The molecular structure strongly affects the fuel sooting propensity. This study aims to investigate the effects of oxygen-free and oxygen-containing aliphatic and aromatic hydrocarbons on soot ...formation. Experiments were carried out in laminar coflow diffusion flames of a n-heptane and iso-octane mixture doped sequentially with cyclohexane, n-hexane, ethanol, and 2,5-dimethylfuran by 15%. Soot samples were collected for characterization using field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-Ray diffraction (XRD), Raman spectroscopy, and thermal gravimetric analysis. Peculiar structures consisting of ultrafine particles were observed in the deposit collected in all the flames except the one doped with ethanol. According to the surface morphology of soot samples, a model of the peculiar structure of soot deposit was proposed: oxidation free radical attack-deposit and edge defect carbon oxidation model. Based on the results of TEM image, XRD pattern, Raman spectroscopy signal, and thermogravimetric analysis, the reasons for the formation of this peculiar structure were analyzed. The results show that the aged soot particles formed in the flame doped with 15% ethanol (E15) have smaller interlayer spacing, larger polycyclic aromatic hydrocarbon stacking thickness (Lc), smaller grain width (La), smaller crystal stacking layer (N), smaller size, and a higher apparent activation energy. These characteristics were consistent with the fairly flat surface of the E15 soot deposits. Soot produced in other flames, especially doped with cycloalkanes, had a large grain width and crystal stacking layers, a lower apparent activation energy, higher oxidation reactivity, and displayed large gaps on the surface and was easily attacked by oxidizing free radicals. Moreover, the large gaps between the crystal layers of the shell structure of single soot particles, and the existence of edge polycarbonate made the crystal edge easy to be activated to produce defects. These soot had high oxidation activity and were prone to secondary combustion, leading to smaller soot particles and forming the peculiar structure on the deposit surface.
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•Combustion characteristic and thermal transmission in a cylindrical micro combustor are investigated.•Porous media and different wall thickness for combustor are used to enhance the ...heat transfer.•Thermal performance of outer wall and working performance are investigated.•Effects of external thermal environment on the working performance of micro combustor are conducted.
An investigation on non-premixed H2/air combustion in a cylindrical micro combustor has been carried out. The effects of porous media and outer wall thickness on the combustion characteristics, flame location, thermal performance and energy conversion efficiency of the thermo photovoltaic (TPV) system were investigated. For the application of micro TPV system, a high and uniform outer wall temperature distribution is indispensable for the sustaining output, and the high energy efficiency is desirable. The results indicate that the setting of porous media or the increase of outer wall thickness can enhance the heat transfer in micro combustor and affects the flame stability, and the micro combustor with porous media and outer wall thickness b = 0.2 mm obtains the lowest flame location. They are also conducive to the improvement of outer wall temperature and energy efficiency, the outer wall temperature of the micro combustor with a thicker outer wall and porous media is relatively uniform and the energy conversion efficiency of micro TPV system is also improved, the micro combustor with b = 0.6 mm and porous media is more suitable for the application of micro TPV system. Additionally, the external thermal environment also can improve the outer wall temperature profile and the working performance of the micro combustor.
•Research progress of gasoline and its surrogate fuels is summarized systematically.•Mechanism and experiment of gasoline and its surrogate fuels have been reviewed.•Some prospects for mechanism and ...experiment development are put forward.
Improvement of gasoline combustion efficiency and its emission reduction are the hot theses of the gasoline components and its surrogate fuels. In this paper, the mechanism and experiment research progress of gasoline constituents and its surrogate fuels are investigated and summarized systematically. The systematic summary results show that the development of gasoline and its surrogate fuels mechanism mainly include three parts: (1) New skeletal mechanism establishment (including more components); (2) More accurate algorithms for detailed mechanism reduction for reducing the computation time; (3) Mechanism update for gasoline and its surrogate fuels combustion characteristics more accurate (such as velocity, ignition delay time). The experiment measurement includes NOx, CO and HC emissions, soot formation, engine simulation experiments, laminar burning velocity (LBV) measurement, and the ignition delay time measured by shock tube and rapid compression reactor. From the review, studies show that alcohols (including bioethanol) have a positive role in reducing HC and CO emissions from fuel combustion. However, the impacts of alcohols addition on NOx emissions are uncertain, the doping ratio increase of alcohol will cause a non-linear increase or decrease of NOx generation. The low temperature combustion got more and more attention because its high efficiency and low emissions, and the next researches will be not only to improve fuel combustion efficiency, but also to reduce pollutant emissions, and low temperature combustion meets these requirements. Biofuels (such as acetone-butanol-ethanol) blended with gasoline and more components (such as naphthene) added into gasoline surrogate fuels are promising way in the future.
In order to provide an accurate State-Of-Health (SOH) estimation, a novel estimation method is proposed in this paper. In this work, some battery SOH relate features are selected theoretically, ...proved and then re-screened mathematically. These features can reflect the battery degeneration from different aspects. Also, a new training set design idea is proposed for Least Squares Support Vector Machine algorithm, thereby a model that is suitable for lithium-ion Battery SOH estimation under multi-working conditions can be built. Several lithium-ion battery degeneration testing datasets from National Aeronautics and Space Administration Ames Prognostics Center of Excellence are used to validate the proposed method. Results demonstrate both the superiority of the proposed method and its potential applicability as an effective SOH estimation method for embedded Battery Management System.
•A novel estimation method for State-Of-Health estimation is proposed.•Some features related to battery SOH are selected and re-screened mathematically.•A model for lithium-ion Battery SOH estimation under multi-working conditions is built.
•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.
•A backward facing step and unique inlet shape are used in a micro combustors.•The non-premixed hydrogen/air combustors with catalyst segment are compared.•Key parameters affecting the performance of ...a non-premixed hydrogen/air combustors are summarized.
In this work, a type of non-premixed hydrogen/air micro combustor is designed for the application of micro-thermophotovoltaic (MTPV) systems. The micro combustor is presented with a backward-facing step and unique inlet shape to enhance the mixing performance and flame stabilization. The combustion, flow, and heat transfer characteristics of non-premixed hydrogen/air combustion in micro combustors with/without catalyst segment are numerically investigated. The results indicate that the homogeneous reaction is obviously weakened in the catalytic combustor, but a higher and more uniform outer wall temperature is obtained, and the outer wall temperature difference can be decreased by up to 28%. The flow characteristics of gaseous mixture in the catalytic combustor are better than those in the non-catalytic combustor. When the inlet velocity is 10 m/s, the average flow velocity and pressure loss of the catalytic combustor are decreased by up to 5.6% and 250 Pa, respectively. Furthermore, the heat of reaction and total heat flux at the gas–solid interface of the catalytic combustor are obviously higher and lower than those of the non-catalytic combustor, and the outer wall heat loss ratio is increased by up to 0.59% when the inlet velocity is 10 m/s. All in all, it can be concluded that adopting catalytic combustion to the micro combustor is extremely suitable for the application of MTPV systems.
In this paper, the characteristics analysis results of lithium-ion battery show that the essence of the inconsistency of lithium-ion battery is State-Of-Charge (SOC) inconsistency. Therefore, the ...disparity of SOC can be used to describe the battery inconsistency degree and investigate the equalization control strategy of lithium-ion battery. Firstly, Extended Kalman Filter (EKF) algorithm is proposed to estimate the SOC on the basis of the Ampere-Hour integral and open circuit voltage. Then, the Simscape battery model is established to estimate battery parameters, and the HPPC experiment is employed to verify the SOC estimation precision. Moreover, based on the battery SOC inconsistency laws, the battery equalization control strategy is presented. Finally, the experimental bench is set up to validate the effectiveness of the equalization strategies. Simulation results depict that with the active equalization, the dispersion of SOC drops from 9.4% to 0.84% during charging phase, while the dispersion of SOC drops from 7.4% to 4.12% and the dispersion of voltage drops from 8.54% to 0.71% during discharging phase. The experimental results show that the maximum SOC estimation error is about 4%, so this SOC estimation method meets the accuracy requirement; the 6 batteries are fully charged at the same time with charging equalization, the voltage error is within 15 mV and the voltage variance is within 2%; discharging processes of the 6 batteries are over at the same time with discharging equalization, voltage error is below 15 mV and the voltage variance is below 2%. These results indicate that active equalization control in this paper not only can improve cell inconsistency but also can improve the energy utilization of the battery pack in the process of charging and discharging.
•Disparity of State-Of-Charge is used to describe the degree of battery inconsistency.•Equalization control strategy of lithium battery is investigated and proposed.•Extended Kalman Filter algorithm is proposed to estimate the State-Of-Charge.•Simscape battery model is established to estimate battery parameters.
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•A L16(44) orthogonal array is selected to design sixteen models.•Cooling effect of a liquid-cooled battery thermal management model is investigated.•Number of the pipe has obvious ...effect on the average temperature of the cooling plate.•Optimal case by this orthogonal analysis can meet various cooling conditions.
In order to analyze the influence of four parameters on the cooling effect of a liquid-cooled battery thermal management model, a L16(44) orthogonal array is selected to design sixteen models to perform and quantify the parametric to identify the main and secondary factors, then the optimal combination model is found. The results show that the number of the pipe has most obvious effect on the average temperature of the cooling plate in the four parameters, and velocity of coolant flow is second, pipe height has the minimal effect. In terms of temperature uniformity, amount of pipe and velocity of coolant have similar effects which are both main factors, pipe width and pipe height have similar effects which are both secondary factors. The optimal case by this orthogonal analysis can meet various cooling conditions.
Diesel particulate filter (DPF) is one of the most effective devices to solve automobile exhaust emission problem. A DPF model with multilayer porous media (PM) and varied porosity is proposed to ...improve regeneration performance and conversion rate. Effects of PM setting, inlet temperature and flow rate on pressure distribution, thermal performance and conversion rate of the DPF are investigated. The results indicate that the static pressure of DPF with multilayer PMs is increased with the improvement of temperature under the condition of porosity P = 0.4, and the static pressure of the incremental model with multilayer PMs is 22.3 Pa and 42.5 Pa lower than that of the holistic and degressive filter, respectively. The pressure distribution is more uniform and the conversion rate is higher than P = 0.5 and P = 0.6. In addition, the increase of porosity is conductive to the rapid heating and reducing the static pressure. Furthermore, the conversion rate of multilayer (P = 0.3 + 0.4+0.5) is increased by 59.24% within t = 400 s and heat transfer performance is significantly improved when the mass flow rate increases from mf = 10 g/s to mf = 30 g/s. Hence, the incremental PM setting is contribute to the achievement of high conversion rate and better thermal performance, reducing engine emissions.
•A diesel particulate filter with multilayer porous media is proposed for the engine aftertreatment.•Effects of layers setting and porosity on pressure and temperature of filter are compared and analyzed.•Coupling effects of flow rate and PM setting on the thermal and regeneration performance are investigated.
•Hydrocarbon catcher is used for hydrocarbon emission control during cold start.•Grand Canonical Monte Carlo method is used in the adsorption.•Molecular Dynamics is used in the diffusion simulation ...of hydrocarbon molecules.
In this work, adsorption characteristic of the MOR, MFI, and CON zeolites used in hydrocarbon catcher and diffusion properties of hydrocarbon (HC) molecules on them were studied for hydrocarbon emission control during cold start. To find adsorbents with promising adsorption performance for hydrocarbon catcher, the numerical simulation was carried out by using Material studio software with benzene (C6H6) and ethylene (C2H4) as the probes, the Grand Canonical Monte Carlo (MC) method was used in the adsorption simulation, and Molecular Dynamics (MD) method was used to simulate the diffusion of hydrocarbon molecules. The isotherms, adsorption sites, heats of adsorption, and interaction energy distribution of hydrocarbon single-component and multi-component molecules on three different zeolites were studied at various low temperatures and pressures. Based on the simulation results, the most suitable type of molecular sieve was found from the three molecular sieves when the type and quantity of components were different. Results of adsorption simulation show that CON molecular sieve has batter adsorption performance for benzene component. The adsorption amount is 65/unitecell (UC) benzene molecules per cell, which is about twice of MFI molecular sieve. MFI molecular sieve has batter adsorption performance for ethylene component. The adsorption amount is 130/UC ethylene molecules per cell, which is about 2 and 1.5 times of MOR and CON, respectively of MOR molecular sieve. The adsorption simulation results of mixed hydrocarbon components show that the adsorption capacity of each component on the three molecular sieves was ranked as follows: C6H6 > C3H6 > C2H4 > C3H8 > H2O > CH4, collectively. The results of diffusion simulation show that the single component of ethylene molecule has relatively small diffusion coefficient on MFI molecular sieve about 2.2×10−10m/s and good adsorption performance at low temperature, and the largest diffusion coefficient on CON molecular sieve about 3.4×10 −10m/s. The single component of benzene molecules has the smallest diffusion coefficient on the CON molecular sieve 5.9×10−11m/s about and the largest diffusion coefficient on the MOR molecular sieve about 1.76×10−10m/s. In multicomponent diffusion. In multicomponent diffusion. The diffusion degree of each component molecule in the MFI and CON molecular sieve from strong to weak is about: H2O, CH4, C2H4, C3H8, C3H6 and C6H6. The diffusion pattern within the MOR molecular sieve from strong to weak approximately: C3H8, C6H6, C3H6, C2H4, CH4 and H2O. The results show that the high temperature had an obvious effect on the adsorption capacity of zeolite. As temperature rises the molecular diffusion coefficient increases and the molecular motion becomes more intense. After about 500 K, the adsorption capacity is at a very low level.
