Flip-flow screens offer unique advantages in grading fine-grained materials.To address inaccuracies caused by sensor vibra-tions in traditional contact measurement methods,we constructed a non-invasive measurement sys...Flip-flow screens offer unique advantages in grading fine-grained materials.To address inaccuracies caused by sensor vibra-tions in traditional contact measurement methods,we constructed a non-invasive measurement system based on electrical and optical sig-nals.A trajectory tracking algorithm for the screen-body was developed to visually measure the kinematics.Employing the principle oflaser reflection for distance measurement,optical techniques were performed to capture the kinematic information of the screen-plate.Ad-ditionally,by using Wi-Fi and Bluetooth transmission of electrical signals,tracer particle tracking technology was implemented to elec-trically measure the kinematic information of mineral particles.Consequently,intelligent fusion and perception of the kinematic informa-tion for the screen-body,screen-plate,and particles in the screening system have been achieved.展开更多
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
The synthetic index K s for evaluating flip-flow screens is proposed and systematically optimized in view of the whole system. A series of optimized values of relevant parameters are found and then compared with those...The synthetic index K s for evaluating flip-flow screens is proposed and systematically optimized in view of the whole system. A series of optimized values of relevant parameters are found and then compared with those of the current industrial specifications. The results show that the optimized value K s approaches the one of those famous flip-flow screens in the world. Some new findings on geometric and kinematics parameters are useful for improving the flip-flow screens with a low K s value, which is helpful in developing clean coal technology.展开更多
Vibrating flip-flow screens are widely used in the field of screening;its actual operation is affected by the impact force of materials,but existing research usually ignores this effect.Based on this background,consid...Vibrating flip-flow screens are widely used in the field of screening;its actual operation is affected by the impact force of materials,but existing research usually ignores this effect.Based on this background,considering the influence of material impact force and moment on vibrating flip-flow screens,this paper develops a dynamic model and a vibration differential equation of a vibrating flip-flow screen,performs the analysis of material movement and calculation of the material impact force,and includes the material impact force in the dynamic characteristic analysis of a vibrating flip-flow screen.The results indicate the following:(1)The impact forces F_(x) and F_(y) account for 29%and 57.58%of the excitation force amplitude,respectively,indicating that they are of the same magnitude as the excitation force.Material impact increases the vibration amplitudes of the main and floating frames,and therefore,cannot be ignored in vibrating flip-flow screen design.(2)By comparing the vibrating flip-flow screen's responses with and without the impact,it is found that impact force significantly influences the system response,causing the displacement curve to shift and the amplitude–frequency curve to have periodic fluctuations and peak values.(3)The effects of impact parameters on the dynamic characteristics of a vibrating flip-flow screen are studied.The results show that increases in material mass and material binding coefficient lead to a decrease in the system natural frequencies.Due to the impact force,the amplitude–frequency curve of the main frame peaks at a frequency lower than the first order of the natural frequency,and the amplitude–frequency curve of the floating frame peaks in the intervals of 5–10Hz and 20–25 Hz.The results provide a theoretical reference for the design of vibrating flip-flow screens.The operating frequency of vibrating flip-flow screens should be selected to avoid the peak value due to the impact force,which helps extend the working life.展开更多
Vibrating flip-flow screens(VFFS)with stretchable polyurethane sieve mats have been widely used in screening fine-grained materials in recent years.In this work,the discrete element method(DEM)is used to study the scr...Vibrating flip-flow screens(VFFS)with stretchable polyurethane sieve mats have been widely used in screening fine-grained materials in recent years.In this work,the discrete element method(DEM)is used to study the screening process in VFFS to explain particle flow and separation behavior at the particle scale.Unlike traditional vibrating screens,for VFFS,the amplitude response of each point on the elastic sieve mat is different everywhere.This study measures the kinematics of the elastic sieve mat under different conditions such as different stretched lengths and material loads.To establish the elastic sieve mat model in a DEM simulation,the continuous elastic sieve mat is discretized into multiple units,and the displacement signal of each unit tested is analyzed by Fourier series.The Fourier series analysis results of each unit are used as the setting parameters for motion.In this way,the movement of the elastic sieve mat is approximately simulated,and a DEM model of VFFS is produced.Through the simulation,the flow and separation of different-sized particles in VFFS are studied,and the reasonability of the simulation is verified by a pilot-scale screening experiment.The present study demonstrates the potential of the DEM method for the analysis of screening processes in VFFS.展开更多
Discrete element method(DEM)is an effective approach for studying the screening process of flip-flow screens.However,there have been few studies focusing on the thick layer of sticky-wet particles on flip-flow screens...Discrete element method(DEM)is an effective approach for studying the screening process of flip-flow screens.However,there have been few studies focusing on the thick layer of sticky-wet particles on flip-flow screens.To achieve accurate simulations of the thick layer of sticky-wet particles on a flip-flow screen,firstly,the movement law of particle flow was studied,and a multi-regime combination cali-bration method based on characteristics of particle flow regimes was proposed.Based on the Plackett-Burman experiment,the curse of dimensionality caused by multi-state and multi-contact parameters was overcome.Subsequently,the lifting cylinder,rotating drum,and trampoline tests were carried out to obtain macroscopic reference values under various granular flow regimes.The calibration results were then determined using the response surface method and climbing algorithm.Finally,the calibration results were tested at both macroscopic and mesoscopic scales and compared with a commonly used calibration method.The results demonstrate that the calibration method,which considers the multi-state characteristics,improves simulation accuracy by 2%-10%and reduces the simulation error to less than 10%,thus meeting the requirements for engineering optimization of flip-flow screens.展开更多
基金financially supported by ChinaNational Funds for Distinguished Young Scientists(No.52125403)National Natural Science Foundation of China(Nos.52261135540 and 52404303)Science and Tech-nology Plan Special Fund Project of Jiangsu Province,China(No.BZ2024046)。
文摘Flip-flow screens offer unique advantages in grading fine-grained materials.To address inaccuracies caused by sensor vibra-tions in traditional contact measurement methods,we constructed a non-invasive measurement system based on electrical and optical sig-nals.A trajectory tracking algorithm for the screen-body was developed to visually measure the kinematics.Employing the principle oflaser reflection for distance measurement,optical techniques were performed to capture the kinematic information of the screen-plate.Ad-ditionally,by using Wi-Fi and Bluetooth transmission of electrical signals,tracer particle tracking technology was implemented to elec-trically measure the kinematic information of mineral particles.Consequently,intelligent fusion and perception of the kinematic informa-tion for the screen-body,screen-plate,and particles in the screening system have been achieved.
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The synthetic index K s for evaluating flip-flow screens is proposed and systematically optimized in view of the whole system. A series of optimized values of relevant parameters are found and then compared with those of the current industrial specifications. The results show that the optimized value K s approaches the one of those famous flip-flow screens in the world. Some new findings on geometric and kinematics parameters are useful for improving the flip-flow screens with a low K s value, which is helpful in developing clean coal technology.
基金supported by the National Natural Science Foundation of China(Grant No.12272259).
文摘Vibrating flip-flow screens are widely used in the field of screening;its actual operation is affected by the impact force of materials,but existing research usually ignores this effect.Based on this background,considering the influence of material impact force and moment on vibrating flip-flow screens,this paper develops a dynamic model and a vibration differential equation of a vibrating flip-flow screen,performs the analysis of material movement and calculation of the material impact force,and includes the material impact force in the dynamic characteristic analysis of a vibrating flip-flow screen.The results indicate the following:(1)The impact forces F_(x) and F_(y) account for 29%and 57.58%of the excitation force amplitude,respectively,indicating that they are of the same magnitude as the excitation force.Material impact increases the vibration amplitudes of the main and floating frames,and therefore,cannot be ignored in vibrating flip-flow screen design.(2)By comparing the vibrating flip-flow screen's responses with and without the impact,it is found that impact force significantly influences the system response,causing the displacement curve to shift and the amplitude–frequency curve to have periodic fluctuations and peak values.(3)The effects of impact parameters on the dynamic characteristics of a vibrating flip-flow screen are studied.The results show that increases in material mass and material binding coefficient lead to a decrease in the system natural frequencies.Due to the impact force,the amplitude–frequency curve of the main frame peaks at a frequency lower than the first order of the natural frequency,and the amplitude–frequency curve of the floating frame peaks in the intervals of 5–10Hz and 20–25 Hz.The results provide a theoretical reference for the design of vibrating flip-flow screens.The operating frequency of vibrating flip-flow screens should be selected to avoid the peak value due to the impact force,which helps extend the working life.
基金supported by the Fundamental Research Funds for the Central Universities (grant No.2021YJSHH32)Anhui Province Major Science and Technology Achievements Engineering Research and Development Special Project (grant No.202103c08020007).
文摘Vibrating flip-flow screens(VFFS)with stretchable polyurethane sieve mats have been widely used in screening fine-grained materials in recent years.In this work,the discrete element method(DEM)is used to study the screening process in VFFS to explain particle flow and separation behavior at the particle scale.Unlike traditional vibrating screens,for VFFS,the amplitude response of each point on the elastic sieve mat is different everywhere.This study measures the kinematics of the elastic sieve mat under different conditions such as different stretched lengths and material loads.To establish the elastic sieve mat model in a DEM simulation,the continuous elastic sieve mat is discretized into multiple units,and the displacement signal of each unit tested is analyzed by Fourier series.The Fourier series analysis results of each unit are used as the setting parameters for motion.In this way,the movement of the elastic sieve mat is approximately simulated,and a DEM model of VFFS is produced.Through the simulation,the flow and separation of different-sized particles in VFFS are studied,and the reasonability of the simulation is verified by a pilot-scale screening experiment.The present study demonstrates the potential of the DEM method for the analysis of screening processes in VFFS.
基金supported by the Anhui Province Major Science and Technology Achievements Engineering Research and Development Special Project(grant No.202103c08020007)the Fundamental Research Funds for the Central Universities(grant No.2022YJSHH15).
文摘Discrete element method(DEM)is an effective approach for studying the screening process of flip-flow screens.However,there have been few studies focusing on the thick layer of sticky-wet particles on flip-flow screens.To achieve accurate simulations of the thick layer of sticky-wet particles on a flip-flow screen,firstly,the movement law of particle flow was studied,and a multi-regime combination cali-bration method based on characteristics of particle flow regimes was proposed.Based on the Plackett-Burman experiment,the curse of dimensionality caused by multi-state and multi-contact parameters was overcome.Subsequently,the lifting cylinder,rotating drum,and trampoline tests were carried out to obtain macroscopic reference values under various granular flow regimes.The calibration results were then determined using the response surface method and climbing algorithm.Finally,the calibration results were tested at both macroscopic and mesoscopic scales and compared with a commonly used calibration method.The results demonstrate that the calibration method,which considers the multi-state characteristics,improves simulation accuracy by 2%-10%and reduces the simulation error to less than 10%,thus meeting the requirements for engineering optimization of flip-flow screens.
