Investigation Of Real Gas Flows Within Steam And Gas Turbines

Wet steam flows within steam turbine leads to two major problems, loss in turbine stage efficiency and blade erosion. Wet steam has a extraordinary complicated properties, and usually contains condensation phenomenon. At present, developers have to correct the parameters of wet steam turbine stages only by their experience because there are no proper tools for analyzing wet steam two-phase condensing flow directly. On the other hand, the gas flows within gas turbine has a broad range of temperature. Especially inside front stages, the local difference in temperature is up to 700 ~ 800 °C due to the presence of film cooling. Under this situation, the properties of gas can not be treated as perfect gas simply.Considering the departure from perfect gas for wet steam inside steam turbine and high temperature gas with variable specific heat ratio inside gas turbine, a kind of method which can describe the real gas properties of wet steam and high temperature gas was constructed. A new kind of implicit scheme called LU-SGS-GE-RG was developed based on implicit LU-SGS-GE scheme. The mathematical model of wet steam condensing flows was constructed under fully Eulerian system, including Reynolds averaged Navier-Stokes equation, q-ω two-equation turbulence model and four-equation condensation model. Corresponding numerical solver was built to integrate above equation set using the new implicit LU-SGS-GE-RG scheme and an improved high resolution MUSCL TVD scheme. The solver was validated by calculating the supersonic condensing flow in Laval nozzle and film cooling on plate. The numerical results agree with the experimental data very well.By using above solver, numerical simulation was done for the wet steam condensing flow inside the last stage of a steam turbine. The predicted outlet parameters were comparing with the experimental data. The experimental data shows a strong wake near the trailing edge. The wake predicted by perfect gas model was weaken than experimental data. The wake predicted by equilibrium wet steam model agree well with experimental data. The results of non-equilibrium wet steam model was between above two cases due to the absence of veritable droplet information at inlet. Detailed analysis shows that the non-equilibrium wet steam model is sensitive to inlet droplet information.The numerical simulation of film cooling flow of a gas turbine blade was done. The numerical results agree with experimental data very well for low blowing ratio case.In a summary, the numerical analysis system for real gas flows constructed in this paper can predict wet steam flow in steam turbine and film cooling flow in gas turbine. It can be used as a basic tool for further research or turbine blade optimum design.