During screening operation, blinding or clogging of screen perforations generally occurs to reduce the sieving capacity and efficiency. Recently, the flip-flow screening has been widely recognized as a feasible method...During screening operation, blinding or clogging of screen perforations generally occurs to reduce the sieving capacity and efficiency. Recently, the flip-flow screening has been widely recognized as a feasible method to deal with the problem. In this paper, a novel centralized-driving flip-flow screen(CFS) was developed for the separation of fine and moist coal, and the key structures, namely, a centralized-driving mechanism and a quasi-circle beam mounted with the mat were designed for high reliability and stability. By means of a test on an experimental prototype, the effect of some factors, i.e., initial stretch and hardness of the polyurethane panel, respectively, and the rotation speed of the driving motor on the kinematic characteristic of the screen surface was investigated. Results show that without an initial stretch, the sieve mat generates the largest vibratory amplitude while the slacker the sieve mat initially is, the smaller amplitude it will accomplish. And an increase in the rotation speed could cause a rise in the vibratory amplitude. Unlike the two factors, the hardness does not have a definite effect on the kinematic performance, on which a further study is required. Finally, screening processing on a laboratory prototype was conducted to draw the conclusion that the developed CFS also has a high sieving efficiency for the fine and moist coal.展开更多
A numerical model was developed by using the dual boundary element method to investigate the dynamic behavior of a moored floating structure with a pair of vertical and flexible skirts attached at its bottom in the li...A numerical model was developed by using the dual boundary element method to investigate the dynamic behavior of a moored floating structure with a pair of vertical and flexible skirts attached at its bottom in the linear wave field. Theoretical conception is based on potential theory with linear external forces. The motions of the structure were assumed to be small and linear. The flexible skirts mounted beneath the structure were assumed uniform flexural rigidity and the thickness of the skirts was negligible. Comparison between the present model and Gesraha＇s solution was made to verify the results for a moored floating structure with or without rigid skirts. The influence of the skirt rigidity on the moored floating structure, moored lines and waves is investigated in this study. The results show that, the natural frequencies of structure＇s oscillation, moored force, wave reflection and transmission tend to the region of short-period waves when the flexible rigidity gradually decreases. Positive correlation exists between the aft mooring force and the pitch motion of the floating structure.展开更多
The floating photovoltaic membrane prototype developed by Ocean Sun was selected as a reference object,and a 1∶40 scale laboratory model was designed and produced to further explore the impact of inflow conditions on...The floating photovoltaic membrane prototype developed by Ocean Sun was selected as a reference object,and a 1∶40 scale laboratory model was designed and produced to further explore the impact of inflow conditions on the hydrodynamic properties of the membrane structure.By conducting free attenuation tests,results showed that the inflow has only a slight effect on the natural frequencies of the heave,pitch,and surge of the membrane structure.This finding shows that the dynamic properties of the membrane structure remain essentially stable under different inflow conditions.The results of further regular and irregular wave hydrodynamic experiments show that,compared with the control group,the response of the membrane structure under inflow conditions in terms of heave,pitch,surge,and heave acceleration motions is relatively gentle,whereas the response of the membrane structure to the mooring force is strong.Especially when the waves are irregular,the inflow conditions have a more significant impact on the membrane structure,which may lead to more complex response changes in the structure.Therefore,in the actual engineering design process,the impact of inflow conditions on the behavior of the membrane structure must be fully considered,and appropriate engineering measures must be taken to ensure the safety and stability of the structure.展开更多
基金The financial support from the National Natural Science Foundation of China (Nos. 51221462 and 51134022)the Doctoral Programs Foundation of Ministry of Education of China (No. 20120095110001)
文摘During screening operation, blinding or clogging of screen perforations generally occurs to reduce the sieving capacity and efficiency. Recently, the flip-flow screening has been widely recognized as a feasible method to deal with the problem. In this paper, a novel centralized-driving flip-flow screen(CFS) was developed for the separation of fine and moist coal, and the key structures, namely, a centralized-driving mechanism and a quasi-circle beam mounted with the mat were designed for high reliability and stability. By means of a test on an experimental prototype, the effect of some factors, i.e., initial stretch and hardness of the polyurethane panel, respectively, and the rotation speed of the driving motor on the kinematic characteristic of the screen surface was investigated. Results show that without an initial stretch, the sieve mat generates the largest vibratory amplitude while the slacker the sieve mat initially is, the smaller amplitude it will accomplish. And an increase in the rotation speed could cause a rise in the vibratory amplitude. Unlike the two factors, the hardness does not have a definite effect on the kinematic performance, on which a further study is required. Finally, screening processing on a laboratory prototype was conducted to draw the conclusion that the developed CFS also has a high sieving efficiency for the fine and moist coal.
文摘A numerical model was developed by using the dual boundary element method to investigate the dynamic behavior of a moored floating structure with a pair of vertical and flexible skirts attached at its bottom in the linear wave field. Theoretical conception is based on potential theory with linear external forces. The motions of the structure were assumed to be small and linear. The flexible skirts mounted beneath the structure were assumed uniform flexural rigidity and the thickness of the skirts was negligible. Comparison between the present model and Gesraha＇s solution was made to verify the results for a moored floating structure with or without rigid skirts. The influence of the skirt rigidity on the moored floating structure, moored lines and waves is investigated in this study. The results show that, the natural frequencies of structure＇s oscillation, moored force, wave reflection and transmission tend to the region of short-period waves when the flexible rigidity gradually decreases. Positive correlation exists between the aft mooring force and the pitch motion of the floating structure.
基金The National Natural Science Foundation of China(No.52171274).
文摘The floating photovoltaic membrane prototype developed by Ocean Sun was selected as a reference object,and a 1∶40 scale laboratory model was designed and produced to further explore the impact of inflow conditions on the hydrodynamic properties of the membrane structure.By conducting free attenuation tests,results showed that the inflow has only a slight effect on the natural frequencies of the heave,pitch,and surge of the membrane structure.This finding shows that the dynamic properties of the membrane structure remain essentially stable under different inflow conditions.The results of further regular and irregular wave hydrodynamic experiments show that,compared with the control group,the response of the membrane structure under inflow conditions in terms of heave,pitch,surge,and heave acceleration motions is relatively gentle,whereas the response of the membrane structure to the mooring force is strong.Especially when the waves are irregular,the inflow conditions have a more significant impact on the membrane structure,which may lead to more complex response changes in the structure.Therefore,in the actual engineering design process,the impact of inflow conditions on the behavior of the membrane structure must be fully considered,and appropriate engineering measures must be taken to ensure the safety and stability of the structure.
