Liquid Jet In Crossflow Research Articles

Multiphase flow and mixing quantification using computational fluid dynamics and magnetic resonance imaging

This paper investigates the current challenges and practices of quality measurement in the oil & gas industry. It particularly focuses on automatic pipeline sampling of petroleum liquids according to ISO 3171. The problem is tackled using innovative diagnostic techniques, advanced design optimisation tools and a new mixing system that uses a Liquid Jet In Cross Flow (LJICF) configuration. First, a 2.5″ diameter small multiphase flow loop (SMPFL) was developed and magnetic resonance (MR) was utilised to characterise the mechanistic behaviour of mixing and the mixing efficiency of various nozzles. Second, a computational fluid dynamics (CFD) model was developed and validated using MR measurements on the SMPFL. The CFD model was then used to optimise the nozzle design as well as the design of a 10” nominal diameter large multiphase flow loop (LMPFL). The LMPFL is a well instrumented facility and was used to conduct mixing experiments on low velocity, low density and low viscosity fluids flowing in a horizontal pipe, which constitute challenging conditions for a mixing device to create homogeneous mixture. To quantify the homogeneity of the mixture created by the new mixing system on the LMPFL, a multiport profile proving (MPP) technique was developed and used to conduct water injection testing in compliance with ISO 3171 and API 8.2 standards. The water volume fraction (WVF) determined by the MPP had low relative error when compared to the mean WVF measured by the water cut meters and samples analysed using Coulometric Karl-Fischer (KF). Additionally, in an earlier study [1], the MPP measurement was able to detect a density gradient across the diameter of the pipe, making it an appropriate method to judge the homogeneity of the mixture. Therefore, the new mixing system together with the MPP technology shows real promise as an effective sampling and proving system for the petrochemical industry.

Primary atomization of a turbulent liquid jet in crossflow: a comparison between VOF and FGVT methods

The primary atomization of a turbulent liquid jet in crossflow was investigated using a mathematical, numerical and computational model. A comparison between the standard volume of fluid (VOF) method and the fine grid volume tracking (FGVT) method was reported. The FGVT method advects the interface between two fluids using a finer grid than the employed by the standard VOF method, and according to the literature, it provides a better interface resolution. Simulations were performed using adaptive mesh refinement in a three-dimensional domain subjected to gravitational field using the in-house code MFSim. The flow was modeled using an Eulerian–Lagrangian approach to capture the interface. The interface was tracked initially with VOF or FGVT methods until the initial breakup. Broken off, small-scale nearly spherical drops were transferred into the Lagrangian point particle description. Column breakup and shear breakup modes were observed on the liquid jet. Drops were small as one-hundredth the size of the injector diameter. The model was validated against experimental correlations for the liquid jet column trajectory, and the droplet size distribution was compared to a previous numerical study from the literature. In addition, the breakup mechanisms predicted were qualitatively compared to those in previous reports. The results of the liquid column trajectory from the simulations performed presented low differences with the literature for both methods tested. According to the numerical results obtained from the computational simulations, the liquid column trajectory was well captured and the droplet size distribution was similar to the literature; however, the FGVT method provided higher accuracy compared to VOF method. The two main breakup modes were identified, namely the column breakup with Kelvin–Helmholtz instabilities and the surface breakup with the formation of multiple ligaments which later lead to droplet formation. The FGVT method provided a more detailed interface contour and improved the number of droplets converted from the Eulerian to the Lagrangian approach compared to the standard VOF method. On the other hand, the FGVT method presented relatively higher computational costs compared to VOF. Therefore, the FGVT method presented a higher interface quality and allowed a larger number of droplet conversion to the Lagrangian approach compared to the VOF method, even though the simulation run time using VOF was lower than with FGVT.

Liquid–solid two-phase jet in a turbulent crossflow: Experiments and simulations

Compared to single-liquid and liquid–liquid jets in crossflow (JICF), liquid–solid two-phase JICF is rarely studied. An experimental setup has been developed to investigate a vertical jet of liquid–solid mixture in water turbulent crossflow at Re≈2.2·104 over 4s period. Rigid micro particles were injected vertically in a horizontal pure-water turbulent flow. The jet trajectory, penetration and the particles concentration were recorded via a high resolution camera with particles tracking technique. Three-dimensional CFD simulations have been conducted using two different Eulerian models: two-Fluid model in commercial code, and a new mixture model solver developed in opensource to predict the hydrodynamics, jet trajectory and particles transport. A modified-k−ε model (for particle induced turbulence, and turbulent dispersion), and a modified-buoyant-k−ε model have been employed in the commercial and open-source codes, respectively. At t≤2.5s near the jet's entry (x/h>0.2, y/h<0.15), both models predicted local ϕ values similar to the experiments. While at t=2.5s, only the mixture model predicted the jet's bend with ϕ≈0 in the zone (x/h>0.2, y/h<0.15) as in the experiment. The mixture model constitutes a good compromise for conducting global predictions of suspension JICFs at a computational cost that is reduced by a factor of the order of O(∼10).

A COMPUTATIONAL PROTOCOL FOR SIMULATION OF LIQUID JETS IN CROSSFLOWS WITH ATOMIZATION

A COMPUTATIONAL PROTOCOL FOR SIMULATION OF LIQUID JETS IN CROSSFLOWS WITH ATOMIZATION

Improved hybrid model applied to liquid jet in crossflow

Spray formation in a liquid jet in air crossflow is investigated numerically using a hybrid approach for two cases: We=11 and We=53, where We is the air Weber number. The VOF method was used to solve the interaction between the liquid jet column and the air flow up to the primary breakup. The Eulerian liquid portion is converted to discrete Lagrangian drops by the use of source terms of mass and momentum and according to empirical correlations. The effects of two secondary breakup models, as well as two-way coupling with droplet-to-droplet collisions were evaluated in this work, in order to establish an improved hybrid model suitable to solve liquid jet in crossflow at low computational cost. The results were very satisfactory relating droplet velocity and mass fraction distribution for the lower Weber number case. For the higher Weber number case, the deviation of the numerical mass fraction distribution in comparison with the experimental one was less than 14×10−2. Improvement to the droplet size distribution was observed by using a new secondary breakup model, specially for the higher Weber number case.

Effect of Orifice Geometry on Column Trajectories of Liquid Jets in Crossflows

Effects of orifice geometry on liquid column trajectories of liquid jets in subsonic crossflows were experimentally studied. One circular and four elliptical plain-orifice injectors with different aspect ratios of 1/3 to 3, were designed and utilized. By changing the injection pressure drop from 1 bar to 6 bar with an increment of 1 bar, and thus the liquid–air momentum flux ratio from 15 to 106, back-lit spray photographs of liquid jets in crossflows were taken and then analyzed using an in-house code to detect the upper boundary and centerline of the liquid jet before the breakup point. Analytical liquid column trajectories for circular and elliptical liquid jets were derived through simple assumptions and compared with present experimental data. It was found that the aspect ratio affected the difference between the analytical drag coefficient and the experimental one. Novel empirical equations for liquid column trajectories of circular and elliptical liquid jets in crossflows were suggested as a function of equivalent orifice diameter, liquid–air momentum flux ratio and aspect ratio. The results showed that the present empirical equation for the circular orifice injector could be reasonably applied to the elliptical orifice injectors when the aspect ratio was below one.

Linear stability analysis of a liquid jet in a weak crossflow

In an effort to better understand the primary breakup mechanism of liquid jets in crossflow, a theoretical model for three-dimensional spatial linear stability of a viscous liquid jet injected in a weak gaseous crossflow is developed. The results are presented for the behavior of jet instabilities in the range of crossflow-to-jet momentum flux ratio of less than 0.01. In this range, the deformation of the liquid column allows a parallel base flow which is described by a modified viscous potential flow analysis. Focusing on the early stages of the jet evolution, a characteristic equation accounting for the growth of columnar waves is obtained and the most dominant wavelength and the corresponding growth rates are calculated. The predicted results for the asymptotic case of free jet flow are examined against the results available in the literature. Symmetric and asymmetric modes of liquid jet disturbance are investigated for a wide range of viscous, surface tension, and aerodynamic force ratios.

Experimental investigations of fuel preparation in a swirling airflow under realistic conditions without reaction in a combustor model with a point fuel source

This paper presents quantitative experimental results of non-reacting spray analysis inside a model combustor at realistic jet engine conditions based on a point fuel source and with using kerosene Jet A-1 for the first time. Therefore, two test conditions with combustor pressures of 0.4 and 1.2 MPa, air preheat temperatures of 440 and 740 K and fuel preheating temperatures of 358 and 467 K were investigated. The basis for this investigation was a specially made combustor model in combination with a burner model similar to a fuel-staged lean burner. The focus was on the main stage with a single decentralised point fuel source. This fuel entry is a liquid jet in cross flow (LJICF) with the jet direction normal to the main air flow. The velocity of the air flow was measured by Laser Doppler Anemometry (LDA). Phase Doppler Anemometry (PDA) was used for the simultaneous measurements of fuel drop size and velocity. Sauter mean diameter (SMD) distributions and drop size dependent velocities were shown for the different axial distances inside the model combustor and were discussed with respect to the distributions and the ability of fuel droplets to follow the airflow. The consequent findings of the drop dispersion were verified by Stokes numbers. The drop diameters, and therefore the Stokes numbers, are heavily dependent on test conditions. With values of 8 < SMD [μm] < 20, the drop sizes were accordingly small. For validating the liquid fuel combustion codes, the dataset is completed by histograms of drop size and the determined Rosin–Rammler (RR) parameters.

Liquid jet in crossflow – Effect of liquid entry conditions

The focus of the present article is to study the effect of liquid jet injection entry conditions on the structure of liquid jet in crossflow (JICF). The experiments are conducted over a range of liquid-to-air momentum ratios (Q ∼ 3–100) and aerodynamic Weber numbers (We = 17–89). Control over the exit conditions of the injected liquid is achieved through the usage of different L/D ratios of the nozzle of the plain-orifice atomizer. The geometrical parameter L/D is varied between 10 and 100 in order to obtain fully-developed laminar flow, transition and turbulent flow. High-speed imaging and Shadowgraphy are used to study the trajectory, drop-sizing and transient behaviour of the resultant spray. It is observed that the dependence of trajectory of the spray is not just limited to the momentum ratio, Q, but also requires correction factors with respect to the injection entry conditions, which are in turn related to L/D. The trajectory of the turbulent jet is found to be lower at all times when compared to that of a laminar jet for the corresponding conditions. This behaviour may be attributed to the inherent instabilities present in a turbulent jet as opposed to a perfectly laminar jet. Turbulent jets also observed atomize better, producing smaller droplets when compared to their laminar counterparts. Further, we also investigate the transient phenomena of the liquid jet breakup at different conditions with the aid of Proper Orthogonal Decomposition (POD) analysis. Distinct modes of breakup are captured for the laminar and turbulent cases.

A Review on Empirical Correlations for Jet/Spray Trajectory of Liquid Jet in Uniform Cross Flow

The empirical correlations for the prediction of jet/spray penetration of liquid jet in subsonic uniform crossflow are reviewed in this study. Considerable number of empirical correlations had been proposed by many investigators. It has generally known that the jet/spray trajectory of a liquid jet in a cross-flow is a function of the liquid to air momentum flux ratio and the normalized distance in the airstream direction from the injector. However, several researchers incorporated the Weber number, liquid-to-water or air viscosity ratio, pressure ratio or Reynolds number, temperature ratio in the empirical correlations. Two different classification methods of correlations, i.e. classification based on mathematic functional form and classification based on flow regime, are introduced in this study. The one classification of existing correlations based on functional form includes correlations in a power-law, logarithmic, and exponential forms, respectively. The other classification of previous correlations based on flow regime includes one, two and three regime, correlations. Correlations in a power-law functional form can be further divided into three groups such as momentum flux ratio, Weber number and other parameters forms. Correlations in logarithmic functional form can be also grouped as momentum flux ratio and Weber number forms. Most of the evaluation studies reported the significant discrepancies of predicted values by the existing correlations. The possible reasons for discrepancies will be summarized as measurement technique, assumptions made in defining terms in the liquid to air momentum flux ratio, difficulties in defining the boundaries of the liquid jets, turbulence level in the core and boundary layer of incoming jet and gas flows, nozzle/injector geometry and its position in the crossflow. However, it can be found from the several evaluation studies that the power-law functional form with momentum flux ratio and two regimes correlations provided relatively the best fit to experimental data.

Subcooled flow boiling in a microchannel with a pin fin and a liquid jet in crossflow

This experimental study presents subcooled flow boiling of an engineering fluid — HFE-7000 — downstream a single pin fin in a microchannel. A liquid secondary jet was introduced into the flow to examine its merits pertinent to heat transfer enhancement. It was found that for HFE-7000 high wall superheats (ΔT(sat,ONB)∼40°C) were required for the onset of nucleate boiling (ONB). Once boiling started, nucleate boiling dominated. Heat transfer coefficient increased monotonically with heat flux, independent of mass flux and jet injections. Secondary flow injection, which was previously found to be an affective single phase heat transfer enhancement technique, showed limited potential for fully developed nucleate boiling.

Breakup of Volatile Liquid Jet in Hot Cross Flow

Liquid jet in cross flow has been a widely studied subject although most of the experimental work has been carried out at ambient conditions. The present study involves the investigation of the behavior of an ethanol jet injected into a cross flowing air at elevated temperatures up to 428K. Spray parameters such as the trajectory and drop size distributions are measured and compared for cold and hot flow conditions. Experiments are conducted for a range of liquid-to-air momentum ratios (Q) ∼ 4 – 13 and for Aerodynamic Weber numbers (We) ∼ 15. Though most of the existing literature attributes the effect of elevated temperature on the effective change in Q due to density variation, the present study shows interesting observations where the results vary in spite of maintaining similar magnitudes of Q between cold and hot flow conditions. It is observed that a higher trajectory is consistently manifested by the ethanol jet at elevated temperatures as compared to that found at ambient temperatures. It is proposed that the physical parameter,density ratio, needs to be considered as an additional parameter to account for these differences. Therefore, a new trajectory correlation is proposed which is observed to match experimental data at different temperatures. The drop size measurements indicate considerable amount of evaporation of the fine droplets formed at the leeward portion of the resultant spray of ethanol jet in cross flow.

Pulsation in Bag Breakup of Round Liquid Jets in Crossflow

An experiment was conducted to investigate bag breakup process of round liquid jets in crossflow. The objective of this study is to research pulsation law. Specifically, this study measures the onset position of bag, the breakup position of bag, the breakup position of the jet. High-speed camera was used to observe the formation and breakup of bags. The diameter of the nozzle used in the experiment was 0.5mm, 0.8mm, 1mm. The test liquid was tap water. Wea number covers the range of 6~30, and liquid-to-air momentum flux ratio varied from 22 to 211. Present results indicate that in the direction perpendicular to the gas flow, the dimensionless pulsating amount of the onset point of bags (yonset/d) is linear to q, while the dimensionless pulsating amount of breakup point of bags (ybag/d) and the dimensionless pulsating amount of breakup point of the jet (yjet/d) is linear to ln (q). The dimensionless pulsating amount of these points in the direction of gas flow is irregular.

Breakup processes of pressure swirl spray in gaseous cross-flow

Injection of liquid fuel in cross flowing air has been a strategy for future aircraft engines in order to control the emissions. In this context, breakup of a pressure swirl spray in gaseous cross-flow is investigated experimentally. The atomizer discharges a conical swirling sheet of liquid that interacts with cross-flowing air. This complex interaction and the resulting spray structures at various flow conditions are studied through flow visualization using still as well as high speed photography. Experiments are performed over a wide range of aerodynamic Weber number (2–300) and liquid-to-air momentum flux ratio (5–150). Various breakup regimes exhibiting different breakup processes are mapped on a parameter space based on flow conditions. This map shows significant variations from breakup regime map for a plain liquid jet in cross-flow. It is observed that the breakup of leeward side of the sheet is dominated by bag breakup and the windward side of the sheet undergoes breakup through surface waves. Similarities and differences between bag breakup present in plain liquid jet in cross-flow and swirl spray in cross-flow are explained. Multimodal drop size distribution from bag breakup, frequency of bag breakup, wavelength of surface waves and trajectory of spray in cross-flow are measured by analyzing the spray images and parametric study of their variations is also presented.

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

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.

Empirical Correlations for Breakup Length of Liquid Jet in Uniform Cross Flow-A Review

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross are reviewed and chassified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and col-fied as constant form, momentum flux ratio form, Weber number form and other parameter form, repectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio. However, Weber number, liquid-to-air ciscosity ratio and density ritio. Reynolds number of ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrenpancies of predicted values by the existing correlations even though many correlation have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location ete. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

Bag Breakup of Turbulent Liquid Jets in Crossflows

An experiment was conducted to investigate the bag breakup process of round liquid jets in crossflows. A highspeed camera was used to observe the formation and breakup of bags in a water jet from a 1.0 mm diameter nozzle with aWeber number in the range of 11 36 and the liquid-to-air momentum ratio from 11 to 95. An analysis of the force balance on bags was conducted and a criterion for bag formation is obtained. The diameter of the bag ring tube was predicted according to a reduced-order model, and the predicted results agree qualitatively well with the experiments. Present results indicate that the normalized basal ring diameter, ring tube diameter, and the bag onset time are all constants, while the onset length of bags normalized by the initial jet diameter varieswith the liquid-to-air momentumratio and jetReynolds number.The bagbreakup lengthdecreases linearlywith the increase of theWeber number, and is independent of the liquid jet velocity. The streamwise distance of the breakup location from the nozzle exit is a constant, while the cross-stream distance increases with the liquid-to-air momentum ratio.

주류유동에서 단일 및 이중 수직분사 분무특성

연소실 내의 주류 공기유동에 미치는 영향을 최소화하면서 미립화 및 혼합특성을 향상시키기 위한 방법으로 주류공기 유동에 대해 수직방향의 연료분사 방식이 실용 엔진에서 많이 사용되고 있고, 관련 연구도 활발히 보고되고 있다. 본 연구는 가스터빈이나 램젯 엔진에서 사용되고 있는 수직분사의 분무특성은 실험적으로 조사하고, 단일 및 이중 수직분사에 따른 침투길이를 측정함으로써 선행연구에 의해 보고된 결과와 비교하였다. 또한 압력과 모멘텀 플럭스비 변화에 따른 침투길이, 분무입경 등의 분무 특성을 연구하였다. 특히, 이중 수직분사의 침투길이는 단일 수직분사의 침투길이에 비해 전단의 수직분사의 영향으로 후단의 수직분사 길이가 약 20% (Lh=4mm) 증가함을 확인할 수 있었다.

Multiple Injector Model for Primary Breakup of a Liquid Jet in Crossflow

R ADIAL injection of liquid jets into a high-velocity and hightemperature cross stream at elevated pressures has various applications in fuel injection systems and advanced aircraft engines, such as gas turbines, afterburners, augmenters, and various combustors. Since this type of fuel injection can improve the fuel atomization and vaporization characteristics, it is commonly used in turbojet augmenter sections and rich burn-quick quench-lean burn, lean premixed prevaporized, and ramjet and scramjet combustion systems. To date, several analytical, experimental, and numerical studies have investigated various characteristics of the jet-incrossflow (JICF) atomization. Experimental studies have developed several correlations that predict various features of the JICF atomization. Because of the nature of the experimental studies, the results and correlations proposed by each study aremainly applicable within the specific parameter ranges of that study. The JICF atomization problem involves very complex physics, such as strong vortical structures, small-scale wave formation, stripping of small droplets from the jet surface, and formation of ligaments and droplets with a wide range of sizes. The JICF atomization process can be divided into three main phases: 1) injection of a liquid jet perpendicular to a gaseous crossflow, 2) deflection and deformation of the jet, and 3) disintegration of the jet into ligaments and droplets. The atomization mechanism is believed to start by the growth of waves that form on the surface of the jet after injection from the nozzle. The relative velocity between the gas and the liquid phase amplifies the surface waves up to the point where the jet breaks up into smaller droplets. Apart from the three phases mentioned above, more complex small-scale physical processes are involved in the problem, such as particle stripping from the jet. From the computational point of view, the complete numerical simulation of such a problem, resolving most important flow scales on the Eulerian frame, is still expensive, especially for industrial applications. These issues signal the demand for some simpler yet reliable models that can be used for industrial design purposes and, at the same time, take into account the flow conditions and the physical properties of the liquid and gas phases. In this paper, we review some of the challenges involved in modeling of the JICF atomization and propose a model that provides realistic predictions of the jet atomization in crossflows. Our focus will be turbulent jets. To validate the model, we perform several experiments. We first validate our experiments by showing that their resulting correlations are in good agreement with the available literature. Then, we use our experimental results to validate our model results. We decided to perform our own experiments rather than making comparisons to previous studies for twomain reasons. First, we needed spatial droplet size and velocity distributions downstream of the nozzle. Although there are studies available that provide that information (such asWu et al. [1]), they mostly consider laminar jets, whereas we are focused on turbulent jets. Second, performing our own experiments provides us with all the information we need to set up our simulations from initial flow parameters to geometrical specifications. A review of some of the experimental studies devoted to studying various characteristics of the JICF problem can be found in Mashayek andAshgriz [2].Wewill present a brief review on some of the experimental and theoretical literature more relevant to the purposes of this paper. One of the first models for atomization of a liquid phase injected normal to a gas stream was that of Reitz [3]. He modeled the atomization by estimating the wavelength and growth rate of the surface waves and relating the breakup droplet sizes to the wavelengths. Liu et al. [4] also modeled a liquid jet injected normal to a gas stream by successive injection of droplets into the gas phase. They did not consider the stripping of droplets from the surface of the jet and Received 24 April 2010; revision received 6 April 2011; accepted for publication 8 April 2011. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0001-1452/11 and $10.00 in correspondence with the CCC. ∗Department of Physics, 60 St. George Street. Department of Civil Engineering, 35 St. George Street. ; Department of Mechanical and Industrial Engineering, King’s College Road (Corresponding Author). AIAA JOURNAL Vol. 49, No. 11, November 2011

Primary atomization of a liquid jet in crossflow

In this fluid dynamics video, we present a visualization of the primary atomization of a turbulent liquid jet injected into a turbulent gaseous crossflow. It is based on a detailed numerical simulation of the primary atomization region of the jet using a finite volume, balanced force, incompressible LES/DNS flow solver coupled to a Refined Level Set Grid (RLSG) solver to track the phase interface position. The visualization highlights the two distinct breakup modes of the jet: the column breakup mode of the main liquid column and the ligament breakup mode on the sides of the jet and highlights the complex evolution of the phase interface geometry.