6Th Annual Conference on Liquid Atomization And

ILASS–Asia 2017 Oct. 18-21, 2017, Jeju, Korea

1. Introduction (Arial, 11 pt) 3. Results and Discussion

The extended abstract must be written in In order to validate the EMC model, calculation English, and it should be 2 to 4 pages long. The results are compared to experimental results of

TITLE (Arial, 18 pt)

AUTHOR1, AUTHOR2, AUTHOR3*

1 Affiliation (Times New Roman, 12 pt) 2 Affiliation (Times New Roman, 12 pt) 3 Affiliation (Times New Roman, 12 pt) Corresponding author: ○○○○○○○, Email: *****@*****.**.**

Keywords: DME (Dimethyl ether), EMC (Enhanced Momentum Coupling) model, Grid dependency, KIVA-3V code, Lagrangian-Eulerian method, Spray tip penetration extended abstract includes Introduction, Research spray penetration, and also compared with standard method and procedure, Results and discussion, and model’s results to investigate the improvement of Conclusions, as well as References. grid independency performance when using the EMC model. In this study, four different grid (Times New Roman, 11 pt) resolutions for three dimensional computational domains are used to test the grid-size sensitivity as shown in Fig. 4 2. Research Method and Procedure In this study, to test the grid-size dependency in the condition of highly evaporating spray 2.1 Subtitle characteristics, the DME spray system is simulated according to the different grid size conditions. Calculation conditions of this study are listed in Table 2. These conditions are selected from the DME spray experiment conducted by Konno et al. [7].

Table. 1. Model application for DME spray simulation

Standard model Improved model Momentum Standard model EMC model Fig. 1. Grid dependency of momentum transfer in Coupling standard KIVA code O’Rourke Collision Nordin model The evaporation model that is popularly used in model the spray CFD code is based on the Spalding’s Vaporization Sparding type model theory [5]. Governing equation of Spalding theory is derived according to the Fick's where means vapor mass fraction in the control 3.1 Spray tip penetration volume. Fig. 5 shows simulation results of spray structure and contour of ambient gas velocity at t = ILASS–Asia 2017 Oct. 18-21, 2017, Jeju, Korea 0.4 ms after start of injection. As seen in Fig. 5 (a), spray shapes and penetration results by the standard model appear to be heavily influenced by the grid size, and particles penetrate further into gaseous phase downward with decrease of the grid size. Abani et al [1] pointed out that the main reason of the grid dependency problem arises from the Acknowledgments prediction of inaccurate ambient gas drag force. For example, as cell size becomes smaller, the Acknowledgement accelerated gas velocity becomes faster and thus aerodynamic drag force decreases, resulting in longer spray tip penetration. Therefore, in the standard model, the prediction of spray tip penetrating length is a function of grid cell size. 5. Reference On the other hand, as shown in Fig. 5 (b), grid dependency problem appears to be almost resolved 1. Abani, N., Kokojohn, S., Park, S. W., Bergin, by using the improved model. When performing M., Munnannur, A., Ning, W., Sun, Y., and spray calculation at each time step, this EMC Reitz, D., "An improved Spray Model for model identically set a fixed droplet volume Reducing Numerical Parameter Dependencies fraction, thus it makes predicted penetration results in Diesel Engine CFD Simulation", SAE Paper less grid-size independent regardless of 2008-01-0970, 2008 computational grid size. 2. Kim, S., Park, S. W., Lee, C. S., "Improved 4. Conclusion Euler-Lagrange spray simulation by using an enhanced momentum coupling model", This paper focused on the investigation of the ICEF2009-14079, proc. ASME Internal causes of grid dependency in the standard spray Combustion Engine Division 2009 Fall models and the strategy for reducing the grid Conference, Lucerne, Switzerland, 2009. dependency by applying the improved models. To simulate the spray penetrating into the gas phase, 3. Spalding, D. B., “The Combustion of liquid Eulerian-Lagrangian method was used in the KIVA Fuels”, Fourth Symposium (International) on code. To verify the reason of grid-size dependency Combustion, The Combustion Institute, and improve the prediction accuracy, two different Pittsburgh, Penn., 1953. spray models were compared each other. The important conclusions are summarized as follows: 4. Amsden, A. A., “KIVA-3V: a block structured KIVA program for engines with vertical or 1. In the standard KIVA model, simulation results canted values”, Technical report, No. LA- inherently have grid dependency problem. One 13313-MS, Los Alamos National Laboratory, of the reasons is caused by Eulerian-Lagrangian 1997. method’s own assumption. This method is ineffective to consider the physically reasonable 5. Nordin, N., 2000. “A mesh independent momentum transfer between two phases. As a collision condition for Lagrangian sprays”, result, the value of the relative velocity and Thermo and Fluid Dynamics, Chalmers drag force are sensitive to grid resolution. University of Technology. Another grid dependency reason is O’Rourke’s collision model that used in standard KIVA 6. Park, S. W., Suh, H. Kyu., Lee, C. S., Abani, model. Since this model supposes that collision N., Reitz, R. D., "Modeling of group-hole- only occurs in the same cell, collision nozzle spray using grid-size, hole-location, and probability depends on the grid size. time step independent model ", Atomization and sprays, pp. 567-582, 2009