=Paper=
{{Paper
|id=Vol-452/paper-22
|storemode=property
|title=Simulation of primary breakup for Diesel spray with phase transition
|pdfUrl=https://ceur-ws.org/Vol-452/poster2.pdf
|volume=Vol-452
}}
==Simulation of primary breakup for Diesel spray with phase transition==
<pdf width="1500px">https://ceur-ws.org/Vol-452/poster2.pdf</pdf>
<pre>
         Simulation of Primary Breakup for Diesel Spray with Phase Transition
                               1
                       P. Zeng* , B. Binninger , P. Peters and M. Herrmann
                                              1           1                2


                                          1
                                          Institute of Combustion Technology
                                         RWTH Aachen University, Germany
                                2
                                  Department of Mechanical and Aerospace Engineering
                                    Arizona State University, Tempe, Arizona, USA

Diesel spray breakup and evaporation determine the characteristics of the fuel-air mixing for mixture-fraction based
combustion models. An accurate spray breakup model is a key point for their predictability, especially primary
breakup. Different from the popular droplet-particle based Langragian models, we resolve the liquid phase in Eulerian
frame. In addition, a level-set method is employed to capture the two-phase flow interface, including surface tension
force. The phase transition is taken into account by introducing surface regression velocity into the level-set transport
equation. Through 3D direct numerical simulation (DNS), we can have insight in the formation of ligaments and
droplets for diesel direct injection. As experimental results are still difficult to obtain for dense spray, the simulation
result reveals the spray primary breakup with the help of modern supercomputers in first principle.


Refined level-set grid method                                  the large eddy simulation (LES) will be done in the
Spray primary breakup is a multiscale problem that             future.
involves a wide range of time and length scales. In
order to balance the efficiency and accuracy of the
simulation model, the Refined Level-Set Grid
(RLSG) method has been designed [1]. As Fig. 1
illustrates, the interface evolution level-set
equation is solved by using the RLSG method on
an auxiliary, high-resolution equidistant Cartesian
grid, while the Navier-Stokes equations governing
both gaseous and liquid phase are solved on their
own unstructured computational grid.




       Figure 1: Refined level-set grid method [1]

Summary and Outlook
Figure 2 shows snapshots of the turbulent liquid jet
and droplets generated by primary breakup [2]. In
this work, an extension of the level-set method for            Figure 2: Snapshots; from top to bottom: t = 4µs, t = 6µs,
primary breakup with phase transition is presented.                             t = 8µs, t = 10µs [2]
The surface regression velocity is introduced and
the interface evolution equation is derived. This              References
model is applied on a direct numerical simulation of           [1] M. Herrmann. A balanced force refined level set grid
a turbulent diesel injection. Though there are many            method for two- phase flows on unstructured flow
numerical uncertainties, preliminary results show              solver grids. J. Comput. Phys., 227:2674–2706, 2008.
promise in regard to a further understanding of the
physical process of atomization with evaporation               [2] P. Zeng, B. Binninger, N. Peters and M. Herrmann.
effect. The mathematical model and the DNS                     Simulation of primary breakup for diesel spray with
solution presented here will provide the frame for a           phase transition. 11th ICLASS International Conference
statistical simulation of the primary breakup, within          on Liquid Atomization and Spray Systems, Accepted,
                                                               2009.

* Corresponding author: p.zeng@itv.rwth-aachen.de
Towards Clean Diesel Engines, TCDE2009

</pre>