scholarly journals Effect of Nozzle Outlet Shape on Cavitation Behavior of Submerged High-Pressure Jet

Machines ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 4
Author(s):  
Gaowei Wang ◽  
Yongfei Yang ◽  
Chuan Wang ◽  
Weidong Shi ◽  
Wei Li ◽  
...  
Keyword(s):  
High Pressure ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Small Scale ◽  
High Speed Photography ◽  
Nozzle Outlet ◽  
Time Frequency ◽  
Cavitation Phenomenon ◽  
Cavitation Behavior ◽  
Organ Pipe

A submerged high-pressure water jet is usually accompanied by severe cavitation phenomenon. An organ pipe nozzle can greatly improve the cavitation performance of the jet, making use of the self-excited oscillation of the flow. In order to study the effect of organ pipe nozzles of different nozzle outlet shapes on cavitation behavior of submerged high-pressure jet, in this paper we build a high-pressure cavitation jet experiment system and carried out a high-speed photography experiment to study cavitation cloud characteristics of a high-pressure submerged jet. Two organ pipe nozzles with and without a whistle were compared. The dynamic characteristics of the cavitation cloud was extracted through the POD method, it was found that the result effectively reflect the dynamic characteristics of the cavitation jet. The reconstruction coefficients of mode-1 obtained by the POD can better reflect the periodic time-frequency characteristics of cavitation development. The effect of the nozzle outlet shape on the cavitation behavior of organ pipe nozzle was analyzed based on unsteady numerical simulation, and it was found that the jet generated by the nozzle with a divergent whistle had a larger vorticity in the shear layer near the outlet. Further, stronger small-scale vortex and much severe cavitation occurred from the nozzle with a divergent whistle.

Flow Visualization Study of Jet and Bucket Interactions in Traditional and Hooped Pelton Runner

2019 ◽  
Author(s):  
Gaurangkumar Chaudhari ◽  
Salim Channiwala ◽  
Samip Shah ◽  
Digvijay Kulshreshtha
Keyword(s):  
Flow Visualization ◽  
Flow Pattern ◽  
High Speed ◽  
Early Stage ◽  
Small Scale ◽  
High Speed Photography ◽  
Pelton Turbine ◽  
Single Jet ◽  
Absolute Frame ◽  
First Time

Abstract This paper aims to study the flow pattern in and around a bucket of a Traditional and a Hooped Pelton runner at single injector operation and illustrates different stages of jet interaction. High speed photography is used to study the flow pattern, keeping the camera in different positions relative to the jet and to the bucket. It is concluded from the results that the flow visualization study, provides exceptional observations with an absolute frame of reference to mark the bucket duty period of a single-jet Pelton runner. The small scale models display erosion damages at the bucket lips, this indicated that the high pressure occur in the early stage of interaction. This fact is substantiated by the present flow visualization studies for the first time. The uncertainty of the free surface outflow within the Pelton turbine bucket establishes good documentation. The results are helpful to know the interaction between the jet and bucket of Pelton turbine.

Submerged Pressure Vessel Testing Hazards

2012 ◽  
Author(s):  
John Montoya ◽  
Donald Ketchum ◽  
Matthew Edel
Keyword(s):  
High Pressure ◽  
Pressure Vessel ◽  
High Speed ◽  
Pressure Vessels ◽  
High Speed Photography ◽  
Gas Release ◽  
Test Program ◽  
Projectile Motion ◽  
Leak Testing ◽  
Test Failure

It is common practice to proof test high pressure vessels prior to their use in the field. One technique for leak testing these vessels is submersion in water. A test failure at high pneumatic pressure and can pose several hazards to nearby personnel, such as projectile launch and blast loads. Submerged underwater testing can provide some level of protection from these hazards. However, it is largely unknown how much water cover is needed to prevent a projectile from escaping. The purpose of this test program was to record the mitigating effects of water on hazards caused by a sudden pressure vessel failure. The test program entails submerging a pressure vessel underwater inside a tank. The vessel is then pressurized to failure, releasing a blast wave and launching a projectile. The event is recorded using high speed photography which is used to observe the effects of the gas release and the projectile motion. A discussion of the test events and associated physics is provided.

scholarly journals Response of High-Pressure Micro Water Jets to Static and Dynamic Nonuniform Electric Fields

2018 ◽  
Vol 6 (2) ◽  
Author(s):  
Yi Shi ◽  
Jian Cao ◽  
Kornel F. Ehmann
Keyword(s):  
High Pressure ◽  
Electric Fields ◽  
High Speed ◽  
Water Jet ◽  
Dynamic Responses ◽  
Order System ◽  
Loop Control ◽  
Time Frequency ◽  
Water Jets ◽  
The Stability

The manipulation of the trajectory of high-pressure micro water jets has the potential to greatly improve the accuracy of water jet related manufacturing processes. An experimental study was conducted to understand the basic static and dynamic responses of high-pressure micro water jet systems in the presence of nonuniform electric fields. A single electrode was employed to create a nonuniform electric field to deflect a high-pressure micro water jet toward the electrode by the dielectrophoretic force generated. The water jet's motions were precisely recorded by a high-speed camera with a 20× magnification and the videos postprocessed by a LabVIEW image processing program to acquire the deflections. The experiments revealed the fundamental relationships between three experimental parameters, i.e., voltage, pressure, and the distance between the water jet and the electrode and the deflection of the water jet in both nonuniform static and dynamic electric fields. In the latter case, electric signals at different frequencies were employed to experimentally investigate the jet's dynamic response, such as response time, frequency, and the stability of the water jet's motion. A first-order system model was proposed to approximate the jet's response to dynamic input signals. The work can serve as the basis for the development of closed-loop control systems for manipulating the trajectory of high-pressure micro water jets.

Investigation on the Motion States of the Hammers while Hammer Mill Steady Running by High-Speed Photography

2010 ◽  
Vol 42 ◽  
pp. 317-321
Author(s):  
Bao Liu ◽  
Dong Xing Zhang ◽  
Li Zong
Keyword(s):  
Wear Mechanism ◽  
Dynamic Characteristics ◽  
High Speed ◽  
High Speed Photography ◽  
Hammer Mill ◽  
Static Deflection ◽  
Comparison Analysis ◽  
Actual Motion

Actual motion states of the hammers while hammer mill steady running is an important analysis basis for the dynamic characteristics of the hammer mill rotor and the wear mechanism between hammers and hammer pivots. To investigation the actual motion states of hammers, a high-speed photography was used in this paper to record the instantaneous states of the hammers. And comparison analysis on the pictures recorded at three different working speeds was made, the results showed that, for each hammer on the hammer mill, there exists random static deflection phenomenon; and for all hammers, there exist chaos phenomena with relative rest positions in range of a certain angle.

scholarly journals Effect of Specimen Placement on Model Rock Blasting

2021 ◽  
Author(s):  
Zong-Xian Zhang ◽  
Li Yuan Chi ◽  
Qingbin Zhang
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Rock Specimen ◽  
Base Material ◽  
Scale Model ◽  
Small Scale ◽  
High Speed Photography ◽  
Rock Blasting ◽  
Ground Material ◽  
Very High

AbstractSmall-scale model blasting plays an important role in understanding mechanism of rock fragmentation by blasting and improving blast technology in rock and mining engineering. Because a specimen (or model) often needs to be placed on either a ground or another material in model blasting, an additional interface appears between the specimen and the ground (or material), compared with an engineering blast that does not have such an interface. In this paper, four model blasts with high-speed photography were presented. The results showed that: (1) as the impedance of a rock specimen was smaller than that of the ground material, the specimen was thrown up and a certain amount of kinetic energy was brought with such a bounce. Thus, this placement should be avoided in model blasts. (2) As a rock specimen was placed on three blocks of the same type of rock as the specimen the specimen was not bounced up during blasting. Correspondingly, no kinetic energy was induced by specimen bounce. Therefore, this placement is recommended for model blasting. If very high specific charge must be used in model blasting, the above-recommended method will not work well due to possible breakage of the base material during blasting. In this case, the rock specimen can be placed on a material with smaller impedance than that of the rock specimen so that specimen bounce can be reduced. Accordingly, such a possible specimen bounce should be estimated by stress wave analysis.

scholarly journals Experimental Study on Submerged High-Pressure Jet and Parameter Optimization for Cavitation Peening

Mechanika ◽  
2020 ◽  
Vol 26 (4) ◽  
pp. 346-353
Author(s):  
Yongfei YANG ◽  
Wei LI ◽  
Weidong SHI ◽  
Chuan WANG ◽  
Wenquan ZHANG
Keyword(s):  
High Pressure ◽  
High Speed ◽  
Surface Profile ◽  
304 Stainless Steel ◽  
Nozzle Geometry ◽  
High Speed Photography ◽  
Sem Images ◽  
Before And After ◽  
The Impact ◽  
Divergent Angle

To increase the performance of high pressure submerged cavitation jet that has been used for cavitation peening, the effect of stand-off distance and the nozzle geometry on the impact capacity is investigated and optimized. High speed photography of the cavitation bubble clouds taken to reveal the unsteady characteristics of the cavitating jet. The impact ability of the jet with different nozzles and standoff distance is tested using Al 1060 at first, and the optimized jet is used then for cavitation peening on 304 stainless steel. The surface profile as well as the grain structures before and after peening using different nozzles are observed from SEM images. It is found that, the divergent angle of the nozzle has a great effect on the impact capability of the submerged high-pressure jet, which is important for improving the peening efficiency. In the nozzles with divergent angle 40°, 60° and 80°, the 60° nozzle shows the best performance. After peening, grain cells under the metal surface are changed and a twin layer is formed. The current research reveals the transient characteristics of the submerged cavitation jet and main factors that affect its impact rate, which provides guide for the nozzle design and application for the high-pressure cavitation jet peening.

scholarly journals Numerical Investigation of a High-Pressure Submerged Jet Using a Cavitation Model Considering Effects of Shear Stress

Processes ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 541 ◽  
Author(s):  
Yongfei Yang ◽  
Wei Li ◽  
Weidong Shi ◽  
Wenquan Zhang ◽  
Mahmoud A. El-Emam
Keyword(s):  
High Pressure ◽  
Shear Stress ◽  
High Speed ◽  
Cfd Simulation ◽  
Experimental Result ◽  
High Speed Photography ◽  
Cavitation Model ◽  
Convergent Nozzle ◽  
Actual Length ◽  
Submerged Jet

In the current research, a high-pressure submerged cavitation jet is investigated numerically. A cavitation model is created considering the effect of shear stress on cavitation formation. As such, this model is developed to predict the cavitation jet, and then the numerical results are validated by high-speed photography experiment. The turbulence viscosity of the renormalization group (RNG) k-ε turbulence model is used to provide a flow field for the cavitation model. Furthermore, this model is modified using a filter-based density correction model (FBDCM). The characteristics of the convergent-divergent cavitation nozzle are investigated in detail using the current CFD simulation method. It is found that shear stress plays an important role in the cavitation formation in the high-pressure submerged jet. In the result predicted by the Zwart-Gerber-Belamri (ZGB) cavitation model, where critical static pressure is used for the threshold of cavitation inception, the cavitation bubble only appears at the nozzle outlet and the length of the cavity is much shorter than the actual length captured by the high-speed photography experiment. When the shear stress term is added to the critical pressure, the length of the predicted cavity is close to the experimental result and three phenomena of the jet are captured, namely, growth, shedding, and collapsing, which agrees well with the experimental high-speed image. According to the orthogonal analysis based on the simulation result, when the jet power is unchanged, the main geometry parameter of the divergent-convergent nozzle that affects the jet performance is the divergent angle. For the nozzle with three different divergent angles of 40°, 60°, and 80°, the one with the medium angle generates the most intensive cavitation cloud, while the small one shows the weakest cavitation performance. The obtained simulation result is confirmed by cavitation erosion tests of the Al1060 plate using these three nozzles.

Axial Rupture in Underwater Pipelines

1990 ◽  
Vol 112 (2) ◽  
pp. 151-156 ◽  
Author(s):  
K. Crentsil ◽  
E. G. Hauptmann ◽  
P. G. Hill
Keyword(s):  
High Speed ◽  
Axial Strain ◽  
Crack Opening ◽  
Water Environment ◽  
Inertial Mass ◽  
Mass Effect ◽  
Small Scale ◽  
High Speed Photography ◽  
Surrounding Water ◽  
External Water

The propagation of axial cracks in underwater pipelines was investigated by means of small-scale pipe experiments. The purpose of the experiments was to determine the effect of external water environment on crack opening characteristics. The development of the axial rupture was recorded by high-speed photography; measurements were made of the internal depressurization transient and the axial strain field. The measured depressurization histories agreed with the predictions of a one-dimensional transient fluid flow code. Results presented for underwater and in-air tests show that the external water environment produces a slower crack and a smaller crack opening area. A steady-state energy balance analysis was performed to investigate the various energy dissipation mechanisms present during pipe rupture. This analysis confirmed that the added inertial mass effect of the surrounding water may account for the reduction in crack speed and opening area.

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