High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresp...High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresponding to the lower part of the MTZ are import for understanding the nature of the 660 km seismic discontinuity. In this study, we determine phase transfor- mations of olivine （MgSi204） and enstatite （MgSiO3） systematiclly at pressures between 21.3 and 24.4 GPa and at a constant temperature of 1600~C. The most profound discrepancy between olivine and enstatite phase transformation is the occurency of perovskite. In the olivine system, the post-spinel transformation occures at 23.8 GPa, corresponding to a depth of 660 km. In contrast, perovskite appears at 〈23 GPa （640 km） in the enstatite splitting of the 660 km seismic discountinuity under eastern China. system. The -1 GPa gap could explain the uplifting and/orsplitting of the 660 km seismic discountinuity under eastern China.展开更多
The current research on self-resonating cavitating waterjet（SRCW） mainly focuses on the generation mechanism and structure optimization.Researches relating to the influences of disturbances at nozzle inlet on the ch...The current research on self-resonating cavitating waterjet（SRCW） mainly focuses on the generation mechanism and structure optimization.Researches relating to the influences of disturbances at nozzle inlet on the characteristics of the jet are rarely available.In order to further improve the performance of SRCW,effects of area discontinuity（enlargement and contraction） are experimentally investigated using three organ-pipe nozzles.Axial pressure oscillation peak and amplitude as well as aggressive erosion intensity of the jet are used to evaluate the effects.The results reveal that area enlargement and contraction affect the peak differently,depending on the inlet pressure,nozzle geometry,and standoff distance;while area contraction always improves the amplitude regardless of these factors.At inlet pressures of 10 MPa and 20 MPa,area discontinuity improves the peak at almost all the testing standoff distances,while this only happens at smaller standoff distances with the inlet pressure increased to 30 MPa.The capability of area discontinuity for improving the amplitude is enhancing with increasing inlet pressure.Moreover,the cavitation erosion ability of the jet can be largely enhanced around the optimum standoff distance,depending on the type of area discontinuity and nozzle geometry.A preliminary analysis of the influence of area discontinuity on the disturbance waves in the flow is also performed.The proposed research provides a new method for effectively enhancing the performance of SRCW.展开更多
基金financially supported by the Sinoprobe-0801National Natural Science Foundation of China(Grant Nos.41002068&41174076)
文摘High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresponding to the lower part of the MTZ are import for understanding the nature of the 660 km seismic discontinuity. In this study, we determine phase transfor- mations of olivine （MgSi204） and enstatite （MgSiO3） systematiclly at pressures between 21.3 and 24.4 GPa and at a constant temperature of 1600~C. The most profound discrepancy between olivine and enstatite phase transformation is the occurency of perovskite. In the olivine system, the post-spinel transformation occures at 23.8 GPa, corresponding to a depth of 660 km. In contrast, perovskite appears at 〈23 GPa （640 km） in the enstatite splitting of the 660 km seismic discountinuity under eastern China. system. The -1 GPa gap could explain the uplifting and/orsplitting of the 660 km seismic discountinuity under eastern China.
基金Supported by National Key Basic Research Program of China(973 Program,Grant No.2014CB239203)National Natural Science Foundation of China(Grant No.51474158)China Scholarship Council(Grant No.201406270047)
文摘The current research on self-resonating cavitating waterjet（SRCW） mainly focuses on the generation mechanism and structure optimization.Researches relating to the influences of disturbances at nozzle inlet on the characteristics of the jet are rarely available.In order to further improve the performance of SRCW,effects of area discontinuity（enlargement and contraction） are experimentally investigated using three organ-pipe nozzles.Axial pressure oscillation peak and amplitude as well as aggressive erosion intensity of the jet are used to evaluate the effects.The results reveal that area enlargement and contraction affect the peak differently,depending on the inlet pressure,nozzle geometry,and standoff distance;while area contraction always improves the amplitude regardless of these factors.At inlet pressures of 10 MPa and 20 MPa,area discontinuity improves the peak at almost all the testing standoff distances,while this only happens at smaller standoff distances with the inlet pressure increased to 30 MPa.The capability of area discontinuity for improving the amplitude is enhancing with increasing inlet pressure.Moreover,the cavitation erosion ability of the jet can be largely enhanced around the optimum standoff distance,depending on the type of area discontinuity and nozzle geometry.A preliminary analysis of the influence of area discontinuity on the disturbance waves in the flow is also performed.The proposed research provides a new method for effectively enhancing the performance of SRCW.
