Akinori Koga

Study on the High Efficiency Closed Cycle Gas Turbine System

In WE-NET project Phase I Program, the power generation system with more than 60%(HHV) thermal efficiency had been designed. However, because this system must be fueled by pure hydrogen, commercialization of this system in early stage is thought to be difficult. Therefore, the new project, in which the natural gas fueled system is targeted, has been started since FY1999. In this project, the power generation efficiency is aimed to be 60%(HHV) or higher, with turbine inlet maximum temperature of 1973K. In this report, the feature of the target system is explained at first. Then, the sensitivities of many parameters are examined in detail.© 2001 ASME

Evaluation of 1700C Class Turbine Blades in Hydrogen Fueled Combustion Turbine System

This paper describes the cooling design and experimental evaluations of the 1700C class turbine blades in hydrogen fueled combustion turbine system. The hybrid cooling method combining recovery steam cooling with partial film cooling was chosen based on a careful study on several cooling systems from the viewpoint of plant efficiency and durability of turbine blades. In the development process, high temperature cooled turbine blades, the advanced cooling technologies, single crystal super alloy and thermal barrier coating (TBC) are important issues to be paid attention and following experiments were performed. First, outer heat transfer test on stator blade and internal heat transfer test in ribbed channel for cooling rotor blade were carried out using liquid crystal thermography. The cooling effectiveness of rotor blade was further investigated in steam driven wind tunnel. The characteristics of single crystal super alloy and TBC were also evaluated in hot steam environment. As a next step, the scale model test blades of size nearly one half to that of the first stage stator and rotor blades in actual turbine were designed and manufactured. Finally, the turbine blade cascade tests were conducted using hydrogen-oxygen combustion driven wind tunnel under practical hot steam conditions of 1700C and 2.5MPa. In these experiments, cooling effectiveness, metal temperatures and cooling steam flow characteristics were investigated. After completing all the test runs, the robustness of blade substrate and TBC were inspected. The experimental results on the hybrid cooling method and blade design procedures are discussed.© 2000 ASME

Effect of Cooled Turbine Blade Surface Roughness on Heat Transfer Rate and Metal Temperature in Gas Turbine Field Operations.

This paper describes the effect of turbine blade surface roughness on the heat transfer rate and metal temperature in gas turbine long term field operations. The metal temperature of Ni based super-alloys can be estimated from changes in microstructure due to the aging. Applying this technology to the rotating blades used in gas turbine field operations, long term operational metal temperature were higher than during short term operation. Also, it was observed that the surface roughness of rotating blades increased during long term operations compared to new blades, which corresponds to the increase in metal temperature. The increased heat transfer rate on the rough surface of the rotating blades was predicted analytically. From these results, the relationship of the rotating turbine blade surface roughness and the increase in the metal temperature in gas turbine field operations can be estimated.

The Advanced Cooling Technology for the 1500 °C Class Gas Turbines: The Steam Cooled Vanes and the Air Cooled Blades

It is very essential to raise the thermal efficiency of combined cycle plants from the viewpoint of energy saving and environmental protection. Tohoku Electric Power Co., Inc. and Toshiba Corporation in Japan have jointly studied the next generation of combined cycle system using 1500 °C class gas turbine.A promising cooling technology for the vanes using steam was developed. The blades are cooled by air, adopting the impingement cooling, the film cooling and so on. The cooling effectiveness was confirmed both for the vanes and the blades using hot wind tunnel. This paper describes the design features of the vanes and the blades, and the results of the verification tests using hot wind tunnel.© 1996 ASME

Hot Spinning Test for Ceramic Moving Blades.

The inlet temperature of a gas turbine has been increased to improve its thermal efficiency. Accordingly, the technique of applying ceramics to the hot parts of a gas turbine has been studied recently. Among them, moving blades are rotating parts and used under severe thermal and vibrating conditions. Toshiba has developed ceramic moving blades for a 1300°C-level gas turbine, and is planning to mount them on a pilot experimental gas turbine in the near future. Hot spinning test equipment has been developed, and these ceramic blades were tested under conditions similar to those of the pilot machine. Furthermore, limitation tests for overtemperature and 110 percent overspeed were carried out. In consequence, the reliability of ceramic moving blades was ascertained. In this paper, the results of a hot spinning test for the ceramic blades are described, and the process and some problems in the development of the test equipment are also discussed.