Convergent Science

Spray Simulations

CONVERGE™ CFD software comes equipped with a rich set of physical models to model liquid sprays. Included in this are models for:

  • Primary atomization
  • Collision and coalescence
  • Droplet breakup
  • Droplet heating and vaporization (including multicomponent distillates)
  • Liquid wall film

CONVERGE™ has sophisticated meshing technologies which automatically add mesh elements when and where they are most needed to minimize the grid effects on the spray results. Convergent Science, Inc. has extensive experience in setting up sprays for both RANS and LES and the best practice settings are readily available.

The CONVERGE™ spray models work seamlessly with the SAGE detailed chemistry solver. Whether solving for a reacting or non-reacting flow, CONVERGE™ CFD is the code of choice to model any liquid spray.

The following video demonstrates the ability of the CONVERGE™ code to capture cycle-to-cycle variations using a Dynamic structure LES model. This work was performed in collaboration with Argonne National Laboratory.

 

 

Historically, Lagrangian spray models begin downstream of the nozzle exit and do not account for nozzle flow dynamics. To improve accuracy associated with the spray boundary conditions, Convergent Science,Inc. is also actively researching nozzle flows. This often involves using the integrated volume of fluid (VOF) and cavitation models available in CONVERGE™. These models work in harmony with other standard CONVERGE™ features such as moving zones and Adaptive Mesh Refinement (AMR). As is the case with other applications, AMR optimizes the mesh by placing cells when and where they are most needed to minimize meshing related errors while maximizing computational productivity.

As an example, the void fraction (top is experiment, bottom is CONVERGE™) for a cavitating Winklhofer nozzle is shown below. The cavitating regions are well predicted by the CONVERGE simulations.

 

cavitating

 

CONVERGE™ can readily handle moving boundaries. The needle motion profile (on-axis and off-axis) can be specified and CONVERGE™ automatically makes a new mesh every time-step during the transient simulation. This makes the setup of cases with moving boundaries quick and easy. This approach can be used to simulate the moving pintle valve of a fuel nozzle as shown below.

 

 

The needle lift profile is specified in CONVERGE™ based on phase-contrast x-ray experiments at Argonne National Laboratory (“Engine Combustion Network (ECN): Measurements of Nozzle Geometry and Hydraulic Behavior”, A. L. Kastengren, F. Z. Tilocco, C. F. Powell, J. Manin, L. M. Pickett, R. Payri, T. Bazyn, Atomization & Sprays, Accepted for Publication March 2013).

Researchers have noticed that in practice, the needle does not move linearly. Rather, the motion has some eccentricity and lateral motion. It is believed that this non-linear motion may be significant in the spray development. Convergent Science, Inc and Argonne National Laboratory are actively researching this topic.

 

 

 

In summary, CONVERGE™ CFD is the code of choice for simulating Lagrangian sprays and internal nozzle flows.

 

ACKNOWLEDGMENTS

The work at Argonne National Laboratory was supported by the U.S. Department of Energy’s Vehicle Technologies Program under Gurpreet Singh.

We gratefully acknowledge the computing resources provided on “Fusion,” a 320-node computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory.

Selected Bibliography

P.K. Senecal, E. Pomraning, K.J. Richards, S. Som, “An investigation of grid convergence for spray simulations using an LES turbulence model,” SAE Paper No. 2013-01-1083, SAE 2013 World Congress, Detroit, April 2013.

“VALIDATION OF A THREE-DIMENSIONAL INTERNAL NOZZLE FLOW MODEL INCLUDING AUTOMATIC MESH GENERATION AND CAVITATION EFFECTS”, Submitted to the Proceedings of ASME 2013 Internal Combustion Engine Fall Technical Conference ICEF 2013 October 13-16, 2013, Dearborn MI, USA ICEF2013-19167, Hongwu Zhao, Shaoping Quan, Meizhong Dai, Eric Pomraning, P. K. Senecal, Qingluan Xue, Michele Battistoni; and Sibendu Som.

Q. Xue, M. Battistoni, S. Som, D.E. Longman, H. Zhao, P.K. Senecal, E. Pomraning, “Three-dimensional Simulations of the Transient Internal Flow in a Diesel Injector: Effects of Needle Movement,” 25th Annual Conference on Liquid Atomization and Spray Systems, Pittsburg, PA, May 2013.

 

 

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