Secondary-Drop-Breakup Simulation Integrated With Fuel-Breakup Simulation Near Injector Outlet

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Eiji Ishii ◽  
Masanori Ishikawa ◽  
Yoshihiro Sukegawa ◽  
Hiroshi Yamada
Keyword(s):  
Liquid Film ◽  
Particle Method ◽  
Liquid Films ◽  
Fuel Spray ◽  
Fuel Injector ◽  
Drop Breakup ◽  
Free Surfaces ◽  
Collision Type ◽  
Automobile Engines ◽  
Secondary Drop

The fuel spray of an injector for automobile engines contains multiscale free surfaces: liquid films formed at the fuel-injector outlet, ligaments generated by liquid-film breakup, and droplets generated from the ligaments within the secondary-drop-breakup region. To simulate these multiscale free surfaces, we developed a method that combines two types of simulation. The liquid-film breakup near the injector outlet was simulated by using a particle method, and the secondary-drop breakup after the liquid-film breakup was simulated by using a discrete droplet model (DDM). The injection conditions of DDM were the distributions of droplet diameters and velocities calculated in the liquid-film-breakup simulation. We applied our method to simulate the spray from a collision-type fuel injector. The simulated liquid-film breakup near the injector outlet and behavior of the secondary-drop breakup qualitatively agreed with measurements. Furthermore, the errors of the mean droplet diameters between the simulations and the measurements were less than 12%. This shows that our method is effective for fuel spray simulation.

Fuel Spray Simulation With Collision Jets for Automobile Engines

2010 ◽  
Author(s):  
Eiji Ishii ◽  
Yoshihiro Sukegawa ◽  
Hiroshi Yamada
Keyword(s):  
Liquid Film ◽  
Leading Edge ◽  
Particle Method ◽  
Fuel Mixture ◽  
Liquid Films ◽  
Fuel Spray ◽  
Diameter Distribution ◽  
Fuel Injector ◽  
Automobile Engines ◽  
Spray Distribution

Fuel injectors for automobile engines atomize fuel into multi-scale free surfaces: liquid films formed at the fuel-injector outlet, ligaments generated by the liquid-film breakup, and droplets generated from the ligaments within the air/fuel mixture region. We previously developed a fuel spray simulation combining the liquid-film breakup near the injector outlet with the air/fuel mixture. The liquid-film breakup was simulated by a particle method. The fuel-droplet behavior in the air/fuel mixture region was simulated by a discrete droplet model (DDM). In this study, we applied our method to simulate fuel sprays from a fuel injector with collision jets. The simulation results were compared with the measurements—the mean diameter of droplet in spray, D32, was 35 percent larger than measured D32. We also studied the effects of DDM injection conditions on the spray distribution in the air/fuel mixture region—diameter distributions of injected DDM-droplets were given by the liquid-film breakup simulation, or by Nukiyama-Tanazawa’s theory. The diameter distribution of droplets near the injector outlet was found to affect the spray distribution within the air/fuel mixture region, mainly around the leading edge of spray.

A Fuel-Spray Simulation Considering Fuel-Jet Breakup Near Fuel Injector and Composition of Air/Fuel Mixture

2009 ◽  
Author(s):  
Eiji Ishii ◽  
Yoshihito Yasukawa ◽  
Yoshihiro Sukegawa ◽  
Hiroshi Yamada
Keyword(s):  
Liquid Film ◽  
Particle Method ◽  
Fuel Mixture ◽  
New Method ◽  
Fuel Spray ◽  
Fuel Injector ◽  
Scale Free ◽  
Jet Breakup ◽  
Fuel Jet ◽  
Automobile Engines

To simulate multi-scale free surfaces in the fuel spray of an injector for automobile engine, we combined a liquid-film-breakup simulation and an air/fuel-mixture simulation. The liquid-film breakup near the injector outlet was simulated by using a particle method, and the air/fuel mixture after the liquid-film breakup was simulated by using a “discrete droplet model” (DDM). Distributions of droplet diameters and velocities, calculated in the liquid-film breakup simulation, were used as the injection condition of DDM. We applied our new method to simulate the spray from a collision fuel injector. The simulation results were verified by comparing them with measurements. The liquid-film breakup near the injector outlet and the behavior of the air/fuel mixture qualitatively agreed with the measurements. We found that out new method was useful to the fuel-spray simulation for automobile engines.

Particle/CIP Hybrid Method for Predicting Motions of Micro and Macro Free Surfaces

Volume 3 ◽  
2004 ◽  
Author(s):  
Eiji Ishii ◽  
Toru Ishikawa ◽  
Yoshiyuki Tanabe
Keyword(s):  
Liquid Film ◽  
Hybrid Method ◽  
Volume Fraction ◽  
Particle Method ◽  
Liquid Films ◽  
Liquid Column ◽  
Cip Method ◽  
Fuel Injector ◽  
Free Surfaces ◽  
Liquid Flows

To predict motions of micro and macro free surfaces simultaneously within gas-liquid flows, we have developed a particle/CIP (Cubic Interpolated Propagation) hybrid method. The micro free surfaces (smaller than grid sizes) were simulated by the particle method, and the macro free surfaces (larger than grid sizes) were simulated by the CIP method. And then the particles used in the particle method were assigned near the macro free surfaces by using volume fraction of liquid that was calculated by the CIP method. The developed method was used to predict the collapse of a liquid column. Namely, it predicted both the large deformation of the liquid column and the fragmentation of it simultaneously, and the predicted configurations of the liquid column agreed well with the experimentally measured ones. It was also used to predict breakup of liquid films in a fuel injector used for engines of automobiles, and the predicted profile of the liquid film was sharp in an air region where the thickness of the liquid film became thinner than the grid sizes.

Simulation of Liquid Jet Breakup of a Swirl-Type Fuel Injector for Automobile Engines

2007 ◽  
Author(s):  
Eiji Ishii ◽  
Toru Ishikawa ◽  
Yoshiyuki Tanabe
Keyword(s):  
Water Column ◽  
Grid Method ◽  
Particle Method ◽  
Engine Fuel ◽  
Fuel Injector ◽  
Free Surfaces ◽  
Scale Free ◽  
Multi Scale ◽  
Jet Breakup ◽  
Automobile Engines

To simulate multi-scale free surfaces, we developed a hybrid particle/grid method by which the free surfaces within sub-grid regions are simulated by the particle method, and other regions are simulated with the grid method. The particle method uses two types of particles to model gas and liquid fluids in order to simulate the interaction between them. We tested the new method on fragmentation of a water column, and the predicted configurations of the water column are consistent with measurements of Koshizuka and Oka. We also simulated the fuel spray near the outlet of an automobile-engine fuel injector and found that this method qualitatively simulated the breakup of the liquid film.

Hybrid Particle/Grid Method for Predicting Motion of Micro- and Macrofree Surfaces

2006 ◽  
Vol 128 (5) ◽  
pp. 921-930 ◽  
Author(s):  
Eiji Ishii ◽  
Toru Ishikawa ◽  
Yoshiyuki Tanabe
Keyword(s):  
Liquid Film ◽  
Volume Fraction ◽  
Grid Method ◽  
Particle Method ◽  
Liquid Films ◽  
Liquid Column ◽  
Computational Time ◽  
Fuel Injector ◽  
Hybrid Particle ◽  
Liquid Flows

We developed a method of hybrid particle/cubic interpolated propagation (CIP) to predict the motion of micro- and macrofree surfaces within gas-liquid flows. Microfree surfaces (smaller than the grid sizes) were simulated with the particle method, and macrofree surfaces (larger than the grid sizes) were simulated with the grid method (CIP is a kind of grid method). With the hybrid, velocities given by the advection part of the particle method were combined with those given by the advection part of CIP. Furthermore, the particles used with the particle method were assigned near the macrofree surfaces by using the volume fraction of liquid that was calculated with CIP. The method we developed was used to predict the collapse of a liquid column. Namely, it was simultaneously able to predict both large deformation in the liquid column and its fragmentation, and the predicted configurations for the liquid column agreed well with the experimentally measured ones. It was also used to predict the behavior of liquid films at the outlet of a fuel injector used for automobile engines. The particle method in the simulation was mainly used for liquid films in the air region and the grid method was used for the other regions to shorten the computational time. The predicted profile of the liquid film was very sharp in the air region where the liquid film became thinner than the grid sizes; there was no loss of liquid film with numerical diffusion.

Applying Particle/Grid Hybrid Method to Fuel Spray With Collision Jet for Automobile Engines

2010 ◽  
Author(s):  
Eiji Ishii ◽  
Masanori Ishikawa ◽  
Yoshihiro Sukegawa ◽  
Hiroshi Yamada
Keyword(s):  
Liquid Film ◽  
Water Column ◽  
Hybrid Method ◽  
Fuel Mixture ◽  
Fuel Spray ◽  
Fuel Injector ◽  
Free Surfaces ◽  
Scale Free ◽  
Multi Scale ◽  
Modified Method

A fuel spray contains multi-scale free surfaces: liquid films formed at the fuel-injector outlet, ligaments generated by the liquid-film breakup, and droplets generated from the ligaments within the air/fuel mixture region. To simulate multi-scale free surfaces, we previously developed a fuel spray simulation combining the liquid-film breakup with the air/fuel mixture. In this study, we modified a part of the liquid-film breakup simulation that uses a particle/grid hybrid method. The procedures combining a particle method and a grid method were changed to obtain more accurate prediction. First, a simple benchmark test, collapse of a water column as investigated by Martine and Moyce, was used to verify the modified simulation method; the behavior of the water column better agreed with measurements than that by the original method. Next, we applied the modified method to simulate the collision jets from three kinds of nozzles. The simulation results were verified by comparison with measurements; the predicted liquid-film breakup qualitatively agreed well with measurements. Furthermore, the errors of mean droplet-diameters between the simulations and the measurements were less than 12%. Therefore, we found that the modified method was effective for spray simulation.

Predicting Droplet Size and Spray Angle of a Fuel Spray From an Automobile Fuel Injector With Multi-Swirl Nozzles

2013 ◽  
Author(s):  
Kazuki Yoshimura ◽  
Eiji Ishii ◽  
Yoshio Okamoto ◽  
Nobuaki Kobayashi
Keyword(s):  
Liquid Film ◽  
Droplet Size ◽  
Gasoline Engine ◽  
Thin Liquid Film ◽  
Liquid Films ◽  
Swirl Flow ◽  
Vof Method ◽  
Spray Angle ◽  
Fuel Spray ◽  
Fuel Injector

A fuel injector with multi-swirl nozzles for finely atomizing a fuel spray in a gasoline engine was developed. The multi-swirl nozzles are composed of swirl chambers placed in the upstream of each orifice which is an outlet of injector. The swirl flow produced by the swirl chambers forms thin liquid films on the walls of the orifices by centrifugal force, and these films break up into small droplets outside the orifices. In this study, fuel flow within the swirl nozzle was simulated by using the volume of fluid (VOF) method, and the simulated velocities and width of the thin liquid film were used to predict the droplet size and spray angle of the fuel spray. Miyamoto’s atomization model was applied to connect a circumferential velocity and a width of the liquid film at the orifice outlet with the droplet size. It was found that the droplet size and spray angle of multi-swirl nozzles can be predicted by using the VOF method and Miyamoto’s atomization model.

Simulation of Liquid Jet Breakup Using a Combination of Particle and Grid Methods

2005 ◽  
Author(s):  
Eiji Ishii ◽  
Toru Ishikawa ◽  
Yoshiyuki Tanabe
Keyword(s):  
Liquid Film ◽  
Computation Time ◽  
Grid Method ◽  
Particle Method ◽  
Liquid Films ◽  
Liquid Jet ◽  
Computational Domain ◽  
Fuel Injector ◽  
Automobile Engine ◽  
Numerical Diffusion

Fine atomization of the liquid jet from a fuel injector in an automobile engine lowers engine emissions and improves fuel efficiency. The breakup length of liquid films and the lengths of ligaments near the injector outlet after the breakup of liquid films are important parameters for predicting the atomization. These parameters have been predicted mainly using the Eulerian-grid method. (We refer to this as the ‘grid method’.) However, the grid method causes a loss of the liquid film with numerical diffusion, and it requires a large amount of computation time in practical engineering aspect because fine meshes smaller than the ligaments must be used. On the other hand, the particle method, an alternative (particle-based) method for representing the continuum Navier-Stokes equation which can simulate a ligament using a group of particles, does not cause numerical diffusion. However, a large number of particles are needed to simulate the entire computational domain within the injectors. In this study, we have focused on the flow field only near the injector outlet, and have tried to simulate the breakup of liquid films by using groups of particles in the particle method. In the simulation, the particle method was applied only to the liquid film and the grid method was used in other regions to shorten the computation time. Furthermore, we tried to integrate Brackbill’s surface-tension model, which is widely used in the grid method, into the particle method. To evaluate this approach, we compared the breakup lengths obtained for a cylindrical liquid jet in a uniform air stream with measurements done by Arai and Hashimoto; the breakup lengths agreed well with their measurements. We then simulated the breakup of a liquid film near the outlet of a fuel injector used for automobile engine, and found that our hybrid method could simulate the breakup of the liquid film into ligaments.

Fine Atomization and Low Penetration Fuel Spray by Using a Multi-Swirl Nozzle for Automobile Engines

2007 ◽  
Author(s):  
Yoshihito Yasukawa ◽  
Yoshio Okamoto
Keyword(s):  
Liquid Film ◽  
Formation Control ◽  
Gasoline Engine ◽  
Swirling Flow ◽  
Thin Liquid Film ◽  
Exhaust Emissions ◽  
Fuel Spray ◽  
Nozzle Outlet ◽  
Long Distance ◽  
Automobile Engines

Improving fuel economy and reducing exhaust emissions of automobile engines have become very important. The direct injection gasoline engine has the advantage of reduced fuel consumption, but it also has disadvantages related to exhaust emissions. Weak mixing of fuel with air due to short mixing time and fuel liquid-film adhering to the engine cylinder walls cause emission problems. To reduce these emissions, injectors need to provide fine atomization, low fuel penetration (length of fuel spray), and spray formation control. In this study, we developed a multi-swirl nozzle that forms a thin liquid-film at the nozzle outlet for fine atomization; the thin liquid-film easily breaks up into small droplets. We investigated the fuel spray characteristics of these nozzles experimentally and numerically. Using a long-distance microscope, we found that a liquid-film formed at the nozzle outlet even if its diameter was small. This is an effect of the centrifugal force from the swirl flow. Experimental results also showed that the multi-swirl nozzle reduced the size of coarse droplets (irregular, large droplets) and shortened fuel penetration. We also simulated numerically the fuel flow of the multi-swirl nozzle. Numerical analysis described the swirling flow that the multi-swirl nozzle generated above the nozzle inlet and the thin liquid-film at the nozzle outlet.

Fuel-Spray Simulation With Valve Motion Perpendicular to Closing Direction

2017 ◽  
Author(s):  
Eiji Ishii ◽  
Yoshihito Yasukawa ◽  
Kazuki Yoshimura ◽  
Kiyotaka Ogura
Keyword(s):  
Flow Simulation ◽  
Grid Method ◽  
Ccd Camera ◽  
Particle Method ◽  
Fuel Mixture ◽  
Fuel Spray ◽  
Fuel Injector ◽  
Multiple Injections ◽  
Fuel Sprays ◽  
Valve Motion

Particulate matter (PM) in exhaust gas from automotive engines causes air pollution. Multiple injections of fuel into the combustion chamber is one of the solutions to decrease PM; a uniform air/fuel mixture and short fuel-spray duration by using multiple injections are effective to decrease PM. To form the uniform air/fuel mixture, fuel sprays from fuel injectors needs to be uniform during injections. Unsteady valve-motions, especially those perpendicular to the closing direction, cause spray swings that form un-uniformity of air/fuel mixture. It is difficult to measure valve motions in the space of a few micrometer within a stainless steel body during fuel injections. Fuel-spray simulation is useful to study the effect of valve motion on the un-uniformity of fuel sprays. In fuel-spray simulation, jets passing through nozzles need to be simulated with the valve motion. We previously developed a particle/grid hybrid method that integrated the inner flow simulation using a grid method with a fuel breakup simulation using a particle method. In this study, we studied the effects of valve motions perpendicular to the closing direction on fuel sprays in order to decrease the un-uniformity of air/fuel mixture. First, we observed fuel-spray behaviors during measurements; a fuel injector with multi-holes was selected, and spray patterns were recorded by a CCD camera with a Xenon flash lamp. The jets passing through the nozzles changed their profiles over time, and the widths of the jets changed from thin to thick at almost the same time. The simulated spray behaviors with valve motion in the front-to-rear direction showed the same trends as those in measurement. It is assumed that because the positions of the six nozzles on the orifice cup were assigned asymmetrically in the front-to-rear direction, asymmetric flow distribution caused the valve motion.

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