Designing the Spindle Parameters of Vortex Spinning by Modeling the Fiber/Air Two-Phase Flow

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Zeguang Pei
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Cone Angle ◽  
Phase Flow ◽  
Two Phase ◽  
Novel Technology ◽  
Yarn Properties ◽  
Vortex Yarn ◽  
Negative Effect ◽  
Yarn Tenacity

Vortex spinning is a novel technology which produces short-staple yarns by utilizing high-speed swirling airflow. The structure of the spindle plays an important role in vortex spinning in terms of its effect on the resulting yarn properties. In this paper, a two-dimensional fluid-structure interaction (FSI) model for the fiber/air two-phase flow is presented to design the two spindle parameters—the spindle cone angle and spindle diameter by evaluating their effects on the fiber dynamics in the flow field inside the twisting system and the resulting yarn tenacity. The coupling between the fiber and airflow is solved and the motional characteristics of the fiber are obtained. It is found that the fiber moves downstream in a varying wavy shape and its spreaded trailing portion is then in a helical motion to form the yarn. The results also show that the increase of the spindle cone angle has a negative effect on the tenacity of the produced vortex yarn. The increased spindle diameter gives rise to the decreased vortex yarn tenacity. The numerical results can provide an explanation for the experimental results reported by previous studies.

scholarly journals Experimental Investigation of the Performance and Spray Characteristics of a Supersonic Two-Phase Flow Ejector with Different Structures

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1166 ◽  
Author(s):  
Shizhen Li ◽  
Wei Li ◽  
Yanjun Liu ◽  
Chen Ji ◽  
Jingzhi Zhang
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Fire Suppression ◽  
Cone Angle ◽  
Water Mist ◽  
Pulsation Period ◽  
Phase Flow ◽  
Two Phase ◽  
Half Cone ◽  
Half Cone Angle

A two-phase flow ejector is an important part of a water mist fire suppression system, and these devices have become a popular research topic in recent years. This paper proposes a supersonic ejector that aims to improve the efficiency of water mist fire suppression systems. The effects of ejector geometric parameters on the entrainment ratio (ER) were explored. The effects of primary flow pressure (PP) on the mixing process and flow phenomena were studied by a high-speed camera. The experimental results show that the ER first increases and then decreases with increasing PP. ER increases with increasing ejector area ratio (AR). The PP corresponding to the maximum ER of ejectors with a different nozzle exit position (NXP) is 3.6 bar. The ejector with an NXP of +1 and AR of 6 demonstrate the best performance, and the ER of this ejector reaches 36.29. The spray half-cone angle of the ejector increases with increasing ER, reaching a maximum value of 7.07°. The unstable atomization half-cone angle is mainly due to a two-phase flow pulsating phenomenon. The pulsation period is 10 ms. In the present study, a general rule that provides a reference for ejector design and selection was obtained through experiments.

High Speed Imaging and Two-Phase Flow Patterns During Flow Boiling in a Single Microchannel

2008 ◽  
Author(s):  
Jacqueline Barber ◽  
Khellil Sefiane ◽  
David Brutin ◽  
Lounes Tadrist
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Pressure Sensors ◽  
Flow Patterns ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Vapour Bubble ◽  
Two Phase ◽  
Over Time

Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two phase flow at a fundamental level. We induced boiling in a single microchannel geometry (hydraulic diameter 727 μm), using a refrigerant FC-72, to investigate several flow patterns. A transparent, metallic, conductive deposit has been developed on the exterior of rectangular microchannels, allowing simultaneous uniform heating and visualisation to be conducted. The data presented in this paper is for a particular case with a uniform heat flux of 4.26 kW/m2 applied to the microchannel and inlet liquid mass flowrate, held constant at 1.33×10−5 kg/s. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop profiles across the microchannel over time. Bubble nucleation, growth and coalescence, as well as periodic slug flow, are observed in the test section. Phenomena are noted, such as the aspect ratio and Reynolds number of a vapour bubble, which are in turn correlated to the associated pressure drops over time. From analysis of our results, images and video sequences with the corresponding physical data obtained, it is possible to follow visually the nucleation and subsequent both ‘free’ and ‘confined’ growth of a vapour bubble over time.

Analysis of Transient Two-Phase Flow in Pressure Safety Valve Outlet Headers

2018 ◽  
Author(s):  
Maral Taghva ◽  
Lars Damkilde
Keyword(s):  
Steady State ◽  
Shock Waves ◽  
High Speed ◽  
Two Phase Flow ◽  
Safety Valve ◽  
Strong Shock ◽  
Flow Property ◽  
Phase Flow ◽  
Transient Pressure ◽  
Two Phase

To protect a pressurized system from overpressure, one of the most established strategies is to install a Pressure Safety Valve (PSV). Therefore, the excess pressure of the system is relieved through a vent pipe when PSV opens. The vent pipe is also called “PSV Outlet Header”. After the process starts, a transient two-phase flow is formed inside the outlet header consisting of high speed pressurized gas interacting with existing static air. The high-speed jet compresses the static air towards the end tail of the pipe until it is discharged to the ambiance and eventually, the steady state is achieved. Here, this transient process is investigated both analytically and numerically using the method of characteristics. Riemann’s solvers and Godunov’s method are utilized to establish the solution. Propagation of shock waves and flow property alterations are clearly demonstrated throughout the simulations. The results show strong shock waves as well as high transient pressure take place inside the outlet header. This is particularly important since it indicates the significance of accounting for shock waves and transient pressure, in contrast to commonly accepted steady state calculations. More precisely, shock waves and transient pressure could lead to failure, if the pipe thickness is chosen only based on conventional steady state calculations.

6. Inviscid instability of high speed two-phase flow

1998 ◽  
Vol 1 (1) ◽  
pp. 7-7 ◽  
Author(s):  
G. H. Schnerr ◽  
S. Adam
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Inviscid Instability

Estimation of Average Void Fraction for Gas-Liquid, Two-Phase Flow in an Industrial Nozzle Assembly Using a Quick-Closing-Valve

2008 ◽  
Author(s):  
Mohammad A. Rahman ◽  
Johana Gomez ◽  
Ted Heidrick ◽  
Brian A. Fleck ◽  
Jennifer McMillan
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Video Camera ◽  
Synchronization Error ◽  
Phase Flow ◽  
Closing Time ◽  
Two Phase ◽  
Void Fractions ◽  
Atomization Performance

Experimentally accurate void fraction measurements are a challenge in an air/water, two-phase flows through an industrial nozzle assembly, as a highly non-uniform void fraction exists in the feeding conduit prior to the nozzle. In this study, average void fractions were measured by isolating a section in the feeding conduit of a horizontal nozzle assembly, termed as the quick-closing-valve (QCV) technique. A high-speed video camera was utilized to capture the asynchronization closing time, tac. The average closing time and asynchronization for the pneumatically controlled valves were 200 ms and 2 ms, respectively. Based on the equation of 100umtac (1−α)/αlc, the synchronization error between the two valves was 1.12%, 1.26%, and 1.79% for the 1%, 2% and 4% ALR cases, respectively; here um is the mixture velocity, α is the void faction, and lc is the closing length. Higher synchronization error at 4% ALR occurs due to enhanced momentum in the flow regime. Experimental results indicate that the average α over the 33.4 cm feeding conduit (6.25 mm ID) was 76% (αtheoretical = 75%) for the 2% ALR, and 85% (αtheoretical = 83%) for the 3.3% ALR. In the two-phase, two-component flow the α affects the drop size and stability of the spray produced from an industrial nozzle assembly. Learning from this study will yield insights and conceptual understanding of two-phase flow phenomena in conduit, which would affect stability, pulsation tendency, and possibly atomization performance of the nozzle downstream. Two-phase flow nozzles have wide applications in the industries, e.g. petrochemical, pharmaceutical, and others.

Numerical Simulation and Experimental Validation on the Particle Trajectory in a Solid Propellant Rocket Chamber

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano ◽  
Timin Cai ◽  
Jiang Li
Keyword(s):  
Numerical Simulation ◽  
Experimental Method ◽  
High Speed ◽  
Particle Trajectory ◽  
Two Phase Flow ◽  
Measurement Data ◽  
Special Method ◽  
Phase Flow ◽  
Two Phase ◽  
Particle Injection

Abstract In solid rocket motors (SRMS) using aluminized composite solid propellants and submerged nozzles a two-phase flow pattern is one of the main flow characteristics needs to be investigated. The modeling and validation of two-phase flow are the focus in this research field. In this paper the authors first traced the particle trajectory in a SRM chamber by using numerical method, and then developed a new experimental method to measure the particle trajectory in a SRM chamber to validate the numerical results. The experimental method was based on the RTR (X-ray Real-time Radiography) technique and high-speed motion analyzer. A special method was developed to imitate the particle injection on the propellant surface. The calculation results and measurement data show that the trajectory obtained by numerical simulation was in good agreement with the measured one by imposing proper boundary conditions. For particles with diameter of 75μm, the initial velocity factor of particle is approximately 0.4, and the particles pass through the centerline in both calculation and experiment. The present method can be extended to study the impingement of particles on the wall and other related two-phase flow patterns.

scholarly journals Numerical Analysis of Dry Ice Blasting Convergent-Divergent Supersonic Nozzle

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4787 ◽  
Author(s):  
Aleksandra Dzido ◽  
Piotr Krawczyk ◽  
Michalina Kurkus-Gruszecka
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Two Phase Flow ◽  
Supersonic Nozzle ◽  
Phase Flow ◽  
Two Phase ◽  
Dry Ice ◽  
Cleaning Methods ◽  
Industrial Cleaning ◽  
Dry Ice Blasting

There are several well-known and widely used industrial cleaning methods in the market today. One of them is dry ice blasting. In this method, moisture-free air is compressed, mixed with solid CO2 particles, and blasted though a nozzle; in the process, the gas expands, propelling its velocity. The high-speed, two-phase flow cleans by supercooling and crushing particles on the surface, causing dry ice sublimation. As the nozzle is a crucial component of the system, the authors conducted a numerical analysis of the geometry of the proposed convergent-divergent nozzle. A mathematical model of the supersonic, two-phase flow was developed and implemented in commercial Computational Fluid Dynamics (CFD) code. Various operating parameters, such as inlet pressure and dry ice mass flow, were taken into consideration.

Visual Criteria for Measuring Two-phase Flow Rate in Venturi with Flow Homogenizer

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Sangho Sohn ◽  
Jaebum Park ◽  
Dong-Wook Oh
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Two Phase Flow ◽  
Volume Fraction ◽  
Differential Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
3 Dimensional ◽  
Lower Amplitude ◽  
Gas Volume

A simple use of Venturi might be used to measure two-phase flow rate within relatively low GVF(gas volume fraction). Upstream flow entering Venturi can be improved with installed flow homogenizer which is easily fabricated by 3-dimensional printer with multiple holes. Simultaneous measurement between high-speed flow visualization and dynamic differential pressure measurement was made to find visual criteria for two-phase flow rate measurement with different GVF ranged from 0% to 30%. It was observed that the two-phase flow rate can be reliably measured up to 15% of GVF using flow homogenizer. FFT(Fast-Fourier Transform) results proved that the long flow homogenizers (type 2 and 4) showed a lower amplitude of differential pressure (Δp) than the short flow homogenizers (type 1 and 3) respectively. So the optimized flow homogenizer can be useful to measure two-phase flow rate at low GVF.

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