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Zhu X.Y.,Tongji University | Wu M.L.,Tongji University | Tian C.,Tongji University | Li Y.F.,CSR Qingdao Sifang Locomotive Co.
Applied Mechanics and Materials | Year: 2014

Anti-sliding control of urban rail brake can effectively improve the adhesion utilization rate of the train, shorten braking distance and prevent wheel scratches. This paper takes differential velocity plus slip rate and speed reduction plus its differential as slip criterion, using logic threshold control method to establish Single wheel anti-slip control system. Pneumatic model, mechanical model and control model are built in AMESim and Simulink to implement co-simulation. Simulation results show that the comprehensive model can effectively achieve the anti-slide function. And by taking wheel glide distance as evaluation index, the merits of the two kinds of antiskid criterion are analyzed. The results show that deceleration and deceleration differential criterion as sliding criterion effect is better. © (2014) Trans Tech Publications, Switzerland.

Yao S.-B.,CAS Institute of Mechanics | Sun Z.-X.,CAS Institute of Mechanics | Guo D.-L.,CAS Institute of Mechanics | Chen D.-W.,CAS Institute of Mechanics | And 2 more authors.
Acta Mechanica Sinica/Lixue Xuebao | Year: 2013

Intensive turbulence exists in the wakes of high speed trains, and the aerodynamic performance of the trailing car could deteriorate rapidly due to complicated features of the vortices in the wake zone. As a result, the safety and amenity of high speed trains would face a great challenge. This paper considers mainly the mechanism of vortex formation and evolution in the train flow field. A real CRH2 model is studied, with a leading car, a middle car and a trailing car included. Different running speeds and cross wind conditions are considered, and the approaches of unsteady Reynold-averaged Navier-Stokes (URANS) and detached eddy simulation (DES) are utilized, respectively. Results reveal that DES has better capability of capturing small eddies compared to URANS. However, for large eddies, the effects of two approaches are almost the same. In conditions without cross winds, two large vortex streets stretch from the train nose and interact strongly with each other in the wake zone. With the reinforcement of the ground, a complicated wake vortex system generates and becomes strengthened as the running speed increases. However, the locations of flow separations on the train surface and the separation mechanism keep unchanged. In conditions with cross winds, three large vortices develop along the leeward side of the train, among which the weakest one has no obvious influence on the wake flow while the other two stretch to the tail of the train and combine with the helical vortices in the train wake. Thus, optimization of the aerodynamic performance of the trailing car should be aiming at reducing the intensity of the wake vortex system. © 2013 The Chinese Society of Theoretical and Applied Mechanics; Institute of Mechanics, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.

Yao S.,CSR Qingdao Sifang Locomotive Co. | Guo D.,CAS Institute of Mechanics | Sun Z.,CAS Institute of Mechanics | Yang G.,CAS Institute of Mechanics
Engineering Applications of Computational Fluid Mechanics | Year: 2015

Based on the concepts of niche count and crowding distance, a modified multi-objective particle swarm optimization (MPSO) is introduced. The niche count and crowding distance are used to determine the globally best particle across four test cases using an external file. A comparative analysis was carried out between MPSO and non-dominated sorting multiobjective adaptive genetic algorithms, both real-coded and binary-coded. The results show that MPSO based on the crowding distance is best for getting the Pareto front, especially for problems with high-dimensional and non-continuous Pareto fronts. In order to verify the efficiency of MPSO in solving engineering problems, the optimal design of the aerodynamic nose shape of high-speed trains was undertaken using a modified vehicle modeling function (MVMF) parametric method. Taking the aerodynamic drag of the whole train (Cd) and the aerodynamic lift of the trailer car (Cl) as the optimization goals, the Kriging surrogate model was introduced to reduce the computational time, and the MPSO based on crowding distance was used to find the Pareto front. The optimization results show that MPSO is efficient at getting the Pareto front; compared to the original shape, the Cd and Cl of the optimal shape are reduced by 1.6% and 29.74%, respectively. © 2015 The Author(s). Published by Taylor & Francis.

Shuanbao Y.,CAS Institute of Mechanics | Dilong G.,CAS Institute of Mechanics | Zhenxu S.,CAS Institute of Mechanics | Guowei Y.,CAS Institute of Mechanics | Dawei C.,CSR Qingdao Sifang Locomotive Co.
Computers and Fluids | Year: 2014

The complex wake flow of high speed trains severely influences the running safety and amenity of the trailing car. In this paper, based on the streamlined shape of CRH380A high speed train, taking the aerodynamic lift force of the trailing car and the volume of the streamlined head as the objectives, an efficient multi-objective optimization process based on the response surface has been constructed. The Kriging model has been constructed based on the cross-validation method and genetic algorithm (GA). This approach could decrease the number of training samples and improve the optimization efficiency while without decreasing its generalization. After the Pareto optimal solutions being obtained, four design points are chosen for comparative study with the original shape, and one of these points is chosen for the unsteady aerodynamic study together with the original shape. The results reveal that the variation trends of the lift force and the side force of the trailing car are the same as that of the drag of the whole train. After optimization, the volume of the streamlined head is almost the same as that of the original shape. Compared to the original shape, the lift force of the trailing car decreases by 27.86% of and the drag of the whole train decreases by 3.34% in conditions without crosswind, and the lift force of the trailing car decreases by 5.43%, the side force of the whole train decreases by 72.09% and the drag of the whole train decreases by 2.1% in the crosswind conditions. The optimal train benefits from low fluctuations of lift and side force of the trailing car. Besides, better wake flow could be obtained, and the wake vortices are suppressed, too. Consequently, the running safety and amenity of HST are improved a lot after optimization. © 2014 Elsevier Ltd.

Yao S.,CAS Institute of Mechanics | Guo D.,CAS Institute of Mechanics | Sun Z.,CAS Institute of Mechanics | Yang G.,CAS Institute of Mechanics | Chen D.,CSR Qingdao Sifang Locomotive Co.
Science China Technological Sciences | Year: 2012

As the running speed of high-speed trains increases, aerodynamic drag becomes the key factor which limits the further increase of the running speed and energy consumption. Aerodynamic lift of the trailing car also becomes the key force which affects the amenity and safety of the train. In the present paper, a simplified CRH380A high-speed train with three carriages is chosen as the model in order to optimize aerodynamic drag of the total train and aerodynamic lift of the trailing car. A constrained multi-objective optimization design of the aerodynamic head shape of high-speed trains based on adaptive non-dominated sorting genetic algorithm is also developed combining local function three-dimensional parametric approach and central Latin hypercube sampling method with maximin criteria based on the iterative local search algorithm. The results show that local function parametric approach can be well applied to optimal design of complex three-dimensional aerodynamic shape, and the adaptive non-dominated sorting genetic algorithm can be more accurate and efficient to find the Pareto front. After optimization the aerodynamic drag of the simplified train with three carriages is reduced by 3.2%, and the lift coefficient of the trailing car by 8.24%, the volume of the streamlined head by 2.16%; the aerodynamic drag of the real prototype CRH380A is reduced by 2.26%, lift coefficient of the trailing car by 19.67%. The variation of aerodynamic performance between the simplified train and the true train is mainly concentrated in the deformation region of the nose cone and tail cone. The optimization approach proposed in the present paper is simple yet efficient, and sheds lights on the constrained multi-objective engineering optimization design of aerodynamic shape of high-speed trains. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

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