In contrary to the commonly used arc melting method, samples in the present paper were prepared by the solid state reaction from elemental powders at 1173 K under a flowing Ar atmosphere for 96-168 h. The constituent ...In contrary to the commonly used arc melting method, samples in the present paper were prepared by the solid state reaction from elemental powders at 1173 K under a flowing Ar atmosphere for 96-168 h. The constituent phases and the elemental compositions were determined and shown that the samples were of single phase and stoichiometry. Then the spark plasma sintering technique was used to consolidate them. It is found that, dense ZrNiSn-based compounds with fine grain size and homogeneous microstructure were achieved under the condition of 1123 K/40 MPa/25 min.展开更多
The effects of a three-dimensional tapered diffuser vane on the flow field and noise radiated from a centrifugal compressor are investigated by both CFD analyses and experiments. Tapered diffuser vanes are very useful...The effects of a three-dimensional tapered diffuser vane on the flow field and noise radiated from a centrifugal compressor are investigated by both CFD analyses and experiments. Tapered diffuser vanes are very useful not only for the reduction of the interaction tone noise but also for the improvement of the pressure recovery characteristics within the diffuser passage. By using tapered diffuser vanes, the interaction area between the impeller-discharge flow and diffuser vanes becomes small, and then the noise level of the discrete tone can be reduced remarkably as a result. Furthermore, by utilizing the visualization technique of vortical structures based on the CFD results, the scale of vortex shedding leaving from the leading edge of the diffuser vanes is found to be contracted and a tendency for the turbulence level to decrease is observed. This may be the cause of the attenuation of broadband noise components. The secondary flow, which is considered to be an obstruction of diffuser pressure recovery, can also be suppressed by the tapered diffuser vanes, and the pressure decrease observed in the throat part of the diffuser passage is further reducible.展开更多
Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments and visualization techniques using a colored off-film method...Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments and visualization techniques using a colored off-film method. The focus of the research is concentrated on the leading edge shape of diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by more than ten decibels by using modified diffuser vanes which have 3-D tapered shapes on both pressure and suction sur- faces of the leading edge. Furthermore, by adopting the proposed modified diffuser vanes, the secondary flow which is considered to be an obstruction of diffuser pressure recovery can be suppressed, and also the pressure decrease observed in the throat part of the diffuser flow passage is reducible. Thus, the proposed diffuser vanes show a favorable result for both noise and the aerodynamic performance of the centrifugal compressor, and offer a few basic guidelines for the diffuser vane design.展开更多
文摘In contrary to the commonly used arc melting method, samples in the present paper were prepared by the solid state reaction from elemental powders at 1173 K under a flowing Ar atmosphere for 96-168 h. The constituent phases and the elemental compositions were determined and shown that the samples were of single phase and stoichiometry. Then the spark plasma sintering technique was used to consolidate them. It is found that, dense ZrNiSn-based compounds with fine grain size and homogeneous microstructure were achieved under the condition of 1123 K/40 MPa/25 min.
文摘The effects of a three-dimensional tapered diffuser vane on the flow field and noise radiated from a centrifugal compressor are investigated by both CFD analyses and experiments. Tapered diffuser vanes are very useful not only for the reduction of the interaction tone noise but also for the improvement of the pressure recovery characteristics within the diffuser passage. By using tapered diffuser vanes, the interaction area between the impeller-discharge flow and diffuser vanes becomes small, and then the noise level of the discrete tone can be reduced remarkably as a result. Furthermore, by utilizing the visualization technique of vortical structures based on the CFD results, the scale of vortex shedding leaving from the leading edge of the diffuser vanes is found to be contracted and a tendency for the turbulence level to decrease is observed. This may be the cause of the attenuation of broadband noise components. The secondary flow, which is considered to be an obstruction of diffuser pressure recovery, can also be suppressed by the tapered diffuser vanes, and the pressure decrease observed in the throat part of the diffuser passage is further reducible.
文摘Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments and visualization techniques using a colored off-film method. The focus of the research is concentrated on the leading edge shape of diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by more than ten decibels by using modified diffuser vanes which have 3-D tapered shapes on both pressure and suction sur- faces of the leading edge. Furthermore, by adopting the proposed modified diffuser vanes, the secondary flow which is considered to be an obstruction of diffuser pressure recovery can be suppressed, and also the pressure decrease observed in the throat part of the diffuser flow passage is reducible. Thus, the proposed diffuser vanes show a favorable result for both noise and the aerodynamic performance of the centrifugal compressor, and offer a few basic guidelines for the diffuser vane design.
