| dc.description.abstract | This project investigates the performance of a Terry GS-2 turbine, and the attached trip-throttle valve and governor valve under two-phase (air/water) flow conditions. Because of their robust design, Terry turbines are used within the nuclear power generation industry in Reactor Core Isolation Cooling (RCIC) systems to remove decay heat during isolation events. During the Fukushima Daiichi nuclear power station disaster in Japan in 2011, the RCIC system and associated Terry turbine operated for over 70 hours: much longer than the 8 - 12 hours typically expected of similar RCIC systems, as they are expected to over-speed and trip upon backup battery depletion and loss of flow control. Theories suggest the turbine was subjected to a two-phase flow, thus degrading the turbine performance, while the RCIC system was simultaneously experiencing conditions that promoted self-regulating operation.
The project experimentally determines the flow coefficient of the two valves when subjected to single-phase air and single-phase water flow conditions over the range of valve stem withdrawal positions. The project also investigates the effect of inlet pressure, flow quality (air mass fraction), and turbine rotational speed on the performance of the turbine when subject to two-phase flows. The turbine was tested at inlet pressures ranging from 20 to 70 psia, qualities from 100% (single-phase air) to 5%, and rotational speeds up to 3600 RPM. The turbine performance is evaluated using torque and efficiency variation as a function of two-phase flow.
A flow visualization study was included to better understand the interaction between the gaseous and liquid phases of the two-phase flow, especially at elevated pressures within the turbine nozzles. The two-phase flow regimes are characterized as a function of pressure and flow quality. Preliminary data regarding the turbine bearing friction is also discussed.
The results will be combined with previous data from a small-scale Terry ZS-1 steam turbine to understand the scaling relationship between large and small Terry turbines. Experimental data and analysis will assist investigators in understanding the performance of the Terry turbine as a component of the RCIC system, and provide experimental data for the validation of turbine models simulating the Fukushima accident. | en |
