International Journal of Engineering Studies. ISSN 0975- 6469 Volume 2, Number 4 (2010), pp. 481-489 © Research India Publications http://www.ripublication.com/ijes.htm Effect of Supplementary Heating on the Performance of Combined Cycle B.B. Arora* 1 , J.N. Rai 2 and Naimul Hasan 3 1 Department of Mechanical Engineering, DTU, New Delhi, India 2 Department of Electrical Engineering, DTU, New Delhi, India 3 Department of Electrical Engineering, JMI, New Delhi, India *Corresponding Author E-mail: prof_bbar@yahoo.com Abstract In this paper, Turbine Inlet Temperature (TIT), Specific Work Output and Thermal Efficiency of combined cycle have been analysed at different Air Fuel ratios, pressure ratios and variable Supplementary heating. The Pressure ratios have been taken in the range of 4 to 20, Air fuel Ratio 50, 55, 60 and 65 and Supplementary heating from 0.1 to 0.5. The results show that the Specific Work Output and Thermal Efficiency improved at lower Air Fuel Ratio and lower Supplementary heating and at higher value of pressure ratio. In the analysis it was desirable that the actual exhaust temperature of gas turbine plus gas turbine bypass temperature should be above 813 K. Keywords: Air Fuel Ratio, Pressure Ratio, Variable Supplementary heating, Specific Work Output and Thermal Efficiency. Introduction Energy is a fundamental requirement of human life, and driving force of civilization so it must be utilized very efficiently at all levels. Due to increased fuel prices and depletion of fossil fuel resources, high efficiency energy conversion systems are at most desirable. There is great potential for increased efficiency in energy converting devices by recovering waste heat to great extent. It was realized that the thermal efficiency of the gas turbine was very poor as around sixty percent of the total heat generated in the combustion chamber goes waste in the exhaust. Hence it was realized that the thermal efficiency of the gas turbine plant can be improved if the use of waste energy can be made to generate steam. Thus the concept of combined cycle came into existence. The significance of the combine power plant is that it utilizes the waste energy for generation of steam to run the steam turbine. This leads to increase in