Significant advances in flow field measurement technology have been observed in recent years. This is because multidimensional measurement and visualization methods have become relatively easy to use. This has made it possible to elucidate complex flow fields that were previously difficult and contributing greatly to the improvement of hydro turbines performance. However, many multidimensional measurement methods are optical, such as those represented by PIV. This has the limitation that a window must be installed in the experimental setup. Therefore, we attempted to measure the flow field using medical MRI, which can transmit and observe regardless of the shape if it does not affect the magnetic field.
This paper reports the results of the application of MRI to flow measurement in a bulb turbine draft tube model. In addition, the usefulness of the improvement method for the problems of MRI flow field measurement is also presented.
The final target of this feasibility study is to implimante in society of a small output organic Rankine cycle（ORC）less than 10 kW. In this study, the evaluation method of a turbine performance which is the major component in the ORC was examined, moreover, the performance of the ORC was evaluated by the heat source of Obama hot spring in Unzen city. In the verification test of Obama hot spring, the thermal efficiency of the prototype ORC was 2.4％. The turbine efficiency at a design point in the turbine test was 21.2％, whereas the turbine efficiency in the ORC verification test was 19.2％. These results indicated that the turbine efficiency could express the universal turbine performance.
In turbo-machineries, there exist the vibration problems that the blades which are most important parts are broken. Many of them are due to the resonance. When the resonance occurs once it is obliged to stop the operation of the factory. Therefore, it is desired that the blade does not break even if in the resonance. The author has been studied the vibration problems of blades for many years. In these studies, it would like to be known that the damping ratio of the first vibration mode is the same as these of higher modes. If the damping ratio is independent of the vibration mode all we have to do is to evaluate only the damping ratio of the first mode. Then in this study, it will be discussed that whether the damping ratio is dependent on the vibration mode or not.
Extraordinary stress on runner blade during start-up at the low specific speed Francis turbine cause severe damage to the blades. To make clear the mechanism of the extraordinary stress, CFD analysis in addition to the measurement of the model and the prototype turbine was carried out. By the analysis of the model and the prototype turbine, it became clear that the phenomenon is commonly arisen as the transient hydraulic behavior, and the impact load causing extraordinary stress on runner blades is related to the impulsive pressure rise. From a comparison of CFD and model test result, it is concluded that the impulsive pressure rise was caused by the result of chain-reaction of the cavitation cloud in the runner passage.