This paper describes physics‐based moisture loss models for designing wet‐steam turbines. Steam turbines operating under wet‐steam conditions experience thermodynamic and mechanical losses caused by the presence of moisture. The developed moisture loss models are composed of six categories: supersaturation loss, condensation loss, acceleration loss, braking loss, capturing loss, and pumping loss. These losses are calculated according to the wetness levels in the stationary blade and moving blade rows, and defined by the functions of steam properties and design factors of turbine stages. The supersaturation loss produced by non‐equilibrium expansion of the wet steam is modeled using the pressure ratio and the isentropic exponent of the supersaturated steam. The loss models are compared to full‐size test turbine data for prediction of the overall moisture losses. As a result, the developed loss models are found to be very effective for estimating the moisture losses of turbine stages. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 42(7): 651–664, 2013; Published online in Wiley Online Library (http://wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20395

The development of integrated coal gasification combined cycle (IGCC) systems ensures cost-effective and environmentally sound options for supplying future coal utilizing power generation needs. The Japanese government and the electric power industries in Japan promoted research and development of an IGCC system using an airblown entrained-flow coal gasifier. We worked on developing a low-Btu fueled gas turbine combustor to improve the thermal efficiency of the IGCC by raising the inlet-gas temperature of gas turbine.On the other hand, Europe and the United States are now developing the oxygen-blown IGCC demonstration plants. Coal gasified fuel produced in an oxygen-blown entrained-flow coal gasifier, has a calorific value of 8.6MJ/m 3 which is one fifth that of natural gas. However, the adiabatic flame temperature of oxygenblown medium-Btu coal gaseous fuel is higher than that of natural gas and so NOx production from nitrogen fixation is expected to increase significantly. In the oxygen-blown IGCC system, a surplus nitrogen in quantity is produced in the oxygen-production unit. When nitrogen premixed with coal gasified fuel is injected into the combustor, the power to compress nitrogen increases. A low NOx combustion technology which is capable of decreasing the power to compress nitrogen is a significant advance in gas turbine

This paper describes physics-based moisture loss models for designing wet-steam turbines. Steam turbines in wet-steam conditions experience thermodynamic and mechanical losses caused by the presence of moisture. The developed moisture loss models are composed of six categories : supersaturation loss, condensation loss, accelerating loss, braking loss, capturing loss and pumping loss. These losses are calculated according to the wetness levels in the nozzle & bucket rows, and defined by the functions of steam properties and design factors of turbine stages. The supersaturation loss produced by the non-equilibrium expansion of the wet steam is modeled using the pressure ratio and the isentropic exponent in the supersaturated steam. The loss models are applied to the full-size test turbine data for the prediction of the overall moisture losses. As a result, the developed loss models are found to be very effective for estimating the moisture losses of turbine stages.

This paper describes characteristics of moisture losses in low pressure steam turbine stages. Steam turbines operating under wet-steam conditions experience thermodynamic and mechanical losses caused by the presence of moisture. In order to predict the moisture losses, physics-based moisture loss models are developed. The moisture loss models are composed of six categories: supersaturation loss, condensation loss, acceleration loss, braking loss, capturing loss and pumping loss. These losses are calculated according to the wetness levels in the stationary blade & moving blade rows, and defined by the functions of steam properties and design factors of turbine stages. The loss models are compared to full-size low pressure steam turbine data for prediction of the overall moisture losses. The developed loss models are found to be effective for designing wet-steam turbines from the standpoint of calculation accuracy and calculation time.

Progress in the computer performance has enabled automatic optimization of the three dimensional shape of turbine blades with a large number of large-scale CFD (Computational Fluid Dynamics) calculations. This paper presents an advanced aerodynamic optimization system for turbine blades. The system can automatically find improved blade shapes that give better aerodynamic performance in a turbine stage and reduces human efforts to generate blade shape data, computational mesh, CFD input data etc. The system consists of three parts; parameter updating part, blade shape generation part, and aerodynamic performance evaluation part. In the parameter updating part, users can choose DOE (Design of Experiment) or evolutionary optimization method such as GA (Genetic Algorithm), ASA (Adaptive Simulated Annealing), etc. to define the parameters in each step. The shape generation part changes the blade shapes using NURBS curves whose control point parameters are defined in the parameter updating part. Three-dimensional CFD grid is automatically generated for the changed blade shapes and steady CFD calculation is used to evaluate the aerodynamic performance of the changed blades in a turbine stage. Stagger angle distribution in the radial direction was thought as one of the important design parameters of turbine blades because it determines the flow pattern in radial direction. Then it was chosen as an optimized parameter with NURBS curves in this system. First, DOE was used for the human optimization, in which the parameter range for the advanced optimization was estimated and the best shape obtained was used as the initial shape for the evolutionary optimization to explore better blade shape parameters. Stage loss of an exhaust stage of IP (Intermediate Pressure) turbine which contains relatively high aspect ratio was chosen as the objective. In spite that such kind of stage was considered not to be sensitive to three dimensional stacking, the results showed good performance enhancement.