Numerical study of the impact of hot steam injection in the condensation flow through the low-pressure stage of steam turbine

Abstract

Nowadays, steam turbines are the devices vastly used for energy generation in power plants. Accordingly, their performance and efficiency are crucially significant. In the last stages of the steam turbine, the presence of liquid phase decreases the efficiency and causes thermodynamic and dynamic losses. Various parameters can affect the steam flow and change the liquid droplets generated as well as the wetness fraction. In the present study, the hot steam injection parameter which affects the wetness decrease for the low-pressure stage of a steam turbine (LPST) has been investigated. First, the impact of hot steam injection (HSI) was studied on the wet steam flow parameters. Hot steam is injected on the suction surface of the stator with various slot angles and slot widths to select the optimal case. The goal of this study is to achieve the optimal value of injection variables to use this method further. To apply this, the LKHCE (Liquid mass, Kinetic energy, Hot steam, Condensation loss, Efficiency) criterion is used for all modes. Also, by examining the results of this method and using the TOPSIS, the optimal case can be selected. The condensing flow of wet steam through the stator-rotor blades is modeled using an Eulerian-Eulerian model and the SST k-turbulence model. Case 6 (angle 40°, slot width 0.1(cm)) for HSI is predicted as the optimal case, in which RL and RC decrease by 35.5 % and 34.6%, respectively, and RE is increased by 1.3%. The HSI caused a slight decrease in RK by 0.3% at the steam turbine stage’s outflow.