This paper aims to study the electric sliding wear performance of a rigid overhead line/contact strips and to find an optimal overhead line/contact strip pair to minimize the wear…
Abstract
Purpose
This paper aims to study the electric sliding wear performance of a rigid overhead line/contact strips and to find an optimal overhead line/contact strip pair to minimize the wear of the contact strip under direct current (DC) passage.
Design/methodology/approach
The tribological characteristics of an overhead line against four contact strips with DC were experimentally investigated using a block-on-disc tester. The wear and temperature of the contact strips were collected and analysed. The severe wear mechanism of the contact strips was discussed.
Findings
Using Taguchi’s method, DC was found to be the most important factor affecting the wear and temperature of current collectors, the normal force being the second and the sliding velocity the weakest. The abnormal wear of current collectors was attributed to arc ablation and poor thermal stability of collectors. The wear performances of current collectors could be optimized by matching different Cu-impregnated carbon strips with the Cu–Ag wire and the wear of current collectors could be reduced by selecting the appropriate normal force, DC and sliding velocity.
Originality/value
Among all test parameters such as the DC, normal force, sliding speed and collector type, DC was identified as the most important factor affecting the wear and temperature of contact strips for the first time. The arc ablation and thermal stability of collectors were considered to be two main factors affecting the wear of the collectors.
Details
Keywords
Yuhan Li, Qun Luo, Shiyu Zhao, Wenyan Qi, Zhong Huang and Guiming Mei
The purpose of this paper is to study the aerodynamic characteristics and uplift force tendencies of pantographs within the operational height span of 1,600–2,980 mm, aiming to…
Abstract
Purpose
The purpose of this paper is to study the aerodynamic characteristics and uplift force tendencies of pantographs within the operational height span of 1,600–2,980 mm, aiming to offer valuable insights for research concerning the adaptability of pantograph-catenary systems on double-stack high container transportation lines.
Design/methodology/approach
Eight pantograph models were formulated based on lines with the contact wire of 6,680 mm in height. The aerodynamic calculations were carried out using the SST k-ω separated vortex model. A more improved aerodynamic uplift force method was also presented. The change rule of the aerodynamic uplift force under different working heights of the pantograph was analyzed according to the transfer coefficients of the aerodynamic forces and moments.
Findings
The results show that the absolute values of the aerodynamic forces and moments of the upper and lower frame increase with the working height, whereas those of the collector head do not change. The absolute values of the transfer coefficients of the lower frame and link arm were significantly larger than those of the upper frame. Therefore, the absolute value of the aerodynamic uplift force increased and then decreased with the working height. The maximum value occurred at a working height of 2,400 mm.
Originality/value
A new method for calculating the aerodynamic uplift force of pantographs is proposed. The specifical change rule of the aerodynamic uplift force of the pantograph on double-stack high container transportation lines was determined from the perspective of the transfer coefficients of the aerodynamic forces and moments.
Details
Keywords
Xiaohua Yang, Chongli Di, Ying Mei, Yu-Qi Li and Jian-Qiang Li
The purpose of this paper is to reduce the computational burden and improve the precision of the parameter optimization in the convection-diffusion equation, a new algorithm, the…
Abstract
Purpose
The purpose of this paper is to reduce the computational burden and improve the precision of the parameter optimization in the convection-diffusion equation, a new algorithm, the refined gray-encoded evolution algorithm (RGEA), is proposed.
Design/methodology/approach
In the new algorithm, the differential evolution algorithm (DEA) is introduced to refine the solutions and to improve the search efficiency in the evolution process; the rapid cycle operation is also introduced to accelerate the convergence rate. The authors apply this algorithm to parameter optimization in convection-diffusion equations.
Findings
Two cases for parameter optimization in convection-diffusion equations are studied by using the new algorithm. The results indicate that the sum of absolute errors by the RGEA decreases from 74.14 to 99.29 percent and from 99.32 to 99.98 percent, respectively, compared to those by the gray-encoded genetic algorithm (GGA) and the DEA. And the RGEA has a faster convergent speed than does the GGA or DEA.
Research limitations/implications
A more complete convergence analysis of the method is under investigation. The authors will also explore the possibility of adapting the method to identify the initial condition and boundary condition in high-dimension convection-diffusion equations.
Practical implications
This paper will have an important impact on the applications of the parameter optimization in the field of environmental flow analysis.
Social implications
This paper will have an important significance for a sustainable social development.
Originality/value
The authors establish a new RGEA algorithm for parameter optimization in solving convection-diffusion equations. The application results make a valuable contribution to the parameter optimization in the field of environmental flow analysis.