Visualization of Spray Structure at the Outlet of the Micro Orifices

2015 ◽  
Author(s):  
Morteza Ghorbani ◽  
Ali Koşar
Keyword(s):  
High Speed ◽  
Bubbly Flow ◽  
Injection Pressure ◽  
Experimental Investigations ◽  
Small Scale ◽  
Spray Characteristics ◽  
Visualization System ◽  
Spray Formation ◽  
Cavitation Phenomenon ◽  
Visualization Techniques

Spray formation occurring at the outlet of short microchannels/micro orifices due to the cavitation phenomenon is of great importance in biomedical and engineering applications. The spray characteristics are affected dramatically by the flow regime in the micro orifice. If properties of the flow are identified in the outlet of the nozzle, the treatment of the spray can be predicted. These properties can be used as boundary conditions. The experimental investigations show that the cavitation phenomenon occurs in the orifice and strongly affects the spray characteristics. However, visualization of the spray at the outlet of the micro orifice is a challenging task, since the phenomena related to the spray are occurred in very small scale and also the region near to the micro orifice is not clear. Therefore there is an urgent need to new and advanced visualization techniques and measurement equipments. In this study, spray formation and atomization, bubble evolution at the outlet of a short microchannel of an inner diameter of 152 μm were experimentally studied at different injection pressures with the use of a high speed visualization system. High speed visualization was performed at four different segments to cover ∼15 mm distance beginning from the microchannel outlet to understand the spray formation mechanism. It was observed that cavitating bubbly flow is strongly affected by injection pressure. Up to an injection pressure of 50 bars bigger size droplets form at the outlet, while beyond 50 bar injection pressure, cavitation erosion of intensified cavitation becomes dominant leading to smaller droplet sizes and a more conical spray. The results showed a good agreement with previous studies. This energy could be exploited in several applications, where destructive effects of bubbly cavitating flows are needed.

Review of the Investigation of Fuel-Air Premixing and Combustion Process Using Rapid Compression Machine and Direct Visualization System

2013 ◽  
Vol 465-466 ◽  
pp. 265-269 ◽  
Author(s):  
Mohamad Jaat ◽  
Amir Khalid ◽  
Bukhari Manshoor ◽  
Siti Mariam Basharie ◽  
Him Ramsy
Keyword(s):  
High Speed ◽  
Combustion Engine ◽  
Early Stage ◽  
Combustion Process ◽  
Injection Pressure ◽  
Rapid Compression Machine ◽  
Mixture Formation ◽  
Visualization System ◽  
Optical Visualization ◽  
Rapid Compression

s :This paper reviews of some applications of optical visualization system to compute the fuel-air mixing process during early stage of mixture formation and late injection in Diesel Combustion Engine. This review has shown that the mixture formation is controlled by the characteristics of the injection systems, the nature of the air swirl and turbulence in thecylinder, and spray characteristics. Few experimental works have been investigated and found that the effects of injection pressure and swirl ratio have a great effect on the mixture formation then affects to the flame development and combustion characteristics.This paper presents the significance of spray and combustion study with optical techniques access rapid compression machine that have been reported by previous researchers. Experimental results are presentedin order to provide in depth knowledge as assistance to readers interested in this research area. Analysis of flame motion and flame intensity in the combustion chamber was performed using high speed direct photographs and image analysis technique. The application of these methods to the investigation of diesel sprays highlights mechanisms which provide a better understanding of spray and combustion characteristics.

Ignition of Diesel Pilot Fuel in Dual-Fuel Engines

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Marcus Grochowina ◽  
Daniel Hertel ◽  
Simon Tartsch ◽  
Thomas Sattelmayer
Keyword(s):  
High Speed ◽  
Measurement Techniques ◽  
Injection Pressure ◽  
Operating Conditions ◽  
Dual Fuel ◽  
Spray Formation ◽  
Fuel Concentration ◽  
Injection Parameters ◽  
Pilot Fuel ◽  
Ignition And Combustion

Dual-fuel (DF) engines offer great fuel flexibility combined with low emissions in gas mode. The main source of energy in this mode is provided by gaseous fuel, while the diesel fuel acts only as an ignition source. For this reason, the reliable autoignition of the pilot fuel is of utmost importance for combustion in DF engines. However, the autoignition of the pilot fuel suffers from low compression temperatures caused by Miller valve timings. These valve timings are applied to increase efficiency and reduce nitrogen oxide (NOx) emissions. Previous studies have investigated the influence of injection parameters and operating conditions on ignition and combustion in DF engines using a unique periodically chargeable combustion cell. Direct light high-speed images and pressure traces clearly revealed the effects of injection parameters and operating conditions on ignition and combustion. However, these measurement techniques are only capable of observing processes after ignition. In order to overcome this drawback, a high-speed shadowgraph technique was applied in this study to examine the processes prior to ignition. Measurements were conducted to investigate the influence of compression temperature and injection pressure on spray formation and ignition. Results showed that the autoignition of diesel pilot fuel strongly depends on the fuel concentration within the spray. The high-speed shadowgraph images revealed that in the case of very low fuel concentration within the pilot spray, only the first stage of the two-stage ignition occurs. This leads to large cycle-to-cycle variations and misfiring. However, it was found that a reduced number of injection holes counteract these effects. The comparison of a diesel injector with ten-holes and a modified injector with five-holes showed shorter ignition delays, more stable ignition and a higher number of ignited sprays on a percentage basis for the five-hole nozzle.

Effect of ultra-high injection pressure up to 50 MPa on macroscopic spray characteristics of a multi-hole gasoline direct injection injector fueled with ethanol

2017 ◽  
Vol 232 (8) ◽  
pp. 1092-1104 ◽  
Author(s):  
Xiang Li ◽  
Yi-qiang Pei ◽  
Jing Qin ◽  
Dan Zhang ◽  
Kun Wang ◽  
...  
Keyword(s):  
High Speed ◽  
Direct Injection ◽  
Cone Angle ◽  
Injection Pressure ◽  
Fuel Mixture ◽  
Gasoline Direct Injection ◽  
Spray Characteristics ◽  
High Injection ◽  
High Injection Pressure ◽  
Wall Impingement

This research systematically studied the effect of injection pressure on macroscopic spray characteristics of a five-hole gasoline direct injection (GDI) injector fueled with ethanol, especially under ultra-high injection pressure up to 50 MPa. The front and side views of sprays were photographed by the schlieren method using a high-speed camera. Various parameters, including spray development stages, cone angle, penetration, area and irregular ratio, were fully analyzed to evaluate macroscopic characteristics of the whole spray and spray core with varying injection pressure. The results demonstrated that the effect of ultra-high injection pressure on macroscopic spray characteristics was significant. As injection pressure increased from 10 MPa to 50 MPa, the occurrence time of branch-like structure decreased; the cone angle increased little; the area increased significantly; the area ratio dropped by 6.4 and 5.8 percentage points on average for the front view and side view spray, respectively. There was a significant increase in the trend for penetration as the injection pressure rose from 10 MPa to 30 MPa. However, this trend became weak when the injection pressure further increased. The penetration ratio under ultra-high injection pressure was slightly higher than it was under 10 or 20 MPa. Ultra-high injection pressure would not obviously raise the possibility of spray/wall impingement, but led to the impingement quantity increasing to some extent. Increasing injection pressure could enhance the vortex scale, finally resulting in better air/fuel mixing quality. Ultra-high injection pressure was a potential way to improve air/fuel mixture homogeneity for a GDI injector fueled with ethanol.

Experimental Study on Spray Characteristics of Diesel Engines and Analysis of Fuel Dripping Phenomenon

2014 ◽  
Vol 1078 ◽  
pp. 271-275 ◽  
Author(s):  
Yu Qiang Wu ◽  
Qian Wang ◽  
Zhi Sheng Gao ◽  
Zhou Rong Zhang ◽  
Li Ming Dai
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Cone Angle ◽  
Digital Camera ◽  
Injection Pressure ◽  
Fuel Mixture ◽  
Long Distance ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone

Experimental study on macroscopic spray characteristics of a certain type of domestic common rail injectors under the conditions of different injection pressures was carried out through a high-speed digital camera. Furthermore, a fuel dripping phenomenon at the end stage of injection was observed through the high-speed digital camera equipped with a long-distance microscope, and a further analysis of the phenomenon was made. The results show the increase in the injection pressure can evidently enhance spray cone angle and expand the scope of spray field in combustion chamber, which is conducive to air-fuel mixture. The spray cone angle during the development spray shows a double-peak shape. And the long response-time of seating of solenoid valve core that disables the injection cutting off in time is one of factors causing fuel dripping phenomenon.

Application of an Arbitrary Lagrangian Eulerian Method to Describe High Velocity Gas-Particle Flow Behavior

2011 ◽  
Author(s):  
D. M. Fox ◽  
J. S. Lee
Keyword(s):  
High Velocity ◽  
High Speed ◽  
Flow Behavior ◽  
Constitutive Models ◽  
Experimental Investigations ◽  
Small Scale ◽  
Arbitrary Lagrangian Eulerian ◽  
High Velocity Flow ◽  
Solid Objects ◽  
Velocity Flow

Novel computational and small-scale experimental investigations were performed in order to better understand the high velocity flow behavior of gas-particle mixtures. The motion of solid objects impacted by the flow of the mixtures was measured by use of high-speed digital video photography. Computations were performed by use of an arbitrary Lagrangian Eulerian (ALE) treatment in a nonlinear finite element code. Constitutive models for description of the solid component of the gas-particle blend were developed based on quasi-statically determined test results. It was observed that there was very close agreement between experimental and computational results and that it was possible to accurately predict the high velocity flow behavior of the gas-particle mixture using quasi-statically determined constitutive models.

Experimental Study on Spray Characteristics of N-Butanol/Acidic Oil/Diesel Blends

2014 ◽  
Vol 1008-1009 ◽  
pp. 1001-1005 ◽  
Author(s):  
Jian Wu ◽  
Yang Hua ◽  
Zhan Cheng Wang ◽  
Li Li Zhu ◽  
Wei Wei Shang
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Cone Angle ◽  
Injection Pressure ◽  
Air Entrainment ◽  
Mixing Ratio ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Spray Penetration

In order to better research on the spray characteristics of biodiesel and n-butanol blends, an experimental study of spray characteristics of different fuel mixtures was investigated in a constant volume vessel using high speed photograph method, and analyzed the influence of different proportions of acidic oil biodiesel and n-butanol on the macroscopic parameters of spray penetration, spray cone angle and so on. The results show that with the increase of acidic oil biodiesel ratio, the air entrainment is weakened, spray penetration gradually increases and spray cone angle decreases under the same injection pressure and back pressure. After adding n-butanol in acidic oil biodiesel and diesel mixture fuel, the surrounding air entrainment is enhanced, and spray front end widen. With the increase of mixing ratio, spray penetration increases first, then decreases. The spray cone angle increases after adding n-butanol, and decreases with the increase of mixing ratio. The results show that adding n-butanol can be used as one of the methods to improve biodiesel spray characteristics.

scholarly journals Influences of hydrodynamic conditions, nozzle geometry on appearance of high submerged cavitating jets

2013 ◽  
Vol 17 (4) ◽  
pp. 1139-1149 ◽  
Author(s):  
Ezddin Hutli ◽  
Salem Abouali ◽  
Ben Hucine ◽  
Mohamed Mansour ◽  
Milos Nedeljkovic ◽  
...  
Keyword(s):  
Digital Camera ◽  
Injection Pressure ◽  
Nozzle Geometry ◽  
Geometrical Parameters ◽  
Main Role ◽  
Visualization System ◽  
Divergent Flow ◽  
Cavitation Phenomenon ◽  
And Performance ◽  
Cavitating Jet

Based on visualization results of highly-submerged cavitating water jet obtained with digital camera, the influences of related parameters such as: injection pressure, nozzle diameter and geometry, nozzle mounting (for convergent / divergent flow), cavitation number and exit jet velocity, were investigated. In addition, the influence of visualization system position was also studied. All the parameters have been found to be of strong influence on the jet appearance and performance. Both hydro-dynamical and geometrical parameters are playing the main role in behavior and intensity of cavitation phenomenon produced by cavitating jet generator. Based on our considerable previous experience in working with cavitating jet generator, the working conditions were chosen in order to obtain measurable phenomenon.

DESIGN, DEVELOPMENT AND PERFORMANCE EVALUATION OF NEW SWIRL EFFERVESCENT INJECTOR

2015 ◽  
Vol 75 (1) ◽  
Author(s):  
Z. A. Ghaffar ◽  
Salmiah Kasolang ◽  
A. H. A. Hamid ◽  
C. S. Ow ◽  
N. R. Nik Roselina
Keyword(s):  
High Speed ◽  
Injection Pressure ◽  
Internal Flow ◽  
Working Fluid ◽  
Design Development ◽  
Spray Characteristics ◽  
Breakup Length ◽  
Swirl Chamber ◽  
Design Attributes ◽  
And Performance

The swirl effervescent injector has more desirable characteristics because it allows a system to run on low injection pressure and yet is still able to achieve an efficient atomization. In previous studies on other types of injectors, spray breakup length was reported as one of the important spray characteristics since a shorter spray breakup length tend to provide an earlier atomization. However, intensive studies on spray characteristics of the swirl effervescent injector are scarce. This paper is intended to describe the geometrical design procedures and performance assessments of a newly developed swirl effervescent injector. In designing the injector, a similitude technique was deployed to find the best design attributes among 4 existing injectors. The desired attributes were incorporated into the development of the injector. The swirl chamber was made from Perspex to permit visualization of the internal flow. A test rig was built to evaluate the injector’s performance. Water was used as the working fluid and nitrogen gas as the atomizing agent. The spray breakup characteristics were observed at different GLR and recorded using high-speed shadowgraph technique. For the analyses of the video recordings and the conversion into image sequences, ImageJ and specific software have been deployed. It was found that the introduction of the swirl-generating vane prior to the discharge orifice has assisted in shortening the spray breakup length at any amount of GLR.  

Parametric Investigation of Circumferential Grooves on Compressor Rotor Performance

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Yanhui Wu ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Qingpeng Li
Keyword(s):  
Numerical Investigation ◽  
High Speed ◽  
Orthogonal Experiment ◽  
Experimental Investigations ◽  
Small Scale ◽  
Stall Margin ◽  
Compressor Rotor ◽  
Set Up ◽  
Compound Effect ◽  
Unloading Effect

This paper presents numerical and experimental investigations about grooved casing treatment with the help of a high-speed small-scale compressor rotor. First, the numerical investigation seeks to offer a contribution of understanding the working mechanism by which circumferential grooves improve stall margin. It is found that stall margin gain due to the presence of circumferential grooves arises from the suction-injection effect and the near-tip unloading effect. Based on that, the philosophy of design of experiment is then set up. Finally, parametric studies are carried out through systematical experiments. It is found that the orthogonal experiment and the factorial analyses are successful in identifying the “best casing configuration” in terms of stall margin improvement. However, the ineffectiveness of the deduction from simulations suggests that the secondary flow circulations on stall margin gain should not be neglected, and the overall contribution of each groove to stall margin gain depends on its unloading effect and the compound effect of suction-injection. Further numerical investigation will focus on how to set up quantitative criteria to evaluate the compound effect of suction-injection and the unloading effect on stall margin gain respectively in each groove.

scholarly journals Effect of Nozzle Outlet Shape on Cavitation Behavior of Submerged High-Pressure Jet

Machines ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 4
Author(s):  
Gaowei Wang ◽  
Yongfei Yang ◽  
Chuan Wang ◽  
Weidong Shi ◽  
Wei Li ◽  
...  
Keyword(s):  
High Pressure ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Small Scale ◽  
High Speed Photography ◽  
Nozzle Outlet ◽  
Time Frequency ◽  
Cavitation Phenomenon ◽  
Cavitation Behavior ◽  
Organ Pipe

A submerged high-pressure water jet is usually accompanied by severe cavitation phenomenon. An organ pipe nozzle can greatly improve the cavitation performance of the jet, making use of the self-excited oscillation of the flow. In order to study the effect of organ pipe nozzles of different nozzle outlet shapes on cavitation behavior of submerged high-pressure jet, in this paper we build a high-pressure cavitation jet experiment system and carried out a high-speed photography experiment to study cavitation cloud characteristics of a high-pressure submerged jet. Two organ pipe nozzles with and without a whistle were compared. The dynamic characteristics of the cavitation cloud was extracted through the POD method, it was found that the result effectively reflect the dynamic characteristics of the cavitation jet. The reconstruction coefficients of mode-1 obtained by the POD can better reflect the periodic time-frequency characteristics of cavitation development. The effect of the nozzle outlet shape on the cavitation behavior of organ pipe nozzle was analyzed based on unsteady numerical simulation, and it was found that the jet generated by the nozzle with a divergent whistle had a larger vorticity in the shear layer near the outlet. Further, stronger small-scale vortex and much severe cavitation occurred from the nozzle with a divergent whistle.

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