During the course of expansion of steam in turbines, the vapour first supercools and then nucleates to become a two phase mixture. The flow initially is single phase but after Wilson point water droplets are developed and there is a non equilibrium two phase flow. This growing droplets release their latent heat to the flow and this heat addition to the supersonic flow cause a pressure rise called condensation shock. Because of irreversible heat transfer in this region the entropy will increase tremendously. The following study investigates the spraying water droplets at inlet of Laval nozzle and their effects on nucleation rate and condensation shock. According to the results, the nucleation rate is considerably decreased and therefore the condensation shock nearly disappeared. In other words the injecting droplets at the inlet of steam turbine would decrease the thermodynamic losses or improve the turbine efficiency.

Keywords