Multiphase Flow Distribution in MQL Drilling Using Optical Intensity Distribution Based Approach

2019 ◽  
Author(s):  
Jay K. Raval ◽  
Wayne N. P. Hung ◽  
Bruce L. Tai
Keyword(s):  
Velocity Field ◽  
Cfd Simulation ◽  
Circular Cross Section ◽  
Flow Distribution ◽  
Helix Angle ◽  
Machining Processes ◽  
Cross Sectional ◽  
Oil Distribution ◽  
Drill Bits ◽  
Oil Flow

Abstract Oil flow distribution in Minimum Quantity Lubrication (MQL) plays an important role in the efficiency of machining processes, but it remains challenging to measure experimentally. This paper presents a new method to measure the oil flow distribution in through-channel drill bits based on the reflected light intensity. Measurements were conducted from multiple angles in order to map the flow distribution across the channel cross-sectional area. The method is applied to drill bits of a circular cross-section channel and two helix angles, 0° and 30°. The results show that, for the 0° helix angle channel, the oil concentrates near the periphery of the channel, while for 30° helix angle channel, the oil concentrates towards the center of the drill point. Furthermore, Computational Fluid Dynamics (CFD) simulation was conducted to compare with the measurement results, and it was observed that the oil distribution is correlated to the velocity field. Oil flow concentration is high in low velocity regions. Though preliminary, this study has concluded that the velocity field generated using single-phase CFD is a critical indicator for oil distribution in an MQL flow.

Velocity Field and Energy Dissipation in Viscoplastic Flow in Tubes of Non-Circular Cross-Section

2014 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Felipe Godoy
Keyword(s):  
Energy Dissipation ◽  
Velocity Field ◽  
Yield Stress ◽  
Cross Section ◽  
Mechanical Energy ◽  
Longitudinal Velocity ◽  
Circular Cross Section ◽  
Viscoplastic Flow ◽  
Entire Cross Section ◽  
Cross Sectional

An analytical method for determining the velocity field, shear stress and energy dissipation in viscoplastic flow in non-circular straight tubes is presented. Bingham’s model of fluid is used for the case of tubes with several cross-sectional contours that can be arbitrarily chosen through a shape factor imposed in the solution for the longitudinal velocity. The analysis is extended to steady flow in tubes in which the cross-section contour exhibits sharp corners. In these cases three flow zones are distinguished: stagnant, non-zero deformation, and plug zones. The method provides the expressions for determining the boundaries and characteristics of those three zones for a wide variety of cross-section shapes. In particular the dynamics of plug-zones for large values of the yield stress and for contours that markedly differ from circumferences is analyzed. Energy dissipation is determined throughout the entire cross-section, so that the effect of shape on mechanical energy loss is assessed in terms of the yield stress and viscosity of the fluid. Some general expressions that help understand energy dissipation mechanisms are derived by using natural coordinates for the velocity field and related variables. These results draw on several recent works from other researchers and the present authors, which have highlighted the significant difficulty of determining the zones of zero deformation in viscoplastic flow when the related solid boundaries are not elementary.

Characterizing Mist Distribution in Through-Tool Minimum Quantity Lubrication Drills

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Jay K. Raval ◽  
Yi-Tang Kao ◽  
Bruce L. Tai
Keyword(s):  
High Speed ◽  
Minimum Quantity Lubrication ◽  
Flow Distribution ◽  
Critical Factor ◽  
Helix Angle ◽  
Distribution Analysis ◽  
Low Velocity ◽  
Minimum Quantity ◽  
Drill Bits ◽  
Mist Flow

Abstract The mist distribution is a critical factor in through-tool minimum quantity lubrication (MQL) drilling since a small amount of lubricant is used. However, it has rarely been discussed because of the difficulty in measuring the mist flow experimentally. In this paper, an optical approach is developed to approximate the mist distribution by using high-speed images from multiple angles. Drill bits with two through-tool channel shapes (circle and triangle) and three helix angles (0 deg, 30 deg, and 45 deg) are 3D printed for mist distribution analysis. Furthermore, computational fluid dynamics (CFD) is conducted to investigate the underlying physics behind mist flow variations. The results show that, in the circular channel, the mist is concentrated near the periphery; the low concentration region shifts away from the chisel point as the helix angle increases. For the triangular channel, the mist is concentrated near three vertices but is less affected by the helix angle. Furthermore, based on the CFD solution, high mist concentration tends to be in low-velocity regions and vice versa. This study confirms a noticeable difference of mist flow distribution in different through-tool channel designs.

Modeling and Finite Element Analysis of Drill Bit Vibrations

1989 ◽  
Vol 111 (2) ◽  
pp. 148-155 ◽  
Author(s):  
O. Tekinalp ◽  
A. G. Ulsoy
Keyword(s):  
Finite Element ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Helix Angle ◽  
Drill Bit ◽  
Element Analysis ◽  
Cross Sectional ◽  
Various Boundary Conditions ◽  
Drill Bits ◽  
Euler Bernoulli Beam

Drill bit vibrations are modeled using the Euler-Bernoulli beam theory. The model includes the most important properties of drill bits and of the drilling operation. These are: the drill bit cross sectional geometry, the drill helix angle, rotational speed of the drill bit, the thrust force, torque, and cutting forces generated during drilling. Equations of motion are derived in an inertial frame and then transformed to a rotating fluted frame for convenience in the solution. The transformed equations are discretized using finite element techniques. The finite element code developed is capable of solving the eigenvalue problem for various boundary conditions and drill cross sectional geometries. Finite element solutions are compared to known analytical, numerical, and experimental results from the literature and good agreement is obtained.

scholarly journals HYDRODYNAMIC STUDY OF THE OIL FLOW IN A PROTECTIVE RELAY COUPLED TO A POWER TRANSFORMER: CFD SIMULATION AND EXPERIMENTAL VALIDATION

2021 ◽  
pp. 105599
Author(s):  
Ivan Xavier Lins ◽  
Hilário Jorge Bezerra Lima Filho ◽  
Valdemir Alexandre dos Santos ◽  
Júlio César Santos Pereira ◽  
Jose Mak ◽  
...  
Keyword(s):  
Experimental Validation ◽  
Cfd Simulation ◽  
Power Transformer ◽  
Protective Relay ◽  
Oil Flow ◽  
Hydrodynamic Study

Fast CFD Simulation of Horizontal Axis Wind Turbines

2010 ◽  
Author(s):  
Fabio De Bellis ◽  
Luciano A. Catalano ◽  
Andrea Dadone
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Horizontal Axis ◽  
Wall Functions ◽  
Mesh Topology ◽  
Numerical Predictions ◽  
Horizontal Axis Wind Turbines ◽  
Time Required

The numerical simulation of horizontal axis wind turbines (HAWT) has been analysed using computational fluid dynamics (CFD) with the aim of obtaining reliable but at the same time affordable wind turbine simulations, while significantly reducing required overall resources (time, computational power, user skills), for example in an optimization perspective. Starting from mesh generation, time required to extract preliminary aerodynamic predictions of a wind turbine blade has been shortened by means of some simplifications, i.e.: fully unstructured mesh topology, reduced grid size, incompressible flow assumption, use of wall functions, commercial available CFD package employment. Ansys Fluent software package has been employed to solve Reynolds Averaged Navier Stokes (RANS) equations, and results obtained have been compared against NREL Phase VI campaign data. The whole CFD process (pre-processing, processing, postprocessing) has been analysed and the chosen final settings are the result of a trade-off between numerical accuracy and required resources. Besides the introduced simplifications, numerical predictions of shaft torque, forces and flow distribution are in good agreement with experimental data and as accurate as those calcuted by other more sophisticated works.

Investigation of Smooth Pipe Bends Under the Effect of In-Plane Bending

2017 ◽  
Author(s):  
Diana Abdulhameed ◽  
Michael Martens ◽  
J. J. Roger Cheng ◽  
Samer Adeeb
Keyword(s):  
High Stress ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Bend Angle ◽  
Bending Moments ◽  
Bend Radius ◽  
Pipe Bend ◽  
Cross Sectional ◽  
Smooth Pipe ◽  
Plane Bending

Pipe bends are frequently used to change the direction in pipeline systems and they are considered one of the critical components as well. Bending moments acting on the pipe bends result from the surrounding environment, such as thermal expansions, soil deformations, and external loads. As a result of these bending moments, the initially circular cross-section of the pipe bend deforms into an oval shape. This consequently changes the pipe bend’s flexibility leading to higher stresses compared to straight pipes. Past studies considered the case of a closing in-plane bending moment on 90-degree pipe bends and proposed factors that account for the increased flexibility and high-stress levels. These factors are currently presented in the design codes and known as the flexibility and stress intensification factors (SIF). This paper covers the behaviour of an initially circular cross-sectional smooth pipe bend of uniform thickness subjected to in-plane opening/closing bending moment. ABAQUS FEA software is used in this study to model pipe bends with different nominal pipe sizes, bend angles, and various bend radius to cross-sectional pipe radius ratios. A comparison between the CSA-Z662 code and the FEA results is conducted to investigate the applicability of the currently used SIF factor presented in the design code for different loading cases. The study showed that the in-plane bending moment direction acting on the pipe has a significant effect on the stress distribution and the flexibility of the pipe bend. The variation of bend angle and bend radius showed that it affects the maximum stress drastically and should be considered as a parameter in the flexibility and SIF factors. Moreover, the CSA results are found to be un-conservative in some cases depending on the bend angle and direction of the applied bending moment.

Hydraulic Characteristics of the New Type Bulb Turbine With Micro-Head

2013 ◽  
Author(s):  
Lingyu Li ◽  
Yuan Zheng ◽  
Daqing Zhou ◽  
Zihao Mi
Keyword(s):  
Numerical Simulation ◽  
Cfd Simulation ◽  
Guide Vane ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Three Dimensions ◽  
Guide Vanes ◽  
Runner Blade ◽  
Cfd Method ◽  
Bulb Turbine

The head of low-head hydropower stations is generally higher than 2.5m in the world, while micro-head hydropower resources which head is less than 2.5m are also very rich. In the paper, three-dimensional CFD method has been used to simulate flow passage of the micro-head bulb turbine. The design head and unit flow of the turbine was 1m and 3m3/s respectively. With the numerical simulation, the bulb turbine is researched by analyzing external characteristics of the bulb turbine, flow distribution before the runner, pressure distribution of the runner blade surface, and flow distribution of the outlet conduit under three different schemes. The turbine in second scheme was test by manufactured into a physical model. According to the results of numerical simulation and model test, bulb turbine with no guide vane in second scheme has simpler structure, lower cost, and better flow capacity than first scheme, which has traditional multi-guide vanes. Meanwhile, efficiency of second scheme has just little decrease. The results of three dimensions CFD simulation and test results agree well in second scheme, and higher efficiency is up to 77% which has a wider area with the head of 1m. The curved supports in third scheme are combined guide vanes to the fixed supports based on 2nd scheme. By the water circulations flowing along the curved supports which improve energy transformation ability of the runner, the efficiency of the turbine in third scheme is up to 82.6%. Third scheme, which has simpler structure and best performance, is appropriate for the development and utilization of micro-head hydropower resources in plains and oceans.

scholarly journals CFD simulation of gas-liquid floating particles mixing in an agitated vessel

2017 ◽  
Vol 23 (3) ◽  
pp. 377-389 ◽  
Author(s):  
Liangchao Li ◽  
Bin Xu
Keyword(s):  
Velocity Field ◽  
Cfd Simulation ◽  
Solid Phase ◽  
Fluid Model ◽  
Surface Region ◽  
Operating Conditions ◽  
Gas Dispersion ◽  
Agitated Vessel ◽  
Superficial Gas Velocity ◽  
Floating Particles

Gas dispersion and floating particles suspension in an agitated vessel were studied numerically by using computational fluid dynamics (CFD). The Eulerian multi-fluid model along with standard k-? turbulence model was used in the simulation. A multiple reference frame (MRF) approach was used to solve the impeller rotation. The velocity field, gas and floating particles holdup distributions in the vessel were first obtained, and then, the effects of operating conditions on gas dispersion and solid suspension were investigated. The simulation results show that velocity field of solid phase and gas phase are quite different in the agitated vessel. Floating particles are easy to accumulate in the center of the surface region and the increasing of superficial gas velocity is in favor of floating particles off-surface suspension. With increasing solids loading, the gas dispersion becomes worse, while relative solid holdup distribution changes little. The limitations of the present modeling are discussed and further research in the future is proposed.

CFD simulation for the effect of the header match on the flow distribution in a central-type parallel heat exchanger

2018 ◽  
Vol 136 ◽  
pp. 144-153 ◽  
Author(s):  
Jian Zhou ◽  
Ming Ding ◽  
Haozhi Bian ◽  
Yinxing Zhang ◽  
Zhongning Sun
Keyword(s):  
Heat Exchanger ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Central Type
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