[en] The position sensors used in a magnetic bearing system are desirable to provide some degree of fault-tolerance as the rotor position is necessary for the feedback control to overcome the open-loop instability. In this paper, we propose and inductive position sensor that can cope with a partial fault in the sensor. The sensor has multiple poles which can be combined to sense the in-plane motion of the rotor. When a high-frequency voltage signal drives each pole of the sensor, the resulting current in the sensor coil contains information regarding the rotor position. The signal processing circuit of the sensor extracts this position information. In this paper, we used the magnetic circuit model of the sensor that shows the analytical relationship between the sensor output and the rotor motion. The multi-polar structure of the sensor makes it possible to introduce redundancy which can be exploited for fault-tolerant operation. The proposed sensor is applied to a magnetically levitated turbo-molecular vacuum pump. Experimental results validate the fault-tolerance algorithm

[en] Gas turbines operate under severe conditions such as high temperature and pressure. Thus, NDT technologies is critical to ensure the integrity of facilities. Conventional NDT methods to inspect parts of gas turbine are fluorescent penetrant inspection, magnetic particle testing, etc. These method has limits to identify flaws of gas turbine. In this study, eddy current testing was performed with the surface eddy current probe for the gas turbine 1'st stage bucket. Reference specimens is designed and made with EDM notches. We estimated the depth of the surface crack which is occurred in the 1'st stage bucket.

[en] Gas turbines operate under severe conditions such as high temperature and pressure. Thus, NDT technologies is critical to ensure the integrity of facilities. Conventional NDT methods to inspect parts of gas turbine are fluorescent penetrant inspection, magnetic particle testing, etc. These method has limits to identify flaws of gas turbine. In this study, eddy current testing was performed with the surface eddy current probe for the gas turbine 1'st stage bucket. Reference specimens is designed and made with EDM notches. We estimated the depth of the surface crack which is occurred in the 1'st stage bucket.

[en] Highlights: • The hybrid system maximizes latent heat recovery and fuel conversion to the power. • Injecting the boiler flue gas into the gasifier improves oxy-coal gasification. • Reusing the boiler flue gas as a diluent in a gas turbine enhances its utilization. • Using additional heat exchangers provides the flexibility of thermal integration. • Extensive heat recovery and hybridization increase the net efficiency of the system. This study proposes the 2nd generation hybrid pressurized oxy-coal combustion power cycle that utilizes both fluidized-bed combustion coupled with the Rankine cycle and gasification connected to the Brayton cycle. The fluidized-bed boiler and gasifier are thermally connected by a flue gas stream flowing from the former to the latter. This improves thermal integration carbon conversion in the gasifier. The Rankine cycle is thermally connected to the Brayton cycle through the reheating process of intermediate pressure steam. This hybrid cycle enables the system to recover thermal energy from the pressurized flue gas with effective thermal integration in a way that it balances heat flow rates between hot and cold streams and increases the degree of freedom for heat flow control. The proposed system also reuses cold boiler exhaust gas as a diluent of the Brayton cycle to control its gas turbine inlet temperature, which raises the gas turbine flow rate and hence the gross power. The results indicate more than 9%-point and 1%-point increases in the gross and net efficiency, respectively, as compared to a single Rankine cycle system. The proposed hybrid system exhibits the net efficiency of 34.39% (HHV) higher than 33.04% (HHV) of the single oxy-PFBC cycle.