Cavitation In Nozzle Research Articles

Implementation of a VoF solver with phase change for the simulation of internal cavitation and droplet breakup in injectors

This study presents the implementation and derivation of a Volume of Fluid (VoF) solver capable of taking into account pressure driven phase change and handle three fluids. The implemented code is designed to investigate internal nozzle cavitation and subsequent injection and jet breakup. An extended cavitation model is also implemented that can handle phase change in the presence of a third phase. Detailed description and derivation of the mathematical system is presented. The solver is validated on a one-dimensional benchmark case from the literature and verified on an experimentally well-documented geometry. The verification shows the developing cavitation regime is well captured by comparing velocity profiles and flow images with experimental measurements and visualisation.

Optimization of Composite Cavitation Nozzle Parameters Based on the Response Surface Methodology

Cavitation is typically observed when high-pressure submerged water jets are used. A composite nozzle, based on an organ pipe, can increase shear stress on the incoming flow, significantly enhancing cavitation performance by stacking Helmholtz cavities in series. In the present work, the flow field of the composite nozzle was numerically simulated using Large Eddy Simulation and was paired with the response surface method for global optimizing the crucial parameters of the composite nozzle to examine their effect on cavitation behavior. Utilizing peak gas-phase volume percent as the dependent variable and the runner diameter, Helmholtz chamber diameter, and Helmholtz chamber length as independent variables, a mathematical model was constructed to determine the ideal parameters of the composite nozzle through response surface methodology. The optimized nozzle prediction had an error of only 2.04% compared to the simulation results, confirming the accuracy of the model. To learn more about the cavitation cloud properties, an experimental setup for high-pressure cavitation jets was also constructed. Impact force measurements and high-speed photography tests were among the experiments conducted. The simulated evolution period of cavitation cloud characteristics is highly consistent with the experimental period. In the impact force measurement experiment, the simulated impact force oscillates between 256 and 297 N, and the measured impact force oscillates between 260 N and 289 N, with an error between 1.5% and 2.7%. The simulation model was verified by experimental results. This study provides new insights for the development of cavitation jet nozzle design theory.

Structure Design Of ROV-Based MOPU Platform Pin Hole Spin Cleaning Device

The pile legs of the MOPU platform have been submerged in seawater for a long time, and there are a large number of Marine organisms on the surface, which has a negative impact on the stability of the platform and needs to be cleaned regularly. Most of the existing jacket cleaning technologies are aimed at cleaning the outer surface, and there are few studies on cleaning the Marine organisms attached to the pin holes of the pile legs of MOPU platform. In order to solve the above problems, this paper firstly designs a spin-type pin hole cleaning device based on underwater wall-climbing robot by drawing lessons from domestic and foreign experience. At the same time, the Fluent simulation of three commonly used cavitation water jet nozzles is carried out, and the most suitable nozzle type for pin hole cleaning is selected from the organ pipe type, shear type and corner cavitation nozzles. In the actual operation, the water temperature and depth around the ROV are changing, so the simulation needs to consider the influence of temperature and depth changes. In this paper, a reasonable point is put forward for the structural design of the spin cavitation cleaning device. The simulation results show that the corner cavitation nozzle should be selected in the pinhole cleaning operation.

NUMERICAL INVESTIGATION OF SUBMERGED HYBRID CAVITATION JET NOZZLE BASED ON STRESS-BLENDED EDDY SIMULATION MODEL

Cavitation jet technology is extensively applied in fields such as mechanical processing, rock fragmentation, and energy development. To further enhance the cavitation capability of the nozzle, first a submerged organ pipe-angular hybrid cavitation nozzle model is established using the software SOILDWORKS. Second, the stress blended eddy simulation (SBES) technology is applied, and the jet law of internal and external flow field of submerged cavitation nozzle is studied numerically using FLUENT. Finally, the periodic shedding of cavitation clouds and the velocity characteristics and vapor volume fraction are studied for different expansion or contraction angles. The study revealed that the cavitation first occurs in the expansion section. With the development of cavitation, the asymmetry of the cavitation cloud increases significantly. Under an inlet pressure of 20 MPa, the fluctuation part of velocity is more concentrated. As the pressure increases, the maximum jet distance and velocity also increase.

Jet Characteristics and Optimization of a Cavitation Nozzle for Hydraulic Fracturing Applications

Jet Characteristics and Optimization of a Cavitation Nozzle for Hydraulic Fracturing Applications

Experimental and numerical simulations to examine the mechanism of nozzle geometry affecting cavitation water jets

The geometry of the cavitation nozzle is the major determinant of the cavitation process and cleaning effect. To better service the cleaning industry, it is necessary to understand the process by which nozzle geometry impacts cavitation. This research uses experimental flow visualization and large eddy simulation (LES) to study the cavitation effects of three different nozzle configurations (Cylindrical, organ-pipe and converging–diverging nozzles). The shedding frequency of the cavitation cloud was determined through power spectrum analysis (PSD). The collapse range of the cavitation cloud produced was measured using the frame difference technique (FDM). A cleaning experiment was carried out to remove the tube scale with the aim of assessing the performance of the nozzle. The findings indicate that under the impact of the re-entrant jet, the cavitation cloud was distorted and fractured, and large shear stresses were produced at the fracture sites. The cylindrical nozzle creates a flow field with more vapour, velocity, and Reynolds stress than the other two nozzles. The findings from the cleaning experiments indicate that the utilization of appropriate nozzle geometry and an optimal standoff distance can significantly enhance the efficiency of tube descaling. This paper can help choose the right nozzle geometry and standoff distance for the cavitation water jet cleaning process, offer crucial technical support for the efficient cleaning within tubes.

Optimization Design And Experimental Study of Self-oscillating Cavitating Jet Descaling Nozzle Based On Cleaning Operation

The scale of tubing in polymer flooding and ASP flooding Wells is serious in Daqing oilfield. In order to improve the cleaning effect of tubing, the self-vibrating cavitation jet nozzle was developed and the cavitation jet technology was used to remove scale. In the design of nozzle structure, it is necessary to derive the basic relation that the structure of the oscillating cavity should satisfy when strong resonance is generated, and calculate the key length dimension L1 of the oscillating cavity. The numerical simulation method the different diffusion Angle α and diffusion length L3 nozzle wall under the condition of gas generation rate and axial velocity distribution, determine the optimum size of diffuser. The scale-removing performance test of cavitation jet verifies the performance of self-vibration cavitation nozzle and determines the optimal target distance and injection Angle. According to the reasonable dimension relation of the oscillating cavity when resonance occurs, the length L1 of the oscillating cavity when strong resonance occurs is calculated as 10.4mm. Use Fluent fluid calculation software painted wall gas generating rate, the relationship between the axial velocity curve, determine the diffusion Angle α to 30°, spread long L3 is 2.5 mm, jet cavitation effect is best. The descaling performance test shows that under the inlet pressure of 20MPa, the target distance of 15mm and the injection Angle of 60°, the effective cleaning area is the largest within 1s. The designed nozzle has a reasonable structure and efficient descaling performance.

Numerical Investigation of Cavitating Jet Flow Field with Different Turbulence Models

In numerous industries such as drilling, peening, cleaning, etc., a cavitating jet is adopted. However, it is challenging to simulate the cavitating flow field numerically with accuracy. The flow field of the organ pipe cavitation nozzle is simulated in this research using the RNG k−ε, DES, and LES turbulence models. The LES model can more accurately predict the periodic shedding of a cavitating cloud, which is basically consistent with the jet morphology captured with a high−speed camera. The flow pattern, cavitating cloud evolution and shedding period of a cavitating jet are analyzed. The findings demonstrate that the LES model produces a cavitating effect inside the nozzle that is superior to those produced by the RNG k−ε and DES models. The vortex rings in the diffusion section are simulated using the LES model, which accelerates cavitation. The cavitating clouds of the organ pipe nozzle show periodic evolutions, with stages of generation, development, shedding and collapse. The periodic shedding of the cavitating clouds exhibits a similar pattern in the vorticities simulated using the LES model, and the vorticities display the small-scale structures where the cavitating bubbles collapse. This study can provide a reference for the simulation of a cavitating jet and the analysis of the cavitating mechanism.

The Effect of Cavitation Water Jet Shock as a Newly Technology on Micro-Forming Process

This article proposes a novel technology called water jet cavitation shock micro-forming to fabricate micro-features on 304 stainless steel foils with a thickness of 100µm, using a cavitation nozzle with an incident pressure of 8 to 20MPa. This study investigated the surface morphology of the formed part, the influence of incident pressure, target distance, and impact time on the forming depth, and analyzed the punching phenomenon of the formed components. The experimental results after the water jet cavitation shocking indicated that the surface morphology of the formed part of the 304 stainless foil sample had good quality and no conventional defects such as die scratches and cracks. Furthermore, when the incident pressure was 20MPa, the height of the uniform-shaped spherical cap exceeded 262µm. The forming depth increased with increasing incident pressure and impact time. Under an incident pressure of 20MPa, with the increase of target distance, the average depth of the formed part increased at first and then decreased. Finally, the analysis of the blanking phenomenon indicated that when the incident pressure increased to 30MPa, the workpiece was completely blanked. This is mainly because, under this incident pressure, the shockwave pressure generated by the collapse of the bubble deforms the workpiece beyond the stress limit of the material itself.

Numerical Simulation of Cavitation and FlashBoiling in GDI Nozzle and Spray

This work aims at using Computational Fluid Dynamics (CFD) method to establish a gasoline direct injection (GDI) engine nozzle and combustion chamber model to simulate cavitation and flash boiling phenomena and analyze how these phenomena affect the engine performance. FLUENT 15.0 is used to simulate the flow of fuel. The cavitation phenomenon in GDI nozzle was simulated comprehensively, and the influences of parameter values such as inlet pressure and outlet pressure on cavitation were studied in this work. The results show that high injection pressure can promote the occurrence of cavitation and high outlet pressure has an inhibitory effect on cavitation. However, the effect of cavitation on atomization cannot be seen intuitively only through the simulation of the internal nozzle. The two-dimensional inter nozzle model established in this work is a foundation for the establishment of external nozzle model. It can provide specific boundary conditions at nozzle outlet. In addition, a three-dimensional external nozzle model was established to simulate the flash boiling spray in the combustion chamber. Based on the mechanism, it can be found that flash boiling spray improves the atomization quality. After verifying the simulation results with relevant experiments, these models could bring great convenience to the study of cavitation and flash boiling with sufficient reliability in further study.

Numerical Simulation of Flow Field of Submerged Angular Cavitation Nozzle

A model of a submerged angular cavitation nozzle is established, which consists of a contraction part, parallel middle part, and expansion part. Based on the CFD technique, a numerical simulation of the flow field of the submerged cavitation nozzle is carried out, in which a multiphase mixture model, cavitation model, and renormalization group (RNG) k-ε turbulence model are applied. Considering the influence of mixture density on cavitation, the effects of the inlet contraction part, parallel middle part, and outlet expansion part on the velocity and vapor volume fraction are studied. The numerical simulation results show that the mixture density is essential in the cavitation jet. When the nozzle diameter d is fixed, the designed angular cavitation nozzle with contraction angle α = 13.5°, parallel middle part length Ld = 3d, expansion part length Le = 4d, and expansion angle β = 60° can effectively bring out cavitation. A cavitation cloud is produced near the rigid wall of the outlet expansion section and diffuses in a vortex ring shape. Optimizing the nozzle structure can improve the cavitation effect of the nozzle. The feasibility of this model is verified by relevant experimental data.

CAVITATION NOZZLES WITH EXPANSION CHAMBER

An expansion chamber for narrow part of cavitation nozzles is developed. Designs of cavitation nozzles with expansion chamber based on cylindrical nozzle and Venturi nozzle are proposed. The results of calculations of the fluid flow in the presented nozzles show the areas in nozzle, where cavitation is generated, their number, form and power. The plot of volume fraction of vapor phase shows the causes of an increase in the intensity of cavitation in new nozzles with expansion chamber. The main of them is that due to introduction of the expansion chamber, a little area of cavitation generation in the narrow part of cavitation nozzle turns to large one, that causes significant increase in cavitation intensity. The results of comparative experimental studies, which confirm the superiority of cavitation nozzles with the expansion chamber over the basic ones, show that cavitation nozzle with expansion chamber can provide 3 times higher intensity of cavitation, than basic cylindrical nozzle. Also, cavitation nozzle with expansion chamber on the basis of Venturi nozzle can provide 1.5 times higher cavitation intensity, than basic Venturi nozzle.

Estimation of cavitation erosion area in unsteady cavitating flows using a modified approach

Estimation of cavitation erosion area remains a challenging issue. Only an accurate estimation of the erosion-sensitive area can effectively reveal the various mechanisms of cavitation erosion. In this study, large eddy simulation is applied to simulate the unsteady cavitating flows, and an energy approach is developed to estimate cavitation erosion area. This approach is modified by taking into account hydrodynamic efficiency, which is deduced from the perspective of shock wave decays. The numerical estimation is then validated based on an axisymmetric nozzle cavitating flow. The numerical simulation results indicate that the modified approach can reasonably estimate the cavitation erosion area. In addition, various hydrodynamic cavitation erosion mechanisms are numerically analyzed based on the cavitating flow around a NACA0015 hydrofoil. The numerical simulation is able to reproduce the experimentally observed U-shaped cavitation structure. The interaction between cavitation and vortex has an important influence on the distribution of cavitation erosion. The areas in which the U-shaped cavitation pass may be in high erosion risk.

Relationships and Mechanisms of Sand Grain Promotion on Nozzle Cavitation Flow Evolution: A Numerical Simulation Investigation

Relationships and Mechanisms of Sand Grain Promotion on Nozzle Cavitation Flow Evolution: A Numerical Simulation Investigation

Generation, validation and application of dynamic load profiles in flow measurement using cavitating Herschel–Venturi nozzles

Today, utility meters for water are tested for measurement behavior at stable operating conditions at specified flow rates as part of the approval process. The measurement error that occurs during start and stop or when changing between flow rates may not be taken into account. In addition, there are new technologies whose measuring behavior under real-world conditions is only known to a limited extend. To take these facts into account, a new method has been developed and tested to determine the measurement behavior of water meters under dynamic load profiles as they occur in the real application. For this purpose, a test rig for flow rate measurement was extended by a cavitation nozzle apparatus and the generation of dynamic load profiles was validated. For the cavitation nozzles used, possible factors influencing the flow rate, such as temperature and purity of the water as well as the upstream pressure were investigated. Using different types of domestic water meters, the applicability of the dynamic test procedure was demonstrated and the measurement behavior of the meters was characterised.

INFLUENCE OF THE INLET PRESSURE ON IMPULSE CHARACTERISTICS OF ALUMINUM SAMPLES

In this work, the cavitation water jet technique was used to clean the inner walls of oil pipes after tertiary oil recovery. The surface morphology, depth of impinging pits, and corrosion resistance of aluminum samples after impingement with the cavitation water jet were examined using scanning electron microscopy (SEM), 3D microscopy, and an electrochemical workstation. When the inlet pressure was higher than 3[Formula: see text]MPa, the number of cavitation bubbles generated by the cavitation nozzle increased with an increase in inlet pressure. Moreover, the cleaning effect that the cavitation water jet had on the aluminum samples was higher than that of general water jet technology. There were no obvious changes to the surface of the aluminum samples when the inlet pressure was decreased to 13[Formula: see text]MPa. Meanwhile, the mass loss of aluminum samples also increased. However, the internal corrosion resistance of the pipe wall after impact was relatively low. These results indicate that the impinging efficiency of the cavitation water jet was obviously enhanced and the degree of damage to the oil pipe wall was low at an inlet pressure of 15[Formula: see text]MPa. The best target distance was 8–12[Formula: see text]mm, and at this point, the jet flushing effect was the best. Moreover, the jet velocity at the outlet cavity was 184[Formula: see text]m/s, and the jet strike area was 250[Formula: see text]mm2.

New Dimensionless Numbers Governing Cavitation in Diesel Multi-Hole Mini-Sac Nozzles and Sprays

New Dimensionless Numbers Governing Cavitation in Diesel Multi-Hole Mini-Sac Nozzles and Sprays

Nozzle Cavitation and Rock Erosion Experiments Reveal Insight into the Jet Drilling Process

AbstractAn in‐depth process analysis of water jetting, a promising cost‐effective drilling method for the exploration of geothermal reservoirs, is presented. The jetting process is analyzed under submerged and pressurized conditions by complementary high‐speed shadow imaging, particle image velocimetry, and rock erosion analysis. The shadowgraphy and velocimetry experiments show that nozzle cavitation dominates the process, and it can be described by a modified cavitation number. Rock erosion experiments show that cloud cavitation governs material erosion. Thus, control of cavitation is essential for the jetting process.

고온유체의 벤츄리노즐 공동현상 수치해석

Understanding cavitation dynamics considering thermodynamic effect is critical to handle specific cavitation phenomena such as high temperature fluid flow or cryogenic fluid flow. In this study, a numerical analysis has been performed to investigate a the Venturi nozzle cavitation characteristic at 5 different points; 4 0℃, 50℃, 65℃, 80℃ and 95℃. A compressible homogeneous mixture model is applied, which is based on a dual-time preconditioning method. The results show that the evolution of cavitation in the Venturi nozzle and its cyclic motion can be described by re-entrant jet behavior, which is formed at a moment when high stagnation pressure occurs at the end of the cavity. After the re-entrant jet cuts off the head of the leading part, cloud shedding cavitation detaches from the main body of the cavity and it starts a vortex motion. In addition, increasing fluid temperature from 50℃ to 80℃ makes thermal effects dominant, which suppress and interrupt further development of cavitation due to the decrease of the local vapor pressure as cavitation occurs. Nonetheless, the 95℃ case, which is almost close to the boiling point of water, induces a thick and long cavity due to its higher saturated vapor pressure value when compared to others.

The effect of the divergent-convergent GDI injector on inner flow and spray characteristics at high injection pressure

ABSTRACT The effects of Divergent-Convergent (D-C) nozzle parameters on the inner flow and spray characteristics of GDI (Gasoline Direct Injection) injector were studied under the condition of high injection pressure of 40 MPa. Homogeneous Relaxation Model (HRM) was used to explore the GDI orifice inner cavitation flow and nozzle exit flow parameters. A one-way coupled spray model was adopted to study the GDI spray behaviors. From these results, the cavitation density in the orifice decreases with the increase of the medium diameter ratio Km, while the discharge coefficient and the orifice exit velocity increases with the increase of Km. Moreover, the nozzle exit average velocity increases with the increase of Xm, and the nozzle exit average velocity with the Km of 1.5 is about 14.1% larger than that of the cylindrical nozzle. While the changing of the Xm has no effect on the nozzle exit average velocity for the same median diameter ratio. Additionally, the turbulent kinetic energy at the nozzle exit decreases with the increase of Km, especially the turbulent kinetic energy for the D-C nozzle with Km of 1.5 is about 17.1% smaller than that of the cylindrical nozzle. In addition, the D-C nozzle with Xm of 0.5 held the smallest turbulent kinetic energy. Also, the Sauter Mean Diameter (SMD) decreases with the decrease of Km at the initial injection stage. However, the spray SMD increases with the decrease of Km, and the SMD decreases with the increase of Xm at the late injection stage. Furthermore, the SMD of D-C nozzle is smaller than that of the cylindrical nozzle at the late injection stage.