Investigation on Jet Breakup of High-Viscous Fuels for Entrained Flow Gasification

2016 ◽  
Author(s):  
Thomas Müller ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Alexander Sänger ◽  
Tobias Jakobs ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Operating Conditions ◽  
Nozzle Geometry ◽  
Liquid Jet ◽  
Liquid Viscosity ◽  
High Speed Camera ◽  
Entrained Flow ◽  
Jet Breakup ◽  
Entrained Flow Gasification

The present study focuses on the atomization behaviour of liquids in external mixing twin fluid nozzles and investigates a wide range of viscosities as well as different nozzle geometries at a gas to liquid ratio (GLR) typically used in entrained flow gasification. In a first stage experiments were performed using water and water-glycerol-mixtures as Newtonian model fuels with liquid viscosity up to 400 mPa s. Jet breakup was investigated qualitatively using a high speed camera as well as using a PIV and LDA-System for detailed quantitative investigation of the flow field. Two different primary instabilities flapping and pulsating mode were detected which are dependent on operating conditions of the nozzle (e.g. GLR) and rheological properties of the liquid phase (e.g. liquid viscosity) as well as nozzle geometry. For better interpretation of the phenomena occurring during jet breakup a frequency-analysis of the primary instabilities was performed using the pictures of the high speed camera. In addition, compressible large eddy simulations (LES) were preformed to describe the experimental observations and to capture the morphology of the primary breakup as well as the important flow field characteristics. The numerical simulations were conducted by means of the open source CFD software OpenFOAM. A Volume of Fluid (VOF) approach was used to track the unsteady evolution and breakup of the liquid jet. Comparison of experimental and numerical results shows a good agreement concerning breakup frequency, velocity fields and morphology. The breakup frequency varied in a range of 430 to 757 Hz depending on operating condition and nozzle geometry. Based on these results a more detailed understanding of the physics leading to liquid jet breakup and finally atomization process will be available.

Visual Observation of Fragmentation Behavior on Molten Material Jet Surface in Coolant

2008 ◽  
Author(s):  
Yuta Uchiyama ◽  
Yutaka Abe ◽  
Akiko Fujiwara ◽  
Hideki Nariai ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
Water Surface ◽  
High Speed ◽  
Internal Flow ◽  
Core Material ◽  
Generation Process ◽  
High Speed Camera ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

For the safety design of the Fast Breeder Reactor (FBR), it is strongly required that the post accident heat removal (PAHR) is achieved after a postulated core disruptive accident (CDA). In the PAHR, it is important that the molten core material is solidified in sodium coolant which has high boiling point. Thus it is necessary to estimate the jet breakup length which is the distance that the molten core material is solidified in sodium coolant. In the previous studies (Abe et al., 2006), it is observed that the jet is broken up with fragmenting in water coolant by using simulated core material. It is pointed out that the jet breakup behavior is significantly influenced by the fragmentation behavior on the molten material jet surface in the coolant. However, the relation between the jet breakup behavior and fragmentation on the jet surface during a CDA for a FBR is not elucidated in detail yet. The objective of the present study is to elucidate the influence of the internal flow in the jet and fragmentation behavior on the jet breakup behavior. The Fluorinert™ (FC-3283) which is heavier than water and is transparent fluid is used as the simulant material of the core material. It is injected into the water as the coolant. The jet breakup behavior of the Fluorinert™ is observed by high speed camera to obtain the fragmentation behavior on the molten material jet surface in coolant in detail. To be cleared the effect of the internal flow of jet and the surrounding flow structure on the fragmentation behavior, the velocity distribution of internal flow of the jet is measured by PIV (Particle Image Velocimetry) technique with high speed camera. From the obtained images, unstable interfacial wave is confirmed at upstream of the jet surface, and the wave grows along the jet-water surface in the flow direction. The fragments are torn apart at the end of developed wave. By using PIV analysis, the velocity at the center of the jet is fast and it suddenly decreases near the jet surface. This means that the shear force acts on the jet and water surface. From the results of experiment, the correlation between the interfacial behavior of the jet and the generation process of fragments are discussed. In addition, the influence of surface instability of the jet induced by the relative velocity between Fluorinert™ and coolant water on the breakup behavior is also discussed.

An Impact of Self-Recirculation Casing Treatment (SRCT) Configurations on Impeller Stall Margin and the Flow Field

2012 ◽  
Author(s):  
Yan Ma ◽  
Guang Xi ◽  
Guangkuan Wu
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Angle ◽  
Stall Margin ◽  
Casing Treatment ◽  
Swirl Velocity ◽  
Inlet Swirl ◽  
Unsteady Simulation

The present paper describes an investigation of stall margin enhancement and a detailed analysis of the impeller flow field due to self-recirculation casing treatment (SRCT) configuration of a high-speed small-size centrifugal impeller. The influence of different SRCT configurations on the impeller flow field at near-stall condition has been analyzed, highlighting the improvement in stall flow ability. This paper also discusses the influence of the SRCT configurations on the inlet flow angle, inlet swirl velocity and loss distribution in the impeller passage to understand the mechanism of the SRCT configurations in enhancing the stall margin of the impeller. The variation of the bleed flow rate at different operating conditions is also presented in this paper. Finally, the time-averaged unsteady simulation results at near-stall point are presented and compared with steady-state solutions.

scholarly journals Estimation of High-Speed Liquid-Jet Velocity Using a Pyro Jet Injector

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Naohisa Takagaki ◽  
Toru Kitaguchi ◽  
Masashi Iwayama ◽  
Atsushi Shinoda ◽  
Hiroshige Kumamaru ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Liquid Jet ◽  
Liquid Density ◽  
Liquid Viscosity ◽  
Ejection Velocity ◽  
Piston Motion ◽  
Ansys Fluent ◽  
Piston Displacement ◽  
Jet Velocity

AbstractThe high-speed liquid-jet velocity achieved using an injector strongly depends on the piston motion, physical property of the liquid, and container shape of the injector. Herein, we investigate the liquid ejection mechanism and a technique for estimating the ejection velocity of a high-speed liquid jet using a pyro jet injector (PJI). We apply a two-dimensional numerical simulation with an axisymmetric approximation using the commercial software ANSYS/FLUENT. To gather the input data applied during the numerical simulation, the piston motion is captured with a high-speed CMOS camera, and the velocity of the piston is measured using motion tracking software. To reproduce the piston motion during the numerical simulation, the boundary-fitted coordinates and a moving boundary method are employed. In addition, we propose a fluid dynamic model (FDM) for estimating the high-speed liquid-jet ejection velocity based on the piston velocity. Using the FDM, we consider the liquid density variation but neglect the effects of the liquid viscosity on the liquid ejection. Our results indicate that the liquid-jet ejection velocity estimated by the FDM corresponds to that predicted by ANSYS/FLUENT for several different ignition-powder weights. This clearly shows that a high-speed liquid-jet ejection velocity can be estimated using the presented FDM when considering the variation in liquid density but neglecting the liquid viscosity. In addition, some characteristics of the presented PJI are observed, namely, (1) a very rapid piston displacement within 0.1 ms after a powder explosion, (2) piston vibration only when a large amount of powder is used, and (3) a pulse jet flow with a temporal pulse width of 0.1 ms.

Experimental study of fibre breakup and shot formation in melt blowing nozzle designs

2020 ◽  
pp. 152808372094927 ◽  
Author(s):  
Ignacio Formoso ◽  
Alejandro Rivas ◽  
Gerardo Beltrame ◽  
Gorka S Larraona ◽  
Juan Carlos Ramos ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Flux Ratio ◽  
Adhesive Bond ◽  
Operating Conditions ◽  
Nozzle Geometry ◽  
Dimensionless Temperature ◽  
Melt Blowing ◽  
High Speed Imaging ◽  
Adhesive Bonds

The high demand for quality in the manufacture of absorbent hygiene products requires the adhesive bonds between layers to be as uniform as possible. An experimental study was conducted on two industrial multihole melt blowing nozzle designs used for hot-melt adhesive applications for hygiene products, in order to study two defects that influence the quality of the adhesive bond: fibre breakup, resulting in contamination, and the presence of shots, undesirable lumps that end up in the finished product. To this end, the fibre dynamics were captured at the nozzle exit region by using high-speed imaging. From the results it was observed that die drool is the main source of shot formation, while fibre breakup occurs as a result of applying a sufficiently large force in the direction perpendicular to the fibre. In addition, three dimensionless parameters were defined, the first two being the air-polymer flux ratio and the dimensionless temperature ratio, both of which represent the operating conditions, and the remaining one being the force ratio, which represents the nozzle geometry. The effect of these parameters on fibre breakup and shot formation was studied and the results indicate that both the operating conditions and the nozzle geometry were responsible for the onset of the fibre breakup and for the formation of shots. More precisely, both defects turned out to be dominated by the air-polymer flux ratio and the air tilt angle. The results that emerge from this study are useful for the enhancement of industrial melt blowing nozzles.

Experimental Investigation of Liquid Jet Breakup in a Cross Flow of a Swirling Air Stream

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Tushar Sikroria ◽  
Abhijit Kushari ◽  
Saadat Syed ◽  
Jeffery A. Lovett
Keyword(s):  
Experimental Investigation ◽  
Momentum Flux ◽  
High Speed ◽  
Cross Flow ◽  
Flux Ratio ◽  
Liquid Jet ◽  
Breakup Process ◽  
Breakup Length ◽  
Jet Breakup ◽  
Penetration Behavior

This paper presents the results of an experimental investigation of liquid jet breakup in a cross flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach number 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using matlab to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes—bag breakup, column breakup, shear breakup, and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15 deg swirl show reduced breakup length and penetration related to the nonuniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.

Air-Blown Entrained-Flow Gasification of Biomass: Influence of Operating Conditions on Tar Generation

2017 ◽  
Vol 31 (10) ◽  
pp. 10924-10932 ◽  
Author(s):  
Ludwig Briesemeister ◽  
Michael Kremling ◽  
Sebastian Fendt ◽  
Hartmut Spliethoff
Keyword(s):  
Operating Conditions ◽  
Entrained Flow ◽  
Biomass Influence ◽  
Entrained Flow Gasification

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.

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.

Estimation of Fragmentation on Jet Breakup in Coolant

2012 ◽  
Author(s):  
Taihei Kuroda ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Iwasawa Yuzuru ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Flow Field ◽  
Tap Water ◽  
Energy Ratio ◽  
Liquid Jet ◽  
Sodium Coolant ◽  
Molten Material ◽  
Colorless Liquid ◽  
Fragmentation Behavior ◽  
Breakup Length ◽  
Jet Breakup

Fast Breeder Reactor (FBR) is designed with safety in mind. However, there is billion to one possibility that a hypothetical Core Disruptive Accident (CDA) occurs. When CDA occurs, the Post Accident Heat Removal (PAHR) must be achieved. In the PAHR, the molten material is required to be fragmented and solidified in sodium coolant. In order to estimate whether the molten material jet is completely solidified in sodium coolant or not, it is significant to estimate jet breakup length. Although, the jet breakup length is influenced with fragmentation behavior, the correlation between them is not clear yet. Therefore, it is strongly required to clarify the mechanism of the fragmentation behavior on the jet surface. The objective of the present study is to estimate fragmentation on jet breakup in coolant experimentally. Tap water and Fluorinert™ (FC-3283) are used as simulated coolant and molten material, respectively. Flourinert is transparent and colorless liquid and its density is higher than water, therefore we can observe internal flow structure of Fluorinert. Fluorinert injected into water, and the jet breakup behavior and the fragmentation behavior of the jet are observed by using high speed video camera. In order to estimate fragmentation on liquid jet, we identified the position of the interface with back lighting technique and also, we conducted velocity measurement with Particle Image Velocimetry (PIV) technique simultaneously. It is observed that interfacial waves of the jet are generated. Waves are pulled with surrounding liquid and grown up. Finally, a fragment is separated as a droplet from front edge of the wave. Also, the vorticity is evaluated from the velocity data in order to investigate influence of the flow field in detail. From the result of calculating vorticity, the high value was estimated when jet was fragmented. It is suggested that fragmentation behavior correlates with the surrounding flow field. And the energy ratio contributing to fragmentation is calculated from velocity field. The energy ratio is important to investigate the amount of the fragmentation on liquid jet. Fragmentation on jet breakup in coolant is estimated.

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