Gas turbine power plant

Gas turbine power plant

1. Course Instructor: Md. Tarek Ur Rahman Erin Sr. Lecturer, MTE, WUB Gas Turbine Power plant Course Title: Power Plant Engineering; Course Code : MTE 905 WEEK 05

2. Gas Turbine Power Plant

3. GAS TURBINES Invented in 1930 by Frank Whittle Patented in 1934 First used for aircraft propulsion in 1942 on Me262 by Germans during second world war Currently most of the aircrafts and ships use GT engines Used for power generation Manufacturers: General Electric, Pratt &Whitney, SNECMA, Rolls Royce, Honeywell, Siemens – Westinghouse, Alstom Indian take: Kaveri Engine by GTRE (DRDO)

4. Gas turbine power plant Gas turbine: Working principle : Air is compressed(squeezed) to high pressure by a fan-like device called the compressor. Then fuel and compressed air are mixed in a combustion chamber and ignited. Hot gases are given off, which spin the turbine wheels. Most of the turbine’s power runs the compressor. Part of it drives the generator/machinery.

5. Gas turbine power plant… Gas turbine: Description: Gas turbines burn fuels such as oil, nature gas and pulverised(powdered) coal. Instead of using the heat to produce steam, as in steam turbines, gas turbines use the hot gases directly to turn the turbine blades. Gas turbines have three main parts: Air compressor Combustion chamber Turbine

6. Gas turbine power plant… Gas turbine: Air compressor: The air compressor and turbine are mounted at either end on a common horizontal axle(shaft), with the combustion chamber between them. Gas turbines are not self starting. A starting motor initially drives the compressor till the first combustion of fuel takes place, later, part of the turbine’s power runs the compressor. The air compressor sucks in air and compresses it, thereby increasing its pressure.

7. Gas turbine power plant… Gas turbine: Combustion chamber: In the combustion chamber, the compressed air combines with fuel and the resulting mixture is burnt. The greater the pressure of air, the better the fuel air mixture burns. Modern gas turbines usually use liquid fuel, but they may also use gaseous fuel, natural gas or gas produced artificially by gasification of a solid fuel. Note : The combination of air compressor and combustion chamber is called as gas generator.

8. Gas turbine power plant… Gas turbine: Turbine: The burning gases expand rapidly and rush into the turbine, where they cause the turbine wheels to rotate. Hot gases move through a multistage gas turbine. Like in steam turbine, the gas turbine also has fixed(stationary) and moving(rotor) blades. The stationary blades guide the moving gases to the rotor blades and adjust its velocity. The shaft of the turbine is coupled to a generator or machinery to drive it.

9. Gas turbine power plant… Applications of gas turbine: Gas turbines are used to drive pumps, compressors and high speed cars. Used in aircraft and ships for their propulsion. They are not suitable for automobiles because of their very high speeds. Power generation(used for peak load and as stand-by unit). Note : Gas t ur b in e s run a t e v e n h i g h e r t e m pera t ures th a n s t eam tu r b i nes, the temperature may be as high as 1100 – 1260 C. The thermal efficiency of gas turbine made of metal components do not exceed 36%. Research is underway to use ceramic components at turbine inlet temperature of 1350 C or more, and reach thermal efficiencies over 40% in a 300 kW unit.

10. Layout of a gas turbine power plant

11. Layout of gas turbine power plant… Starting motor: Gas turbines are not self starting. They require a starting motor to first bring the turbine to the minimum speed called coming –in speed, for this purpose a starting motor is required. Low pressure compressor(LPC): The purpose of the compressor is to compress the air. Air from the atmosphere is drawn into the LPC and is compressed. Intercooler: The air after compression in the LPC is hot. It is cooled by the intercooler. The i nt e r c o o l er i s c i r c ula t ed w i t h cooling water.

12. Layout of gas turbine power plant… High pressure compressor(HPC): The air from the intercooler enters the HPC where it is further compressed to a high pressure. The compressed air passes through a regenerator. Regenerator(Heat exchanger): The air entering the combustion cha m ber(C C ) for c o m b u st i on must be hot. The heat from the exhaust gases is picked up by the co m p r e s s e d a i r e nt e r i ng the combustion chamber. Combustion chamber: The fuel(natural gas, pulverized coal, kerosene or gasoline) is injected into the combustion chamber. The fuel gets ignited because of the compressed air. The fuel along with the compressed air is ignited sometimes with a spark plug.

13. Layout of gas turbine power plant… High pressure turbine (HPT): In the beginning the starting motor runs the compressor shaft. The hot gases(products of combustion) expands through the high pressure turbine. It is important to note that when the HPT shaft rotates it infact drives the compressor shaft which is coupled to it. Now the HPT runs the compressor and the starting motor is stopped. Note : Abo u t 6 6 % de v e l o p e d by o f the pow e r t he gas t ur b ine power p l a nt i s us e d t o r un t h e compressor. Only 34% of the power developed by the plant is used to generate electric power.

14. Layout of gas turbine power plant… Low pressure turbine (LPT): The purpose of the LPT is to produce electric power. The shaft of the LPT is directly coupled with the generator for producing electricity. co m b u s t i o n ) aft e r l e a v i n g The hot gas e s ( p r oducts of the HPT is again sent to a combustion cha m ber w h e re i t f ur t h e r undergoes combustion. The exhaust gases after leaving the L PT p a sses t hr o ugh the r e ge n e ra t or exhausted bef o re be i ng t h r ough t he c h i m ney into the atmosphere. The heat from the hot gases is used t o p r e heat the a i r e n t er i ng the combustion chamber. This preheating of the air improves the efficiency of the combustion chamber.

15. Gas turbine power plant… Advantages of gas turbine power plant : Storage of fuel requires less area and handling is easy. The cost of maintenance is less. It is simple in construction. There is no need for boiler, condenser and other accessories as in the case of steam power plants. Cheaper fuel such as kerosene , paraffin, benzene and powdered coal can be used which are cheaper than petrol and diesel. Gas turbine plants can be used in water scarcity areas. Less pollution and less water is required. Disadvantages of gas turbine power plant : 66% of the power developed is used to drive the compressor. Therefore the gas turbine unit has a low thermal efficiency. The running speed of gas turbine is in the range of (40,000 to 100,000 rpm) and the operating temperature is as high as 1100 – 1260 C. For this reason special metals and alloys have to be used for the various parts of the turbine. High frequency noise from the compressor is objectionable.

16. Compared to Steam-Turbine , Gas Turbine offers : Greater Power for a given size and weight, High Reliability , Long Life , More Convenient Operation . Engine Start-up Time reduced from 4 hrs to less than 2 min …!! Gas Turbine Power Plants – Advantages

17. Thermodynamic Cycles Applications of Thermodynamics Power Ge n erat i on Refrigeration Power Cycles Refrigeration Cycles Engines Refrigerators / Heat Pumps / Devices / produce Net Systems used Power Output . to A.C. Devices / Systems used to produce Refrigeration Effect External H eat i s s upp l ied t o t h e W o r k i ng F lu i d from an external source such as a Furnace / Geothermal Well / Nuclear Reactor, etc. Internal Heat is supplied to the Working Fluid by burning the Fuel within the System Boundaries.

18. Introduction Thermodynamics Cycles Gas Cycles Vapour Cycles Working Fluid remains in Gaseous Phase throughout the Cycle. Working Fluid exists in Vapor Phase during part of the Cycle, and in liquid phase during remaining pa r t

19. Thermodynamics Cycles Closed Cycles Open Cycles Working Fluid returns to Initial State at the end of the cycle, and is Rec i r culate d . Working Fluid is Renewed at the end of each cycle, and thus us Non- Rec i r culate d . Introduction

20. Made up of Four Internally Reversible processes: Brayton Closed Cycle – Analysis 1 -2 2 -3 3-4 4-1 Isentropic Compression (in a Compressor ) Constant-Pressure Heat Addition Isentropic Expansion (in a Turbine ) Constant-Pressure Hat Rejection

21. Brayton Closed Cycle – Analysis Thermal Efficiency of Ideal Brayton Cycle : 1 1 1 th , Brayton r p 2 1 p P r P w h ere;

22. Gas Turbine Power Plants – Applications Two Major Application Areas : Aircraft Propulsion Electric Power Generation. Electric Power Generation Aircraft Propulsion

23. Regenerative Brayton Cycle For the Brayton cycle, the turbine exhaust temperature is greater than the compressor exit temperature. Therefore, a heat exchanger can be placed between the hot gases leaving the turbine and the cooler gases leaving the compressor. This heat exchanger is called a regenerator or recuperator..

24. Gas Turbine Cycle – Intercooling Three Internally Reversible processes: 1 -c Isentropic Compression, till Pr. is P i c -d Constant-Pressure Cooling, ↓ from T c to T d d -2 Isentropic Compression , State 2 .

25. Gas Turbine Cycle – Reheat After expansion from State 3 to State a in the first turbine, the gas is Reheated at Constant Pressure from State a to State b . The expansion is then completed in the second turbine from State b to State 4 .

26. Gas Turbine Cycle – Intercooling + Reheat + Regenerator

27. Brayton with Intercooling, Reheat, & Regeneration

28. Thank You