Addition of steam to combustors in gas turbines and to internal-combustion engines reduces the peak temperatures and lowers emission of NO. Consider a modification to a gas turbine, as shown in Fig. P12.176, where the modified cycle is called the Cheng cycle. In this example, it is used for a cogenerating power plant. Assume 12 kg/s of air with state 2 at 1.25 MPa, unknown temperature, is mixed with 2.5 kg/s of 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 reasonable turbine efficiency, 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.