• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.179-188
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• 2003

The spray characteristics of dual orifice injector were investigated under two different fuels through measurement of SMD, number density and volume flux by using PDPA system. In this experiment, we found out that the droplet size and spray structure are strongly depend on fuel density and viscosity.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.10
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• pp.868-874
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• 2015

Thrust variation is an essential parameter in a space mission such as landing on an atmosphereless planet or docking a spacecraft. In order to achieve the thrust variation control, using throttleable injector is a representative and general method. A dual-manifold injector, one of throttleable injectors, was used to control mass flow rate. Five kinds of injectors were designed and investigated in order to compare the spray characteristics of the dual-manifold injector with various tangential entries. Spray angles and patterns were measured to determine external flow characteristics and film thicknesses were measured in order to investigate the internal flow patterns.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.635-644
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• 1994

This study investigated mainly on the flow characteristics of a droplet in the cross region of twin spray. The velocities of the droplet were measured along the axial and radial direction, and the flow characteristics of the droplet were statistically analyzed. For the statistical analysis, the probability density of the turbulent components has been studied, and then the Reynolds shear stress, the skewness and the flatness factors were calculated, and compared with the Gaussian value. Two pressure swirl stomizers were used for the twin spray system and kerosene was employed as the working liquid. 2-D PDA(particle dynamic analyzer) was used for the purpose of the measurement of droplet size and velocities. As a result, it was found that (1) the droplets collision was taken place strongly in the cross region. So, a large momentum loss of droplets due to the loss of natural movement direction was occurred, and momentum loss of radial direction was greater than that of axial direction. (2) The axial direction skewness factor approached to zero like the Gaussian distribution in the cross region of twin spray. (3) In the cross region of twin spray, the fluctuation instability of droplet was increased because of the development of the turbulence characteristics due to the droplet collision.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.126-133
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• 2008

The atomization characteristics of the dual air supplying two-fluid nozzle were investigated experimentally using PIV and PDA systems. The twin-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air, and the main nozzle to produce sprays. The main nozzle has the swirler with four equally spaced tangential slots, which gives the injecting fluid an angular momentum. The swirl angle in the swirler varied with $0^{\circ}$, $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$. The ratios of carrier air to assist air and ALR (total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the AMD and SMD distributions of the sprays were measured using PDA system. As a result, the SMD distribution increases along the radial distance, and it decreases with the increase of swirl angle in swirler.

• Journal of ILASS-Korea
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• v.24 no.4
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• pp.163-170
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• 2019

In this study, feedback logic using dual O₂ sensor values were developed to increase the purification capability of a three-way catalyst (TWC) in a compressed natural gas (CNG) engine. A heavy-duty inline 6-cylinder engine was used and the CNG was supplied to the engine through a mixer. This study consists of two main parts, namely, the proportional integral (PI) control with a front O₂ sensor and the feedback control with dual O₂ sensors. In the PI control experiment, effects of various parameters, such as P gain, I gain, and lean delay, on the TWC capability were identified. Based on the results of the PI control experiment, the feedback logic using dual O₂ sensor values were developed. In both cases, the nitrogen oxides (NO_X) emissions were nearly zero. However, the carbon monoxide (CO) emissions were reduced significant in the feedback logic with dual O₂ sensors than in the PI control with the front O₂ sensor.

• Journal of the Korean Society of Visualization
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• v.8 no.4
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• pp.60-65
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• 2010

A focus is given to the breakup behavior of spray droplets issuing from a nonimpinging-type injector. The analysis has been carried out experimentally by means of the dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters in terms of axial velocity, mean diameter, velocity fluctuation, and span (width of the size distribution) of droplets are measured down the geometric axis of a nozzle orifice and on the plane normal to the spray stream with the injection pressure variations. As the injection pressure increases, the velocity and its fluctuation become higher, whereas the droplet sizes get smaller. It is also shown that the magnitudes of those parameters are smoothed out by dispersion when the droplets move downstream as well as outwardly. The atomization process is significantly influenced by the injection pressure rather than the traveling distance in the experimental condition presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1459-1466
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• 2004

The purpose of this study is to investigate the effect of swirler angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single and twin spray. The characteristics of sprays have been investigated by measuring the spray angle, droplet size and velocity. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber, but for the twin spray, the axial velocity and SMD were not influenced significantly by the changing the aspect ratio of swirl chamber. The effect of swirler angle on the spray characteristics was greater than the aspect ratio of swirl chamber for single spray. The nozzle pitch was one of the important factors affecting the spray characteristics of twin spray.

• Fire Science and Engineering
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• v.29 no.5
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• pp.29-33
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• 2015

In this study, the relations of flow rate, discharging distance and droplet size are measured in accordance with the nozzle shape. The dual type nozzles of LPN142 and LPN148, which have identical core diameter (6.0 mm) and the different radial injection angles (${\theta}_2=142^{\circ}$ and $148^{\circ}$), are manufactured. The distribution diameters with discharging distance are quantified by UL2167 test standard. The relations between discharging angle and droplet sizes, which are measured by the method of Helium-Neon laser equipment, are obtained by the empirical correlation as working pressure increase. Moreover, the extinction coefficient, which is major parameter of the radiative transport equation (RTE) is analyzed with variable droplet sizes. Thus, it is possible to opt the nozzle's shape by analyzing the relations of working pressure, spray distance, droplet size and fire characteristics at minimum allowable flow rate.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.9-14
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• 1999

The effect of operating condition was studied experimently on the characteristics of twin sprays ejected from two airblast atomizers, within the range of the mass air-fuel ratio 1.36∼3.54. Water and nitrogen gas were used as test fluids for the experiments. Spray characteristics of liquid spray were measured with measurement of mass distribution and instantaneous image of the spray cone. Experimental results show that the maximum specify of the distribution were lowered but distributed over the larger area when the ROA ratio increased, Center of mass position did not change with increasing water mass flow, Increase of the nozzle distance has an small effect on mass distribution of interaction area but distributed over the larger area. It was also conformed that the effect of interaction near central point of collision decreased with the increase of the ROA ratio on interaction area from comparison using superposition method