scholarly journals Simulation of the Primary Jet Breakup of Non-Newtonian Fuels: Basic Research for Simulation-Assisted Design of Low-Grade Fuel Burner

2018 ◽  
Author(s):  
Thomas Müller ◽  
Kathrin Kadel ◽  
Peter Habisreuther ◽  
Dimosthenis Trimis ◽  
Nikolaos Zarzalis ◽  
...  
Keyword(s):  
Surface Tension ◽  
Research Work ◽  
High Viscosity ◽  
Spray Angle ◽  
Low Grade ◽  
Breakup Length ◽  
Third Phase ◽  
Jet Breakup ◽  
Primary Breakup ◽  
Characteristic Features

The research work of the present study is focused on the numerical simulation of primary breakup of high-viscosity non-Newtonian fluids. For the experimental investigation of fluid properties such as viscosity, surface tension and flow behaviour on the jet breakup an external mixing twin-fluid nozzle is used, as investigated in a previous study [Müller et al., ASME Turbo Expo 2016, GT2016-56371]. To describe the disintegration process of the fluids, characteristic features like liquid jet morphology, breakup length, breakup frequency and spray angle are evaluated. Furthermore, the primary breakup of slurries is simulated without discretizing the particles as a third phase, which heavily reduced the computational effort. Instead, the physical properties (density, viscosity) of the liquid phase take the influence of the particles into account. The primary breakup was investigated using the open source CFD software OpenFOAM. To gather the morphology of the primary breakup and the flow field characteristics compressible large eddy simulations (LES) were performed and the movement of the gas-liquid interface was captured by means of the Volume of Fluid-Method (VOF). The conducted simulations showed good agreement with experimental results with respect to the characteristic features (e.g. breakup length) and the significant influence of viscosity and surface tension on the primary breakup. It is reasonably justified that the used OpenFOAM code and VOF is sufficient to simulate the primary breakup of particle laden liquids without discretizing particles as a third phase. Moreover, those findings contribute to a better understanding of the physics responsible of the breakup of high-viscosity liquid jets and as well to create an experimentally validated CFD based tool for future burner development and optimization.

scholarly journals Influence of Reactor Pressure on the Primary Jet Breakup of High-Viscosity Fuels: Basic Research for Simulation-Assisted Design of Low-Grade Fuel Burner

2018 ◽  
Author(s):  
Thomas Müller ◽  
Kathrin Kadel ◽  
Peter Habisreuther ◽  
Dimosthenis Trimis ◽  
Nikolaos Zarzalis ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Research Work ◽  
Basic Research ◽  
High Viscosity ◽  
Low Grade ◽  
Breakup Length ◽  
System Pressure ◽  
Wide Range ◽  
Primary Breakup ◽  
Characteristic Features

Detail investigations on the primary breakup of high-viscosity liquids using external-mixing twin-fluid nozzles at increased system pressure are scarce. Therefore, the research work of the present study is focused on the investigation of pressure influence (1 - 11 bar (abs)) on the primary breakup by numerical simulation based on a previously studied nozzle [Müller et al., ASME Turbo Expo 2016, GT2016-56371]. The pressure influence was investigated for two liquids applying a wide range of viscosities (100 mPa s; 400 mPa s) and two atomizing air velocities (58 m/s; 74 m/s). To describe the disintegration process of the fluids, characteristic features like liquid jet morphology, breakup length and breakup frequency were evaluated. The primary breakup was investigated using the open source CFD software OpenFOAM. To gather the morphology of the primary breakup and the flow field characteristics compressible large eddy simulations (LES) were performed and the movement of the gas-liquid interface was captured by means of the Volume of Fluid-Method (VOF). The conducted simulations showed good agreement with experimental results with respect to the characteristic features (e.g. morphology and breakup length) and revealed a decrease of the breakup length with increasing ambient pressure for a constant liquid mass flow and atomizing air velocity. Moreover, those findings will contribute to a better understanding of the physics of the breakup of high-viscosity liquid jets and as well to create an experimentally validated CFD based tool for future burner development and optimization.

Influence of Nozzle Design Upon the Primary Jet Breakup of High-Viscosity Fuels for Entrained Flow Gasification

2017 ◽  
Author(s):  
Thomas Müller ◽  
Alexa Dullenkopf ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Alexander Sänger ◽  
...  
Keyword(s):  
Research Work ◽  
Flux Ratio ◽  
Liquid Structure ◽  
High Viscosity ◽  
Design Parameters ◽  
Liquid Jets ◽  
Jet Breakup ◽  
Internal Mixing ◽  
Primary Breakup ◽  
Entrained Flow Gasification

The research work of the present study is focused on the influence of design parameters of twin-fluid nozzles used for the atomization of high-viscosity fuels with respect to the primary breakup of the liquid jet. Two external mixing twin-fluid nozzles, which have already been investigated in previous studies [1, 2], were chosen as basic design. Based on the previous findings the web thickness between fuel and oxidizer supply was varied. In addition both designs were extended by a channel for internal mixing of gas and liquid with a length to diameter ratio of one. Moreover one of the basic nozzles was scaled by decrease of the effective areas in a way that momentum flux ratio as well as gas to liquid mass flow ratio was kept constant. The newly designed atomizers were subsequently investigated with regard to the influence of the changes upon the primary jet breakup using CFD simulations. The numerical simulations were conducted by means of the open source package OpenFOAM. The Volume of Fluid method was used for the determination of the gas-liquid interface. These simulations were then compared with experimentally validated simulations of the basic nozzle designs with regard to the breakup morphology of the jet and the mode of the primary surface instability. In addition, the liquid structure was examined by comparison of breakup length and frequency. The results of these simulations showed that small changes in the atomizer design heavily influence the primary breakup, which in turn influences the overall performance of the atomizer (e.g. SMD). Moreover, these findings will contribute to a better understanding of the physics of the breakup of high-viscosity liquid jets and as well to create an experimentally validated CFD based tool for future burner development and optimization.

The Effects of Surfactant on Simplex Nozzle Spray Behavior and its Comparison to Liquid Fuels

2013 ◽  
Author(s):  
Ashkan Davanlou ◽  
Joshua Lee ◽  
Saptarshi Basu ◽  
Ranganathan Kumar
Keyword(s):  
Experimental Study ◽  
Surface Tension ◽  
Numerical Models ◽  
Droplet Diameter ◽  
Pure Water ◽  
Diagnostic Technique ◽  
Injection Pressure ◽  
Droplet Breakup ◽  
Spray Angle ◽  
Breakup Length

Pressure-swirl nozzles (simplex nozzles) are used in various field applications such as aero-engines, power generation, spray painting and agricultural irrigation. For this particular nozzle, research in the past decade has dealt with the development of numerical models for predicting droplet distribution profiles. Although these results have been valuable, the experimental results have been contradictory, therefore fundamental understanding of the influence of properties in nozzle is important. This paper experimentally investigates the effect of surfactants on breakup and coalescence. Since most of the fuels and biofuels have low surface tension compared to water, a comparative analysis between a surfactant solution and a liquid fuel is imperative. For this experimental study, a simplex nozzle characterized as flow number 0.4 will be utilized. The injection pressures will range from 0.3–4Mpa while altering the surface tension from 72 to 28mN/m. By applying Phase Doppler Particle Anemometry (PDPA) which is a non-intrusive laser diagnostic technique, the differences in spray characteristics due to spray surface tension can be highlighted. The average droplet diameter decreases for a low surface tension fluid in the axial direction in comparison to pure water. The average velocity of droplets is surprisingly lower in the same spray zone. Measurements made in the radial direction show no significant changes, but at the locations close to the nozzle, water droplets have larger diameter and velocity. The results indicate the breakup and coalescence regimes have been altered when surface tension is lowered. A decrease in surface tension alters the breakup length while increasing the spray angle. Moreover, higher injection pressure shortens the breakup length and decrease in overall diameter of the droplets. By performing this experimental study the fundamentals of spray dynamics, such as spray formation, liquid breakup length, and droplet breakup regimes can be observed as a function of surface tension and how a surrogate fuel compares with a real fuel for experimental purposes. This knowledge potentially will lead to designing a better atomizer or new biofuels.

Spray Distribution of Plain Orifice Atomizer in Preheated Air Flow

2014 ◽  
Vol 1070-1072 ◽  
pp. 1911-1916
Author(s):  
Jia Xing Qian ◽  
Yu Ying Liu ◽  
Yi Xie ◽  
Zhi Wei Peng
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Momentum Flux ◽  
Air Flow ◽  
Flux Ratio ◽  
Spray Angle ◽  
Flow Temperature ◽  
Jet Breakup ◽  
Spray Distribution ◽  
Spray Field

An experiment by taking photos of the spray field behind plain orifice atomizer was conducted to study its atomization in preheated air flow. The air flow condition was 0.14~0.2 Mach number and 300~400°C. Fuel-to-air momentum flux ratioQvaried from 0.4 to 9, and Weber numberWecovered the range of 60~140. Photos were analyzed by Matlab image processing toolbox. The results indicate that under the experiment conditions: (1) Under the same temperature, jet breakup length increases withQincreasing, and decreases with the increase ofWe. (2) As the air flow temperature increases from 300°C to 400°C, jet and air flow interaction affect the liquid column breakup more greatly than surface tension. (3) Under the same temperature, spray angle increases with the increase ofQ. (4) As the air flow temperature increases from 300°C to 400°C, evaporation affects the atomization more greatly than pneumatic nebulization.

scholarly journals Experimental Study of Primary Atomization Characteristics of Sonic Air-Assist Atomizers

2021 ◽  
Vol 11 (21) ◽  
pp. 10444
Author(s):  
Raghav Sikka ◽  
Knut Vågsæther ◽  
Dag Bjerketvedt ◽  
Joachim Lundberg
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Water Pressure ◽  
Research Work ◽  
Spray Angle ◽  
Flow Rates ◽  
Breakup Length ◽  
Mass Flow Rates ◽  
Sheet Breakup ◽  
Atomization Characteristics

The present study compares two twin-fluid atomizer concepts based on the airflow (shock waves) pattern obtained through shadowgraph imaging for atomization of water with a low air/water pressure supply. The research work was conducted using the backlight imaging technique for converging (sonic) and converging–diverging (supersonic) air-assist atomizers with a 3.0 mm (throat) diameter. An annular sheet of thicknesses 70 µm and 280 µm with a high-speed air-core was employed to study the breakup dynamics for different water mass flow rates (100–350 kg/h) and air mass flow rates (5–35 kg/h). Different sheet breakup patterns were identified as the function of the ALR ratio (air-to-liquid mass flow), liquid Weber number (WeL), and Reynolds number (Reg). Different breakup modes extend from canonical Rayleigh bubble breakup, ligament-type breakup, to the pure pulsating breakup via annular sheet disintegration. The sheet breakup dynamics were studied in terms of spray angle and breakup length. With higher ALR values, breakup length showed a decreasing trend, while spray angle showed an increasing trend in the converging and converging–diverging (CD) air-assist atomizers, respectively, owing to the drastic difference in the jet flow dynamics.

Simulation of Laminar Liquid Jets in Gaseous Crossflow Before the Onset of Primary Breakup

2011 ◽  
Author(s):  
C.-L. Ng ◽  
K. A. Sallam
Keyword(s):  
Experimental Data ◽  
Fuel Injection ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Jet Breakup ◽  
Primary Breakup ◽  
Density Ratios ◽  
First Time ◽  
Two Sides ◽  
Reduced Pressures

The deformation of laminar liquid jets in gaseous crossflow before the onset of primary breakup is studied motivated by its application to fuel injection in jet afterburners and agricultural sprays, among others. Three crossflow Weber numbers that represent three different liquid jet breakup regimes; column, bag, and shear breakup regimes, were studied at large liquid/gas density ratios and small Ohnesorge numbers. In each case the liquid jet was simulated from the jet exit and ended before the location where the experimental data indicated the onset of breakup. The results show that in column and bag breakup, the reduced pressures along the sides of the jet cause the liquid to move to the sides of the jet and enhance the jet deformation. In shear breakup, the flattened upwind surface pushes the liquid towards the two sides of the jet and causing the gaseous crossflow to separate near the edges of the liquid jet thus preventing further deformation before the onset of breakup. It was also found out that in shear breakup regime, the liquid phase velocity inside the liquid jet was large enough to cause onset of ligament formation along the jet side, which was not the case in the column and bag breakup regimes. In bag breakup, downwind surface waves were observed to grow along the sides of the liquid jet triggered a complimentary experimental study that confirmed the existence of those waves for the first time.

Experimental comparison of the spray atomization of heavy and light fuel oil at different temperatures and pressures for pressure-swirl injector

2021 ◽  
pp. 095765092199437
Author(s):  
Elyas Rostami ◽  
Hossein Mahdavy Moghaddam
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Diesel Fuel ◽  
Temperature Increase ◽  
Liquid Film Thickness ◽  
Fuel Oil ◽  
Spray Angle ◽  
Breakup Length ◽  
Fuel Atomization ◽  
Mean Diameter

In this study, the atomization of heavy fuel oil (Mazut) and diesel fuel at different pressures is compared experimentally. Also, the effects of temperature on the Mazut fuel atomization are investigated experimentally. Mass flow rate, discharge coefficient, wavelength, liquid film thickness, ligament diameter, spray angle, breakup length, and sature mean diameter are obtained for the Mazut and diesel fuel. Fuels spray images at different pressures and temperatures are recorded using the shadowgraphy method and analyzed by the image processing technique. Error analysis is performed for the experiments, and the percentage of uncertainty for each parameter is reported. The experimental results are compared with the theoretical results. Also, Curves are proposed and plotted to predict changes in the behavior of atomization parameters. Diesel fuel has less viscosity than Mazut fuel. Diesel fuel has shorter breakup length, wavelength, liquid film thickness, and sature mean diameter than Mazut fuel at the same pressure. Diesel fuel has a larger spray angle and a larger discharge coefficient than Mazut fuel at the same pressure. As the pressure and temperature increase, fuel atomization improves. The viscosity of Mazut fuel is decreased by temperature increase. As the fuel injection pressure and temperature increase, breakup length, wavelength, liquid film thickness, and sature mean diameter decrease; also, spray angle increases.

Experimental Study on Jet Breakup Behavior With Surface Solidification

2010 ◽  
Author(s):  
Takashi Wada ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Yuta Uchiyama ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Size Distribution ◽  
Reactor Vessel ◽  
Image Processing Technique ◽  
Core Material ◽  
Dominant Factor ◽  
Sodium Coolant ◽  
Molten Material ◽  
Breakup Length ◽  
Jet Breakup ◽  
Median Diameter

For the safety design of the Fast Breeder Reactor (FBR), the Post Accident Heat Removal (PAHR) is required when a hypothetical Core Disruptive Accident (CDA) occurs. In the PAHR, it is strongly required that the molten core material can be cooled down and solidified by the sodium coolant in the reactor vessel. There is high possibility for molten material to be ejected as a liquid jet into sodium coolant in the reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant or not, it is necessary to understand the interaction between molten core material and coolant such as jet breakup and fragmentation behavior in coolant. The jet breakup behavior is the phenomenon that the front of molten material breaks up in coolant. To clarify the mechanism of jet breakup and fragmentation during the CDA for the FBR, it is necessary to understand the correlation between jet breakup lengths and size distribution of fragments when molten material jet interacting with coolant. The objective of the present study is to clarify the dominant factor of the jet breakup length and the size distribution of fragments experimentally. Molten jet of U-alloy 138 is injected into water as simulated core material and coolant by free-fall. The density ratio of core material and coolant is almost same as that of the real FBR system. The jet breakup behavior as interaction of molten material with coolant is observed with high speed video camera. Front velocity of the molten material jet is estimated by using the image processing technique. It suddenly decreases when the jet fall into the coolant. The jet breakup length estimated from observed images is compared with the breakup theories to understand the effect of experimental parameters for the jet breakup length. The solidified fragments are gathered and classified in size, and the mass in each size is measured. Median diameter is obtained from the mass distribution of the fragments. In comparison with interfacial instabilities, the median diameter of fragments shows the independent of relative velocity. The jet breakup lengths and median diameters compared with existing theories is discussed.

Jet Breakup and Droplet Formation in Immiscible Liquid-Liquid System

2016 ◽  
Author(s):  
Shimpei Saito ◽  
Yuzuru Iwasawa ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Tetsuya Kanagawa ◽  
...  
Keyword(s):  
Weber Number ◽  
Droplet Diameter ◽  
Droplet Formation ◽  
Liquid System ◽  
Immiscible Liquid ◽  
Satellite Droplet ◽  
Breakup Length ◽  
Jet Breakup ◽  
Fundamental Process ◽  
Median Diameter

Mitigative measures against the event of a core disruptive accident (CDA) are of the importance from the viewpoint of safety of a sodium-cooled fast reactor (SFR). If the CDA occurs, the so-called post-accident heat removal must be surely achieved. The present study focuses on the scenario that the molten materials are injected into the lower plenum as jets. The jet breakup behavior during the CDA will be very complicated. Therefore, a specialized study on the fundamental process during the jet breakup is believed to be an effective approach. The aim of this paper is to understand the fundamental process of hydrodynamic interaction of jet breakup and droplet formation Using the immiscible liquid-liquid system, water and silicon oil as the test fluids, visualization via high-speed videography was performed. From the visualization results, the breakup length and droplet diameter were measured by image processing. The experimental data were scaled with ambient Weber number. When the Weber number was smaller than 1, the droplet diameter was close to the nozzle diameter, and distribution of droplet size was not observed. When the Weber number exceeded 1, the breakup length became longer and the generated droplet diameter possessed a distribution with two peaks due to satellite droplet formation. In both cases, the droplet formed at the leading edge of jet. In case that Weber number is around 100, the droplets were formed by entrainment of interfacial wave at jet side. From the mass median diameter data, we can see that the increase of the Weber number caused the decrease of median diameter and the increase of the width of the distribution.

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