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Stray current corrosion damage is significant in DC traction power supply system (DTS). Stray current collection system including stray current collection network (SCCN) and stray current drainage device (SCDD) is designed to control the stray current. A comprehensive system integrated calculation model is established to evaluate the stray current. And the iterative power flow algorithm with simplification of DTS is proposed. The stray current distribution is calculated by multi sections rail reflux system model. The model is verified with CDEGS simulation. The influence of stray current collection system on stray current is evaluated. The result shows that the primary stray current is mainly affected by rail to SCCN resistance and the length of the line. The efficiency of collecting stray current of SCCN is mainly affected by the resistance of SCCN and the SCCN to earth resistance. While the use of SCDD deteriorates the efficiency of collecting stray current of SCCN. A site test was carried out in Chengdu Metro Line 1 to evaluate the effect of stray current collection system.

Solar thermal storage system has strict requirements on the problems of hydrated salt phase change materials (PCMs) such as supercooling, phase separation, low thermal conductivity and cyclic stability. In addition, the long-term storage/release heat cycle of PCMs lead to the loss of crystallization water and shorten the service life. Herein, we demonstrate an improved model to predict the thermal conductivity of modified carbon-based matrix form-stable PCMs based on the relationship between porosity (e) and modified expanded graphite (MEG) content. The proposed new model may predict the thermal conductivity of carbon-based matrix composites with relatively high precision. Furthermore, the hydrophilic and hydrophobic groups on the surface of EG sheet have been rearranged via titanate coupling agent, and then MEG is introduced as high thermal conductivity porous matrix. The modified aluminum potassium sulfate dodecahydrate (MAPSD) is used as the PCM. Five different EG contents of MEG/APSD composite PCM samples with the same density have been prepared by the method of “melting blend-solidification and form-stable”. In addition, 80 times storage/release heat experiments are carried out on the samples and the heat transfer process of the three-dimensional (3D) model is numerically simulated. It results show that the weight loss of the composites with MEG samples decreased by only 7.85%. The simulation results suggest that the temperature field and phase change interface vary uniformly. Moreover, the composites samples with MEG has the superior heat transfer performance and much higher heat storage/release rate. With sample density 900 kg/m3 and the MEG content of 20 wt%, the MEG/APSD composites has relatively good thermal performance and high cost performance. Therefore, it can be applied for industrial waste heat energy recovery applications, the solar domestic hot water system and mid-temperature thermal energy storage system.

Conventional maintenance mode for the traction power supply system (TPSS) is to perform scheduled regular maintenance activities for power supply equipment, while such maintenance mode may result in undue maintenance tasks and low efficiency due to different degradation processes of different sorts of equipment. To address this problem, this paper introduces a preventive opportunistic maintenance (POM) method for TPSS based on equipment reliability. Firstly, a POM model is established by considering the equipment reliability degradation process based on Weibull distribution. Then, by considering the total power outage time in the planned operation cycle of TPSS as the optimization objective, the optimal maintenance scheme of TPSS is formulated by iterative method of maintenance strategies. The proposed method is verified by introducing practical maintenance strategies and fault record data of the traction transformer, circuit breaker and disconnector in an actual TPSS of a railway administration. Results show that the presented method can make full use of the existing fault data to develop a POM scheme for TPSS. It can improve maintenance efficiency and reduce power outage time, providing guidance to formulate scientific maintenance strategies for TPSS.

Hydrated salt of aluminium potassium sulfate dodecahydrate (APSD)/expanded graphite (EG) form-stable composite phase change material (PCM) has been prepared. Hydrated salt of aluminium potassium sulfate dodecahydrate used as the PCM was firstly modified by using nucleator and thickener with the aiming at solving the supercooling and phase separation. Sulfurized EG is selected as supporting matrix to overcome leakage and low thermal conductivity of MAPSD. Furthermore, hydrophilic and hydrophobic groups on the surface of the expanded graphite is oriented by carrying out titanate coupling agent, which could restrict the volatilization of crystal water and solve the poor cyclic stability problems of APSD. The thermal performance of modified APSD (MAPSD) and modified EG (MEG)/MAPSD composite PCMs are tested and analyzed by using Differential Scanning Calorimeter (DSC), Hot Disk Thermal Constant Analyzer and a small-scale experimental device. The DSC analysis showed that the melting enthalpy of form-stable composite PCM containing 80 wt% APSD and MAPSD are 473.52 and 641.75 J/g, and their corresponding melting points are 84.39 and 84.34 °C, respectively. The 100 times melt-freeze cyclic tests revealed that the mass of MAPSD decreases by 45.57%. However, the mass of MEG/MAPSD composite PCMs decreases by only 7.91% when the sample density (ρ) of 900 kg/m3 and mass fraction of MEG with 20%, which could still maintain its original shape perfectly without any change. What’s more, the effective thermal conductivity of MEG/MAPSD composite PCM (6.157 W/(m·K)) is about 11 times higher than that of pure APSD (0.55 W/(m·K)) and Agari-Uno model is used to predict the thermal conductivity of composite PCMs with different MEG contents. The average deviation is only 3.91% between experimental and predicted value. All the results indicate that the form-stable MAPSD/MEG composite PCMs can be considered as high-performance latent heat storage materials and the great potential for practical application in solar thermal utilization.

Phase change energy storage technology, which can solve the contradiction between the supply and demand of thermal energy and alleviate the energy crisis, has aroused a lot of interests in recent years. Due to its high energy density, high temperature and strong stability of energy output, phase change material (PCM) has been widely used in thermal energy systems. The aim of this review is to provide an insight into the thermal conduction mechanism of phonons in PCM and the morphology, preparation method as well as thermal conductivity of composite PCMs. Phonon thermal conduction mechanism is suggested to cover three forms: phonon-phonon scattering, phonon-defect scattering and phonon-boundary scattering. Then the microcosmic factors affecting the thermal conductivity of composite PCMs are analyzed. The research progress of adding three-dimensional, two-dimensional, one-dimensional and zero-dimensional structure additives to PCM is reviewed. Besides summarizing the preparation method and microstructure, the thermal conductivity of the composite PCMs are also analyzed from the aspect of phonon thermal conductivity mechanism. Meanwhile, some novel materials, including metal organic frameworks (MOFs), titanium dioxide foam, highly graphitized network carbon, graphene foam and hexagonal boron nitride (HBN) nanoparticles, are proposed for the additives of heat storage materials. Ongoing research and development studies indicate that the challenges of the improving the thermal conductivity of PCM focus on the aspects of clarifying the phonon scattering mechanism in PCM, increasing the number of thermal conductivity chains and broadening the thermal transmission channels. Booming progress illustrates that the exploration of high performance PCM is an extremely valuable and scalable option for storing industrial waste heat and solar energy, especially for constant temperature storage and utilization. To bring the phase change heat storage solution into a broader market, more intensive studies in fields of phonon thermal conductivity mechanism, development of high performance composite PCMs and efficient and compact phase change heat storage system are still required.

Traction transformer is one of the core equipment of traction power supply system, and its safe and stable operation are very important for this electrified railway. In this paper, a comprehensive evaluation method combining variable weight coefficient with Bayesian network is proposed based on the information generated by various states of traction transformer during the operation. Firstly, the support and confidence of each single state quantity and comprehensive state quantity are calculated by association rule algorithm based on the historical statistical data of traction transformer, and the constant weight coefficient values of each state quantity are determined; secondly, the score of comprehensive state quantity is determined by the score values and constant weight coefficient of single state quantity; then, the comprehensive state quantity and operation performance are calculated and analyzed by the method of variable weight coefficient. The overall evaluation score and the comprehensive state quantity score were calculated by variable weight coefficient. Finally, Bayesian network method is used to analyze the relationship between state levels at different times, and the final evaluation results are obtained. In this paper, the state information of traction transformer in a railway substation is used to verify the model. The evaluation method proposed in this paper can accurately evaluate the operation status of traction transformer, so that the on-site operation and maintenance personnel can timely repair and maintain the transformer with abnormal operation, so as to achieve the purpose of saving costs and reducing safety risks.

The Eu-doped TiO2 nanoparticles were successfully prepared by a simple sol-gel method. The properties of the catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS), N2 adsorption-desorption, UV–vis diffuse reflectance and photoluminescence (PL) spectroscopy. The results indicated that Eu-TiO2 catalysts had a high specific surface area, enhanced visible light response and low recombination rate of electron-hole pairs. The photocatalytic performances of Eu-TiO2 catalysts for CO2 reduction were investigated under 9 h irradiation of a 300 W Xe arc lamp. The maximum yields of CH4 and CO over the optimized Eu-TiO2 catalyst were 65.53 μmol/g.cat and 42.91 μmol /g.cat, respectively, which were approximately 13 times and 1 times higher than that of pure TiO2. The enhanced photocatalytic performance could be ascribed to the high-efficiency separation of photo-generated electron-hole pairs.

In recent years, with the rapid development of intelligent driving technology, vision based traffic signal target detection is one of the urgent problems to be solved; especially with the extensive application of deep learning technology, the traffic signal data set is more and more important. Due to the variety of traffic signals, there is no data set that can cover all categories at home and abroad. This paper presents a traffic signal data set based on indoor traffic scene. The currently disclosed data category includes 22 categories, including traffic signs and traffic lights. Simultaneously, this paper also uses a two-stage deep learning method to conduct experiments. In order to facilitate other researchers to conduct further research on the disclosed data set in this paper.

The initial simulation calculation of the ORC power generation system was carried out using the software Aspen Plus, and the simulation data matched with the design conditions were obtained. According to the specific structure of the evaporator and superheater in the ORC power generation system and the characteristics of the software Aspen EDR, a new simulation calculation method is proposed: structural simulation calculation method. The calculation method and the direct simulation calculation method are used to carry out simulation comparison to find out the regularity of the change of waste heat resources, and it is convenient to further analyze and control the ORC power generation system.

The waste heat resource of iron and steel industry was the research object. The economical and technical of direct heating, sensible heat storage and latent heat thermal storage were compared. The result shows that using phase change materials (PCM) as storage materials, energy storage density is higher, cost and exergy loss is lower and the discharge of air pollutants can be reduced, which is compliance with the requirements of conservation and reduction of pollutant emissions and has a broad application prospect.

Molar reaction Gibbs function change, molar reaction enthalpy change, equilibrium constant and the equilibrium partial pressure of SO2 and NO for the reaction of simultaneous removal of SO2 and NO by using NaClO/ammonia solution were calculated based on the principle of chemical thermodynamics. As can be seen from the results, simultaneous removal of SO2 and NO by using NaClO/ ammonia solution is available.