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Macroscopic visualization of non-evaporating spray was carried out experimentally to investigate spray tip penetration and spray angle in term of low density condition corresponding to the early injection strategy. In addition, injectors with different injection angle, which refer to spray included angle, (146° and 70°) and number of hole (8 and 14) were applied to study the effect of the injector configuration. Compared with 8H146, which is regarded as baseline injector with 8 holes and 146° injection angle, spray tip penetration for 8H70 injector showed longer that for 8H146. It is attributed higher momentum and velocity due to smooth flow field in sac volume and nozzle, which was located closer to injector tip centerline. Intense turbulence generation due to the increase in velocity resulted in wide spray angle. On the other hand, spray tip penetration for 14H70 injector was smaller than that for 8H70 injector. Competition between increase in velocity and decrease in nozzle diameter bring about spray tip penetration for 14H70 injector, i.e., increase in momentum, which previously showed for 8H70 injector, contributed to the increase in spray tip penetration, but decrease in nozzle diameter could result in the decrease in the spray tip penetration. Spray angle for 14H70 injector was similar to that for 8H146 injector. Moreover, injection rate measurement reveals that slope for narrow injection angle (70°) was steeper than that for wide injection angle during injection event. Based on the experimental results, assessment of spray tip penetration model was carried to investigate the effect of injector configuration under low ambient gas density condition. Because previous model of spray tip penetration has no information on the injection angle, developed formula in this paper can apply the spray evolution from injector with same nozzle diameter and different injection angle. The formula showed good agreement with experimental results except initial stage of spray evolution.
The swirl spray for direct injection gasoline engines was controlled using the tapered nozzles to fulfill the requirement of various combustion systems and the control mechanism causing the spray alterations were investigated. This study focused on how the correlation between taper angle, inclined angle of tapered nozzle, and flow angle affects the swirl spray shape. The macroscopic spray images were captured and velocity and droplet size distribution of tapered nozzle swirl spray were measured to understand the spray alterations at different taper angles. The result showed that fuel did not pass some area of nozzle exit and U or V shape spray was generated when the taper angle was higher than 90o minus flow angle. The velocity and fuel distribution of swirl spray were more asymmetrical and the spray robustness was enhanced when the taper angle was increased. The opened swirl spray, U or V shape spray generated when the taper angle is more than 90o minus flow angle, showed the possibility for the application of spray-guided combustion system as a result of enhanced spray momentum and reduced static air pressure drop inside the spray compared with the conventional swirl spray.
Hydrotreated biodiesel (HBD) would be one of the promising alternative fuels instead of current biodiesel. In this study, Investigation of spray characteristics in terms of spray penetration and spray angle were conducted experimentally including calculated SMDs as well. The ambient pressures of 1, 3, and 5 MPa and injection pressures of 30, 80, and 130 MPa were introduced and the fuels employed were petro-diesel, and 2, 10, 20, 30, and 50 % for hydrotreated biodiesel, respectively. 6 holes of Bosch injector was used for this study with 156 degree of injection angle and 0.120 mm of nozzle diameter. In this study, spray tip penetrations were measured and analyzed between 0.0 ms and 3.0 ms after start of injection. Pictures were taken at every 0.1 ms of time frames. It was difficult to measure spray angles because of low resolution. Thus, spray angles were measured after 0.2 ms of injection. Test result shows that the distinct differences in penetration length among fuels were shown regardless of ambient pressure in the low injection pressure like 30 MPa. At the same injection pressure such as 130 MPa, the spray penetration length at ambient pressure of 1Mpa shows three times higher than that of 5Mpa. Spray tip penetrations were mostly affected by the injection pressure and ambient pressure. Thus, there were little significant differences of spray tip penetrations among test fuels at the same conditions. Nevertheless, the more HBD blended diesel shows relatively shorter penetration length because of lower density than that of petro-diesel. On the contrary, the more biodiesel blended fuel shows the longer penetration length because of higher density than that of petro-diesel. Relatively larger spray angles were observed to the more HBD blended diesel than petro-diesel at the same time frame after injection. The more biodiesel blended diesel shows smaller spray angle as opposed to HBD, because of the difference of their density, kinetic viscosity and surface tension. Spray angle increases appreciably with increase in nozzle diameter, and diminishes with increase in ambient density, liquid viscosity, and injection pressure of liquid. Spray angle decreases with increase in viscosity. Surface tension had no appreciable effect on spray angle. Spray angle widens slightly with increase in density. SMD correlations among surface tensions, densities and viscosities of petro-diesel and HBD blended diesels were calculated by means of two typical numerical equations, which is the regression model developed from the experimental data acquired using Malvern Particle Size Analyzer. The results on SMD can be seen that viscosity has more positive effects than density. Therefore, the more HBD blended fuels were shown the slightly larger SMDs than petro-diesel, because of larger viscosity of HBD than that of petro-diesel. Consequently, this study has found that HBD has a little bit merits and demerits of macro- and microspray patterns compared to petro-diesel.
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.
Optimum engine performance is obtained when the spray characteristics is well matched to the geometry of a combustion chamber. Among many parameters governing the combustion performance in internal combustion engine, fuel supply characteristics and atomization are important performance factors. Therefore, spray characteristics of high pressure multi-hole injector has been studied experimentally. An experimental test system has been made to operate high pressure injection system and to visualize spray behavior. Spray visualization has been performed to analyze spray formation, spray cone angle, bent angle and penetration length. Spray interaction with piston has been analyzed with various injector installation angle, injection pressure and ambient pressure. Test results show that penetration length is greatly influenced by the injection pressure. Penetration length is decreased as ambient pressure increased. Spray cone angle is increased as injection pressure and ambient pressure increased. However, bent angle is not influenced by the change of injection pressure and ambient pressure. Spray cone angle distribution map is plotted using the experimental data. Fuel movement around the spark-plug has been enforced as increasing injector installation angle.
Spray angle is one of the key spray macro parameters which reflect fuel atomization characteristics and fuel and air entrainment quality directly; it then could affect the combustion efficiency and emission formation in cylinder. As the spray characteristics are widely investigated, there are already some kinds of definition and calculation methods for spray angle. Although all these definitions reflect the spray angle trends correspondingly, the difference between these definitions and calculation results was seldom studied. This paper focuses on the comparison and analysis the spray angle results based on the different calculation criterions, and the trend of these key points versus time at various calculation criterions which determine spray angle.
DISI injectors are important for evaluating the spray uniformity of individual spray plumes in order to achieve spray control and fuel distribution. To measure the spray uniformity of individual spray plumes, it is essential to obtain data on the main spray characteristics of individual spray plumes. The narrow spray angle of the DISI injector makes it difficult to measure individual spray plumes; therefore, a new method using cross-sectional images is proposed. Using sheet beams and cross-sectional images of sprays, hole-to-hole spray uniformity can be analyzed via a repeatability evaluation of the acquired data. The proposed method was verified by applying it to two injectors with different hole arrangements and operating pressure ranges. A comparison of spray uniformity between the injectors was conducted. As a result, spray uniformity was investigated in terms of the correlations among individual spray center, spray area, and spray cone angle.
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.
The spray characteristics of swirl spray at different taper angles are investigated and then a taper angle, generating an opened hollow cone spray, is chosen to create the robust swirl spray at various surrounding conditions. The tapered nozzle altered the symmetrical distribution of fuel and velocity to asymmetrical state. The larger portion of fuel was positioned in some area with higher injection velocity, and the smaller portion of fuel was located in another area with lower injection velocity. When the taper angle was decreased, the fuel velocity to a certain direction was getting increased and spray images showed more asymmetrical shape. By cutting the nozzle to have a tapered nozzle with an angle less than the flow angle, opened hollow cone spray was formed because some part of fuel impinges to the cut area. This shape assists in equalizing the pressure difference between the centerline and outer part of spray envelop. The results showed that there is a potential from a tapered nozzle spray to be independent of the various surrounding conditions without much sacrifice of the atomization quality when the taper angle is less than the flow angle.
To investigate the measurement methods of swirl spray angles, back-lit spray photographs were taken using a high-speed camera during cold-flow tests. Since the spray was turbulent and the instantaneous spray shape was time-dependent, the spray angles were measured and averaged from twenty photographs. In the present study, two methods were studied to measure the spray angle. The first is to utilize the linear regression method from the locations of spray surface and the second is to average sequentially the spray angles from each spray surface point. The two methods showed a difference in the spray angle for each photograph. However, the spray angles averaged from twenty photographs using two methods were almost same.