As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively high...As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeUer blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.展开更多
Relative contact angle and heat of wetting can be used to provide a measurement of surface wettability of synthetic magnetite. The comparison between synthetic and natural magnetite in terms of surface wettability sho...Relative contact angle and heat of wetting can be used to provide a measurement of surface wettability of synthetic magnetite. The comparison between synthetic and natural magnetite in terms of surface wettability showed that, using the same kind of wetting liquid, the difference in the relative contact angle was 10° between the concentrate and tailings obtained from reverse fl otation of synthetic magnetite, while the difference was more than 20° between the concentrate and tailings obtained from reverse fl otation of natural magnetite. As for the concentrate and tailings from reverse fl otation of synthetic magnetite with water as wetting liquid, the relative ratio of their wetting heat was 106.21%. In comparison, the relative ratio of wetting heat was 176.59% for concentrate and tailings from reverse fl otation of natural magnetite, showing a 70.38% difference.展开更多
In this work,we propose multiple rotation averaging using only the relative rotation angle,which is a straightforward camera pose optimization method.We use the axis-angle representation to parameterize the rotation a...In this work,we propose multiple rotation averaging using only the relative rotation angle,which is a straightforward camera pose optimization method.We use the axis-angle representation to parameterize the rotation and use only relative rotation angles to constrain absolute rotations instead of complete relative rotations.When used with an inertial measurement unit(IMU),our method can obviate the need to estimate and maintain extrinsic parameters between the camera and IMU.This advantage makes our method immune to extrinsic parameters and flexible.We performed extensive evaluations on both synthetic data and publicly available real datasets,which showed that our method was comparable with the state-of-the-art method and achieved a significant gain in accuracy for the visual measurement when applied to the case in which the camera and IMU are tightly fixed.展开更多
To recognize the boundary of wireless networks to meet some specific needs, relative azimuth angles of nodes distributed in the 1-hop neighborhood of each node in one network were used to recognize the boundary of the...To recognize the boundary of wireless networks to meet some specific needs, relative azimuth angles of nodes distributed in the 1-hop neighborhood of each node in one network were used to recognize the boundary of the network. A novel recognition algorithm based on local generalized convex hull was proposed for one node to decide if it self is a boundary node. The flexibility, efficiency and consistency of the algorithm are shown in its performance by extensive simulations.展开更多
This paper is concerned with a scenario of multiple attackers trying to intercept a target with active defense.Three types of agents are considered in the guidance:The multiple attackers,the target and the defender,wh...This paper is concerned with a scenario of multiple attackers trying to intercept a target with active defense.Three types of agents are considered in the guidance:The multiple attackers,the target and the defender,where the attackers aim to pursuit the target from different directions and evade from the defender simultaneously.The guidance engagement is formulated in the framework of a zero-sum two-person differential game between the two opposing teams,such that the measurements on the maneuver of the target or estimations on the defending strategy of the defender can be absent.Cooperation of the attackers resides in two aspects:redundant interception under the threat of the defender and the relative intercept geometry with the target.The miss distances,the relative intercept angle errors and the costs of the agents are combined into a single performance index of the game.Such formulation enables a unitary approach to the design of guidance laws for the agents.To minimize the control efforts and miss distances for the attackers,an optimization method is proposed to find the best anticipated miss distances to the defender under the constraint that the defender is endowed with a capture radius.Numerical simulations with two cases are conducted to illustrate the effectiveness of the proposed cooperative guidance law.展开更多
With the growing demand for energy saving,emission reduction,and green metallurgy,we had designed a new C-H2 smelting reduction reactor.In order to solve the key problem that the heat transfer efficiency from high tem...With the growing demand for energy saving,emission reduction,and green metallurgy,we had designed a new C-H2 smelting reduction reactor.In order to solve the key problem that the heat transfer efficiency from high temperature oxidation zone in upper region to low temperature reduction zone in lower region is low in traditional metallurgical reduction reactor,a water simulation was adopted to optimize the mean residence time and to improve the transmission efficiency within the reactor.According to the modified Froude similarity,a water model experimental reactor with a ratio of 1:1 to the prototype was constructed.In the prototype,the feed port was used to feed preheated ore and flux.In order to simulate the effect of different feeding positions of the tracer on the mixing behavior in the molten pool,four points of tracer feeding position were arranged for a systematic study.At the same time,based on double-row side nozzle with thick slag layer in a C-H2 smelting reduction reactor,nine influencing factors,including relative angle between upper and lower side nozzles,were studied.The experimental results showed that the tracer feeding position had a great influence on the mean residence time,and the relative angle also had a great influence on tracer feeding position.Finally,through comprehensive analysis,the optimal condition parameters were obtained under different tracer feeding positions.These results provide valuable help for the design and optimization of the C-H2 smelting reduction reactor.展开更多
A turbocharger compressor working in commercial vehicles, especially in some passenger cars, often works together with some pipes with complicated geometry as an air intake system, due to limit of available space in i...A turbocharger compressor working in commercial vehicles, especially in some passenger cars, often works together with some pipes with complicated geometry as an air intake system, due to limit of available space in internal combustion engine compartments. These pipes may generate various distortions of physical parameters of the air at the inlet of the compressor and therefore the compressor aerodynamic performance deteriorates. Sometimes, the turbocharging engine fails to work at some operation points. This paper investigates the effects of various swirl distortions induced by different bending-torsional intake ducts on the aerodynamic performance of a turbocharger compressor by both 3D numerical simulations and experimental measurements. It was found that at the outlet of the pipes the different inlet ducts can generate different swirl distortions, twin vortices and bulk-like vortices with different rotating directions. Among them, the bulk-like vortices not only affect seriously the pressure distribution in the impeller domain, but also significantly deteriorate the compressor performance, especially at high flow rate region. And the rotating direction of the bulk-like vortices is also closely associated with the efficiency penalty. Besides the efficiency, the transient flow rate through a single impeller channel, or the asymmetric mass flow crossing the whole impeller, can be influenced by two disturbances. One is from the upstream bending-torsional ducts; other one is from the downstream volute.展开更多
The cold fluid flowing over two hot spheroids placed in a tandem arrangement was numerically studied via a GPU-based immersed boundary-lattice Boltzmann method(IB-LBM)model.The drag coefficient and average Nusselt num...The cold fluid flowing over two hot spheroids placed in a tandem arrangement was numerically studied via a GPU-based immersed boundary-lattice Boltzmann method(IB-LBM)model.The drag coefficient and average Nusselt number of both the two spheroids were obtained with the main influencing factors investigated.To validate the IB-LBM model,several numerical case studies containing one and two spheres were firstly conducted to reach the good agreement with the previously reported data.Then,a number of simulations were further carried out which were designed by changing the particle aspect ratio(1.0≤Ar≤4.0)and inter particle distance(1.5≤ι≤7.0,whereι=L/D,D stands for the volume-equivalent sphere diameter)as well as the Reynolds number(10≤Re≤200).Their influence on the momentum and heat transfer characteristics between the solid and fluid phases was fully discussed.Numerical results show that,for all the considered Reynolds numbers and aspect ratios,the individual and total drag coefficients and average Nusselt number increase with the inter particle distance.The inter particle distance has greater influence on the drag coefficient and average Nusselt number of the trailing particle than the leading one.The drag coefficient and average Nusselt number of the trailing particle are far less than the leading one under the same working conditions.The prediction correlations for the drag coefficient and average Nusselt number of both the two spheroids were established with low deviations.At last,the influence of the relative incidence angles between the two tandem spheroids on the momentum and heat transfer was studied.It is shown that the relative incidence angles play significant roles due to the change of the frontal area of the leading spheroid with these angles.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51239005)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeUer blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.
基金Funded by the National Natural Science Foundation of China(No.51144003)
文摘Relative contact angle and heat of wetting can be used to provide a measurement of surface wettability of synthetic magnetite. The comparison between synthetic and natural magnetite in terms of surface wettability showed that, using the same kind of wetting liquid, the difference in the relative contact angle was 10° between the concentrate and tailings obtained from reverse fl otation of synthetic magnetite, while the difference was more than 20° between the concentrate and tailings obtained from reverse fl otation of natural magnetite. As for the concentrate and tailings from reverse fl otation of synthetic magnetite with water as wetting liquid, the relative ratio of their wetting heat was 106.21%. In comparison, the relative ratio of wetting heat was 176.59% for concentrate and tailings from reverse fl otation of natural magnetite, showing a 70.38% difference.
基金Hunan Provincial Natural Science Foundation for Excellent Young Scholars(Grant No.2023JJ20045)in part by the Science Foundation(Grant Nos.KY0505072204 and GJSD22006)。
文摘In this work,we propose multiple rotation averaging using only the relative rotation angle,which is a straightforward camera pose optimization method.We use the axis-angle representation to parameterize the rotation and use only relative rotation angles to constrain absolute rotations instead of complete relative rotations.When used with an inertial measurement unit(IMU),our method can obviate the need to estimate and maintain extrinsic parameters between the camera and IMU.This advantage makes our method immune to extrinsic parameters and flexible.We performed extensive evaluations on both synthetic data and publicly available real datasets,which showed that our method was comparable with the state-of-the-art method and achieved a significant gain in accuracy for the visual measurement when applied to the case in which the camera and IMU are tightly fixed.
文摘To recognize the boundary of wireless networks to meet some specific needs, relative azimuth angles of nodes distributed in the 1-hop neighborhood of each node in one network were used to recognize the boundary of the network. A novel recognition algorithm based on local generalized convex hull was proposed for one node to decide if it self is a boundary node. The flexibility, efficiency and consistency of the algorithm are shown in its performance by extensive simulations.
基金supported by the Science and Technology Innovation 2030-Key Project of “New Generation Artificial Intelligence”,China(No.2020AAA0108200)the National Natural Science Foundation of China(Nos.61873011,61922008,61973013 and 61803014)+3 种基金the Defense Industrial Technology Development Program,China(No.JCKY2019601C106)the Innovation Zone Project,China(No.18-163-00-TS-001-00134)the Foundation Strengthening Program Technology Field Fund,China(No.2019-JCJQ-JJ-243)the Fund from Key Laboratory of Dependable Service Computing in Cyber Physical Society,China(No.CPSDSC202001)。
文摘This paper is concerned with a scenario of multiple attackers trying to intercept a target with active defense.Three types of agents are considered in the guidance:The multiple attackers,the target and the defender,where the attackers aim to pursuit the target from different directions and evade from the defender simultaneously.The guidance engagement is formulated in the framework of a zero-sum two-person differential game between the two opposing teams,such that the measurements on the maneuver of the target or estimations on the defending strategy of the defender can be absent.Cooperation of the attackers resides in two aspects:redundant interception under the threat of the defender and the relative intercept geometry with the target.The miss distances,the relative intercept angle errors and the costs of the agents are combined into a single performance index of the game.Such formulation enables a unitary approach to the design of guidance laws for the agents.To minimize the control efforts and miss distances for the attackers,an optimization method is proposed to find the best anticipated miss distances to the defender under the constraint that the defender is endowed with a capture radius.Numerical simulations with two cases are conducted to illustrate the effectiveness of the proposed cooperative guidance law.
基金This study was funded by the National Science and Technology Support Program(2006BAE03A12).
文摘With the growing demand for energy saving,emission reduction,and green metallurgy,we had designed a new C-H2 smelting reduction reactor.In order to solve the key problem that the heat transfer efficiency from high temperature oxidation zone in upper region to low temperature reduction zone in lower region is low in traditional metallurgical reduction reactor,a water simulation was adopted to optimize the mean residence time and to improve the transmission efficiency within the reactor.According to the modified Froude similarity,a water model experimental reactor with a ratio of 1:1 to the prototype was constructed.In the prototype,the feed port was used to feed preheated ore and flux.In order to simulate the effect of different feeding positions of the tracer on the mixing behavior in the molten pool,four points of tracer feeding position were arranged for a systematic study.At the same time,based on double-row side nozzle with thick slag layer in a C-H2 smelting reduction reactor,nine influencing factors,including relative angle between upper and lower side nozzles,were studied.The experimental results showed that the tracer feeding position had a great influence on the mean residence time,and the relative angle also had a great influence on tracer feeding position.Finally,through comprehensive analysis,the optimal condition parameters were obtained under different tracer feeding positions.These results provide valuable help for the design and optimization of the C-H2 smelting reduction reactor.
基金sponsored by the Key Projects of Hebei Provincial Department of Education(No.ZD2016095)the Program of Science and Technology Research and Development of Handan(1621212047-2)
文摘A turbocharger compressor working in commercial vehicles, especially in some passenger cars, often works together with some pipes with complicated geometry as an air intake system, due to limit of available space in internal combustion engine compartments. These pipes may generate various distortions of physical parameters of the air at the inlet of the compressor and therefore the compressor aerodynamic performance deteriorates. Sometimes, the turbocharging engine fails to work at some operation points. This paper investigates the effects of various swirl distortions induced by different bending-torsional intake ducts on the aerodynamic performance of a turbocharger compressor by both 3D numerical simulations and experimental measurements. It was found that at the outlet of the pipes the different inlet ducts can generate different swirl distortions, twin vortices and bulk-like vortices with different rotating directions. Among them, the bulk-like vortices not only affect seriously the pressure distribution in the impeller domain, but also significantly deteriorate the compressor performance, especially at high flow rate region. And the rotating direction of the bulk-like vortices is also closely associated with the efficiency penalty. Besides the efficiency, the transient flow rate through a single impeller channel, or the asymmetric mass flow crossing the whole impeller, can be influenced by two disturbances. One is from the upstream bending-torsional ducts; other one is from the downstream volute.
基金This work is financially supported by the National Science Foundation of China(Nos.11571293,51606040,11501484,11601462)the National Key R&D Program of China(No.2016YFB0600101-4)+1 种基金Hunan Provincial Civil-Military Integration Industrial Development Project”Adaptive Multilevel Solver and Its Application in ICF Numerical Simulation”,Jiangsu Province Science Foundation for Youths(No.BK20160677)Hunan Provincial Innovation Foundation for Postgraduate(No.CX2016B246).
文摘The cold fluid flowing over two hot spheroids placed in a tandem arrangement was numerically studied via a GPU-based immersed boundary-lattice Boltzmann method(IB-LBM)model.The drag coefficient and average Nusselt number of both the two spheroids were obtained with the main influencing factors investigated.To validate the IB-LBM model,several numerical case studies containing one and two spheres were firstly conducted to reach the good agreement with the previously reported data.Then,a number of simulations were further carried out which were designed by changing the particle aspect ratio(1.0≤Ar≤4.0)and inter particle distance(1.5≤ι≤7.0,whereι=L/D,D stands for the volume-equivalent sphere diameter)as well as the Reynolds number(10≤Re≤200).Their influence on the momentum and heat transfer characteristics between the solid and fluid phases was fully discussed.Numerical results show that,for all the considered Reynolds numbers and aspect ratios,the individual and total drag coefficients and average Nusselt number increase with the inter particle distance.The inter particle distance has greater influence on the drag coefficient and average Nusselt number of the trailing particle than the leading one.The drag coefficient and average Nusselt number of the trailing particle are far less than the leading one under the same working conditions.The prediction correlations for the drag coefficient and average Nusselt number of both the two spheroids were established with low deviations.At last,the influence of the relative incidence angles between the two tandem spheroids on the momentum and heat transfer was studied.It is shown that the relative incidence angles play significant roles due to the change of the frontal area of the leading spheroid with these angles.