Drop Shape Research Articles

CO2 rich cushion gas for hydrogen storage in depleted gas reservoirs: Insight on contact angle and surface tension

Hydrogen storage in porous media (aquifers and depleted reservoirs) is an effective means of achieving large-scale inter-seasonal demand for energy. In particular, the depleted gas reservoir provides substantial storage capacity and additional economic incentives due to the preexistence of the storage infrastructure as well as the requisite reservoir integrity. However, the interfacial phenomenon between the injected hydrogen, the native gas (cushion gas), the formation brine, and the host rocks require further investigation for efficient gas containment. In this study, we conducted a comprehensive examination of the application of CO2 as a cushion gas. Our investigation involved performing contact angle and surface tension experiments using the drop shape analyzer (DSA) 100 equipment. We examined various gas mixtures (H2–CO2 – CH4–N2) under different pressure ranges (500–3000 psi), temperature levels (30, 40, 50, 60, 70 °C), and salinities (2, 5, 10, 15, and 20 wt%).Results indicate that the wettability behavior of the studied gas-mixture compositions remains relatively consistent unless there are changes in the initial wetting state of the rock. The contact angles observed ranged from 29 to 51°, independent of reservoir pressure, temperature, and salinity. The contact angle values increased with higher pressure but decreased with higher temperature. Furthermore, the contact angle was lower for a gas mixture with a lower CO2 fraction compared to a gas mixture with a higher CO2 fraction. Conversely, the gas mixture brine surface tension exhibited a decrease with increasing pressure, temperature, and CO2 fraction. However, it increased with increasing salinity for all gas mixtures. Based on the results obtained from the contact angle and surface tension analysis, mixture 4 emerged as the ideal fraction for designing CO2 cushion gas in terms of both hydrogen storage and withdrawal. These findings present precise and valuable input parameters and data that can be utilized in reservoir-scale simulations to optimize geo-storage in depleted natural gas reservoirs.

Machine learning (ML)-assisted surface tension and oscillation-induced elastic modulus studies of oxide-coated liquid metal (LM) alloys

Pendant drops of oxide-coated high-surface tension fluids frequently produce perturbed shapes that impede interfacial studies. Eutectic gallium indium or Galinstan are high-surface tension fluids coated with a ∼5 nm gallium oxide (Ga2O3) film and falls under this fluid classification, also known as liquid metals (LMs). The recent emergence of LM-based applications often cannot proceed without analyzing interfacial energetics in different environments. While numerous techniques are available in the literature for interfacial studies- pendant droplet-based analyses are the simplest. However, the perturbed shape of the pendant drops due to the presence of surface oxide has been ignored frequently as a source of error. Also, exploratory investigations of surface oxide leveraging oscillatory pendant droplets have remained untapped. We address both challenges and present two contributing novelties- (a) by utilizing the machine learning (ML) technique, we predict the approximate surface tension value of perturbed pendant droplets, (ii) by leveraging the oscillation-induced bubble tensiometry method, we study the dynamic elastic modulus of the oxide-coated LM droplets. We have created our dataset from LM’s pendant drop shape parameters and trained different models for comparison. We have achieved >99% accuracy with all models and added versatility to work with other fluids. The best-performing model was leveraged further to predict the approximate values of the nonaxisymmetric LM droplets. Then, we analyzed LM’s elastic and viscous moduli in air, harnessing oscillation-induced pendant droplets, which provides complementary opportunities for interfacial studies alternative to expensive rheometers. We believe it will enable more fundamental studies of the oxide layer on LM, leveraging both symmetric and perturbed droplets. Our study broadens the materials science horizon, where researchers from ML and artificial intelligence domains can work synergistically to solve more complex problems related to surface science, interfacial studies, and other studies relevant to LM-based systems.

The shape of things to come: Axisymmetric drop shape analysis using deep learning

HypothesisIn the traditional approach to Axisymmetric Drop Shape Analysis (ADSA), the determination of surface tension or interfacial tension is constrained by computational speed and image quality. By implementing a machine learning-based approach, particularly using a convolutional neural network (CNN), it is posited that analysis of pendant drop images can be both faster and more accurate. ExperimentsA CNN model was trained and used to predict the surface tension of drop images. The performance of our CNN model was compared to the traditional ADSA, i.e. direct numerical integration, in terms of precision, computational speed, and robustness in dealing with images of varying quality. Additionally, the ability of the CNN model to predict other drop properties such as Volume and Surface Area was evaluated. FindingsOur CNN demonstrated a significant enhancement in experimental fit precision, predicting surface tension with an accuracy of (+/-) 1.22×10−1 mN/m and at a speed of 1.50 ms−1, outpacing the traditional method by more than 5×103 times. The model maintained an average surface tension error of 2.42×10−1 mN/m even for experimental images with challenges such as misalignment and poor focus. The CNN model also demonstrated showcased a high degree of accuracy in determining other drop properties.

From Biological Source to Energy Harvesting Device: Surface Protective Ionic Liquid Coatings for Electrical Performance Enhancement of Wood-Based Electronics.

This study explores task-specific ionic liquids (TSILs) in smart floor systems, highlighting their strong electrical rectification abilities and previously established wood preservative properties. Two types of TSILs, featuring a "sweet" anion and a terpene-based cation, were used to treat selected wood samples, allowing for a comparison of their physical and electrical performance with untreated and commercially treated counterparts. Drop shape analysis and scanning electron microscopy were employed to evaluate the surface treatment before and after coating. Near-IR was used to confirm the presence of a surface modifier, and thermogravimetric analysis (TGA) was utilized to assess the thermal features of the treated samples. The different surface treatments resulted in varied triboelectric nanogenerator (TENG) parameters, with the molecular structure and size of the side chains being the key determining factors. The best results were achieved with TSILs, with the instantaneous voltage increasing by approximately five times and the highest voltage reaching 300 V under enhanced loading. This work provides fresh insights into the potential application spectrum of TSILs and opens up new avenues for directly utilizing tested ionic compounds in construction systems.

Ultra-hydrophobic biomimetic transparent bilayer thin film deposited by atmospheric pressure plasma

An open-air atmospheric pressure plasma was used to deposit ultrahydrophobic bilayer coatings. The plasma set-up was tuned, allowing the successive injection in the post-discharge of two monomers. To the best of our knowledge, no study describes the successive deposition by atmospheric plasma of two precursors, which could work in synergy and allow designing composite coatings of high added value. In this study, two liquid precursors were chosen for the deposition of single and bilayer coatings: (i) hexamethyldisiloxane (HMDSO) and (ii) 1H,1H,2H,2H-perfluorooctyltriethoxysilane (pFOTES). Single layer coatings (HMDSO and pFOTES) as well as bilayer coating (HMDSO/pFOTES) were analysed using multiscale techniques: Scanning Electron Microscopy (SEM), profilometer, Atomic Force Microscopy (AFM), Fourier-Transformed Infrared Spectroscopy (FTIR), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and drop shape analysis. The bilayer system (HMDSO/pFOTES), resulting from the successive deposition of HMDSO and pFOTES precursors, was confirmed by ToF-SIMS characterization while contact angle measurements highlighted the ultrahydrophobic property of the bilayer: water was fully repelled, with a zero contact angle hysteresis. This resulted from the combination of the multiscale roughnesses of the HMDSO-based and pFOTES based layers, combined with the intrinsic hydrophobicity of the pFOTES layer.

Prediction of multi-bead profile of robotic wire and arc additive manufactured components recursively using axisymmetric drop shape analysis

ABSTRACT Dimension prediction of robotic wire and arc additive manufacturing (WAAM) part is fundamentally dependent on the modelling accuracy of single-bead profile and its subsequent overlapping ones. Current multi-bead overlapping models are still not capable of describing the flatten valley area of WAAM parts. This paper proposes a new recursive model, based on coordinate transformation and axisymmetric drop shape analysis (ADSA), to predict multi-bead overlapping profiles. First, a single-bead profile model for WAAM is established based on ADSA, followed by detailed description of conventional and proposed modified recursive ADSA profile model. The properties of developed recursive ADSA model are then investigated to reveal the effects of overlapping ratio and single-bead aspect ratio. Finally, multi-bead overlapping deposition experiment is carried out to validate the model feasibility. The results show that the modified recursive ADSA model is more accurate than the conventional one for its better accountability of valley areas. It is also indicated that the modified recursive ADSA model is suitable for the robotic WAAM process. The research outcome is beneficial to improving the forming accuracy of WAAM parts and geometry prediction of other additive manufactured products.

Dynamics of Drop Formation in the Presence of Interfacial Mass Transfer.

The dynamics of drop formation have been investigated in the presence of interfacial mass transfer through controlled flow visualization experiments. The mixtures of n-hexane (solvent) and acetone (solute) were used as a dispersed phase, having different initial compositions varying over a broad range. Drops were formed at the submerged position in the continuous phase (water) at the same operating flow conditions. The unsteady force balance model is developed to analyze the implications of the simultaneously occurring interfacial transfer of the solute on the formation dynamics in real time, and predictions are validated with experimental results. Based on initial compositions, the analysis of the transient drop shape shows a sharp transition in the drop formation regime. At lower initial solute concentrations, i.e., ϕ0 < 0.2, axisymmetric drop formation occurs and the interfacial solute transfer has negligible effects on the formation dynamics. Over an intermediate range of solute concentrations, i.e., 0.2 < ϕ0 < 0.5, Marangoni instability is triggered along the evolving interface, and therefore, the interface deformations and contractions occur during the drop formation. At ϕ0 = 0.5, the drop takes highly nonaxisymmetric shapes and remains away from equilibrium until its detachment from an orifice. For ϕ0 > 0.5, the spontaneous ejection of plumes of the solute results in the rapid generation of multiple droplets of smaller size. This work shows that higher solute concentration gradients not only lead to faster solute transport but also induce strong interfacial instability simultaneously. Thus, the coupled effects of transient change in composition and fluid properties govern the drop size and its formation time in such systems under non-equilibrium.

One Material-Opposite Triboelectrification: Molecular Engineering Regulated Triboelectrification on Silica Surface to Enhance TENG Efficiency.

Molecular engineering is a unique methodology to take advantage of the electrochemical characteristics of materials that are used in energy-harvesting devices. Particularly in triboelectric nanogenerator (TENG) studies, molecular grafting on dielectric metal oxide surfaces can be regarded as a feasible way to alter the surface charge density that directly affects the charge potential of triboelectric layers. Herein, we develop a feasible methodology to synthesize organic-inorganic hybrid structures with tunable triboelectric features. Different types of self-assembled monolayers (SAMs) with electron-donating and withdrawing groups have been used to modify metal oxide (MO) surfaces and to modify their charge density on the surface. All the synthetic routes for hybrid material production have been clearly shown and the formation of covalent bonds on the MO's surface has been confirmed by XPS. The obtained hybrid structures were applied as dopants to distinct polymer matrices with various ratios and fiberization processes were carried out to the prepare opposite triboelectric layers. The formation of the fibers was analyzed by SEM, while their surface morphology and physicochemical features have been measured by AFM and a drop shape analyzer. The triboelectric charge potential of each layer after doping and their contribution to the TENG device's parameters have been investigated. For each triboelectric layer, the best-performing tribopositive and tribonegative material combination was separately determined and then these opposite layers were used to fabricate TENG with the highest efficiency. A comparison of the device parameters with the reference indicated that the best tribopositive material gave rise to a 40% increase in the output voltage and produced 231 V, whereas the best tribonegative one led to a 33.3% rise in voltage and generated 220 V. In addition, the best device collected ~83% more charge than the reference device and came up with 250 V that corresponds to 51.5% performance enhancement. This approach paved the way by addressing the issue of how molecular engineering can be used to manipulate the triboelectric features of the same materials.

Hydrogen storage in depleted gas reservoirs using nitrogen cushion gas: A contact angle and surface tension study

The utilization of depleted natural gas reservoirs is a significant consideration for large-scale hydrogen (H2) storage and production. However, accurate knowledge of cushion gas compositions such as nitrogen (N2), methane (CH4), and carbon dioxide (CO2) is crucial, as they are critical components that affect the rock-fluid interfacial phenomenon, thereby impacting deployment feasibility. Moreover, there are limited reported studies on rock/brine/gas-mixture wettability and gas-mixture/brine surface tension for this type of reservoir. To address this gap, we explore the possibility of using N2 as a cushion gas (in the presence of CH4 and CO2) on a pristine quartz for H2 storage across various pressure (500–3000) psi, temperature (30–70) °C, and salinity (2–20) wt.%. We conducted extensive contact angle (CA) and surface tension (ST) experiments for different gas mixtures (H2–N2–CH4–CO2) to generate relevant data for H2 storage in depleted natural gas reservoirs using drop shape analyzer (DSA 100) equipment. Our findings suggest that the wettability behavior of the gas-mixture compositions studied is likely to remain consistent unless the rock's initial wetting state is altered. The CAs were observed to range between 28 and 46°, regardless of reservoir pressure, temperature, and salinity. It also increased with increasing pressure but decreased with increasing temperature. In addition, CA was lower at a lower N2 fraction (Mix 1–80% H2 – 10% N2 – 5% CH4 –5% CO2) compared to a higher N2 fraction (Mix 4–20% H2 – 70% N2 – 5% CH4 –5% CO2). The ST of the gas-mixture/brine systems declined with increasing (i) pressure, (ii) temperature, and (iii) N2 fraction but increased with increasing salinity for every gas mixture. Based on our investigation, mixtures 2 and 3 with H2 (40–60%) and N2 (30–50%) fractions (at constant 5% CH4 and 5% CO2) were identified as the optimal cushion gas for H2 storage and withdrawal under the studied conditions. The results of this study provide accurate and valuable input parameters and data for reservoir-scale simulations utilized in optimizing geo-storage in depleted natural gas reservoirs.

Identification of machine learning neural-network techniques for prediction of interfacial tension reduction by zein based colloidal particles

In this work, five different models of the artificial neural networks (ANNs) called feedforward, cascadeforward, timedelay, layrec and narx were used for IFT prediction as a function of biopolymers (zein and water-soluble portion of Zedo gum (WZG)) contents, pH, and time based on the experimental data. The architecture of the ANN models consisted of four inputs, one hidden layer and one output layer by considering the range of 1–60 neurons and the tansig activation function in the hidden layer. The experimental IFT data obtained from pendant drop method and drop shape analyzer (DSA) instrument were used to train the ANN models. The relative root mean square error (rRMSE) for the mentioned models were in the range of 0.68%− 2.51% and the overall score of timedelay model was higher than other models. Moreover, the relative importance index of the input data for more detailed assessment of IFT was determined for time delay model as the best model to predict IFT. Analysis showed that the impacts of time and zein content on IFT were greater than other factors. The results of this research showed the considerable ability of timedelay model (a data-based and knowledge-based combined approach) to predict IFT. This model can be used by food industry engineers as a very useful and cost-effective tool for process optimization and control the stability of emulsions.

Interfacial rheology insights: particle texture and Pickering foam stability

Interfacial rheology studies were conducted to establish a connection between the rheological characteristics of particle-laden interfaces and the stability of Pickering foams. The behavior of foams stabilized with fumed and spherical colloidal silica particles was investigated, focusing on foam properties such as bubble microstructure and liquid content. Compared to a sodium dodecyl sulfate-stabilized foam, Pickering foams exhibited a notable reduction in bubble coarsening. Drop shape tensiometry measurements on particle-coated interfaces indicated that the Gibbs stability criterion was satisfied for both particle types at various surface coverages, supporting the observed arrested bubble coarsening in particle-stabilized foams. However, although the overall foam height was similar for both particle types, foams stabilized with fumed silica particles demonstrated a higher resistance to liquid drainage. This difference was attributed to the higher yield strain of interfacial networks formed by fumed silica particles, as compared to those formed by spherical colloidal particles at similar surface pressures. Our findings highlight that while both particles can generate long-lasting foams, the resulting Pickering foams may exhibit variations in microstructure, liquid content, and resistance to destabilization mechanisms, stemming from the respective interfacial rheological properties in each case.

Liquid drops on compliant and non-compliant substrates: an ellipsoid-based fitting for approximating drop shape and volume

Liquid drops on compliant and non-compliant substrates: an ellipsoid-based fitting for approximating drop shape and volume

Impact of water on miscibility characteristics of the CO2/n-hexadecane system using the pendant drop shape analysis method

Miscible CO2 flooding has shown bright prospects for improving oil recovery from unconventional reservoirs as well as for storing greenhouse gas in underground formations. Although the favorable water presence effect has been reported in the near miscible CO2 flooding practices, there is still a lack of target research works on the impact of water on the miscibility characteristics of the oil/gas systems. Therefore in this paper, the effect of water presence on the Minimum Miscibility Pressure (MMP) of the CO2/n-Hexadecane (n-C16H34) system is experimentally investigated based on the Oil Droplet Volume Measurement (ODVM) method. By pre-saturating CO2 with water in the high-pressure high-temperature cell, the water component is introduced at the CO2/oil interface. Measurement results show the water presence could result in lower MMPs of the CO2/oil system. Under five temperature levels of 40 °C, 51 °C, 61 °C, 72 °C, and 82 °C, the water presence decreases the MMPs of the CO2/n-C16H34 system from 8.2 to 7.8 MPa, from 9.6 to 8.8 MPa, from 11.6 to 10.2 MPa, from 13.0 MPa to 12.2 MPa and from 14.6 MPa to 13.2 MPa respectively. Thermodynamic calculations provide consistent results as the experimental observations, indicating the main mechanism behind the lower MMPs of the water presence CO2/oil system could be the decreased CO2 molar fraction in the water presence system. This research is expected to provide an innovative viewpoint to understand the water presence effect in the CO2 flooding processes.

Dynamics of the spontaneously accelerative equatorial expansion of a droplet in a high-intensity acoustic standing wave field

This work reports an investigation of the acoustically induced accelerated deformation of drops in high-intensity acoustic standing wave fields generated by a single-axis acoustic levitator. The dynamic characteristics of droplet deformation are obtained and discussed based on high-speed visualization and in-house Python codes. Based on the actual physical characteristics, the finite element method numerical model has been developed for intercoupling the sound field and flow field, allowing for bidirectional feedback between the drop shape and the acoustic wave. The experimental results indicate that during the deformation process of droplets, their equatorial radius expands at an increasing speed without artificially increasing the sound field intensity. The simulation shows that the acoustic radiation suction acting on the equator dominates droplet deformation. Furthermore, there is a kind of positive feedback loop between the acoustic radiation pressure (pr) amplitude at the drop’s equator and the aspect ratio (AR) during the deformation period. It is confirmed that this causes the spontaneous accelerated expansion of the droplet’s equator. In addition, the functional relationship between pr at the drop’s equator and the AR has been obtained through theoretical derivation, which is consistent with the simulation results. Finally, the critical Bond number (Ba,s) of the rim instability is also obtained. This work provides deeper insights into contactless liquid manipulation and ultrasonic atomization technology applications.

A spectral boundary integral method for simulating electrohydrodynamic flows in viscous drops

A weakly conducting liquid droplet immersed in another leaky dielectric liquid can exhibit rich dynamical behaviors under the effect of an applied electric field. Depending on material properties and field strength, the nonlinear coupling of interfacial charge transport and fluid flow can trigger electrohydrodynamic instabilities that lead to shape deformations and complex dynamics. We present a spectral boundary integral method to simulate droplet electrohydrodynamics in a uniform electric field. All physical variables, such as drop shape and interfacial charge density, are represented using spherical harmonic expansions. In addition to its exponential accuracy, the spectral representation affords a nondissipative dealiasing method required for numerical stability. A comprehensive charge transport model, valid under a wide range of electric field strengths, accounts for charge relaxation, Ohmic conduction, and surface charge convection by the flow. A shape reparametrization technique enables the exploration of significant droplet deformation regimes. For low-viscosity drops, the convection by the flow drives steep interfacial charge gradients near the drop equator. This introduces numerical ringing artifacts that we treat via a weighted spherical harmonic expansion, resulting in solution convergence. The method and simulations are validated against experimental data and analytical predictions in the axisymmetric Taylor and Quincke electrorotation regimes.

Corrosion behavior of self-organized TiO2 nanotubular arrays grown on Ti6Al4V for biomedical applications

The electrochemical interactions between a biomaterial and a human fluid are important to understand when developing surfaces on titanium biomedical composites to improve bone regeneration, healing times, and longevity. Electrochemical corrosion is a major problem in implant-tissue interaction in that environment. The purpose of this research is to use different electrochemical methods such as open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) to examine the effect of self-organized TiO2 nanotubular surfaces on the corrosion resistance of Ti6Al4V surface. The electrochemical behavior of polished Ti6Al4V (control), and anodized samples at a constant voltage of 30V and various time-periods of anodization, such as 3hr, 4hr, and 5hrs respectively is the main focus of our study. All the anodized samples were annealed at 500 °C for 3hr with preheating rate of 5 °C per minute. The resistance of the nanotubular structure is improved after annealing because the anatase phase is stabilised, and the fluoride ions are removed. The electrochemical behavior of the nanotubular surfaces were investigated by using the simulated body fluid (SBF, 7.4 pH) solution. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and a Drop Shape Analyzer were all used to investigate the nanotubular morphology, chemical compositions, and structure. According to the findings, the anodic oxidation process results in a nanotubular structure that improves the surface area and influences the surface's chemical composition. Surfaces with self-organized TiO2 nanotubular structures had greater corrosion resistance than polished Ti6Al4V because the passive film had a larger surface area and a more dispersed amorphous crystal structure. Finally, the physical condition of the post-electrochemical treated sample was evaluated by the SEM images and compositional analysis by the EDS and XRD. The PDP curves showed the corrosion rate of the samples polished Ti6Al4V, TiO2 30V 3hr, TiO2 30V 4hr, and TiO2 30V 5hrs are 0.39, 0.35, 0.09, and 0.24 mm per year respectively. Similarly, the efficiencies of the anodized samples TiO2 30V 3hr, 4hr, and 5hrs are 9.96, 76.44, and 38.30% respectively. When comparing all of the anodized samples, the overall corrosion resistance is improved by 2 times.

Degradation profiling of in-vitro-produced polyhydroxyalkanoate synthesized by the soil bacterium Bacillus sp. PhNs9 under different microenvironments

Polyhydroxyalkanoates have been proven to be one of the best alternatives for synthetic plastics due to the similarity in their properties. The current study is focused on the natural degradation of the in vitro-produced PHA by the strain Bacillus sp. PhNs9. Different microenvironments were created to mimic different terrestrial and aqueous ecosystems. Maximum degradation of 98.62% was obtained in the soil while, in the case of aqueous systems, maximum degradation of 89.75% was found in the sewage wastewater in 30 days. The degradation profile of PHA was studied at different temperatures, pH, and moisture contents to ensure the degradation of produced PHA in different geographical locations having different environmental conditions. Different equations were obtained through a polynomial fitting for the prediction of degradation percentage at different conditions. The films were characterized using FTIR, Raman spectroscopy, drop shape analysis, and XRD which confirmed the decrease in both hydrophobicity and crystallinity of the films after degradation. This study established the natural degradation of the PHA produced by Bacillus sp. PhNs9 which could be commercialized without concerns about its accumulation in the environment.

An investigation on performance of castor oil and Pongamia oil based cutting fluid in MQL milling of aluminium alloy 6061

The expense of coolant in milling processes accounts for such a significant portion of overall production costs, research efforts are presently concentrated on finding ways to reduce or do away with the need for lubrication. The environment, the performance of the machining, and the prices of the machining can all benefit from the decrease or elimination of traditional fluid. By employing the Minimum Quantity Lubrication Method, one is able to cut down on lubrication costs while also lowering the potential danger to the health of workers. While end milling aluminium 6061 with a SINOMILL VMC300 and an HSS end mill tool at three distinct spindle speeds (1000, 1500, and 2000 rpm), three distinct doc(0.25, 0.5, and 0.75 mm), and three distinct feed(100,150,200 mm/min), surface roughness (Ra) was measured in dry milling, MQL with base fluid (Pongamia oil, castor oil), conditions. The reduction in Ra is reported as a 12.89% with base fluid (Pongamia oil), in comparison to dry milling. When compared to dry milling, the reduction in Ra that was recorded when using base fluid (castor oil) was 33.72%. In this experiment it was carried out by the Drop shape analyzer (which was manufactured by Kruss), it was found that the contact angle in castor oil is superior to the contact angle in pongamia oil, and the values of contact angle are 43.4 and 47.8 respectively.

Study of cutting force in turning of AISI- 304 steel using mono and hybrid graphene nanoparticles enriched cutting fluid

In manufacturing industries turning hard materials like AISI 304 steel is very challenging because of its low ability to heat dissipation. When these kinds of materials are perform machining, heat builds up on the tool tip, this raises the temperature of the tool tip which speeds up the rate of tool wear. So present investigation based on turning of hard material AISI-304 strain-free steel using Al-GrP based hybrid nanofluids and graphene-based nanofluids in vol. concentration 0.25, 0.5 & 0.75 vol% with the base oil sunflower oil. RSM with Box-Behnken was utilized in this experiment's design and response analysis. It was observed that the hybrid nanofluids made of Al-GrP (with nanoparticles fraction 80:20) and graphene had a reduced wettability, which affected the heat dissipation rate. This supports by the DSA test results of several nanofluids on tooltip surfaces. In Drop shape analyzer (DSA) results show that the contact angle at the tool insert in Al-GrP nanofluids is smaller than that of graphene-based nanofluids at the same concentration. During the experiment, it was discovered that Al-GrP and graphene have the shortest contact angles at 38.9° and 41.9° at 0.75 vol%.The use of (Al-GrP) hybrid nanofluids with MQL lowers surface finishing by 10%, as well as the force on cutting direction is 7.25 percent, respective compared to graphene-based nanofluids, and Graphene also demonstrates a high rate of tool wear, which forms a built-up edge on the tool during machining of AISI-304 strain-free steel.

Role of methane as a cushion gas for hydrogen storage in depleted gas reservoirs

Depleted natural gas reservoirs play an important role as a viable option for large-scale hydrogen storage and production. However, its deployment depends on the accurate knowledge of the cushion gas (such as CH4, CO2, and N2) compositions, which are key components affecting the rock-fluid interfacial phenomenon. In addition, there are currently few reported studies on rock/brine/gas-mixture wettability and gas-mixture/brine surface tension representing this type of reservoir. Hence, we report the feasibility of using CH4 as a cushion gas (in the presence of CO2 and N2) for H2 storage at various pressures (500 up to 3000 psi), temperatures (30 up to 70) oC, and salinities (2 up to 20) wt.% using drop shape analyzer equipment. Contact angle (CA) and surface tension (ST) experiments were extensively conducted for the different gas mixtures (H2–CH4–CO2–N2) to establish relevant data for H2 storage in depleted gas reservoirs.Our result indicates that unless when the rock's initial wetting state is altered, the studied gas-mixture compositions (Test case 1: 80% H2 – 10% CH4 – 5% CO2 – 5% N2; case 2: 70% H2 – 20% CH4 – 5% CO2 – 5% N2; case 3: 60% H2 – 30% CH4 – 5% CO2 – 5% N2; case 4: 50% H2 – 40% CH4 – 5% CO2 – 5% N2; case 5: 40% H2 – 50% CH4 – 5% CO2 – 5% N2; case 6: 30% H2 – 60% CH4 – 5% CO2 – 5% N2; and case 7: 20% H2 – 70% CH4 – 5% CO2 – 5% N2) will exhibit comparable wettability behavior as the CAs ranged between [20 to 41°] irrespective of the reservoir pressure, temperature, and salinity. ST decreases with increasing temperature and linearly with increasing pressure. ST for each gas mixture increased with salinity. ST decreases systematically with increasing CH4 fraction (at any given salinity, temperature, and pressure) with the highest observed in Test case 1 and the lowest in Test case 7 compositions. Test cases 3 and 4 with H2 (50–60%) and CH4 (30–40%) fractions was selected as the optimal gas mixture based on CA and ST for H2 storage and withdrawal. The study's findings offer precise and useful input data for the reservoir-scale simulation used in geo-storage optimization in depleted natural gas reservoirs.