High Jet Pressure Research Articles

Flow structures and cavitation in submerged waterjet at high jet pressure

Complexity of the submerged waterjet driven by high pressure resides in the jet itself and ambient water as well. To explore the traits of the high-pressure submerged waterjet, an experimental study is carried out at jet pressures of 13, 16 and 18MPa. The submerged waterjet flow is measured using particle image velocimetry in conjunction with seeded Rhodamine 6B fluorescence particles. Vorticity is calculated from velocity distribution. High-speed photography is utilized to capture the evolution of cavitation phenomenon near the nozzle. Pressure fluctuations excited in the water tank are acquired with miniature pressure transducers. At the three high jet pressures, submerged waterjet velocity attenuates remarkably along the streamwise direction, demonstrating substantial difference in comparison with low-pressure submerged waterjet. The semi-width of the waterjet stream increases downstream in a nearly linear manner. Pressure fluctuations in the water tank are featured by a wide frequency band within which low frequencies are most predominant. Meanwhile, relatively high frequencies are associated with cavitation evolution. Cavitation cloud development encompasses three distinct stages, namely cavitation cloud extending, cavitation cloud preserving and cavitation cloud shrinking. Of significance is the cavitation cloud profile, it is represented by disperse cavity elements at 13MPa. And the coherence of the cavitation cloud, as well as cavitation area fraction, is enhanced as jet pressure increases.

Effects of Processing Parameters on Massive Production of Graphene by Jet Cavitation.

The massive production of graphene by jet cavitation method with high productivity is demonstrated. Effects of the critical processing parameters on the product dispersions are studied systematically. Experimental results show that high yield of graphene flakes relies on appropriate initial concentration of graphite, high jet pressure, and long treating time. By processing a large batch (10 L) of graphite dispersion for 8 h under 20 MPa in the jet cavitation device, an exfoliation fraction of up to ~12 wt% was achieved. Based on statistical analysis of atomic force microscopy, the as-produced graphene flakes were proved to be highly exfoliated, while the distributions of flake thickness and area became narrower with the increase of treating time. Raman spectra confirm that few defects on the graphene basal planes were induced. In general, the presented approach shows advantages in comparison with peer liquid phase exfoliation methods and thus provides a new route in efficiently producing high-quality graphene in large scale.

Machining of Micro-Channels on Brittle Glass Using an Abrasive Slurry Jet

This paper presents a study of using an abrasive slurry jet for the machining of micro channels on brittle glasses. The machined surface morphology and channel dimensions are used to assess the technology. Surface morphology was found featuring with two types of wave patterns; one was along the channels with large wave lengths as a result of the jet deflection during the motion of nozzle, and the other was due to viscous flow that resulted in smooth surface eroded predominantly by ductile mode. The investigation showed that using higher jet pressure and higher particle concentration enables to create channels with higher depth, although these widened the channels and degraded the surface quality in some cases by inducing a larger number of pit fragments on the surface. With proper control of the operating parameters, this technology can be used for machining micro channels on brittle materials with high quality of surface finish.

Study on MQL in Point Grinding Process for Green Manufacturing

In point grinding process, the contact area of point grinding is much smaller than that of conventional cylindrical grinding under same conditions, so the grinding power and heat to measure is lower and the cooling condition is improved obviously. For green manufacturing, the point grinding process has the significance to reduce the consumption of grinding fluid and improve ground surface integrity and greenness. This study analyzes the geometric configuration of the contact area between wheel and workpiece in point grinding process, establishes the geometric and mathematic models of the contact area, and investigates the relations between the grinding parameters and the grinding power by the simulations. The MQL and semi-dry point grinding experiments are performed on the ground surface integrity. These investigations show that the MQL and semi-dry grinding can be achieved in point grinding process under less contact area and higher jet pressure condition for the high greenness demand.

Numerical investigation of the shock interaction effect on the lateral jet controlled missile

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. A three-dimensional Navier–Stokes computer code (AADL 3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body. Different jet flow conditions including jet pressures and jet Mach numbers, and the circumferential jet positions have been incorporated into the case studies. The missile surface is divided into four regions with respect to the center of gravity, and the normal force and moment distribution at each region are compared. The results show conspicuously different normal force and moment variations according to each parameter variation. From the detailed flow field analyses, it has been verified that most of the normal force loss and the pitching moment generation are taking place at the low-pressure region behind the jet nozzle. Furthermore, it is shown that the pitching moment can be efficiently reduced by the lateral thrust obtained through higher jet Mach number rather than high jet pressure. Thus, an angle of yaw is more effective for missile control by side jet than an angle of attack.

측 추력 제트가 미사일의 공력특성에 미치는 영향에 관한 연구 : Part I. 제트 유동특성 영향

측 추력(Lateral Jet)을 이용하여 자세를 제어하는 미사일 주위의 초음속 유동장 해석을 위하여 삼차원 Navier-Stokes 코드 (AADL3D)를 개발하고, 이를 이용한 수치해석 연구를 수행하였다. 분출 제트 압력, 분출 마하수 등을 포함하는 제트의 유동특성이 미사일에 미치는 수직력 및 피칭모멘트에 대한 영향을 알아보기 위한 사례연구를 수행하였으며, 공력 해석 결과 제트의 분출 압력과 분출 마하수 변화에 따른 서로 다른 수직력과 모멘트 변화 양상 및 그 원인을 확인할 수 있었다. 또한 대부분의 수직력 손실과 피칭모멘트 발생은 노즐 후방의 저압영역에 의한 것이며, 동일한 제트 추력일지라도 분출 마하수가 큰 경우가 분출 압력이 큰 경우보다 모멘트 발생 최소화에 유리함을 확인하였다. A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for different jet flow conditions including jet pressure and jet Mach number. The results show different behavior of normal force and moment variation according to jet pressure variation and jet Mach number variation. From the detailed flow field analyses, it is verified that most of the normal force loss and the pitching moment generation are taken place at the low-pressure region behind the jet nozzle. Furthermore, it is shown that the pitching moment can be efficiently reduced by obtaining the lateral thrust through higher jet Mach number rather than through high jet pressure.

Grouting pressure and damaged adjacent buildings. Part 1: Behaviour analysis

This paper studies how high-jet pressure improvement piles—such as the chemical churning pile (CCP), the jumbo special pattern (JSP) and the jumbo grouting pile (JGP) methods—protect adjacent buildings in excavations. If the grouting pressure did not control adequately for various soils at various NSPT numbers, the adjacent buildings would suffer secondary damage. By studying good relationships between grouting pressure and soil properties, knowledge of protecting adjacent buildings under excavations can be accumulated. It is recommended to use laser level surveyors to monitor the adjacent buildings when CCP (chemical churning pile), JSP and JGP high-jet pressure improvement piles are to be constructed. Cette étude analyse comment les pieux de réhabilitation par jet à haute pression, tels que les CCP, JSP et JGP, protègent les bâtiments voisins lors d'une excavation. Si le contrôle de la pression du jointoiement par coulis n'est pas approprié aux différents types de sols, aux différentes valeurs NSPT, cela peut entraîner des dégats secondaires pour les bâtiments voisins. A partir de statistiques établies par l'étude de plusieurs cas, nous établissons quelles sontles meilleures relations entre les propriétés du sol et la pression de la coulée de jointoiement, augementant ainsi les connaissances sur la protection des bâtiments voisins lors d'une excavation souterraine. Notre étude propose également, lors de la construction de pieux de réhabilitation par jet à haute pression, de surveiller les bâtiments voisins au moyen d'appareils lasers de contrôle de niveau, afin de maintenir la sécurité de ces bâtiments.

Thermal Energy Distributions in the Workpiece During Cutting With an Abrasive Waterjet

Distribution of thermal energy in the workpiece during cutting with an abrasive waterjet (AWJ) was studied experimentally. Detailed time-temperature measurements in the workpiece as a function of jet pressure, traverse rate, workpiece material, and workpiece orientation were performed. It is shown that maximum temperatures occur at the immediate vicinity of the cutting interface and sharply decay thereafter with increasing distance from the interface. A higher jet pressure and/or a lower traverse speed results in higher temperatures in the workpiece. A material with higher thermal conductivity experiences higher temperatures during the cut. Within the workpiece, higher temperatures occur at inner zones where the jet-induced cooling effects are minimum.

Liver resection using a water jet.

The water-jet method has been used during hepatic resection. The instrument cuts the hepatic tissue with the high pressure of the fine water flow, while the exposed elastic intrahepatic vessels are spared injury. A comparative study on the water-jet method with the previously employed conventional methods was undertaken. Hepatic resections were performed on 35 patients using the water-jet method. Cirrhosis of the liver was associated with 10 of the 24 patients with hepatocellular carcinoma. An ordinary saline solution was used as the jet, which was projected at a pressure of between 12 kg/cm2 and 20 kg/cm2 through a 0.15/mm-diameter nozzle. A higher jet pressure was needed to cut the fibrotic hepatic parenchyma. In the case of normal liver, the intrahepatic vessels of more than 0.2 mm were well preserved. In most of the cases, the loss of blood when cutting the hepatic parenchyma can be easily reduced with a jet pressure of 15-16 kg/cm2, thus preserving the fine vessels more than 0.2 mm in diameter without injury. When the same pressure was applied in the cutting of a cirrhotic liver, it took much longer time compared to that of a non-cirrhotic normal liver parenchyma. The cut surface was smooth compared to that after using CUSA, although its disadvantages lie in the formation of air bubbles, which obscure the operative field. The controlled projection of a jet of water under optimal pressure may ensure a safe hepatic resection of both normal and cirrhotic livers. Furthermore, because of its uncomplicated form, a wide range of applications can be expected, while the lower cost will also expedite its large-scale use for economic reasons.

難削材の研削加工の改善に関する研究 (第2報)

With grinding fluid is a high jet pressure, heat quantity that its flow carry away increases. Therefore, to get fundamental information of practical development on grinding operation for difficult material to be cut by jet infusion of grinding fluids, effect of jet pressure is discussed by measurement values of grinding force, grinding temperature, residual stress, loading and concaveness of ground surface. The main results are as follows;(1) The jet infusion of tangential direction of grinding point is most effective for the reduction of grinding temperature, residual stress and concaveness of ground surface.(2) For improvement of thermal dominating factors in grinding accuracies, the dilution water of No. 1-No. 4 grinding fluids are more effective than group of #60 spindle oil.(3) The prevention of loading of grinding wheel becomes effective as high jet pressure. For example, the jet infusion in high pressure takes a way the loading of adhesive type.(4) The grinding temperature and conduction zone of it were dominated by a changes in the jet infusion pressure Pj.