GAS TURBINE POWER PLANTS BY ABHISHIEK PAWAR 0815002

GAS TURBINE POWER PLANTS BY ABHISHIEK PAWAR - 0815002 ANIL NAIR - 0815012 ANIRUDDHA SAWANT - 0815013 ANJALI DESAI - 0815014

INTRODUCTION: • A generating station which employs gas turbine as the prime mover for the generation of electrical energy is known as a gas turbine power plant. • In a gas turnine power plant, air is used as the working fluid. The air is compressed by the compressor is lead to the combustion chamber where heat is added to air, thus raising its temperature. Heat is added to the compressed air either by burning fuel in the chamber or by the use of air heaters. The hot and high pressure air from the combustion chamber is then passed to the gas turbine where it expands and does the mechanical work. The gas turbine drives the alternator which converts the mechanical energy into electrical energy.

SIMPLE GAS TURBINE CYCLE

AIR STANDARD BRAYTON CYCLE 1 - 2 Isentropic compression 2 - 3 Constant pressure heat addition 3 - 4 Isentropic expansion 4 - 1 Constant pressure heat removal P-V Diagram T-S Diagram

SIMPLE GAS TURBINE LAYOUT FRONT VIEW TOP VIEW

FUELS: • One further advantage of gas turbines is their fuel flexibility. They can be adapted to use almost any flammable gas or light distillate petroleum products such as gasoline (petrol), diesel and kerosene (paraffin) which happen to be available locally, though natural gas is the most commonly used fuel. Crude and other heavy oils and can also be used to fuel gas turbines if they are first heated to reduce their viscosity to a level suitable for burning in the turbine combustion chambers.

ADVANTAGES: • It is simple in design as compared to steam power station since no boilers and their auxiliaries are required • it is much smaller in size as compared to steam power station of same capacity. This is expected since gas turbine power plant doesnot require boiler, feed water arrangements etc • The initial and operating costs are much lower than that of equivalent steam power station • It requires comparatively less water as no condenser is used • The maintenance charges are quite small • Gas turbines are much simpler in construction and operation than steam turbines • It can be started quickly from cold conditions • There are no standby losses. However, in a steam power station, these losses occur because boiler is kept in operation even when the steam turbine is supplying no load

DISADVANTAGES: • There is a problem for starting the unit. It is because before starting the turbine, the compressor has to be operated for which power is required from some external source. However once the unit starts, the external power is not needed as the turbine itself supplies necessary power to the compressor. • Since a greater part of the power developed by the turbine is used in driving the compressor, the net output is low • The overall efficiency of such plants is low(about 20%) because of the exhaust gases from the turbine contain sufficient heat • The temperature of combustion chamber is quite high(3000 deg. F)so that its life is comparatively reduced

GAS POWER PLANTS IN INDIA

THE MAIN COMPONENTS OF A GAS TURBINE POWER PLANT • • COMPRESSOR TURBINE HEAT EXCHANGER INTERCOOLER

COMPRESSOR • The compressor sucks in air form the atmosphere and compresses it to pressures in the range of 15 to 20 bar. The compressor consists of a number of rows of blades mounted on a shaft. This is something like a series of fans placed one after the other. The pressurized air from the first row is further pressurized in the second row and so on. Stationary vanes between each of the blade rows guide the air flow from one section to the next section. The shaft is connected and rotates along with the main gas turbine.

TURBINE • The turbine does the main work of energy conversion. The turbine portion also consists of rows of blades fixed to the shaft. Stationary guide vanes direct the gases to the next set of blades. The kinetic energy of the hot gases impacting on the blades rotates the blades and the shaft. The blades and vanes are made of special alloys and designs that can withstand the very high temperature gas. The exhaust gases then exit to exhaust system through the diffuser. The gas temperature leaving the Turbine is in the range of 500 to 550 °C.

HEAT EXCHANGER • Two kinds of heat exchangers are used: • a) Recuperators and b)Regenerators • In recuperative type, the air and hot gases are made to flow in counter direction as the effect of counter-flow gives high average temperature difference causing the higher heat flow.

HEAT EXCHANGER • The regenerator type heat exchanger consists of a heat conducting member which is exposed alternately to the hot exhaust gases and the cooler compressed air. It absorbs heat from hot gases and gives it up when exposed to the air. The heat capacity member is made of a metallic mesh or matrix which is rotated slowly (40 -60 rpm) and continuously exposed to hot and cold air.

(iii)Combustion Chamber The air at high pressure from the compressor is led to the combustion chamber via the regenerator. In the combustion chamber, heat is added to the air by burning oil. The oil is injected through the burner into the chamber at high pressure ensure atomization of oil and its through mixing with air. The result is that the chamber attains a very high temperature(about 3000 F). The combustion gases are suitably cooled to 1300 F to 1500 F then delivered to gas turbine.

INTERCOOLER • An intercooler is generally used in a gas turbine power plant when the pressure ratio used is sufficiently large and the compression is completed with two or more stages • A cross flow type intercooler is generally preferred for effective heat transfer

URAN GAS TURBINE POWER PLANT

• It is the first gas-run electricity plant in asia • This power station has got first air cooled condensor in asia. • It consists of nine units overall • UNIT 1 was commisioned in February 1982 • The plant can be brought to full speed in 3 minutes and at full load in 8 minutes

Total Capacity of Station. 852 MW = GT 3 x 60 MW GT 4 x 108 MW WHRP 2 x 120 MW

• The plant is located close to ONGC Uran terminal where the gas separation is done • A 220 k. V sub-station has been established which connects the station to the state 220 k. V network • A pipeline of 30 cm diameter and 6 km long from ONGC terminal to gas turbine station is completed in 1982 to supply the gas separated at ONGC terminal

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