scholarly journals Influence of External Jet on Hydraulic Performance and Flow Field Characteristics of Water Jet Propulsion Pump Device

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Jinxin Wu ◽  
Li Cheng ◽  
Can Luo ◽  
Chuan Wang
Keyword(s):  
Flow Field ◽  
Axial Force ◽  
Water Body ◽  
Jet Flow ◽  
Hydraulic Performance ◽  
Water Jet ◽  
Jet Propulsion ◽  
Wide Range ◽  
Depth Analysis ◽  
Flow Field Characteristics

Water jet propulsion technology has broad application prospects in the field of ships, and water jet technology is a kind of high and new technology that is booming and has a wide range of applications. However, there are a few studies on the effect of the external jet on the performance of the water jet propulsion pump, and it is urgent to carry out this research. In this paper, the standard k-ε turbulence model is used to carry out the numerical simulation study of the influence of the external jet on the hydraulic performance and flow field characteristics of the water jet propulsion pump device. This paper discusses the selection of calculation models, the division of grids and the setting of turbulence models, and an in-depth analysis of the calculation results. The research results show that when a high-speed water jet enters a moving water body, it will cause turbulence in the moving water body. With the increase of jet flow, the turbulence phenomenon will be improved. The average velocity of the outlet section of the nozzle is consistent with the change of the total pressure. The average vortex gradually decreases, the turbulent kinetic energy changes little, the turbulence dissipation first decreases and then increases, and the nozzle axial force changes more and more. The axial force and thrust of the device will obviously increase when the two water streams merge and spray, and they will increase with the increase of the jet flow rate. By revealing the influence mechanism of the external jet on the water jet propulsion pump device, it can provide a theoretical basis and guiding direction for further optimizing the hydraulic performance of the entire device.

Numerical Tests on the Effect Factors of the Last Stage Blade for Low Pressure Exhaust Hood Simulation

2017 ◽  
Author(s):  
Liu Meng ◽  
Chen Yang ◽  
Zhong Zhuhai ◽  
Zhang Xiaodan ◽  
Deng Guoliang ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Flow Field ◽  
Jet Flow ◽  
Low Pressure ◽  
Exhaust Hood ◽  
Effect Factors ◽  
Numerical Tests ◽  
Wide Range ◽  
Last Stage ◽  
Inlet Boundary Condition

Kinetic energy recovery is a key objective for low pressure exhaust hood design and optimization. Numerical simulation of the exhaust hood helps the engineers to explore and confirm the causes of the loss in the hood. Many studies have suggested that it is necessary for the simulation to include the last stage blade to get a realistic assessment. For the sole exhaust hood study, the inlet boundary condition is hard to set precisely like the downstream flow of the last stage blade. And the studies have also shown that the performances generated from the simulations may vary evidently between the sole exhaust hood and exhaust hood with last stage blade. It is obvious that the blade influences the exhaust hood, but the exact effect factors of the blade and the way they work are not thoroughly discussed. This paper has conducted many numerical tests to audit the influence of the common effect factors of the last stage blade. The internal flow field of the exhaust hood was numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions based on the ANSYS-CFX. In the first part of the paper, the tests are conducted by changing each effect factor of the inlet boundary condition for sole exhaust hood studies. These factors include the mass flow flux, the angle of the exit flow of the last stage, both the circumferential and the radial ones, and the speed and position of the jet-flow downstream of the seal over the shroud of the bucket. The tests show that each factor has its own distinctive style and extent for influence. Some of them may maximize the performance at some certain point, and some may deteriorate the performance rapidly beyond a threshold. And some factors may change the performance insignificantly within a wide range. However, these influences are not good enough to be consistent with the difference between the sole exhaust hood and the hood with blade simulations. In the second part of this paper, the focus locates on the direction of the jet-flow of the bucket seal. The tests prove that this direction is the prominent factor to influence the exhaust hood performance. Some extra tests for the seal have also been conducted to analyze this factor. The static pressure recovery for the simulation with labyrinth seal is about only half of the sole exhaust hood simulation. The discussion of these tests show that the seal jet is the main cause for this performance dive, and explain how the seal jet direction changes the flow field of the exhaust hood. It also suggests that the procedure to optimize the seal design is not mature yet, for some nature of the jet-flow remains unclear. It may need more detailed study in the future.

scholarly journals Numerical Simulation and Experimental Study on Flow of Polymer Aqueous Solution in Porous Jet Nozzle

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Minghui Wei ◽  
Chenghuai Wu ◽  
Yanxi Zhou
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Pure Water ◽  
Jet Flow ◽  
Rock Breaking ◽  
Water Jet ◽  
Drilling Process ◽  
Polymer Additive ◽  
Convergent Nozzle ◽  
Jet Nozzle

The addition of a polymer to the jet medium enhances its ability to break rock, and the structure of the nozzle plays a vital role in the full utilization of energy. In this paper, a self-propelled porous jet bit with a support plate is designed, which can prevent the drill bit from jamming due to the jet nozzle against the bottom of the well during the drilling process. And the structural design of the cone-converging nozzle is applied to the forward center nozzle. The polymer additive jet flow field and the pure water jet flow field were compared by numerical simulation and experimental investigation. The results show that the polymer additive jet has a longer isokinetic core, and the rock-breaking volume of the polymer additive jet is much larger than that of the pure water jet, and the optimal spray distance is increased. The forward central jet with the conical convergent nozzle structure has more efficient rock-breaking ability.

Velocity and Momentum Decay Characteristics of a Submerged Viscoplastic Jet

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Flow Field ◽  
Yield Stress ◽  
Initial Velocity ◽  
Momentum Conservation ◽  
Wide Range ◽  
Velocity Decay ◽  
Flow Field Characteristics ◽  
Order Of Magnitude ◽  
Field Information ◽  
Penetration Depths

Velocity and momentum decay characteristics of a submerged viscoplastic non-Newtonian jet are studied within the steady laminar flow regime. The governing mass and momentum conservation equations along with the Bingham rheological model are solved numerically using a finite-difference scheme. A parametric study is performed to reveal the influence of the initial velocity profile, flow inertia, and yield stress presence on the flow field characteristics. Two initial velocity profiles are considered, a top-hat and fully developed pipe jets. The centerline velocity decay is found to be more rapid for the pipe jet than the top-hat one when the fluid is Newtonian while the opposite trend is observed for yield stress Bingham fluids. The decay in the momentum flux of the pipe jet is always less than that of the top-hat jet. Momentum and velocity based jet depths of penetration are introduced and used to analyze the obtained flow field information for a wide range of Reynolds and yield numbers. Depths of penetration are found to linearly increase with the Reynolds number and substantially decrease with the yield number. The presence of yield stress significantly reduces the momentum and velocity penetration depths of submerged top-hat and pipe jets. Penetration depths of yield stress fluids are shown to be more than an order of magnitude smaller than the ones corresponding to Newtonian fluids.

scholarly journals On the acoustic levitation stability behaviour of spherical and ellipsoidal particles

2012 ◽  
Vol 709 ◽  
pp. 581-592 ◽  
Author(s):  
D. Foresti ◽  
M. Nabavi ◽  
D. Poulikakos
Keyword(s):  
Axial Force ◽  
Surrounding Medium ◽  
Radial Force ◽  
Stability Behaviour ◽  
Axial Forces ◽  
Ellipsoidal Particles ◽  
Wide Range ◽  
Depth Analysis ◽  
Sphere Radius ◽  
The Stability

AbstractWe present here an in-depth analysis of particle levitation stability and the role of the radial and axial forces exerted on fixed spherical and ellipsoidal particles levitated in an axisymmetric acoustic levitator, over a wide range of particle sizes and surrounding medium viscosities. We show that the stability behaviour of a levitated particle in an axisymmetric levitator is unequivocally connected to the radial forces: the loss of levitation stability is always due to the change of the radial force sign from positive to negative. It is found that the axial force exerted on a sphere of radius ${R}_{s} $ increases with increasing viscosity for ${R}_{s} / \lambda \lt 0. 0125$ ($\lambda $ is the acoustic wavelength), with the viscous contribution of this force scaling with the inverse of the sphere radius. The axial force decreases with increasing viscosity for spheres with ${R}_{s} / \lambda \gt 0. 0125$. The radial force, on the other hand, decreases monotonically with increasing viscosity. The radial and axial forces exerted on an ellipsoidal particle are larger than those exerted on a volume-equivalent sphere, up to the point where the ellipsoid starts to act as an obstacle to the formation of the standing wave in the levitator chamber.

scholarly journals Numerical simulation on the flow field characteristics and impact capability of liquid nitrogen jet

2017 ◽  
Vol 36 (5) ◽  
pp. 989-1005
Author(s):  
Chengzheng Cai ◽  
Feng Gao ◽  
Zhongwei Huang ◽  
Yugui Yang
Keyword(s):  
Flow Field ◽  
Liquid Nitrogen ◽  
Fluid Dynamic ◽  
Engineering Application ◽  
Physical Property ◽  
Water Jet ◽  
Petroleum Engineering ◽  
Fluid Temperature ◽  
Flow Field Characteristics ◽  
The Impact

With the rapid progress of petroleum engineering, liquid nitrogen jet is expected to be used for perforation and jet fracturing, and then provide a new method for unconventional reservoirs efficient development. In order to research the flow field characteristics and evaluate the impact capability of liquid nitrogen jet, a computation fluid dynamic model was built by coupling the nitrogen physical property equations to simulate the flow field of liquid nitrogen jet. The results indicated that given the same simulation conditions, the impact pressure of liquid nitrogen jet was equivalent to that of water jet. The liquid nitrogen jet presented more excellent impact capability than water jet because of its higher axial and radial velocities. The impact capability of liquid nitrogen jet increased with the growth of nozzle pressure drop and nozzle diameter, decreased with the increasing of standoff distance, and was slightly influenced by fluid temperature. The confining pressure hardly affected the impact capability of liquid nitrogen jet, so it can be neglected in the engineering application. This study uncovered the flow field characteristics of liquid nitrogen jet and could provide theoretical guidance for the application of perforation and fracturing with liquid nitrogen jet.

scholarly journals Numerical Study of the Normal Impinging Water Jet at Different Impinging Height, Based on Wray–Agarwal Turbulence Model

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1744 ◽  
Author(s):  
Hongliang Wang ◽  
Zhongdong Qian ◽  
Di Zhang ◽  
Tao Wang ◽  
Chuan Wang
Keyword(s):  
Flow Field ◽  
Turbulence Model ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Prediction Method ◽  
Reynolds Numbers ◽  
Water Jet ◽  
Impingement Plate ◽  
Theoretical Support ◽  
Flow Field Characteristics

As a kind of water jet technology with strong impinging force and simple structure, the submerged impinging water jet can produce strong scouring action on subaqueous sediments. In order to investigate the flow field characteristics and impinging pressure of submerged impinging water jets at different impinging heights, the Wray-Agarwal (W-A) turbulence model is used for calculation. The velocity distribution and flow field structure at different impinging heights (1 ≤ H/D ≤ 8), and the impinging pressure distribution at the impingement plate under different Reynolds numbers (11, 700 ≤ Re ≤ 35100) are studied. The results show that with the increase of the impinging height, the diffusion degree increases and the velocity decreases gradually when the jet reaches the impingement region. The fluid accelerates first and then decelerates near the stagnation point. The maximum impinging pressure and the impinging pressure coefficient decrease with the increase of the impinging height, but the effective impinging pressure range remains unchanged. In this paper, the distribution characteristics of the impinging pressure in the region of the impingement plate at different heights are clarified, which provides theoretical support for the prediction method of the impinging pressure.

scholarly journals Comparisons of Hydraulic Performance in Permanent Maglev Pump for Water-Jet Propulsion

2014 ◽  
Vol 6 ◽  
pp. 438176 ◽  
Author(s):  
Puyu Cao ◽  
Yang Wang ◽  
K. X. Qian ◽  
Guidong Li
Keyword(s):  
Hydraulic Performance ◽  
Water Jet ◽  
Jet Propulsion

Simulation of the impinging liquid jet cooling process of a flat plate

2015 ◽  
Vol 25 (1) ◽  
pp. 153-170 ◽  
Author(s):  
Paul Stark ◽  
Udo Fritsching
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Flat Plate ◽  
Local Heat Transfer ◽  
Jet Flow ◽  
Water Jet ◽  
Direct Result ◽  
Liquid Jet ◽  
Cooling Process ◽  
Content Type

Purpose – The purpose of this paper is to develop a numerical model to simulate the flow field as well as the conjugate heat transfer during unsteady cooling of a flat plate with a single submerged water jet. At wall temperatures above the liquid boiling point, the vapor formation process and the interaction of the vapor phase with the developing jet-flow field are included. Design/methodology/approach – The time-dependent flow and temperature distribution during all occurring boiling phases as well as the local and temporal distribution of the heat transfer coefficient on a flat plate can be simulated. Findings – The influence of the liquid jet flow rate (10,800=Re_d=32,400) and the nozzle distance to the plate (4=H/d=20) on the transient cooling process are analyzed. This includes the time-dependant positions of the transition regions between the boiling phases on the plate as well as the temperatures at these transition regions. Additionally, the local heat transfer rates are a direct result of the unsteady cooling simulation. Originality/value – A single model approach is developed and utilized to simulate the unsteady cooling process of a flat plate with an impinging water jet including all occurring boiling phases.

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