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Based on the lumped mass method, a torsional vibration model of the planetary gear system is established considering the nonlinear factors such as friction, time-varying meshing stiffness, backlash, and comprehensive error. The Runge–Kutta numerical method is used to analyze the motion characteristics of the system with various parameters and the influence of tooth friction on the bifurcation and chaos characteristics of the system. The numerical simulation results show that the system has rich bifurcation behavior with the excitation frequency, damping ratio, comprehensive error amplitude, load and backlash, and experiences multiple periodic motion and chaotic motion. Tooth friction makes the bifurcation behavior of the system fuzzy in the high frequency and heavy load areas, makes the chaos of the system restrained in the low-damping ratio and light load areas, advances the bifurcation point of the system in the small comprehensive error amplitude area, and makes the period window of the chaos area larger in the large-backlash area, which makes the bifurcation behavior of the system more complex. [ABSTRACT FROM AUTHOR]

In this work, a composite cooling system including composite phase change material(CPCM) and liquid cooling is designed for battery pack, and the effects of coolant flow rate, battery spacing, thermal conductivity of CPCM, channel number of cooling plate on the safety performance of battery pack under thermal runaway propagation are studied. The results reveal that: (1)Coolant flow rate increase mainly delays the thermal runaway propagation on both sides of cooling plate. When the coolant flow rate is 0.029 m/s, the thermal runaway propagation time through the cooling plate is 32.9s, which is extended by 1.84 times than that at 0.009 m/s (2)Battery spacing increase delays thermal runaway propagation and changes the propagation path. (3)Thermal conductivity reduction of CPCM can significantly delay thermal runaway propagation, because the heat is concentrated in the periphery of the battery and is hard to transfer though CPCM and cooling plate. (4)Compared with other influence factors, channel number of cooling plate has less influence on the overall thermal runaway propagation time. When the channel number is between 5 and 1, the total thermal runaway time changes within 25.5s–27s. The conclusions in this work are helpful to design a safer thermal management system for lithium-ion battery packs. • A novel composite cooling strategy is designed for cylindrical battery pack. • Effects of different factors on the thermal safety of the battery pack are studied. • Thermal runaway propagation path and time of the battery pack are analyzed and obtained. [ABSTRACT FROM AUTHOR]

• Cold starting process of diesel engine at low temperature is analyzed in detail. • An improved thermodynamic model of diesel engine is developed. • Cold starting performance of diesel engine is validated by the experimental results. • Suggestions for cold starting performance enhancement of the diesel engine are proposed. It is very important for the diesel engine to achieve a cold startup at low environmental temperature especially in the region with the temperature in the range of −40 °C to 0 °C. Thus, the specific cold start characteristics, such as gas leakage, heat loss and clearance volume, should be investigated in detail. In order to investigate the cold start ability, an improved thermodynamic model for thermodynamic parameters is developed. The prediction of ignition temperature is the closest to the experimental values when the adiabatic index is equal to 1.34 for the compressed gas. The thermodynamic results show that the compression pressure is the most sensitive to the gas leakage rate , followed by the heat transfer loss rate and reference clearance volume. The gas leakage, heat loss and clearance volume are employed to investigate the cold start ability for the diesel engine, which provide a better reference for strengthening the cold start capacity research. The small clearance volume and big initial intake air temperature can improve the exergy of diesel engine. In addition, the entropy production increases with the increase of clearance volume. Similarly, the exergy of system will reduce with the increase of entropy production. Finally, the improvement suggestions for cold starting performance enhancement of the diesel engine are proposed. [ABSTRACT FROM AUTHOR]

Highlights • Graphene used in energy conversion and heat transfer are classified and compared. • Performances of energy equipment made of graphene products are investigated. • Further application of graphene products in the field of energy is summarized. • Heat transfer applications of nano-graphene and graphene coatings are discussed. Abstract Along with the chic fad energy industry field, the graphene application in energy conversion and management does bring about some benefits in terms of the energy transfer and storage development, the achievement it exerts on the multifaceted innovate approaches. Both current and previous studies on energy conversion, energy storage and energy transfer development, many research results are sufficient to show that all graphene products including graphene paper, film, foam and fiber have a significant role in improving performance. In the energy conversion research on the graphene paper, it has been recently demonstrated that putting the graphene into triboelectric nanogenerators practice possesses higher output performance than traditional generator, which has a maximum strain as large as 200% without evident degradation of the electrical properties. In terms of energy transfer, the graphene fiber application on the battery can significantly increase the charge and discharge rates with enhanced storage capacity of 763 F g−1. On the energy storage research, the graphene foam can enhance a high density of solar thermal storage up to 269.8 kJ kg−1 for long-term. Nano-graphene and graphene coating provide feasibility for the miniaturization of energy storage equipment which inspired the possibility for portable and foldable devices. The work done in this paper can effectively help promote the application of graphene in energy field. Based on our work, the researchers can choose graphene products (graphene paper, graphene film, graphene foam or graphene fiber) efficiently according to the research object in the future. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A dish concentrator model is developed by two coupling software. • Finite element model is used to predict the amplitude and frequency of the vibration. • Fluid-structure coupling model is used to analyze harmonic response. • The maximum deformation of reflector is analyzed. • The modal analysis is performed by the fluid-structure coupling model. Abstract The dish solar thermal power generation system is widely used due to the high efficiency. The mechanism of the whole system must meet stringent structural deformation requirements. In this work, the dish concentrator model is developed by the CFD software STAR-CCM+ and the finite element software of ABAQUS, respectively. The pressure fields obtained in the STAR-CCM+ environment are mapped to the ABAQUS model. The validated finite element (FE) model is employed to predict the amplitude and frequency of the vibration. The effects of different pitch angle, azimuth angle and wind velocity on the amplitude and frequency of the vibration are also considered in the process of calculation. The simulated calculation of fluid-structure coupling model is used for the analysis of harmonic response of four hinge nodes vibration. The vibration period of sinusoidal wind excited is 2 s. The results show that the vibration of the dish concentrator will occur with the sinusoidal wind load and reaches the maximum in a short time, then gradually becomes flatter. Moreover, the change of the height angle has a little influence on the modal frequencies of the system and the modal natural frequency is only changed a little when the wind load increases. Thus, the information obtained from the FE model can serve as a reference for subsequent analyses mechanism design such as wind-induced response dynamics analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Different low-level of water-biodiesel emulsion fuels are employed in this work. • Effects of water additive rate on spray, combustion and emission characteristics are investigated. • A computational modeling is developed by the chemical kinetics mechanism. • Water additive and the kinetic viscosity of biodiesel fuel play very important roles. Abstract In this work, the low water-level water-biodiesel emulsion (WBE) fuels (2, 4 and 6 wt%) and pure biodiesel fuel were used to investigate the effects of water addition on spray, combustion and emission characteristics of a medium speed diesel engine in terms of cylinder pressure, cylinder temperature, heat release rate, brake power, brake thermal efficiency, brake specific fuel consumption, NO x , soot, CO and CO 2 emissions. The corresponding three-dimensional CFD model was performed by AVL-Fire coupled CHEMKIN II code, and an improved chemical kinetics mechanism containing 475 reactions and 134 species was developed to simulate the fuel spray process and combustion process since it contained methyl linolenate, methyl linoleate, methyl oleate, methyl stearate, methyl palmitate, a majority component in most biodiesel, thus improved the accuracy of simulation. The result obtained showed that the water addition in fuel played an important role in fuel spray process and fuel combustion process. The fuel-air mixing was improved due to the micro-explosion. More specifically, the findings revealed that low-level water addition in biodiesel fuel could reduce NO x , CO and CO 2 emissions. The optimal water addition level in terms of diesel engine emission and performance parameters was found at 4 wt% among WBE fuels. In particular, the NO x , CO and CO 2 emissions were reduced respectively, at maximum speed of 1000 rpm. Thus, the relationship between water addition rate and combustion and emission characteristics is not straightforward, the balance between water addition and fuel is very important. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study the equipment parameters of expressway convective wind energy collection devices and determine the optimal structural parameters by numerical methods. Firstly, the characteristics of convection wind energy and flow field on the expressway are analyzed and the principle of wind energy utilization is determined. Based on traditional resistance wind turbines, two different blades of the device are designed and developed. Some structural parameters (such as blade height and the number of blades) of the device are discussed based on the flow field characteristics. Secondly, the device is numerically simulated using Star CCM+ software, and the optimal structural parameters are determined based on the power coefficient. Thirdly, the proposed numerical analysis method is verified and indirect verification is used to determine the most suitable turbulence model and grid independence based on the similarity principle. Based on the above research results, the experimental verification is used to determine the high reliability of the simulation model. Finally, the simulation results between the Rectangular turbine and the Savonius turbine are compared and obtained. The results show that the device is useful for the wind energy usage, wind energy conversion and the wind resistance reduction of the opposite vehicle. At the same time, when the inlet wind speed is 15 m/s, the tip speed ratio (TSR) is 1.4, the device is rectangular turbine (RT), the height of blade is 1.55 m, the number of blades is 4, and the maximum power coefficient C p is 0.363. [ABSTRACT FROM AUTHOR]

In this work, a preheating management system for large-capacity ternary lithium battery is designed, where a novel coupling preheating method of heating film and phase change material (PCM) is employed to preheat. In order to make the preheating system meet the preheating requirements of the battery pack, effects of four influencing factors (heating film power, heating film power difference, cell spacing and PCM thickness) on preheating of the battery pack are studied numerically. Then, the relationship between four factors and preheating time and temperature difference is found, and the optimum parameters in the coupled preheating management system are obtained based on simulation. Finally, the preheating schemes of conventional preheating and rapid preheating under low ambient temperature are determined and investigated. The results show that rapid preheating takes much less preheating time than conventional preheating, where the temperature difference is about 1.48 K and the time consumption is 602 s, 518 s and 394 s under the low temperatures of 253.15 K, 263.15 K and 273.15 K, respectively. In addition, this preheating scheme also prove the feasibility of the designed battery pack thermal management system, which can meet the actual use of electric vehicles. • A novel coupling preheating method combining heating film and phase change material is proposed. • Effects of different influencing factors on preheating of the battery pack are studied. • The optimum thermal management scheme and parameters are determined based on simulation. • The preheating schemes of conventional preheating and rapid preheating are analyzed and compared. [ABSTRACT FROM AUTHOR]

Abstract: Surfaces of plants and animals are evolved to optimal states to accommodate environments better after billions of years of natural selection. As the development of further study on bionics, surfaces with special wetting properties in nature are discovered, extremely related to the micro‐/nanostructures on surface. The wetting models and wetting mechanism of several surfaces in nature are investigated, followed by lifting the veil of superhydrophobic field. Various facile, effective, and convenient methods for fabricating superhydrophobic surfaces are obtained and optimized in scientific research and practice. The possibility of wide application for superhydrophobic surface on production and life is improved via the promotion in fabrication ability. This paper is ranged from four main parts, including wetting models, wetting mechanism on various typical surfaces in nature, frequently used fabricating methods for superhydrophobic surfaces in recent years, and application of superhydrophobic material surfaces in three main aspects. It is really hoped that this review article can provide a useful guide for development of superhydrophobic surface in further study. [ABSTRACT FROM AUTHOR]

In this work, a micro elliptical tube combustor is developed and compared with the regular micro circular tube combustor. The objective of this work is to understand the combustion characteristics (pressure loss, wall temperature, emitter efficiency, heat loss efficiency and combustion efficiency) of H 2 /air premixed combustion in micro elliptical tube combustors under various H 2 mass flow rates, H 2 /air equivalence ratios and major/minor axis length ratios. Results show that the micro elliptical tube combustor owns higher emitter efficiency and combustion efficiency, while the micro elliptical tube combustor is faced with the challenge of the increase of the pressure loss and heat loss efficiency, compared with the micro circular tube combustor. Moreover, it is found that when the major/minor axis length ratio a / b and the H 2 mass flow rate is increased to 1.9/1.18 and 7 × 10 −7 kg/s, respectively, the emitter power and emitter efficiency of the micro elliptical tube combustor is increased by 0.68 W and 2.17%, respectively, compared with that of the micro circular tube combustor. This design extends the geometrical structure of micro tube combustors for applications in the MTPV system, providing us another way to develop micro combustors. [ABSTRACT FROM AUTHOR]

• The porous medium micro-combustor and thermoelectric system is developed. • Effects of the heat exchange and Seebeck converse effect on temperature field are analyzed. • Thermoelectric conversion performance of the micro thermoelectric system is analyzed. • Optimization directions of micro-thermoelectric system are proposed. The energy conversion of micro combustion system has become the main research direction at present. However, due to the small size of micro-combustors, they face challenges such as unstable combustion and difficulty in effectively converting generated thermal energy into usable energy. This work mainly studies the thermoelectric conversion system based on porous medium micro-combustor, which mainly uses the high energy density of micro-combustor to replace the traditional battery energy and improve the working time of small equipment. And this work also establishes the coupling model of porous medium micro combustor and thermoelectric module. By analyzing the performance parameters of the micro thermoelectric system in different flow rate, the results show that at low flow rates, semiconductor materials with better thermoelectric performance, such as Bi 2 Te 3 , can be used to improve the energy conversion efficiency of the system. However, the low heat release from combustion leads to lower maximum output power. At high flow rates, there is a significant improvement in the thermoelectric conversion performance of the system, but it is limited by the temperature of the thermoelectric materials. To optimize the impact of these factors on micro-thermoelectric systems, the optimization methods were analyzed as: (1) The temperature uniformity of micro-combustor wall can be improved by using mixture with low equivalence ratio and high flow rate; (2) enhancing the thermal conductivity of the micro-combustor and porous medium to improve the thermal conductivity of micro thermoelectric system; (3) Using CH 4 -H 2 mixed combustion to reduce combustion temperature and ensure that thermoelectric materials work within the normal temperature range; (4) The segmented thermocouple is used to improve the thermoelectric performance of thermoelectric module. The results show that using a mixture with low equivalence ratio and high flow rate can achieve a maximum conversion efficiency of 5.51%. Using mixed combustion to reduce combustion temperature can increase the maximum output power of the system to 57.8 W. [ABSTRACT FROM AUTHOR]

In order to effectively improve the composite regeneration performance of the diesel particulate filter in vehicle, a fuzzy gray correlation analysis model based on the composite regeneration influencing factors of diesel particulate filter was established using the cosine value of fuzzy membership and Euclidean distance formula. And, on the basis of experimental data from three-dimensional computational fluid dynamics simulation, the fuzzy gray correlation analysis on important degree of characteristic indexes, which has influence on the composite regeneration performance of diesel particulate filter, was conducted. Moreover, the method of Lagrange function was used to solve the fuzzy gray affiliate degree based on the results of this fuzzy gray correlation analysis. The effectiveness indexes of overall performance of the diesel particulate filter composite regeneration time, regeneration peak temperature and regeneration efficiency were also obtained. The results showed that the amount of ceria-based additive had the greatest influence on the regeneration time among all the characteristic performance indexes of diesel particulate filter composite regeneration. Similarly, it could be concluded that the exhaust oxygen concentration and exhaust temperature respectively had the greatest influence on the regeneration peak temperature and regeneration efficiency. In addition, the regeneration time had the greatest influence on the overall performance of diesel particulate filter composite regeneration while the regeneration efficiency took the second place and the influence of the regeneration peak temperature was the minimum. The results of this article showed theoretical significance and reference value for optimization analysis and control of diesel particulate filter composite regeneration process. [ABSTRACT FROM AUTHOR]

• Combustion stabilization technologies for micro/meso-scale combustors are reviewed. • Flammable range is expanded by applying combustion stabilization technology. • Combustion stabilization technology improves outer wall temperature distribution. • Combustion stabilization technology effectively reduces pollutant emissions. • Combustion stabilization technology improves energy conversion efficiency. Owing to its high energy density, the combustion-based micro thermophotovoltaic system has promising prospects and becomes the most potential substitute for conventional power generation systems. As one of the most critical components in micro thermophotovoltaic systems, however, micro/meso-scale combustors are still confronted with many challenges due to the scale effect. Therefore, it is of great significance to develop combustion stabilization technologies for micro/meso-scale combustors. During the past two decades, many researchers have proposed various combustion stabilization technologies, which have been reviewed in this work. According to the working principle, different micro/meso-scale combustion stabilization technologies can be classified into three categories: heat recirculation, flow recirculation, and combustion optimization. The results indicate that these technologies can effectively expand the flammable range and have a positive effect on the stable combustion in micro/meso-scale combustors. Furthermore, the working performance of micro/meso-scale combustors, including thermal performance, emission performance, and energy conversion performance, has been evaluated. The results demonstrate that the application of different combustion stabilization technologies to micro/meso-scale combustors effectively increases the outer wall temperature distribution, reduces CO/NO X emissions, and improves the combustion/radiation efficiency. Finally, the challenges and prospects of future work are outlined. This work expounds on the research progress of micro/meso-scale combustors for micro thermophotovoltaic systems, which provides references for subsequent research and applications. [ABSTRACT FROM AUTHOR]

Based on models A, B, and C of three kinds of diesel particulate filter (DPF) with microwave regeneration, a DPF microwave regeneration model is established according to the laws of conservation of mass, momentum, and energy. The trends of internal temperature under different velocities of exhaust gas in channels are simulated and analyzed. The results show that: (1) Regeneration temperature in the process of microwave regeneration will begin to increase from the front to the rear end of along the axial direction, and the maximum temperature value will appear in the rear end of the monolith. (2) The internal flow velocity in the DPF of model C is the most uniform and the temperature gradient is the smallest among the three models. Therefore, it is the most useful for DPF regeneration. (3) The minimal thermal stress is exerted on the DPF of model C. Therefore, this model is most useful for prolonging the service life of a DPF. [ABSTRACT FROM AUTHOR]

In order to solve the nonlinear mechanism in the process of actual control application of six-degree-of-freedom parallel Stewart platform, the chaos theory was applied in the paper to analyze the acceleration control signal. The research included correlation dimension calculation by use of the G-P method, the maximum Lyapunov coefficient of the acceleration control signal, and Kolmogorov entropies of the acceleration control signal. The results show that the acceleration signals are of chaos characteristics, and there are lots of influencing factors to the acceleration variables. [ABSTRACT FROM AUTHOR]

• Influencing parameters of the flame optimization schemes are summarized. • Influence parameters of the micro-thermal photoelectric system are analyzed. • Influence parameters of the thermoelectric conversion efficiency are investigated. • Technical limitations and development of the micro power equipment are summarized. Hydrocarbon fuel and hydrogen are used as fuels for micro power equipment to replace traditional batteries and provide energy for micro-electromechanical systems, which has become a hot research direction. However, due to the reduction in the size of micro power equipment, not only the flame in the micro combustor is affected, but the overall energy conversion efficiency of micro power equipment is also affected by the size effect. Therefore, it is significance to analyze the energy loss and design optimization methods pertinently from the point of energy conversion. In the past ten years, many researchers have done research about the direction, which has been reviewed in this article. For the flame optimization, the influencing parameters of optimization methods such as exhaust gas recirculation, cavity combustor, bluff body combustor, porous media combustion, and hydrocarbon fuels mixed with hydrogen are summarized. For the micro-thermal photoelectric system, the influence parameters of combustion efficiency, radiant efficiency, spectral efficiency, view factor efficiency and photovoltaic cell efficiency are analyzed. In the micro-thermoelectric system, the influence parameters of combustion efficiency, heat conduction efficiency and thermoelectric conversion efficiency are analyzed. For the micro internal combustion engine, the influencing parameters of combustion efficiency and conversion efficiency are analyzed. Finally, the technical limitations and development of each micro power equipment are summarized in this article. [ABSTRACT FROM AUTHOR]