Hardgrove grindability index （HGI） is an important indicator of coal grindability, and is one of the most important parameters to determine the capacity of coal pulverizer in power station. However, HGI is an empiri...Hardgrove grindability index （HGI） is an important indicator of coal grindability, and is one of the most important parameters to determine the capacity of coal pulverizer in power station. However, HGI is an empirical grindability index without linkages to any known physical parameters. To investigate the effect of energy input on the grinding in Hardgrove mill. a T20WN torque meter was installed on the shaft of a modified Hardgrove mill to record the torque driving the mill. Samples from four kinds of coals with HGI ranging from 36 to 72 were prepared according to the procedure of standard HGI test and ground in a modified Hardgrove mill at different revolutions. The relation of sample size reduction degree to specific comminution energy （Ecs） was studied with Shi-Kojovic model, The results show that Shi-Kojovic model predicted well the coal size reduction degree with Ecs in Hardgrove mill. The griadability index given by Shi-Kojovic model has a similar trend with HGI. The relation of sample size reduction degree to Ecs reveals that HGI has a non-linear relationship with effective specific energy in Hardgrove mill, which explains the non-linear relation of HG1 to industrial pulverizer capacity.展开更多
In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the e...In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the experimental results,a power exponent function was used to model the creep degree of these high-performance concretes(HPCs) for structural numerical analysis,and two series parameters of this function for the HPCs were given with the optimum method of evolution program.The experimental data were compared with CEB-FIP 90 and ACI 92 models.Results show that the two code models both overestimate the creep degree of two HPCs,so it is recommended that the power exponent function should be used for the creep analysis of bridge structure.展开更多
This paper proposes an approach to evaluate the performance of robot manipulator from the view of energy analysis. Based on the dynamics analysis of the manipulator, the Energy Distribution Index （EDI） is defined to...This paper proposes an approach to evaluate the performance of robot manipulator from the view of energy analysis. Based on the dynamics analysis of the manipulator, the Energy Distribution Index （EDI） is defined to depict the energy increment contribution of its subsystem to the whole manipulator. EDI is applied to the evaluation of the buffeting capability of the manipulator working under unpredictable and heavy external loads. A series of buffering indices, the Static Buffering Index （SBI）, Kineto-Static Buffering Index （KBI）, Dynamic Buffering Index （DBI）, and Global Buffering Index （GBI） are proposed to evaluate the buffering capability under different conditions. In order to acquire higher calculation accuracy, the general stiffness mapping of manipulators considering the actuator stiffness, inertia of the manipulator, damping, as well as elasticity of linkages is developed. Three different robot manipulators are studied as evaluation cases, in which the buffering structures are mechanism with variable topology, linear springs, and the elasticity of linkages respectively. The case studies show that the indices based on energy analysis have the advantage of coordinate free and are effective for buffering capability evaluation.展开更多
The roughness increase on horizontal axis wind turbine(HAWT) blade surface,especially on the leading edge,can lead to an aerodynamic performance degradation of blade and power output loss of HAWT,so roughness sensitiv...The roughness increase on horizontal axis wind turbine(HAWT) blade surface,especially on the leading edge,can lead to an aerodynamic performance degradation of blade and power output loss of HAWT,so roughness sensitivity is an important factor for the HAWT blade design.However,there is no criterion for evaluating roughness sensitivity of blade currently.In this paper,the performance influences of airfoil aerodynamic parameters were analyzed by the blade element momentum(BEM) method and 1.5 MW wind turbine blade.It showed that airfoil lift coefficient was the key parameter to the power output and axial thrust of HAWT.Moreover,the evaluation indicators of roughness sensitivity for the different spanwise airfoils of the pitch-regulated HAWT blade were proposed.Those respectively were the lift-to-drag ratio and lift coefficient without feedback system,the maximum lift-to-drag ratio and design lift coefficient with feedback system for the airfoils at outboard section of blade,and lift coefficient without feedback,maximum lift coefficient with feedback for the airfoils at other sections under the pitch-fixed and variable-speed operation.It is not necessary to consider the roughness when HWAT can be regulated to the rated power output by the pitch-regulated and invariable-speed operation.展开更多
基金the financial supports provided by the National Key Basic Research and Development Program of China (No. 2012CB214904)the Coal Joint Fund of the National Natural Science Foundation of China and Shenhua Group (No. 51134022)+2 种基金the Creative Scholars Climbing Program of Jiangsu Province Basic Research Program (No. BK2010002)the Funds for Creative Research Groups of China (No. 50921002)the Australia Coal Association Research Program (No. C15079)
文摘Hardgrove grindability index （HGI） is an important indicator of coal grindability, and is one of the most important parameters to determine the capacity of coal pulverizer in power station. However, HGI is an empirical grindability index without linkages to any known physical parameters. To investigate the effect of energy input on the grinding in Hardgrove mill. a T20WN torque meter was installed on the shaft of a modified Hardgrove mill to record the torque driving the mill. Samples from four kinds of coals with HGI ranging from 36 to 72 were prepared according to the procedure of standard HGI test and ground in a modified Hardgrove mill at different revolutions. The relation of sample size reduction degree to specific comminution energy （Ecs） was studied with Shi-Kojovic model, The results show that Shi-Kojovic model predicted well the coal size reduction degree with Ecs in Hardgrove mill. The griadability index given by Shi-Kojovic model has a similar trend with HGI. The relation of sample size reduction degree to Ecs reveals that HGI has a non-linear relationship with effective specific energy in Hardgrove mill, which explains the non-linear relation of HG1 to industrial pulverizer capacity.
文摘In order to investigate the compression creep of two kinds of high-performance concrete mixtures used for prestressed members in a bridge,an experimental test under laboratory conditions was carried out.Based on the experimental results,a power exponent function was used to model the creep degree of these high-performance concretes(HPCs) for structural numerical analysis,and two series parameters of this function for the HPCs were given with the optimum method of evolution program.The experimental data were compared with CEB-FIP 90 and ACI 92 models.Results show that the two code models both overestimate the creep degree of two HPCs,so it is recommended that the power exponent function should be used for the creep analysis of bridge structure.
基金supported by the National Natural Science Foundation of China(Grant No.51075259,50821003)the National Basic Research Program of China("973"Program)(Grant No.2006CB705400)
文摘This paper proposes an approach to evaluate the performance of robot manipulator from the view of energy analysis. Based on the dynamics analysis of the manipulator, the Energy Distribution Index （EDI） is defined to depict the energy increment contribution of its subsystem to the whole manipulator. EDI is applied to the evaluation of the buffeting capability of the manipulator working under unpredictable and heavy external loads. A series of buffering indices, the Static Buffering Index （SBI）, Kineto-Static Buffering Index （KBI）, Dynamic Buffering Index （DBI）, and Global Buffering Index （GBI） are proposed to evaluate the buffering capability under different conditions. In order to acquire higher calculation accuracy, the general stiffness mapping of manipulators considering the actuator stiffness, inertia of the manipulator, damping, as well as elasticity of linkages is developed. Three different robot manipulators are studied as evaluation cases, in which the buffering structures are mechanism with variable topology, linear springs, and the elasticity of linkages respectively. The case studies show that the indices based on energy analysis have the advantage of coordinate free and are effective for buffering capability evaluation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50976117 and 50836006)
文摘The roughness increase on horizontal axis wind turbine(HAWT) blade surface,especially on the leading edge,can lead to an aerodynamic performance degradation of blade and power output loss of HAWT,so roughness sensitivity is an important factor for the HAWT blade design.However,there is no criterion for evaluating roughness sensitivity of blade currently.In this paper,the performance influences of airfoil aerodynamic parameters were analyzed by the blade element momentum(BEM) method and 1.5 MW wind turbine blade.It showed that airfoil lift coefficient was the key parameter to the power output and axial thrust of HAWT.Moreover,the evaluation indicators of roughness sensitivity for the different spanwise airfoils of the pitch-regulated HAWT blade were proposed.Those respectively were the lift-to-drag ratio and lift coefficient without feedback system,the maximum lift-to-drag ratio and design lift coefficient with feedback system for the airfoils at outboard section of blade,and lift coefficient without feedback,maximum lift coefficient with feedback for the airfoils at other sections under the pitch-fixed and variable-speed operation.It is not necessary to consider the roughness when HWAT can be regulated to the rated power output by the pitch-regulated and invariable-speed operation.
