Content: Introduction A Simple Gas Turbine Plant & It’s Working Plant Layout Types according to Cycle 1. Open Cycle Gas Turbine Plants 2. Close Cycle Gas Turbine Plants Fuels for Gas Turbine Plants Methods to Improve Thermal Efficiency of the Plant 1. Regeneration 2. Intercooling 3. Reheating Advantages Disadvantages Applications Conclusion

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. Air is used as the working fluid. Air is compressed by the compressor is lead to the combustion chamber where heat is added to air. Hot and high pressure air from the combustion chamber is then passed to the gas turbine where it is expands and does the mechanical work. The gas turbine drives the alternator which converts the mechanical energy into electrical energy. These plants are suitable for peak load purpose because their fuel costs are some what higher while there initial cost are low.

Simple gas turbine plant A simple gas turbine plant consist of a compressor, combustion chamber or combustor and turbine. Besides these components there may be auxiliaries such as starting device, fuel system, the duct system, auxiliary lubrication system etc.

(A Simple Gas Turbine Plant)

working When the unit runs atmospheric air is drawn in by the compressor and it raised to starting pressure which is several time that of atmosphere. The fuel injected into the combustor. The temperature exhaust gases is in the range of about 475° to 550° C. N.B.:- in the compressure a part of the air is delivered ahead of the burning fuel this is done to cool the very hot combustion products which are at temperature 1600° C to bring them down to a temperature of range 650° to 800°C.

(Plant lay out of a gas turbine plant)

Plant layout The layout has an important effect on the over all performance of the plant since there may be a lose of as much as 20% of the power developed in the inter connecting ducts with a large number of sharp bends. In case of gas turbine plant the main building is the turbine house in which major person of the plant as well as auxiliaries are installed. The fuel oil storage tank are arranged out side but adjoining to the turbine house.

Open cycle gas turbine plant:- Since ambient air enters the compressor and gasses coming out of the turbine are exhausted into the atmosphere, the working medium has to be replaced continuously. At present majority of gas turbine power plants used this type of cycle.

Close cycle gas turbine plant:-

Fuel for gas turbine plants A wide variety of fuels from solid to gaseous can be used in the gas turbine plants. The ideal fuel is the natural gas. Liquid fuels of petroleum origin such as distillate oils or residual fuels are most commonly used for such plants. Minerals like sodium, vanadium and calcium prove very harmful for turbine blades as they build up deposits or corrode the blades. Use of solid fuels (for example pulverized coal) in gas turbine presents a number of difficulties involved even though use of coal for closed cycle plant is universally accepted.

1.Regeneration The exchange of heat takes place in a device known as regenerator. A regenerator is usually of shell and tube construction. The exhaust gasses are made to flow inside the nest of tubes whereas air flows out side the tubes in the shell in counter flow and is heated up by the heat given out by the gasses.

2.Intercooling Intercooling means cooling the air after it has been partially compressed. Intercooling results in improvement of thermal efficiency, air rate and work ratio. Therefore when intercooling is emlpoyed the size of turbine and compressor for the same output can be reduced or plant of the same size can give greater work.

3.Reheating Gasses after partial expansion in the turbine may be reheated so that they can be expanded further and may produced additional work. Reheating may in fact be taken as anb additional combustor.

Advantages Simple in design Smaller in size Initial and a operating cost are much lower Require less water Maintenance charges quite small Simple construction and operation Started quickly from cold condition

Disadvantages There is problem for starting the unit Net output is low Over all efficiency is low Life is comparatively reduced

Conclusion From the above topic I conclude that gas turbine plants possess inherent advantages of simplicity and flexity of design and installation. From the view of point of price it has been estimated that the steam plant developing power at 17% efficiency costs equal to the gas turbine plant developing power at 34%. This being the case that gas turbine plant as a base load plant has little future.