Numerical investigation of non-equilibrium steam condensing flow in various Laval nozzles
Telegina, Anna (2020)
Diplomityö
2020
School of Energy Systems, Energiatekniikka
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2020120899909
https://urn.fi/URN:NBN:fi-fe2020120899909
Tiivistelmä
Investigation of condensing steam flow plays an important role due to the significance of the steam turbines which is a considerable part of global power generation. Condensation has an enormous impact on the efficiency of the low-pressure turbine which is lower in comparison with high-pressure steam turbine efficiency and study of this problem highly important. Turbine blade erosion, thermodynamic and aerodynamic losses, high level of the liquid mass fraction are caused by condensation in the low-pressure turbine stages. Experiments and numerical studying should be conducted to examine the condensation process and various losses caused by condensation.
In present work, the computational fluid dynamic (CFD) simulations were carried out to research the behaviour of non-equilibrium condensing steam flow inside the last turbine stages. For the CFD simulation, the Eulerian-Eulerian approach was applied. The shear stress transport (SST) k-ω turbulence model was used for solving the turbulence of steam flow. Various convergent-divergent (CD) nozzles were modelled for investigation of the surface tension effect on condensing steam flow. The model was validated with experimental data from literature sources. The results showed that the nucleation rate, droplet numbers and wetness are highly sensitive to the bulk tension factor. The surface tension of the liquid droplets significantly influences the correctness of simulated results provided by the nucleation model. The accuracy of the applied model is satisfactory to capture the condensation shock.
In present work, the computational fluid dynamic (CFD) simulations were carried out to research the behaviour of non-equilibrium condensing steam flow inside the last turbine stages. For the CFD simulation, the Eulerian-Eulerian approach was applied. The shear stress transport (SST) k-ω turbulence model was used for solving the turbulence of steam flow. Various convergent-divergent (CD) nozzles were modelled for investigation of the surface tension effect on condensing steam flow. The model was validated with experimental data from literature sources. The results showed that the nucleation rate, droplet numbers and wetness are highly sensitive to the bulk tension factor. The surface tension of the liquid droplets significantly influences the correctness of simulated results provided by the nucleation model. The accuracy of the applied model is satisfactory to capture the condensation shock.