency with the helium Brayton cycle at significantly lower temperature (550°C vs. 850°C), but higher pressure (20 MPa vs. 8 MPa)."

Thank you. Presented By…!! RUPESH S. BARWALIYA Guide By…!! B. L. THAKOR