Launching of Single, Small Particles for Impact FOD Testing of Ceramic Gas Turbines

Abstract

In developing ceramic gas turbines (CGT), impact test technique of ceramic elements at elevated temperature (sometime with tensile stress) is very important. For the purpose of establishing an impact simulation technique for small, foreign object damage (FOD) without contamination of testing environment, launch experiment of single particle of 1 mm diameter is made by using micro-sabot and electrothermal (ET) gun. Since the ET gun exhausts only small amount of gases, it is expected not to disturb temperature condition of testing environment. Particle velocity is measured by various methods based on 1) time difference between impact acoustic signals at muzzle and target, 2) high-speed photographs, and 3) induction current signal from coil-magnet flyer particle system. First particle is mounted on the micro-sabot and accelerated together. Then they are separated by sabot stopper placed at the ET gun muzzle. In the present experiments particle velocities up to about 2,000 m/s are obtained. However, complete separation of particle and sabot, where no sabot fragments appear from the muzzle, is possible up to about 1,000 m/s within the present separation system. This velocity range covers the required one (≦ 800 m/s). By using the launch system, impact tests of the actual turbine CGT-303 are carried out at room temperature without any loads. The tests at elevated temperature with tensile stresses are scheduled in the near future.