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Gas Turbine Power Plants

Gas Turbine Power Plants

The gas turbine is one of the oldest device known to man for the conversion of heat into mechanical work. The gas turbine is most satisfactory power developing unit among various means of producing mechanical power due to its exceptional reliability; freedom from vibration and ability to produce large powers from units of comparatively small size and weights. The use of gas turbine plant for developing power was known as early as in 1872.

Unfortunately most efforts towards the development failed due to the lack of understanding of diffusion process taking place in the air passing through the compressor. The axial flow compressor was built to a reasonable degree of efficiency in period of 1930 to 1935 and high temperature materials were also made available during the same period.

The rapid progress in the gas turbine development was made as a result of industrial and military needs. The use of gas turbine in the power generation industry is more recent than its use in any other field. In the last two decades, the rapid progress has been observed in the development and improvement of the gas turbine plants for electric power production.

The major progress has been observed in three directions, increase in unit capacities of gas turbine units (50-100 MW) increase in their efficiency (37%) and drop in capital cost The economics of power generation by gas turbine is proving more attractive in all parts of the world due to its low capital cost and high reliability and flexibility in operation.

The another outstanding feature of gas turbine plant for power generation is capability of quick starting and capability of using wide variety of fuels from natural gas to residual oil or powdered coal. Primary application of gas turbine to the electric supply industry is still for peaking power.

The world's largest peaking installation of 480W is at Astoria Power Station in U.S.A. The massive North east power blackout in 1965 and heavy summer loads in 1969 and other power emergencies during the past decade have helped to establish the gas turbine as an indispensable peaking generator unit in the U.S. power generation industry. The power generation by gas turbine is accounted as 12% of total MW installed during 1969-70 period. Economic installation costs and operational flexibility forecast a long term role for the turbine in the power generation field.

Its relatively low installed cost per KW installed capacity commended attention throughout the world as excellent source of peaking or emergency power. As manufacturers increased the unit size and as the operators become impressed with the operating characteristics of the gas turbine plant the running hours tended to increase subject to the limitations of fuel economics.

This situation was further improved with the addition of' regenerative cycle. With the addition of steam cycle in the gas turbine cycle, the overall efficiency of the plant is further increased. The gas turbine as a base load plant is preferred over the other plants as major delays in completion of large base load fossil and nuclear units