Advanced technologies in Ceramics Gas Turbine (CGT) are expected to make a great progress in energy conservation, anti-pollution, and fuel-diversification. In Japan, R&D’s in industrial usage 300 kW class CGT have been advanced under a national project entitled “New Sunshine Program”, under the subsidy of Agency of Industrial Science and Technology (AIST), Ministry of International Trade and Industry (MITI) through the period of FY1988–1996. In this project, three different type prototypes of the CGT are under development through New Energy and Industrial Technology Development Organization (NEDO). Over the last six years, the basic designs have been completed and the ceramic elements such as turbine rotors, scrolls, and combustors were successfully fabricated. To check up the whole progress of the project, an interim evaluation is scheduled by the end of FY1993. Toward this evaluation, each prototype has been programmed to demonstrate 1200°C of Turbine Inlet Temperature (TIT) and prove more than 30% of thermal efficiency. (The ultimate target in the project is 42% of thermal efficiency at 1350°C TIT.) They would also show enough environmental adaptability. In this paper, overall status of the development in the 300kW CGT project is reviewed and the items in the interim evaluation are explained.

Fundamental heat transfer experiments were carried out for three kinds of heat pipes which may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium(Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium(NaK). Heat pipes B and C included non-condensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, an infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm 2 . The start-up time was about 6 minutes for heat pipe B and about 16 minutes for heat pipe A. Thus adding non-condensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the start-up time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 degrees. There was no significant gravitational dependence on heat transport for heat pipes including non-condensible gas.

Turbine inlet temperature of gas turbine engines have been increased in order to improve engine efficiency but is closing in on the upper limit of capacity for current casting materials and thermal barrier coating systems. To cope with such situations, it is necessary to develop new material applications which have superior heat resistant properties than current casting superalloys, ODS alloys are one of the candidate materials. In this study, optimum HIP (Hot Isostatic Pressing) diffusion bonding parameters and a manufacturing process for turbine vanes of Ni base ODS (Oxide Dispersion Strengthened) alloy, MA754, were developed for the purpose of introducing advanced internal cooling structures. By using these parameters and process, HIP diffusion bonded MA754 turbine vanes were manufactured experimentally. As another application of the bonding process, MA754 turbine vanes HIP diffusion bonded with pure Cu internal cooling structure which has high thermal conductivity were also manufactured.