RESUMO
The transformation of railway infrastructure and traction equipment is an ideal way to realize energy savings of urban rail transit trains. However, upgrading railway infrastructure and traction equipment is a high investment and difficult process. To produce energy-savings in the urban rail transit system without changing the existing infrastructure, we propose an energy-saving optimization method by optimizing the traction curve of the train. Firstly, after analyzing the relationship between the idle distance and running energy-savings, an optimization method of traction energy-savings based on the combination of the inertia motion and energy optimization is established by taking the maximum idle distance as the objective; and the maximum allowable running speed, passenger comfort, train timetable, maximum allowable acceleration and kinematics equation as constraints. Secondly, a solution method based on the combination of the adaptive dynamic multimodal differential evolution algorithm and the Q learning algorithm is applied to solve the optimization model of energy-savings. Finally, numeric experiments are conducted to verify the proposed method. Extensive experiments demonstrate the effectiveness of the proposed method. The results show that the method has significant energy-saving properties, saving energy by about 11.2%.
RESUMO
To explore the wetting behavior of nanofluid under high voltage, a contact angle measurement system under electric field is designed and set up. The effects of mass concentration, the type of nanoparticles and the temperature of dielectric layer are considered. The experimental results manifest that the contact angle reduction rate of SiO2-water nanofluid is gradually increased with the increase of nanofluid concentrations from 0 to 0.05 wt%. While, it is decreased when the concentration is varied from 0.05 to 0.25 wt%. On the other hand, the contact angle reduction rate of Al2O3-water nanofluid is generally greater than SiO2-water nanofluid with the same volume concentration. In addition, the reduction rate of the contact angle of the SiO2-water nanofluid would be gradually increased with the increase of the surface temperature of the dielectric layer. Moreover, the experimental values are greatly deviated from the results calculated by Young-Lippmann equation and its modified form of nanofluid. Hence, the present study proposes a dimensionless surface tension correct factor to obtain the modified equation which is based on the Young-Lippmann equation. The influence of electric charge, electric field force, drag force and Brownian force on nanoparticles under high voltage are considered in the modified equation. The results show that the modified equation can predict the trend of the nanofluid contact angle under higher voltage.
