scholarly journals Experimental study on flash-boiling spray structure of multi-hole gasoline direct injection injector in a constant volume chamber

2020 ◽  
Vol 12 ◽  
pp. 175682772093243
Author(s):  
Jian Wu ◽  
Jiakun Du ◽  
Hong Chen ◽  
Yuhuai Li ◽  
Wenfeng Zhan ◽  
...  
Keyword(s):  
Optical Measurement ◽  
Ambient Pressure ◽  
Direct Injection ◽  
Measurement Techniques ◽  
Gasoline Direct Injection ◽  
Fuel Temperature ◽  
Droplet Distribution ◽  
Spray Structure ◽  
Significant Difference ◽  
Flash Boiling

The macroscopic and microscopic characteristics of flash-boiling spray were experimentally investigated with various optical measurement techniques. The effects of ambient pressure and fuel temperature on flash-boiling characteristics in multi-hole gasoline direct injection injector were analyzed. The analysis was focused on the spray structure and atomization droplet size distributions. In order to increase the understanding of the flash-boiling spray targeting, three injectors with different spray patterns were investigated under strong flash-boiling condition. The results show that ambient pressure and fuel temperature have significant influence on flash boiling. Both lower ambient pressure and higher fuel temperature could accelerate the flash-boiling process. For the macroscopic characteristics, similar influences could be found with the ambient pressure decreased by 0.4 bar and the fuel temperature increased by 10°C. Further, significant difference could be found within cold-jet spray and strong flash-boiling spray, such as the spatial structure. The spray structure always turns from hollow cone into solid when flash boiling occurs. With a higher fuel superheat degree, the spray droplet distribution moves toward smaller sizes and let the larger droplets reduce due to the promotion of atomization. For the strong flash-boiling spray, the Sauter mean diameter has decreased by 50% compared with cold-jet spray. There is a corresponding relationship between collapsed flash-boiling spray target and weighted geometric center of the injector. Spray collapse could be avoided by increasing the plume distance.

Prediction of spray collapse in multi-hole gasoline direct-injection fuel injectors

2018 ◽  
Vol 20 (1) ◽  
pp. 18-33 ◽  
Author(s):  
Sampath K Rachakonda ◽  
Arman Paydarfar ◽  
David P Schmidt
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Ambient Pressure ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Nozzle Geometry ◽  
Fuel Injectors ◽  
Computational Fluid Dynamics Simulations ◽  
Flash Boiling ◽  
Dynamics Simulations

A parametric study was conducted to predict the conditions leading to spray collapse in multi-hole gasoline direct-injection fuel injectors using computational fluid dynamics simulations. The computational fluid dynamics simulations were performed using an in-house multi-dimensional code that accounts for thermal non-equilibrium and entrainment of the non-condensable gas and coupled with primary atomization. The simulations were performed for a fixed injection pressure and fuel temperature on nine different six-hole injectors. The parameters were varied to include the effects of the ratio of the ambient pressure to the saturation pressure (Pa/Ps), the drill angle, and the diameters of the nozzle and the counter bore, respectively, on the spray. The findings indicate that spray collapse results from a combination of the nozzle geometry, the thermodynamic conditions of the fuel, and the ambient pressure. Spray collapse was observed in injectors with a narrow arrangement of the nozzle holes under extreme flash-boiling conditions with very low ambient pressures and in the case of non-flash-boiling conditions with very high ambient pressures.

scholarly journals Numerical Analysis of GDI Flash Boiling Sprays Using Different Fuels

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5925
Author(s):  
Raul Payri ◽  
Pedro Marti-Aldaravi ◽  
Rami Abboud ◽  
Abian Bautista
Keyword(s):  
Alternative Fuels ◽  
Fuel Injection ◽  
Ambient Pressure ◽  
Direct Injection ◽  
Saturation Pressure ◽  
Combustion Process ◽  
Gasoline Direct Injection ◽  
Injection Process ◽  
Engine Combustion ◽  
Flash Boiling

Modeling the fuel injection process in modern gasoline direct injection engines plays a principal role in characterizing the in–cylinder mixture formation and subsequent combustion process. Flash boiling, which usually occurs when the fuel is injected into an ambient pressure below the saturation pressure of the liquid, is characterized by fast breakup and evaporation rates but could lead to undesired behaviors such as spray collapse, which significantly effects the mixture preparation. Four mono–component fuels have been used in this study with the aim of achieving various flashing behaviors utilizing the Spray G injector from the Engine Combustion Network (ECN). The numerical framework was based on a Lagrangian approach and was first validated for the baseline G1 condition. The model was compared with experimental vapor and liquid penetrations, axial gas velocity, droplet sizes and spray morphology and was then extended to the flash boiling condition for iso–octane, n–heptane, n–hexane, and n–pentane. A good agreement was achieved for most of the fuels in terms of spray development and shape, although the computed spray morphology of pentane was not able to capture the spray collapse. Overall, the adopted methodology is promising and can be used for engine combustion modeling with conventional and alternative fuels.

Effects of nozzle hole configuration of a multi-hole type gasoline direct injector on spray development under flash boiling conditions

2020 ◽  
pp. 146808742096002
Author(s):  
Donghwan Kim ◽  
Sungwook Park
Keyword(s):  
Ambient Pressure ◽  
Mie Scattering ◽  
Prediction Equation ◽  
Width Ratio ◽  
Fuel Temperature ◽  
Spray Structure ◽  
Closed Type ◽  
Nozzle Hole ◽  
Flash Boiling ◽  
Overlapped Region

The flash boiling phenomenon is critically affected by not only injection conditions such as fuel temperature, ambient pressure and physical properties of fuel but also the nozzle hole configurations of the injector. In this research, two kinds of injectors, having different nozzle hole configurations (a closed type and a opened type) were used to analyze the influence of flash boiling. Near-field and far-field spray visualization was performed using a high-speed camera based on the Mie-scattering imaging technique. Test parameters were injection pressure, ambient pressure, and fuel temperature. The spray length, spray width, length-to-width ratio, and axial velocity of spray development depending on time were measured using the MATLAB program for quantitative and objective analysis. Finally, the prediction equation for the spray length was derived using the least-squares method based on the experimental results. In the case of the closed type injector, the spray center contained a wide overlapped region because of the strong links between plumes. On the other hand, with the opened type injector, there was a relatively narrow overlapped region between plumes due to weak interaction between plumes. As a result, the closed type injector had a narrow and long spray structure and the opened type injector had a partially long and wide spray structure. According to the prediction equation, the spray develops depending on time more linearly under flash boiling conditions than under non-flash boiling conditions. The influence of flash boiling was smaller in the closed type injector because the closed type injector has less variation of the spray structure with varying injection conditions, ranging from non-flash boiling conditions to non-flash boiling conditions.

Optical investigation of flash boiling and its effect on in-cylinder combustion for butanol isomers and iso-octane

2020 ◽  
pp. 146808742091724
Author(s):  
Rakesh Kale ◽  
Raja Banerjee
Keyword(s):  
Physical Properties ◽  
Fuel Injection ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Optical Investigation ◽  
Fuel Injector ◽  
Fuel Temperature ◽  
Piston Head ◽  
Flash Boiling ◽  
Thermo Physical Properties

Performance of a gasoline direct injection engine significantly depends on the fuel injection phenomenon. It has been shown that variation in the fuel thermo-physical properties and in-cylinder thermodynamic conditions can adversely affect engine performance. Spray collapse due to flash boiling is the consequence of such varying in-cylinder thermodynamics. It has also been observed that gasoline direct injection engines have higher particulate matter emissions compared to port fuel injection engines. One of the possible reasons for this observation may be fuel impingement on the piston head and spray collapse at high fuel injector temperature. In the present work, experiments have been performed to understand spray characteristics under flash boiling conditions and ultimately its effect on in-cylinder combustion quality for the three different fuels: n-butanol, iso-butanol and iso-octane. To mimic in-cylinder conditions, hot fuel was introduced inside an optically accessible engine. It was observed that fuel temperature and their thermo-physical properties have a significant effect on piston head wetting and pool fire on the piston top. Butanol isomers showed significant reduction in sooty combustion with increase in fuel temperature. However, iso-octane showed higher wall wetting at elevated fuel temperature due to spray collapse.

scholarly journals Flashboiling atomization in nozzles for GDI engines

2017 ◽  
Author(s):  
Sebastian Bornschlegel ◽  
Chris Conrad ◽  
Lisa Eichhorn ◽  
Michael Wensing
Keyword(s):  
Penetration Depth ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Ambient Pressure ◽  
Rapid Expansion ◽  
Gasoline Direct Injection ◽  
Coolant Temperature ◽  
Concentrated Mass ◽  
Flash Boiling ◽  
Gdi Engines

Flashboiling denotes the phenomenon of rapid evaporation and atomization at nozzles, which occurs when fluidsare injected into ambient pressure below their own vapor pressure. It happens in gasoline direct injection (GDI) engines at low loads, when the cylinder pressure is low during injection due to the closed throttle valve. The fuel temperature at the same time approaches cylinder head coolant temperature due to the longer dwell time of the fuel inside the injector. Flash boiling is mainly beneficial for atomization quality, since it produces small droplet sizes and relative broad and homogenous droplet distributions within the spray. Coherently, the penetration depth normally decreases due to the increased aerodynamic drag. Therefore the thermal properties of injectors are often designed to reach flash boiling conditions as early as possible. At the same time, flash boiling significantly increases the risk of undesired spray collapsing. In this case, neighbouring jets converge and form a single jet. Due to the now concentrated mass, penetration depth is enhanced again and can lead to liner or piston wetting in addition to the overall diminished mixture formation.In order to understand the underlying physics, it is important to study the occurring phenomena flashboiling and jet-to-jet interacting i.e. spray collapsing separately. To this end, single hole injectors are built up to allow for an isolated investigation of flashboiling. The rapid expansion at the nozzle outlet is visualized with a microscopic high speed setup and the forces that lead to the characteristic spray expansion are discussed. Moreover, the results on the macroscopic spray in terms of penetration, cone angles and vapor phase are shown with a high speed Schlieren setup. Resulting droplet diameters and velocities are measured using LDA/PDA.As a result, we find a comprehensive picture of flash boiling. The underlying physics can be described and discussed for the specific case of high pressure injection at engine relevant nozzle geometries and conditions, but independently from neighbouring jets. These findings provide the basis to understand and investigate flashboilingand jet-to-jet interaction as distinct, but interacting subjects rather than a combined phenomenon.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4750 

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

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.

scholarly journals Time-dependent line-of-sight extinction tomography for multi-hole GDI injectors

2016 ◽  
Vol 9 (3) ◽  
pp. 199-211 ◽  
Author(s):  
Yudaya Sivathanu ◽  
Jongmook Lim ◽  
Varun Kulkarni
Keyword(s):  
Ambient Temperature ◽  
Direct Injection ◽  
Injection Pressure ◽  
Gasoline Direct Injection ◽  
Time Dependent ◽  
Line Of Sight ◽  
Experimental Measurements ◽  
Fuel Injectors ◽  
Factors Affecting ◽  
Spray Structure

Finely atomized sprays from multi-hole gasoline direct injection (GDI) fuel injectors make them an ideal choice for automobile applications. A knowledge of the factors affecting the performance of these injectors is hence important. In the study presented here, we employ statistical extinction tomography to examine the transient characteristics of two GDI fuel injectors with five and six holes. Two axial locations, 25 mm and 35 mm from the injector exit, are chosen for experimental measurements, and the dependence of injection pressure and ambient temperature on plume locations and angles is examined from these measurements. A pressure chamber with opposing windows is used which permits the nozzle to be rotated 12 times (30° each rotation) to obtain information on the complete spray structure. Additionally, the plume centroid locations are measured and compared with those obtained with a mechanical patternator. The centroid locations from the two instruments compare favorably.

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