Addition of steam to combustors in gas turbines and to internal-combustion engines reduces the peak temperatures and
Question:
Addition of steam to combustors in gas turbines and to internal-combustion engines reduces the peak temperatures and lowers emission of NOx. Consider a modification to a gas turbine, as shown in Fig., where the modified cycle is called the Cheng cycle. In this example, it is used for a cogenerating power plant. Assume 12 kg/s air with state 2 at 1.25 MPa, unknown temperature, is mixed with 2.5 kg/s water at 450◦C at constant pressure before the inlet to the turbine. The turbine exit temperature is T4 = 500◦C, and the pressure is 125 kPa. For a turbine efficiency of 23%, estimate the required air temperature at state 2.
Compare the result to the case where no steam is added to the mixing chamber and only air runs through the turbine. Which case is better, justify your reasoning.
Fundamentals of Thermodynamics
ISBN: 978-0471152323
6th edition
Authors: Richard E. Sonntag, Claus Borgnakke, Gordon J. Van Wylen