Numerical analysis of hot steam injection through an embedded channel inside a 3D steam turbine blade

Abstract

The steam expands rapidly and releases its latent heat at the last stages of steam turbines, forming a large number of tiny liquid droplets. This non-adiabatic process results in a sudden phenomenon known as condensation shock, leading to significant thermodynamic losses. Given that the condensation phenomenon can reduce the performance of steam turbines and shorten their lifespan, several studies in recent years have been proposed to eliminate liquid droplets, some focusing on surface heating, others on hot steam injection. However, providing a practical platform design for hot steam injection remains to be studied, which defines the primary goal of this investigation. In this research, a channel is installed inside the 3D turbine blade, allowing hot steam to enter and be stored there. Then, the stored hot steam enters the mainstream flow through eight injection holes with unequal mass flow rates from each hole. Six criteria are defined to see how hot steam injection contributes to decreasing wet steam losses and affects other key parameters. The results of CFD simulations indicate that hot steam injection reduces the rate of erosion, condensation losses, and wetness, respectively, by 58%, 28.5%, and 31.5%. Notwithstanding the advantages of this method, kinetic energy decreases by about 0.5%. This, however, seems to be acceptable due to the remarkable reduction of erosion and condensation losses. Finally, the obtained results indicated the fact that injecting hot steam through the designed channel costs roughly 0.45 ($/hour).