Explore the vast range of titles available.

Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A2B7-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La2-xYxNi6.50Mn0.33Al0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.

This work is devoted to the study of the processes that take place in the welding gap during explosive welding (EW). In the welding gap, when plates collide, a shock-compressed gas (SCG) region is formed, which moves at supersonic speed and has a high temperature that can affect the quality of the weld joint. Therefore, this work focuses on a detailed study of the parameters of the SCG. A complex method of determining the SCG parameters included: determination of the detonation velocity using electrical contact probes, ceramic probes, and an oscilloscope; calculation of the SCG parameters; high-speed photography of the SCG region; measurement of the SCG temperature using optical pyrometry. As a result, it was found that the head front of the SCG region moved ahead of the collision point at a velocity of 3000 ± 100 m/s, while the collision point moved with a velocity of 2500 m/s. The calculation of the SCG temperature showed that the gas was heated up to 2832 K by the shock compression, while the measured temperature was in the range of 4100–4400 K. This is presumably due to the fact that small metal particles that broke off from the welded surfaces transferred their heat to the SCG region. Thus, the results of this study can be used to optimize the EW parameters and improve the weld joint quality.

Icebreaking by using underwater explosion bubbles and compressed high-pressure gas bubbles has gradually become an effective icebreaking method. In order to compare the damaging effect of these two methods on the ice body, a fluid–structure coupling model was established based on the arbitrary Lagrangian–Eulerian (ALE) method and a series of calculations were carried out. The morphological changes of underwater explosion bubbles and compressed gas bubbles at the same energy under the free surface; the changes of flow load near the rigid wall; and the damage caused to the ice plate were studied and compared. The damage effect of the ice plate was analyzed by detecting the number of failure elements of the ice plate, and the optimum standoff distance was found. For an ice plate with a radius of 0.19 m and a thickness of 0.15 m, the optimum standoff distance of the compressed gas bubbles with 120 J is 0.03 m, and the optimum standoff distance of the TNT with 120 J is 0.02875 m. The similarities and differences of the two sources of bubbles on ice plate damage were summarized.

The article analyzes the modern theory and practice of transportation and storage of compressed natural gas. The expediency of the inclusion of a floating storage berth for the loading of gas carriers and container ships into the infrastructure of marine transportation of compressed natural gas is considered. Requirements for storage berth are formulated. It is shown that without using a marine mooring storage facility, the loading time of a gas carrier will considerably increase, and the economic efficiency of compressed gas transportation will lower due to the considerable time of loading and unloading of a gas carrier. The construction of a storage berth is proposed, and calculations of storage parameters and calculation of its buoyancy are made. The possibility of using the REFPROP vs. 9.1 software package to automate the selection of the composition of a multicomponent hydrocarbon mixture for further use at the selected range of temperatures and pressures is substantiated. The use of the system is considered in the example of phase equilibrium of a multicomponent hydrocarbon mixture.

Hybrid fuel for the operation of diesel engine is the motivated research in this study. The diesel engine is modified to operate with the hybrid diesel and compressed natural gas (CNG). In this work a four stroke, single cylinder diesel engine is considered to operate at variable load and speed. At is operation condition the emission characteristics are measured to model the proposed Manhattan K-nearest neighbor (MKNN) technique. The MKNN is modelled to effectively analysis and predict the torque, brake power, exhaust emissions and break specific fuel consumption (BSFC). The MKNN is modelled with the constant K=3 and applied Manhattan distance formula for neighbor determination. From the result analysis it is evident that the proposed MKNN technique can effectively predict the engine performance and exhaust emission while the usage of hybrid fuel.

The application of compressed natural gas (CNG) as fuel for compression ignition (CI) engines under dual-fuel (DF) mode operation is not attempted in countries like India for commercial purposes. A commercial heavy-duty turbocharged six-cylinder common-rail direct-injected diesel engine has been converted into a DF mode of operation using CNG and diesel for its potential usage and study on its performance along with Selective Catalytic Reduction (SCR). CNG is inducted through the intake manifold at varying energy substitution rates (ESR) with a flow rate of 0.67-1.54 kg/h while diesel fuel is controlled through the engine electronic control unit (ECU). For a maximum ESR of 10.2% with CNG, an increase in power by 8.9% and a 5.8% increase in torque were observed. While there was an increase in brake thermal efficiency (BTE), volumetric efficiency marginally decreased, therefore, to have higher brake power with a DF engine, a dedicated turbocharging system is necessary. The brake-specific energy (BSEC)/fuel consumption (BSFC) has marginally reduced by 1%, and optimum engine speed for better fuel economy was in the range of 1250-2250 rpm. The brake-specific carbon monoxide (BSCO) and carbon dioxide (BSCO₂) emissions have considerably reduced while brake-specific non-methane hydrocarbon (BSNMHC), oxides of nitrogen (BSNOx), and methane (BSCH₄) emission was marginally higher with CNG substitution; however, within Euro 4 emission norms. Unregulated emissions like ammonia (NH₃), propane, and sulfur dioxide (SO₂) have reduced while formaldehyde, acetylene, ethylene, and formic acid have marginally increased. SCR has been useful in reducing mass emissions out from the diesel engine and in conversion.

Hydrogen, an emerging low-carbon energy carrier, is pivotal for high-penetration renewable energy and integrated energy systems, yet the coupling of hydrogen with electricity and gas for hydrogen production and enriched compression-integrated systems remains a key issue for energy transition. This study establishes the architecture and analyzes the energy flow of an urban hydrogen production and enriched compressing-integrated energy system, as well as models its hydrogen production-enriched compressing, power, and hydrogen-enriched compressed natural gas subsystems based on water electrolysis, hydrogen storage, hydrogen fuel cells (HFCs), and hydrogen-enriched compressed natural gas (HCNG) technology, and develops a low-carbon optimal scheduling model with demand response to minimize intraday economic dispatch costs. Scenario comparisons verify the model’s effectiveness, showing that the system boosts wind-solar utilization by 6.81% and cuts carbon emissions by 1.89%.

Compressed natural gas (CNG) taxis represent the most ubiquitous and dynamically active passenger vehicles in urban settings. The pollutant emission characteristics of in-use CNG taxis driving on a typical mountain city before and after three-way catalyst (TWC) replacement was examined using a modular on-board portable emissions measurement system (PEMS), the OBS-ONE developed by Horiba. The results showed that the exhaust NO of CNG taxis equipped with deactivation TWC exceeded the emission limits, even higher than gasoline vehicles. The high emission rate of CNG taxis is mainly concentrated on road slopes between a 2% and 6% gradient and a deceleration rate in the interval of [0.5, 4], respectively, which results in higher emissions from CNG taxis traveling in the mountain city of Chongqing than other cities and vehicles. Moreover, the pollutant emission rates of the in-use CNG taxis were highly correlated with the velocity and the vehicle specific power (VSP). After a new TWC replacement, the emission factors of carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NOx), and particle number (PN) decreased by 85.21–89.11%, 68.71–85.49%, 60.91–81.11%, and 62.26–68.39%, respectively. Our results will provide guidance for urban environments to carry out the comprehensive management of in-use vehicles and emphasize the importance of TWC replacement for CNG taxis.

Transporting green hydrogen by existing natural gas networks has become a practical means to accommodate curtailed wind and solar power. Restricted by pipe materials and pressure levels, there is an upper limit on the hydrogen blending ratio of hydrogen-enriched compressed natural gas (HCNG) that can be transported by natural gas pipelines, which affects whether the natural gas network can supply energy safely and reliably. To this end, this paper investigates the effects of the intermittent and fluctuating green hydrogen produced by different types of renewable energy on the dynamic distribution of hydrogen concentration after it is blended into natural gas pipelines. Based on the isothermal steady-state simulation results of the natural gas network, two convection–diffusion models for the dynamic simulation of hydrogen injections are proposed. Finally, the dynamic changes of hydrogen concentration in the pipelines under scenarios of multiple green hydrogen types and multiple injection nodes are simulated on a seven-node natural gas network. The simulation results indicate that, compared with the solar-power-dominated hydrogen production-blending scenario, the hydrogen concentrations in the natural gas pipelines are more uniformly distributed in the wind-power-dominated scenario and the solar–wind power balance scenario. To be specific, in the solar-power-dominated scenario, the hydrogen concentration exceeds the limit for more time whilst the overall hydrogen production is low, and the local hydrogen concentration in the natural gas network exceeds the limit for nearly 50% of the time in a day. By comparison, in the wind-power-dominated scenario, all pipelines can work under safe conditions. The hydrogen concentration overrun time in the solar–wind power balance scenario is also improved compared with the solar-power-dominated scenario, and the limit-exceeding time of the hydrogen concentration in Pipe 5 and Pipe 6 is reduced to 91.24% and 91.99% of the solar-power-dominated scenario. This work can help verify the day-ahead scheduling strategy of the electricity-HCNG integrated energy system (IES) and provide a reference for the design of local hydrogen production-blending systems.

Pakistan is developing South Asian country which is currently considering alternative energy sources including coal, solar, compressed natural gas, and wind energy to cope with the worst energy crisis in its history. Moreover, the policy promotion of compressed natural gas especially in the transport sector has raised concerns about the demand management of natural gas to avoid future shortages and ensure sustainable use of this precious non-renewable source of energy. Against this background, this study aimed to forecast natural gas demand in Pakistan for the 2016–2030 period by applying relevant univariate time series econometric methods. Apart from forecasting the overall natural gas demand, the forecasting analysis is also conducted for natural gas demand in Pakistan’s total natural gas consumption and also for natural gas consumption across the household, industrial, commercial, transport, fertilizer production, power generation, and cement production sectors. Overall, the findings revealed that ARIMA is the appropriate model for forecasting gas consumption in Pakistan. Further, the growth of increase in the level of compressed natural gas consumption in the household sector is more as compared to all other sectors of the economy up to the year 2030. The key findings show that (a) natural gas consumption is likely to grow with time, (b) mixed projection trends are observed for the overall natural gas consumption and other sector-based natural gas consumption trends, and (c) the difference between natural gas consumption and production in Pakistan is likely to grow leading to 2030. As part of the policy recommendation in line with the findings, policymakers in Pakistan should increase the availability of natural gas, particularly in sectors where its consumption is likely to be declining. In addition, more proactive measures should be undertaken to explore the existing natural gas reserves in the long run while also importing natural gas from the neighboring nations in the short run. Furthermore, the government of Pakistan should seriously consider strategizing the development of the nation’s compressed natural gas sector.