Cavitating Jet Research Articles

Experimental study on a designed jet cavitation device for producing two-dimensional nanosheets

In this study, a jet cavitation device aimed at producing two-dimensional nanosheets was designed. The effects of cavitation generator type and jet pressure on the cavitation inception and intensity were examined by monitoring the changes of sound pressure level (ΔSPL). As such, the optimized cavitation generator with the best cavitation capability under the same ambient condition was determined. Further, BN and MoS2, two kinds of layered materials, were exfoliated into individual flakes in aqueous solutions by this jet cavitation device. By investigating the morphology of these exfoliated flakes via scanning electron microscopy and transmission electron microscope, it was found that these pristine materials were mostly exfoliated into two-dimensional nanosheets, among which even monolayers were generally presented. This exfoliation process happened mainly due to the cavitation-induced intensive tensile stress acting on the layered materials. As graphene has been produced by this device successfully, it is anticipated that this jet cavitation device is suitable for producing other various two-dimensional nanosheets.

Study on a New High-Efficiency Treatment Method of Printing and Dyeing Wastewater

The large quantity of dyeing and printing wastewater, which contains high organics which can be hardly decomposed, is one of the main sources of water pollution. Based on summarizing the existing problems of traditional processing methods, the technology of cavitation jet and impinging streams were organically combined, which has great potential in wastewater treatment field, as a new method for degrading printing and dyeing wastewater, and then the “cavitation impinging streams (CIS)” concept was proposed, in which the superior features in wastewater degradation with CIS was expounded, and the problems to be further studied were pointed out.

Experimental Study on Rock Breaking with Impacting Water Jet by Modulation of Chaos

The experiment focused on the contrast with rock breaking effect of impacting water jet by modulation of chaos and common cavitation jet. Investigated the influences of various water jet parameters and conditions on rock breaking, such as standoff distance, pump pressure, transverse speed and erosion time and the mass loss and erosion depth were measured in the experiment. The results show that the impacting water jet by modulation of chaos can efficiently use the energy of water jet and increase ability in rock-breaking, which will have a wide application prospect in high pressure water jet technology field.

Investigation of Cavitating Jet Effect on Bitumen Separation from Oil Sands

The effect of a submerged cavitating jet on as-mined oil sands is investigated in order to assess the potential of this new technological approach to bitumen extraction at low temperatures. A series of laboratory experiments have been performed using a custom-made experimental apparatus that allowed ablation measurements of oil sands samples and provided information regarding the volume of the extracted bitumen, the remaining volume of cleaned sand, the effects of the water temperature, and the time of exposure of the sample to a cavitating jet. A comparison of the results for cavitating and noncavitating jets is provided.

Investigation of the Effect of Slurry Density on a Bitumen Separation Process Based on Cavitating Jets

The effect of slurry density on a bitumen separation process based on a new cavitating jet technology at low temperatures is investigated. The experiments were conducted in a custom-made apparatus. It is shown that the cavitation effect does take place at increased slurry densities, and thus its application in industry will lead to increased efficiency of bitumen extraction. A comparison of the results for cavitating and noncavitating jets is provided to validate the effect of cavitation.

The effect of scanning pitch of nozzle for a cavitating jet during overlapping peening treatment

The objective of this paper is to optimize the pitch at which the nozzle of a cavitating jet is scanned during peening. The evaluations of an effect of the pitch on overlapping treatment are done, firstly theoretically, by estimating the aggressive intensity of the jet based on a Gaussian distribution in order to uniformly and effectively treat the surface in applications such as cavitation peening and cleaning. Experimentally, cavitation peening was conducted with the nozzle scanned at various pitches. Striped patterns, due to the non-uniform treatment, were formed in aluminum when pitches of 6, 8, 10 or 12mm were used, whereas with pitches of 2 and 4mm the patterns were uniform. The compressive residual stress introduced into type 316L stainless steel by cavitation peening was approximately 380 and 400MPa for pitches of 2 and 4mm, respectively. From the viewpoint of not only the uniformity but also effective and efficient treatment, the optimum pitch for scanning was determined to be 4mm, since this requires half the number of scans compared to 2mm.

Suppression of hydrogen-assisted fatigue crack growth in austenitic stainless steel by cavitation peening

In this paper we demonstrate the suppression of hydrogen-assisted fatigue crack growth in type 316L austenitic stainless steel by cavitation peening employing a cavitating jet in air. Plate bending fatigue tests on pre-cracked samples were conducted after cathodic hydrogen charging with and without cavitation peening. Without cavitation peening, the hydrogen effect on the crack growth behavior at low applied stress was clearly demonstrated compared with high applied stress in the fatigue test. The coalescence of sub-cracks and the main crack propagating from the pre-crack were observed in the hydrogen charged specimen. This phenomenon significantly accelerated the crack growth. This unexpected fracture was suppressed by introducing compressive residual stress by cavitation peening regardless of the length of processing time. In addition, lengthier treatment reduced the crack growth rate of the hydrogen charged specimen by 75% compared to an untreated one.

EXPERIMENTAL STUDY ON THE EFFECTS OF HYDRAULIC CONFINING PRESSURE ON IMPACTING CHARACTERISTICS OF JETS

Original Manuscript Submitted: 4/6/2012; Final Draft Received: 6/15/2012 The high hydraulic confining pressure exhibited in oil-well downholes and deep water conditions affects jet dynamic characteristics remarkably. A set of devices and equipment were developed to study the influence of confining pressure on jet impact pressure and rock-breaking efficiency. The three most popular jet types—a conical water jet, a cavitating jet, and an abrasive jet—were studied with a maximum nozzle pressure drop of 25.0 MPa and maximum confining pressure of 20.0 MPa. Results clearly reveal the close relationship among confining pressure and jet impact pressure and rock-breaking efficiency. The axial jet impact pressure and rock removal volume decrease while as confining pressure increases, and the decreasing curve becomes flattened at a certain point. Under the same conditions, the rock-breaking efficiency of the cavitating nozzle jet is higher than the conical nozzle jet, and cavitating erosion and pressure fluctuation are the important factors affecting jet rock-breaking efficiency. Furthermore, under confining pressure conditions, pure water jets have an optimal standoff distance about 3 to 5 times that of the nozzle outlet diameter, at which the highest rock removal volume is achieved. According to the study, a drop of jet impact pressure with growth of confining pressure may be the main reason for the decreasing rock-breaking capability. The study could be used as a reference for setting and optimizing jet application conditions, and also could be adopted for developing working parameter selections as well as guiding the nozzle structure designs.

G040032 メカノケミカルキャビテーション噴流による耐食性向上に関する研究

G040032 メカノケミカルキャビテーション噴流による耐食性向上に関する研究

OS0825 き裂を有する材料に対するウォータージェットピーニングの残留応力低減効果

Water jet peening is a method using cavitation jet peening to introduce compressive residual stress into target surface, which has already been applied in nuclear power plants as a measure against stress corrosion cracking. In this report, we confirmed the effects of the water jet peening on cracked surface. Visual inspection after water jet peening might not be available because crack is closed, in which case ultrasonic inspection will still work. Reduction of tensile residual stress around cracks is confirmed. In addition, we found that crack growth rate decreased after water jet peening in shallow stress corrosion cracking.

Measurements of the stagnation pressure in the center of a cavitating jet

The stagnation pressure at a certain distance from the nozzle is important for the erosion/ cutting capacity of a submerged jet in dredging. The decay of the stagnation pressure with jet distance is well known in the case of non-cavitating jets. It is also known that cavitation causes the rate of decay to decrease. Under conditions of cavitation, a cone of bubbles forms around the jet, which decreases the momentum exchange between the jet and the ambient water and the associated entrainment. Despite the amount of research on cavitating jets, the literature does not provide a description for the entrainment in the case of a cavitating jet. Also, a useful description of the stagnation pressure decay of a cavitating jet is missing. To fill this lacuna, we carried out jet tests at various ambient pressures in both fresh and saline water. We present and analyse the results in this paper.

Disinfection of gram-negative and gram-positive bacteria using D ynaJ ets® hydrodynamic cavitating jets

Cavitating jet technologies (D ynaJ ets®) were investigated as a means of disinfection of gram-negative Escherichia coli, Klebsiella pneumoniae, Pseudomonas syringae, and Pseudomonas aeruginosa, and gram-positive Bacillus subtilis. The hydrodynamic cavitating jets were found to be very effective in reducing the concentrations of all of these species. In general, the observed rates of disinfection of gram-negative species were higher than for gram-positive species. However, different gram-negative species also showed significant differences ( P. syringae 6-log 10 reduction, P. aeruginosa 2-log 10 reduction) under the same conditions. Disinfection of E. coli repeatedly showed five orders of magnitude reduction in concentration within 45–60-min at low nozzle pressure (2.1 bar). Optimization of nozzle design and operating pressures increased disinfection rates per input energy by several orders of magnitude. The power efficiencies of the hydrodynamic cavitating jets were found to be 10–100 times greater than comparable ultrasonic systems.

Cavitation erosion and jet impingement erosion mechanism of cold sprayed Ni–Al2O3 coating

Abstract A composite coating was deposited on Inconel 600 substrate by cold spray method using pure Ni powder (60 wt.%) blended with α-Al2O3 (40 wt.%) as feedstock. It is expected to be applied to repair the bellows eroded by the liquid droplet erosion (LDE). Microstructure of the coating was observed using optical microscope (OM) and scanning electron microscopy (SEM). Microhardness of the coating was determined by Vickers hardness tester. Cavitation erosion (CE) experiments were carried out in the distilled water. Jet impingement erosion (JIE) experiments were performed in slurry containing 1 wt.% quartz particle with the flow velocity of 15 m/s at impingement angles of 30°, 60° and 90°, respectively. Cumulative mass loss vs. testing time was used to evaluate the erosion rate of the coating. The erosion mechanism was analyzed by OM, SEM, X-ray diffraction (XRD) and the microhardness measurement. The results show that the composite coating has compact microstructure and relatively high hardness. The resistance to CE of the coating is not as good as that of Inconel 600 substrate due to the weak bonds of the Al2O3 particles. However, the results of the JIE test indicate that the slurry erosion resistance of the coating is better than that of Inconel 600 at the impact angles of 30° and 60°, but not at the normal impact angle.

Application Research on Low-Pressure Pulse and Cavitation Jet Compound Drilling Technology

In the low-pressure pulse and cavitation jet compound drilling technology, pulse low-pressure and cavitation jet generator is installed on bit, water jet modulated by generator can generate pulse low-pressure, which will alternate rock mechanics, decrease rock breaking strength, increase rock-breaking efficiency. And cavitation jet generated can increase hydraulic power downhole. The results show that low-pressure pulse and cavitation jet generator has been run well from 5349m to 6162m for 129.36h-136.63h in TK1090 well, increasing drilling speed 40.6%～85.1%. The low-pressure pulse and cavitation jet compound drilling technology can increase drill speed and be deployment in deep well drilling.

Enhancing the Aggressive Intensity of a Cavitating Jet by Means of the Nozzle Outlet Geometry

In order to enhance the aggressive intensity of a cavitating jet for practical applications, the effect of the geometry of the nozzle through which the jet is driven on the aggressive intensity was investigated. The nozzle under test was cylindrical and consisted of a plate and a cap with a hole bored through it. The aggressive intensity of the jet was estimated by the erosion suffered by pure aluminum test specimens. The parameters varied were the bore diameter, D, and length, L, the standoff distance, the nozzle throat diameter, d, and the upstream and downstream pressures of the nozzle. The mass loss at the optimum standoff distance, where the mass loss was at a relative maximum, was found for each bore diameter and length, and then the optimum bore diameter and length were obtained. The optimum ratio of d : D : L was shown to be 1 : 8 : 8, and this was the optimum for both d =1 mm and d =2 mm. It was also the optimum ratio for upstream pressures of 15 MPa and 30 MPa, and downstream pressures of 0.1 MPa and 0.42 MPa.

Morphology and structure of mono- and few-layer graphene produced by jet cavitation

We prepared mono- and few-layer graphene with micrometer-sized dimensions in aqueous solution by a jet cavitation method starting from common crystal graphite, which is totally green, facile, low-cost, and laborsaving. The graphene yield by our method is estimated as ∼4 wt. % by statistical analysis. Diverse microscopy is used to characterize the morphology, microstructure, and near-edge fine structure of the prepared nanosheets. It is found that partial folding allows realization of rotational stacking fault in otherwise perfect samples. The folded graphene with Morié patterns could be ideal specimens for experimentally probing band structure and electronic properties of graphene with different stacking styles.

Preparation of graphene by jet cavitation

Despite its bright prospects, graphene faces challenges including issues concerningmass production. Here we present a totally green approach whereby commoncrystal graphite can be exfoliated into graphene sheets in aqueous solution byjet cavitation. This is possible mainly because the tensile stress caused bygraphite–solution interfacial reflection of compressive waves acts an intensive‘suction disk’ on the graphite flakes. We confirm the presence of graphene sheetsby diverse characterizations. The graphene yield by our method is estimated as ∼ 4 wt%, which could potentially be improved by further processing. The method, ofa mechanical nature, is powerful compared to the traditional low-throughputmicromechanical cleavage. Our work here illustrates jet cavitation as a facile, low cost,timesaving and laborsaving route, which can potentially be scaled up to mass production ofgraphene.

An Experimental Study of the Nanoparticle Colloid Hydrodynamic Cavitation Jet Polishing Performance under Different Nozzle Designs

Nanoparticle colloid hydrodynamic cavitation jet polishing (HCJP) is a super-smooth machining technology. This technology utilizes the interface reaction to remove material from the workpiece and uses cavitation effect to improve the processing efficiency. In this paper, the prototype equipment of HCJP is researched. Based on the prototype equipment, the processing experiments of pulsed jet nozzle, swirling jet nozzle and common cone-shaped nozzle have been done and the results of the experiments are compared with each other. The experiment results indicate that the roughness of the surfaces polished by three nozzles has remarkably decreased. The material removal rate of pulsed jet nozzle is the highest among the three types of nozzles. The material removal rate of the swirling jet nozzle is not improved obviously compared with the common cone-shaped nozzle. The processing experiment of monocrystalline silicon by the pulsed jet nozzle has been done and the roughness of processed surface is Ra 0.475 nm.

Modification of Microstrucure and Residual Stress on Friction Welding Surface of Titanium Alloy by Water-Jet Cavitation Peening

Water jet cavitation peening is applied to improve the strength and mechanical properties of the friction-welded joints of titanium alloys. Scanning electron microscopy observations of the microstructure of the welded joints and welded area before/after water jet cavitation peening confirm slip dislocation at the microstructure near the surface of the specimens. The residual stress on the surface of the welded joint is measured by X-ray diffraction. The results indicate the effect of peening time on the strength of compressive residual stress.

Bubble proliferation in the cavitation field of a shock wave lithotripter

Lithotripter shock waves (SWs) generated in non-degassed water at 0.5 and 2 Hz pulse repetition frequency (PRF) were characterized using a fiber-optic hydrophone. High-speed imaging captured the inertial growth-collapse-rebound cycle of cavitation bubbles, and continuous recording with a 60 fps camcorder was used to track bubble proliferation over successive SWs. Microbubbles that seeded the generation of bubble clouds formed by the breakup of cavitation jets and by bubble collapse following rebound. Microbubbles that persisted long enough served as cavitation nuclei for subsequent SWs, as such bubble clouds were enhanced at fast PRF. Visual tracking suggests that bubble clouds can originate from single bubbles.