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Abstract The transportation of hydrogen is a weak link in the large‐scale development of the hydrogen energy industry. Injecting hydrogen into the natural gas pipeline network for transportation is an efficient way to achieve the large‐scale, long‐distance, and low‐cost transportation of hydrogen. Hydrogen can lead to hydrogen embrittlement in natural gas pipelines and cause safety incidents if hydrogen and natural gas are not mixed uniformly. Therefore, it is necessary to study the blending process and blending uniformity of hydrogen and natural gas. In this study, a three‐dimensional model of the hydrogen‐injected natural gas pipeline was constructed. The effects of hydrogen injection inlet and turbulator configuration on the mixing process of hydrogen and natural gas were investigated using a computational fluid dynamics approach. The results show that increasing the number of hydrogen injection inlets shortens the distance L98% of uniform mixing of hydrogen and natural gas. Increasing the radial distance r from the initial hydrogen mixing positions to the center of the pipeline will shorten the distance for uniform gas mixing in the pipeline. The addition of turbulator configurations in the pipeline significantly reduces the distance to uniform gas mixing. Changing the distance Lturb from the turbulator to the initial mixing position further shortens the distance between hydrogen and natural gas mixing uniformly. The results of this study provide a reference for the structural design of the hydrogen–natural gas mixing pipeline and the gas distribution state during the mixing process.

Hydrogen mixing in existing natural gas pipelines efficiently achieves large-scale, long-distance, and low-cost hydrogen delivery. The physical properties of hydrogen and natural gas differ significantly. Hydrogen-mixed natural gas modifies the flow state and thermodynamic properties of the original natural gas in the pipeline. Hydrogen-mixed natural gas can lead to increased errors in ultrasonic flow metering because of the high sound speed and low density of hydrogen. Ultrasonic flowmeter installation distances need to be re-determined. In this study, a Lamb wave non-contact ultrasonic gas flow meter is used to measure the flow of hydrogen-mixed natural gas in a T-type pipeline. The greater the hydrogen mixing ratio, the higher the flow rate of the branch pipeline, and the shorter the installation distance of the ultrasonic flow meter, for example, 10% at 150D, 20% at 110D, and 30% at 20D. The time-difference method with high accuracy and broad applicability is used to calculate the flow rates of COMSOL simulated values. The errors between COMSOL simulation and theoretical flow rates at the shortest installation distance downstream do not exceed 3%. The errors at the position where the mixing uniformity is 80% are significantly higher than those at the shortest installation distance, and the maximum error is about 7.7%. The COMSOL simulation results show the feasibility and accuracy of ultrasonic gas flow metering of hydrogen-mixed natural gas.

Overuse of fossil energy has accelerated the development of industrialization and improved the quality of human life. However, it also leads to the excessive emission of CO2, and the greenhouse effect is threatening global climate stability and human health. Various countries have implemented measures and initiatives to promote carbon emission reduction and the carbon cycle. Chemical capture and utilizing CO2 generated by fossil energy combustion has proved an efficient and valuable method. This review describes the recent progress in synthesizing high-value-added oxazolidinones from CO2 as a C1 source. Firstly, the development and value of oxazolidinones are discussed, and the necessity of finding efficient and green chemical synthesis methods for oxazolidinones is proved. Furthermore, the significance of the CO2 cycloaddition reaction in the green and efficient synthesis of oxazolidinones is introduced, and we summarize and compare various transition metal-based and organic-based reaction systems that catalyze the cycloaddition reaction of CO2 to oxazolidinones. In order to achieve potential industrial applications, the significance of novel heterogeneous catalysts, such as atomically dispersed catalysis for the CO2 reduction reaction, is expounded by comparing the characteristics of homogeneous and heterogeneous catalysis. Finally, the interaction mechanism of cycloaddition reaction between CO2 and N-propargylamine is discussed in the metallic and metal-free catalytic system, which provides insights for the precise design and control of the reaction and promotes the further development of catalytic systems.

Energy saving is one of the main technique routes for net zero carbon emissions. Air compressor systems take up a large part of energy consumption in the industrial field. A pre-cooling air compressor system was proposed for energy saving by cooling the air before it flows in a compressor. The energy efficiency of the proposed system was analyzed. As additional energy consumption is required for air cooling, the feasibility of the pre-cooling method for energy saving was analyzed. As the efficiency of the pre-cooling air compressor system is mainly influenced by the environment temperature and humidity, applicability of the system in different regions and at different seasons was discussed. A pilot project was performed to verify the technical feasibility and economics of the proposed system. When the precooling temperature of the pilot system was set to 2 °C, the annual pneumatic-electrical ratio of the system can be increased by approximately 2% in several regions of China. This paper shows the pre-cooling air compressor system is feasible for energy saving.

With the significant increase in demand for artificial intelligence, environmental map reconstruction has become a research hotspot for obstacle avoidance navigation, unmanned operations, and virtual reality. The quality of the map plays a vital role in positioning, path planning, and obstacle avoidance. This review starts with the development of SLAM (Simultaneous Localization and Mapping) and proceeds to a review of V-SLAM (Visual-SLAM) from its proposal to the present, with a summary of its historical milestones. In this context, the five parts of the classic V-SLAM framework—visual sensor, visual odometer, backend optimization, loop detection, and mapping—are explained separately. Meanwhile, the details of the latest methods are shown; VI-SLAM (Visual inertial SLAM) is reviewed and extended. The four critical techniques of V-SLAM and its technical difficulties are summarized as feature detection and matching, selection of keyframes, uncertainty technology, and expression of maps. Finally, the development direction and needs of the V-SLAM field are proposed.

Water-spray-cooled quasi-isothermal compressed air energy storage aims to avoid heat energy losses from advanced adiabatic compressed-air energy storage (AA-CAES). The compression efficiency increases with injection water spray. However, the energy-generated water spray cannot be ignored. As the air pressure increases, the work done by the piston and the work converted into heat rise gradually in the compression process. Accordingly, the flow rate of the water needed for heat transfer is not a constant with respect to time. To match the rising compression heat, a time sequence of water-spray flow rate is constructed, and the algorithm is designed. Real-time water-spray flow rate is calculated according to the difference between the compression power and heat-transfer power. Compared with the uniform flow rate of water spray, energy consumption from the improved flow rate is reduced.

We report a novel synthesis of monodisperse samples of copper telluride with crystallinity and stoichiometry corresponding to forms of rickardite, Cu3−xTe2 (x < 1). This synthesis makes use of a ligand balanced reaction to allow control over shape and size by varying the relative and absolute concentration of oleylamine to stearic acid. The rickardite samples presented here display size dependent plasmon peaks in the near infrared and direct energy band gaps between 1.7 and 2.3 eV. As such they may find utility in photovoltaic, thermoelectric or as novel optical materials for study of surface plasmons.

Magnetic flux leakage (MFL) detection is one of the most popular methods of pipeline inspection. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. This paper introduces the main principles, measurement and processing of MFL data. As the key point of a quantitative analysis of MFL detection, the identification of the leakage magnetic signal is also discussed. In addition, the advantages and disadvantages of different identification methods are analyzed. Then the paper briefly introduces the expert systems used. At the end of this paper, future developments in pipeline MFL detection are predicted.

We report on the synthesis of CuInTe2 nanoparticles and their function in photovoltaic equipment, such as solar cells. Under certain synthesis conditions, the CuInTe2 nanocrystals form shape with nanocrystals, nanorods or nanocubes. It was found that CuTe nanocrystals could be converted to CuInTe2 by addition of an In reactant. CuInTe2 nanorods were synthesized using this method.

Compressed air energy storage (CAES) has emerged as an effective large-scale energy storage technology. This storage system can have many urban applications based on the time-dependent price of electricity. In China, the electric power companies employ batteries to store electricity when the price drops and generate electricity when the price increases. When compared with storage batteries, CAES systems have larger storage capacity (100 MWh, battery < 10 MWh), are more environmentally friendly (no heavy metals pollution), and have longer service life. However, the major limitation that restricts the application of such systems is its poor (<60%) turnaround efficiency (electricity to electricity). Most CAES systems are based on adiabatic compression. Approximately half of the electricity is transformed into heat and exhausted due to the poor heat transfer from the air to environment. Most of the previous research focused on enhancing the heat transfer to achieve quasi-isothermal compression. In this study, a contact heat transfer method is used to cool the compressed air by injecting micron-sized (10–100 μm) water spray into the compressed air. A transient temperature measurement method is developed to investigate the heat transfer behaviour between air and water. The measurements showed the spray-air heat transfer rate to lie in the range of 10–120 W·m −2 ·K −1 . When the compression ratio is two in a compression chamber of 0.94 L, the compression power is reduced from 73.8 J/cycle (adiabatic) to 69.0 J/cycle, using water injection of 0.416 g/cycle. The achieved compression efficiency is improved from 86.7% (adiabatic) to 92.4%. [ABSTRACT FROM AUTHOR]

• This study proposes an isothermal piston formed with a gas-solid-liquid three-layer heat transfer structure. • The porous medium works as a medium to enhance the heat transfer from air to environment. • The isothermal piston could improve the compression efficiency. • Dimensionless parameters Ka and Xu is obtained to analyze the system. Currently, Compressed Air Energy Storage systems mainly use adiabatic compression. Compared with isothermal compression, approximately twice the electricity is transformed into heat. Twice the heat passed into heat exchange mediums leads to twice the heat transfer losses. Enhancement of the heat transfer between air and environment to achieve isothermal compression is an effective approach to improve the turnaround efficiency of CAES systems. An isothermal piston structure is proposed to do isothermal compression. One end of the isothermal piston is connected to a traditional piston, and the other end dips into a liquid medium in the bottom of a cylinder. This forms a gas–solid–liquid three-layer heat transfer structure. A porous medium is used to enhance the heat transfer from the air to the liquid. As the heat capacity of the liquid is much greater than that of the air, the temperature of the liquid remains unchanged as well as the compressed air. A new method is proposed to look at the thermodynamics of the compressor with two dimensionless parameters Ka and Xu. Ka describes the extent of the compressor approaching isothermal. When Ka is over 80, the temperature of the air is reduced by 80% compared with adiabatic condition. In the case of using an aluminum porous medium, the compression efficiency increases by 11% at the compression ratio of 7 and the speed of 1200 r/min. [ABSTRACT FROM AUTHOR]