The input-output ratio and comprehensive energy consumption of low concentration coalbed methane cryogenic liquefaction devices are determined by the process parameters in control of the distillation column. In order to accurately control the actual operation process of the distillation column, the effect of the operating temperature of the distillation column on the liquefaction performance of a cold box was studied experimentally, and the optimal control parameters of the distillation column were obtained. The results show that the recovery rate of methane decreases with the increase in temperature at the top of the distillation column, and when this temperature is higher than −178 °C, the methane recovery rate drops sharply to below 90%. When the temperature at the bottom of the distillation column rises from −154 °C to −142.7 °C, the purity of LNG products is improved, and when this temperature is increased to −143.5 °C, the purity of products at the bottom of the distillation colu... [more]

The stable working window of a dual-fuel engine is narrow, and it is prone to knock during operation. The occurrence of knock limits the load and torque output of a dual-fuel engine, and even causes engine damage in severe cases. The existing volumetric model of marine dual-fuel engine has little research on the related problems of knock simulation. In order to analyze the causes of knock phenomenon and the influence of operating parameter changes on knock, under the Matlab/Simulink simulation environment, a quasi-dimensional model was established with MAN 8L51/60DF dual-fuel engine as the prototype, and the model was calibrated using the bench data. The knock intensity index coefficient (KI) was used as the evaluation index of knock intensity. Three parameters, the intake air temperature, compression ratio, and natural gas intake, were selected as variables to simulate the engine. According to the analysis of the simulation results, the influence of the parameter changes on the occurr... [more]

This paper presents two novel automated optimization approaches. The first one proposes a framework to optimize wind turbine blades by integrating multidisciplinary 3D parametric modeling, a physics-based optimization scheme, the Inverse Blade Element Momentum (IBEM) method, and 3D Reynolds-averaged Navier−Stokes (RANS) simulation; the second method introduces a framework combining 3D parametric modeling and an integrated goal-driven optimization together with a 4D Unsteady Reynolds-averaged Navier−Stokes (URANS) solver. In the first approach, the optimization toolbox operates concurrently with the other software packages through scripts. The automated optimization process modifies the parametric model of the blade by decreasing the twist angle and increasing the local angle of attack (AoA) across the blade at locations with lower than maximum 3D lift/drag ratio until a maximum mean lift/drag ratio for the whole blade is found. This process exploits the 3D stall delay, which is often i... [more]

Carbon capture and storage has gained increased attention during the last decade, and several full-scale projects are currently being planned. From economic and public acceptance point of view it is important to ensure that the transportation system is operated in a safe manner, avoiding threats such as corrosion or formation of solid matters. Thus, routine chemical analyses are required to ensure that the CO2 stream complies with the required specifications. The CO2 will usually be transported in the liquid or supercritical state (high pressure), which makes the practicalities around chemical analyses difficult. Phase transition from liquid or supercritical state to gaseous state may also introduce several physiochemical effects that may affect the analyses. This paper discusses technical and practical challenges with CO2 stream analyses experienced in a joint industry project that studied corrosion and chemical reactions in a simulated CO2 transport system.

The International Panel on Climate Change and the 2015 Climate Summit in Paris have recommended that efforts to reduce carbon emissions be coupled with carbon removal from the atmosphere. Carbon negative energy combines net carbon removal with the production of energy products or other revenue-generating products beyond sequestered carbon. Even though both biochemical and thermochemical approaches to carbon negative energy can be envisioned, this paper considers the prospects for the latter including pyrolysis and gasification. The fundamentals of these two processes are described to better understand how they would be integrated with carbon removal. Characteristics of pyrolysis and gasification are related to the kinds of sequestration agents they would produce, the scale of their deployment, the fraction of biomass carbon that could ultimately sequestered, the challenges of effectively sequestering these different forms of carbon and the economics of thermochemical carbon negative en... [more]

The traditional dry-type mine transformer has some disadvantages, such as incomplete fire prevention, large volume, high loss and not enough environmental protection. Based on evaporative cooling technology, this paper proposes a scheme of mine transformer using fluorocarbon as coolant which can truly realize the incombustible transformer scheme and meet the strict environmental requirements. The transformer adopts three-dimensional wound core structure to reduce the loss and improve the anti-short-circuit ability. The volume of transformer is greatly reduced due to the efficient heat dissipation ability of evaporative cooling technology. The scheme of plate fin heat exchanger is more suitable for the ventilation condition of the mine. The filling technology is used to reduce the amount of expensive coolant. Through the life cycle cost analysis, evaporative cooling transformer has better economic benefits than traditional mine transformer, but also has better safety benefits. A prototy... [more]

Biomass pellet fuel is one of the development directions of renewable energy. The purpose of the article is to study the combustion characteristics of five kinds of biomass pellet fuel that can be used as biomass fuel and analyze their combustion kinetics. The thermogravimetric method (TG method) was used to analyze the combustion characteristics of five kinds of biomass pellet fuel and to calculate the index S of comprehensive combustion characteristic. The Arrhenius equation and the Coats−Redfern method were used to analyze the combustion kinetics of five kinds of biomass pellet fuel. The activation energy and pre-exponential factor were obtained according to different temperature ranges. Conclusions are as follows: The pyrolysis of five kinds of biomass pellet fuel mainly includes three stages: (1) water evaporation stage, (2) volatile component combustion stage, (3) fixed carbon oxidation stage. The TG curves of five kinds of biomass pellet fuel are roughly the same at the same hea... [more]

The printed circuit heat exchanger (PCHE) with discontinuous fins is a novel type of compact and highly efficient plate heat exchanger, which has superior thermal hydraulic performance. The morphology and characteristics of the flow channel greatly affect the performance of the PCHE. The discontinuous airfoil fins are used in PCHE channel design because they can affect the flow and heat transfer by increasing the heat transfer area and the disturbance in the channel. In this paper, the effects of different staggered distance (Ls) and transverse distance (Lv) of airfoil fin arrangements on the heat transfer and flow of supercritical nitrogen in the PCHE are numerically simulated using ANSYS Fluent. Simulation results and subsequent analysis show that the appropriate decrease in Ls and reduction in Lv between the two rows of fins can improve the convective heat transfer of the PCHE. A fully staggered arrangement of fins (Ls = 1.2) and an appropriate increase in the Lv can mitigate pressu... [more]

In recent years, solar thermal energy (STE) has attracted energy researchers because of its higher efficacy compared to the photovoltaic solar cell. STE is one of the forms of solar energy whereby heat is transferred via a secondary medium called heat transfer fluids (HTFs). Therefore, the overall performance of STE depends on the thermophysical properties and thermal performance of the HTFs. Traditional HTFs suffer from low decomposition temperature, high melting point, and higher vapor pressure. To overcome these limitations, researchers have recently begun working on new HTFs for STE. Ionic liquids (ILs) are considered as a potential candidate for the next generation of HTFs because of their enhanced thermophysical properties, such as thermal stability at high temperature, insignificant vapor pressure, and high ionic conductivity. In addition, thermophysical properties and thermal performance of ILs can be further enhanced by dispersing nanoparticles, which is one of the emerging re... [more]

Solid oxide cells represent one of the most efficient and promising electrochemical technologies for hydrogen energy conversion. Understanding and monitoring degradation is essential for their full development and wide diffusion. Techniques based on electrochemical impedance spectroscopy and distribution of relaxation times of physicochemical processes occurring in solid oxide cells have attracted interest for the operando diagnosis of degradation. This research paper aims to validate the methodology developed by the authors in a previous paper, showing how such a diagnostic tool may be practically implemented. The validation methodology is based on applying an a priori known stress agent to a solid oxide cell operated in laboratory conditions and on the discrete measurement and deconvolution of electrochemical impedance spectra. Finally, experimental evidence obtained from a fully operando approach was counterchecked through ex-post material characterization.

Waste heat recovery from flue gas based on water vapor condensation is an important issue as the waste heat recovery significantly increases the efficiency of the thermal power units. General principles for designing of this type of heat exchangers are known rather well; however, investigations of the local characteristics necessary for the optimization of those heat exchangers are very limited. Investigations of water vapor condensation from biofuel flue gas in the model of a vertical condensing heat exchanger were performed without and with water injection into a calorimetric tube. During the base-case investigations, no water was injected into the calorimetric tube. The results showed that the humidity and the temperature of inlet flue gas have a significant effect on the local and average heat transfer. For some regimes, the initial part of the condensing heat exchanger was not effective in terms of heat transfer because there the flue gas was cooled by convection until its tempera... [more]

Intricate fluid flow and transport phenomena in porous media are ubiquitous in natural processes and engineering systems [...]

Biodiesel produced from non-edible plant sources is cost-effective, biodegradable, environment friendly, and compatible with petro-diesel, but new sources and extraction processes still need to be discovered. Here, we explored the fuel properties of seeds from six non-edible plant sources, including Sapindus mukorossi (Soapnut, SP), Vernicia fordii (Tung, TO), Ricinus communis (Castor, CA), Toona sinensis (Juss. TS), Ailanthus altissima (Heaven tree, AA), and Linum usitatissimum L. (Lin seed, LS) from China. The optimum extraction conditions were obtained by optimizing the most important variables (reaction temperature, ratio of alcohol to vegetable oil, catalyst, mixing intensity, and purity of reactants) that influence the transesterification reaction of the biodiesel. All six plants contained high seed oil content (SOC; % w/v) with the highest in the TO-54.4% followed by SP-51%, CA-48%, LS-45%, AA-38%, and TS-35%, respectively, and all expressed satisfactory physico-chemical propert... [more]

Spent coffee grounds contain lipids (fatty acids) in addition to cellulose, hemicellulose, and lignin. The reaction process for upgrading biocrude oil produced from spent coffee grounds is different from that followed for upgrading biomass pyrolysis oil, such as processes that utilize sawdust. The feasibility of upgrading coffee biocrude oil through a supercritical ethanol reaction with plastic pyrolysis oil and through catalytic cracking for the improvement of the undesirable properties of biocrude oil, caused by the presence of oxygenated compounds, was evaluated. The initial oxygen content of the coffee biocrude oil was 16.9 wt%. The oil comprised a total content of 40.9% fatty acids, as found by analyzing the GC-MS peak area. After the supercritical ethanol reaction at 340 ∘C, the oxygen content was decreased to 9.9 wt%. When the MgNiMo/AC catalyst was applied to the supercritical reaction, the oxygen content was further decreased to 8.5 wt%. The esterification of the fatty acids i... [more]

Heat transfer coefficients were investigated for saturated nucleate pool boiling of binary mixtures of water and glycerin at atmospheric pressure in a wide range of concentrations and heat fluxes. Mixtures with water mass fractions from 100% to 40% were boiled on a horizontal flat copper surface at heat fluxes from about 25 up to 270kWm−2. Experiments were carried out by static and dynamic method of measurement. Results of the static method show that the impact of mixture effects on heat transfer coefficient cannot be neglected and ideal heat transfer coefficient has to be corrected for all investigated concentrations and heat fluxes. Experimental data are correlated with the empirical correlation α=0.59q0.714+0.130ωw with mean relative error of 6%. Taking mixture effects into account, data are also successfully correlated with the combination of Stephan and Abdelsalam (1980) and Schlünder (1982) correlations with mean relative error of about 15%. Recommended coefficients of Schlünder... [more]

Biofuels have recently attracted a lot of attention, mainly as alternative fuels for applications in energy generation and transportation [...]

Despite the increasing contribution of the automotive industry to China’s national economy, CO2 emissions have become a challenge. However, the research about its energy consumption and carbon emissions is lacking. The significance of this study is to fill the research gap and provide suggestions for China’s automotive industry to reduce its carbon emissions. In this paper, the extended logarithmic Division index (LMDI) method is adopted to decompose the factors affecting carbon emissions and determine the key driving forces. According to provincial statistical data in China in 2017, the annual emissions of six provinces exceeded five million tons, accounting for 55.44% of the total emissions in China. The largest source of emissions in China is in Jilin Province, followed by Jiangsu, Shandong, Shanghai, Hubei and Henan. The decomposition results show that investment intensity effect is the greatest factor for CO2 emissions, while R&D intensity and energy intensity are the two principa... [more]

The accurate estimation and prediction of lithium-ion battery state of health are one of the important core technologies of the battery management system, and are also the key to extending battery life. However, it is difficult to track state of health in real-time to predict and improve accuracy. This article selects the ternary lithium-ion battery as the research object. Based on the cycle method and data-driven idea, the improved rain flow counting algorithm is combined with the autoregressive integrated moving average model prediction model to propose a new prediction for the battery state of health method. Experiments are carried out with dynamic stress test and cycle conditions, and a confidence interval method is proposed to fit the error range. Compared with the actual value, the method proposed in this paper has a maximum error of 5.3160% under dynamic stress test conditions, a maximum error of 5.4517% when the state of charge of the cyclic conditions is used as a sample, and... [more]

As a by-product from the metallurgical industry, steel slag contains a large amount of metal elements. In many developing countries, the output of steel slag is huge and the comprehensive utilization rate is low, hence the development of a novel application method for steel slag is of great significance to increase its utilization rate to improve the environment. This paper reviewed the dissolution behavior of Fe, P, Ca and silicate of steel slag under seawater and acidic solutions as an application in the cultivation of different microalgae, such as diatoms, spirulina, and chlorella. This review clarifies that proper pre-treatment of steel slag can effectively increase the dissolved elements of steel slag in the solution and provide more nutrients for the growth of microalgae. Microalgae cultivated with steel slag as a nutrient can be used to produce biodiesel which has a very broad application prospects for cleaner production and environmental protection.

The powertrain system is critical to the reliability of a battery electric vehicle (BEV). However, the BEV powertrain is a complex system; it includes the motor, motor controller, power distribution unit, battery system, etc. The failure of any of these components may result in the failure of the entire powertrain system and eventually cause serious traffic accidents on the road. However, how much does each component affect the reliability of the entire system, and which components are the most vulnerable in the entire system? These questions are still unanswered today. To develop a reliability design for a BEV powertrain system, it is essential to conduct detailed research by investigating the most vulnerable component parts of the entire powertrain. In the present study, a fault-tree model of the entire powertrain and its subsystems was developed. Based on this model, the failure rates of all components were calculated first. Then, trends in the reliability indices for the entire pow... [more]

Through the previous study a hydrothermal polymerization (HTP)—a catalytic methodology for treating various biomass and organic wastes—has been developed on a lab scale with a 1 L reactor and the results published. The research work described herein aims to ensure that the catalytic process is scalable for pilot and even commercial scale plants. A 1700 L binary reactor system has been built and the assumptions of a commercial scale plant that would have 10,000 to 20,000 L pressure vessels tested. The HTP catalytic biofuel process converts mono- and polysaccharides into a solid polymer fuel that is based on a furfuraldehyde ring system. The calorific value of the material obtained from the pilot plant is on the order of 27 MJ/kg and the material typically has low ash and fixed carbon content order of 48% which are about same as the lab results for various wood biomass feedstocks. Though a 1700 times scale up binary reactor system the scalability of the HTP catalytic methodology has been... [more]

The gasoline/natural gas dual-fuel combustion mode has been found to have unique advantages in combustion. The ignition timing has a significant impact on the combustion characteristics of gasoline engines. Thus, here we study the combustion characteristics of gasoline/natural gas dual-fuel combustion mode to determine the details of their respective advantages under cooperative combustion. A direct-injection turbocharged gasoline engine was modified, and an engine experimental platform was built for the coordinated control of gasoline direct-injection and natural gas port injection. A low-speed and low-load operating point was selected, and the in-cylinder pressure, heat release rate, pressure rise rate, combustion temperature, ignition delay, and combustion duration under the coordinated combustion of gasoline and natural gas dual fuel at the ignition moment were studied through bench tests among other typical combustion parameters. The results show that with the increase of the igni... [more]

In this study, the pressure drop and heat transfer characteristics of smooth tube and internal helically micro-finned tubes with two different fin-to-fin height ratios i.e., equal fin height and alternating fin height, are computationally analysed. The tube with alternating fin height is analysed for proof of concept of pressure drop reduction. A single phase steady turbulent flow model is used with a Reynolds number ranging from 12,000 to 54,000. Water is used as working fluid with inlet temperature of 55 °C and constant wall temperature of 20 °C is applied. Friction factor, heat transfer coefficient, Nusselt number, and Thermal Performance Index are evaluated and analysed. The numerical results are validated by comparison with the experimental and numerical data from literature. The results showed that the thermal performance is enhanced due to helically finned tube for a range of Reynolds numbers, but at the expense of increased pressure drop as compared to a smooth tube. The helica... [more]

Waste cooking oil (WCO) from palm oil is one of the most prospective biodiesel feedstock when compared to other oil seeds. Thus, WCO has great potential as a green source of diesel fuel for engines in motor vehicles and machinery. This project aimed to study the potential of three randomly selected types of WCO, namely; sample A (used 1× once to fry an egg), sample B (used 3−5× to fry salted fish), and sample C (used repeatedly to fry banana fritter) for the production of green diesel fuel over Ni-Mo/AC (nickel and molybdenum oxides incorporated with activated carbon) catalyst through the deoxygenation (DO) process. The prepared catalyst was characterized through X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). The DO process was performed at 350 °C to remove oxygen from the WCO samples. The liquid products were analysed by gas chromatography-mass spectrometer (GC-MS) and gas chromatography-flame ionization detector (GC... [more]

The boiling performance of functionalized hybrid aluminum surfaces was experimentally investigated for water and self-rewetting mixtures of water and 1-butanol. Firstly, microstructured surfaces were produced via chemical etching in hydrochloric acid and the effect of the etching time on the surface morphology was evaluated. An etching time of 5 min was found to result in pitting corrosion and produced weakly hydrophilic microstructured surfaces with many microcavities. Observed cavity-mouth diameters between 3.6 and 32 μm are optimal for efficient nucleation and provided a superior boiling performance. Longer etching times of 10 and 15 min resulted in uniform corrosion and produced superhydrophilic surfaces with a micropeak structure, which lacked microcavities for efficient nucleation. In the second stage, hybrid surfaces combining lower surface energy and a modified surface microstructure were created by hydrophobization of etched aluminum surfaces using a silane agent. Hydrophobize... [more]