The Daharan Dam, like other dams, is subject to concrete surface wear or cavitation in the chute structure. This article looks into the concurrent effects of decreasing the chute angle and slope profile changes from a...The Daharan Dam, like other dams, is subject to concrete surface wear or cavitation in the chute structure. This article looks into the concurrent effects of decreasing the chute angle and slope profile changes from a single slope to a double slope and the simultaneous latitudinal convergence of the chute structure on the cavitation index and the economy of project. In order to perform this research, the geometric specifications were collected of the dam, and the chute structure as well as those of a flood with a return period of 1000 years, which make up the basis of the spillway design. Taking advantage of the numerical WS77 model, different modes were simulated with a single slope, double slope with fixed latitude, double slope with latitudinal convergence, and the cavitation index and the excavation volumes for each option were calculated. The results indicated that a decrease in slope led to a rise in the cavitation index to over 1.2 and that the convergence of the chute structure positively affected the increase in the cavitation index.展开更多
Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river,but it significantly changes its morphodynamic characteristics.Channel adjustments after cutoff are rapid,which ma...Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river,but it significantly changes its morphodynamic characteristics.Channel adjustments after cutoff are rapid,which makes it difficult to study the interaction between river morphology and flow structure only through field measurement.However,numerical simulations can provide insights into the hydrodynamic characteristics after artificial chute cutoffs.In this study,both field measurement and numerical simulation are employed to investigate the flow structure and bed morphology caused by an artificial chute cutoff in Sipaikou area of the Upper Yellow River in 2018.The measured hydrological data provide boundary conditions and initial values for the numerical model.The field measurement results reveal that the concave bank of the study area is severely scoured up to 270 m after the artificial cutoff,and a 20 m deep scour hole and a 2.26 km long pool are formed at the entrance and near the left bank of the chute channel.The numerical simulation results of velocity at typical cross-sections are in good agreement with the measurement results.Flow separation and stagnation zones are observed near the right bank during the low flow conditions(discharge of at least 902 m^(3)/s),but this phenomenon is not seen during larger flow conditions(discharge exceeds 2000 m^(3)/s).Interestingly,flow recirculation zones are also found near the left and right banks of the scour hole.Further,a long flux belt is formed at the scour hole and the pool.Consequently,the impact of the bed topography on the hydrodynamic characteristics is relatively prominent when the discharge is small,while the impact on the river banks and river bed is more noticeable when the water discharge is large.In addition,high shear stress is observed near the left bank at the downstream of the studied area,which indicates that the left bank at the downstream is still being scoured.These results suggest that bank protection measures along the left bank are required to maintain the effectiveness of the artificial chute cutoff.展开更多
For the bell-less top blast furnace, when particles move along the chute, the particlesr motion direction and the frictional force acting on them will change due to the chute rotation, which consequently influences th...For the bell-less top blast furnace, when particles move along the chute, the particlesr motion direction and the frictional force acting on them will change due to the chute rotation, which consequently influences the velocity at the tip of chute, changes the burden flow width and impact point, and finally affects the stock profile and gas f[ow distribution. So the influence of chute rotation needs to be considered when calculating the burden trajectory with a mathematical model. The mathematical model was established to analyze the influence of Coriolis force on particle velocity at chute tip as well as height and width of burden flow in chute, and to summarize the effect of Coriolis force on burden distribution, thereby making the calculation result more accurate.展开更多
Based on the structure of chute - feed and autoleveHer, an analysis of their working principle and the verification of their practical production results have been carried out. Finally, the future investigation direet...Based on the structure of chute - feed and autoleveHer, an analysis of their working principle and the verification of their practical production results have been carried out. Finally, the future investigation direetiom of chute - feed and card autuleveller are put forward.展开更多
In particulate material transfer systems,traditional shear test based steady state analysis can provide some insight into the strength of the bulk material and subsequent resistive frictional forces during flow.For fa...In particulate material transfer systems,traditional shear test based steady state analysis can provide some insight into the strength of the bulk material and subsequent resistive frictional forces during flow.For fast flowing transfer points,dynamic flow conditions dominate and additional modelling techniques are required to improve design guidance.The research presented shows the evolution of a design solution which utilises two distinct processes;a continuum method and a discrete element method(DEM). Initially,the internal structure of dense granular flow,down vertical and inclined pipes was investigated using a twin sensor,12 electrode electrical capacitance tomography device.Subsequently,DEM simulations were conducted using the commercial software,PFC3D.Initially,two particle types and their flow behaviours were analysed:plastic pellets and sand.The pipe angle was varied between 0°and 45°to the vertical.For both the plastic pellets and the sand,good qualitative agreement was found with the spatial particle concentration analysis.Generally,the flow had a dense particle region at its core with the particle concentration reducing away from this core.As expected,at 0°, the core was centrally located within the pipe for both the plastic pellets and sand.At pipe angles 5°or greater,the dense core of particles was located on or near the pipe wall.Average flow velocity analysis was also conducted using the results of wall friction test analysis.The velocity comparisons also showed good agreement between the ECT image analysis and the DEM simulations. Subsequently,the DEM method was used to analyse a complex transfer system(or chute) with the continuum method providing comparative flow analysis with the DEM flow analysis.展开更多
This study describes a model-directed experimental approach toward the measurement of dense granular rheology.It used a concentric cylinder rheometer tilted along an axis,essentially a chute flow where applied shear c...This study describes a model-directed experimental approach toward the measurement of dense granular rheology.It used a concentric cylinder rheometer tilted along an axis,essentially a chute flow where applied shear can further affect the continuous dense flow of granular media.Experiments were done using draining flows over a range of shear rates imposed by the concentric rotor within the device.Multiple sensors were used to investigate the interaction of mass holdup,shear rate,specific torque,particle velocity,and discharge mass flow rate.A linear range was observed wherein the specific torque and mass flow rate remained steady during draining.The flow rate,specific torque,and particle speed measurements increased with increasing rotor speed.The relative variance of the mass flow rate was found to be proportional to the temporal scale of scrutiny;it decreased at higher shear rates for short time intervals.Wall slip at the rotor was inferred from particle velocity measurements.With increasing shear rate,gradual increases in flow rate were observed combined with increased specific torque and wall slip.A sharp transition between quasi-static and dense-inertial regimes was not observed with this device;instead,the observed increase in specific torque was gradual with an apparent asymptotic limit,suggesting a pump-curve analogy where the outlet mass flow rate was controlled as a function of orthogonal shear.展开更多
Rotating chutes are widely used to control the burden distribution and enhance the gas distribution in a blast furnace.The chute cross-section shape has a significant effect on the particle movement and distribution.T...Rotating chutes are widely used to control the burden distribution and enhance the gas distribution in a blast furnace.The chute cross-section shape has a significant effect on the particle movement and distribution.Therefore,this study developed a three-dimensional model of a blast furnace top with rotating chute using the discrete element method.The effect of different chute shapes on the particle movement and radial burden distribution was then investigated.The results showed that the burden stream height at the chute discharge agrees well with the burden stream thickness at the burden surface.A semicircular chute had the largest main striking point,where the chute discharge joins the burden surface,and trapezoidal and rectangular chutes had successively smaller MSPs.The semicircular chute helped to obtain a uniform radial size distribution.The trapezoidal chute helped form an aggregated burden stream at low rotating speeds,while the rectangular shape chute achieved this at higher rotating speeds and different chute angles.展开更多
The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of ex...The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of external information;hence,it is especially suitable for measuring the angular and translational velocities of internal characteristic particles.To study the influence of the end wall of the chute on the motions of the internal characteristic particles,the z-axis rotational and translational velocities of the internal characteristic particles in the chute were measured,and it was found that the rotational velocity about the z-axis differs according to the initial position.The z-axis angular velocity of a characteristic particle at the centre fluctuates near 0,and the average value approaches 0.The z-axis angular velocity of a characteristic particle at the left end wall is typically negative.This phenomenon is due to the influence of the end wall on the rotational motions of particles with initial positions that are near the end wall.In addition,the average translational velocity of the characteristic particles is also affected by the end wall.The distributions of the average z-axis angular velocity and the average translational velocity are quantitatively analysed,and the correlation between the tilt angle of the chute and the end wall effect is studied.展开更多
The chute aerators separate the flow from the chute bottom,and the air can enter into the flow through the lower surface.In this study,the air concentration and the pressure along the chute bottom are investigated sys...The chute aerators separate the flow from the chute bottom,and the air can enter into the flow through the lower surface.In this study,the air concentration and the pressure along the chute bottom are investigated systematically by a series of model tests with the upper aeration effect being eliminated.The chute downstream the aerator is partitioned into four zones:the cavity zone,the impact zone,the equilibrium zone,and the far zone.It is found that a large amount of air entrained in the cavity zone is only partially entrained into the flow finally.Furthermore,the lower air discharge is decreased sharply in the impact zone,and the detrainment disappearsonthe section of x= Lm.In the equilibrium zone,the lower air discharge is kept unchanged.With the in crease of the flow Froude number and withthe other parameters kept unchanged,it is found that the dimensionless value of K has a significant increase.Meanwhile,a formula to calculate K is proposed,with results in good agreement with the model and prototype data.展开更多
The formulae used to calculate the friction in the non uniform flow chute were examined with the experimental data, and the results show that the accuracy of the formula is enough for engineering applications. A comp...The formulae used to calculate the friction in the non uniform flow chute were examined with the experimental data, and the results show that the accuracy of the formula is enough for engineering applications. A comparison between the results of friction respectively from the uniform flow assumption and the non uniform flow approximation indicates that the former is an order of magnitude larger than the latter in the case of steep chute. The hydraulic drag on a steep chute with aerators was measured on the hydraulic model directly and the coefficient of the aerator effect on the drag was obtained. The variation patterns of the wall shear just downstream of the aerators were investigated and the mechanism of the increase in the drag by aerator were analyzed qualitatively with the measured water depths just downstream the aerators.展开更多
文摘The Daharan Dam, like other dams, is subject to concrete surface wear or cavitation in the chute structure. This article looks into the concurrent effects of decreasing the chute angle and slope profile changes from a single slope to a double slope and the simultaneous latitudinal convergence of the chute structure on the cavitation index and the economy of project. In order to perform this research, the geometric specifications were collected of the dam, and the chute structure as well as those of a flood with a return period of 1000 years, which make up the basis of the spillway design. Taking advantage of the numerical WS77 model, different modes were simulated with a single slope, double slope with fixed latitude, double slope with latitudinal convergence, and the cavitation index and the excavation volumes for each option were calculated. The results indicated that a decrease in slope led to a rise in the cavitation index to over 1.2 and that the convergence of the chute structure positively affected the increase in the cavitation index.
基金This work was supported mainly by the National Natural Science Foundation of China(Grants No.11761005 and 11861003)partly supported by Key Research&Development Plan Projects of the Science and Technology Department of Ningxia Autonomous Region(Grant No.2019BEG03048)+1 种基金the Natural Science Foundation of Ningxia Province(Grants No.2021AAC03096,2021AAC03206 and 2020AAC03254)Science Research Project of Ningxia(Grant No.NGY2020009).
文摘Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river,but it significantly changes its morphodynamic characteristics.Channel adjustments after cutoff are rapid,which makes it difficult to study the interaction between river morphology and flow structure only through field measurement.However,numerical simulations can provide insights into the hydrodynamic characteristics after artificial chute cutoffs.In this study,both field measurement and numerical simulation are employed to investigate the flow structure and bed morphology caused by an artificial chute cutoff in Sipaikou area of the Upper Yellow River in 2018.The measured hydrological data provide boundary conditions and initial values for the numerical model.The field measurement results reveal that the concave bank of the study area is severely scoured up to 270 m after the artificial cutoff,and a 20 m deep scour hole and a 2.26 km long pool are formed at the entrance and near the left bank of the chute channel.The numerical simulation results of velocity at typical cross-sections are in good agreement with the measurement results.Flow separation and stagnation zones are observed near the right bank during the low flow conditions(discharge of at least 902 m^(3)/s),but this phenomenon is not seen during larger flow conditions(discharge exceeds 2000 m^(3)/s).Interestingly,flow recirculation zones are also found near the left and right banks of the scour hole.Further,a long flux belt is formed at the scour hole and the pool.Consequently,the impact of the bed topography on the hydrodynamic characteristics is relatively prominent when the discharge is small,while the impact on the river banks and river bed is more noticeable when the water discharge is large.In addition,high shear stress is observed near the left bank at the downstream of the studied area,which indicates that the left bank at the downstream is still being scoured.These results suggest that bank protection measures along the left bank are required to maintain the effectiveness of the artificial chute cutoff.
基金Item Sponsored by National Natural Science Foundation of China(60872147)
文摘For the bell-less top blast furnace, when particles move along the chute, the particlesr motion direction and the frictional force acting on them will change due to the chute rotation, which consequently influences the velocity at the tip of chute, changes the burden flow width and impact point, and finally affects the stock profile and gas f[ow distribution. So the influence of chute rotation needs to be considered when calculating the burden trajectory with a mathematical model. The mathematical model was established to analyze the influence of Coriolis force on particle velocity at chute tip as well as height and width of burden flow in chute, and to summarize the effect of Coriolis force on burden distribution, thereby making the calculation result more accurate.
文摘Based on the structure of chute - feed and autoleveHer, an analysis of their working principle and the verification of their practical production results have been carried out. Finally, the future investigation direetiom of chute - feed and card autuleveller are put forward.
文摘In particulate material transfer systems,traditional shear test based steady state analysis can provide some insight into the strength of the bulk material and subsequent resistive frictional forces during flow.For fast flowing transfer points,dynamic flow conditions dominate and additional modelling techniques are required to improve design guidance.The research presented shows the evolution of a design solution which utilises two distinct processes;a continuum method and a discrete element method(DEM). Initially,the internal structure of dense granular flow,down vertical and inclined pipes was investigated using a twin sensor,12 electrode electrical capacitance tomography device.Subsequently,DEM simulations were conducted using the commercial software,PFC3D.Initially,two particle types and their flow behaviours were analysed:plastic pellets and sand.The pipe angle was varied between 0°and 45°to the vertical.For both the plastic pellets and the sand,good qualitative agreement was found with the spatial particle concentration analysis.Generally,the flow had a dense particle region at its core with the particle concentration reducing away from this core.As expected,at 0°, the core was centrally located within the pipe for both the plastic pellets and sand.At pipe angles 5°or greater,the dense core of particles was located on or near the pipe wall.Average flow velocity analysis was also conducted using the results of wall friction test analysis.The velocity comparisons also showed good agreement between the ECT image analysis and the DEM simulations. Subsequently,the DEM method was used to analyse a complex transfer system(or chute) with the continuum method providing comparative flow analysis with the DEM flow analysis.
文摘This study describes a model-directed experimental approach toward the measurement of dense granular rheology.It used a concentric cylinder rheometer tilted along an axis,essentially a chute flow where applied shear can further affect the continuous dense flow of granular media.Experiments were done using draining flows over a range of shear rates imposed by the concentric rotor within the device.Multiple sensors were used to investigate the interaction of mass holdup,shear rate,specific torque,particle velocity,and discharge mass flow rate.A linear range was observed wherein the specific torque and mass flow rate remained steady during draining.The flow rate,specific torque,and particle speed measurements increased with increasing rotor speed.The relative variance of the mass flow rate was found to be proportional to the temporal scale of scrutiny;it decreased at higher shear rates for short time intervals.Wall slip at the rotor was inferred from particle velocity measurements.With increasing shear rate,gradual increases in flow rate were observed combined with increased specific torque and wall slip.A sharp transition between quasi-static and dense-inertial regimes was not observed with this device;instead,the observed increase in specific torque was gradual with an apparent asymptotic limit,suggesting a pump-curve analogy where the outlet mass flow rate was controlled as a function of orthogonal shear.
基金This work was supported by the China Postdoctoral Science Foundation (Grants 2016M591076 and 2017M610769)Fundamental Research Funds for the Central Universities (Grant FRF-TP-15-065A1 and FRF-TP-17-035A2).
文摘Rotating chutes are widely used to control the burden distribution and enhance the gas distribution in a blast furnace.The chute cross-section shape has a significant effect on the particle movement and distribution.Therefore,this study developed a three-dimensional model of a blast furnace top with rotating chute using the discrete element method.The effect of different chute shapes on the particle movement and radial burden distribution was then investigated.The results showed that the burden stream height at the chute discharge agrees well with the burden stream thickness at the burden surface.A semicircular chute had the largest main striking point,where the chute discharge joins the burden surface,and trapezoidal and rectangular chutes had successively smaller MSPs.The semicircular chute helped to obtain a uniform radial size distribution.The trapezoidal chute helped form an aggregated burden stream at low rotating speeds,while the rectangular shape chute achieved this at higher rotating speeds and different chute angles.
基金This work has been supported by the National Natural Science Foundation of China(91634202,11902190).
文摘The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of external information;hence,it is especially suitable for measuring the angular and translational velocities of internal characteristic particles.To study the influence of the end wall of the chute on the motions of the internal characteristic particles,the z-axis rotational and translational velocities of the internal characteristic particles in the chute were measured,and it was found that the rotational velocity about the z-axis differs according to the initial position.The z-axis angular velocity of a characteristic particle at the centre fluctuates near 0,and the average value approaches 0.The z-axis angular velocity of a characteristic particle at the left end wall is typically negative.This phenomenon is due to the influence of the end wall on the rotational motions of particles with initial positions that are near the end wall.In addition,the average translational velocity of the characteristic particles is also affected by the end wall.The distributions of the average z-axis angular velocity and the average translational velocity are quantitatively analysed,and the correlation between the tilt angle of the chute and the end wall effect is studied.
基金the National Key Research and Development Program (Grant No.2016YFC0401707)the National Natural Science Foundation of China (Grant Nos.51709293,51479129).
文摘The chute aerators separate the flow from the chute bottom,and the air can enter into the flow through the lower surface.In this study,the air concentration and the pressure along the chute bottom are investigated systematically by a series of model tests with the upper aeration effect being eliminated.The chute downstream the aerator is partitioned into four zones:the cavity zone,the impact zone,the equilibrium zone,and the far zone.It is found that a large amount of air entrained in the cavity zone is only partially entrained into the flow finally.Furthermore,the lower air discharge is decreased sharply in the impact zone,and the detrainment disappearsonthe section of x= Lm.In the equilibrium zone,the lower air discharge is kept unchanged.With the in crease of the flow Froude number and withthe other parameters kept unchanged,it is found that the dimensionless value of K has a significant increase.Meanwhile,a formula to calculate K is proposed,with results in good agreement with the model and prototype data.
文摘The formulae used to calculate the friction in the non uniform flow chute were examined with the experimental data, and the results show that the accuracy of the formula is enough for engineering applications. A comparison between the results of friction respectively from the uniform flow assumption and the non uniform flow approximation indicates that the former is an order of magnitude larger than the latter in the case of steep chute. The hydraulic drag on a steep chute with aerators was measured on the hydraulic model directly and the coefficient of the aerator effect on the drag was obtained. The variation patterns of the wall shear just downstream of the aerators were investigated and the mechanism of the increase in the drag by aerator were analyzed qualitatively with the measured water depths just downstream the aerators.
