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Sensitivity in polymer-bonded explosives (PBXs) relies on the presence of defects, such as cracks and voids, which create localized thermal energy, commonly known as hotspots, and initiate reactions through various localization phenomena. Our prior research has explored the use of internal gas pressure induced by thermite ignition to generate localized defects for PBX sensitization. However, further research is required to gain a more comprehensive understanding of the defect generation process resulting from internal gas pressure. This study investigates the process of defect generation in PBXs in response to internally induced gas pressure by applying controlled compressed gas to a fabricated cavity within the materials, simulating the gas pressure emitting from thermite. X-ray micro-computed tomography was employed to visualize the microstructure of the sample before and after gas injection. The experiments reveal the significance of gas pressure, cavity shape, temperature, and specimen compaction pressure in the defect generation. Numerical simulations using Abaqus/Standard were conducted to assess the defect generation in mock PBXs under varying gas pressures, cohesive properties, and binder thicknesses. The simulation results demonstrate the substantial influence of these properties on the ability to generate defects in mock PBXs. This study contributes to a better understanding of the factors influencing defect generation in mock PBXs. This knowledge is crucial for achieving precise control over defect generation, leading to improved ignition and detonation characteristics in PBXs. [ABSTRACT FROM AUTHOR]

Quantum many-body scars are notable as nonthermal, low-entanglement states that exist at high energies. In this study, we used attractively interacting dysprosium gases to create scar states that are stable enough to be driven into a strongly nonlinear regime while retaining their character. We measured how the kinetic and total energies evolve after quenching the confining potential. Although the bare interactions are attractive, the atoms behave as if they repel each other: Their kinetic energy paradoxically decreases as the gas is compressed. The missing “phantom” energy is quantified by benchmarking our experimental results against generalized hydrodynamics calculations. We present evidence that the missing kinetic energy is carried by undetected, very high momentum atoms. [ABSTRACT FROM AUTHOR]

Introduction Inhaled nitric oxide (INO) is a selective pulmonary vasodilator delivered from compressed gas cylinders filled to 2,200 psig (137.8 bar) with 800 ppm of NO in a balance of nitrogen. NO is currently FDA-approved for use in term or near-term infants with hypoxemia and signs of pulmonary hypertension in the absence of cardiac disease. INO has also been shown to improve oxygenation in adults with refractory hypoxemia. Current doctrine precludes the use of NO during military aeromedical transport owing to the requirement for large compressed gas cylinders. We performed a bench evaluation of 2 delivery systems that create NO from room air without the need for pressurized cylinders, Materials and Methods We evaluated 2 portable nitric oxide INO generation systems (LungFit PH, Beyond Air Inc, Garden City, NJ and a prototype NO generator, Odic Inc, Littleton, MA) at ground level, 8,000, and 14,000 feet (2,437 and 4,267 meter) simulated altitude in an altitude chamber. The output from each device was injected into the inspiratory limb of the ventilator circuit that was attached to a test lung. A 731 ventilator (Zoll Medical, Chelmsford, MA) and T1 (Hamilton Medical, Reno, NV) were used employing 24 combinations of ventilator settings each repeated in duplicate. An INOmax DS IR was used to measure delivered INO and NO2 via a sampling line attached in the ventilator circuit inspiratory limb. A fast response oxygen analyzer (O2CAP, Oxigraf Inc, Sunnyvale, CA) was used to measure inspired FiO2. Target INO concentration was 20 ppm. Results Across all ventilator settings, the LungFit device delivered INO was 19.8 ± 1.6 ppm, 16.1 ± 1.9 ppm, and 11.6 ± 1.7 ppm at ground level, 8,000 ft (2,437 meter), and 14,000 ft (4,267 meter), respectively. The Odic device delivered INO dose was 20.6 ± 1.4 ppm, 21.3 ± 5.5 ppm, and 20.4 ± 9.1 ppm at ground level, 8,000 ft (2,437 meter), and 14,000 ft (4,267 meter), respectively. Conclusions Both devices delivered a reliable INO dose at ground level. Altitude significantly affected INO delivery accuracy at 14,000 ft (4,267 meter) (P  < 0.01) with both devices and at 8,000 ft (2,437 meter) (P  < 0.01) with LungFit. Differences in INO dosage were not statistically significant with the Odic device at 8,000 ft (2,437 meter)(P  > 0.05) although there were large variations with selected ventilator settings. With careful monitoring, devices creating INO from room air without cylinders could be used during aeromedical transport without the need for pressurized cylinders. [ABSTRACT FROM AUTHOR]

Hydrogen has enormous potential for sustainable future mobility. However, current challenges include high production costs and storage issues, necessitating further engineering advancements. Compressed Natural Gas is also a viable alternative, as it is easily produced and stored but suffers from slow flame speed-related issues. Improving its combustion characteristics by enrichment using a small fraction of hydrogen holds significant promise. Inducting hydrogen directly into the combustion chamber improves the engine's volumetric efficiency, eliminating the backfire issues. However, it is crucial to understand the test fuel's jet and mixing characteristics before engine investigations. This study aims to analyse the macroscopic jet characteristics of hydrogen, compressed natural gas and hydrogen-enriched compressed natural gas in realistic engine-like conditions in a constant volume spray chamber at various fuel injection pressures and varying ambient pressures and temperatures. Fuel injection pressures for hydrogen and CNG were varied at 16, 32, and 48 bar, and ambient pressures in the constant volume spray chamber were set at 4- and 8-bar and ambient temperatures at 25 and 100 °C. The results showed hydrogen exhibited ∼2% shorter jet penetration length than compressed natural gas. Depending on the test conditions, hydrogen showed a ∼1–3% higher jet area than CNG due to its higher diffusivity and faster mixing. This higher jet area improved fuel-air mixing of hydrogen with air compared to CNG. The effect of hydrogen enrichment with CNG on their jet characteristics was also analysed for 8 bar FIP. 10% (v/v), 20%, and 40% hydrogen-enriched compressed natural gas did not significantly alter the macroscopic jet characteristics from baseline compressed natural gas. [Display omitted] • Macroscopic spray characterization of hydrogen and CNG in CVSC using Schlieren. • FIP for hydrogen and CNG was varied at varying ambient pressures/temperatures. • Hydrogen exhibited a ∼2% shorter spray jet penetration length than CNG. • Hydrogen showed a larger spray area than CNG. • Hydrogen enrichment of CNG didn't alter macroscopic spray characteristics. [ABSTRACT FROM AUTHOR]

Transition of global energy market towards an environment‐friendly sustainable society requires a profound transformation from fossil fuel to zero carbon emission fuel. To cope with this goal production ofrenewable energy is accelerating worldwide. Research in renewable energy from production and storage to practical utilization requires an organized approach. One of the best renewable energy carrier is the hydrogen, due to its clean combustion and abundance. Nonetheless, its storage is a critical challenge to its success. Hydrogen must be stored long after being produced and transported to a storage site. Physical hydrogen storage is vital among hydrogen storage modes, and its shortcoming needs to overcome for its successful and economic benefits. This review intends to discuss the techniques and applications of physical hydrogen storage in the state of compressed gas, liquefied hydrogen gas, and cold/cryo compressed gas concerning their working principle, chemical and physical properties, influencing factors for physical hydrogen storage, and transportation, economics, and global outlook. Insights of several probable physical hydrogen storage (PHS) systems are highlighted. The outcomes of this review envisioned that the PHS still necessitates technological advancements despite having remarkable success. The Liquid Hydrogen Gas storage marks better sustainability than Compressed and Cryo Compressed Gas. The physical hydrogen storage method can store hydrogen in tanks in any state (liquid or gas) under 20 K for the liquid state and ambient temperature for the gaseous state The Bibliographic analysis depicts that the research in hydrogen rising with time and mostly the research in conducted in USA with 231 articles. Prospects and challenges with lessons learned and the limitation opens the door to further research, which would be helpful for efficient and long‐term physical hydrogen storage. [ABSTRACT FROM AUTHOR]

A fuel gas from rice husk gasification "a producer gas" has a good potential as a compressed producer gas (CPG) fuel. However, cleaning of the producer gas has to be performed to reduce tar content before compressing into cylinder. The present work aims to investigate performance of spray scrubber on tar removal and energy density of CPG from rice husk gasification. The performance of the scrubber is evaluated at different adsorbent and spray pressure. The adsorbents used are water and waste of cooking oil under spray pressure of 2, 4, 6, and 8 bar. The data taken during the experimental work are producer gas and adsorbent temperatures, gas composition, and gravimetric tar. The data are used to analyze performance of the scrubber in terms of tar removal and cooling effectiveness, and energy density of CPG. The results show that water spray scrubber has higher effectiveness than waste of palm oil scrubber. Pressure of the spray also impacts scrubber's performance in reducing tar content. Scrubber's effectiveness improves as stepping up spray pressure. At spray pressure of 6 bar for water scrubber and 8 bar for waste of cooking oil scrubber, the gravimetric tar was 83.33 mg/Nm3 and 83 mg/Nm3 which are suitable for vehicular fuel. The highest tar removal effectiveness of the scrubber is found at spray pressure of 8 bar which are 0.94 and 0.75 for water spray scrubber and waste palm oil scrubber. The highest energy density of the CPG of 2.57 MJ/Nm3 is obtained at water spray pressure of 6 bar. [ABSTRACT FROM AUTHOR]

Isentropic (adiabatic) compression of superheated vapor in vapor compression refrigeration cycles usually results in some discharge superheat, i.e. the discharge temperature exceeding the condensing temperature. Large discharge superheat reduces both operating range and compression efficiency. Sub-isentropic compression with heat rejection to the heat sink is therefore superior to adiabatic compression, as it results in lower discharge superheat and improved efficiency. However, significant temperature reduction by heat transfer through the working chamber walls is difficult to facilitate in common refrigeration compressors, particularly reciprocating compressors. Refrigerant and oil injection is a well-established method for reducing temperatures and increasing efficiency in screw and scroll compressors, as well as multi-stage systems. In comparison, effective methods for temperature reduction in single-stage reciprocating compressors are fairly limited. Therefore, a concept for high-pressure liquid injection is proposed. By means of a pump and injection valve, high-pressure liquid refrigerant is injected into the working chamber and atomized. The compressed gas is cooled through the evaporation of the injected liquid. The injection valve allows for control over the injection timing and quantity, enabling adjustment of the temperature profile, which is a major distinction from existing refrigerant injection methods. The coupled compression-injection process is evaluated for various refrigerants using an energetic chamber model. The injection is found to be particularly suitable for refrigerants with a large evaporation heat and a shallow dew line slope. For the example of ammonia, a theoretical reduction in compression work of 8.9% at an evaporation temperature of −10 °C and a condensing temperature of 45 °C is found. • Proposal of high-pressure liquid injection for reciprocating compressors. • Theoretical evaluation using energetic chamber model. • Potential for significant efficiency improvement compared to isentropic compression. • Increased operating range due to reduced discharge temperature. [ABSTRACT FROM AUTHOR]

For a gas undergoing a compression process, it is more appropriate to think of either isentropic or polytropic efficiency as process-defining parameters indicating that a given end state of compression has been achieved, rather than a measure of effectiveness of conversion of one form of energy into another. The polytropic efficiency, as defined in ASME PTC-10 standard for compressor field trials and acceptance tests, actually involves the comparison of two distinct compression processes, neither of which are actually connected to the performance of the compressors producing them. Consequently, it is not rational to compare the ASME PTC-10 polytropic efficiency of a compressor designed to compress a gas predominantly adiabatically with that for a compressor designed to compress a gas predominantly isothermally. A framework correcting this situation is set out and is illustrated with several numerical examples. Suggestions for maintaining backward compatibility with ASME PTC-10 are also put forward. [ABSTRACT FROM AUTHOR]

The importance of the energy transition and the role of green hydrogen in facilitating this transition cannot be denied. Therefore, it is crucial to pay close attention to and thoroughly understand hydrogen storage, which is a critical aspect of the hydrogen supply chain. In this comprehensive review paper, we have undertaken the task of categorising and evaluating various hydrogen storage technologies across three different scales. These scales include small-scale and laboratory-based methods such as metal-based hydrides, physical adsorbents, and liquid organic hydrogen carriers. Also, we explore medium and large-scale approaches like compressed gaseous hydrogen, liquid cryogenic hydrogen, and cryocompressed hydrogen. Lastly, we delve into very large-scale options such as salt caverns, aquifers, depleted gas/oil reservoirs, abandoned mines, and hard rock caverns. We have thoroughly examined each storage technology from technical and maturity perspectives, as well as considering its techno-economic viability. It is worth noting that development has been ongoing for each storage mechanism; however, numerous technical and economic challenges persist in most areas. Particularly, the cost per kilogramme of hydrogen for most current technologies demands careful consideration. It is recommended that small-scale hydrogen storage technologies such as metal hydrides (e.g., MgH 2 , LiBH 4) need ongoing research to enhance their performance. Physical adsorbents have limited capacity except for activated carbon. Some liquid organic hydrogen carriers (LCOHs) are suitable for medium-scale storage in the near term. Ammonia-borane (AB), with its high gravimetric and volumetric properties, is a promising choice for medium-scale storage, pending effective dehydrogenation. It shows potential as a hydrogen carrier due to its high storage capacity, stability, and solubility, surpassing DOE targets for storage capabilities. Medium-scale storage, utilising compressed gas cylinders and advancements in liquefied and cryocompressed hydrogen storage, requires cost reduction measures, and a strategic supply chain. Large-scale storage options include salt caverns, aquifers, and depleted gas/oil reservoirs, with salt caverns offering pure hydrogen, need further techno-economic analysis and deployment projects to mature, but storage costs are reasonable, ranging mostly from €0.25/kg to €1.5/kg for location specific large-scale options. • Comprehensive review of hydrogen storage technologies from small to very large scale. • Metal hydride MgH 2 shown to be economically viable with storage at €2.8 per kg. • Ammonia-borane (AB) offers promising medium-scale hydrogen storage potential. • Technological advancements are enhancing compressed gas hydrogen storage systems. • Large-scale hydrogen storage costs vary between €0.25 and €1.58 per kg. [ABSTRACT FROM AUTHOR]

In quasi-two-dimensional conditions, different invasion patterns can be observed when a fluid displaces another fluid with a higher viscosity. The transition from interfacial instability to fracture during gas invasion remained poorly understood, and classification criteria for different invasion patterns demanded further improvement. In this study, single-point compressed gas injection experiments were conducted in magnesium lithium phyllosilicate (MLPS) suspensions in a rectangular Hele-Shaw cell. Interestingly, with the increase of the injection pressure and the decrease of the concentration of MLPS suspension, the gas invasion pattern underwent a transition from viscous elastic fracture, elastic fracture, elastic viscous fingering to viscous fingering, in which viscous elastic fracture was observed for the first times. We detailly discuss the characteristics and occurrence conditions of each invasion pattern. Furthermore, by analyzing the velocity field of each invasion pattern, it is found that the relationship between the velocity direction around the gas and the gas growth direction varies with different invasion patterns. A simple and effective quantitative indicator is constructed to distinguish the different invasion patterns. Following the identification of invasion patterns, a further investigation was conducted into the relationship between invasion patterns and experimental conditions. By utilizing the relationships among injection conditions and material rheological properties, two dimensionless numbers, Bingham number and Weissenberg number, are conducted, which have an impact on the various invasion patterns and invasion process. A unified phase diagram based on the Bingham number and Weissenberg number was also proposed to incorporate the possible gas invasion patterns in the MLPS suspension. [ABSTRACT FROM AUTHOR]

In this paper, a novel concept of a finned piston system is presented and analyzed in which the compression heat is continuously extracted from the compression chamber. The resulting compression characteristic moves in the direction of an isothermal process, reducing the temperature of the compressed fluid in the compression chamber and reducing the necessary mechanical work required to carry out the process. The finned piston concept consists in an integrated heat exchanger inside of the chamber that is constituted of imbricated flat fins placed on the stator part and on the mobile piston. The internal heat exchange on the surface is strongly increased in comparison with a classical piston/cylinder. The energetic performance of the new system is evaluated with the help of simulation. The pressures, forces, and temperature of the compressed gas are simulated as well as the mechanical work needed. The different curves are compared with the system's adiabatic and isothermal characteristics. [ABSTRACT FROM AUTHOR]

Introduction: Tasmania is a small island state off the southern edge of Australia where a comparatively high proportion of the 558,000 population partake in recreational or occupational diving. While diving is a relatively safe sport and occupation, Tasmania has a significantly higher diving death rate per head of population than other States in Australia (four times the national diving mortality rate). Methods: Three compressed gas diving deaths occurred in seven months between 2021-2022 prompting a review of the statewide approach for the immediate response of personnel to diving-related deaths. The review engaged first responders including the Police Marine and Rescue Service, hospital-based departments including the Department of Hyperbaric and Diving Medicine, and the mortuary and coroner's office. Results: An aide-mémoire for all craft groups, digitalised checklists for first responders (irrespective of diving knowledge), and a single-paged algorithm to highlight inter-agency communication pathways in the event of a diving death were designed to enhance current practices and collaboration. Conclusions: If used, these aids for managing diving related deaths should ensure that time-critical information is appropriately captured and stored to optimise information provided for the coronial investigation. [ABSTRACT FROM AUTHOR]

The results of diagnostic tests under steady-state speed conditions of an unloaded engine do not fully reflect the emissivity of vehicles adapted to run on natural gas. Therefore, it is reasonable to pay attention to the emissions performance of these vehicles under dynamic conditions. In this regard, the tests were carried out on a chassis dynamometer with the engine fueled by gasoline and natural gas. Due to the area of operation of natural gas vehicles being usually limited to urban areas, the urban phases of the NEDC (New European Driving Cycle) and WLTC (Worldwide harmonized Light-duty vehicles Test Cycle) were adapted. While CO2 emissions are lower when fueled by natural gas, CH4 emissions can be high, which is related to momentary changes in the composition of the combustible mixture. Although CH4 emissions are higher when the engine runs on natural gas, the CO2eq value is, depending on the driving cycle, about 15–25% lower than when running on petrol. Additionally, studies have shown that in engines adapted to run on CNG (compressed natural gas), it is advisable to consider the use of catalytic converters optimized to run on natural gas, as is the case with vehicles which are factory–adapted to run on CNG. [ABSTRACT FROM AUTHOR]

Despite the deployment of alternative fuel vehicles (AFVs) being one of the promising measures to reduce air pollutants and greenhouse gas emissions, AFVs still represent a very small share in the heavy-duty vehicle (HDV) sector. Understanding HDV fleet operator perspectives on alternative fuels is critical to developing effective demand-side strategies to facilitate wider and more rapid adoption of heavy-duty AFVs. This study explored California HDV fleet operator perspectives on viable alternative fuel options in the next 10–20 years, along with motivators for, and barriers to, such adoption. Eighteen in-depth qualitative interviews were conducted, after which thematic analysis was employed to analyze the interview data. Electric, hydrogen, compressed natural gas (CNG), and hybrid options were commonly perceived as viable in the 2030s by the participating organizations. Various optimistic aspects were addressed, including advanced technologies and emission reduction benefits (electric/hydrogen), continued fuel commitments due to their fleet or infrastructure investments already made (CNG), and lower complexity in fleet routing along with favorable driver acceptance (hybrid options). However, many concerns and uncertainties were also reported, including functional unsuitability (electric), uncompetitive upfront costs (hydrogen), unready infrastructure, perceived unavailability of vehicles, uncertain return on investment (electric/hydrogen), and unpromising support from state government (CNG). The study findings help fill a key knowledge gap in AFV fleet adoption research regarding HDV fleet operator perspectives, and contribute to developing demand-side strategies to aid the success of AFV diffusion throughout the HDV market. • Electricity, hydrogen, CNG, and hybrid options were perceived as viable to some extent. • Various positive or negative remarks were identified across diverse fuel technologies. • Motivators included advancing technologies, emission benefits, and continued commitments. • Concerns included functional unsuitability, unready infrastructure, unavailability, and costs. • Recommendations were suggested for policymakers seeking to accelerate the adoption. [ABSTRACT FROM AUTHOR]

The work is aimed at improving thermomechanical compressors designed to provide recondensation systems of cryogenic liquids. A promising field of use of thermocompressors can be the river tanker fleet designed for the transportation of cryogenic products, for example, liquefied gas. High-pressure throttle cycles are usually used in gas recondensation refrigeration units. Known schemes of liquefied natural gas recondensers in tanks of medium and small capacity based on single-stage cryogenic gas machines (CGM). They implement the reverse Stirling cycle, and the working medium is helium. The resource of single-stage CGM Stirling is limited. In addition, they do not exclude the leakage of helium due to the sealing of the compressor piston. Promising gas coolers are Gifford cryogenerators with a remote compressor. Their advantage is the reduction of the number of moving nodes and points of potential refrigerant (helium) leakage. The use of Gifford coolers allows utilization of low-temperature heat by thermome-chanical compression of the working fluid. The principle of operation of thermomechanical compressor units is based on the consumption of thermal energy to compress gases and mechanical energy to drive the compressor itself. It is proposed to use the energy resources of cold and heated streams on LNG tankers or LNG bunkering vessels. The low-temperature flow is vaporized gas taken from the tank in the form of main engine fuel or formed in the bunkering process. The warm source can be outboard water or engine exhaust gases. The introduction into practice of a new type of coolers based on the combined use of thermocompressors and gas cryogenerators will make it possible to increase the period of undrained storage of low-temperature liquids and reduce the volume of potential emissions. [ABSTRACT FROM AUTHOR]

We present a compact closed-loop recycling system for noble and inert gases. It has been developed for an extreme-ultraviolet (XUV) frequency comb based on high-harmonic generation at 100 MHz repetition rate. The system collects gas injected at several bars of backing pressure through a micrometer-sized nozzle into the laser-interaction region with a differential pumping system comprising turbomolecular pumps, and subsequently compresses the gas to a pressure of up to 200 bar. By drastically reducing the waste of expensive gases such as xenon and krypton, it enables the long operation times needed for spectroscopic measurements, as well as for continuous operation of the XUV frequency comb. [ABSTRACT FROM AUTHOR]

As one of the potential explosions and inflammation, compressed natural gas (CNG) stations in urban areas cause irreparable losses and casualties. Estimating risk assessment in gas stress based on coherent uses can reduce accidents in urban areas. The purpose of the present study was to estimate a small risk estimation at one of the CNG multipurpose stations, LPG, using combined models of the Fuzzy Bayesian Network, Bow-tie Diagram, and consequence modeling. This study was conducted based on the basic and 25 intermediate events. This study formed a seven-person safety team to identify the primary events and build the Bow-tie diagram. Then, because of the lack of a proper database, fuzzy theory was used to determine the probability of significant events. Bayesian networks were drawn based on the Bow-tie model using GeNLe software. Finally, the main events of the two Bow-tie, Bayesian network modeling, and risk estimation were performed with the help of PHAST/SAFETI (V8.22). The geographical information system software was used to zone the explosion effects. The Risk assessment result showed that the social risks and the Bayesian network model are more than Bow-tie, and the Bow-tie diagram is unacceptable. Therefore, using incompatible land uses in the vicinity of the CNG stations gives rise to the effects of accident scenarios in particular residential and administrative land uses, which decision-makers and city managers should consider. Based on the findings of this study, the obtained results can be utilized to implement effective control measures. These measures encompass devising a response plan tailored to address specific emergency conditions and conducting comprehensive training programs for the individuals and residents residing within the study area. [ABSTRACT FROM AUTHOR]

Alternative fuels in spark-ignition engines significantly reduce engine exhaust emissions and improve fuel efficiency. This research investigates the performance of a multicylinder SI engine using 10%, 20% (ethanol, methanol, methyl acetate), and 100% compressed biomethane gas (CBG) as alternative fuels. Engine performance parameters (BTE, ITE, ME, BP), BSFC, ISFC, FF, combustion phenomenon (cylinder pressure, crank angle, cylinder volume, mass fraction burned, net heat release, mean gas temperature, cumulative heat release, rate of pressure rise), and emission characteristics (HC, CO, CO2, NOx) are measured. CBG achieved a maximum BTE of 23.33% compared to all other fuels. Minimum fuel consumption rate of 1.72 kg/h at maximum rpm achieved BSFC value of 0.44 kg/kWh and ISFC value of 0.261 kg/kWh. The highest cylinder pressure of 6.79 bar was achieved in the G90M10 with a cylinder volume of 48.58 cc. NHR of 3.08 j/deg was found in the G80M20 at a crank angle of 376°, and the maximum MGT was 390.20 °C in the G80E20. The highest CHR values of 0.12 kJ at crank angles of 432°, 420°, 422°, and 427° were achieved in the G100, CBG, G80E20, and G90E10. G90M10 reached a maximum value of 0.14 bar/degree of rate of pressure rise at a crank angle of 374°. Average minimum emission gas was found in CBG at a minimum and maximum RPM, indicating that CBG gives the best emission result with engine performance compared to all alternative fuels. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are carbon‐containing chemicals that may evaporate rapidly at room temperature and standard pressure. Such organic compounds can be preserved inside carbonaceous chondrite matrices. However, unlike meteoritic soluble organic matter (SOM) and insoluble organic matter (IOM), VOCs are typically lost (at least in part) during sample processing (meteorite crushing) and exposure to terrestrial atmosphere and/or solvents. Like SOM and IOM, VOCs can provide valuable insights into the chemical inventory of the meteorite parent body and even the presolar cloud from which our solar system formed, as well as the composition and processes that occurred during the early formation of our solar system and the asteroidal stage. Thus, in this work, we designed and built an instrument that allowed us to access the VOCs present in samples of the carbonaceous chondrites Murchison and Sutter's Mill after mineral disaggregation by means of freeze–thaw cycling. We simultaneously evaluated the abundances and compound‐specific 13C‐distributions of the volatiles evolving after meteorite powdering at ~20, 60, and 100°C. Carbon monoxide (CO) and methane (CH4) were released from these meteorites as the most abundant VOCs. They were combusted together for analysis and showed positive δ13C values, indicative of their extraterrestrial origins. Carbon dioxide (CO2) was also an abundant VOC in both meteorites, and its isotopic values suggest that it was mainly formed from dissolved carbonates in the samples. We also detected aldehydes, ketones, and aromatic compounds in low amounts. Contrary to Murchison, which mostly yielded VOCs with positive δ13C values, Sutter's Mill yielded VOCs with negative δ13C values. The less enriched 13C isotope composition of the VOCs detected in Sutter's Mill suggest that they are either terrestrial contaminants, such as VOCs in compressed gas dusters and common laboratory solvents, or compounds disconnected from interstellar sources and/or formed through parent body processing. Understanding the relative abundances and determining the molecular distributions and isotopic compositions of free meteoritic VOCs are key in assessing their extraterrestrial origins and those of chondritic SOM and IOM. Our newly developed technique will be valuable in the study of the samples brought to the Earth from carbonaceous asteroid Bennu by NASA's OSIRIS‐REx mission. [ABSTRACT FROM AUTHOR]

Methane storage performance of a series of metal‐organic frameworks (MOFs) has been thoroughly examined over a wide pressure range up to 750 bar. Based on volumetric adsorption measurements, crystal structure and porous texture characterization, excess, total and working adsorption capacities, and heat of adsorption as functions of pressure have been evaluated. It has been found that the use of MOFs demonstrates a significant advantage in methane storage capacity over compressed gas, and the Gain can reach 300% to 400% depending on the pressure‐temperature operating conditions. However, the benefit of adsorption storage drops with increasing pressure. Even for the best MOF adsorbent, this methane storage method becomes technologically unreasonable above 280 bar. The data obtained allowed us to conclude that conventionally reported excess adsorption does not give a complete picture of the effectiveness of MOFs. Besides high specific surface area, optimal density of the skeleton and moderate heat of adsorption are required for the best storage performance. [ABSTRACT FROM AUTHOR]

The research is centered on energy production and harvesting to facilitate the transformation of electrical energy with energy-independent sensor systems, using powering devices in the expected power range of P = 10–10,000 W. A model application case for a harvester is the conversion of energy stored in the compressed gas during expansion; such gas embodies the energy stored in scenarios such as braking a car using an auxiliary pump. Similar systems find use in sensing various quantities in the transport sector (bridge structures, infrastructural components, cars, and other objects). The proposed theoretical harvester models describing the transformation of linear motion energy into electricity provide relevant support for the experiments. In the given context, the results obtained in the designing and construction of a robust motion generator with a primarily linear geometry-based system technology are presented, too. The expected output of electrical power of an N-segment harvester within the tested type is variable, and the design exploits the rectilinear motion generated by an engine using compressed air, a small fuel system, and similar options to obtain an expected/adjustable N-segment power in the range of Psm = 10–500 W. The fundamental structure of the generator core has been continuously numerically modeled, and an experimental setup has been developed to analyze the specific parts and variations in order to validate the concept and to achieve the most suitable parameters with the selected construction materials (a power yield increase of up to 2000 times). A scaled-down version of the model principle was tested in the experiments, and the parameters and results were compared with the predicted theoretical analyses. Generally, the conceptual layout of an enhanced magnetic circuit layout transforming motion energy into electricity was presented and verified. [ABSTRACT FROM AUTHOR]

Ram-pressure stripping (RPS) is the mechanism most often invoked to explain the observed differences between cluster and field galaxies. In the local Universe, its effect on the star-forming properties of the galaxies has been largely elucidated and the general consensus is that this process first compresses the gas available in galaxy disks, boosting the star formation for a limited amount of time, and then removes the remaining gas, leading to quenching. Much less is known about the effect and preponderance of RPS at higher redshifts, due to the lack of statistical samples. Exploiting VLT/MUSE observations of galaxies at 0.2 < z < 0.55 and a published catalog of ram-pressure-stripped galaxies, we compare the global star formation rate–mass (SFR–M*) relation of 29 cluster galaxies undergoing RPS to that of 26 undisturbed field and cluster galaxies that constitute our control sample. Stripping galaxies occupy the upper envelope of the SFR–M* relation of the control sample, showing a systematic enhancement of SFR at any given mass. The boost is > 3σ when considering the SFR occurring in both the tail and the disk of the galaxies. The enhancement is also seen on local scales: Considering spatially resolved data, ram-pressure stripped galaxies have large ΣSFR values overall, especially for Σ* > 107.5 M⊙ kpc−2. RPS seems to leave the same imprint on the SFR–M* and ΣSFR–Σ* relations both in the local Universe and at z ∼ 0.35. [ABSTRACT FROM AUTHOR]

Economical hydrogen storage and transportation contribute to hydrogen energy utilization. In this paper, for economically distributing hydrogen from the hydrogen plant to the terminal hydrogen refueling station, considering the daily hydrogen demand and transportation distance, firstly a comprehensive techno-economic analysis of the point-to-point hydrogen storage and transportation system based on compressed gas hydrogen (GH), liquid hydrogen (LH), pipeline hydrogen (PH), and liquid organic hydrogen carriers (LOHC) is investigated, respectively. The optimal economical point-to-point energy storage and transportation modes under various transportation distance and daily hydrogen demand are obtained. Then the economic analysis of different hydrogen storage and transportation modes under 1-to-N hydrogen storage and transportation scenario is conducted, which can significantly decrease the cost of LH storage and transportation mode. To step further, the 1-to-N relay hydrogen storage and transportation scenario is constructed to improve the applicability and reduce the unit cost. The economic analysis of 14 kinds of feasible combinations of hydrogen storage and transportation modes is systematically assessed. Regarding to the transportation distance and daily hydrogen demand, the optimal economical 1-to-N relay energy storage and transportation modes are identified. This study may contribute to rationally design and application for economic hydrogen storage and transportation systems. [Display omitted] • The economics of point-to-point hydrogen storage and transportation scenario is investigated. • The economics of the 1-to-N hydrogen storage and transportation scenario is analyzed. • 1-to-N relay hydrogen storage and transportation scenario is constructed to improve economic applicability. • 1-to-N relay hydrogen storage and transportation scenarios may exhibit obvious economic advantage. [ABSTRACT FROM AUTHOR]

This study presents a systematic workflow for estimating hydrogen storage capacity for a smooth energy transition from natural gas market to hydrogen market to achieve net-zero emissions. The workflow establishes maximum and minimum thresholds for hydrogen storage and considers appropriate storage techniques, including underground or surface facilities. The technique assesses environmental footprint of each storage technique and evaluates associated emission reductions. We apply this workflow to energy market in Alberta and project minimum and maximum storage thresholds of 0.28 and 5 megatonne/year (Mt/year) by 2050. Under three distinct storage scenarios, the storage capacity necessitates 128 salt caverns, 10 million compressed gas tanks, or 78,150 cryogenic liquefied tanks. Salt cavern storage emerges as a promising choice owing to its relatively lower emissions of 0.16 MtCO 2 e/year and a land footprint of 2.56 km2. The net emission reduction achieved is 1.47 MtCO 2 e/year, equivalent to 0.8% of Canada's target emission reduction of 190 MtCO 2 e/year by 2050. • A workflow is developed to forecast required hydrogen storage capacity in Alberta. • Salt caverns emerge as a reliable and practical technique for large-scale hydrogen storage. • The workflow projects the required number of salt caverns for hydrogen storage. • Supplying stored hydrogen to market reduces 1.5 megatonne/year of GHG emissions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The global energy landscape faces significant challenges, necessitating a transition toward alternative energy sources to mitigate energy consumption and greenhouse gas emissions. Hydrogen emerged as a versatile energy carrier with immense potential, particularly in the realm of transportation. However, the lack of a comprehensive hydrogen infrastructure poses a critical barrier to its widespread adoption. By examining various important factors including the pressure level, transported capacity, trailer capacity, pipeline diameter, pressure drop, and transport distance, this study aims to optimize the hydrogen supply chain and improve the cost‐effectiveness of compressed hydrogen gas transportation. Five major delivery modes, encompassing compressed gas trucks and pipelines of varying diameters, are evaluated. This research offers valuable insights into the costs associated with hydrogen delivery within the European context. It reveals that the total levelized cost of hydrogen transportation (LCOHT) ranges from 0.3 to 3.44 € kg−1. These cost fluctuations are observed over transport distances that extend from 25 to 500 km and are dependent upon varying hydrogen demand levels, encompassing quantities of up to 100 000 kg per day. Based on the results, optimal choices for transport infrastructure are identified considering factors such as distance and hydrogen demand. [ABSTRACT FROM AUTHOR]

Pressure pulsations and vibrations generated in gas discharge pipelines are one of the main causes of failure in a compressed gas system. Installation of shaped nozzles in the compressor discharge manifold is one of the new ideas to minimize this phenomenon. It has been proven that shaped nozzles technology is able to minimize the unfavorable phenomena of pressure pulsation and thus the pipeline vibration. The production of such components using 3D printing techniques is a very good solution, as they have complicated shapes and are individually produced for a specific installation. The world is currently struggling with an excess of waste and a shortage of energy. Therefore, modern technology should be part of the sustainable development strategy, according to which the amount of energy consumed during the processes should be reduced. This article presents the influence of shaped nozzles on the specific compression power mounted in the discharge manifolds of two different compressors: reciprocating and screw. This influence can also be estimated by a conceptual model presented in the article. Based on the values of specific compression power, obtained during carried out research, it can be concluded that 3D printed nozzles may have a minor impact on the energy efficiency of compression depending on their shape complexity. [ABSTRACT FROM AUTHOR]

Biogas from anaerobic digestion is a versatile energy carrier that can be upgraded to compressed biomethane gas (CBG) as a renewable and sustainable alternative to natural gas. Organic residues and energy crops are predicted to be major sources of bioenergy production in the future. Pre-treatment can reduce the recalcitrance of lignocellulosic energy crops such as Salix to anaerobic digestion, making it a potential biogas feedstock. This lignocellulosic material can be co-digested with animal manure, which has the complementary effect of increasing volumetric biogas yield. Salix varieties exhibit variations in yield, composition and biomethane potential values, which can have a significant effect on the overall biogas production system. This study assessed the impact of Salix varietal differences on the overall mass and energy balance of a co-digestion system using steam pre-treated Salix biomass and dairy manure (DaM) to produce CBG as the final product. Six commercial Salix varieties cultivated under unfertilised and fertilised conditions were compared. Energy and mass flows along this total process chain, comprising Salix cultivation, steam pre-treatment, biogas production and biogas upgrading to CBG, were evaluated. Two scenarios were considered: a base scenario without heat recovery and a scenario with heat recovery. The results showed that Salix variety had a significant effect on energy output–input ratio (R), with R values in the base scenario of 1.57–1.88 and in the heat recovery scenario of 2.36–2.94. In both scenarios, unfertilised var. Tordis was the best energy performer, while the fertilised var. Jorr was the worst. Based on this energy performance, Salix could be a feasible feedstock for co-digestion with DaM, although its R value was at the lower end of the range reported previously for energy crops. [ABSTRACT FROM AUTHOR]

The flow field around the grinding wheel prevents grinding fluid from entering the grinding area, which deteriorates machining conditions and reduces the quality of the workpiece. MQL (Minimum Quantity Lubrication) grinding uses compressed gas to improve the ability of the grinding fluid to pass through the flow field of the grinding wheel so that a small amount of the grinding fluid can meet the cooling and lubrication requirements and reduce the cost of using grinding fluid. In this study, we investigated the flow field of grinding wheels under MQL conditions and obtain the rules that influence factors such as grinding fluid flow rate, grinding wheel linear speed and compressed gas pressure affect the flow rate of grinding fluid. The simulation method was used to simulate the flow field of the grinding wheel and the trajectory of the grinding fluid droplets. The simulation results show that these factors are important ones affecting the effective flow rate of grinding fluid. Meanwhile, the experimental results verify that these factors have the same influence pattern on the effective flow rate and grinding temperature. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Isobaric expansion (IE) engines can directly convert heat into mechanical energy, making them particularly attractive for applications such as vapor-driven pumps and compressors. A recent initial assessment investigating the utilization of IE engines as vapor-driven reciprocating compressors has revealed that the vapor use efficiency is inherently low in the case of the simplest direct-acting compressor designs. Based on this analysis, it was anticipated that multistage compression can offer significant advantages for vapor-driven compressors. Therefore, this paper aims to conduct a comprehensive analytical thermodynamic analysis of direct vapor-driven multistage reciprocating compressors. The analysis considers processes without intercooling and processes with intercooling of the compressed gas between stages. The findings demonstrate that, for vapor-driven compression, the benefits of multistage compression are superior to those known for conventional compression processes. Multistage vapor-driven compression not only reduces compression work and temperature elevation but, more importantly, mitigates the adverse effects on vapor compression of the driving vapor, thereby enabling a substantial improvement in vapor utilization efficiency. Furthermore, the total volume of the IE engine compressor experiences a significant decrease with an increasing number of stages. Consequently, under specific process parameters, the overall dimensions of the engine-compressor system may also decrease as the number of stages increases. The results offer significant opportunities for energy savings in energy-intensive compression processes by replacing electrical energy with readily available low-grade heat sources (<100 °C). Such processes include hydrogen, air, and ethylene compression at high pressure. [ABSTRACT FROM AUTHOR]

The present investigation on a hydrodynamic study focused on the RPM and pressure drop in a pressure swing rotating bubble cap (PSRBC) sparger column. PSRBC is one of its kind, which has the capability of producing bubbles and effective mixing in the sparged column. In this experimental work, a plastic PSRBC sparger of cylindrical shape has been designed and used for the supply of compressed gas (air) through the stationary liquid (water-glycerine solution) pool. The system variables viz. superficial air velocity, stationary liquid height, column diameter, the viscosity of liquid and sparger outlet opening area are considered for this study. Model equations have been developed for predicting RPM for the PSRBC sparger and pressure drop of the column in dimensionless form. The calculated values from predicted models have been compared with the experimental values and the coefficients of correlations are found to be more than 0.97. The present hydrodynamic study relates to RPM and pressure drop and may be useful for the design of gas-liquid systems viz. bubble columns, deaerators, bio-reactors (without stirrer) etc. where the interfacial area of gas-liquid has a distinct role in the performance. [ABSTRACT FROM AUTHOR]

The oil and gas sector is important to the global economy because it covers the exploration, production, processing, transportation, and distribution of oil and natural gas resources. Despite constant innovation and development of technologies to improve efficiency, reduce environmental impact, and optimize operations in the gas and oil industry over the last few decades, there is still room to increase the efficiency of the industry's equipment in order to reduce its carbon footprint. The separation of gas from oil is a critical stage in the technological production chain, and it is carried out using high-performance multi-phase separators to limit greenhouse gas emissions and have a low impact on the environment. In this study, an improved gas–oil separator configuration was established utilizing CFD techniques. Two separator geometry characteristics were studied. Both cases have the same number of subdomains, two porous media, and four fluid zones, but with a difference in the pitch of the cyclone from the inlet subdomain. The streamlines in a cross-plan of the separator and the distribution of the oil volume fraction from the intake to the outlet were two of the numerical results that were shown as numeric outcomes. The validation of these results was performed using an experimental testing campaign that had the purpose of determining the amount of lubricating oil that is discharged together with the compressed gas at the separator outlet. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) are considered a promising energy source in the field of transport and distributed power generation. Fundamental research into their key components is needed to improve PEMFC performance and accelerate commercialization. Binder addition and compression induced by assembly pressure can significantly change the microstructure of the gas diffusion layer and affect mass transport. A two-dimensional multicomponent lattice Boltzmann (LB) model considering the cathode electrochemical reaction was developed, and a GDL was reconstructed numerically and considering a binder structure. The effects of the binder and compression on mass transport and electrochemical performance within the GDL were investigated. The results showed that an increase in binder volume fraction led to more chain-like structures and closed pores that were unfavorable for mass transport. Compression increased the mass transfer resistance of the GDL in the region under the rib, leading to a decrease in oxygen concentration and local current density. [ABSTRACT FROM AUTHOR]

Investigations of a prototype positive-displacement piston hybrid power machine having two suction valves showed that the cooling-fluid flow rate is maximum at a compressed gas discharge pressure of 0.5 MPa. Elevation of discharge pressure leads to a decline in machine performance on both suction and discharge and a decrease in delivery coefficient. The components of the delivery coefficient and the physical mechanisms of their change were disclosed. Analysis of the effect of discharge pressure on the temperature of the cylinder-piston group parts revealed that there is a significant nonuniformity of temperature distribution along the cylinder generatrix, which reaches 26 K. This nonuniformity increases with increase of crankshaft speed. The maximum value of the indicator isothermal efficiency of the studied machine is observed at 0.5 MPa discharge pressure. [ABSTRACT FROM AUTHOR]

A method was developed for determining the mass of compressed gas and the supplied indicated work of the compressor and pump during compression, both for regenerative and recuperative heat exchange. On the basis of a certain mass of compressed gas supplied to the consumer and the supplied indicated work, coefficients were proposed that characterize the efficiency and economic efficiency of using regenerative heat exchange in comparison with recuperative heat exchange for cooling the compressor. [ABSTRACT FROM AUTHOR]

Underwater compressed gas energy storage (UW-CGES) holds significant promise as a nascent and viable energy storage solution for a diverse range of coastal and offshore facilities. However, liquid accumulation in underwater gas pipelines poses a significant challenge, as it can lead to pipeline blockages and energy transmission interruptions and adversely impact pipeline operation. In this paper, experimental and Oil and Gas Assays (OLGA) simulation studies have been conducted on the formation process of slug flow in pipelines. Firstly, experiments are conducted to capture high-speed camera images of slug flow under various liquid accumulation volumes and inclination angles. Subsequently, an OLGA model is developed to verify the experimentally observed flow regime, pressure, and slugging speed. Therefore, the flow regime verification results exhibit substantial consistency, and pressure variations display uniform trends, with an average slugging velocity error of 6.42%. The results indicate that the formation of slug flow involves three distinct stages: slug flow growth, ejection, and backflow. By analyzing slug flow, it can gain insights into the relationship between pressure and slug flow formation, exposing the sensitivity of this phenomenon to pressure fluctuations. These results further enhance recognition of the operational status of UW-CGES pipelines and provide support for safe operation. [ABSTRACT FROM AUTHOR]

This paper proposes a techno-economic model for a high-speed hydrogen ferry. The model can describe the system properties i.e. energy demand, weight, and daily operating expenses of the ferry. A novel aspect is the consideration of superconductivity as a measure for cost saving in the setting where liquid hydrogen (LH 2) can be both coolant and fuel. We survey different scenarios for a high-speed ferry that could carry 300 passengers. The results show that, despite higher energy demand, compressed hydrogen gas is more economical compared with LH 2 for now; however, constructing large-scale hydrogen liquefaction plants make it competitive in the future. Moreover, compressed hydrogen gas is restricted to a shorter distance while LH 2 makes longer distances possible, and whenever LH 2 is accessible, using a superconducting propulsion system has a beneficial impact on both energy and cost savings. These effects strengthen if the operational time or the weight of the ferry increases. • Superconducting ferry consumes the least amount of hydrogen. • Hydrogen in gas form is more appropriate for short distances and lighter ferries. • The high energy demand for compressed hydrogen gas ferries restricts their usage. [ABSTRACT FROM AUTHOR]

This work highlights the recent advancements in the hydrogen value chain for the Middle East region by evaluating the feedstock, production technologies, storage options, delivery routes, and end-user applications. It discusses the national strategies for implementing the hydrogen value chain in the Middle East from 2020 to 2050. The challenges in the hydrogen value chain from techno-economic, safety, and social perspectives are also discussed in this study. Hydrogen production technologies are analyzed and compared. Steam-methane reforming has a high efficiency of 74% and a low hydrogen cost of $2.27/kg-H 2 , making it the most dominant technology for hydrogen production. Electrolysis has a lower efficiency of 60% and a higher hydrogen cost of $10.30/kg-H 2, with more potential for further improvments. Furthermore, hydrogen storage options are compared. Compressed gas and cryogenic liquid options have the highest storage capacities of 39.2 and 70.9 kg/m3, respectively. However, they are not entirely safe due to the high flammability of hydrogen. Two hydrogen explosion incidents are also reported, the first explosion at the Fukushima nuclear power plant in 2011 and the second in the Hindenburg fire in 1937. Metal hydrides propose a safer and more effective option, but they are still under research and development. For H 2 transportation options, pipelines and cryogenic tankers are the most conventional and efficient options (above 99%). Ships have the largest capacity of 10,000 tons per shipment and the maximum investment costs of 465M - 620M$ per barge, but they are not feasible. This review paper will help researchers and practitioners analyze the hydrogen value chain in a more systematic way for further improvements toward more practical applications. • Several Middle East countries have developed national strategies for the hydrogen economy. • Steam-Methane Reforming is the most widely used method for hydrogen production. • Electrolysis and photolysis need major technical advances to be commercialized. • Hydrogen delivery infrastructure requires further development for a future hydrogen economy. • Hydrogen Value Chain implementation has some techno-economic and safety and social challenges. [Display omitted] [ABSTRACT FROM AUTHOR]

The dual-fuel combustion strategy using compressed natural gas (CNG) and diesel exhibits immense potential for improving conventional diesel engines. To reduce CO2 emissions, diesel should be substituted with CNG to the maximum extent possible. In this study, a numerical investigation was conducted using a three-dimensional computational model for cases with 97 % CNG substitution (CNG97), which has not been explored through experiments previously owing to the technical limitations of diesel injection systems. The simulation model was validated through experiments conducted under operating conditions similar to a diesel engine; the results revealed that ignition was initiated by the diesel fuel regardless of the CNG substitution rate. In the CNG97 case, ignition occurred near the center of the cylinder owing to short spray penetration. Consequently, the CNG remained inside the piston bowl and top crevice area. In addition, the small quantity of diesel weakened the initial stage of combustion. These two effects retarded combustion significantly, which caused substantial phasing loss in CNG97. Based on these findings, it was concluded that the diesel injector should be optimized for a high CNG substitution rate to reduce CO2 emissions effectively. [ABSTRACT FROM AUTHOR]

One of the most rational methods of energy utilization of compressed gas in pipelines is to use turbo-expander installations. In particular, these are autonomous turbo-expander power stations. A fundamentally new concept has been devised to improve the technical and economic performance of this type of machines. This concept is not focused on a separate aspect of the plant's operation but on their entire set. In particular, physical principles, structures, and technologies were considered as an object of research. First, effective parameters of gas-dynamic flows and heat-mass transfer were determined based on the modeling of work processes. Secondly, progressive designs of turbo-expander units have been created. Thirdly, technologies for the production of parts and assemblies of turbo-expander units have been developed, which combine, unlike the traditional ones, different types of strengthening for contacting parts in their pair. A method of parametric modeling was used to substantiate the technical solutions of the elements of turbo-expander power plants. This makes it possible to determine the technical characteristics of these installations under a certain set of parameters. By purposeful variation, a recommended set of their parameters was determined, which ensure the improvement of the most important technical characteristics. A specialized database was built, which contains an array of information about the regularities of the influence of variation of significant parameters on various characteristics of turbo-expander power plants. Already on this basis, the problems of synthesis of successful technical solutions of turbo-expander power plants are solved. As a result, their high energy efficiency is ensured. Thus, the efficiency of the expander was achieved at the level of 86 % while the resource increased by 20–25 %. All these solutions were implemented in a number of unique turbo-expander units. Their effectiveness has been demonstrated during operation [ABSTRACT FROM AUTHOR]

This study proposes a novel variable air pressure supply structure based on the electromagnetic effect. This structure can be implemented in various soft robots driven by air pressure, including pneumatic artificial muscles, pneumatic soft grippers, and other soft robots. The structure's main body comprises a hollow circular tube, a magnetic piston arranged in the tube, and an electromagnetic solenoid nested outside the tube. The electromagnetic solenoid is designed with special winding and power supply access modes, generating either an attractive force or a repulsive force on the magnetic piston. This solenoid conforms with the magnetic piston expectation in the tube by changing the polarity direction. The interior of the whole structure is a closed space. The gas is conveyed to the soft robot by the gas guide hoses at the two ends of the structure, and the expansion energy of the compressed gas is fully utilized. Then, the gas supply pressure is controlled to drive the robot. The mathematical model of the structure is established based on the analysis of the electromagnetic force and gas pressure on the piston. The simulation results show that the structure's inherent vibration characteristics under various parameters align with expectations. The real-time automatic optimization of the controller parameters is realized by optimizing the incremental proportional-integral-derivative (PID) controller based on a neural network. The simulation results show that the structure can meet the application requirements. The experimental results show that the proposed gas supply structure can provide a continuous pressure supply curve with any frequency in a specific amplitude range and has an excellent tracking effect on the sinusoidal-like pressure curve. [ABSTRACT FROM AUTHOR]

Supercritical CO2 phase change fracturing technology has been widely used in rock engineering. However, the surface vibration characteristics induced by phase change rock breaking have not been sufficiently studied. In this paper, a model for calculating the surface vibration velocity induced by supercritical CO2 phase change was established based on the time-domain recursive method, and the reliability of the model was verified using LS-DYNA nonlinear finite element software; based on the model for calculating the blasting energy of a compressed gas and water vapor container, the surface vibration velocity and decay law induced by CO2 phase change fracturing and equivalent explosive blasting were compared and analyzed. The results show that the ground vibration velocity calculation model based on the time-domain recurrence method can better evaluate the ground vibration characteristics induced by supercritical CO2 phase change fracturing, and the vibration velocity decays exponentially with the fracture distance; the peak pressure of supercritical CO2 phase change is only 1/3.36 of that of explosive blasting, but the action time is 100 times longer than that of explosive blasting, and the peak vibration velocity is 1/74~1/78 of that of equivalent explosive blasting. [ABSTRACT FROM AUTHOR]