Multi Structure Research Articles

Preparation of superhydrophobic conductive micro/nano‐graphite/PDMS films on paper by simple spraying method

AbstractPaper‐based materials are widely used in various fields due to their advantages, such as environmental friendliness and sustainability. However, the highly hydrophilic nature of the cellulose that makes up paper‐based materials limits their use. In this paper, micron/nano‐graphite/polydimethylsiloxane (PDMS) coatings with excellent superhydrophobic and conductive properties were prepared on the surface of filter paper by a simple spraying method. A mixture of micro‐graphite and nano‐graphite was used to form a multistage rough structure on the surface of the filter paper by spraying, and the low surface energy PDMS enhanced the adhesion of the micro‐graphite and nano‐graphite on the surface of the filter paper. The results showed that the samples possessed the best superhydrophobic properties when the ratio of micro‐graphite to nano‐graphite was 1:1, at which time the contact and rolling angles of the samples were 165.4° and 3.2°, respectively. The prepared superhydrophobic samples have good bounce and self‐cleaning properties, while the samples have good mechanical stability and chemical resistance. Additionally, due to the conductivity of micro–nano‐graphite, both particle sizes closely contact the sample surface, creating a conductive network. With a 1:1 ratio of micro‐ and nano‐graphite, the coating exhibits minimal resistance at 1.89 KΩ, and the sample maintains stable conductivity even underwater. The above properties greatly extend the application range of paper‐based superhydrophobic materials.

Deep learning-based immunohistochemical estimation of breast cancer via ultrasound image applications.

Breast cancer is the key global menace to women's health, which ranks first by mortality rate. The rate reduction and early diagnostics of breast cancer are the mainstream of medical research. Immunohistochemical examination is the most important link in the process of breast cancer treatment, and its results directly affect physicians' decision-making on follow-up medical treatment. This study aims to develop a computer-aided diagnosis (CAD) method based on deep learning to classify breast ultrasound (BUS) images according to immunohistochemical results. A new depth learning framework guided by BUS image data analysis was proposed for the classification of breast cancer nodes in BUS images. The proposed CAD classification network mainly comprised three innovation points. First, a multilevel feature distillation network (MFD-Net) based on CNN, which could extract feature layers of different scales, was designed. Then, the image features extracted at different depths were fused to achieve multilevel feature distillation using depth separable convolution and reverse depth separable convolution to increase convolution depths. Finally, a new attention module containing two independent submodules, the channel attention module (CAM) and the spatial attention module (SAM), was introduced to improve the model classification ability in channel and space. A total of 500 axial BUS images were retrieved from 294 patients who underwent BUS examination, and these images were detected and cropped, resulting in breast cancer node BUS image datasets, which were classified according to immunohistochemical findings, and the datasets were randomly subdivided into a training set (70%) and a test set (30%) in the classification process, with the results of the four immune indices output simultaneously from training and testing, in the model comparison experiment. Taking ER immune indicators as an example, the proposed model achieved a precision of 0.8933, a recall of 0.7563, an F1 score of 0.8191, and an accuracy of 0.8386, significantly outperforming the other models. The results of the designed ablation experiment also showed that the proposed multistage characteristic distillation structure and attention module were key in improving the accuracy rate. The extensive experiments verify the high efficiency of the proposed method. It is considered the first classification of breast cancer by immunohistochemical results in breast cancer image processing, and it provides an effective aid for postoperative breast cancer treatment, greatly reduces the difficulty of diagnosis for doctors, and improves work efficiency.

Multistage bridge engineering for electrolyte and interface enables quasi-solid batteries to operate at -40°C

The practical application of solid-state batteries (SSBs) has been significantly hampered by the sluggish Li+ transport dynamics in cold climates. In particular, SSBs suffer from insufficient dynamics due to poor electrolyte-electrode interface compatibility at low temperatures. Herein, a multistage bridge engineering for electrolyte and interface is proposed to improve the Li+ transfer kinetics, which enables quasi-solid batteries to operate at low temperatures. The incorporation of siloxane segments allows the electrolyte to polymerise uniformly and improves Li+ transport. The multistage bridging structure improves the electrode-electrolyte interfacial interaction, accelerating Li+ transfer kinetics at low temperatures. The obtained Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) cell delivers a high coulombic efficiency of 99.98 % and a specific energy of 266 Wh⋅kg−1 at -40 °C. This multistage bridge engineering strategy provides a new perspective for polymer electrolyte design towards stable operation of quasi-solid batteries at low temperatures.

An iontronic flexible pressure sensor based on a multistage gradient micro-dome structure with a broad sensing range for wearable devices

The sensing principles, performance, and applications of the iontronic sensor in posture assessment in this work.

Engineering Co3O4@3DOM LaCoO3 multistage-pore nanoreactor with superior SO2 resistance for toluene catalytic combustion.

Sulfur dioxide poisoning is a significant factor in catalyst deactivation during the catalytic combustion of volatile organic compounds. In this study, we prepared the LaCoO3 and Co3O4 composite catalysts using both the Ship-in-Bottle and Building-Bottle-Around-Ship approaches. Three-dimensionally ordered macropores (3DOM LaCoO3) were utilized as nanoreactors to protect the active sites during the catalytic combustion of toluene, preventing SO2 poisoning. Additionally, we grew ZIF-67 confined in the nanoreactor to create a multistage-pore structure. The Co3O4@3DOM LaCoO3 catalysts exhibited excellent activity in the complete catalytic oxidation of toluene. Various characterization studies confirmed the presence of a significant number of Co3+ species and an abundance of surface weak acid sites in the Co3O4@3DOM LaCoO3 catalysts, which synergistically enhanced the conversion of VOCs at low temperatures. Notably, the multistage pore structure provided a favorable reaction environment, accelerating the adsorption and diffusion of toluene and intermediates, resulting in excellent sulfur resistance of the catalysts. Moreover, XPS analysis confirmed a strong interaction between Co3O4 and LaCoO3, promoting rapid electron transfer and increasing the activation of O2-. In situ DRIFTS experiments verified that toluene mainly follows the MvK mechanism over Co3O4@3DOM LaCoO3 catalysts, indicating the following reaction pathway: toluene adsorption → benzyl alcohol → benzaldehyde → benzoate → anhydride → CO2 and H2O.

Experimental study of the effects of a multistage pore-throat structure on the seepage characteristics of sandstones in the Beibuwan Basin: Insights into the flooding mode

To investigate the relationship between grain sizes, seepage capacity, and oil-displacement efficiency in the Liushagang Formation of the Beibuwan Basin, this study identifies the multistage pore-throat structure as a crucial factor through a comparison of oil displacement in microscopic pore-throat experiments. The two-phase flow evaluation method based on the Li–Horne model is utilized to effectively characterize and quantify the seepage characteristics of different reservoirs, closely relating them to the distribution of microscopic pores and throats. It is observed that conglomerate sandstones at different stages exhibit significant heterogeneity and noticeable differences in seepage capacity, highlighting the crucial role played by certain large pore throats in determining seepage capacity and oil displacement efficiency. Furthermore, it was found that the displacement effects of conglomeratic sandstones with strong heterogeneity were inferior to those of conventional homogeneous sandstone, as evidenced by multiple displacement experiments conducted on core samples with varying granularities and flooding systems. Subsequently, core-based experiments on associated gas flooding after water flooding were conducted to address the challenge of achieving satisfactory results in a single displacement mode for reservoirs with significant heterogeneity. The results indicate that the oil recovery rates for associated gas flooding after water flooding increased by 7.3%–16.4% compared with water flooding alone at a gas–oil ratio of approximately 7000 m3/m3. Therefore, considering the advantages of gas flooding in terms of seepage capacity, oil exchange ratio, and the potential for two-phase production, gas flooding is recommended as an energy supplement mode for homogeneous reservoirs in the presence of sufficient gas source and appropriate tectonic angle. On the other hand, associated gas flooding after water flooding is suggested to achieve a more favorable development effect compared to a single mode of energy supplementation for strongly heterogeneous sandstone reservoirs.

Anti-icing system based on multi-level micro-nano and electric heating dual structure

The potential application value of superhydrophobic surfaces with anti-icing and de-icing properties in aerospace, telecommunications cables, energy and other fields has always been an important research topic. In this paper, a kind of superhydrophobic surface with stable structure, sufficient heat, excellent heat transfer performance and mass production was prepared based on elastic material. In this study, the multi-stage micro-nano rough structure is synthesized by ingenious pressing and mold closing control, and the surface contact angle of the prepared sample can reach 159°. The multi-stage micro-nano rough structure on the surface of the experimental sample can make the water droplets form a large number of cavitation, which can delay the icing of static water droplets. The height difference on both sides of (Un)pressed mesh surface makes the water droplets freeze asymmetrically, so (Un)pressed mesh surface has excellent anti-icing ability. The experimental sample is connected with 24 V direct current, and the average resistivity is 1.403 Ω·cm. The temperature can be raised to about 60 °C in one minute. The prepared sample has stable temperature, good electrical conductivity, sufficient heat generation, excellent heat transfer performance and high anti-icing efficiency. This study expands the design idea of anti-icing of aircraft rotor.

Facile preparation of durable superhydrophobic coating with microstructure self-repairing function by spraying method

Self-healing superhydrophobic coatings have attracted tremendous attention recently, although their practical applications are severely limited by hydrophobic instability and poor structure durability. In this study, a durable superhydrophobic coating was fabricated by a rapid micro/nano structural reconstruction strategy. Carbon nanofibers (CNF) with high aspect ratio were interspersed in fluorosilicone resin (FSR) to construct a uniform network structure. By combining with temperature-responsive carnauba wax (CW) and modified fluororubber (MFR), we obtained a superhydrophobic FSR/CNF/CW/MFR coating with a water contact angle (WCA) of 157 ± 1.2° and water sliding angle (WSA) of 4.5 ± 0.4°. Under the triple synergy of polymer segment migration of FSR, temperature-responsive phase transition of CW, and elastomer rebound repair of MFR, the damaged FSR/CNF/CW/MFR coating surface was rapidly reformed to a new hierarchical micro/nanostructure with short heat treatment (less than 120 s). As a result, for a flat surface, after 1000 abrasion cycles or falling ball impact, a rich micro/nano structure was rapidly reconstructed and superhydrophobic properties were restored. The reconstructed micro/nano multistage structure could effectively capture air, which led to the repaired area exhibiting a charming silver mirror effect and excellent self-cleaning performance. Therefore, this work is expected to provide new insight into the restoration of micro/nanostructures of durable superhydrophobic coatings.

Plastic wastes-derived electro-spun nanofiber/MnO2 nanocomposite for flexible supercapacitor application

The usage of plastic bottles in large quantities will cause serious pollution to the environment due to its poor biodegradability. The recycling of plastic waste with high added value for expanded applications needs to be explored and the poor mechanical properties should be resolved at the meantime. Herein, plastic waste was recycled into flexible nanofiber electrode based on electrospinning associated with acidified carbon nanotubes loaded inside/outside and electrodeposition of nano-MnO2 film outside. The fabricated plastic waste-based composites could be directly used as a supportable electrode with high conductivity, multistage aperture structure and efficient pseudo-capacitance. And the further assembled symmetric supercapacitors exhibited excellent flexibility, high energy capacity as the specific capacitance of 118.8 mF/cm2 at a scan rate of 10 mV/s and desirable cycle stability as 97.6 % capacitance retention over 5000 charge/discharge cycles. The strategies presented herein help alleviate the white pollution problem and realize the recycling and utilization of waste plastic products with high added value, which is a cost-effective and sustainable option to promote circular economy.

Development of sulfhydryl grafted hierarchical porous geopolymer for highly effective removal of Pb (II) from water

Geopolymers have captured increasing attention in the adsorption of lead ions due to their zeolite-like three-dimensional network structure, and several advantages such as low cost and environmental friendliness. However, their adsorption performance is limited by a small specific surface area and fewer adsorption sites. In this study, a metakaolin-based geopolymer was first pretreated with different concentrations of nitric acid to increase the porosity and surface area. Subsequently, the sulfhydryl functional group was grafted onto the above hierarchical porous geopolymer, which is a inorganic material with multistage pore structure. The result of N2 adsorption and desorption results demonstrated that an increase in specific surface area and number of grafting sites for sulfhydryl groups with increasing acid concentration when the highest nitric acid concentration used is 5 mol/L and acid treatment time is for 5 h. The specific surface area of the fabricated geopolymers was as high as 343.87 m2/g and the concentration of silanol groups reached 4.46 mmol/g at 3 mol/L acid concentration. The maximum Pb2+ adsorption quantities for SH-1HGeo, SH-2HGeo, and SH-3HGeo samples were 173.2 mg/g, 239.8 mg/g, and 386.3 mg/g, respectively. The adsorption processes were in accordance with the pseudo-second-order kinetic model and the Langmuir models, indicating that the Pb2+ adsorption on the sulfhydryl grafted hierarchical porous geopolymer was mainly chemisorption and monolayer adsorption. The contribution of different Pb2+ adsorption mechanism on geopolymer was ion-exchange, while that on SH-3HGeo was functional group complexation.

High-strength ionic hydrogel constructed by metal-free physical crosslinking strategy for enhanced uranium extraction from seawater

Uranium is one of the most important elements in the nuclear industry, and efficient extraction of uranium from the ocean is conducive to the sustainable development of nuclear energy. In this work, rigid perylene tetracarboxylate anion (PTC4−) was introduced by physical (non-covalent) crosslinking strategy to obtain metal-free ionic hydrogel PAOIB-PTC. PTC4− not only increased the rigid structure content of ionic hydrogel, but also formed dynamic macrocycle AO-PTC with amidoxime (AO) through hydrogen bonds. Unlike reported heterogeneous additives, PTC4− did not undergo inhomogeneity or shedding. Therefore, PAOIB-PTC exhibited high strength (7.34 MPa), excellent solvent resistance and salinity tolerance. A large number of hydrophilic groups and multistage pore structure endowed PAOIB-PTC with high hydrophilicity, which facilitated U(VI) mass transfer and led to rapid adsorption rates (88.6 mg g−1 h−1, c0 = 250 ppm). Since the metal-free component enabled more adsorption sites to be utilized, the maximum adsorption capacity of PAOIB-PTC was as high as 1008.03 mg g−1, which exceeded most reported hydrogel-based uranium adsorbents. Experiments and DFT calculations proved that PAOIB-PTC possessed high adsorption selectivity through uranyl recognition via hydrogen bonding and synergistic coordination by supramolecular structure AO-PTC. The low-concentration uranium capture capability and excellent recycling performance demonstrated the practical application potential of PAOIB-PTC. This work provides an idea for the design of metal-free ionic hydrogels with high-strength, and the established PAOIB-PTC is expected to be a candidate material for enhanced uranium extraction from seawater.

HKUST-1 derived one-dimensional Cu/N-doped carbon nanofibers for simultaneous detection of acetaminophen and sulfanilamide

The design of novel signal amplification elements was key to improving the sensing and analysis performance of electrochemical sensors. In this work, porous one-dimensional copper nitrogen-doped carbon nanofibers (Cu-NCNFs) were successfully prepared via the coupled process of electrospinning technology and high-temperature pyrolysis. This coupling of multiple processes and the introduction of heteroatoms pyrolyzed the HKUST-1 particles to generate three-dimensional Cu-doped carbon octahedra and mosaic them inside the one-dimensional carbon nitride channels, obtaining small-sized Cu particles while introducing a large number of N species, and constructing a three-dimensional MOFs-derived metal-carbon hybrid one-dimensional multistage carbon nitride structure. The resulting Cu-NCNFs sensor could simultaneously determine acetaminophen and sulfanilamide and exhibit superior electroanalytical performance, reproducibility, stability, and selectivity. This strategy provides a new approach to preparing novel signal amplification elements for the efficient monitoring of micropollutants.

Evolution of mechanical and corrosion properties of TiN/TiO2 nanocomposite multi-stage coating on AZ31 magnesium alloy using atomic layer deposition and in-situ oxidation

TiN/TiO2 nanocomposite film has been deposited on AZ31 magnesium alloy by two-step preparation involving atomic layer deposition and in-situ oxidation. The compact single and multi-stage coatings uniformly cover the surface. Mechanical property evaluation indicates that the resulting coating has good adhesion strength, well wear resistance and compressive residual stress. Furthermore, neutral salt spray test shows a uniform corrosion mode. Hydrogen evolution and electrochemical tests indicate excellent corrosion resistance. For example, compared to AZ31 magnesium alloy, the hydrogen evolution rate of the two-stage sample decreases by a farceur to 1/2, and corrosion current density drops by a farceur to 10-3. The single stage sample has a crystalline/amorphous interlayer structure and ∼ 20 nm thickness, which could lead to a compressive residual stress for the single stage sample and even for the multi-stage coating. The compressive residual stress delays the germination of tiny defects. Furthermore, the multi-stage structure presents more interfaces that can impede longitudinal crack propagation and limit corrosion media diffusion, which contribute to the corrosion resistance. The work not only proposes a good protective coating for magnesium alloy but also presents a strategy for corrosion resistant coating design.

Dissolution-precipitation method concatenated sodium alginate/MOF-derived magnetic multistage pore carbon magnetic solid phase extraction for determination of antioxidants and ultraviolet stabilizers in polylactic acid food contact plastics

Antioxidants and UV stabilizers have some endocrine disrupting effects and liver toxicity. Both types of additives are still widely used in food contact plastics to improve the durability of plastic products. However, efficient and rapid detection of antioxidants and UV stabilizers has been a challenge due to the complexity of the plastic matrix and the low content of antioxidants and UV stabilizers. In this study, a sodium alginate/MOF-derived magnetic multistage pore carbon material (MIL-101(Fe)/SA-CAs) was developed, having the merits of abundant multistage pore structure, large specific surface area, and good magnetic separation properties. Thus, this material was selected as the sorbent for magnetic solid-phase extraction combined with a dissolution-precipitation method for the extraction and purification of antioxidants and UV stabilizers from polylactic acid food contact plastics. The extraction parameters such as sorbent type, sorbent dosage, sample solution pH, ionic strength, sorption time, elution solution type, volume, and time were investigated. Under the optimized conditions, all the analytes determined by UPLC-MS/MS showed good linear range (r > 0.99), detection limit (0.023–3.105 ng g−1), accuracy (70.6–102.3 %), and reproducibility (RSD<9.8 %). Further, the developed method was applied to determine the antioxidants and UV stabilizers in polylactic acid lunch boxes and straws, showing excellent applicability. The results showed that the antioxidants and UV stabilizers were detected in some of the samples, with a maximum detection of antioxidant 1010 at 7297 ng g−1. This study provided a sensitive, efficient, and environmentally friendly method for antioxidants and UV stabilizers in polylactic acid food contact plastics. The ideas for the design of environmentally friendly metal-organic frameworks and biomass composite multifunctional materials would promise in the sample pretreatment field for the emerging contaminants.

Electrospun Nanofibrous Conduit Filled with a Collagen-Based Matrix (ColM) for Nerve Regeneration.

Traumatic nerve defects result in dysfunctions of sensory and motor nerves and are usually accompanied by pain. Nerve guidance conduits (NGCs) are widely applied to bridge large-gap nerve defects. However, few NGCs can truly replace autologous nerve grafts to achieve comprehensive neural regeneration and function recovery. Herein, a three-dimensional (3D) sponge-filled nanofibrous NGC (sf@NGC) resembling the structure of native peripheral nerves was developed. The conduit was fabricated by electrospinning a poly(L-lactide-co-glycolide) (PLGA) membrane, whereas the intraluminal filler was obtained by freeze-drying a collagen-based matrix (ColM) resembling the extracellular matrix. The effects of the electrospinning process and of the composition of ColM on the physicochemical performance of sf@NGC were investigated in detail. Furthermore, the biocompatibility of the PLGA sheath and ColM were evaluated. The continuous and homogeneous PLGA nanofiber membrane had high porosity and tensile strength. ColM was shown to exhibit an ECM-like architecture characterized by a multistage pore structure and a high porosity level of over 70%. The PLGA sheath and ColM were shown to possess stagewise degradability and good biocompatibility. In conclusion, sf@NGC may have a favorable potential for the treatment of nerve reconstruction.

Multistage pore structure legume-like UiO-66-NH2@carbon nanofiber aerogel modified electrode as an electrochemical sensor for high sensitivity detection of HMIs

Electrode material is the core component of electrochemical sensor, which has a decisive influence on the detection performance of heavy metal ions. A novel electrochemical sensor based on amino modified metal-organic frameworks loaded three-dimensional carbon nanofiber aerogel composite material was proposed. The UiO-66-NH2 was embedded into nanofibers through one-step electrospinning technology to forming a legume-like structure, ensuring the number of active sites N coordination with HMIs, which improved enrichment capacity of the sensor. 3D carbon nanofiber aerogel with multistage pore structure was developed by one-dimensional nanofibers as unit modules, which increases conductive path and HMIs transport channel. Accordingly, the UiO-66-NH2 @carbon nanofiber aerogel modified electrode (N-U@CFA/GCE) as an electrochemical sensor exhibited an ultra-high sensitivity and the low limit of detection for the simultaneous detection of Cd2+ (0.52 nM) and Pb2+ (0.46 nM) using the differential pulse anode stripping voltammetry and was feasible and accurate for the detection of actual environmental water. The novel sensor platform has high sensitivity, stability and anti-interference, which showing great potential on HMIs monitoring.

Investigation and optimization of load characteristics of a multi-stage load-reduction structure for vehicles during high-speed vertical water entry

Vehicles are subjected to intense impact loads during water entry at high speed, so some appropriate measures are taken to reduce the impact response of the structure. In this paper, a multi-stage load-reduction structure composed of foam aluminum and cavitation structure is designed to improve the load characteristics of high-speed vehicles. Its three-dimensional numerical model is established based on the Coupled Euler-Lagrange (CEL) method. The accuracy of the numerical simulation was verified by comparison with various experimental results of the sphere and AUV head section, and irrelevant grids were obtained. The simulation of a vehicle with and without a multi-stage load-reduction structure was carried out to study the load characteristics under the influence of different parameters such as vertical velocity and relative density of foam aluminum. Researches were also carried out to select the optimal parameters. The results show that the impact acceleration and the optimal density increase synchronously with the initial velocity. The installation of the multi-stage structure transforms the single impact of direct water entry into three reduced acceleration peaks, and finally realizes the load reduction. When the velocity is 100, 200 or 300 m/s, the load reduction rates under the optimum density are up to 84.6%, 83.7% and 79.3%.

A tunable balanced phase shifter with wide operating bandwidth

Abstract A wideband tunable balanced phase shifter is achieved by utilizing varactor-loaded coupled lines (VLCLs)-embedded multistage branch-line structure. The tunable phase shift with low in-band phase deviation is attributed to the regulation in phase shift of the VLCLs and the horizontal microstrip lines in series. The wideband differential-mode (DM) impedance matching and common-mode (CM) suppression are due to multiple DM transmission poles and CM transmission zeros, which are brought about by the cascade of VLCLs and a microstrip line with short-circuited stubs in the DM-equivalent circuit and open-circuited stubs in the CM-equivalent circuit, respectively. Compared with the state-of-the-art tunable balanced phase shifters, the proposed design not only has the advantages of wide operating bandwidth (BW) with low in-band phase deviation but also has low insertion loss and easily fabricated structure. Theoretical analysis and design procedure were conducted, resulting in a prototype covering the frequency of 1.8 GHz. This prototype offers a tunable phase shift capability ranging from 0° to 90°. The prototype exhibits an operating BW of 45%, with a maximum phase deviation of ±6°. It also achieves a 10 dB DM return loss and CM suppression, while maintaining a maximum insertion loss of 2.5 dB.

Nonlinear symbolic regression for bit error rate prediction of NOMA systems in 5G cellular communications

Machine learning (ML) has been suggested as a promising tool in the design of telecommunication systems to overcome the challenges of traditional methods and meet the requirements regarding future cellular networks. As an enabler of 5G communications, Non-orthogonal multiple access (NOMA) has emerged to adaptively manage the existing resources and received huge attention in terms of performance analysis to confirm its efficiency in resource management. This work addresses the applications of nonlinear symbolic regression (NLSR) techniques to evolve mapping models for bit error rate (BER) prediction in the downlink NOMA systems with perfect and imperfect successive interference cancellation (SIC) receivers. In this regard, a multi-stage structure is proposed to evaluate the BER using the related inputs as well as the output of the previous stages for imperfect SIC signal decoding. Each step consists of an NLSR block with different inputs and an output, which inputs include the effective parameters and the output of the previous stages. Experimental results confirm that the NLSR techniques are able to establish modeling expressions with good prediction accuracy compared to other benchmark methods. In particular, these ML-based techniques overcome the limitation of the classical approaches in modeling a closed-form BER formula, especially for the NOMA systems with more than two users. In addition, this BER prediction tool can be utilized by the NOMA base station as new side information for more optimal resource management.

Inter-stage performance and energy characteristics analysis of electric submersible pump based on entropy production theory

The electric submersible pump (ESP) is a crucial apparatus utilized for lifting in the oil extraction process. Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production (EP) analysis, which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.