Search Results (1,254)

Semi-open impeller sewage pumps are widely used for transporting solid-laden fluids due to their anti-clogging properties. However, unlike extensive research on clear water conditions, the specific mechanisms governing pressure instabilities under solid–liquid two-phase flows remain underexplored. This study investigates the unsteady flow field and pulsation characteristics of a Model 80WQ4QG pump using unsteady CFD simulations based on the Standard k−ϵ turbulence model and the Eulerian–Eulerian multiphase model. The effects of flow rate, particle size, and volume fraction were systematically analyzed. Results indicate that the blade-passing frequency (95 Hz) dominates the pressure spectra, with the volute tongue and impeller outlet identified as the most sensitive regions. While increased flow rates weaken fluctuations at the volute tongue, the presence of solid particles significantly amplifies them. Specifically, compared to single-phase flow, the pulsation amplitudes at the volute tongue increased by 68.15% with a 3.0 mm particle size and by 97.73% at a 20% volume fraction. Physically, this amplification is attributed to the intensified momentum exchange between phases and the enhanced turbulent flow disturbances induced by particle inertia at the rotor–stator interface. These findings clarify the particle-induced flow instability mechanisms, offering theoretical guidelines for optimizing pump durability in multiphase environments. Full article

Understanding the dynamic characteristics of droplets in the orientated flow channels of Proton Exchange Membrane Fuel Cells (PEMFCs) is crucial for their effective heat and water management and bipolar plate design. Therefore, the transient transport dynamics of liquid water within orientated gas flow channels (OGFCs) of PEMFCs are investigated, and a two-phase model based on the volume of fluid (VOF) method is established in the current study. Moreover, the impacts of the size of droplets and the geometrical parameters of baffles on the removal dynamics of liquid water are examined. The results show that baffles effectively promote droplet breakup and accelerate their detachment from the Gas Diffusion Layer (GDL) surface by increasing flow instability and local shear forces. The morphology of water is altered by the high velocity of gaseous flow, which can break up into several smaller droplets and distribute them on the surface of GDL by the gas flow. The shape of the liquid water film changes from a regular cuboid to a big droplet due to the surface tension of the liquid water droplets and the hydrophobicity of the GDL surfaces. Increasing the baffle height can reduce the time needed for the removal of droplets. With the increase in L1* from 0.25 to 0.75, the drainage time decreases slightly; however, for L1* increasing from 0.75 to 1.25, the drainage time remains almost the same. The impacts of different leeward lengths, L2*, on the water coverage ratio and pressure drop are minor. Full article

Needle-free injection (NFI) technology is a promising alternative to conventional syringe injection, as it mitigates needle-related complications and enhances patient compliance. However, achieving the controlled and efficient dispersion of larger-volume formulations (>1 mL) within tissues remains a significant challenge. This study presents a novel pneumatic NFI system that uses a two-phase driving mode to regulate driving pressure and duration with an ejection volume of 1.0–2.0 mL. The integrated pressure stabilization unit significantly reduces pressure fluctuations during the initial injection phase, generating a more stable and uniform spray distribution. It is designed to produce an ideal elliptical dispersion effect while eliminating splatter, enabling controlled large-volume delivery. Jet impact experiments were conducted to investigate the dynamic characteristics of microjets generated by conventional single-phase and novel two-phase driving modes. Furthermore, the influence of the driving mode on the dispersion behaviors of microjets in agarose gels was explored through high-speed imaging of gel injections. The results demonstrate that the two-phase driving mode produces a distinct two-phase jet pressure profile. Compared to the single-phase mode, the two-phase mode produced a significantly larger dispersion width at equivalent initial driving pressures. This promotes more uniform lateral drug distribution and achieves a higher percentage of liquid drug delivery in gels. Furthermore, favorable driving pressure combinations were identified for different volumes: (1.25–0.25) MPa for 1.0 mL, (1.25–0.50) MPa for 1.5 mL, and (1.50–0.50) MPa for 2.0 mL. This provides a practical basis for optimizing clinical parameters and advancing the development of controllable NFI systems. Full article

Cholesterol plays a fundamental role in the human body—it stabilizes cell membranes, modulates gene expression, and is a precursor to steroid hormones, vitamin D, and bile salts. Its correct level is crucial for homeostasis, while both excess and deficiency are associated with serious metabolic and health consequences. Excessive accumulation of cholesterol leads to the development of atherosclerosis, while its deficiency disrupts the transport of fat-soluble vitamins. Magnetic resonance spectroscopy (MRS) enables the detection of cholesterol esters and the differentiation between their liquid and crystalline phases, but the technical limitations of clinical MRI systems require the use of dedicated coils and sequence modifications. This study demonstrates the feasibility of using MRS to identify cholesterol-specific spectral signatures in atherosclerotic plaque through ex vivo analysis. Using a custom-designed experimental coil adapted for small-volume samples, we successfully detected characteristic cholesterol peaks from plaque material dissolved in chloroform, with spectral signatures corresponding to established NMR databases. To further enhance spectral quality, a deep-learning denoising framework based on a 1D U-Net architecture was implemented, enabling the recovery of low-intensity cholesterol peaks that would otherwise be obscured by noise. The trained U-Net was applied to experimental MRS data from atherosclerotic plaques, where it significantly outperformed traditional denoising methods (Gaussian, Savitzky–Golay, wavelet, median) across six quantitative metrics (SNR, PSNR, SSIM, RMSE, MAE, correlation), enhancing low-amplitude cholesteryl ester detection. This approach substantially improved signal clarity and the interpretability of cholesterol-related resonances, supporting more accurate downstream spectral assessment. The integration of MRS with NMR-based lipidomic analysis, which allows the identification of lipid signatures associated with plaque progression and destabilization, is becoming increasingly important. At the same time, the development of high-resolution techniques such as μOCT provides evidence for the presence of cholesterol crystals and their potential involvement in the destabilization of atherosclerotic lesions. In summary, nanotechnology-assisted MRI has the potential to become an advanced tool in the proof-of-concept of atherosclerosis, enabling not only the identification of cholesterol and its derivatives, but also the monitoring of treatment efficacy. However, further clinical studies are necessary to confirm the practical usefulness of these solutions and their prognostic value in assessing cardiovascular risk. Full article

Ions in liquid helium exist in their simplest form in two configurations, as negatively charged “electron bubbles” (electrons in a void of about 35 Å in diameter) and as positive “snowballs” (He⁺ ions surrounded by a sphere of solid helium, about 14 Å in diameter). Here, we give an overview of studies with these ions when they are trapped at interfaces between different helium phases, i.e., the “free” surface between liquid and vapor, but also the interfaces between liquid and solid helium at high pressure and between phase-separated ³He-⁴He mixtures below the tricritical point. Three cases are discussed: (i) if the energy barrier provided by the interface is of the order of the thermal energy k_BT, the ions can pass from one phase to the other with characteristic trapping times at the interface, which are in qualitative agreement with the existing theories; (ii) if the energy barrier is sufficiently high, the ions are trapped at the interface for extended periods of time, forming 2D Coulomb systems with intriguing properties; and (iii) at high electric fields and high ion densities, an electrohydrodynamic instability takes place, which is a model for critical phenomena. Full article

In Proton Exchange Membrane Water Electrolysis (PEMWE), the two-phase flow distribution in the anode field significantly affects overall electrolysis performance. Based on visualized experimental data, in this paper, the reaction kinetics equations were theoretically revised, and a three-dimensional, two-phase, non-isothermal, multi-physics coupled model of the electrolysis was developed and experimentally validated. Four different configurations of rectangular turbulence promoters were designed within the anode serpentine flow field and compared with a conventional serpentine flow field (SFF) in terms of their multi-physics distribution characteristics. The results showed that, in the double-row rectangular block serpentine flow field (DRB SFF), the uniformity of liquid water saturation, temperature, and current density improved by 16.6%, 0.49% and 40.8%, respectively. The normal mass transfer coefficient increased by a factor of 6.3, and polarization performance improved by 6.98%. A cross-arranged turbulence promoter structure was further proposed. This design maintains effective turbulence while reducing flow resistance and pressure drop, thereby enhancing mass transfer efficiency and overall electrolysis performance through improved bubble fragmentation. Full article

To investigate the influence of particle characteristics on wear in slurry pump flow-through components, this study established a computational fluid dynamics-discrete element method (CFD-DEM) coupled with the Archard wear model for numerical simulation of solid-liquid two-phase flow characteristics and wear mechanisms within the pump. Focusing on the correlation between wear contour distribution and particle collision frequency, the study systematically analyzed the influence mechanisms of particle concentration, size distribution, and shape on wear patterns within the pump. The reliability of the coupled model was validated through external characteristic tests. Results indicate that wear severity on both the impeller and volute increases significantly with rising particle concentration, while wall particle collision frequency exhibits a positive correlation with concentration. Particles of 1.5 mm diameter cause the most severe localized wear on the impeller, whereas the presence of mixed particles partially mitigates the wear effect of larger particles. Both total and localized wear on the volute peak at a particle diameter of 1 mm. Low-sphericity particles intensified overall wear on both the impeller and volute; while high-sphericity particles reduced overall wear, they induced more severe localized wear on the impeller. Volute localized wear was most pronounced at a sphericity of 0.84. This study elucidates the mechanism by which particle characteristics influence wear on slurry pump flow-through components, providing a theoretical basis for optimizing slurry pump design. Full article

The chemical composition, mineral composition, and mineral distribution characteristics of steel slag were characterized through petrographic analysis, X-ray diffraction (XRD), and particle size analysis. Limestone, silica, and silicomanganese slag were blended with converter steel slag to fabricate a reconstructed steel slag. Through burden calculation, the chemical composition ratio of this reconstructed steel slag approximated the silicate phase region. The high-temperature reconstruction process outside the furnace was simulated through reheating. The composition, structure, and cementitious characteristics of the reconstructed steel slag were investigated through X-ray diffraction (XRD), FactSage software (FactSage version 7.0 (GTT-Technologies, Aachen, Germany, 2015))analysis, scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) analysis, setting time determination, compressive strength measurement, and thermodynamic computation. The findings indicated that the primary mineral compositions of the reconstructed steel slag were predominantly silicates, such as Ca₃Al₂O₆, Ca₂SiO₄, Ca₂MgSi₂O₇, Ca₂Al(AlSiO₇), Ca₂(SiO₄), and FeAlMgO₄. In comparison with the original steel slag, these compositions underwent substantial alterations. The α′-C₂S phase appears at 1100 K and gradually transforms into α-C₂S at 1650 K. The liquid phase begins to precipitate at approximately 1550 K. Spinel exists in the temperature range from 1300 to 1700 K, and Ca₃MgSi₂O₈ melts into the liquid phase at 1400 K. As the temperature increases to 1600 K, the minerals C₂AF, Ca₂Fe₂O₅, and Ca₂Al₂O₅ gradually melt into the liquid phase. Melilite melts into the liquid phase at 1700 K. It was observed that the initial and final setting times of the reconstructed steel slag exhibited reductions of 7 and 43 min, respectively, in comparison to those of the original steel slag. In comparison with steel slag, the compressive strength of the reconstructed steel slag exhibited an increase of 0.6 MPa at the 3-day strength stage, 1.6 MPa at the 7-day strength stage, and 3.4 MPa at the 28-day strength stage. The reduction in setting time and the enhancement in compressive strength verified the improved cementitious activity of the reconstructed steel slag. Thermodynamic calculations of the principal reactions of the reconstructed steel slag at elevated temperatures verified that the primary reaction at 1748 K is thermodynamically favorable. Full article

Modern processes to produce rare-earth elements, strategic metals, and nuclear fuel reprocessing require highly efficient liquid–liquid extraction in systems characterized by high viscosity, elevated interfacial tension, and small density differences. Traditional gravity-driven extractors exhibit low performance under these conditions, whereas centrifugal extractors enable rapid mass transfer and nearly complete phase separation. Differential-contact annular centrifugal contactors offer the highest flexibility and efficiency, but their optimization is limited by the lack of experimental data on the hydrodynamics of liquid flow through perforated nozzles in a rotating field. This limitation hinders the development of accurate computational fluid dynamics (CFD) models (e.g., ANSYS Fluent), reliable equipment scale-up, and the design of optimized contactor configurations. The present study addresses this gap by experimentally determining the flow velocity of liquids through nozzles of various geometries across a wide range of centrifugal accelerations. From these data, a universal power-law correlation was derived, linking the flow rate to rotor speed, nozzle geometry, and the physicochemical properties of the phases. The proposed correlation provides a robust experimental basis for numerical model validation, computational design, and optimization of next-generation differential-contact centrifugal extractors. Full article

When considering the adsorption effect, traditional experimental methods have faced significant challenges in obtaining the solute transport parameters for composite pollutants. Based on the adsorption test data of three types of composite pollutants collected from the Web of Science and China National Knowledge Infrastructure databases from 2014 to 2024, this study employed four commonly used machine learning models, that is, Random Forest (RF), Support Vector Machine (SVM), Back Propagation Neural Network (BPNN), and Decision Tree (DT) models, to establish adsorption isotherms of pollutants with liquid-phase equilibrium concentration as the horizontal coordinate and solid-phase adsorption capacity as the vertical coordinate, and systematically investigated the adsorption characteristics of combined pollutants in the porous aquifer. Subsequently, the Mean Square Errors (MSEs) and coefficients of determination, two commonly used evaluation metrics for regression models in machine learning, were chosen to estimate the prediction effect of datasets. Combined with the convection–diffusion equation, the adsorption kinetic parameters under the mutual interference of composite pollutants, namely, the retardation factor, were solved. The results show that for the adsorption isotherms of heavy metal composite pollutants, organic composite pollutants, and heavy metal and organic combined composite pollutants, SVM, BPNN, and RF models have the best prediction effect, respectively, and their MSEs are 0.032, 0.001, and 0.018. The adsorption isotherm fitting results indicate that the heavy metal composite pollutants and organic composite pollutants conform to the Freundlich model. The retardation factor of organic composite pollutants is significantly higher than that of heavy metal composite pollutants. Full article

Methanol is a liquid fuel with high oxygen content and the potential for a closed-loop carbon-neutral production cycle. To investigate the mixture formation and combustion characteristics of a heavy-duty Port Fuel Injection (PFI) methanol engine, a three-dimensional numerical simulation model was established using the CONVERGE 3.0 software. Multi-cycle simulations were performed to analyze the influence of wall film dynamics on engine performance. The results indicate that the “adhesion–evaporation” equilibrium of the intake port wall film determines the in-cylinder mixture concentration. Due to the high latent heat of vaporization of methanol, severe wall-wetting occurs during the initial cycles, causing the actual fuel intake to lag behind the injection and leading to an overly lean mixture and misfire. Regarding injection strategies, the open valve injection (OVI) strategy utilizes high-speed intake airflow to reduce wall adhesion and improve fuel transport efficiency compared to closed valve injection. OVI refers to the fuel injection strategy that injects fuel into the intake port during the intake valve opening phase. The open valve injection strategy (e.g., SOI −500° CA) demonstrates distinct superiority over closed valve strategies (SOI −200°/−100° CA), achieving a 75% reduction in wall film mass. The long injection duration and early phasing allow the high-speed intake airflow to carry fuel directly into the cylinder, significantly minimizing wall film accumulation and avoiding the “fuel starvation” observed in closed-valve strategies. Additionally, OVI fully utilizes methanol’s latent heat to generate an intake cooling effect, which lowers the in-cylinder temperature and helps suppress knock. Furthermore, a dual-injector strategy is proposed to balance spatial atomization and rapid fuel transport, which achieves a 66.7% increase in the fuel amount entering the cylinder compared with the original strategy. This configuration effectively resolves the fuel induction lag, achieving stable combustion starting from the first cycle. Full article

During natural gas field extraction, downhole compressors frequently encounter gas-liquid two-phase flow conditions, yet the internal flow characteristics and performance evolution mechanisms remain insufficiently understood. This paper investigates a small-scale, low-pressure-ratio five-stage axial compressor using a multiphase numerical simulation method based on the Euler-Lagrange framework. The study systematically examines the effects of different inlet pressures (0.1 MPa, 1 MPa, 8 MPa) and liquid mass fraction (0%, 5%, 10%) on its overall and stage-by-stage performance, droplet evolution, and flow field structure. The results indicate that the inlet pressure exerts a decisive influence on the overall efficiency trend of wet compression. The stage efficiency response displays a trend of an initial decrease in the front stages followed by an increase in the rear stages, showing significant variation under different inlet pressures. Flow field analysis reveals that increased inlet pressure intensifies droplet aerodynamic breakup, leading to higher flow losses in the compressor. Simultaneously, under high-pressure conditions, the cumulative cooling effect resulting from droplet heat transfer and evaporation effectively enhances the flow stability in the rear stages. This research elucidates the interstage interaction mechanisms of gas-liquid two-phase flow in low-pressure-ratio multistage compressors and highlights the competing influences of droplet breakup and evaporation effects on performance under different pressure conditions, providing a theoretical basis for the optimal design of downhole wet gas compression technology. Full article

As the power density of microelectronic devices and components continues to increase, thermal management has become a critical bottleneck limiting their performance and reliability. With its advantages of effective heat dissipation, no need for external power, and good safety, the micro pulsating heat pipe (MPHP) exhibits unique application advantages and enormous development potential when compared to other cutting-edge thermal management solutions, such as embedded microchannel cooling technology, which has complicated manufacturing processes and is prone to leakage, or thermoelectric material cooling technology, which is limited by material efficiency and self-heating. However, a pulsating heat pipe (PHP) is vulnerable to the combined impacts of several elements (scale effects, wall effects, and interfacial effects) at the micro-scale, which can lead to highly variable heat transfer characteristics and complex two-phase flow behavior. There are still few thorough experimental reviews on this subject, despite the fact that many researchers have concentrated on the MPHP and carried out in-depth experimental investigations on their flow and heat transmission mechanisms. In order to provide strong theoretical support for optimizing the design of the MPHP cooling devices, this paper reviews previous experimental research on the MPHP with the goal of thoroughly clarifying the mechanisms of gas–liquid two-phase flow and heat/mass transfer within them. The definition of MPHP is first explained, along with its internal energy transmission principles and structural features. The motion states of gas–liquid two-phase working fluids in the MPHP from previous experimental investigations are then thoroughly examined, highlighting their distinctive flow patterns and evolution mechanisms. Lastly, the variations in thermal performance between different kinds of MPHPs are examined, along with the factors that affect them. Full article

Semi-open impeller sewage pumps are widely used in fields such as municipal wastewater treatment. However, they often face performance degradation and operational instability when conveying solid–liquid two-phase flows containing solid particles. This study aims to systematically elucidate the influence mechanisms of particle diameter (0.5–3.0 mm) and volume fraction (1–20%) on the external characteristics and internal flow field of semi-open impeller sewage pumps, providing a theoretical basis for optimizing their design and operational stability. Using an 80WQ4QG-type sewage pump as the research subject, this study employed a combination of numerical simulation and experimental research. The standard k-ε turbulence model coupled with the Discrete Phase (Particle) approach was adopted for multi-condition solid–liquid two-phase flow simulations. Furthermore, two-way analysis of variance (two-way ANOVA) was utilized to quantify the main effects and interaction effects of the parameters. The results indicate that the pump head and efficiency generally exhibit a decreasing trend with increasing particle diameter or volume fraction, with particle diameter exerting a more pronounced effect (p < 0.01). When the particle diameter increased to 3.0 mm, the head decreased by 5.66%; when the volume fraction rose to 20%, the head decreased by 4.17%. It is noteworthy that the combination of a 0.5 mm particle diameter and a 20% volume fraction resulted in an abnormal increase in head, suggesting a possible flow pattern optimization under specific conditions. Analysis of the internal flow field reveals that coarse particles (≥1.5 mm) intensify the pressure gradient disparity between the front and rear shroud cavities of the impeller, thereby increasing the axial thrust. A high volume fraction (≥10%) promotes pronounced flow separation in the volute tongue region and exacerbates the risk of localized erosion at the outlet. Full article

Hydrothermal liquefaction (HTL) is a thermochemical process by which biomass feedstocks are converted into bio-oil and multiple by-products, including aqueous co-product (ACP), gaseous co-product (GCP), and biochar. Bio-oil produced from food waste feedstocks represents a potential candidate for use in commercial waste-to-energy conversions. The objective of this study is to further develop this technology by investigating the product distribution and quality from the HTL of food waste feedstocks. Four food waste feedstocks were selected for analysis: brewery grains, pear lees, coffee grounds, and honeydew skins. Solids analysis was conducted on each as-received feedstock, with the results determining dilution ratios for optimizing water content for HTL (≥80%). HTL conversions were conducted at 300 °C with a retention time of 30 min. Biochar was measured after product filtration, while ACP and bio-oil were measured via liquid–liquid phase separation. Coffee grounds produced the highest percentage of bio-oil (0.460%) and biochar (9.96%), while pear lees produced the highest percentage of ACP (89.5%). After quantification, ACP was characterized for nutrient concentrations. The quality of the ACP differed significantly from values in the literature, highlighting the influence of feedstock type and reaction conditions on HTL product characteristics (in addition to distribution) and underscoring the need for further research to optimize co-product utilization and process efficiency. Full article