The ceramic gas turbine (CGT) engine can achieve higher thermal efficiency, lower pollutant emissions, and has a wider fuel tolerance compared to conventional gasoline and diesel engines. Accordingly, research and development of a 300kW class ceramic gas turbine has been performed in Japan as a national project since FY 1988, under the Agency of Industrial Science and Technology (AIST), which is an agency of the Ministry of International Trade and Industry (MITI). The final target of the project is to achieve 42% thermal efficiency at a Turbine Inlet Temperature (TIT) of 1350°C.
At present, two different types of ceramic gas turbines (CGT 301 and CGT 302) are under development and operating tests of prototype engines are being carried out. The CGT 301 features removable ceramic blades joined to a metal rotor disk. This 37 blade hybrid rotor of the high pressure stage was hot spin tested at a TIT of 1350°C and the burst of the blades did not occur at the rated speed. A thermal efficiency of 26.4% was achieved at a TIT 1200°C during the first year of prototype operation. Improvement in component parts is ongoing and as a result, improvements in thermal efficiency are forthcoming.
The CGT 302 features a lean premixed low-NOx combustor having a primary diffusion burner, a set of main pre-mixed burners, single fuel injector, and air bypass to control combustion. This combustor showed a lower pressure loss and NOx emissions of 5ppm (O2 = 16%), which is less than the allowable value of 70ppm. Recent operating tests of this engine showed a maximum output power and thermal efficiency of 228kW and 36%, respectively, as of November 1996.
For both the CGT 301 and CGT 302, more focused research on CGT materials and components, as well as operating tests at 1350°C TIT, are being carried out in order to reach the final target values.