Cavitation Process Research Articles

Research on Rapid Detection Method of Cavitation State of Water jet Propulsion Pump Based on Multi-source and Multi-feature of Acoustic Emission Signal and Bayesian Network

Abstract Cavitation prevents the conversion of internal dynamic and pressure energy in a water jet propulsion pump and causes erosion of flow passage components. Acoustic emission is a non-destructive test method for instability signals. Based on the incipient mechanism and development process of cavitation, three acoustic emission signal feature parameters (ring counting rate, energy release rate, Hurst index) are proposed to define the cavitation state utilizing the waveform pattern and signal self-similarity. The multi-source and multi-feature cavitation identification model of acoustic emission signals is established through cavitation simulation, multi-monitoring point acoustic emission signal testing, and feature parameter extraction, and a large number of probabilistic trainings are carried out using Bayesian network, resulting in a fast cavitation state identification method based on acoustic emission signals. The research results have important practical engineering application significance for the prediction of cavitation resistance, real-time dynamic monitoring of cavitation phenomenon and prevention of cavitation damage.

Flow Structure and Periodic Processes in a Disc-Shaped Vortex Chamber of a Hydrodynamic Cavitator

Introduction. The essence of the acoustic – cavitation processes is that the liquid is passed through sound with a pressure at the wave surface of more than 3 bar that causes local breaks of the liquid in the vacuum phase of the wave and the collapse in the manometric phase. The opposite walls of each cavern in the collapse approach at a speed exceeding two speed of sound, due to which a high energy density is achieved at the meeting point, and what is especially valuable is the mutual transitions of energies from one form to another, unattainable under normal conditions, and, moreover, as inside cavitation area and near it. The novelty of the work is confirmed by the results of a periodic information and patent analysis, and by four patents received for inventions on the topic under consideration.Aim of the Study. The study is aimed at improving the acoustic-cavitation qualities of a disk-shaped vortex chamber used as a liquid whistle.Materials and Methods. In the study, there were used numerical modeling of flows in the FlowVision program, experimental determination of flow rates using a pitot tube, film method, removal of frequency response using SpectraPLUS 5.0, and visualization of flows and processes on optically transparent devices by the method of color indicators in stroboscopic lighting high-speed video shooting.Results. The mechanism of sound generation and noise in the flow transiting through the device has been found. The corrective effect of pump pulsations f = 300 Hz on the sound generation mechanism was revealed. The disc-shaped character of the device, which encloses the input flow in cross section from three directions, contributes to creating a more expressive acoustic signal, forming two conjugate torus vortices along the shell that ensures uniformity of the circumferential flow, attenuation of longitudinal high-frequency oscillations f = 200 kHz, and the creation of periodic zones of increased pressure along the shell. The concentrated tangential entrance to the device determines the central asymmetry of the flows in it and a number of processes that create acoustic noise.Discussion and Conclusion. The frequency of the useful acoustic signal in the vortex chamber is proportional to the speed of the transit flow, and the amplitude is proportional to the dimensions of the device. Along with the useful signal created by the interaction of the peripheral and input parts of the transit flow, noise of similar frequencies is created in the device. Other sources of noise generation are due to the presence of a concentrated tangential input. The formation of two conjugate torus vortices along the shell can be used as a means of controlling the process of interaction between parts of the transit flow. The disc-shaped vortex chamber combines the functions of sound generation and the ability to create a centrifugal field, which expands its technological capabilities.

Synergistic Degradation of Methylene Blue by Hydrodynamic Cavitation Combined with Hydrogen Peroxide/Vitamin C System.

In this study, a new combined process of hydrodynamic cavitation (HC) and a hydrogen peroxide/vitamin C (H2O2/Vc) system was proposed for the degradation of methylene blue (MB) in wastewater. An impact-jet hydraulic cavitator was used as the cavitation generation equipment, and H2O2/Vc was selected as a homogeneous oxidation system. The degradation characteristics of MB were investigated. The results showed that the degradation effect of HC in combination with the H2O2/Vc system was more effective than that of the individual HC or H2O2/Vc system. A maximum degradation rate of 87.8% was achieved under the following conditions: H2O2 concentration of 0.03 mol/L, Vc concentration of 0.021 mol/L, inlet pressure of 0.3 MPa, initial solution concentration of 4 μmol/L, solution volume of 150 mL, and reaction time of 10 min. The synergy index was 1.615, indicating a synergistic effect between the HC and H2O2/Vc system. The data of the hydroxyl radical (·OH) yield under the conditions of HC, the H2O2/Vc system, and the HC + H2O2/Vc system were fitted and analyzed. A correlation equation for ·OH yield was established, further revealing the synergistic mechanism of the HC and H2O2/Vc system. The intermediate products of MB degradation were detected based on LC-MS, and three possible degradation pathways of MB degradation were proposed. The combined process of HC and H2O2/Vc systems exhibited relatively low energy efficiency and operating cost, indicating that it was in line with the development direction of wastewater treatment.

A comprehensive study on the effects of annular protrusion for cavitation intensification in Venturi tubes

Hydrodynamic cavitation, a novel advanced oxidation technique that is notable for its high performance on energy efficiency and environmentally friendly, has incited broad interest. Enhancement of cavitation forms an emerging field in this context. A semi-circular annular protrusion has been introduced into Venturi tubes for cavitation intensification. Initially, improved multiphase flow-cavitation chemical effect simulations are constructed, enabling accurate estimations of the cavitation process on multiscale. Based on this model, an in-depth analysis is carried out to reveal the influential mechanisms of protrusion. Subsequently, optimization of protrusion structure is conducted through a comprehensive analysis of cavitation flow characteristics. The interaction between pressure and protrusion structure are further explored utilizing multi-factor optimization methods. Results indicate a significant performance improvement on the cavitating Venturi tube with a semi-circular annular protrusion. This is attributed to an extended low-pressure area, prolonged high-speed duration, and the increase in both collapse pressure and temperature, yielding higher amounts of free radicals. The semi-circular protrusion is superior to the triangle and rectangle shape. Its position and height significantly impact cavitation intensity in accordance with the generated cavitation patterns, pressure distribution, velocity magnitude and streamlines. Interactive factors analysis reveals strong linear relationships between optimal protrusion height, position and inlet pressure (R2 = 0.999 and 0.992). In comparison to smooth Venturi tubes, recommended designs have shown the vapor volume fraction enhanced by 212 %, 230 %, 255 %, and 117 % at 3, 4, 5, and 6 bar. Accordingly, the ˑOH prediction multiplies to 23 times, 33 times, 107 times and 3 times. This study provides theoretical backing for engineering applications of the semi-circular annular protrusion in Venturi tubes and contributes towards improved cavitation efficiency and reduced experimental and time costs.

Nonlinear dynamics of a bubble cluster in liquid cavity wrapped by elastic medium

Abstract According to the modified nucleation theory, gas nuclei can generate and grow into cavitation bubbles when’s the liquid pressure exceeds a threshold in a cavity. Based on the modified nucleation theory, the growth process of the gas nuclei in a liquid cavity can be simplified to two “events”, and the full confinement effects of the surrounding elastic medium of the cavity was considered by including the bulk modulus in the equation of state. The dynamical equations were derived to model the nonlinear oscillation of the multi-bubble system in the cavity. The effects of acoustic parameters, the initial radius and the total number of bubbles on bubble dynamics were investigated numerically. It is found that bubble behaviors are sensitive to the acoustic field. In the low frequency region (f <1MHz), bubble oscillation exhibits a modulated waveform, and fundamental, subharmonic and harmonic modes can be found in the acoustic response curve. The oscillations of confined bubbles diminish with increasing frequency. In the high frequency region (f >1MHz), the confinement state affects the acoustic response of the gas nuclei, and the growth rate differ by a factor of 5 difference in the presence of shelled or unbounded elastic confinement of the cavity. Therefore, the suppression or enhancement of cavitation growth and collapse in confined cavity can be modulated by a variety of factors, such as the total number of nuclei, cavity size, acoustic frequency and amplitude, negative pressure, and elastic medium, which have a synergistic influence on the confined cavitation process.

Data-driven insights into cavitation phenomena: From spatiotemporal features to physical state transitions

The application of data-driven methods to study cavitation flow provides insights into the underlying mechanisms and richer physical details of cavitation phenomena. This paper aims to analyze the physically interpretable multi-state cavitation behavior. Initially, the spatiotemporal features of the cavitation flow are represented as network trajectories using principal component analysis. The k-means++ algorithm is then employed to obtain coarse-grained flow field states, and the centroid of each cluster served as a representative for the attributes of that state. Subsequently, the Markov state model is constructed to capture the dynamic transitions in the cavitation flow field. Through a detailed analysis of the dynamic transition model, the cavitation flow field states with genuine physical mechanisms are refined. Finally, proper orthogonal decomposition (POD) is utilized to extract the flow patterns corresponding to different states. The distribution characteristics of the flow field modes in different states correspond to their physical properties. These data-driven algorithm enables a detailed analysis of the typical states in periodic cavitation processes, such as cavity growth, development, shedding, and collapse, providing a deeper understanding of the cavitation flow characteristics in different typical states.

Effect of organic solvent additives on the enhancement of ultrasonic cavitation effects in water for lithium-ion battery electrode delamination

Ultrasonic delamination is a low energy approach for direct recycling of spent lithium-ion batteries. The efficiency of the ultrasonic delamination relies both on the thermophysical properties (such as viscosity, surface tension, and vapour pressure) of the solvent in which the delamination process is carried out, and the properties of the ultrasound source as well as the geometry of the containment vessel. However, the effect of tailoring solutions to optimise cavitation and delamination of battery cathode coatings has not yet been sufficiently investigated. Acoustic detection, high-speed imaging, and sonochemiluminescence (SCL) are employed to study the cavitation processes in water-glycol systems and identify the effect of tailoring solvent composition on cavitation strength. The addition of small volume fractions of organic solvent (ca. 10–30 vol%), including ethylene glycol or glycerol, to the aqueous delamination solution were found to significantly improve the delamination efficiency of lithium-ion battery cathode coatings due to the alteration of these thermophysical properties. However, greater volume fractions of glycol decrease delamination efficiency due to the signal-dampening effect of viscosity on the ultrasonic waves. The findings of this study offer valuable insights for optimising ultrasonic bath solution composition to enhance film delamination processes.

Preliminary treatment of landfill leachate by hydrodynamic cavitation supported by Fenton process

Hydrodynamic cavitation as an effective and environmentally friendly method of treating wastewater. Massive amounts of energy may be released into the surrounding liquid during hydrodynamic cavitation, resulting in mechanical , chemical and thermal impacts. Bacteria and organic materials in sewage can be broken down by these circumstances. Furthermore, a coupling effect may be created by combining hydrodynamic cavitation with other water treatment techniques. In this study it is aim to investigate and improve the hydrodynamic cavitation (HDC) process supported by Fenton process for the pretreatment of landfill leachate. In the second phase of the study, the effectiveness of the hydrodynamic cavitation process was investigated in conjunction with the Fenton process. The parameters such as the number of cavitation events, pH, and temperature were evaluated. The effluent was characterized and monitored for COD measurements. The consequences of operational variables such H2O2, Fe+2 , and pH values were investigated to determine the optimal Fenton oxidation process parameters. The findings of the experiment showed that pH values were ideal for Fenton oxidation of 3.5-4.5, 30 mM H2O2, and 5 mM Fe+2. A combined treatment process of Fe+2+H2O2, HDC + Fenton, and Cavitation alone were conducted for the treatment of landfill leachate. The results showed that the removal rates of chemical oxygen demand (COD) for the combined processes were 32.85%, 44.28%, and 7%, respectively. Temperature, pH, and the number of cavitation events were among the parameters that were assessed. The effluent was measured for COD and was characterized.

Degradation of Procion Golden Yellow H-R Dye Using Ultrasound Combined with Advanced Oxidation Process

The current study aims to degrade Procion Golden Yellow H-R through ultrasound-induced cavitation coupled with various oxidants. A comprehensive investigation was conducted to examine the impact of parameters, specifically pH, power, and frequency, on the extent of degradation. The primary aim was to optimize degradation by solely utilizing a cavitation reactor where only 23.8% degradation was observed under the established optimum conditions of pH 2.5, frequency of 22 kHz, and power of 200 W. The investigation of the combined process of cavitation with H2O2, Fenton reagent (H2O2/Fe2+), NaOCl, and potassium persulphate (KPS) was subsequently conducted under optimized conditions. The combined operations greatly enhanced degradation with the use of H2O2 loading of 0.1 g/L leading to 53.3% degradation and the H2O2/Fe2+ ratio of 1:0.25 resulting in 94.6% degradation, while the NaOCl quantum of 0.075 g/L yielded 90% degradation and the KPS quantity of 2 g/L resulted in 97.5% degradation in the specific combinations. A toxicity test on two bacterial strains, Staphylococcus aureus and Escherichia coli, was carried out using the original dye solution and after treatment. The various individual and combination processes were compared using the parameters of cavitational yield and total treatment cost. The study elucidates that combining ultrasonic cavitation with KPS is an effective method for treating wastewater containing Procion Golden Yellow H-R dye, especially when implemented at a larger scale of operation.

Rankala Lake quarry water purification via a dual strategy involving hydrodynamic cavitation and ozonation

This research presents a ground-breaking approach to wastewater treatment that leverages hydrodynamic cavitation and ozonation with unprecedented efficiency and environmental benefits by resolving the concern of the ever-present paradox of water scarcity and persistent pollutants in wastewater, and it compels scientists to relentlessly pursue innovative and eco-friendly treatment solutions. This study introduces a pioneering method for treating wastewater employing a sequential approach of hydrodynamic cavitation (HC) coupled with subsequent ozonation (O3). This research examined the process of purifying rainwater collected from the Rankala Lake quarry in Kolhapur, India. The treatment, which lasted for approximately 7 hours each day over a span of three weeks, resulted in notable enhancements in water quality. The initial greenish discoloration and bad odor were notably eradicated within a week, without any chemical additives. The microbial burden decreased significantly from 105 CFU/mL to 102 CFU/mL, indicating a strong level of disinfection. The COD decreased significantly from 110 ppm to less than 10 ppm, while the BOD decreased dramatically to undetectable levels (0 ppm) from 55 ppm. In addition, there was a slight change in the concentration of chloride, water hardness, clarity, and total dissolved solids (TDS). This exemplifies the efficacy of the cavitation process coupled with ozonation for converting polluted, discolored, and malodorous water into purified water appropriate for diverse uses.

Soluble hemp protein-xylose conjugates fabricated by high-pressure homogenization and pH-shifting treatments.

The process of Maillard conjugation occurs with plant proteins and sugars and can be influenced by several factors, such as processing time, pH, and shear force. By utilizing cavitation processes such as high-pressure homogenization (HPH) and pH-shifting, it is possible to regulate the degree of grafting, functional characteristics, and structural changes in the formation of conjugates. The present study aimed to improve the hemp protein concentrate (HPC) through two different conjugation techniques: HPH and pH-shifting-assisted processes. The best conjugation conditions for the conventional method were identified as a 1:2 HPC to xylose ratio, a pH of 10, and 3 h of treatment at 70 °C. The use of HPH and pH 12-shifting methods resulted in a remarkable 2.5-fold increase in grafting degree, requiring less processing time. Fourier transform infrared spectra confirmed the formation of conjugates. Conjugates produced through HPH with pH 12-shifting (MPHX) transformed into soluble glycoproteins with a particle size of 74 nm. MPHX solubility increased by 5.7-fold than HPC, reaching 85.7%, with a more negatively charged surface at -32.4 mV. Microimages showed cracked and sharp forms for conjugated proteins compared to untreated HPC. Additionally, MPHX conjugates demonstrated superior properties in emulsion stability, foaming capacity, and antioxidant activity compared to HPC and classical conjugates. The use of HPH and pH-shifting-assisted Maillard conjugation was highly effective in enhancing the functional attributes of hemp protein conjugates. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Microstructure evolvement and wear properties of Ni60-based coating by ultrasonic power-assisted laser cladding

Ultrasonic vibration is known to cause significant refinement of microstructure, the effect of ultrasonic power on grain size, grain orientation and Schmid factor by laser cladding in the Ni60/WC composite coating was studied systematically. Meanwhile, the effect of microstructure on wear properties and hardness was elucidated. The results show that the performance of the cladding layer is the best when the ultrasonic power is 600 W, which is due to the combined effect of ultrasonic cavitation and acoustic flow. The average grain diameter is refined from 28.36 μm to 23.02 μm, and the refinement range is 18.9%. The formation of low Angle grain boundaries (LAGBs) is promoted by ultrasound, and the dislocation density is increased. The texture strength of the coating is distributed over {100}, {110} and {111} surfaces, and the strength decreases from 12.307 to 5.447 The microhardness is increased by 16% (from 768.85HV1 to 896.95HV1), the wear mechanism gradually from adhesive to abrasive wear and the average friction coefficient decreases from 0.47 to 0.216 with the increase of ultrasonic power, which improve the wear resistance of the coatings. Based on the understanding of microstructure evolvement, the grain refinement mechanism effected by ultrasonic power was explained from the aspect of cavitation processes.

Investigation of Cavitation Flow and Entropy Production Characteristics in a Dual-Rotor Turbine Flowmeter

Flow meters are extensively utilized in fields such as chemical engineering, petroleum, and aerospace, and are an indispensable component of modern industry. This paper examines the metrological properties of a dual-rotor turbine flow meter within its measurable flow range through experimental approaches and investigates the cavitation flow dynamics within the flow meter using numerical methods. First, the flow characteristics curve of the dual-rotor turbine flow meter was established experimentally, and the accuracy of numerical simulation results was validated. Secondly, the transient characteristics of the cavitation cavity were revealed using the Z-G-B cavitation model and dynamic mesh technology. Finally, entropy production theory was applied to investigate the energy losses caused by cavitation, analyzing the contributions of different types of energy losses during the cavitation process. Flow calibration experiments and numerical simulations reveal an increase in the meter coefficient of the dual-rotor turbine flow meter in high-flow cavitation zones, indicating that the displayed flow rate is slightly higher during cavitation compared to non-cavitating flows. Transient cavitation flow undergoes three stages: attachment, development, and collapse. At 323 K, the volume fractions of upstream and downstream cavities increase by 38.9% and 48.3%, respectively, with the cavitation cycle duration being 1.21 times that at 298 K. At 343 K, these increases are 75.3% and 239.2%, with the cycle duration being 2.63 times that at 298 K. Among the various sources of loss, the contribution from losses due to pulsating velocity gradients is the most significant, with maximum proportions of 81.95%, 85.1%, and 87.11% at 298 K, 323 K, and 343 K, respectively.

Evaluation of tool wear during micro-milling of ultrasonically assisted abrasive peened Ti-6Al-4V

When a cutting tool shears through a workpiece, the interaction causes wear of the tool which is based on relative hardness, surface characteristics of the tool and the workpiece, cutting environment and thermal behaviour at the work/tool interface. In this study, wear of a micro-end milling tool is investigated while milling of as-received and peened work material (in this case, Ti-6Al-4V). The peening is performed with the help of an in-house developed ultrasonic cavitation process. The process excites the abrasives suspended in the cavitating medium, which impart on the work surface and induce compressive residual stress and uniform grain refinement. As the cutting process advances, a built-up is formed more rapidly in the as-received workpiece, leading to higher cutting forces and earlier chipping of the cutting edge. Under the peened conditions, it is found that the increase in tool edge radius and flank wear width reduce by 50 % and 54 % respectively compared to the as-received one. Additionally, peening-induced grain refinement leads to a 26 % decrease in surface roughness of the machined surface and inhibits burr formation by 60 %. A tool wear chipping model is employed to predict the tool diameter, cutting edge radius and flank wear width of the worn tool. Results show that the magnitude of flank wear, edge radius of worn tool and tool diameter deviate from experiments by 15.2 %, 14 % and 13 % respectively.

Enhancing wastewater treatment efficiency through hydrodynamic cavitation and advanced oxidation processes: Experimental insights and comparative analysis

BackgroundThe escalating industrial wastewater production mandates effective treatment methods to mitigate environmental and health risks. Hydrodynamic cavitation (HC) and its combination with advanced oxidation processes (AOPs) offer promising approaches for wastewater pollution reduction. MethodsThis study investigates the enhancement of HC efficiency for Chemical Oxygen Demand (COD) reduction by integrating hydrogen peroxide (H2O2) and air injection. Synthetic wastewater resembling industrial effluent COD levels serves as the experimental medium. Varied inlet pressures, H2O2 concentrations, and air injection rates were examined to gauge their impact on COD reduction. Significant FindingsHigher inlet pressures directly correlate with increased COD reduction, highlighting intensified cavitation effects. Combining HC with H2O2 or air, especially when directly injected into the venturi throat, showcased substantial synergy, significantly reducing COD levels. Notably, the maximum extent of COD reduction, achieved at 51.85 %, was with the combination of (HC+H2O2+Air). The COD reduction percentages for other processes, including HC alone, (HC+Air tank injection), (HC+Air throat injection), (HC+H2O2 tank injection), and (HC+H2O2 throat injection), were 4.21 %, 19.7 %, 20.9 %, 37.8 %, and 39.4 %, respectively.

Analysis of Microbubble-Blood cell system Oscillation/Cavitation influenced by ultrasound Forces: Conjugate applications of FEM and LBM

Sonoporation is a non-invasive method that uses ultrasound for drug and gene delivery for therapeutic purposes. Here, both Finite Element Method (FEM) and Lattice Boltzmann Method (LBM) are applied to study the interaction physics of microbubble oscillation and collapse near flexible tissue. After validating the Finite Element Method with the nonlinear excited lipid-coated microbubble as well as the Lattice Boltzmann Method with experimental results, we have studied the behavior of a three-dimensional compressible microbubble in the vicinity of tissue. In the FEM phase, the oscillation microbubble with a lipid shell interacts with the boundary. The range of pressure and ultrasound frequency have been considered in the field of therapeutic applications of sonoporation. The viscoelastic and interfacial tension as the coating properties of the microbubble shell have been investigated. The presence of an elastic boundary increases the resonance frequency of the microbubble compared to that of a free microbubble. The increase in pressure leads to an expansion in the range of the microbubble’s motion, the velocity induced in the fluid, and the shear stress on the boundary walls of tissue. An enhancement in the surface tension of the microbubble can influence fluid flow and reduce the shear stress on the boundary. The multi-pseudo-potential interaction LBM is used to reduce thermodynamic inconsistency and high-density ratio in a two-phase system for modeling the cavitation process. The three-dimensional shape of the microbubble during the collapse stages and the counter of pressure are displayed. There is a time difference between the occurrence of maximum velocity and pressure. All results in detail are presented in the article bodies.

ASESSMENT OF THE EFFECTIVENESS OF CAVITATION PROCESSING OF DARK OIL PRODUCTS

The paper presents experimental results of the influence of the conditions of cavitation treatment of dark petroleum products in the hydrodynamic regime on the yield of fractions boiling up to 400 °C. Straight-run products (fuel oils, vacuum gas oils), as well as catalytic cracking gas oils, were considered as raw materials. The influence of raw material characteristics (density, fractional and group hydrocarbon composition) and its processing conditions (pressure, at five cycles of exposure) on the yield of the target fraction is considered. The linear dependence of the yield of the target fractions on the processing pressure is revealed. The constructed regression models are adequate, informative, and all their coefficients are significant. Taking into account the density of the feedstock did not improved models. The best model constructed was tested using the cross-validation method. The average forecast error was 11%, the maximum was 22%. For a small number of samples, such an error is acceptable. The possibility of assessing the effectiveness of cavitation treatment of crude oil based on data on its fractional and group hydrocarbon composition is shown. It was possible to build several regression models linking the increase in yield with pressure during processing and the content of resins and oils in the raw materials. All of them are adequate and informative, and their coefficients are significant. The increase in the yield of fractions boiling up to 400 °C is associated with the transformations of hydrocarbons during cavitation. The possibility of evaluating the effectiveness of cavitation treatment of petroleum raw materials based on data on its group hydrocarbon composition has been established. Several regression models have been constructed linking the increase in yield with the pressure during processing and the content of resins and oils in the raw materials. All of them are adequate and informative, and their coefficients are significant. Based on the constructed models, it is assumed that the change in the fractional composition of petroleum products during cavitation treatment is more associated with the destruction of the transition and solvate layers of complex structural units of the oil dispersed system than with the course of cracking reactions. For citation: Peshnev B.V., Burlyaeva E.V., Nikishin D.V., Nikolaev A.I., Kuznetsov A.S. Asessment of the effectiveness of cavitation processing of dark oil products. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 103-110. DOI: 10.6060/ivkkt.20246707.7006.

Evolution of the cavity structure of HDPE/UHMWPE blends during cold stretching

AbstractThe cavitation process of high‐performance HDPE/UHMWPE blends with a uniform dispersion of UHMWPE during cold stretching was investigated. It was observed that incorporating a small amount of UHMWPE into the HDPE matrix resin can serve as a nucleating agent, increasing the number of contact sites and accelerating the crystallization rate. This leads to the formation of thicker lamellar crystals and tethered molecules, ultimately enhancing the mechanical properties of the HDPE matrix. Furthermore, the relationship between the natural tensile ratio and strain‐hardening modulus was confirmed. Microstructural changes within the blends were also explored. As the drawing tangles in the middle, the cavities subsequently evolve by collapsing and merging to align parallel to the tensile direction, culminating in tensile damage forming a large crack in the final macroscopic form. As a result, the presence of more tethered molecules in the later stages of stretching inhibits further cavity growth.Highlights The HDPE/UHMWPE blends were prepared by solution blending and ultrasound‐assisted twin‐screw extrusion. The mechanisms underlying the formation and evolution of cavities in HDPE/UHMWPE blends, which lead to stress whitening during tensile damage, were examined by using DSC and SAXS/WAXD. The relationship between microstructure and mechanical properties was analyzed by cold‐drawing the molded blended sheets at room temperature.

CAVITATION PROCESSES IN THE MULTIPORT BALL VALVE SYSTEMS

Valves are essential components of a fluid management system, and their proper functioning is critical to ensuring the system's efficiency and durability. Multiport ball valves are versatile and commonly used in various industries to control fluid flows. These valves have multiple ports or outlets, allowing for different flow paths and configurations. One of the key considerations when using multiport ball valves is the flow characteristics within the valve itself. The flow within multiport ball valves is governed by several factors, including the design of the valve and the pressure drop across it. Understanding the flow behavior in multiport ball valves is crucial for optimizing their performance and ensuring efficient fluid handling. Different flow paths and configurations in multiport ball valves result in varying flow characteristics. For example, in a three-way multiport ball valve, there are typically two inlet ports and one outlet port. The flow can be diverted from one inlet to the outlet, or it can be split between the two outlets. This flow behavior is influenced by the presence of a constant throttling channel in the valve design.The constant throttling channel helps regulate the flow rate through the valve, and its size and shape can impact the flow characteristics. Additionally, the flow behavior in multiport ball valves can be further influenced by factors such as the material properties of the valve and the flow conditions. Furthermore, the overall flow behavior in multiport ball valves can have an impact on mass transfer and chemical reactions in the system. Different flow patterns and configurations within multiport ball valves can affect the mass transfer and transport characteristics in a system. For example, if the flow is not well-distributed or if there are areas of stagnant flow, it can lead to uneven mixing and reaction rates. Keywords: Multiport ball valve, cavitation, fluid characteristics, control of cavitation processes.

Characterisation of the creep cavitation process on grain boundaries in a polycrystalline nickel-base alloy 247

ABSTRACT Hot gas components such as gas turbine blades are loaded with constant centrifugal stress at high temperatures and thus the formation of creep cavitation on grain boundaries is expedited. Conventionally cast polycrystalline Nickel-base superalloys used as blade materials are prone to creep cavitation as unfavourably orientated grain boundaries exist. This research presents a diffusion-based probabilistic creep model which describes the creep cavitation process on grain boundaries. It includes the three mechanisms: pore nucleation, growth, and coalescence. The calibration of the model has been carried out by analysing Alloy 247 as-received specimens and specimens with pre-strain. For the evaluation of the pore numbers and sizes, a deep learning model for pore detection was trained on light microscopic and scanning electron microscopy images. Electron backscatter diffraction images are analysed for further investigations regarding grain orientations and grain boundary angles to the loading direction. The calibrated model allows predictions of pore size distributions over time.