Experimental Characterization of Intrinsic Properties Associated With Air-Assisted Liquid Jet and Liquid Sheet

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
K. Balaji ◽  
V. Sivadas ◽  
Vishnu Radhakrishna ◽  
Khushal Ashok Bhatija ◽  
K. Sai Charan
Keyword(s):  
High Speed ◽  
Liquid Sheet ◽  
Interfacial Instability ◽  
Wave Number ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Experimental Characterization ◽  
Interfacial Wave ◽  
Visualization Techniques

The present study focuses on experimental characterization of interfacial instability pertinent to liquid jet and liquid sheet in the first wind-induced zone. To accomplish this objective, the interfacial wave growth rate, critical wave number, and breakup frequency associated with air-assisted atomizer systems were extracted by utilizing high-speed flow visualization techniques. For a range of liquid to gas velocities tested, nondimensionalization with appropriate variables generates the corresponding correlation functions. These functions enable to make an effective comparison between interfacial wave developments for liquid jet and sheet configurations. It exhibits liquid sheets superiority over liquid jets in the breakup processes leading to efficient atomization.

Experimental Characterization of a Liquid Jet Emanating From An Effervescent Atomizer

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
V. Sivadas ◽  
K. Balaji ◽  
Antriksha Vishwakarma ◽  
Sundar Ram Manikandan
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Low Frequency ◽  
Intrinsic Property ◽  
Liquid Jet ◽  
Experimental Characterization ◽  
Jet Breakup ◽  
Effervescent Atomizer ◽  
Visualization Techniques

Abstract The study focuses on experimental characterization of the primary atomization associated with an effervescent atomizer. Unlike the existing designs available in the literature that inject air perpendicular to the liquid flow direction, the present atomizer design utilizes coflowing air configuration. In doing so, the aerodynamic shear at the liquid–gas interface create instability and enhance the subsequent jet breakup. Both integrated and intrinsic properties of the liquid jet were extracted by utilizing high-speed flow visualization techniques. The integrated property consists of breakup length, while the intrinsic property involves primary and intermediate breakup frequencies. The primary instability is characterized by low-frequency sinusoidal mode, whereas the intermediate instability consists of high-frequency dilatational mode. Dimensionless plots of these parameters with Weber number ratio leads to a better collapse of data, thereby generating appropriate universal functions. The combined diagram of frequencies converge with increasing relative velocity. This may be due to the dominance of energy consuming sinusoidal wave as the aerodynamic shear increases.

Experimental Characterization of the Whipping Instability of Charged Microjets in Liquid Baths

2010 ◽  
Vol 1272 ◽  
Author(s):  
Guillaume Riboux ◽  
Álvaro Gómez-Marín ◽  
Antonio Barrero ◽  
Alberto Fernández-Nieves ◽  
Ignacio G. Loscertales
Keyword(s):  
Electric Energy ◽  
Theoretical Models ◽  
Polymer Fibers ◽  
Liquid Jets ◽  
Experimental Characterization ◽  
Thin Polymer ◽  
Electrified Jets ◽  
Liquid Flows ◽  
Capillary Liquid

AbstractCapillary liquid flows have shown their ability to generate micro and nano-structures which can be used to synthesize material in the micro or nanometric size range. For instance, electrified capillary liquid jets issued from a Taylor are broadly used to spin micro and nanofibers when the liquid consists of a polymer solution or melt, a process termed electrospinning. In this process, the electrified capillary jet may develop a nonaxisymmetric instability, usually referred to as whipping instability, which very efficiently transforms electric energy into stretching energy, thus leading to the formation of extremely thin polymer fibers. Even though non axysimmetric instabilities of electrified jets were first investigated some decades ago, the existing theoretical models provide a qualitative understanding of the phenomenon but none of them is accurate enough when compared with experimental results. This whipping instability usually manifests itself as fast and violent lateral motion of the charged jet, which makes it difficult its characterization in the laboratory. However, this instability also develops when electrospinning is performed within a liquid bath instead of air. Although it is essentially the same phenomenon, the frequency of the whipping oscillations is much slower in the former case than in the latter, thus allowing detailed experimental characterization of the whipping instability. Furthermore, since the outer fluid is a liquid, its density and viscosity may now be used to influence the dynamics of the electrified capillary jet. In this work we present and rationalize the experimental data collecting the influence of the main parameters on the whipping characteristics of the electrified jet (frequency, amplitude, etc.).

Study on some Aspects of Breakup Characteristics of Power-Law Fluid with Impinging Jets Based on Mechanics Properties

2012 ◽  
Vol 625 ◽  
pp. 57-60
Author(s):  
En Dong Wang ◽  
Yan Yin ◽  
Qing Du
Keyword(s):  
Power Law ◽  
High Speed ◽  
Wave Length ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Liquid Jets ◽  
Power Law Fluid ◽  
Round Jets ◽  
Breakup Length ◽  
Jet Velocity

Shear-thinning power-law fluid is a kind of non-Newtonian fluid in which the viscosity is a function of shear rate. Impinging jets system is used to study the breakup characteristics of power-law liquid sheets formed by two symmetrical round jets in this study. High quality images are obtained from the experiment with a high speed camera and breakup length is extracted from the images. Closed-rim sheet, web-like sheet and ligaments sheet are observed with the increase of jet velocity. A series of images show that the wave length on the surface of sheets tends to decline as the jet velocity increases. At a low We number, the breakup length increases with an increasing We number. However, it first increases and then decreases when the liquid sheet breaks up at a high We number. The liquid jets with larger diameter collide to each other and lead to a liquid sheet with a smaller breakup length.

Experimental Investigation on Flow and Breakup of Two-Dimensional Liquid Jets

2019 ◽  
Author(s):  
Amin Jaberi ◽  
Mehran Tadjfar
Keyword(s):  
High Speed ◽  
Volume Flow Rate ◽  
Quantitative Description ◽  
Sheet Thickness ◽  
Liquid Jets ◽  
Liquid Jet ◽  
High Speed Photography ◽  
Two Dimensional ◽  
Aspect Ratios ◽  
Wide Range

Abstract Studying of injectors with non-circular geometries has recently come to the spotlight of researchers as a potential technique to improve the liquid injection characteristics of different systems. In this work, the flow physics and breakup of two-dimensional liquid jets issued from flat slits into still air were experimentally investigated. Three injectors with aspect ratios of 30, 60 and 90 and thickness of 0.35 mm were manufactured to obtain two-dimensional liquid flow at the nozzle exit. The tests were performed for a wide range of volume flow rate, varying from 10 L/h to 240 L/h. Backlight shadowgraphy and high speed photography were employed to capture the flow dynamics of the jets. In order to capture every detail of the flow, photos of the liquid jet were taken from two views with 90° from each other. Using the visualizations, different regimes of the jet flow were explored and a regime map was proposed to distinguish these regimes based on the non-dimensional parameters of the liquid jet. Moreover, quantitative description of the main features of jet flows were obtained using an in-house image processing program. Measurements of different parameters including convergence length, maximum width, breakup length, sheet thickness to name a few, were conducted.

Experiments on the Injection of Elliptical Liquid Jets Into a Low Speed Airflow

2018 ◽  
Author(s):  
Yosef Rezaei ◽  
Mehran Tadjfar
Keyword(s):  
Experimental Investigation ◽  
Weber Number ◽  
Momentum Flux ◽  
High Speed ◽  
Flux Ratio ◽  
Major Axis ◽  
Liquid Jets ◽  
Liquid Jet ◽  
High Speed Camera ◽  
Subsonic Crossflow

An experimental investigation was performed to study the physics of liquid jets injected into a low subsonic crossflow. The jets are issued from elliptical and circular injectors with equivalent exit area. The liquid jet was visualized using shadowgraph technique and a high speed camera was used to record the instantaneous status of the jet. The liquid / air momentum flux ratio and air Weber number were varied to examine their effects on different parameters of the flow like liquid jet column trajectory, breakup point and breakup regimes. The major axis of the elliptical nozzle was aligned parallel and perpendicular to the air crossflow direction. Two different breakup modes were observed, column breakup and bag breakup. Based on the obtained results some characteristics of injected liquid jets into the air crossflow such as penetration depth and the trajectory of liquid jet were affected by changing the nozzle exit shape.

Experimental Characterization of Losses in Bladeless Turbine Prototype

2021 ◽  
Author(s):  
Avinash Renuke ◽  
Federico Reggio ◽  
Alberto Traverso ◽  
Matteo Pascenti
Keyword(s):  
High Speed ◽  
Electrical Power ◽  
Working Fluid ◽  
Small Scale ◽  
Experimental Characterization ◽  
Scaling Effects ◽  
Low Performance ◽  
Low Sensitivity ◽  
First Time

Abstract Multi-disk bladeless turbines, also known as Tesla turbines, are promising in the field of small-scale power generation and energy harvesting due to their low sensitivity to down-scaling effects, retaining high rotor efficiency. However, low (less than 40%) overall isentropic efficiency has been recorded in the experimental literature. This article aims for the first time to a systematic experimental characterization of loss mechanisms in a 3-kW Tesla expander using compressed air as working fluid and producing electrical power through a high speed generator (40krpm). The sources of losses discussed are: stator losses, stator-rotor peripheral viscous losses, end wall ventilation losses and leakage losses. After description of experimental prototype, methodology and assessment of measurement accuracy, the article discusses such losses aiming at separating the effects that each loss has on the overall performance. Once effects are separated, their individual impact on the overall efficiency curves is presented. This experimental investigation, for the first time, gives the insight into the actual reasons of low performance of Tesla turbines, highlighting critical areas of improvement, and paving the way to next generation Tesla turbines, competitive with state of the art bladed expanders.

Theoretical Analysis of Surface Waves on Liquid Jets in Crossflows with Deformation

2013 ◽  
Vol 681 ◽  
pp. 152-157
Author(s):  
Shao Lin Wang ◽  
Yong Huang ◽  
Fang Wang ◽  
Zhi Lin Liu
Keyword(s):  
Growth Rate ◽  
Theoretical Analysis ◽  
Surface Waves ◽  
Cross Section ◽  
Aerodynamic Force ◽  
Linear Instability ◽  
Wave Number ◽  
Liquid Jets ◽  
Liquid Jet ◽  
The Cross

Liquid jets in cross air flows are widely used and play an important role in propulsion systems, such as ramjet combustors. Surface waves on the liquid jets in gaseous crossflows have been observed in numerous experiments. Especially for lower gas Webber number, liquid jets breaks up due to the surface waves. However compared with injecting into gas coaxial flow, liquid jet will be deformed in crossflow due to the transverse aerodynamic force. Deformation of jet is investigated by analyzing stress force equilibrium of the cross-section. Though linear instability analysis, dispersion relation and growth rate of surface waves of liquid jet with deformation were derived. According to the present theoretical analysis, the cross-section shape can be deformed to stable ellipse only if the gas velocity was lower than 9m/s for 1mm diameter jet. The maximum growth rate of disturbances takes place at wave number 0.7 approximately, and it will decrease with increasing the jet diameter. The range of instable wave number will expand and the most instable wave number will grow for the deformed jets.

Experiments on liquid jet instability

1970 ◽  
Vol 40 (3) ◽  
pp. 495-511 ◽  
Author(s):  
E. F. Goedde ◽  
M. C. Yuen
Keyword(s):  
Wave Number ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Audio Frequency ◽  
Linear Effect ◽  
Jet Instability ◽  
Non Linear ◽  
Linear Effects ◽  
The Difference ◽  
Time Sequences

The capillary instability of vertical liquid jets of different viscosities have been examined by imposing audio-frequency disturbances. Real time sequences of photographs allow a direct measurement of growth rates of disturbances of various wavelengths. Results show that in general non-linear effects dominate the growth processes. This is in agreement with Yuen's analysis. The growth rate of the difference between the neck and the swell, however, agrees well with the linearized analysis of Rayleigh and Chandrasekhar. The non-linear effect causes a liquid jet to disintegrate into drops with ligaments in between. The sizes of the ligaments decrease with increasing wave-number. The subsequent roll up of the ligament into droplet, the eventual coalescing of the droplet with the main drop and drop oscillation have also been studied.

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