Gas turbine and its classification
0 likes2,456 views
A gas turbine is a device that converts hot gases into mechanical work, operating primarily on the Joule or Brayton cycle which includes processes of compression and expansion. Compared to steam turbines, gas turbines are easier to start, require less space, and do not depend on water supply, though they operate at higher temperatures. Gas turbines can be classified into open and closed cycle types, with various applications including electric power generation and propulsion in vehicles.
Gas turbine and its classification
- 1. Gas Turbine What is a Gas turbine? A gas turbine is a contrivance in which hot gases are to be passed over the turbine blade in order to produce mechanical work. Working fluid of Gas turbine: Air
- 2. Diagram of A gas turbine Figure-1: Schematic Diagram of Gas turbine Plant
- 3. Cycle on which Gas turbine operates Gas turbine operates on Joule or Brayton Cycle. Brayton cycle consists of Two constant pressure processes (H.A & H.R). Two isentropic processes (Compression & Expansion).
- 4. P-V & T-S Diagram
- 5. Working principle: In a gas turbine, first of all, the air is obtained from the atmosphere and compressed in an air compressor. The compressed air is then passed into the combustion chamber, where heat is added. The hot air is then made to flow over the moving blade of the gas turbine, which imparts rotational motion to the runner. Ultimately mechanical work is produced. A major part of the work developed by the gas turbine is to be supplied to the compressor.
- 6. Comparison with Steam turbine: Gas turbine Steam Turbine Starting of GT is easy and quick.(8-12 mins) Starting is difficult and takes long time. Weight power ratio is low.(15 kg/hp) Weight power ratio is high.(39 kg/hp) It requires less space for installation. It requires more space for installation. Omission of boiler, condenser and other auxiliaries in GT leads to the simplification of the system. Involving boiler, condenser etc. so it is not simple. It can be stooped within few seconds after cut off the fuel supply. It requires more time to stop. A gas turbine does not depend on water supply. Steam turbine obviously depend on water supply. Max. Temperature is limited to 1000K. Max. temperature is limited to 750K.
- 7. Applications of Gas Turbine • Generation of Electric power. • Turbojet and turbo propellers engines. • Marine engines • Railway engines • Automobile
- 8. 1. According to the path of working substance a) Open cycle gas turbine. b) Closed cycle gas turbine. 2. According to the process of heat absorption. a) Constant pressure gas turbine. b) Constant volume gas turbine. Classification of Gas turbines
- 9. Open cycle gas turbine In open cycle gas turbine, atmospheric air is taken into the compressor where air is compressed. Then compressed air is delivered to the combustion chamber in order to add heat. The hot charge is then passed over the blade of turbine in which gases are expanded and hence work is produced. The charge coming out from the turbine is exhausted to the atmosphere. Fresh air is taken for repeat the process.
- 10. Closed cycle gas turbine In closed cycle gas turbine, same working fluid is used again and again (i.e The charge coming out from turbine is cooled in a cooling chamber or in a heat exchanger instead of exhaust). Here, compressed air is not delivered to the combustion chamber. Heat is added to the air in a heat exchanger. In closed cycle gas turbine, air is not mixed with the product of combustion.
- 11. Modification or Improvement of Gas turbine 1. By Intercooling 2. By Reheating 3. By Regeneration