Effects of Flash Boiling in Nozzle Flow of GDI Injector on Air/Fuel Mixture

2018 ◽  
Author(s):  
Eiji Ishii ◽  
Kazuki Yoshimura ◽  
Seiichi Koshizuka ◽  
Akihiro Sekine ◽  
Shota Sugihara
Keyword(s):  
Axial Symmetry ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Gasoline Direct Injection ◽  
Fuel Spray ◽  
Nozzle Flow ◽  
Cavitation Model ◽  
Spray Penetration ◽  
Flash Boiling ◽  
Fuel Mixtures

The widths of fuel plumes around nozzle outlets expanded due to flash boiling during the nozzle flow. In some sprays, the length (penetration) of the air/fuel mixture increased due to the flash boiling. A cavitation model was incorporated in a simulation of the fuel spray integrating a simulation of the nozzle flow with a simulation of the air/fuel mixture. The simulation was applied to fuel sprays from a gasoline direct-injection injector; six nozzles were placed on an orifice cup in axial symmetry. Expansions of the plumes (in terms of width) around the nozzle outlets due to flash boiling and extension of spray penetration qualitatively agreed with the measured ones. Effects of the expansions of the plumes due to flash boiling on spray-penetration distance were also studied. The result of that study indicated that interactions between the expanded plumes around the nozzle outlets cause the spray shape of the air/fuel mixtures to thin, thereby extending the penetration of the spray.

Advanced Numerical Approach to Simulate GDI Sprays Under Engine-Like Conditions

2014 ◽  
Author(s):  
Eiji Ishii ◽  
Motoyuki Abe ◽  
Hideharu Ehara ◽  
Yoshihito Yasukawa
Keyword(s):  
Flow Direction ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Numerical Approach ◽  
Gasoline Direct Injection ◽  
Fuel Spray ◽  
Density Region ◽  
Penetration Length ◽  
Spray Penetration ◽  
Fuel Injectors

Gasoline direct-injection (GDI) engines provide both higher engine power and better fuel efficiency than port-injection gasoline engines. However, they emit more particulate matter (PM) than the latter engines. Fuel stuck on walls of pistons and combustion chambers forms a high-density region of fuel in the air/fuel mixture, which becomes a source of PM. To decrease the amount of PM, fuel injectors with short length of spray-penetration are required. A fuel-spray simulation was previously developed; that is, the air/fuel-mixture simulation was integrated with the liquid-column-breakup simulation. The developed fuel-spray simulation was used to optimize the nozzle shapes of fuel injectors for gasoline direct-injection engines. In the present study, the factors that influence spray-penetration length were identified by the numerical simulation. The simulation results were validated by comparing the simulated spray-penetration length with the measured ones and revealing good agreement between them. Angle α was defined as that formed between the direction of flow entering the nozzle inlet and the direction of flow leaving the nozzle outlet; in other words, a indicates a change of flow direction. It was found that α and spray-penetration length was closely related. Velocity that are accelerated with a were studied, and it was found that the velocity within a plane perpendicular to the center axis of the nozzle increases with increasing α.

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

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Eiji Ishii ◽  
Yoshihito Yasukawa ◽  
Kazuki Yoshimura ◽  
Kiyotaka Ogura
Keyword(s):  
Surface Tension ◽  
Particulate Matter ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Fuel Spray ◽  
Direct Injection Engines ◽  
Fuel Injectors ◽  
Multiple Injections ◽  
Fuel Mixtures ◽  
Opening And Closing

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.

Short Spray-Penetration for Direct Injection Gasoline-Engines With Numerical Simulation

2013 ◽  
Author(s):  
Eiji Ishii ◽  
Motoyuki Abe ◽  
Hideharu Ehara ◽  
Tohru Ishikawa
Keyword(s):  
High Speed ◽  
Direct Injection ◽  
Grid Method ◽  
Particle Method ◽  
Fuel Mixture ◽  
Liquid Column ◽  
Fuel Spray ◽  
Spray Penetration ◽  
Fuel Injectors ◽  
Gasoline Engines

Direct injection gasoline-engines have both better engine power and fuel efficiency than port injection gasoline-engines. However, direct injection gasoline-engines also emit more particulate matter (PM) than port injection gasoline-engines do. To decrease PM, fuel injectors with short spray-penetration are required. More effective fuel injectors can be preliminarily designed by numerically simulating fuel spray. We previously developed a fuel-spray simulation. Both the fuel flow within the flow paths of an injector and the liquid column at the injector outlet were simulated by using a grid method. The liquid-column breakup was simulated by using a particle method. The motion of droplets within the air/fuel mixture (secondary-drop-breakup) region was calculated by using a discrete droplet model (DDM). In this study, we applied our fuel-spray simulation to sprays for the direct injection gasoline-engines. Simulated spray penetrations agreed relatively well with measured spray penetrations. Velocity distributions at the outlet of three kinds of nozzles were plotted by using a histogram, and the relationship between the velocity distributions and spray penetrations was studied. We found that shrinking the high-speed region and making the velocity-distribution uniform were required for short spray penetration.

Simulation of Coarse Droplet and Liquid Column Formed Around Nozzle Outlets due to Valve Wobble of a GDI Injector

2017 ◽  
Author(s):  
Eiji Ishii ◽  
Yoshihito Yasukawa ◽  
Kazuki Yoshimura ◽  
Kiyotaka Ogura
Keyword(s):  
Surface Tension ◽  
Particulate Matter ◽  
Body Surface ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Fuel Spray ◽  
Direct Injection Engines ◽  
Fuel Injectors ◽  
Fuel Mixtures ◽  
Opening And Closing

The generation of particulate matter (PM) is one problem with gasoline direct-injection engines. PM is generated in high-density regions of fuel that are formed by non-uniform air/fuel mixtures, coarse droplets generated during end-of-injection, and fuel adhering to the nozzle body surface and piston surface. Uniform air/fuel mixtures and short fuel-spray durations with multiple injections are effective in enabling the valves of fuel injectors to not 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 degrees. 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 degrees.

scholarly journals String flash-boiling in gasoline direct injection simulations with transient needle motion

2016 ◽  
Vol 87 ◽  
pp. 90-101 ◽  
Author(s):  
E.T. Baldwin ◽  
R.O. Grover ◽  
S.E. Parrish ◽  
D.J. Duke ◽  
K.E. Matusik ◽  
...  
Keyword(s):  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Flash Boiling

The Sensitivity of Inner Nozzle Flow in Gasoline Direct Injection Injector to the Nozzle Geometry Parameters

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Xinhai Li ◽  
Yong Cheng ◽  
Xiaoyan Ma ◽  
Xue Yang
Keyword(s):  
Structural Parameters ◽  
Direct Injection ◽  
Large Diameter ◽  
Small Diameter ◽  
Flow Characteristics ◽  
Gasoline Direct Injection ◽  
Nozzle Geometry ◽  
Nozzle Flow ◽  
Nozzle Length ◽  
Injector Nozzle

The inner-flow of gasoline direct injection (GDI) injector nozzles plays an important role in the process of spray, and affects the mixture process in gasoline engine cylinder. The nozzle structure also affects the inner-flow of GDI injector. In order to obtain uniform performance of GDI injector, the size consistency of injector nozzle should be ensured. This paper researches the effect of nozzle length and diameter on the inner flow and analyzes the sensitivity of inner flow characteristics to these structural parameters. First, this paper reveals the process of inception, development, and saturated condition of cavitation phenomenon in injector nozzle. Second, the inner-nozzle flow characteristics are more sensitive to small diameter than large diameter under the short nozzle length, while the sensitivity of the inner-nozzle flow characteristics to large nozzle diameter becomes strong as the increase of the nozzle length. Finally, the influence of nozzle angle on the injection mass flow is studied, and the single nozzle fuel mass will increase as the decrease of nozzle angle α. And the sensitivity of inner-flow characteristic to nozzle angle becomes strong as the decrease of α.

scholarly journals Numerical simulation of internal and near-nozzle flow of a gasoline direct injection fuel injector

2015 ◽  
Vol 656 ◽  
pp. 012100 ◽  
Author(s):  
Kaushik Saha ◽  
Sibendu Som ◽  
Michele Battistoni ◽  
Yanheng Li ◽  
Shaoping Quan ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Nozzle Flow ◽  
Fuel Injector

Modeling of Internal and Near-Nozzle Flow for a Gasoline Direct Injection Fuel Injector

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Kaushik Saha ◽  
Sibendu Som ◽  
Michele Battistoni ◽  
Yanheng Li ◽  
Shaoping Quan ◽  
...  
Keyword(s):  
Liquid Fuel ◽  
Numerical Study ◽  
Direct Injection ◽  
Computational Cost ◽  
Volume Averaging ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Superheated Liquid ◽  
Fuel Injector ◽  
Flash Boiling

A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a multihole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eight-hole counterbore injector, from the engine combustion network (ECN). Simulations have been carried out for a fixed needle lift. The effects of turbulence, compressibility, and noncondensable gases have been considered in this work. Standard k–ε turbulence model has been used to model the turbulence. Homogeneous relaxation model (HRM) coupled with volume of fluid (VOF) approach has been utilized to capture the phase-change phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine nonflashing and evaporative, nonflashing and nonevaporative, and flashing conditions. Noticeable hole-to-hole variations have been observed in terms of mass flow rates for all the holes under all the operating conditions considered in this study. Inside the nozzle holes mild cavitationlike and in the near-nozzle region flash-boiling phenomena have been predicted when liquid fuel is subjected to superheated ambiance. Under favorable conditions, considerable flashing has been observed in the near-nozzle regions. An enormous volume is occupied by the gasoline vapor, formed by the flash boiling of superheated liquid fuel. Large outlet domain connecting the exits of the holes and the pressure outlet boundary appeared to be necessary leading to substantial computational cost. Volume-averaging instead of mass-averaging is observed to be more effective, especially for finer mesh resolutions.

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