High-Speed PIV Evaluation of Fuel Sprays under Superheated Conditions

( Ming Zhang ),( Min Xu ),( Yu Yin Zhang ),( Gao Ming Zhang ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-

Spray structure, distribution, and atomization process of the superheated sprays are dramatically influenced by the degree of the fuel superheating. The fuel spray flow field can provide detailed information about such influence due to the fuel superheating. It is anticipated that the fuel spray flow field depends on the superheat degree, which is carefully examined using high-speed PIV in this study. The fuel droplet velocities are measured within the lower number density regions of the spray generated from a multi-hole injector. The spray structure is characterized by spray penetration, maximum spray width and spray angle derived from the spray laser-sheet images. These characteristics are correlated with the spray velocity vector field to analyze the driving force of the spray transformation. The results illustrate that, as the superheat degree increases, the spray velocities in both radial and axial directions vary dramatically accompanied by the unexpected transformations of the spray structure, such as transforming from separate plumes to a collapsed form. The superheat degree is the predominant factor influencing break-up, atomization, and structure of the superheated sprays.

압력선회노즐에서 물-기름 유화연료의 분무특성

임정현 ( J. H. Rhim ),노수영 ( S. Y. No ) 한국액체미립화학회 2000 한국액체미립화학회지 Vol.5 No.1

The beneficial aspects of applying emulsion fuels to combustion systems may be due to the changes of fuel properties which lead to the enhanced atomization characteristics. The spray characteristics of water/oil emulsified fuel injected from the pressure-swirl(simplex) atomizer using for oil burner were investigated. Four different water contents from 10 to 40 % by volume at 10% increment were prepared by mixing with the different contents of surfactants. Total amount of surfactant used was varied from 1 to 3 % by volume. This study demonstrates the influence of water and surfactant contents of emulsified fuel, injection pressure on the spray characteristics, i.e. Sauter mean diameter(SMD) and spray angle. The drop size distribution of the emulsified fuel spray was measured with a Malvem particle sizer. In order to measure the spray angle, the digital image processing was employed by capturing multiple images of the spray with 3-CCD digital video camera. It was evident that the addition of water and surfactant changes fuel properties which are the key parameters influencing the atomization of the spray. The increase in surfactant content results in the decrease of SMD and the increase in spray angle. The droplets decease with increase in injection pressure, but the influence of injection pressure in this experimental condition was less important than expected. The more viscous fuel with the increase of water content exhibits the larger droplets in the centerline of the spray, and the less viscous fuel in the outer edges of the spray. The increase in axial position from the nozzle causes the spray angle to decrease. The spray angle decreases with increase in water content. This is due to increase in viscosity with increase in water content.

Spray distortion effect on particulate emission in stratified combustion of n-butane

( Sangjae Park ),( Jinyoung Jung ),( Choongsik Bae ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

To obtain spray robustness for fuel injection directly in engine cylinders, typical hollow cone injectors are used in several direct injection engine, especially for advanced gasoline direct injection engine. In terms of lean stratified combustion, the robustness would be major factor for mixture formation process, which has significant impact on particulate matter emission. Dedicated injector nozzle design for gasoline fuel showed small sensitiveness for spray structure of the injected fuel, but if other fuel, such as liquefied petroleum gas, a typical with high vapor pressure, is used with same injector, the spray structures were distorted from typically designed spray configuration. Intuitively, spray tip vortexes were formed near to injector tip compared to liquid fuel spray, and they showed shorter liquid penetration than those of liquid fuel spray. But, in terms of inner structure of hollow cone spray, there are more severe distortion those of outer surface, due to the overlap of inner vortexes. The overlap could affect whole spray structure by filling the hollow space with fuel cloud, so that the vapor cloud of fuel behaved as a typical kind of full cone spray. These phenomena caused deterioration of mixture formation between surrounding air and fuel vapor, which could affect particulate formation within the combusted by ignitor. These effects were not majorly observed in particulate mass emission, but in particulate number emission the large difference could be observed by that effect. These distortion could be evaluated indirectly by observing side structure of spray, in these case, larger mixing time causes more particulate emission, contradictively.

DIESEL SPRAY CHARACTERISTICS AND ITS COMBUSTION

Masataka ARAI 한국자동차공학회 2005 한국자동차공학회 Workshop Vol.2005 No.-

Spray formation mechanism of a diesel spray and its combustion process were reviewed. Spray formation mechanism of the diesel spray was controlled by a cavitation inside an injection nozzle. The Sauter mean diameter of a diesel spray became small when the cavitation occurred in the nozzle and it resulted in a complete spray. The empirical equations of the Sauter mean diameter were shown with the discussion of the cavitation. The spray tip penetrations of free and wall impingement sprays were introduced with the equations. The spray tip penetration was discussed with air entrainment process. Impingement spray was discussed with penetration and adhering fuel on the wall. High pressure injection spray was introduced with its spray characteristics. Spray-to spray interaction was clearly shown by many photographs to propose a new spray system. Evaporation process on an impingement wall was duscused. Ignition delay and the empirical equations of it were reviewed. The ignition delay was greatly affected by the spray movement and surrounding conditions. Wall and residual gas effects on the ignition delay were reviewed. The OH flame kernel and hot flame kernel observed at the ignition of impingement spray were explained. Alos, effect of injection pressure and effect of wall impingement on flame development process was explained.

분무응용 기술 : 바이오 디젤의 수평분무 이미지 분석

윤석주 ( Suckju Yoon ),황창영 ( Changyeong Hwang ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-

This paper presents the possibility of bio-diesel which has high viscosity and oxygenated fuel by gun-type burner. The experiments were carried out for the comparison of the spray characteristics of the kerosene, lard, and soybean fuel injected from the pressure swirl nozzle of gun-type burner. The spray images were acquired by the high speed camera and changes of injection pressures and blending rate. In the horizontality direction spray different from vertical direction spray, the flow of single spray in downstream was found. This flow was appeared by the generation of primary spray and secondary spray. The primary spray has an influence of initial spray condition and secondary spray was shown by correlation of primary spray and nearby air.

A study on the macroscopic spray behavior and atomization characteristics of biodiesel and dimethyl ether sprays under increased ambient pressure

Kim, H.J.,Park, S.H.,Lee, C.S. Elsevier Scientific Pub. Co 2010 Fuel processing technology Vol.91 No.3

The aim of this work is to investigate the spray behaviors of biodiesel and dimethyl ether (DME) fuels using image processing and atomization performance analysis of the two fuel sprays injected through a common-rail injection system under various ambient pressure conditions in a high pressure chamber. In order to observe the biodiesel and DME fuel spray behaviors under various ambient pressures, the spray images were analyzed at various times after the start of energization using a visualization system consisting of a high speed camera and two metal halide light sources. In addition, a high pressure chamber that can withstand a pressure of 4MPa was used for adjusting the ambient pressure. From the spray images, spray characteristics such as the spray tip penetration, cone angle, area, and contour plot at various light intensity levels were analyzed using image conversion processing. Also, the local Sauter mean diameters (SMD) were measured at various axial/radial distances from the nozzle tip by a droplet measuring system to compare the atomization performances of the biodiesel and DME sprays. The results showed that the ambient pressure had a significant effect on the spray characteristics of the fuels at the various experimental conditions. The spray tip penetration and spray area decreased as the ambient pressure increased. The contour plot of the biodiesel and DME sprays showed a high light intensity level in the center regions of the sprays. In addition, it was revealed that the atomization performance of the biodiesel spray was inferior to that of the DME spray at the same injection and ambient conditions.

ATOMIZATION PROCESS OF DIESEL FUEL SPRAY IN THE INITIAL STAGE OF INJECTION

KO K. N.,LEE C. S.,HUH J. C. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.1

An experimental investigation has been carried out to reveal the atomization process of the diesel fuel spray. The spray injected through a single hole nozzle was taken by a camera on the opposite side of a stroboscope for macroscopic observation or a nanolite for microscopic observation. The effect of nozzle aspect ratio was analyzed with disintegration phenomena of the diesel spray. Based on the enlarged spray photograph, atomization process was observed in detail and further the spray cone angle was measured under various ambient pressures. The result shows that atomization of diesel spray in early stage of injection is mainly progressed in the vicinity of spray periphery region except the region close to the nozzle exit and spray head region. The spray cone angle is nearly constant under the pressurized condition, while it decreases with elapsing time under the atmospheric condition.

Experimental and Numerical Study on Effects of Wall Impingement on Spray and Combustion Characteristics in a Diesel Engine

Liu, Yu,Chung, S.S.,Ha, J.Y. Institute for Liquid Atomization and Spray Systems 2010 한국액체미립화학회지 Vol.15 No.3

The spray-wall impingement in diesel engines is important to mixture preparation, engine performance and pollutant emissions. The purpose of this paper is to study the effects of spray-wall impingement on fuel distribution, combustion and emission characteristics by using both experimental and numerical methods. To investigate the spray-wall impingement process, an impingement-chamber was designed and a visualization experiment system was also developed. The images of impinged spray and free spray were digitally recorded with an intensified CCD camera. To investigate the fuel distribution, combustion and emission characteristics of impinged spray in a real diesel engine, the fuel injection and combustion processes of an engine with impingement-chamber were simulated by CFD software. Equivalence ratio distribution results were obtained to understand the fuel distribution characteristics of the impinged spray. Some combustion and emission characteristics were also acquired and the results showed that ignition delay of impinged spray was shorter than that of free spray; NO emission of the impinged spray was significantly less than that of free spray, but soot emission of impinged spray was more than that of the free spray. This study found that the diesel engine with spray-wall impingement has significant potential to reduce NO emission.

연료분무 및 연소 1 : 디젤 분무의 증발 / 비증발 특성 비교

김동훈 ( Dong Hoon Kim ),김기현 ( Ki Hyun Kim ),배충식 ( Choong Sik Bae ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

Diesel spray is a main phenomenon in a CI (compression ignition) engine. It is important to understand diesel spray characteristics inside the cylinder to design CI engines. Diesel fuel is directly injected into the cylinder by injectors in almost all CI engine. Diesel spray characteristics, such as liquid penetration length, spray angle and vapor distribution, directly affect combustion characteristics and these determine engine performance and emissions. Many researchers are studying fuel spray with experimental and numerical method. CFD method is one of the useful numerical tools to investigate internal combustion engines, recently. Many spray sub-models are derived to simulate fuel spray. Breakup models, evaporation models, collision models and wall-impingement models are included spray sub-models. To describe spray structure properly, it is important to use suitable spray sub-models in CFD code. In this study, diesel spray structure was calculated using OpenFOAM, which is a CFD package coded with C++ language. Kelvin-Helmholtz/Rayleigh-Taylor breakup model, standard evaporation model and O`Rourke collision model were used as spray sub-models to compare diesel spray characteristics in non-evaporating and evaporating condition inside the constant volume chamber. Evaporation model used in spray simulation is important to calculate liquid and vapor distribution inside the constant chamber. Calculated liquid length without evaporation model was less than those with evaporation model. Liquid length of spray was calculated accurately with evaporation model. Droplet sizes with evaporation model were slightly less than those without evaporation model. Evaporation model should be considered to simulate diesel spray even in non-evaporating condition.

Optimal Condition of Hydroxyapatite Powder Plasma Spray on Ti6Al4V Alloy for Implant Applications

Ahn, Hyo-Sok,Lee, Yong-Keun Materials Research Society of Korea 2012 한국재료학회지 Vol.22 No.4

Optimal conditions for HA plasma spray-coating on Ti6Al4V alloy were investigated in order to obtain enhanced bone-bonding ability with Ti6Al4V alloy. The properties of plasma spray coated film were analyzed by SEM, XRD, surface roughness measurement, and adhesion strength test because the film's transformed phase and crystallinity were known to be influential to bone-bonding ability withTi6Al4V alloy. The films were formed by a plasma spray coating technique with various combinations of plasma power, spray distance, and auxiliary He gas pressure. The film properties were analyzed in order to determine the optimal spray coating parameters with which we will able to achieve enhanced bone-bonding ability with Ti6Al4V alloy. The most influential coating parameter was found to be the plasma spray distance to the specimen from the spray gun nozzle. Additionally, it was observed that a relatively higher film crystallinity can be obtained with lower auxiliary gas pressure. Moderate adhesion strength can be achievable at minimal plasma power. That is, adhesion strength is minimally dependent on the plasma power. The combination of shorter spray distance, lower auxiliary gas pressure, and moderate spray power can be recommended as the optimal spray conditions. In this study, optimal plasma spray coated films were formed with spray distance of 70 mm, plasma current of 800 A, and auxiliary gas pressure of 60 psi.