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Research Papers: Internal Combustion Engines

Late-Fuel Simulation Near Nozzle Outlet of Fuel Injector During Closing Valve

[+] Author and Article Information
Eiji Ishii

Research and Development Group,
Hitachi, Ltd.,
832-2 Horiguchi, Hitachinaka,
Ibaraki 312-0034, Japan
e-mail: eiji.ishii.qm@hitachi.com

Kazuki Yoshimura

Research and Development Group,
Hitachi, Ltd.,
832-2 Horiguchi,
Hitachinaka, Ibaraki 312-0034, Japan
e-mail: kazuki.yoshimura.ox@hitachi.com

Yoshihito Yasukawa

Research and Development Group,
Hitachi, Ltd.,
832-2 Horiguchi, Hitachinaka,
Ibaraki 312-0034, Japan
e-mail: yoshihito.yasukawa.uw@hitachi.com

Hideharu Ehara

Hitachi Automotive Systems, Ltd.,
2520 Takaba, Hitachinaka,
Ibaraki 312-8503, Japan
e-mail: hideharu.ehara.kz@hitachi-automotive.co.jp

Contributed by the IC Engine Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received January 20, 2016; final manuscript received February 16, 2016; published online April 12, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(10), 102801 (Apr 12, 2016) (9 pages) Paper No: GTP-16-1026; doi: 10.1115/1.4032885 History: Received January 20, 2016; Revised February 16, 2016

Late fuel during closing of the valve of a fuel injector and fuel films stuck on the wall around the nozzle outlets are sources of particulate matters (PM). In this study, we focused on the effects of the valve motions on the late fuel and the fuel films stuck on the walls around the nozzle outlets. We previously developed a particle/grid hybrid method: fuel flows within the flow paths of fuel injectors were simulated by a front capturing method, and liquid-column breakup at the nozzle outlets was mainly simulated by a particle method. The velocity at the inlet boundary of a fuel injector was controlled in order to affect the valve motions on the late-fuel behavior. The simulated late fuel broke up with surface tension around the time of zero-stroke position of the valve, then liquid columns and coarse droplets formed after the bounds of the valve, and finally only coarse droplets were left. We found that the late fuel was generated by low-speed fuel-flows through the nozzles during the bounds of the valve. The effect of the bounds of the valve on the fuel films stuck on the wall around the nozzle outlets was also studied with a simulation that removed the bounds of the valve. The volume of the fuel films stuck on the wall of the nozzle outlets decreased without the bounds of the valve.

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References

Hirt, C. W. , and Nichols, B. D. , 1981, “ Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries,” J. Comput. Phys., 39(1), pp. 201–225. [CrossRef]
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Tanguy, S. , Menard, T. , Berlemont, A. , Estivalezes, J. L. , and Courderc, F. , 2004, “ Developpement D'une Methode Level Set Pour Le Suivi D'interfaces et Applications,” Advances in the Modeling Methodologies of Two-Phase Flows, Lyons, France, Nov. 24–26, Paper No. 13.
Tanguy, S. , and Berlemond, A. , 2005, “ Application of a Level Set Method for Simulation of Droplet Collisions,” Int. J. Multiphase Flow, 31(9), pp. 1015–1035. [CrossRef]
Pan, Y. , and Suga, K. , 2004, “ Direct Simulation of Water Jet Into Air,” 5th International Conference on Multiphase Flow (ICMF’04), Yokohama, Japan, May 30–June 4, Paper No. 377.
Battistoni, M. , Xue, Q. , and Som, S. , 2014, “ Effect of Off-Axis Needle Motion on Internal Nozzle and Near Exit Flow in a Multi-Hole Diesel Injector,” SAE Int. J. Fuels Lubr., 7(1), pp. 167–182. [CrossRef]
Ishii, E. , Ishikawa, T. , and Tanabe, Y. , 2006, “ Hybrid Particle/Grid Method for Predicting Motion of Micro- and Macrofree Surfaces,” ASME J. Fluids Eng., 128(5), pp. 921–930. [CrossRef]
Ishii, E. , Ishikawa, M. , Sukegawa, Y. , and Yamada, H. , 2011, “ Secondary-Drop-Breakup Simulation Integrated With Fuel-Breakup Simulation Near Injector Outlet,” ASME J. Fluids Eng., 133(8), p. 081302. [CrossRef]
Koshizuka, S. , and Oka, Y. , 1996, “ Moving-Particle Semi-Implicit Method for Fragmentation of Incompressible Fluid,” Nucl. Sci. Eng., 123(3), pp. 421–434.
Ishii, E. , and Sugii, T. , 2012, “ Surface Tension Model for Particle Method Using Inter-Particle Force Derived From Potential Energy,” ASME Paper No. FEDSM2012-72030.
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Figures

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Fig. 1

Concept of particle/grid hybrid method. Inner flows in fuel injector and liquid column near nozzle outlets were simulated with a grid method (CIP), and liquid-column breakup was done with a particle method (MPS).

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Fig. 2

MPS and CIP procedures in hybrid method

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Fig. 3

Definition of distance from interface. θCIP is the volume fraction of liquid. The position of the free surface is defined as 0.5 of the volume fraction of liquid given by CIP. δ is the distance defined at the particle coordinates as the number of cells from a free surface.

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Fig. 4

Dependency of particle density on pressure in sphere droplet. Pressure was normalized by pressure given with the theory of Young–Laplace equation.

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Fig. 5

Verification of the surface tension model in particle method (MPS) with theoretical solution. (a) Simulation results in cases of different contact angles. (b) Wettings of a droplet on a wall over nondimensional time t* in the case of contact angle of 60 deg.

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Fig. 6

Simulation model of the late-fuel behavior during closing of valve: (a) simulation model around valve seat and (b) time changes of valve lift with valve bounds

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Fig. 7

Experimental equipment for measuring valve lift

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Fig. 8

Computational grids used in VOF simulation with closing of valve; time changes of flow rate injected from a fuel injector were predicted. Polyhedral grids (left figure) were applied. Extended section-view around valve seat is shown in the right figure.

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Fig. 9

Nondimensional flow rate and nondimensional valve lift during closing of valve. Time of 0.0 ms was defined as when valve started closing.

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Fig. 10

Late-fuel behaviors injected from nozzles during closing of valve. Time of 0.0 ms was defined as when valve started closing. Color bar shows volume fraction of liquid: fuel: 1 and air: 0.

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Fig. 11

Computational grids in late-fuel simulation with particle/grid hybrid method (left figure). Hexahedron grids of 393,116 cells were applied. Extended picture of orifice cup from bottom is shown in the right figure.

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Fig. 12

Grid-dependency study of flow rate

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Fig. 13

Simulated late-fuel behaviors with particle/grid hybrid method (left figures). Simulated results were compared with measured ones (right figures). Time of 0.0 ms was defined as when valve started closing.

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Fig. 14

Comparison of the late-fuel behaviors at the time of a valve lift of 0.0 μm (0.5 ms after the valve started closing): (a) simulated late-fuel with the VOF simulation, (b) with the particle/grid hybrid method, and (c) measured rate fuel

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Fig. 15

Relationships between late-fuel behaviors and valve motion. Late-fuel behaviors were classified into types A, B, C, and D. Type A: fuel broken up with shear stress by air; type B: fuel broken up with surface tension; type C: generation of liquid columns and coarse droplets; and type D: generation of coarse droplets only.

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Fig. 16

Relationships between late-fuel behaviors (left figures) and velocity distributions (right figures) after valve bounds

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Fig. 17

Effects of the valve bounds on late-fuel behaviors. Simulated late-fuel (a) with and (b) without valve bounds.

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Fig. 18

Fuel stuck around nozzle outlets. Simulation results (a) with valve bounds (4.0 ms) and (b) without valve bounds (1.8 ms).

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Fig. 19

Effects of valve bounds on volume of late fuel. Volumes of late fuels were substituted for number of particles in late fuels.

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