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1. High-Fidelity Modeling and Simulation of Primary Breakup fo a Gasoline Surrogate Jet

   Zhang, Bo ; Ling, Yue ( May 2019 , Proc. ILASS-Americas 30th Annual Conference on Liquid Atomization and Spray Systems 30th Annual Conference on Liquid Atomization and Spray Systems)

   In the present work, we model and simulate the injection and atomization of a gasoline surrogate jet by detailed numerical simulation. The surrogate fuel has a low volatility and thus no phase change occurs in the process. The nozzle geometry and operation conditions are similar to the Engine Combustion Network (ECN) “Spray G”. We focus the present study on the near field where inter-jet interaction is of secondary importance. Therefore, we have considered only one of the eight jets in the original Spray G injectors. The liquid is injected from the inlet into a chamber with stagnant gas. A tangential component of velocity is introduced at the inlet to mimic the complex internal flow in the original spray G injector, which leads to the jet deflection. A parametric study on the inlet tangential velocity is carried out to identify the proper value to be used. Simulations are performed with the multiphase flow solver, Basilisk, on an adaptive mesh. The gas-liquid interface is captured by the volume-of-fluid method. The numerical results are compared to the X-ray experimental data for the jet deflection angle and the temporal variation of penetration length. The vortex dynamics in the near field are also presented by the assistance of the vortex-identification criterion. 

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2. Visualization of Internal Flow Dynamics in Counterflow Atomizers Using X-Ray Diagnostics and Laser Shadowgraphy

   Hoxie, A. ; Srinivasan, V. ; Johnson, E. ; Kastengren, A. ( May 2022 , ILASS-Americas 32nd Annual Conference on Liquid Atomization and Spray Systems)

   Experiments were carried out to observe the flow inside counterflow atomizers over a range of operating conditions and fluid properties. Liquids used were water and propylene glycol, while the gas was either air or helium. Liquid flow rates ranged from 10 ml/min to 40 ml/min, with gas liquid ratio (GLR) ranging from 0.1 to 0.6. The primary experiments used the 7-BM line of the Advanced Photon Source in Argonne National Laboratories with a 2.6 mm atomizer produced from (Poly)Ethyl-Ether-Ketone (PEEK). The X-Ray beam was operated in phase contrast mode, leading to interference patterns near the gas-liquid interface and enabling a qualitative understanding of the flow structure. Complementary optical work applied laser shadowgraphy to a 1 mm orifice atomizer constructed with quartz capillary tubing. A diffuse pulsed Nd:YAG laser backlight captured instantaneous gas-liquid interface positions in the internal flow. With both techniques, two distinct flow behaviors are observed corresponding to low and high GLR values. At low GLR, the inertia of the injected gas is insufficient to penetrate the liquid downflow. The gas stream entering the mixing chamber in the upstream direction is immediately deflected by the denser liquid and enters the discharge tube around a central liquid jet, which is sheared and accelerated by the surrounding gas, leading to breakup. A distinct frequency of jet breakup is observed inside the discharge tube, with the liquid jet oscillating and fragmenting against the walls. The situation at high GLR is quite different, however, as the incoming gas stream asymmetrically penetrates upstream into the mixing chamber, taking the form of a high-speed jet confined along one wall, and displaying a flapping instability as it encounters the liquid flowing downstream. This flapping causes violent mixing, resulting in a highly disturbed interface, along with the generation of liquid ligaments and gas bubbles. This two-phase mixture enters the discharge tube with no liquid jet formation evident for this case. The transition between these two regimes is explored by changing the liquid viscosity and gas molar mass, and weak sensitivity to fluid properties is observed. Further, quantitative image analysis techniques applied to the low and high GLR cases allow extraction of the frequencies of the liquid jet in the discharge tube at low GLR, as well as the flapping mode at high GLR. 

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3. Investigation of the evaporation and fuel property effect on liquid jets in supersonic crossflow

   Zou, Shufan ; Zhou, Dezhi ; Yang, Suo. ( May 2021 , 12th U.S. National Combustion Meeting)

   null (Ed.)

   Due to the longer auto-ignition time with liquid fuels compared with hydrogen, the understanding of interaction of shock waves with sprays and the subsequent vapor mixing is significant to design ramjets/scramjets with liquid fuel sprays. In this study, an Eulerian-Lagrangian framework is developed based on the OpenFOAM platform. In this solver, detailed multi-component transport models for Eulerian gas-phase species properties are included. In addition, Lagrangian spray break-up, atomization and evaporation models are added to simulate liquid phase. In addition, an equilibrium wall function is added to model the near-wall properties. The newly developed solver is used to conduct large eddy simulations (LES) on non-reactive liquid jets in supersonic crossflow (JISCF) with liquid sprays. The liquid penetration length are compared with the experimental data, showing a very good agreement. Effects of evaporation and fuel properties (e.g., heat capacity and enthalpy of evaporation) on penetration length, temperature, Sauter mean diameter (SMD) and volumetric parcel flux are discussed in this study. It is shown that evaporation effects primarily show up in the temperature field. For n-heptane sprays, such impact could be conducted to other properties of the flow field like spray plume size, particle size distribution and volumetric flux, which is caused by the smaller enthalpy of evaporation and heat capacity comparing to water. Full version of this paper has been published as a journal article: Shufan Zou, Dezhi Zhou, Suo Yang, “Effects of Evaporation and Fuel Properties on Liquid Jets in Supersonic Crossflow: a Computational study using a compressible Eulerian-Lagrangian solver”, Atomization and Sprays 30 (9) (2020) 675-696. https://doi.org/10.1615/AtomizSpr.2020034860 

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4. The effect of nozzle internal flow on spray atomization

   https://doi.org/10.1177/1468087419875843  

   Agarwal, Arpit ; Trujillo, Mario F ( January 2020 , International Journal of Engine Research)

   The effect of nozzle surface features on the overall atomization behavior of a liquid jet is analyzed in the present computational work by adopting three representative geometries, namely a single X-ray tomography scan of the Engine Combustion Network’s Spray A nozzle (Unprocessed), a spline reconstruction of multiple scans (Educated), and a purely external flow configuration. The latter configuration is often used in fundamental jet atomization studies. Numerically, the two-phase flow is solved based on algebraic volume-of-fluid methodology utilizing the OpenFoam solver, interFoam. Quantitative characterization of the surface features concerning the first two geometries reveals that while both of them have similar levels of cylindrical asymmetries, the nozzle configuration pertaining to the Unprocessed geometry has much larger surface features along the streamwise direction than the Educated geometry. This produces for the Unprocessed configuration a much larger degree of non-axial velocity components in the flow exiting the orifice and also a more pronounced disturbance of the liquid surface in the first few diameters downstream of the nozzle orifice. Furthermore, this heightened level of surface destabilization generates a much shorter intact liquid core length, that is, it produces faster primary atomization. The surprising aspect of this finding is that the differences between the Unprocessed and Educated geometries are of [Formula: see text](1) μm, and they are able to produce [Formula: see text](1) mm effects in the intact liquid core length. In spite of more pronounced atomization for the Unprocessed geometry, the magnitude of the turbulent liquid kinetic energy is roughly the same as the Educated geometry. This highlights the important role of mean field quantities, in particular, non-axial velocity components, in precipitating primary atomization. At the other end of the spectrum, the external-only configuration has the mildest level of surface disturbances in the near field resulting in the longest intact liquid core length. 

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5. High-fidelity simulation of a rotary bell atomizer with electrohydrodynamic effects

   Krisshna, Venkata ; Owkes, Mark ( August 2021 , ICLASS 2021, 15th Triennial International Conference on Liquid Atomization and Spray Systems)

   Rotary Bell Atomizers (RBA) are extensively used as paint applicators in the automotive industry. Atomization of paint is achieved by a bell cup rotating at speeds of 40k-60k RPM in the presence of a background electric field. Automotive paint shops amount up to 70% of the total energy costs [Galitsky et. al., 2008], 50% of the electricity demand [Leven et. al., 2001] and up to 80% of the environmental concerns [Geffen et al., 2000] in an automobile manufacturing facility. The atomization process in an RBA affects droplet size and velocity distribution which subsequently control transfer efficiency and surface finish quality. Optimal spray parameters used in industry are often obtained from expensive trial-and-error methods. In this work, three-dimensional near-cup atomization (primary and secondary breakup) are simulated computationally using a high-fidelity volume-of-fluid transport scheme that includes an electrohydrodynamic effects. The influence of fluid properties (viscosity ratio, flow rate and charge density), nozzle rotation rate and bell potential on atomization are investigated by performing a parametric study. This cost-effective method of research aims to identify the ideal spray parameters to achieve maximum transfer efficiency. 

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