First observation and characterization of vortex flow in steel micronozzles for high-pressure diesel injection

Moon, Seoksu; Huang, Weidi; Wang, Jin

doi:10.1016/j.expthermflusci.2019.04.018

Cited by 27 publications

(20 citation statements)

References 20 publications

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“…It has been reported that the spray angle widens due to turbulence caused by the sudden expansion from the narrow seat to the sack at the small needle valve opening inside the nozzle. (Moon et al, 2019). It is considered that the breakup of the droplet is promoted by this turbulence.…”

Section: Results and Discussion 31 Time Variations Of Velocity And Sizementioning

confidence: 99%

“…It is considered that conventional methods could not be applied to the region where the number density of droplets is high. The flow of fuel immediately after injection (Moon et al, 2015c), the velocity (Moon et al, 2015a) and mass (Kastengren et al, 2014) distributions of droplets in the vicinity of the nozzle hole, and the fuel flow inside the nozzle (Moon et al, 2019) (Moon et al, 2015b) were measured by applying X-rays. Since this technique is based on line-of-sight transmission measurements and the results include information on all droplets from the front to the back of the spray.…”

Section: Introductionmentioning

confidence: 99%

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Droplet size decrease rate of secondary breakup in diesel fuel sprays

Saito¹,

Komada

Sakaguchi

et al. 2021

JTST

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Targeting the evaluation of the universal droplet breakup process, measurements were made on diesel fuel sprays injected from two solenoid type injectors with different specifications. The velocity and size of the spray droplets were measured using a laser 2-focus velocimeter (L2F). The velocity of small droplets that follow the flow was taken as the air velocity. The Weber number was evaluated using the velocity of the droplets relative to air as the representative velocity. Since the spray expands in a conical shape with the nozzle hole at its apex, the measurement points were placed on a straight line from the apex, which is the estimated flight direction of droplets. The change in droplet size in the flight direction was considered to be due to secondary breakup, and the rate of decrease in droplet size during this process was evaluated. It was confirmed that the velocity and size of the droplets inside the spray injected from the two injectors varied over time, and the spatial distribution of the Weber number and the rate of droplet size decrease in the middle of the injection period was non-uniform and different. It was found that there is a positive correlation between the Weber number and the rate of droplet size decrease for both sprays, and that the relationship is nearly identical despite the fact that the characteristics are different between the two sprays. The secondary breakup process was shown to be independent of the injection conditions such as the diameter and number of nozzle holes.

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Section: Results and Discussion 31 Time Variations Of Velocity And Sizementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Droplet size decrease rate of secondary breakup in diesel fuel sprays

Saito¹,

Komada

Sakaguchi

et al. 2021

JTST

View full text Add to dashboard Cite

show abstract

“…Since this effect is related to the number of cavitation bubbles which further coalesce and form the cavitation structures (clouds), it is dependent on nozzle size and can differ in real size nozzles and large scale nozzles (models). The X-ray phase-contrast imaging technique and X-ray tracer imaging methods can be used to monitor real conditions during the injection process using petroleum-based fuels [20]. All the presented experimental methods are appropriate for monitoring flow conditions and cavitation inside the injector nozzle, but they are usually related to high costs of experimental equipment and long measurement procedures in the case of studying several fuels and operating regimes.…”

Section: Introductionmentioning

confidence: 99%

Effect of the In-Cylinder Back Pressure on the Injection Process and Fuel Flow Characteristics in a Common-Rail Diesel Injector Using GTL Fuel

et al. 2021

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The presented paper aims to study the influence of mineral diesel fuel and synthetic Gas-To-Liquid fuel (GTL) on the injection process, fuel flow conditions, and cavitation formation in a modern common-rail injector. First, the influence on injection characteristics was studied experimentally using an injection system test bench, and numerically using the one-dimensional computational program. Afterward, the influence of fuel properties on internal fuel flow was studied numerically using a computational program. The flow inside the injector was considered as multiphase flow and was calculated through unsteady Computational Fluid Dynamics simulations using a Eulerian–Eulerian two-fluid approach. Finally, the influence of in-cylinder back pressure on the internal nozzle flow was studied at three distinctive back pressures. The obtained numerical results for injection characteristics show good agreement with the experimental ones. The results of 3D simulations indicate that differences in fuel properties influence internal fuel flow and cavitation inception. The location of cavitation formation is the same for both fuels. The cavitation formation is triggered regardless of fuel properties. The size of the cavitation area is influenced by fuel properties and also from in-cylinder back pressure. Higher values of back pressure induce smaller areas of cavitation and vice versa. Comparing the conditions at injection hole exit, diesel fuel proved slightly higher average mass flow rate and velocities, which can be attributed to differences in fluid densities and viscosities. Overall, the obtained results indicate that when considering the injection process and internal nozzle flow, GTL fuel can be used in common-rail injection systems with solenoid injectors.

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“…Although the difference between the sac pressure and rail pressure is negligibly small when the needle lift is sufficient, the sac pressure increases dramatically from zero with the needle lift increasing while the rail pressure is kept at almost constant during the initial stage of injection. [19][20][21] As a result, the above models for the quasi-steady jets give unacceptable predictions for S tip at the injection startup. 22 This limitation seems to have been accepted by the above studies based on the singlehole nozzle with relatively long injection duration, when the ramp-up processes account for a relatively small portion of the whole injection processes.…”

Section: Introductionmentioning

confidence: 99%

Modeling of diesel spray tip penetration during start-of-injection transients

2020

International Journal of Engine Research

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Multiple-injection strategy that has been applied widely in diesel engines usually features a short duration for each injection pulse. As a result, the shortened injection makes the needle opening and closing transients increasingly important for spray in an injection event. Owing to the needle movement, the spray development during the transient processes is complex and quite different from the spray at the quasi-steady state. However, so far modeling of the spray development during the transient processes is far from adequate. Particularly, a theoretical zero-dimensional (0-D) spray tip penetration model considering the needle opening and sac pressurization processes as well as ambient and injection conditions during the start-of-injection (SOI) transients is still absent. In this paper, considering the sac pressurization processes, the 0-D model of spray tip penetration during the SOI transients is derived. Then, the model is validated against the experimental spray data using a long-distance microscope together with an ultrahigh speed CMOS camera. The model and experimental results show that the spray tip penetration shows a t3/2 dependence at the initial stage of injection rather than the t dependence suggested by Hiroyasu’s model. Later, the spray tip penetration shows a t3/4 dependence owing to the spray breakup, and a t1/2 dependence with the completion of sac pressurization. The models and analysis are believed to provide new insights into the transient spray behaviors and valuable reference for engineers and researchers who are considering the model-based development of next-generation diesel engines.

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First observation and characterization of vortex flow in steel micronozzles for high-pressure diesel injection

Cited by 27 publications

References 20 publications

Droplet size decrease rate of secondary breakup in diesel fuel sprays

Droplet size decrease rate of secondary breakup in diesel fuel sprays

Effect of the In-Cylinder Back Pressure on the Injection Process and Fuel Flow Characteristics in a Common-Rail Diesel Injector Using GTL Fuel

Modeling of diesel spray tip penetration during start-of-injection transients

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