Capillary Pumped Loop (CPL) is a tWo Phase closed system. The tWo main components of CPL, both evaporatorand reservoir are generally believed to play significant roles in its unsteady operation. In thes paper, experim...Capillary Pumped Loop (CPL) is a tWo Phase closed system. The tWo main components of CPL, both evaporatorand reservoir are generally believed to play significant roles in its unsteady operation. In thes paper, experimentaland theoretical investigations are carried out on the influences of unsteady chararterishcs of both of them. Theprevious analyhcal results show that there is a pressure oscillation source in the evaporator and the internaloscillation frequency can be obtained. The reservoir also has an unsteady characterishcs, when the reservoir line hasa smaller damping value, there will be a self-oscillation of Pressure in the reservoir, and its analyhcal frequenciesare normally one or two quantihes bigger than the inherent frequencies of the evaporator. In order to keep CPLoperate steadily, on one hand, the structure of evaporator must be increased to make the conhnuous generated vaporflow out the wick easily, on the other hand, the return liquid ought to be subcooled enough to the reservoirtemperature set value.展开更多
As the pump turbine tends to be operated with high head and high rotational speed, the study of stability problems becomes more important. The pump turbine usually works at operating conditions where the guide vanes e...As the pump turbine tends to be operated with high head and high rotational speed, the study of stability problems becomes more important. The pump turbine usually works at operating conditions where the guide vanes experience strong vibrations. However, most traditional studies were carried out based on constant GVO(guide vane opening) simulations. In this work, dynamic analysis on pressure fluctuation in the vaneless region of a pump turbine model was conducted using a dynamic mesh method in turbine mode. 3D unsteady simulations were conducted where GVO was closed and opened by 1° from the initial 18°. Detailed time domain and frequency domain characteristics on pressure fluctuation in the vaneless region under different guide vane rotational states compared with constant GVO simulations were investigated. Results show that, during the guide vanes oscillating process, the low and intermediate frequency components in the vaneless region are significantly different. The amplitudes of pressure fluctuation are higher than those with constant GVO simulations, which agree better with the experimental data. In addition, the pressure fluctuation increases when GVO is opened, and vice versa. It can be concluded that pressure fluctuation in the vaneless region is strongly influenced by the oscillating of the guide vanes.展开更多
文摘Capillary Pumped Loop (CPL) is a tWo Phase closed system. The tWo main components of CPL, both evaporatorand reservoir are generally believed to play significant roles in its unsteady operation. In thes paper, experimentaland theoretical investigations are carried out on the influences of unsteady chararterishcs of both of them. Theprevious analyhcal results show that there is a pressure oscillation source in the evaporator and the internaloscillation frequency can be obtained. The reservoir also has an unsteady characterishcs, when the reservoir line hasa smaller damping value, there will be a self-oscillation of Pressure in the reservoir, and its analyhcal frequenciesare normally one or two quantihes bigger than the inherent frequencies of the evaporator. In order to keep CPLoperate steadily, on one hand, the structure of evaporator must be increased to make the conhnuous generated vaporflow out the wick easily, on the other hand, the return liquid ought to be subcooled enough to the reservoirtemperature set value.
基金supported by the National Key Technology R&G Program(Project No.2012BAF03B01-X)Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51121004)
文摘As the pump turbine tends to be operated with high head and high rotational speed, the study of stability problems becomes more important. The pump turbine usually works at operating conditions where the guide vanes experience strong vibrations. However, most traditional studies were carried out based on constant GVO(guide vane opening) simulations. In this work, dynamic analysis on pressure fluctuation in the vaneless region of a pump turbine model was conducted using a dynamic mesh method in turbine mode. 3D unsteady simulations were conducted where GVO was closed and opened by 1° from the initial 18°. Detailed time domain and frequency domain characteristics on pressure fluctuation in the vaneless region under different guide vane rotational states compared with constant GVO simulations were investigated. Results show that, during the guide vanes oscillating process, the low and intermediate frequency components in the vaneless region are significantly different. The amplitudes of pressure fluctuation are higher than those with constant GVO simulations, which agree better with the experimental data. In addition, the pressure fluctuation increases when GVO is opened, and vice versa. It can be concluded that pressure fluctuation in the vaneless region is strongly influenced by the oscillating of the guide vanes.
