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Research Papers: Internal Combustion Engines

Simulation of Coarse Droplet and Liquid Column Formed around Nozzle Outlets Due to Valve Wobble of a Gasoline Direct Injection Injector

[+] Author and Article Information
Eiji Ishii

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

Yoshihito Yasukawa

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

Kazuki Yoshimura

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

Kiyotaka Ogura

Hitachi Automotive Systems, Ltd.,
2520 Takaba,
Hitachinaka 312-8503, Ibaraki, Japan
e-mail: kiyotaka.ogura.nb@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 February 19, 2018; final manuscript received March 4, 2018; published online June 18, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(10), 102801 (Jun 18, 2018) (8 pages) Paper No: GTP-18-1076; doi: 10.1115/1.4039808 History: Received February 19, 2018; Revised March 04, 2018

The generation of particulate matter (PM) is one problem with gasoline direct-injection engines. PM is generated in high-density regions of fuel. Uniform air/fuel mixtures and short fuel-spray durations with multiple injections are effective in enabling the valves of fuel injectors not to wobble and dribble. We previously studied what effects the opening and closing of valves had on fuel spray behavior and found that valve motions in the opening and closing directions affected spray behavior and generated coarse droplets during the end-of-injection. We focused on the effects of valve wobbling on fuel spray behavior in this study, especially on the behavior during the end-of-injection. The effects of wobbling on fuel spray with full valve strokes were first studied, and we found that simulated spray behaviors agreed well with the measured ones. We also studied the effects on fuel dribble during end-of-injection. When a valve wobbled from left to right, the fuel dribble decreased in comparison with a case without wobbling. When a valve wobbled from the front to the rear, however, fuel dribble increased. Surface tension significantly affected fuel dribble, especially in forming low-speed liquid columns and coarse droplets. Fuel dribble was simulated while changing the wetting angle on walls from 60 to 5 deg. We found that the appearance of coarse droplets in sprays decreased during the end-of-injection by changing the wetting angles from 60 to 5 deg.

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References

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Figures

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Fig. 1

Simulation model of fuel spray with valve wobble during injector dribble: (a) inner flow simulation with valve wobble; valve motion perpendicular to valve closing direction was simulated using mesh morphing and flow rate at inlet boundary during closing of valve was given by using another simulation using remeshing [10] (the region is marked by dashed line in (b)), and (b) fuel breakup simulation using hybrid method

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Fig. 2

Experimental setup for measuring fuel-spray behaviors

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Fig. 3

Experimental setup for measuring fuel spray during injector dribble with long-distance microscope

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Fig. 4

Experimental setup for measuring valve lift

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Fig. 5

Fuel-spray behaviors over time. Wobbles of center spray plumes; left pictures: thick spray plumes and right pictures: thin spray plumes. (Times of thick and thin spray plumes through right and left nozzles are a little shifted from those through the center nozzle).

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Fig. 6

Measured times when ith wobbles of every half cycle of oscillation occur

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Fig. 7

Interval times when ith wobbles of every half cycle of oscillation occur

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Fig. 8

Computational grids. The figure on the right is an extended view from the air region; six nozzles are assigned on the orifice cup.

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Fig. 9

Amplitude of valve wobbles over time in simulation

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Fig. 10

Simulated fuel sprays with valve oscillation in the (a) y (rear-to-front) direction and (b) x (left-to-right) direction

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Fig. 11

Comparison of simulated fuel dribbles with measured ones: (a) measured valve lift and simulated flow rate over time [11], (b) measured fuel dribble, and (c) simulated ones without valve wobble and with valve wobble in the x and y directions

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Fig. 12

Effects of valve wobbles on volume of fuel dribble. Volumes of fuel dribble were substituted for number of particles in fuel dribble.

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Fig. 13

Effects of valve wobbles on velocity distributions in orifice cup; without valve wobble (a) at time of full stroke and (b) at 0.45 ms, and with valve wobbles at 0.45 ms in the (c) x direction and (d) y direction

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Fig. 14

Effects of wetting angle on fuel dribble (results with wetting angle of 60 deg is same as those in Fig. 11)

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Fig. 15

Effects of wetting angle on fuel dribble at 1.5 ms; wetting angle of (a) 60 deg (original) and (b) 5 deg

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Fig. 16

Effects of wetting angles on volume of fuel dribble. Volumes of fuel dribble were substituted for number of particles in fuel dribble.

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