Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promot...Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.展开更多
Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on ...Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on the flow characteristics of the hub plate crown is of practical significance. The shroud and hub cavities are respectively studied with regard to tangential and radial velocities at the four different angular positions(0°, 90°, 180°, and 270°) at the four different operational points(0.6 Qsp, 0.8 Qsp, 1.0 Qsp, and 1.2 Qsp). Results indicate that at the same operational point, the smaller the volute chamber sectional area is, the higher the tangential velocity of the fluid core zone of the shroud cavity is. Radial leakage flow from the volute to the seal ring at the same operational point appears in 0° and 90° direction;when the flow is large, the tangential and radial velocities of the shroud and hub cavities with the same radius tend to be equal with axial symmetry. The axial leakage flow through the balance holes significantly affects the radial distribution of both tangential and radial velocities of fluid flow in the hub cavity. The numerical calculation results of fluid leakage through the clearance of back sealing ring are in good agreement with the test results. Accordingly, the magnitude of leakage is closely related to the fluid pressure and velocity distribution in the hub plate crown of the centrifugal pump. The analysis of the flow characteristics in the hub plate crown of the centrifugal pump could reveal the cause of the disc friction loss from the mechanism, providing a significant guidance for improving the accuracy of calculation and balancing the axial thrust in the centrifugal pump.展开更多
This paper presents the aspirated modification of a dual-stage counter-rotating compressor which contains inlet guide vanes（IGVs）, two counter-rotating rotors（R1, R2）, and outlet guide vanes（OGVs）.Uniform circul...This paper presents the aspirated modification of a dual-stage counter-rotating compressor which contains inlet guide vanes（IGVs）, two counter-rotating rotors（R1, R2）, and outlet guide vanes（OGVs）.Uniform circular holes are circumferentially distributed over the rotors＇ tips on the shroud casing which are designed to remove the low-energy fluid near the shroud casing.OGVs are hollow blades with two slots designed on the suction side which can better control the flow on the suction surface through boundary layer suction.Related works about the experiments have been carried out since June 2012 and the effect of flow suction on the performance of the compressor is investigated in detail.Characteristic lines at a 70% corrected rotating speed are tested and those with higher rotating speeds will be studied in the near future.Experimental results indicate that boundary layer suction can improve the compressor characteristics and the best suction methodology varies along the operating line.At the near stall condition, suction from the R2 tip region can obviously increase the efficiency and the total pressure ratio, as well as improve the flow capacity.Isentropic efficiency can be maximally increased by 4.24% with an increase of 1.94% in massflow under a suction flow of 160 m3/h.Suction at the R1 position with a suction rate below 0.35% in a high flow situation can make the performance of the compressor better than others.Around the peak efficiency point, boundary layer suction from the slots of OGVs is the best choice in improving the efficiency, but it causes a 0.1% loss in the total pressure ratio.展开更多
In its totality and complexity, the theme of forcing in Christian events is almost impossible to investigate. In fact, a lot of scholars and a very long time would be necessary to analyse the numerous events. Thus, we...In its totality and complexity, the theme of forcing in Christian events is almost impossible to investigate. In fact, a lot of scholars and a very long time would be necessary to analyse the numerous events. Thus, we decided to investigate such events only in the study of the Shroud of Turin, an archaeological find known worldwide. The above topic is essential for Christianity. Furthermore, we must take into account that also among the followers of other religions, atheists and agnostics, there is a considerable interest. We think this is due to the unexpected characteristics that the Body Image, which appears on the Burial Linen of the Nazarene, shows. In this article, we would like to demonstrate that the practice of forcing is still in use. These actions, which are also present on the other side, in the non-Christian world, are the result of conflicts of religious interests. To confirm the presence of the Almighty is not necessarily the forcing. Finding a solution to these problems is not our job. However, we want to highlight them through scientific literature.展开更多
The flow past a circular-section cylinder with a conic shroud perforated with four holes at the peak was simulated numerically at Re = 100, considering two factors, viz.the angle of attack and the diameter of the hole...The flow past a circular-section cylinder with a conic shroud perforated with four holes at the peak was simulated numerically at Re = 100, considering two factors, viz.the angle of attack and the diameter of the holes. The effects of the perforated conic shroud on the vortex shedding pattern in the near wake was mainly investigated, as well as the time history of the drag and lift forces. In the investigated parameter space, three flow regimes were generally identified, corresponding to weak, moderate, and strong disturbance effects.In regime I, the wake can mainly be described by alternately shedding Kármán or Kármán-like vortices. In regime II, the spanwise vortices are obviously disturbed along the span due to the appearance of additional vorticity components and their interactions with the spanwise vortices, but still shed in synchronization along the spanwise direction. In regime III,the typical Kármán vortices partially or totally disappear,and some new vortex shedding patterns appear, such as-type, obliquely shedding, and crossed spanwise vortices with opposite sign. Corresponding to these complex vortex shedding patterns in the near wake, the fluid forces no longer oscillate regularly at a single vortex shedding frequency, but rather with a lower modulation frequency and multiple amplitudes. An overview of these flow regimes is presented.展开更多
Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and asso...Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall. Besides, shroud leakage flow is one of the dominant sources of secondary flow in tur- bomachinery, which not only causes a deterioration of useful work but also a penalty on turbine efficiency. It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution signifi- cantly different to those measured. Even so, the influence of shroud leakage flow is seldom taken into considera- tion during the routine of turbine design due to insufficient understanding of its impact on end wall flows and tur- bine performance. In order to evaluate the impact of tip shroud geometry on turbine performance, a 3D computa- tional investigation for 1.5-stage turbine with shrouded blades was performed in this paper. The following ge- ometry parameters were varied respectively：展开更多
After almost fifteen years, we remind our fellow scientists of the Stochastic process, a natural mechanism for obtaining the Shroud Body Image. The above process is considered the only source of energy present in an a...After almost fifteen years, we remind our fellow scientists of the Stochastic process, a natural mechanism for obtaining the Shroud Body Image. The above process is considered the only source of energy present in an ancient tomb: the thermal one emitted by the corpse of Jesus Christ. It, for all corpses, is notoriously so weak that the only process that could be triggered is the Stochastic one. However, the best-known expert scientists in the Shroud of Turin investigation did not take this model into account, even if it guaranteed a latent image, typical of the Stochastic process, and a fibrils distribution as appears on the Shroud surface. The above scientists and many others had already chosen the Radiative hypothesis, which is based on the emission of radiation (Ultraviolet) and nuclear particles (Protons and Neutrons) by the corpse of Jesus Christ. These emissions are impossible;conversely, if they were true, we would have to talk about miracles. Today, after four decades, it would be appropriate to accept that the Radiative hypothesis (which in the Turin Shroud case becomes a miraculous hypothesis) cannot be in line with both Physics and Theology. We think that we should all be more fiscal when we judge our work.展开更多
基金The project is sponsored by the National Natural Science Foundation of China (No.50274007).
文摘Fine bubbles will create when the inert gas is introduced to the high rapidsteel stream within the shroud nozzle between ladle and tundish. The collision and attachment amongthe bubbles and fine inclusions will promote the floatation efficiency of inclusions in the tundish.The behaviors of the bubbles, such as the dispersion in shroud, coalescence and floatation intundish, are studied. The results show that the maximum sizes of the bubbles in the water and steelflow within the shroud in the length of 1.2 m are 0.70-1.44 mm and 1.53-3.16 mm respectively whenthe flow rates are 0.006-0.016 m^3/s; the terminal velocities of fine bubbles in the water andmolten steel within the tundish are 0.02-0.2 and 0.05-0.6 m/s.
基金Supported by National Natural Science Foundation of China(Grant Nos.51576162,51236006)
文摘Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on the flow characteristics of the hub plate crown is of practical significance. The shroud and hub cavities are respectively studied with regard to tangential and radial velocities at the four different angular positions(0°, 90°, 180°, and 270°) at the four different operational points(0.6 Qsp, 0.8 Qsp, 1.0 Qsp, and 1.2 Qsp). Results indicate that at the same operational point, the smaller the volute chamber sectional area is, the higher the tangential velocity of the fluid core zone of the shroud cavity is. Radial leakage flow from the volute to the seal ring at the same operational point appears in 0° and 90° direction;when the flow is large, the tangential and radial velocities of the shroud and hub cavities with the same radius tend to be equal with axial symmetry. The axial leakage flow through the balance holes significantly affects the radial distribution of both tangential and radial velocities of fluid flow in the hub cavity. The numerical calculation results of fluid leakage through the clearance of back sealing ring are in good agreement with the test results. Accordingly, the magnitude of leakage is closely related to the fluid pressure and velocity distribution in the hub plate crown of the centrifugal pump. The analysis of the flow characteristics in the hub plate crown of the centrifugal pump could reveal the cause of the disc friction loss from the mechanism, providing a significant guidance for improving the accuracy of calculation and balancing the axial thrust in the centrifugal pump.
基金supported by the National Natural Science Foundation of China (No.51236006)Advanced Aeroengine Collaborative Innovation Center
文摘This paper presents the aspirated modification of a dual-stage counter-rotating compressor which contains inlet guide vanes（IGVs）, two counter-rotating rotors（R1, R2）, and outlet guide vanes（OGVs）.Uniform circular holes are circumferentially distributed over the rotors＇ tips on the shroud casing which are designed to remove the low-energy fluid near the shroud casing.OGVs are hollow blades with two slots designed on the suction side which can better control the flow on the suction surface through boundary layer suction.Related works about the experiments have been carried out since June 2012 and the effect of flow suction on the performance of the compressor is investigated in detail.Characteristic lines at a 70% corrected rotating speed are tested and those with higher rotating speeds will be studied in the near future.Experimental results indicate that boundary layer suction can improve the compressor characteristics and the best suction methodology varies along the operating line.At the near stall condition, suction from the R2 tip region can obviously increase the efficiency and the total pressure ratio, as well as improve the flow capacity.Isentropic efficiency can be maximally increased by 4.24% with an increase of 1.94% in massflow under a suction flow of 160 m3/h.Suction at the R1 position with a suction rate below 0.35% in a high flow situation can make the performance of the compressor better than others.Around the peak efficiency point, boundary layer suction from the slots of OGVs is the best choice in improving the efficiency, but it causes a 0.1% loss in the total pressure ratio.
文摘In its totality and complexity, the theme of forcing in Christian events is almost impossible to investigate. In fact, a lot of scholars and a very long time would be necessary to analyse the numerous events. Thus, we decided to investigate such events only in the study of the Shroud of Turin, an archaeological find known worldwide. The above topic is essential for Christianity. Furthermore, we must take into account that also among the followers of other religions, atheists and agnostics, there is a considerable interest. We think this is due to the unexpected characteristics that the Body Image, which appears on the Burial Linen of the Nazarene, shows. In this article, we would like to demonstrate that the practice of forcing is still in use. These actions, which are also present on the other side, in the non-Christian world, are the result of conflicts of religious interests. To confirm the presence of the Almighty is not necessarily the forcing. Finding a solution to these problems is not our job. However, we want to highlight them through scientific literature.
基金supported by the National Key Scientific Instrument and Equipment Development Program of China (Grant 2011YQ120048)
文摘The flow past a circular-section cylinder with a conic shroud perforated with four holes at the peak was simulated numerically at Re = 100, considering two factors, viz.the angle of attack and the diameter of the holes. The effects of the perforated conic shroud on the vortex shedding pattern in the near wake was mainly investigated, as well as the time history of the drag and lift forces. In the investigated parameter space, three flow regimes were generally identified, corresponding to weak, moderate, and strong disturbance effects.In regime I, the wake can mainly be described by alternately shedding Kármán or Kármán-like vortices. In regime II, the spanwise vortices are obviously disturbed along the span due to the appearance of additional vorticity components and their interactions with the spanwise vortices, but still shed in synchronization along the spanwise direction. In regime III,the typical Kármán vortices partially or totally disappear,and some new vortex shedding patterns appear, such as-type, obliquely shedding, and crossed spanwise vortices with opposite sign. Corresponding to these complex vortex shedding patterns in the near wake, the fluid forces no longer oscillate regularly at a single vortex shedding frequency, but rather with a lower modulation frequency and multiple amplitudes. An overview of these flow regimes is presented.
基金Financial support from the Innovation Foundation of BUAA for PhD Graduates(YWF-13-A01-014)
文摘Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall. Besides, shroud leakage flow is one of the dominant sources of secondary flow in tur- bomachinery, which not only causes a deterioration of useful work but also a penalty on turbine efficiency. It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution signifi- cantly different to those measured. Even so, the influence of shroud leakage flow is seldom taken into considera- tion during the routine of turbine design due to insufficient understanding of its impact on end wall flows and tur- bine performance. In order to evaluate the impact of tip shroud geometry on turbine performance, a 3D computa- tional investigation for 1.5-stage turbine with shrouded blades was performed in this paper. The following ge- ometry parameters were varied respectively：
文摘After almost fifteen years, we remind our fellow scientists of the Stochastic process, a natural mechanism for obtaining the Shroud Body Image. The above process is considered the only source of energy present in an ancient tomb: the thermal one emitted by the corpse of Jesus Christ. It, for all corpses, is notoriously so weak that the only process that could be triggered is the Stochastic one. However, the best-known expert scientists in the Shroud of Turin investigation did not take this model into account, even if it guaranteed a latent image, typical of the Stochastic process, and a fibrils distribution as appears on the Shroud surface. The above scientists and many others had already chosen the Radiative hypothesis, which is based on the emission of radiation (Ultraviolet) and nuclear particles (Protons and Neutrons) by the corpse of Jesus Christ. These emissions are impossible;conversely, if they were true, we would have to talk about miracles. Today, after four decades, it would be appropriate to accept that the Radiative hypothesis (which in the Turin Shroud case becomes a miraculous hypothesis) cannot be in line with both Physics and Theology. We think that we should all be more fiscal when we judge our work.
